Comparison of higher order aberrations in patients with various refractive errors

Saim Khan,Fawad Mashhadi,Sabahat Arzoo,Aisha Fawad,Mazhar Ishaq,Sadia Humayun

doi:10.12669/pjms.314.7538

Abstract

Objective:To compare the mean root mean square (RMS) of total higher order aberrations (HOAs), coma and spherical aberrations in individuals with myopia, hypermetropia and myopic astigmatism.Methods:This prospective analytical study was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from Jan 2014 to Dec 2014. Two hundred eyes of 121 patients with age ranging from 18-40 years were included in the study. Patients were divided into 4 group namely Low myopia, High myopia, Astigmatism and Hypermetropia on the basis of refractive error. Included were the patients who had refractive error more than ± 0.5D and best corrected visual acuity (BCVA) of 0.00 or better. Patients who had history of surgery and / or eye disease were excluded from the study. Visual acuity (VA), Spherical equivalent (SE) of refractive error, RMS value of total HOAs, coma and spherical aberrations were evaluated. HOAs were measured with aberrometer (Wavelight analyzer version 1073) at 6 mm pupil size.Results:Age of the patients ranged from 18 years to 40 years with mean age of 29.10±10.6 years. Seventy one (35.5%) were males and 129 (64.5%) were female. Mean RMS value of HOAs, coma and spherical aberrations was calculated in all four groups. RMS of total HOAs and spherical aberrations in hypermetropia was 0.96±0.96 and 0.30±0.42 respectively and it was higher than other three groups.Conclusions:In overall comparison the mean RMS of total HOAs and spherical aberrations was significantly increased in hypermetropia group and there was a statistically significant negative correlation of SE of hypermetropia with RMS of total HOAs and spherical aberration.

Highlights

Higher order aberrations are small optical irregularities of the ocular refractive media
Unlike low order aberrations they cannot be corrected with spectacles or contact lenses
Refractive error was described in terms of spherical equivalent and it ranged from +6.00 to - 10.50 D

Summary

Introduction

Higher order aberrations (spherical aberrations, coma, trefoil) are small optical irregularities of the ocular refractive media. Popularization of laser corneal refractive surgery and its potential to induce or remove optical aberrations (both low order and higher order aberrations) is the main reason behind better understanding of the nature of aberrations as well as their influence on visual quality.[2] In the normal eye, cornea is responsible for 90% of total aberrations and Zernike polynomials are most commonly used to describe these HOAs. Advent of new diagnostic modalities and introduction of wave front technology has brought revolution in the field of corneal refractive surgery. Advent of new diagnostic modalities and introduction of wave front technology has brought revolution in the field of corneal refractive surgery These advancements has expanded the indications of corneal refractive surgery beyond correcting only low order aberrations.[3]

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