Transcript Characterization Of Higher Order Ocular Aberrations (HOA) In

Amit Gupta MS
Manish Chaudhary MS
Advanced Eye Centre,
Postgraduate Institute of Medical Education & Research,
Chandigarh
India
(Email : [email protected])
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;42:1809-1824.
This study aimed to establish normative data on HOA in
Indian population as well as to study the effect of
refractive error on HOA.
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
Patients and Methods
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)
Inclusion criteria



Age 18-40 years.
Best corrected visual acuity
(BCVA)of 6/9 or better.
Normal ocular examination,
emmetropia or Myopia < 6 D.
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 ARK10000 OPD scan (NIDEK
Technologies, Japan)
Aberrometric Data Interpretation and Analysis
Step 1: OPD Scan Analysis
Step 2:




Zernike polynomials were transformed into
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
Thibos et al. Standards for reporting the optical aberrations of eyes. J Refract Surg
2002; 18:S652–S660
Aberrometric Analysis by
OPD Scan
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
Patients characteristics in emmetropic and myopic group
Group I (Emmetropic)
Group II (Myopic)
Male
147
90
Female
103
160
Mean age (Yrs)
28.40 + 7.4
27.82 + 5.49
Both the groups were age matched
Ocular Aberrations in Emmetropic versus
Myopic Eyes
Emmetropia
Myopia
Significance
(mean +SD mm)
1.04 + 0.91
(mean + SD mm)
4.48 + 2.73
( p-value )
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
0.101 + 0.085
0.148 + 0.204
0.001
0.117 + 0.083
0.161 + 0.161
0.001
Total wavefront
aberration
Spherical
aberration
Trefoil
All the ocular aberration were significantly higher in myopic group
Comparative data of wavefront aberrations ( Emmetropic versus
myopic eyes )
All the ocular aberration were statistically higher in myopic group
Correlation of HOAs with Degree of Myopia
Correlation of ocular aberrations with
magnitude of Myopia
Correlation
coefficient
Total wavefront
aberration
0.466
Significance
( p-value )
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
0.089
0.046
0.102
0.023
Spherical
aberration
Trefoil
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
Myopia
Significance
(p -value)
3rd order
Emmetropi
a
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
Scatter diagram Showing the Correlation of HOAs with degree of Myopia
HOAs are correlated with amount of refractive error as the amount of
myopia increase the value of HOAs increases
Comparison of our aberrometric data with reported data
Parameter
Our study
Sample size
(eyes)
500
Salmon and
van de pol
(USA)
2560
Ethnicity
Indian
Mixed
Caucasian
Hartmann
Hartmann
Hartmann
OPD scan
Shack, Wave Shack,
Shack, Wave (Nidek)
scan (visx)
Zywave(Bau scan (visx)
sh & Lomb
OPD scan
(Nidek)
0.23± 0.11
0.49± 0.16
0.51± 0.71
0.55± 0.70
(India)
Aberrometri OPD scan
c principal & (Nidek)
instrument
used
Netto et al
(USA)
Wei et al
(Singapore)
Wang et al
(USA)
Nakano et al Nakano et al
(Brazil)
(Brazil)
418
166
532
384
264
Chinese
NS
Asian
Non Asian
HOA RMS
0.35 ± 0.32
Hartmann
Shack,
multiple
aberrometer
s
0.33± 0.13
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
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
0.067±0.03
0.30± 0.09
This is the first study comparing wavefront aberrations in the
emmetropic versus myopic eyes in Indian population.
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.