guidelines for prescribing optical devices and training

GUIDELINES FOR PRESCRIBING OPTICAL DEVICES AND TRAINING23 February 2012

SESSION OUTCOMES At the end of the session, each student

is expected to: Discuss the factors which need to be

considered before choosing an appropriate device

Discuss guidelines and factors to consider before prescribing telescopes

Discuss guidelines and factors to consider before prescribing near magnifiers

Discuss problems which may be encountered with devices

Discuss the training of a prescribed device

SPECIAL CONSIDERATIONS 1. Patient’s level of motivation• The examiner may pick-it up during

examination• Other patients may require

encouragement.2. The size and working distance of the

task3. Hands-free• Does the patient require to have hands free

to hold a book/paper?• Can he/she have the text mounted on a

stand?

4. Ability to hold steadily• Does the patient has ability to hold material

steadily• Will the hand-held device be appropriate for

this patient?5. Ease of handling6. Need for a flat surface• E.g. reading newspapers needs a flat

surface, but reading a can won’t require fixed focus stand magnifier.

7. Acceptable cosmesis• Does the patient like the cosmesis of the

device?• Will the patient mind using the device in

public?8. Training involved• High reading addition?• Is eccentric viewing necessary?9. Environment 10. Close working distance• It is more acceptable to younger or highly

motivated patients.

11. Portability • Does the aid need to be portable?• Or it should not be too bulky12. Integral lighting • Devices which require electricity

cannot be prescribed for a patient who lives in a village where there’s no electricity.

13. Cost • Affordability should be considered.

OTHER FACTORS INCLUDE Age of the patient Preference VA of the patient

DISTANCE OPTICAL DEVICES (TELESCOPES)They provide an increase in the

retinal image size- better resolution

Magnification should be as low as possible

To avoid limitations of fieldTo avoid aberrationThe amount magnification

depends on best VA and target acuity.

SEQUENCE FOR PRESCRIBING TELESCOPES1. Determine the best distance

correction2. Measure the best corrected acuity3. Determine the goal acuity4. Calculate the magnification needed5. Demonstrate the appropriate

telescope to the patient6. Explain the available options7. Loan a device for home trials8. Design the final prescription

PROBLEMS WITH THE USE OF TELESCOPE MAY BE DUE TO THE FOLLOWING: May be improperly focused May be misaligned with the eye May be due to the patient’s poor

localization skills May be causing insufficiency of

brightness May be too close to or too far from the

patient’s eye

TRAINING INCLUDES The use of the device (s) effectively in

terms of: Working distance Posture Handling of the device How to take care of device

Head and eye movement Eye hand coordination

TRAINING WITH THE DISTANCE DEVICES1. Familiarization with focusable devices2. Focusing 3. Locating the object4. Fixating the object5. Spotting the object6. Tracing the object7. Tracking the object

8. Scanning 9. Integration

HAND-HELD TELESCOPES Have px to look at the object without

the telescope, Then move the head down along

straight line to look at their own feet. Then raise the head slowly in the

direction of the object with telescope before the eye.

The back-and-fourth motion along a straight line will bring the image into focus.

The poorer eye may be covered with a patch to allow concentration.

Do not try to walk around while looking through the telescope.

If there’s a problem with lighting or glare, the px must try to reposition him/herself.

Practice for about 5-10 (mins)

SEQUENCE FOR PRESCRIBING HAND-HELD AND STAND MAGNIFIERS1. Determine the best distance correction2. Measure the best corrected acuity

through appropriate add3. Determine the goal acuity4. Calculate the magnification needed5. Demonstrate the appropriate telescope

to the patient6. Loan a device for home trials7. Demonstrate different options in which

it can be prescribed.

OTHER IMPORTANT FACTORS WHICH NEED TO BE TAKEN INTO CONSIDERATION Working distance Field of view Illumination Device manipulation

Working distance Train the patient to position and

maintain the material at the proper distance.

The use of reading stands may have to be considered

Most low vision aids impose working distances to which the px is not accustomed.

HAND-HELD MAGNIFIER Place the aid on the reading material

and slowly and slowly move it towards you until words get blurred, and then push the aid away you get focus.

View from the centre of the magnifier- for good field of view

Adjust the light to properly illuminate material.

Hold material in vertical position. A reading stand or clipboard may help

to keep material flat and steady. Practice for 5 to 10 minutes several

times a day in the beginning. Asthenopia may be experienced

STAND MAGNIFIER Reading portion may be used for

patient who have bifocals. Place the base of the stand flat against

the reading material. The print is automatically in focus

when the stand magnifier rests on the page.

Moving closer to material will allow the px to see a larger area at one time.

View from the centre The px must move the stand magnifier

across the page as he/she reads.

THE IMPORTANCE OF TRAINING AND EDUCATION To ascertain how the patient is

adjusting to the use of the device/s. To establish if the patient has any

problems with the use and care of the device/s

The patient must demonstrate the use of the device/s and comment on the his/her vision with the device/s.

GENERAL GUIDELINES FOR THE TRAINING1. Motivation 2. Explanation 3. Demonstration 4. Practice5. Transfer

Motivation The patient must be well motivated to

perform certain visual skills He/she must understand the purpose of

the skill And how it relates to the desired task.

Explanation How does the device work? At what distance does the device have

to be use.

Demonstration Clearly demonstrate how the device

must be used by the patient. Make sure that the patient

understands and stay motivated by choosing the relevant material.

Practice This is preferably done under the

supervision of the examiner or the. The patient must be given clear

instructions and guided accordingly.

Transfer The skill learned in the clinic setting

must be transferred to the patients home or at work situation.

Practice must therefore takes place in the “real life" setting.

TRAINING SESSION REQUIREMENTS1. Comfortable room2. Good central lighting 3. Additional desk lighting for near work4. Variety of print5. Different charts6. Reading exercises7. Reading stands

Typoscope or bar readers Other necessary devices- Material must resemble the desired

task set by the patient. E.g. if the desired task is to sew, use

sewing material, not reading cards.

FOLLOW-UP VISITS First visit is after a week or two weeks. After three months After six months

SUMMARY SLIDE Case history VA measurements Refraction Magnification/ power calculation Special considerations Device Prescription Training with a device Loan Follow up visits