Analysis of Ocular Wavefront Aberrations in Post Penetrating Keratoplasty Eyes with Two Different Hartmann-Shack

Aberrometers Adriana S. Forseto1, MD; Telma Pereira2, MD; Vera

Mascaro2, MD; Lucila Pinto1, MD; Walton Nosé1,2, MD

1Eye Clinic Day Hospital 2Federal University of São Paulo - UNIFESP

São Paulo - Brazil

The authors have no financial interest in the subject matter of this poster

Introduction Penetrating keratoplasty (PKP) is still widely performed as a treatment option

for the correction of advanced keratoconus. However, visual rehabilitation is so far influenced by the presence of different degrees of refractive errors.

Several surgical refractive treatments have already been proposed. Unfortunately, the amount of total higher-order aberrations (HOA) present in these eyes is faraway that observed in non operated eyes. This may influence the visual quality experienced by these patients.

Many wavefront sensors have more difficulty of measuring the ocular aberrations on eyes with highly irregular corneas. Inaccuracies in wavefront measurements may compromise clinical testing and the refractive correction procedures.

Another concern is the presence of possible discrepancies between the wavefront-derived refractions and the clinical measurements, since many customized ablation platforms use these data to treat the refractive error.

PurposeTo analyze ocular order aberrations derived from

Ladarwave (Alcon) and Zywave (Bausch & Lomb) devices in eyes after penetrating

keratoplasty (PKP) for keratoconus (KC) and to compare the clinical refraction with the lower

order aberrations obtained from these two aberrometers

Methods

Inclusion criteriaMinimum age: 18 yoHistory of PKP for KCClear corneal graftPrevious removal of

all keratoplasties sutures

Exclusion criteriaOther ocular

pathology than KCOther previous

surgery than PKPContact lens wear

Thirty eyes were evaluated with 2 wavefront (WF) sensors:Ladarwave and Zywave

Methods The WF refractions were evaluated for 3.50mm pupil

and compared with the clinical measurements (manifest and cycloplegic), after conversion to power vectors coordinates: spherical equivalent (M or Sph Eq), J0 and J45 (astigmatism)(1)

The WF aberrations (up to the 4th order) were compared between the 2 devices (6.00mm pupil size)

Parametric testing was used with a significant level of p < 0.05

(1)Thibos LN, Wheeler W, Horner DG. Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error. Optom Vis Sci 1997;74:367-375.

Results The mean time between PKP and WF examinations

was: 5.95±4.37 years (range, 1 to 15 years)

The Zywave aberrometer was unable to capture the images in 3 eyes and the Ladarwave in one of them

Centroids view and processed image in post PKP eyeNote the irregularities at the periphery

ResultsCorrelation between the manifest and the Ladarwave and the Zywave derived refraction

Manifest refraction Ladarwave Zywave

Sph Eq r = 0.97p < 0.001 *

r = 0.97p < 0.001 *

Vector J0 r = 0.97p < 0.001 *

r = 0.97p < 0.001 *

Vector J45r = 0.92

p < 0.001 *r = 0.94

p < 0.001 *Both wavefront devices derived refractions were highly correlated to clinical manifest refraction

Results

Cycloplegicrefraction Ladarwave Zywave

Sph Eq r = 0.99p < 0.001 *

r = 0.99p < 0.001 *

Vector J0 r = 0.97p < 0.001 *

r = 0.95p < 0.001 *

Vector J45r = 0.91

p < 0.001 *r = 0.94

p < 0.001 *

Correlation between the cycloplegic and the Ladarwave and the Zywave derived refraction

Both wavefront devices derived refractions were highly correlated to clinical cycloplegic refraction

Results

Variables Clinical Refraction WF sensor derived-refractionManifest Cycloplegic Ladarwave Zywave

Mean Sph Eq (SD) -3.65 (3.75) -2.98 (3.99) -3.30 (4.20) -2.80 (4.18)Range -15.00 to 1.75 -15.00 to 3.38 -16.09 to 3.61 -15.49 to 4.02Mean J0 (SD) 0.34 (1.62) 0.23 (1.77) 0.31 (2.01) 0.11 (2.13)Range -2.13 to 3.20 -2.11 to 3.45 -2.99 to 3.78 -3.03 to 3.78Mean J45 (SD) -0.29 (1.41) -0.25 (1.67) -0.29 (1.67) -0.27 (1.54)Range -2.17 to 2.75 -2.35 to 2.57 -4.42 to 2.84 -3.09 to 2.49

Statistically significant differences (p < 0.05) were found between:•LADARWave Sph Eq and Zywave Sph Eq•LADARWave J0 and Zywave J0• Zywave SphEq and the manifest Sph Eq•LADARWave Sph Eq and the cycloplegic Sph Eq

Analysis of variance with repeated measurements of the clinical and the wavefront sensors-derived refractions

ResultsMean values of total HOA, 3rd and 4th HOA

1.791.74

0.84 0.78

1.21 1.22

0.59 0.6

0.3 0.250.480.43

00,20,40,60,8

11,21,41,61,8

RMS

(micr

a)

HOA coma trefoil spherical secastigmatism

quadrifoil

Aberrations

LadarwaveZywave

•No statistically significant discrepancies in higher-order aberrations (HOA) measurements between the two Hartmann-Shack devices were observed. •Trefoil aberrations were dominant when compared to coma or spherical aberrations in post-PKP eyes.

(6.00mm pupil)

ConclusionsEyes with PK have a great amount of

ocular aberrations The correction of these aberrations may

be limited by the discrepancies among the wavefront refractions and the clinical measurements, since these customized ablation platforms use their own data to treat the refractive error

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