FP1238 : Pupillodynamics And Corneal Spherical Aberrations In Selection Of Aspheric IOL In Indian Population

Dr. Mukesh Paryani, P16420, Dr. Darak Ambarish Balkrishna

Introduction:

Nowadays, cataract surgery has become a refractive procedure. The patient’s demand is not only limited to the improvement in visual acuity, but also better visual quality. Therefore, wavefront aberrations have become an important parameter for evaluating visual quality(1). Studies have already proven the effect of pupil size on higher order aberrations (HOAs).Higher the pupillary size, higher are HOAs (2) (3).

Benefits of aspheric lenses have been shown in several studies. However, adjustment of the cornea’s positive spherical aberration by an aspheric IOL can be demonstrated only in larger pupils(4).

To our knowledge, the average pupillary diameter in indian population has not been studied till now. Also the average spherical aberrations in Indian population at different diameters has not been studied

Aim:

The aim of our study is to assess the pupillary diameter and spherical aberrations in Indian eyes under photopic , mesopic and scotopic conditions

Materials and methods:

In this prospective observational study, 104 eyes of 52 patients planned for cataract surgery ,underwent pre-operative pupillary size measurement at different conditions, scotopic , mesopic and photopic using Sirius Topography (CSO) . Patient with other ocular co-morbidities were excluded from the study.

The Sirius Topographer measures the Pupil diameter in different luminance of 0.4 lux, 4 lux and 40 lux for scotopic, mesopic and photopic condition respectively

All the  measurements were taken by single clinician after dark adaption for a period of two minutes. The pupil diameter were first measured for scotopic Right eye then Scotopic left eye and  then similarly for other two mesopic and photopic conditions

The average mesopic pupil for all patients was calculated first

The corneal spherical aberrations were measured at two zones. First at the calculated average mesopic pupillary size and at 6 mm zone and both were compared

Results:

The mean age of population was 53 years. the mean scotopic, mesopic and photopic pupil size was 4.367mm ,3.920mm and 3.365mm resp. the mean corneal spherical aberration measured at 6mm zone was 0.225microns and at 4mm zone was 0.063microns. there was statistical difference in amount of spherical aberration at 6mm and at 4mm zone

Conclusion: 

the average mesopic papillary size being close to 4mm demonstrates lower spherical aberrations as compared to 6mm zone spherical aberrations . .this would perhaps indicate the role of customising and selecting IOL s based on spherical aberrations of cornea measured at the zone equalling the mesopic pupillary size for optimal visual outcome and not generalising highly negative aspheric IOLs for all cataract surgeries which would overcorrect corneal spherical aberration. However larger sample sized studies are required to for further validation

References:

1. Charman WN. Wavefront aberration of the eye: a review. Optom Vis Sci. 1991;68:574–583.
2. de Castro LE, Sandoval HP, Bartholomew LR, Vroman DT, Solomon KD. High-order aberrations and preoperative associated factors. Acta Ophthalmol Scand. 2007;85:106–110.
3. McKelvie J, McArdle B, McGhee C. The influence of tilt, decentration, and pupil size on the higher-order aberration profile of aspheric intraocular lenses. Ophthalmology. 2011;118:1724–1731.
4. Kohnen T¹, Klaproth OK. Aspheric intraocular lenses Ophthalmologe.   2008 Mar;105(3):234-40..