diabetic retinopathy clinical research network visual acuity

Diabetic Retinopathy Clinical Research Network

Visual Acuity - Refraction Testing Procedures Manual

Version 1.3

March 18, 2005

DRCRnet Visual Acuity-Refraction Testing Manual 10-27-05.doc

Table of Contents 1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Refraction Protocol 1-1Introduction 1-1

Refraction Chart 1-1Trial Frames/Phoropter 1-1 Contact Lens Use 1-1Refractionists 1-1

Steps in Refraction 1-1 Determine Initial Starting Refraction 1-2 Refine Sphere 1-3 Increase Plus 1-3 Increase Minus 1-3 Refine Cylinder Axis 1-4 Refine Cylinder Power 1-5Checking Cylinder When Beginning Refraction is a Sphere 1-6 Refraction Recheck/Final Sphere Refinement 1-6 Refraction for Patients with Poor Visual Acuity 1-6

Flow Chart of DRCRnet Refraction Protocol 1-7 Visual Acuity Testing 2-1 Electronic Visual Acuity Tester 2-1

EVA System Description 2-1System Calibration 2-2

Size Calibration 2-2Luminance Calibration 2-2

Adjusting the Monitor Settings 2-3 E-ETDRS Testing Protocol 2-3 Overview of E-ETDRS Visual Acuity Testing Protocol 2-3

Electronic ETDRS (E-ETDRS) Visual Acuity Testing Protocol Overview 2-4 Electronic ETDRS (E-ETDRS) Visual Acuity Testing Protocol Algorithm 2-5 Testing Procedures Using the EVA 2-6 Visual Acuity Testing Procedures 2-6 Safeguards to Avoid Bias 2-7 Poor Vision Testing (Testing Light Perception) 2-7 Standard ETDRS Visual Acuity Protocol 3-1 Visual Acuity Chart: Modified Bailey-Lovie 3-1 Illumination of Visual Acuity Charts and Room 3-1 Best-Corrected Visual Acuity Measurement 3-1 Poor Vision Testing 3-2Calculating the Visual Acuity Score 3-2 Certification for Refraction and Visual Acuity 4-1 General Considerations 4-1

Minimum and Maximum Number of Certified Staff 4-1 Certification Numbers 4-1 Equipment Certification 4-1

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Table of Contents 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79

Electronic Visual Acuity Tester (EVA) 4-1 ETDRS Charts 4-1 Trial Frames and Complete Lens Set 4-1 Refraction Certification 4-2 Procedures for Initial Refraction Certification 4-2 Refraction Pre-Certification Training 4-2 Submitting Certification Request 4-2

Refraction Phone Certification Procedures 4-3 Initial Phone Call 4-3 Certification Phone Call 4-3 Recording of Results 4-3 Maintaining Active Certification 4-3 Recertification 4-4 Certification for Visual Acuity Testing Using the EVA 4-4 Procedures for Initial VA Certification 4-4 Maintaining Active Certification 4-4 Non-study Refraction & Visual Acuity Tests 4-4 Visual Acuity/Refraction Certification Guidelines 4-5 Visual Acuity 4-5 Refraction 4-5

Appendix A: E-ETDRS Letter Score – log MAR Snellen Conversions Appendix B: ETDRS Chart R Appendix C: DRCRnet - EVA Refraction Testing FormAppendix D: DRCRnet Visual Acuity Testing Certification Form

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CHAPTER 1 80 81 82 83 84

REFRACTION PROTOCOL A. Introduction ALL refractionists should be proficient in the following optical fundamentals: 85

86 87 88 89 90 91 92 93 94

95 96 97 98

99 100 101 102 103 104 105 106

107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122

• Spherical equivalency • Plus/minus spheres and cylinders • Hyperopia, myopia and astigmatism • "Push plus" refraction principles.

1. Refraction Chart Use of the refraction chart on the Electronic Visual Acuity Tester (EVA) at a distance of 3 meters is preferred; however, either ETDRS chart R at 4 meters/1 meter or office charts at 10 - 20 foot optical equivalent can be used if the EVA is not working.

• For the EVA, the refraction chart on the EVA is displayed by tapping on the [Refraction Chart] icon on the Main Menu of the Palm Handheld or tapping the dropdown in upper right corner of screen and selecting ‘Refraction Chart’; select [Refraction Chart] icon

• If the refraction is performed at a test distance of <3 meters (discouraged), then the spherical component of the refraction needs to be rechecked using the EVA at 3 meters prior to commencing with visual acuity testing.

2. Trial Frames/Phoropter

• Trial frames are preferred for use in refraction. If trial frames/lenses are not used, a phoropter may be used. If a phoropter is used, the final refraction MUST be put in trial frames and the final spherical refinement performed at 3 meters.

• If a phoropter is used for a patient whose acuity is worse than 20/80, the +/-0.25 D or +/-0.50 D strength of the phoropter’s mounted cross cylinder may not allow the patient to notice any change when checking for cylindrical axis and power. In this case, a separate +/-1.00 D handheld cross cylinder (as in the Protocol summary at the end of this chapter) held in front of the phoropter instead of the mounted cross cylinder is recommended.

The method to follow for the subjective refraction is described in terms of a trial frame, but a similar method can be followed with a phoropter. The trial frame is placed and adjusted on the patient’s face so that the lens cells are parallel to the anterior plane of the orbits and centered in front of the pupils. The left eye is occluded and the starting refraction is placed in the right lens cells, with the cylindrical correction anterior. The steps for the procedure are detailed below.

DRCRnet Visual Acuity-Refraction Testing Manual 10-27-05.doc 1-1

3. Contact Lens Use 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144

If the patient wears contact lenses and has spectacle glasses as well, he/she should be instructed to refrain from wearing the contact lenses on the day of each examination. In the event that the patient either has no glasses or has forgotten the instructions and has reported for the examination wearing contact lenses, these should be removed and at least one-half hour should elapse before the refraction is performed. In this latter event, careful attention should be given to the cornea during the slit-lamp examination and any abnormalities should be noted in the patient's clinic record. 4. Refractionists Any individual at the site may be certified for refraction, including investigators, coordinators, technicians, and fellows. The staff performing the refraction is not required to be masked to treatment group (in protocols that include masking), although masking is preferred. B. Steps in Refraction 1. Determine initial starting refraction 2. Refine sphere for the right eye 3. Refine cylinder axis for the right eye 4. Refine cylinder power for the right eye 5. Recheck sphere for the right eye 6. Repeat the process for the left eye 1. Determine Initial Starting Refraction

145 146 147

If patient has had a study refraction at a prior visit, use the refraction results from the most recent visit.

148 149 150 151

152 153 154 155 156 157 158 159 160 161 162 163 164

If this is the first study refraction for the patient, use one of the following for the starting refraction:

• Retinoscopy

• Autorefractor • Current spectacles • Previous refraction (available in patient chart)

In the exceptional case that none of the above is available, then start the refraction with ‘plano’. The refraction steps below are for visual acuities of 20/20 to 20/80 with the initial starting refraction. For acuities worse than 20/80, refer to the charts for appropriate sphere and cylinder powers to use. Whenever the acuity improves to a better range by improved correction (e.g. from 20/80 – 20/160 range to 20/20 – 20/80 range) smaller sphere and cylinder powers for the better acuity range according to the charts should be used.


2. Refine Sphere 165 166 a. Increase Plus

Sphere for Checking Sphere Incremental Change 20/20-20/80 +0.50 +0.50 <20/80 – 20/160 +1.00 +1.00 20/200 – 20/320 +2.00 +1.00 <20/320 +2.00 +1.00

167 168 169 170 171 172 173 174 175

176 177 178 179

180 181

182 183 184 185 186 187

The right eye is tested first and then the left eye. The starting refraction is placed in the trial frame and the patient is asked to read the lowest line possible. With the patient focused on the smallest letters that he/she can read, a +0.50 D sphere is held in front of the trial frame over the right eye and the patient is asked if the lens makes the vision clearer, blurrier, or keeps the vision exactly the same.

• If vision is clearer or there is no change, the sphere in the trial frame is replaced with a sphere that is 0.50 D more plus or less minus.

• The +0.50 D sphere is again held in front of the trial frame over the right eye and the patient is asked again if the lens makes the vision clearer, blurrier, or keeps the vision exactly the same. o If vision is again clearer or there is no change, the sphere in the trial frame is replaced with

a sphere that is 0.50 D more plus or less minus.

• This process of increasing the plus sphere or decreasing the minus sphere in the right eye is repeated until the +0.50 D sphere makes the vision blurrier.

• When the +0.50 D sphere makes the vision blurrier, no additional change in the sphere is made at this time.

By this process the highest plus or least minus sphere for best vision is determined. b. Increase Minus

Sphere for Checking Sphere Incremental Change 20/20-20/80 -0.50 (or -0.37) -0.25 <20/80 – 20/160 -1.00 -0.50 20/200 – 20/320 -2.00 -1.00 <20/320 -2.00 -1.00

188 189 190 191 192 193 194 195 196

After determining the highest plus or least minus sphere, the patient is asked to read the smallest line possible (the reading should be at least as good as the initial reading). The -0.50 (or –0.37) D sphere is held in front of the trial frame before the right eye and the patient is asked if the vision is improved so he can actually read more letters.

• If vision is not improved, the +0.50 D sphere is held in front of the trial frame before the right eye once again to see if the patient will accept more plus.


• If the patient reports that the –0.50 (or -0.37) D lens improves vision, the patient is requested to read the smallest line possible while the –0.50 (or –0.37) D lens is held in front of the trial frame.

197 198 199 200 201 202 203 204 205 206

207 208 209 210 211 212

° If there is an actual improvement in acuity and the examiner is convinces that the patient

is able to read additional letters, then the sphere in the trial frame is replaced by a sphere that is 0.25 D less plus or more minus.

Minus spherical power is added in –0.25 D increments in this fashion as long as the patient continues to read more letters.

• If the patient is unable to read any more letters, the sphere is not changed, even if the patient reports that the vision with the extra minus is better.

The final check in the initial sphere evaluation should be the presentation of a +0.50 D sphere to determine if any more plus sphere will be accepted initially. Example: Assume that following the check with plus sphere, the sphere in the trial frame is -0.50. The patient is asked to read the lowest line possible with this correction and reads the 20/20 line perfectly. Then -0.50 (or -0.37) D is added (to make the sphere -1.00) and the patient is again asked to read the chart. If more letters are read (e.g., 20/20

213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241

+2), then the sphere in the trial frame is changed to -0.75.

The process is repeated with a -0.50 (or -0.37) D added over –0.75. If again the patient reports that vision is improved, but he cannot read any additional letters, the sphere should remain at –0.75 and a final sphere check with a +0.50 D lens done. 3. Refine Cylinder Axis For purposes of this discussion, only plus cylinder techniques are presented. Minus cylinders may be used instead of plus cylinders to determine the axis and power of the cylinder. If minus cylinders are used, the procedure described must be revised to reflect this change in sign. If the starting refraction contains a cylinder correction, changes in cylindrical axis are tested by adding a 0.50 D cross cylinder, first with the positive axis 45 degrees to one side of the cylinder axis, and then with the positive axis 45 degrees to the opposite side of the cylinder axis. Instruct the patient to focus on an “O” or “C” one-two lines above the smallest line of letters that he can read. Explain to the patient: I am going to show you two views of this “C” and neither view may be clearer than the view you have right now. I would like to know which of the two views is the clearer of the two, or are both views pretty much about equally blurry. Ask: Is the “C” clearer on view 1 [flip the lens] or view 2, or are both views about equally blurred?

• Since neither position may produce a clear image, the patient is encouraged to select the position of least blur.


242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284

If the patient cannot choose between the two positions of the cross cylinder at the beginning of this test, the axis of the cylinder is moved 5-15 degrees, first in one direction and then in the other, with the cross cylinder being checked in each position to confirm that the original axis was indeed correct.

• If the patient does prefer one position of the cross cylinder to the other, the axis of the cylinder is moved 5-15 degrees toward the positive axis of the cross cylinder when in the position the patient said was better.

When the power of the cylinder is low and/or the patient’s discrimination is poor, larger shifts will produce more clear-cut responses.

The cross cylinder is tried again with the positive axis 45 degrees to one side of the new cylinder axis and then with the positive axis 45 degrees to the opposite side of the new cylinder axis; the patient is asked which position he/she prefers.

• If the patient prefers one position to the other, the axis of the plus cylinder is moved toward the positive axis of the cross cylinder.

Testing for change of axis is repeated until the patient cannot decide that one position of the cross cylinder is better than the other by reporting that both views are about the same. 4. Refine Cylinder Power Change in cylinder power is now tested by adding the 0.25 D cross cylinder, first with the positive axis and then with the negative axis coincident with the cylinder axis. Again, instruct the patient to focus on an “O” or “C” one-two lines above the smallest line of letters that he can read or on the smallest line of letters he can read. Explain to the patient: Once again I am going to show you two views of this “C” and neither view may be clearer than the view you have right now. I would like to know which of the two views is the clearer of the two, or are both views pretty much about equally blurry. Ask: Is the “C” clearer on view 1 [flip the lens] or view 2, or are both views about equally blurred?

• If the patient prefers the positive axis coincident with cylinder axis, the power of the correcting plus cylinder is increased by an additional plus 0.25 D.

• If the patient prefers the negative axis coincident with the cylinder, the power of the

cylinder is reduced by 0.25 D. The process is repeated until the patient cannot choose one of the cross cylinder positions as better than the other (i.e., until both positions are equally bad). Whenever 0.50 D of cylinder is added, 0.25 D of sphere of opposite sign is added as well (the changing of the sphere occurs during the procedure as soon as the cylinder has been changed by 0.50 D rather than making the adjustment following the completion of the refinement).


a. Checking Cylinder When Beginning Refraction is a Sphere 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310

If the beginning refraction is a sphere and does not contain a cylinder, the presence of astigmatism is tested by arbitrarily placing a 0.25 D cylinder at 90 degrees in the trial frame. The refraction is then continued by checking for cylinder power at axis 90 degrees, 180 degrees, 45 degrees, and 135 degrees. If the patient accepts the cylinder in any of these locations, continue the refraction by modifying the cylinder axis and power as described above. 5. Refraction Recheck/Final Sphere Refinement In all situations a final check of the sphere, as described below, must be repeated using the EVA (at a distance of 3 meters) and trial frames. The power of the sphere is rechecked according to the sphere refinement protocol above by using +0.37 D and -0.37 D spheres and changing the spherical power by 0.25 D increments of the appropriate sign until the patient can perceive no improvement in vision. If the sphere is changed at this point by 0.50 D or more, the cylinder axis and power should be rechecked. This process is repeated until no further significant lens changes are made. The entire process is then repeated for the left eye. 6. Refraction for Patients with Poor Visual Acuity For patients with acuity worse than 20/100, the strong preference is to use the EVA at 3 meters since letters can be projected as large as 20/800. If ETDRS chart R is used at 1 meter, then it will be necessary to recheck the sphere using the EVA at 3 meters. In order to make the correction appropriate for the 3 meter visual acuity test distance, a 0.75 D should be subtracted from the sphere determined at 1 meter, and the sphere then rechecked using the EVA.

311 312 313 314 315 316 317 318

If the subjective refraction cannot be performed because the patient's visual acuity is too poor, then the patient's most recent distance subjective refraction obtained at a previous visit should be considered as the refraction. Example: ETDRS chart R is used for refraction which could not be performed at 4 meters in the right eye because the patient could not see any letters on the refraction chart at that distance. When the patient was moved up to 1 meter, the following was obtained: + 2.00 + 1.00 x 180 degrees

319 320 321 322 323 324 325 326

In order to make this finding appropriate for visual acuity testing at 3 meters a 0.75 D sphere must be subtracted from the above resulting in + 1.25 + 1.00 x 180 degrees. This is placed in trial frames and the sphere is rechecked using the EVA at 3 meters. Example: In another patient, the refraction could not be performed at 4 meters and the following refraction was obtained at 1 meter in the left eye: - 1.75 + 0.50 x 90 degrees. The appropriate correction for retesting the sphere using the EVA is - 2.50 + 0.50 x 90 degrees.

327 328 329 330


DRCRnet REFRACTION PROTOCOL SUMMARY 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353

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FLOW CHART OF DRCRnet REFRACTION PROTOCOL

1. SPHERE a. Plus Better Increase plus. (lowest line) No Change Increase plus. Worse STOP

b. Minus Better Increase minus if additional letter(s) read. (lowest line) No Change STOP Worse STOP

c. Plus Better Increase plus. (lowest line) No Change Increase plus. Worse STOP

2. CYLINDER a. Axis Better at Move axis toward preferred plus axis (C or O above 1 or 2 until position 1 and 2 are equal. smallest line)

3. CYLINDER a. Power Better at Increase or decrease plus power (C or O on 1 or 2 until neither position 1 or 2 is better. smallest line) If power changes by >=.50 adjust sphere.

(Not present) JCC at 90/180; Place cylinder at preferred axis. JCC at 45/135 Then, check cylinder axis and power as above.

4. REFINE SPHERE Refine with +/- spheres as in step #1 until no improvement in vision.

Sphere Cylinder Sphere

Refinement Vision with

Best Correction Power

(1) Increment

(1) Axis (2)

Power(3)

Increment(3)

Power (4)

Increment(4)

a. +.50 +.50 a.+.37 +.25b. -.50 -.25 b. -.37 -.25

20/20 – 20/80

c. +.50 +.50

a..50 JCC

a..25 JCC

+.25 -.25

c.+.37 +.25a. +1.00 +1.00 a.+.50 +.50b. -1.00 -0.50 b. -.50 -.50

<20/80 – 20/160

c. +1.00 +1.00

a.1.00JCC

a.1.00JCC

+1.00 -1.00

c.+.50 +.50a. +2.00 +1.00 a.+1.00 +1.00b. -2.00 -1.00 b.-1.00 -1.00

20/200 – 20/320

c. +2.00 +1.00

a.1.00JCC

a.1.00JCC

+1.00 -1.00

c.+1.00 +1.00a. +2.00 +1.00b. -2.00 -1.00

<20/320

c. +2.00 +1.00

No cylinder test No refinement

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CHAPTER 2 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381

VISUAL ACUITY TESTING

It is essential to have standardized visual acuity measurements for each examination at each of the participating clinics to minimize the effects of acuity examiner and patient bias. Visual acuity testing is being performed with the Electronic Visual Acuity Tester (EVA) using a protocol called the Electronic ETDRS (E-ETDRS) Visual Acuity Testing Protocol. This protocol has been developed to provide a visual acuity score that is comparable to that using the manual testing protocol used in the Early Treatment of Diabetic Retinopathy Study (ETDRS). The ETDRS chart testing is used as a back-up in case the EVA is not functioning. Visual acuity measurements for each eye are obtained by a certified visual acuity examiner before the patient's pupils have been dilated. A. Electronic Visual Acuity Tester 1. EVA System Description The EVA (Figure 1) utilizes a programmed Palm handheld device (or tablet PC) that communicates with a personal computer running a Linux (or Windows XP) operating system. Stimuli are high-contrast, black-and-white letters with luminance of 85 to 105 candels/meter2 and contrast of 98%. The system can present single letters or lines of letters. Single letter testing is used in the Electronic ETDRS program whereas lines of letters can be used for refraction. Single letters are framed with crowding bars spaced a letter width around the letter. For lines of letters, five letters are displayed for sizes smaller than 20/160; a decreasing number of letters is displayed as letter size increases. With a high-resolution (1600x1200) 17-inch monitor, the system is capable of displaying letters from 20/800 (1.6 logMAR) to 20/12 (-0.2 logMAR) at a test distance of 3 meters. Letter size is a close, but not exact, approximation of the logMAR progression of the ETDRS charts (within about 2% of the letter size at each logMAR level). See Appendix A.

382 383 384 385 386 387 388 389 390 391 392 393 394

The Palm™ handheld device (Figure 2), which is connected to the EVA by a serial cable, provides instructions for the technician, allows entry of identification data, displays the letter that is being shown on the monitor, records the responses, and sends instructions to the EVA with regard to the sequence of letter presentations. The size of each letter presentation is determined by a computer program based on the subject’s responses. Figure 1: Electronic Visual Acuity Tester (EVA) F gure 2: Palm Handheld

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2. System Calibration 395 396 397 398 399 400 401 402 403

Two system calibrations are performed at regular intervals: (1) size calibration to confirm letters are accurately displayed and (2) luminance calibration to confirm the monitor screen is sufficiently bright for testing. a. Size Calibration For DRCRnet studies, size calibration must be performed at each study visit. For non-DRCRnet study use, size calibration is recommended at least quarterly. Size Calibration Instructions: 1. Display the EVA calibration square (this is the initial screen

when the system starts up). Length of each side of the black square should be 114 mm

2. Repeat the following steps on the top and left side of square:

a) Place DRCR ruler (or similar ruler with millimeter scale) against side of black square. Check whether length of the side is 114 mm.

IMPORTANT: When viewing, use only one eye and move your head as necessary such that your eye is directly on line with side.

b) If needed, adjust side to 114 mm by changing horizontal and/or vertical setting as described in section 3 below.

404

405 406 407 408 409 410 411 412 413 414 415 416 417 418 419

b. Luminance Calibration For DRCRnet studies, luminance calibration must be performed at each study visit.

Luminance Calibration Instructions: 1. Allow monitor to warm up for at least 10 minutes.

2. Display the EVA calibration square (this is the initial screen when the system starts up).

3. With room lights off, hold the light meter upright with the face of the meter (the corrugated transparent “bubble” portion) up to the white part (top half) of the screen. The red meter needle should fall within or above the black colored area on the light meter face.

2-2

3. Adjusting the Monitor Settings 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452

There are four (4) buttons located on the front of the EVA monitor. These buttons are used to adjust monitor settings as follows: ● Press “1” button to start the onscreen menu ● Press the Up or Down arrow button to highlight the

setting needing adjustment (H. Size, V.Size, Brightness/Contrast) ● Press “2” button to select the highlighted setting ● For Brightness/Contrast, press “2” button again to toggle between selections ● Press Up or Down arrow button to increase/decrease setting

● Press “1” button to save and exit ● To end, press “1” button until menu closes.

B. E-ETDRS Testing Protocol The EVA runs a visual acuity testing program called E-ETDRS (which stands for Electronic Early Treatment of Diabetic Retinopathy). The program has been developed to provide a visual acuity letter score that is comparable to the ETDRS chart testing score. As part of the development of the E-ETDRS protocol, a study was conducted in which high validity and test-retest reliability were demonstrated (Moke PS, Turpin AH, Beck RW et al. A computerized method of visual acuity testing: adaptation of the amblyopia treatment study visual acuity testing protocol. Am J Ophthalmol 2001; 132:903-14). 1. Overview of E-ETDRS Visual Acuity Testing Protocol In brief, the E-ETDRS Visual Acuity Testing Protocol consists of an initial screening phase to obtain an approximation of the visual acuity threshold and then a testing phase to obtain the visual acuity score. The protocol is summarized below. The complete algorithm is depicted in the figure that follows.


Electronic ETDRS (E-ETDRS) Visual Acuity Testing Protocol Overview 453

454

455

The E-ETDRS testing protocol:

• Screening phase: With single letter presentations, determines smallest logMAR level at which a letter is correctly identified.

• Testing phase: Starts testing letters by intermixing letter sizes of screening phase score and one level smaller.

• Test progress: If a letter is missed at a level, one level larger is added to the testing mix; if a letter is correct at a level, one level smaller is added to the testing mix. • Acuity determination: Tests 5 letters at each level until smallest level with 5/5 correct and the

smallest level with 0/5 correct are determined.

IN THE FOLLOWING EXAMPLE, C = CORRECT AND M = MISSED

Example: Screening: 20/400c, 20/200c, 20/100c, 20/50c, 20/25m, 20/40m Score = 20/50 Test progress 1. Start by intermixing 20/50 and 20/40 letters: 20/50c, 20/40m, 20/50c, 20/40m, 20/50m 2. Because a 20/50 letter was missed, add 20/63 to the letter mix (so now will have letters of 20/40, 20/50, and

20/63 intermixed): 20/63c, 20/50c, 20/40c 3. Because 20/40 was correct, add 20/32 to the letter mix (mix is now 20/32, 20/40, 20/50, and 20/63): 20/32m,

20/63c, 20/63c, 20/50m 4. Five letters at 20/50 have been tested, so it drops out of the mix (mix is now 20/32, 20/40, and 20/63): 20/63c,

20/40c, 20/32m, 20/40m 5. Five letters at 20/40 have been tested, so it drops out of the mix (mix is now 20/32 and 20/63): 20/32m,

20/32m, 20/63c 6. Five letters at 20/63 have been tested, so it drops out of the mix (mix is now 20/32 only): 20/32m 7. Five letters at 20/32 have been tested; there are no letters left in the mix so test is over Test summary 20/63 5/5 correct 20/50 3/5 correct 20/40 2/5 correct 20/32 0/5 correct Letter Score: 10 (number of letters correctly identified) + 55 (5 times the number of lines above (larger than) 20/63 and through 20/800) = 65 Snellen Notation (smallest line with at least 3 of 5 letters correct): 20/50



456

Electronic ETDRS (E-ETDRS) Visual Acuity Testing Protocol Algorithm Screening Phase

Show 20/400 letter

Show letters in 3-level steps (e.g. 20/200, 20/100, 20/50, 20/25, 20/12) until either a miss or 20/12 correct

Show letter 2 levels up from missed level (i.e. level smaller than last correct level)

Show letter at each successive larger level until

correct response

Screening score is last correct level

Threshold Phase 1. To start, letter pool consists of letters from 2 levels*: level of screening phase score and one level smaller. 2. Each letter presentation is randomly selected from active pool of letters with the stipulation that every third

letter must be from the largest level in active letter pool. 3. A level remains in active pool until 5 letters are tested at the level. 4. A new level is added to active letter pool when:

a. A letter from largest level in the pool is missed: one level larger is added to letter pool† b. A letter from smallest level in the pool is correct: one level smaller is added to letter pool‡

5. Testing continues until an upper logMAR level with 5 of 5 letters correct and a lower logMAR level with 0 of 5 letters correct are determined and 5 letters are tested on all levels in between upper and lower logMAR levels.§ 6. Visual acuity score is the number of letters correctly identified during threshold testing, plus 5 letters for

each logMAR line above the upper logMAR level through 20/800.

Show a 20/800 letter

Correct Incorrect

Incorrect Correct

Show letter at each successivelysmaller level until a miss or

20/12 correct

Incorrect

Screening score is 20/800

The screening phase uses the letters V, R, K and D. The threshold phase uses the same 5 letters from the Sloan letter set thatappear on the original ETDRS charts for right and left eyes. *Unless screening score was 20/12, in which case letter pool consists of only 20/12 level letters. †Unless 20/800 letter is missed. ‡Unless 20/12 is correct. §If 20/12 becomes part of the active letter pool, it will be the lower logMAR level.

In each step, one letter is shown at each logMAR level.

Correct

Letter Missed

Show letter at each successively smaller level until either a miss or 20/400 correct

20/400 Correct

20/12 Correct

Letter missed

Testing Procedures Using the EVA 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486

487 488 489 490 491 492 493 494

495 496 497

498

499

Before each patient study visit:

● Calibrate monitor for letter size

● Check monitor luminance

• Check room lighting level (dim incandescent lighting is recommended; fluorescent lighting should not be used; no glare on screen; no spotlights)

Before Every Test

● Verify testing distance from EVA to center of exam chair is 3 meters (118 inches)

● Turn on Palm and remove stylus DRCRnet Patient Testing (must be used for study patients) ● Turn on Palm and remove stylus ● On main menu, tap [DRCRnetPt] icon OR

Tap dropdown in upper right corner of screen, select 'DRCRnet Pt'; select [DRCRnetPt] icon ● Follow instructions on Palm Shut Down System ● Turn off the PC tester by selecting [Shutdown] icon on main menu OR Tap dropdown in upper right corner of screen, select ‘DRCRnetPt’; select [Shutdown] icon

2. Visual Acuity Testing Procedures a. Trial frames are to be used for refractive correction. In addition to the occluder in the trial

frame, for testing the right eye, left eye is occluded with an eye patch or pad placed beneath the trial frames and vice versa. • The study protocol will specify when a refraction must be done. If a refraction is required at

a visit, then the correction determined in the refraction will be used for the visual acuity testing. If a refraction is not required at a visit, then the correction determined in the most recent refraction will be used.

• In some protocols, a refraction may only be required if visual acuity has changed by 10 or more letters since the last visit. In such cases, visual acuity testing will be repeated after the refraction and when the refraction is found to have changed.

b. If the protocol specifies that both eyes are to be tested, the right eye is always tested first.

c. Visual acuity testing is to be done without cycloplegia and without pupil dilation.


3. Safeguards to Avoid Bias 500 501 502 503 504 505 506 507

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Masking of visual acuity testing will be achieved when feasible at a site, but is not a requirement. Due to the automated nature of the computerized EVA testing, the potential for induction of bias on the part of the technician is minimized. Technician instructions to the patient are to be minimal. a. The patient should be told that there are only letters and no numbers and that each letter is

“bracketed” by lines on all four sides.

b. For patients with poor central vision, it may be suggested that the patient fixate eccentrically or turn or move his/her head in any manner if this improves visual acuity. If the patient employs these maneuvers, care must be taken to ensure that the fellow eye remains covered.

c. When the patient cannot read a letter, he/she is told to guess. If the patient states that a letter is one of two letters, then he/she is asked to choose only one letter and, if necessary, to guess.

d. When the patient gives one response but then gives a second response before the first response has been finalized (i.e., before the technician has verified the response as correct or incorrect and before the letter presentation on the EVA screen changes), the patient should be asked if that is his/her final answer; if the patient equivocates, ask the patient to choose one letter. Once the technician has verified the response and the letter presentation has changed on the EVA, no changes can be made in the patient’s response.

D. Poor Vision Testing (Testing Light Perception) If the patient cannot identify any letters on visual acuity testing of an eye (i.e., letter score = 0), the eye is tested for light perception with the indirect ophthalmoscope as the light source. The testing procedure can be performed according to the investigator’s usual routine. The following procedure is suggested:

• Room lighting should remain at the level of normal visual acuity testing. The patient should close the opposite eye and occlude it by making a tight seal with the palm around the orbit and the bridge of the nose. The indirect ophthalmoscope light should be in focus at three feet, and the rheostat set at six volts. From a distance of three feet the beam should be directed in and out of the eye at least four times; the patient should be asked to respond when he/she sees the light. If the examiner is convinced that the patient perceives the light, vision should be recorded as light perception, otherwise as no light perception.


CHAPTER 3 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577

STANDARD ETDRS VISUAL ACUITY PROTOCOL The Standard ETDRS Visual Acuity Protocol should only be used as a back-up in the event the Electronic Visual Acuity Tester (EVA) is not functioning. A. Visual Acuity Chart: Modified Bailey-Lovie The ETDRS visual acuity charts 1 and 2 will be employed for standardized measurement of visual acuity. Acuity testing of all patients, regardless of visual acuity, begins at four meters. Two ETDRS Visual Acuity Charts are used for the measurement of visual acuity, each with a different letter sequence. The right eye will always be tested with Chart 1 and the left eye with Chart 2. B. Illumination of Visual Acuity Charts and Room Each clinic must have/use an ETDRS light box for the ETDRS visual acuity charts during any DRCR.net protocol acuity testing. The light box should be hung at eye level on the wall or placed on a stand (that can be purchased from the Lighthouse for the Blind in New York). Room lighting should be at office levels (about 50 foot candles) and should be uniform between the patient and the light box. The distance from the patient’s eyes to the Visual Acuity Chart should be 4.0 meters. C. Best-Corrected Visual Acuity Measurements The right eye is tested first and then the left eye. The patient is seated such that the distance from the patient's eyes to the ETDRS Visual Acuity Chart should be 4.0 meters. This testing distance is always used first even if the patient could not be refracted at four meters. In addition to the occluder in the trial frame, the left eye is occluded with an eye patch or pad placed beneath the trial frames. With the lens correction obtained by subjective refraction in the trial frame, the patient is asked to read ETDRS Visual Acuity Chart 1 from the top with the right eye. It is emphasized to the patient that each answer will be scored so that adequate time should be allowed for each letter in order to achieve the best identification. The patient is instructed that all of the figures to be read are letters and that there are no numbers. The examiner records each letter identified correctly by the patient as he/she reads the chart by circling the corresponding letter on the appropriate DRCR.net form for this visit. Letters read incorrectly, or for which no guesses are made, are not marked on this form. Each letter read correctly is scored as one point. The score for each line (including zero if no letters were read correctly on that line) and the total score for the eye must be recorded on the form after the testing has been completed. If the number of letters read correctly at four meters is less than twenty, the test should be repeated at one meter and both the four-meter and one-meter totals should be recorded on the appropriate DRCR.net form for this visit. Both eyes should be tested at four meters before the patient is moved up to the one-meter test distance. Prior to actual testing at one-meter, + 0.75 sphere should be added to the correction already in the trial frame to compensate for the new distance. The patient must sit for testing at the one-meter distance. The same procedure for obtaining visual acuity for the right eye is used for the left eye, except that ETDRS Visual Acuity Chart 2 is used.


D. Poor Vision Testing 578 579 580 581 582 583

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Follow the procedures described in Chapter 2, Visual Acuity Testing. E. Calculating the Visual Acuity Score After each measurement of visual acuity, the visual acuity score for the visit is calculated. The visual acuity score is defined as follows:

• If twenty or more letters are read correctly at the four-meter test distance, the visual acuity score is equal to the number of letters (N) read correctly at four meters +30.If one or more but less than twenty letters are read correctly at four-meter distance, the visual acuity score is equal to the number of letters read correctly at four meters plus the number of letters read correctly at one meter in the first six lines.

• If no letters are read correctly at either the four-meter distance or the one-meter distance, the visual acuity score is 0.


CHAPTER 4 592 593 594 595 596 597 598 599

CERTIFICATION FOR REFRACTION AND VISUAL ACUITY A. General Considerations 1. Minimum and Maximum Number of Certified Staff Each site must have a minimum of two individuals certified for refraction and for visual acuity testing. For sites with only one office location, the maximum number of individuals to be certified for refraction is 3. For sites with multiple offices

600 , the maximum number of refractionists is 2 per

office location. For medical centers with large diabetic populations, additional individuals may be certified for refraction and visual acuity testing only with Coordinating Center approval.

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Any individual at the site may be certified for refraction, including investigators, coordinators, technicians, and fellows. B. Certification Numbers Each individual to be certified for a procedure must have a DRCR.net identification number. This number will be assigned by the Coordinating Center. If an individual to be certified does not already have a number, complete a DRCR.net Request to Add Additional Site Staff form and fax it to the Coordinating Center.

C. Equipment Certification Sites must complete a Visual Acuity and Refraction Equipment Certification form, for each location where patients are seen, to confirm they have the required equipment for refraction and ETDRS visual acuity. Note: ETDRS equipment will only be used as a back up if the Electronic Visual Acuity Tester (EVA) is not operational. 1. Electronic Visual Acuity Tester (EVA) All sites will receive an EVA for use with the DRCR.net studies. Upon receipt, the EVA Calibration Form is completed (see Chapter 2 for calibration instructions) and sent to the Coordinating Center. 2. ETDRS Charts For back-up purposes, sites should have ETDRS charts to use if the EVA is not operational (and there is only one EVA at the site). 3. Trial Frames and Complete Lens Set For refraction, either trial frames or a phoropter can be used. For visual acuity testing, trial frames are used.


D. Refraction Certification 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649

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1. Procedures for Initial Refraction Certification Several steps are involved for an individual to obtain certification for refraction. Note: Investigators requesting certification must complete the same procedures as technicians. a. Refraction Pre-Certification Training Prior to requesting certification, the individual must have experience performing refractions using the refraction protocol as detailed in Chapter 1. It is strongly encouraged that individuals requesting certification for refraction be experienced refractionists, even if not experienced with the ETDRS or similar protocol. Prior to requesting certification, the following steps must be completed:

1) Read the Refraction Protocol (Chapter 1).

2) Perform a refraction using the protocol on both eyes of at least 10 patients: • At least 3 of the patients should have acuity worse than 20/100 in at least one eye.

• If the individual is not already an experienced refractionist, the refraction results should be supervised by an experienced refractionist for at least 5 of the patients.

• If the individual already has experience performing refractions using this protocol (or a nearly identical one) in other studies, this experience can be counted toward fulfilling the 10 patient requirement.

• Principal investigator must review the individual’s qualifications and verify that the required steps have been completed.

b. Submitting Certification Request The steps involved in the initial certification process include:

1) Complete the necessary pre-certification training

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2) Submit the following documents online (www.drcr.net) under the Clinical Sites, Certification menu:

• DRCR.net Refraction Certification Request Form (A request form is required for each individual requesting certification)

3) Upon submission of form, an email is sent to Examiner and Site Coordinator.

4) The Examiner then contacts the refractionist within 24-48 hrs. via phone or email to schedule a time for an Initial Phone Call.

Note: Upon submission, all pending requests will show on pending VA certification report


http://www.drcr.net/

2. Refraction Phone Certification Procedures 673 674 675 676 677 678 679 680 681 682 683 684

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a. Initial Phone Call During this phone call, the Examiner (1) will confirm that the candidate has completed all of the steps necessary prior to certification testing and (2) will ask the candidate questions about the procedure to ascertain that the candidate is prepared for the formal testing. Assuming that the candidate and the Examiner agree to proceed, an appointment will be scheduled for the formal certification procedure.

b. Certification Phone Call For the formal certification teleconference, the candidate will need to be in an exam room with the following items:

• A speaker phone is preferred for “hands-free” work.

• If a phoropter will be used, one should be present.

• If the refraction will be done manually using a trial frame (preferred), then trial frames, proper Jackson cross cylinders, and a complete lens set is necessary.

• EVEN IF A PHOROPTER WILL BE USED THE CANDIDATE MUST HAVE TRIAL FRAMES AND A COMPLETE LENS SET AVAILABLE TO DEMONSTRATE THE ABILITY TO PROPERLY PLACE THE OBTAINED RERACTION IN THE TRIAL FRAMES.

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• A copy of the DRCR.net EVA Refraction Testing form (Appendix C). Alternatively, the ETDRS Chart R (Appendix B) can be used, however, the EVA Refraction Testing form must still be available for recording refraction.

During the phone certification, the Examiner will act as a patient. The Examiner will provide a starting refraction that the candidate will place in trial frames/phoropter and then the refraction will proceed just as if the Examiner was sitting in the chair in front of the candidate. The refraction must be properly put in the trial frames if a phoropter is used. c. Recording of Results Upon completion of the certification testing, the examiner determines if the candidate is certified.

• The Examiner then accesses the DRCR.net website and records the results.

• Refractionist and site coordinator are notified of results via auto email.

3. Maintaining Active Certification In order to maintain active certification, a refraction exam must be done on a study patient at least once during the time intervals specified below under any DRCR.net protocol:

• Refraction: once every 4 months


• If a refraction is not performed within this 4-month period, then the certification status will be changed to inactive. Individuals with inactive status will need to undergo the full certification procedure for active status to be restored.

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In addition, a formal recertification process must be completed once every 12 months to maintain active refraction certification as indicated below. 4. Recertification Refraction certification must be renewed once every 12 months, with the same phone certification process described above for the initial certification. To re-certify each refractionist will need to submit the DRCR.net Refraction Re-Certification Request Form, online (www.drcr.net) under the Clinical Sites, Certification menu.

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Upon completion of the refraction recertification test online, the refractionist will be contacted to schedule a recertification teleconference. The certification status will be renewed once the recertification call has been completed. D. Certification for Visual Acuity Testing Using the EVA 1. Procedures for Initial VA Certification The following steps should be completed:

a. Read this DRCRnet Visual Acuity – Refraction Testing Procedures Manual regarding:

• Electronic Visual Acuity Tester and its calibration

• E-ETDRS Testing Protocol

• Standard ETDRS Visual Acuity Protocol

b. Check the calibration of the EVA

c. Perform visual acuity testing using the E-ETDRS testing protocol separately on each eye of one individual

d. Complete the DRCR.net Visual Acuity Testing Certification form online (Appendix D). 2. Maintaining Active Certification In order to maintain active certification, a visual acuity test (masked or unmasked) must be performed at least once every six months on the EVA. If an individual's refraction or ETDRS certification expires, the online certification test must be retaken. E. Non-study Refraction & Visual Acuity Tests In order to maintain active certification, visual acuity technicians and refractionists can perform an exam on a non- study patient (this may include any office personnel). The results of the non-study exams should be recorded online (www.drcr.net) under the Clinical Sites, Certification menu. 752

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F. Visual Acuity/Refraction Certification Guidelines 754 1. Visual Acuity 755

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The duration of visual acuity certification is 6 months. Certification is renewed with each test completed on the EVA Tester for the DRCRnet or SCORE studies. The DRCRnet and SCORE correspond on a weekly basis to update tests completed by DRCR personnel in order to maintain accurate expiration dates for certification. Emails are sent on a weekly basis from the DRCRnet to the clinical sites detailing which DRCR personnel will expire within the next 30 days or have already expired. In an effort to help VA testers maintain their certification status, an application has been added to the EVA Tester to allow for non-study patient VA testing. To complete a non-study patient VA test, select the ‘Non-Study Patient’ icon on the EVA Palm Pilot. Once the VA exam is complete, record the results online under the Clinical Sites – Certification – Refraction and Visual Acuity Non-Study Tests menu. Note: Office personnel may be used to complete a non-study patient VA exam. Should a lapse in certification occur (i.e. a VA test not performed within 6 months), the VA technician will become inactive and will need to complete the EVA Visual Testing Certification Form located on the DRCRnet website under the Clinical Sites – Certification menu. If the VA tester passes the online certification test, their status will be returned to active. Should the VA tester fail the online certification test, a teleconference with Greg Anderson will need to be completed before their active status can be reinstated. Greg Anderson will contact the VA tester to schedule a teleconference when required. 2. Refraction 779

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The duration of refraction certification is 4 months. Certification is renewed with each refraction completed by the Refractionist for the DRCRnet studies. Emails are sent on a weekly basis from the DRCRnet to the clinical sites detailing which DRCR personnel certification will expire within the next 30 days or have already expired. In an effort to help Refractionist maintain their certification status, an application has been added to the EVA Tester to allow for non-study patient refractions. To complete a non-study patient refraction, select the ‘Non-Study Patient’ icon on the EVA Palm Pilot. Once the refraction is complete, record the results online under the Clinical Sites – Certification – Refraction and Visual Acuity Non-Study Tests menu. Note: Office personnel may be used to complete a non-study patient refraction. Should a lapse in certification occur (i.e. a refraction not done within 4 months), the Refractionist will become inactive and will need to complete the Annual Refraction Re-certification Request Form located on the DRCRnet website under the Clinical Sites – Certification menu. Once this form is completed, an email will be sent to both the Examiner (Greg Anderson) and the site coordinator. The Examiner will contact the Refractionist to schedule a certification teleconference. Upon completion of the certification teleconference, the Refractionist will be assigned a grade of either passing or failing, which the Examiner will report to the DRCRnet


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Coordinating Center. Once the grade has been entered, an email will be forwarded to both the Refractionist and site coordinator. Note: Annual refraction re-certification MUST be completed regardless of current certification status. To complete an annual re-certification request, complete the Annual Refraction Re-certification Request Form located on the DRCR website under the Clinical Sites – Certification menu. An email reminder will be sent to the site coordinator detailing all Refractionists needing annual refraction recertification.


Appendix A: E-ETDRS Letter Score – log MAR Snellen Conversions 809

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Letters logMAR Snellen Equiv

0-3 1.70 to 1.64 <20/800

4 to 8 1.62 to 1.54 20/800

9 to 13 1.52 to 1.44 20/640

14 to 18 1.42 to 1.34 20/500

19 to 23 1.32 to 1.24 20/400

24 to 28 1.22 to 1.14 20/320

29 to 33 1.12 to 1.04 20/250

34 to 38 1.02 to 0.94 20/200

39 to 43 0.92 to 0.84 20/160

44 to 48 0.82 to 0.74 20/125

49 to 53 0.72 to 0.64 20/100

54 to 58 0.62 to 0.54 20/80

59 to 63 0.52 to 0.44 20/63

64 to 68 0.42 to 0.34 20/50

69 to 73 0.32 to 0.24 20/40

74 to 78 0.22 to 0.14 20/32

79 to 83 0.12 to 0.04 20/25

84 to 88 0.02 to -0.06 20/20

89 to 93 -0.08 to -0.16 20/16

94 to 97 -0.18 to -0.24 20/12


APPENDIX B: ETDRS CHART R 813 814 815

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20/200 H V Z D S

20/160 N C V K D

20/125 C Z S H N

20/100 O N V S R

20/80 K D N R O

20/63 Z K C S V

20/50 D V O H C

20/40 O H V C K

20/32 H Z C K O

20/25 N C K H D

20/20 Z H C S R

20/16 S Z R D N

20/12.5 H C D R O

20/10 R D O S N


APPENDIX C CERTIFICATION WORKSHEET

DRCRNET- EVA REFRACTION TESTING FORM EVA Refraction Chart

20/800 R O K C S

20/640 N D C K H

20/500 V H D O S

20/400 N R Z V Z

20/320 S O V N D

20/250 O D N V Z

20/200 R H R C K

20/160 C S H K H

20/125 D C V O S

20/100 N K Z R C

20/80 S O R Z V

20/63 N K C V H

20/50 S H K N R

20/40 Z D O D C

20/32 R O V H S

20/25 O S H K C

20/20 R N D Z V

20/16 Z D N K O

20/12 K N V Z S

Refraction:

OD ________ ________ @ _______ o

OS ________ ________ @ _______ o

__________________________ Name of Refractionist __________________________ Signature of Refractionist ___ ___ / ___ ___ ___ /___ ___ ___ ___ Date (dd/MMM/yyyy) ___ ___ ___ - ___ ___ ___ DRCR ID#

843


APPENDIX D 844 845 846 A.847

DRCRnet VISUAL ACUITY TESTING CERTIFICATION FORM

TECHNICIAN INFORMATION

Site

Principal Investigator

Date of Form Completion

Name

DRCRnet ID -

B.848 STEPS TO COMPLETE CERTIFICATION:

1. Read the DRCRnet Visual Acuity Testing Procedures Manual regarding: • Electronic Visual Acuity Tester and its calibration • E-ETDRS Testing Protocol • Standard ETDRS Visual Acuity Protocol

2. Check the calibration of the EVA

3. Perform visual acuity testing using the E-ETDRS testing protocol separately on each eye of one individual

4. Complete the DRCRnet Visual Acuity Testing Certification form 849 C.850 CERTIFICATION REQUIREMENTS √ Check each to indicate that it has been completed

I have read the DRCRnet Procedures Manual and understand the EVA set up and visual acuity testing protocol Calibration of EVA completed for brightness and letter size Testing of one individual with E-ETDRS Testing Protocol VA score OD____ VA score OS___

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QUESTIONS TO ANSWER (only one correct answer for each question)

1. What is the testing distance for EVA visual acuity testing?

a. 3 meters from the monitor screen to the front of the chair b. 3 meters from the monitor screen to the back of the chair c. 3 meters from the monitor screen to the middle of the seat of the chair (approximate head

position location of the patient) d. There is no fixed test distance; the test can be done at any distance and the test distance is

recorded on the exam form 2. What must be calibrated/checked prior to performing EVA visual acuity testing?

a. Calibration of the brightness of the monitor b. Size calibration of the monitor c. Both brightness and size calibration of the monitor d. Room illumination

e. Monitor brightness and size calibration as well as room illumination

3. What is “acceptable” room illumination for EVA use?

a. Dim incandescent; no fluorescents; no spotlights b. Fluorescents at no specific level c. Spotlights d. Any lights set at 50 – 75 foot candles


4. The letter set used for EVA testing is the same letters that are used on standard ETDRS charts 871 872 873

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a. True

b. False

5. What is the purpose of the Screening Phase?

a. To familiarize the patient with the test b. To obtain an approximate acuity to start the test

c. To determine if the refraction appears to be correct

6. How is the starting point for the Screening Phase determined?

a. Starting letter size is always 20/800 b. Starting letter size is always 20/400 c. Starting letter size is selected at random by the computer d. Technician must select 20/100 or 20/400 based on expectation of acuity

7. The letter presentations in the Threshold Phase consist of which of the following:

a. Lines of 5 letters b. Lines of 4 letters

c. Single letters d. Single letters at large levels, lines of 3 letters at intermediate levels, and lines of 4 letters

at smaller levels

8. What is the range of acuity levels that can be tested?

a. 20/200 to 20/20 b. 20/400 to 20/20 c. 20/800 to 20/12 d. 20/200 to 20/12

9. How does the testing start in the Threshold Phase?

a. 20/400 letter is presented b. 20/100 letter is presented c. A letter pool is created consisting of letters from 2 levels: level of screening phase

score and one level smaller d. Computer picks a level at random

10. When does the testing end?

a. When the patient reports that he/she cannot identify the letter b. When the patient misses 3 letters consecutively c. When an upper level is determined where patient correctly identifies 5 of 5 letters

and a lower level is determined where patient misses 5 of 5 letters d. When the 20/20 level has been tested


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11. How is the visual acuity score (i.e., the letter score, not the Snellen equivalent) determined?

a. Total number of letters correct in Testing Phase extrapolated to give a score equivalent to the ETDRS chart test

b. Total number of letters correct in Screening Phase plus Testing Phase c. Lowest line with all 3 of 5 letters correct d. Lowest line with all 5 letters correct e. The better of the acuity scores from the Screening Phase and the Threshold Phase

logMAR equivalent of lowest line with 3 of 5 letters correct

12. If a patient responds to a letter presentation that he/she is not sure whether the letter is an ‘O’ or a ‘C’, which of the following is correct?

a. Ask the patient to choose one of the letters (i.e., “O” or “C”). b. Count the response as incorrect and continue the testing c. Count the response as correct and continue the testing

13. If a patient initially responds (incorrectly) that a letter presentation is an ‘O’ but then before you have proceeded to show the next letter says ‘no, I think it is a ‘C’ (correctly), what should you do?

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a. Ask the patient if that is his/her final answer; if the patient equivocates, ask the patient to choose one letter

b. Count the response as incorrect and continue the testing c. Count the response as correct and continue the testing

14. If a patient initially responds (correctly) that a letter presentation is an ‘O’ but then before you have proceeded to show the next letter says ‘no, I think it is a ‘C’ (incorrectly), what should you do?

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a. Ask the patient if that is his/her final answer; if the patient equivocates, ask the patient to choose one letter

b. Count the response as correct and continue the testing

c. Count the response as incorrect and continue the testing

15. If a patient initially responds (incorrectly) that a letter presentation is an ‘O’ but then after 934 935 936 937 938 939 940

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you have proceeded to show the next letter says ‘no, I think the last letter was a ‘C’ (correctly), what should you do?

a. Hit the back button and ask the patient to choose one or the other

b. Continue the testing with the next letter (you have already scored the last letter as incorrect and there is no change to be made)

c. Hit the back button and change the response from incorrect to correct

16. If a patient’s response is that he/she cannot see the letter, what should you do? a. Stop the test

b. Ask the patient to guess

c. Score the letter as incorrect and continue the testing


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17. If a patient’s response is a number rather than a letter, what should you do?

a Count the response as incorrect and continue the test b. Tell the patient that there are only letters and ask the patient to give another response

18. Which of the following is correct?

a ETDRS chart testing can only be performed if the EVA is not functioning

b. ETDRS chart testing can be used interchangeably with the EVA testing If used, ETDRS chart testing must be performed at 4 meters and 1 meter on all patients

19. What is to be done if the patient cannot see any letters on the E-ETDRS test (i.e., letter

score = 0)?

a Repeat refraction

b. Test the eye for light perception

c. Give the patient a rest and repeat the test

20. How is refractive correction provided for testing?

a Testing is done without any correction

b. Trial frames must be used.

c. Trial are used if the refraction is different from the spectacle correction; if the spectacles have the proper correction, then the spectacles can be used

d. Contact lenses can be used instead of trial frames

21. Which eye is tested first?

a Right eye is tested, then the left eye

b Study eye is always tested first (if there is one study eye)

c. Study eye is always tested second (if there is one study eye)


diabetic retinopathy clinical research network visual acuity

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