rules in refractive surgery + cases presentation

Rules and Recommendations in Refractive Surgery

Rules in Refractive SurgeryDr .Hilal Mohamed HilalElnour eye center Damietta Egypt

4 mapAnterior (Axial) sagittal

Corneal thickness map

Anterior elevation map

Posterior elevation map

The most common display is a 4-map

In each map, both

Shape

Should be studied Parameters

1-Anterior sagittal (axial)map

Normal pattern 1- Symmetric bow tie pattern 2-Segments S and I are equal,3- Their axes are aligned..

6


Normal Parameters.At 5mm circle inferior power higher than superior less than 1.5D on the steep axis The superior point may rarely have a higher value than the inferior one; less than 2.50 D.

7

1-Anterior sagittal (axial)mapAbnormal shapes


Angulations more than 30


Asymmetric bow tie More lower steepness

More than 1.5 D


Asymmetric bow tie upper steepness difference more than 2.5D


Asymetric + angle


Smile predisposed to ectasia


Gunctional predisposed to ectasia

1-Anterior sagittal (axial)mapVortex predisposed to ectasia

Important risky point in Anterior sagittal (axial)map

1-K>48D2-Angulation 3-Astigmatism >6D in either surface4-Aginest the rule astigmatism5-Inferior superior asymmetry6-Difference between the inferior and superior more than 1.50 D

-Keratometry readings (k1, k2)--Radii of curvature (Rh, Rv), -Mean keratometry mm zone (Km),

Pachymetry data of the 1-Pupil center,2- apex, 3- thinnest point, and their locations are followed by maximum curvature amount and location.

.

4 mapAnterior (Axial) sagittal

Corneal thickness map

Anterior elevation map

Posterior elevation map

2-3-ANTERIOR AND POSTERIOR ELEVATION MAPShape. The normal shape is the hourglass

Abnormal shapes ------Irregular,

-Tongue-like extensions

-Isolated islands

2-3-ANTERIOR AND POSTERIOR ELEVATION MAPParameters..The highest plus value within the central 5-mm zone;

Normal values are 1.1)

43

Thickness Profilesb. S-shape The red curve has a shape of an S. It isencountered in FFKC and ectatic disorders.

The average is usually high (> 1.1).

Thickness Profilesc. Flat shape The red curve takes a straight course.

It is encountered in diseased thickened (oedematous) corneas such as Fuchs dystrophy and cornea Guttata.

The average is low < 0.8 (red ellipse)

Thickness Profilesd. Inverted The red curve follows an upward course.It is encountered in some cases of PMD.

The average is very low (< 0.8) and may take a minus value

Topometric MapThe most important isvertical inferiorNormal < -0.5 Border line -0.5 and -0.55. Abnormal> -0.55

The most important sectoris the 6 mm or 20 sector

Measure the spherical aberration Q valueMeasurement undertakenAt 6mm diameter at 4 meridian

Sum. Vertical is most important (Normal vertical -0.25 -0.52 Aspheric cornea with least spherical apparition )

Q value (spherical aberration)-2 advanced keratoconus or after hyperopia correction+5-1 moderate keratoconus or after hyperopia correction+2-0.25 -0.52 Vertical normal Aspheric cornea with least spherical apparition0 spherical cornea with spherical apparition +1 after correction of -5 myopia +2 after correction of -12 myopia

6-Topographic astigmatism..

Disparity between these Topographic and manifest astigmatism.1-misalignment during capture,

2-irregular astigmatism,

3-tear film disturbance,

4-corneal haze

5-lenticular astigmatism (including subtle cataract).

Disparity between Topographic astigmatism and manifest astigmatism. If lenticular astigmatism is present without cataract and there disparity,.. avoid overcorrection or converting the orientation of the topographic astigmatism

-/-3x180 corrected as -0.5/-2x180

Disparity between Topographic astigmatism and manifest astigmatism. For example, if the manifest astigmatism is -3.00 X 180 and the topographic astigmatism is -2.00 X 180,

correcting the full manifest astigmatism will induce -1.00 X 90, which the patient may not tolerate despite zero manifest refraction.

In such a case, one of the recommendations is to correct -2.00 X 180 and adjust the sphere to achieve the same spherical equivalent (eg, 0.00 -3.00 X 180 corrected to -0.50 -2.00 X 180.

7-Pupil coordinates.The horizontal (x) coordinate of the pupil center reflects angle kappa.

The normal value of the latter is less than 100 m (5.5mm

Ablation OZ = 6.5 mm

So 1D Ablate 14um.When Scotopic pupil 470 m.

Thickness RulesRSB Rule 8

For calculations in mixed astigmatism, The equation should be converted into plus cylinder formula before calculating the RSB.

+2 D sph/4 D cyl converted to 2 D sph/+4 D cyl

RSB rules are applied on the 2 D sph

Thickness RulesRSB Rule 9

In WFGT profiles, the AD differs according to the type and severityof HOA(s).

Therefore, AD and RSB should be calculated on site.

General guidelinesThickness Rules

K-reading Rules

Astigmatism Rules

Pupil Center and Angle Kappa Rule

K-reading Rules

First The recommended amount of correction should be calculated according to RSB rules

Second then according to K-reading rules.

K-reading Rules

Flat K Rule

Correcting each 1 D reduces the flat K by 0.75 D.

Final flat K according to the amount of myopic ablation should be > 34 D.

K-reading Rules

K-max Rule

Correcting each +1 D increases K-max by 1.2 D.

K-max according to the amount of hyperopic ablation should be < 49 D.

K-reading Rules

Correcting each 1 D reduces the flat K by 0.75 D.

The final flat K > 34 D.

K-max RuleCorrecting each +1 D increases K-max by 1.2 D.

The final steep K < 49 D.

Flat K Rule


K-reading Rules

Astigmatism Rules


Astigmatism Rules

Myopic Astigmatism Rules

The astigmatic correction flattens the steep K and brings it to flat K

Thereafter, the spherical correction flattens all.

Astigmatism Rules

Hyperopic Astigmatism Rules

the astigmatic correction steepens the flat K and brings it to steepK

Thereafter, the spherical correction steepens all .

.

Astigmatism Rules

Mixed Astigmatism Rules

The astigmatic correction steepens the flat K and brings it to steep K

Thereafter, the spherical correction flattens all.


K-reading Rules

Astigmatism Rules



Angle Kappa is the angle between the visual axis and the axis that passes through the pupil center..

Angle kappa is considered significant when it is > 5 (x > 200 m).

Angle Kappa

Large angle Kapa When angle kappa is > 100 m (x > 200 m), the capture should be repeated to exclude misalignment.1-false positives or false negatives such as the skewed hourglass pattern in elevation maps.2- When treating hyperopia or 2 D of astigmatism, optimal resul ts can be achieved when the center of ablation coincides with the optical axis of the eye. This can be achieved by decentering the ablation profile for the amount of angle kappa; this is called offset pupil ordecentration.3-Finally, decentered pupil (corectopia) is a case of concern, especially when PIOL implantation is indicated.

Case 1A 27-year-old female has a stable refractive error

Case 1

Right eye Case 1The anterior elevation map:Show tong-like extension.Normal values within theThe anterior sagittal curvature map shows aSB with an insignificant SRAX and an I-S differenceThe posterior elevation map symmetric hourglasspattern.normal valuesThe pachymetry map shows normal shape.There is an insignificant S-I difference

Case 1Thickness profiles show normal slopes with a normal average

QS is OK K-maxsteep K is < 1DThickness at the TL is > 500mPachy-Thinnest difference is < 10 mY-coordinate of the TL shows an insignificant displacementPupil coordinates indicate a significant angle KappaK-readings including D K- < 49 max

Left Eye Case 1

AB pattern WTR astigmatismAnterior elevation map skewed hourglass.Posterior elevation map symmetric hourglass pattern.The pachymetry map shows a normal shapewith a borderline S-I difference

Thickness profiles show normal slopes witha normal average (0.8).

Left Eye Case 1

QS is OKK-maxsteep K is < 1DThickness at the TL is > 500 mK-readings including K-max are < 49 D.Y-coordinate of the TL shows an insignificant displacementPupil coordinates indicate an insignificant angle Kappa.PachyThinnest difference in thickness is < 10 m

Case 1Borderline shapes and parameters such asskewed hourglass,tongue-like extension and thickness parameters.

Therefore,I would recommend PRK rather than LASIK

Case 2A 35-year-old male has a stable refractive error with no othercomplaints. Eye examination is normal.

The posterior elevation map:show moderately skewed hourglass pattern.Nothing seems to be abnormal in the pachymetry mapsNothing seems to be abnormal in the anterior elevation mapsMild tong ex.The anterior sagittal curvature map shows a SB with an insignificant SRAX and a S-I difference

Thickness profiles show normal slopes witha normal average (0.9).

QS is OKPachyThinnest difference in thickness is < 10 mThickness at the TL is > 500 mK-are < 49 DY-coordinate shows no vertical displacementix. Pupil coordinates indicate an insignificant angle KappaK-maxsteep K is < 1 D

DiscussionCompound myopic astigmatism in both eyes.

Tomography show normal shapes and parameters except for the skewed hourglass on the posterior elevation map.

This patient is a good candidate for photorefractive surgery with a low risk score.

Full correction by LASIK is possible as shown by thicknessand K-reading calculations.

In spite of high AD, some surgeons may go for PRK since the RSB is > 400 m

Roland gaross

Case 3A 24-year-old male has a stable refractive error.

Hs recent glasses and corresponding VA are shown in table

Case 3

The anterior sagittal curvature map showsa AB because of an insignificant I-S difference and SRAX.The posterior elevation map:irregular pattern.normal valuesThe anterior elevation map:almost symmetrichourglass pattern.normal valuesThe pachymetry map shows normal shapewith an insignificant S-I difference

show normal slopes with a normal average (0.9).

The red curves deviate after the6-mm zone (blue arrows).

Case 3

ACD is > 3.0 mmK-maxsteep K is < 1D.K-max are < 49 DTL is > 500 m.PachyThinnest difference in thickness is < 10 m.Y-coordinate shows superior displacement,Pupil coordinates indicate significant angle Kappa

Case 3It is a high refractive error case.

Corneal thickness not good enough to proceed with photorefractive surgery. Partial correction may be proceeed.

Anterior chamber parameters and patients age are suitable for phakic IOL

Case 4

His recent glasses

Cyclopligic refraction

Post mydriatic test.

A 35-year-old male has a refractive error, and he has strain in near tasks.

Case 4

The anterior sagittal curvature map shows AB but considered SB because of an insignificant SRAX and I-S difference .almost symmetrichourglass pattern Normal value irregular pattern.normal valuespachymetry map shows a horizontal displacement of the TL and an insignificantS-I difference

Case 4Thickness profiles show normal slopes witha normal average (1.0).

Y-coordinate of the TL insignificant verticaldisplacement.Pupil coordinates indicate an insignificant angle KappaQS is OKK-readings including K-max are < 49 DK-maxsteep K is < 1DThickness at the TL is > 500Pachythinnest is < 10 m.

Case 4

4. Discussion:compound hyperopic astigmatism.

The thickness rules allow for full correction, The K-reading rules do not5x1.2 =6D +46.7 =52.7 Final K will be higher than 49 D, which leads to induction of negative spherical aberration

Case 5

A 27-year-old male has a refractive error.

He is complaining ofblurring vision, halos, ghost images and headache.

He feels thathis vision is deteriorating

FFK

Right Case 5

Irregular shape.Tongue shapeTongue shapeabnormal valuesAtypical concentric shape with an abnormal S-I difference (> 30 m).

Right Case 5

Right Thickness profiles show an S-shape (blue arrows) with a normal average (0.9).

Right Case 5

Pupil coordinates indicate decentered pupil and asignificant angle Kappa.the AC is shallow(ACD < 2.1 mmY-coordinate of the TL is normal< 500 m.QS is OKK-readings are 500 m.Pachythinnest difference in thickness is < 10 m.

Left case 5

Irregular shape or a superior-steep shape.tongue-like extension Normal values within the central 5-mmtongue-like extension Abnormal values within the central 5-mmAtypical dome-like. The S-Idifference is > 30 m

Left case 5 LeftThickness profiles show an S-shape (bluearrows) with a normal average 0.8

Left case 5

QS is OK.K-readings including K-max are < 48 DThickness at the TL is > 500 mY-coordinate of the TL is < 500 mPupil coordinates indicate decentered pupil and asignificant angle Kappa

Case 5

DiscussionThis is a case of FFKC because it is progressive reffracion change with corneal abnormal tomography not distinct enough to be classified ectatic disorders.

Conventional photorefractive surgery cannot be done.

Option 1-wavefront-guided or topo-guided PRK with CXL2-PIOL is also another option with CXL prior to implantation.

Case 5

WB

Case 6

A 24-year-old female She is complaining of blurring vision, strain and headache after near tasks with glasses.

Cycloplegic ref.Recent glasses

Post medriatic ref.sa

RT Case 6

Irregular horizontal AB pattern indicating ATR astigmatismNot typicalhourglass butit is normal symmetry.normal values within the central 5-mm circle.Tongue-like extension. normal values withinthe central 5-mm circleNormal shape in spite of superior-temporal displacement in the TL There is an insignificant S-I difference

Case 6Thickness profiles show normal slopes anda normal average (0.8).

RT Case 6

K-readings including K-max are < 48 D.K-maxsteep K is < 1 D.Thickness at the TL is > 500 m.PachyThinnest difference in thickness is < 10 m.Y-coordinate of the TL is < 500 m.ACD is > 3.0 mmPupil coordinates indicate decentered pupil and asignificant angle Kappa

Case 6There is a big difference among MR, CR and PMT,

Try contact lenses or glasses depending on PMT correction for a couple of weeks,

Then recheck the patient for adding more correction till the highest tolerable correction is reached.

In our case, the expected optimal correction is reashed

Manifest RefCycloplegic Ref Post medryatic testOptimal correction

Case 6Disscution As regarded to Corneal thickness and K-readings concept This case can be treated because preoperative

a.Corneal thickness is 550m.b. K-readings concept: 1.2x4 =48.8 D so can de treated .. -0.5Thiniet 440

CASE 7: KERATOCONUSAbnormal profiles(Quick Slope )

CASE 7: KERATOCONUSThe cornea is very prolate as shown on the topometric map with more than 0.3 difference between vertical and horizontal averages. +ve keratoconus indices,

keratoconus level three

CASE 8: KERATOCONUS POSSIBLE

AB/IS and the vortex pattern, although there is no skew in thevery central major axes. The posterior elevation map isirregular in spite of its normal values



There are two indicesin the keratoconus indices page with abnormal values,.

CASE 8: KERATOCONUS POSSIBLEThere are two indicesin the keratoconus indices page with abnormal values,

The possibility came from: the pattern of thesagittal curvature front map. As you see, other parametersare within the accepted range.

SCORING THE CASE

SCORING THE CASE

SCORING THE CASEAfter careful study of the topography, it is very important to score the case in order to

1- Exclude the risky cases2-Decide correctly which modality of treatment is the best.

Thank you

rules in refractive surgery + cases presentation

Investor Relations