Amit Gupta MS Manish Chaudhary MS Advanced Eye Centre,

Postgraduate Institute of Medical Education & Research,

ChandigarhIndia

(Email : amitguptaeye@gmail.com)

The authors have no financial interest in the subject matter of this posterThe 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;42:1809-1824.

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

0+0.25 D) Group II : 500 myopic eyes (refractive error > -

0.25 to < -6.0 diopters)

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

Exclusion criteriao Corneal degenerations

and dystrophieso Corneal scarring after

infective diseaseso Dry eye patientso Any Other ocular

pathology

Patient Workup:Patient Workup: Best Corrected Visual Best Corrected Visual

Acuity, Acuity, Slit Lamp Biomicroscopy, Slit Lamp Biomicroscopy, Refraction, Refraction, Schirmer’s test, Schirmer’s test, Aberrometry:Aberrometry: : Optical Path Optical Path

Difference (OPD) Scanning Difference (OPD) Scanning

done after dilating with done after dilating with

0.8% tropicamide and 5% 0.8% tropicamide and 5%

phenylephrine using ARK-phenylephrine using ARK-

10000 OPD scan (NIDEK 10000 OPD scan (NIDEK

Technologies, Japan)Technologies, Japan)

Inclusion criteria

Age 18-40 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 Root mean square (RMS) of higher order aberration (HOA) from the 3rd to 6th aberration (HOA) from the 3rd to 6th ordersorders

RMS of the spherical aberration (SA) RMS of the spherical aberration (SA) (square root of the sum of the squared (square root of the sum of the squared coefficients of Z4 0 and Z60), coefficients of Z4 0 and Z60),

RMS of coma (square root of the sum of RMS of coma (square root of the sum of the squared coefficients of Z3-1, Z31, Z5-the squared coefficients of Z3-1, Z31, Z5-1,and Z51),1,and Z51),

RMS of trefoil (square root of the sum of RMS of trefoil (square root of the sum of the squared coefficients of Z3-3, Z33, Z5-the squared coefficients of Z3-3, Z33, Z5-3,and Z533,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 Analysis

Step 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

Group I

(Emmetropic)

Group II

(Myopic)

Male 147147 9090

Female 103103 160160

Mean age (Yrs) 28.40 28.40 ++ 7.4 7.4 27.82 27.82 + + 5.49 5.49

Both the groups were age matched

Patients characteristics in emmetropic and myopic groupPatients characteristics in emmetropic and myopic group

Emmetropia

(mean +SD mm)

Myopia

(mean + SD mm)

Significance

( p-value )Total wavefront aberration

1.04 + 0.91 4.48 + 2.73 0.001

Total HOA 0.24 + 0.14 0.35 + 0.32 0.001

2nd order 0.536 + 0.644 2.4 + 1.56 0.001

3rd order 0.145 + 0.089 0.204 + 0.193 0.001

4th order 0.056 + 0.04 0.084+ 0.098 0.001

5th order 0.026 + 0.019 0.037 + 0.044 0.001

6th order 0.0114 + 0.012 0.0234 + 0.033 0.001

Coma 0.0836 + 0.053 0.117 + 0.136 0.001

Spherical aberration

0.101 + 0.085 0.148 + 0.204 0.001

Trefoil 0.117 + 0.083 0.161 + 0.161 0.001

All the ocular aberration were significantly higher in myopic group

Ocular Aberrations in Emmetropic versus Ocular Aberrations in Emmetropic versus Myopic EyesMyopic 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

0.466 0.001

Total HOA 0.169 0.001

2nd order 0.398 0.001

3rd order 0.15 0.001

4th order 0.125 0.005

5th order 0.154 0.001

6th order 0.18 0.001

Coma 0.16 0.001

Spherical aberration

0.089 0.046

Trefoil 0.102 0.023

Emmetropia

Myopia Significance(p -value)

3rd order

60.08 % 59.87 %0.174

4th order

23.40 % 23.16 %0.086

5th order

11.64 % 10.78 %0.003

6th order

4.86 % 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 MyopiaScatter 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)

Nakano et al (Brazil)

Sample size (eyes)

500 2560 418 166 532 384 264

Ethnicity Indian Mixed Caucasian Chinese NS Asian Non Asian

Aberrometric principal & instrument used

OPD scan (Nidek)

Hartmann Shack, multiple aberrometers

Hartmann Shack, Wave scan (visx)

Hartmann Shack, Zywave(Baush & Lomb

Hartmann Shack, Wave scan (visx)

OPD scan (Nidek)

OPD scan (Nidek)

HOA RMS 0.35 ± 0.32

0.33± 0.13 0.23± 0.11 0.49± 0.16 0.30± 0.09 0.51± 0.71 0.55± 0.70

3rd order 0.2 ± 0.19 0.25 ± 0.12

NS 0.37 ± 0.16

0.22 ± 0.09

NS NS

4th order 0.08 ± 0.09

0.169±0.09

NS 0.29±0.11 0.16±0.06 NS NS

5th order 0.04 ±0.04 0.067±0.03

NS 0.08±0.04 0.07±0.03 NS NS

6th order 0.023 ±0.03

NS NS NS NS NS NS

Coma 0.12 ± 0.13

NS 0.14±0.08 0.27± 0.14 0.17±0.08 0.23±0.30 0.29±0.45

Trefoil 0.16 ±0.16 NS 0.10±0.07 NS NS 0.29±0.35 0.30±0.31

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.