Distribution of corneal spherical aberration in a Tanzanian population

Hiroki Asano,Yusuke Seki,Takanori Saruta,Natsuko Hatsusaka,Yoshiaki Tabata,Hiroshi Sasaki,Takahiro Hiraoka,Tetsuro Oshika,Hiromi Osada,Teppei Shibata,Cellina Mhina,Anna Sanyiwa,Fukumi Fujikake,Hidenaga Kobashi

doi:10.1371/journal.pone.0222297

Abstract

PurposeTo investigate the distribution of corneal spherical aberration (SA) in Tanzanian people of African descent, and to examine the correlation between corneal SA and ocular parameters.DesignCross-sectional population-based study.MethodsResidents aged 40 years and older in three villages in the Mkuranga district in Tanzania were enlisted as study participants. Corneal higher-order aberrations (HOAs) for the right eye were measured with a wavefront analyzer (KR-1W, Topcon) and calculated for the central 6.0-mm zone. Corneal curvature radius (CR), corneal astigmatism, and axial length (AL) were also measured and their correlation with corneal SA was assessed.ResultsThe right eyes of 657 participants (336 male, 321 female) were analyzed. The mean age of the subjects was 57.2 ± 10.3 years (mean ± SD). The mean corneal SA (Zernike spherical aberration coefficient C40) was 0.188 ± 0.095 μm (-0.242 to 0.613). The SAs in about three-quarters of all subjects were between 0.10 and 0.30 μm. The root mean squares of total corneal HOAs and the third- and fourth-order aberrations were 0.629 ± 0.250 μm, 0.539 ± 0.236 μm, and 0.269 ± 0.110 μm, respectively. Corneal SA showed weak significant correlations with CR (Spearman’s rank correlation coefficient, r = -0.177, p < 0.001), corneal astigmatism (r = -0.142, p < 0.001), AL (r = -0.168, p < 0.001), and age (r = -0.085, p < 0.05).ConclusionsThis finding may be beneficial for selecting aspheric intraocular lens in this population.

Highlights

In recent times, the goal of cataract surgery has been to restore visual acuity and achieve better quality of vision (QOV), such as improvement in contrast sensitivity
Corneal spherical aberration in a Tanzanian population. This finding may be beneficial for selecting aspheric intraocular lens in this population
Among all the components of higher-order aberrations (HOAs) derived from the cornea, only spherical aberration (SA) is correctable with commercially available aspherical intraocular lenses (IOLs)

Summary

Introduction

The goal of cataract surgery has been to restore visual acuity and achieve better quality of vision (QOV), such as improvement in contrast sensitivity. Among all the components of HOAs derived from the cornea, only spherical aberration (SA) is correctable with commercially available aspherical intraocular lenses (IOLs). As the value of corneal SA is generally positive [2,3,4,5], aspherical IOLs designed to have a negative SA cancel the positive SA of the cornea and reduce the whole ocular SA, leading to an improvement in visual function, including contrast sensitivity [6,7,8,9]. Aspherical IOLs with negative SA, such as Tecnis ZCB00 (Abbott Medical Optics, Santa Ana, CA, USA) and AcrySof IQ SN60WF (Alcon Laboratories Inc., Fort Worth, TX, USA) are designed to compensate for positive corneal SA by -0.27 and -0.20 μm, respectively

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