Characterization of Higher Order Ocular Aberrations (HOA) In ‘Normal’ Versus Myopic Eyes To Study The Effect Of Myopia On Higher Order Aberrations Amit Gupta MS Manish Chaudhary MS Advanced Eye Centre, Postgraduate Institute of Medical Education & Research, Chandigarh India ( The authors have no financial interest in the subject matter of this poster

Role of Wavefront error assessment:  Quantitative assessment of the optical properties of the eye  To evaluate therapy (eg: refractive surgery) designed to improve the optical properties of the eye  Provides the necessary information to design optical prescriptions for the eye to minimize all refractive errors. Ethnicity and refractive errors significantly affect the wavefront aberrations. Carkeet A et al Luo H, Tong L, Saw S, Tan D. Refractive error and monochromatic aberrations in Singaporean children. Vision Reseach 2002;42: This study aimed to establish normative data on HOA in Indian population as well as to study the effect of refractive error on HOA.

Study Design: An observational cross sectional prospective study Study Population  Group I : 500 emmetropic eyes (refractive error D)  Group II : 500 myopic eyes (refractive error > to < -6.0 diopters) Purpose Patients and Methods To Characterize Higher Order Ocular Aberrations (HOA) In ‘Normal’ Versus Myopic Eyes In Order To Study The Effect Of Myopia On HOA in the Indian Population

Methods Exclusion criteria o Corneal degenerations and dystrophies o Corneal scarring after infective diseases o Dry eye patients o Any Other ocular pathology Patient Workup:  Best Corrected Visual Acuity,  Slit Lamp Biomicroscopy,  Refraction,  Schirmer’s test,  Aberrometry: Optical Path Difference (OPD) Scanning done after dilating with 0.8% tropicamide and 5% phenylephrine using ARK OPD scan (NIDEK Technologies, Japan)  Aberrometry: : Optical Path Difference (OPD) Scanning done after dilating with 0.8% tropicamide and 5% phenylephrine using ARK OPD scan (NIDEK Technologies, Japan) Inclusion criteria  Age years.  Best corrected visual acuity (BCVA)of 6/9 or better.  Normal ocular examination, emmetropia or Myopia < 6 D.

 Root mean square (RMS) of higher order aberration (HOA) from the 3rd to 6th orders  RMS of the spherical aberration (SA) (square root of the sum of the squared coefficients of Z4 0 and Z60),  RMS of coma (square root of the sum of the squared coefficients of Z3-1, Z31, Z5-1,and Z51),  RMS of trefoil (square root of the sum of the squared coefficients of Z3-3, Z33, Z5-3,and Z53 Aberrometric Analysis by OPD Scan Thibos et al. Standards for reporting the optical aberrations of eyes. J Refract Surg 2002; 18:S652–S660 Aberrometric Data Interpretation and Analysis Step 1: OPD Scan AnalysisStep 2: Zernike polynomials were transformed into Step 3: Statistical Analysis  ‘t-test’ (for normal Distribution) & for skewed data Mann- Whitney test.  Relationship between different variables using Spearman and Pearson correlation coefficient

Results Group I (Emmetropic)Group II (Myopic) Male14790 Female Mean age (Yrs) Both the groups were age matched Patients characteristics in emmetropic and myopic group Patients characteristics in emmetropic and myopic group

Emmetropia (mean +SD mm) Myopia (mean + SD mm) Significance ( p-value ) Total wavefront aberration Total HOA nd order rd order th order th order th order Coma Spherical aberration Trefoil All the ocular aberration were significantly higher in myopic group Ocular Aberrations in Emmetropic versus Myopic Eyes

Comparative data of wavefront aberrations ( Emmetropic versus myopic eyes ) All the ocular aberration were statistically higher in myopic group

Correlation of ocular aberrations with magnitude of Myopia Contribution of each order to the overall Higher Order aberrations in emmetropic and myopic eyes Amount of HOAs are well correlate to amount of refractive error as the amount of refractive error increase the amount of HOAs increases Correlation of HOAs with Degree of Myopia Correlation coefficient Significance ( p-value ) Total wavefront aberration Total HOA nd order rd order th order th order th order Coma Spherical aberration Trefoil Emmetropi a Myopia Significance (p -value) 3 rd order60.08 %59.87 % th order23.40 %23.16 % th order11.64 %10.78 % th order4.86 %6.19 % 0.019

HOAs are correlated with amount of refractive error as the amount of myopia increase the value of HOAs increases Scatter diagram Showing the Correlation of HOAs with degree of Myopia

Comparison of our aberrometric data with reported data Parameter Our study (India) Salmon and van de pol (USA) Netto et al (USA) Wei et al (Singapore) Wang et al (USA) Nakano et al (Brazil) Sample size (eyes) EthnicityIndianMixedCaucasianChineseNSAsianNon Asian Aberrometri c principal & instrument used OPD scan (Nidek) Hartmann Shack, multiple aberrometer s Hartmann Shack, Wave scan (visx) Hartmann Shack, Zywave(Bau sh & Lomb Hartmann Shack, Wave scan (visx) OPD scan (Nidek) HOA RMS0.35 ± ± ± ± ± ± ± rd order0.2 ± ± 0.12NS 0.37 ± ± 0.09NS 4 th order 0.08 ± ±0.09NS0.29± ±0.06NS 5 th order0.04 ± ±0.03NS0.08± ±0.03NS 6 th order0.023 ±0.03NS Coma0.12 ± 0.13NS0.14± ± ± ± ±0.45 Trefoil0.16 ±0.16NS0.10±0.07NS 0.29± ±0.31

Summary And Conclusions The emmetropic and myopic groups showed significant differences for higher order aberration for 3rd, 4th, 5th and 6th-order aberrations. All the differences were highly significant (p<0.001) Ocular wavefront aberrations varied greatly from subject to subject. There was no correlation with age as well sex of individuals in both groups. Amount of refractive error significantly affects the amount of aberration. As refractory error increases, the amount of aberration as well as HOAs also increases but this correlation is not a linear relation The right and left eye of subjects showed no significant difference in amount of HOAs and well correlated to each other. This is the first study comparing wavefront aberrations in the emmetropic versus myopic eyes in Indian population.