<p>Contributions of Anterior Corneal and Ocular Residual Astigmatism to Autorefraction Astigmatism in a Myopic Adult Sample</p>

Abstract

Aim To evaluate the contributions of anterior corneal and ocular residual astigmatism to autorefraction astigmatism in adult myopic and myopic astigmatic subjects and how these compensate each other. Subjects and Methods This retrospective study was completed in private eye centre, Ismailia, Egypt, between September 2017 and November 2019. The study included eyes with myopia (0.5 to 10.0D) or myopic astigmatism (0 to 8.5D). The refractive errors, including autorefraction astigmatism, were measured after using 1% cyclopentolate with autorefractometer (Topcon, Tokyo Optical Co., Ltd., Japan). Corneal topography (Sirius; CSO, Florence, Italy) was used to measure anterior corneal astigmatism. Ocular residual astigmatism was measured by vectorial subtraction of the anterior corneal astigmatism from autorefraction astigmatism determined to the corneal plane. Results This study included 1158 eyes (right 582 and left 576) with myopia or myopic astigmatism of 582 participants (206 males with 406 eyes and 376 females with 752 eyes). The mean±SD age of the total participants was 26±5.7 years, range (21 to 50 years). The mean±SD of spherical error was −3.2±1.9D, range (−0.5 to −10.0D). The mean±SD of autorefraction astigmatism was 1.13±1.1D; range (0.5 to 8.5D). The mean±SD of anterior corneal astigmatism was 1.22±0.8D; range (0.03 to 5.6D). The mean±SD of ocular residual astigmatism was 0.6±0.5D; range (0 to 4.8D). Of the total eyes, 75.4% had significant autorefraction astigmatism, 82.5% had significant anterior corneal astigmatism, and 16.8% had significant ocular residual astigmatism. Conclusion The percentage of the significant autorefraction astigmatism (>0.5D) was 75.4% which is mainly anterior corneal. In 26.8% of participants, anterior corneal astigmatism is compensated by ocular residual astigmatism.

Evaluation of Refractive Accuracy of ORA and the Factors Impacting Residual Astigmatism in Patients Implanted with Trifocal IOLs During Cataract Surgery: A Retrospective Observational Study

“…The outcome of refractive and cataract surgeries depends upon insight into the distribution of different astigmatic components, their relationship, and the counteractive or superimposed effect between ACA and ocular residual astigmatism based on the type of astigmatism, ie, ATR or WTR. 23 , 24 Interestingly, a negative correlation between residual astigmatism and preoperative ACA was observed in this study, congruent to the findings of Lin J who found that ACA was offset by ocular residual astigmatism in 84.8% (140) of eyes. 24 This can be due to the greater appearance of the posterior cornea’s ATR astigmatic component in cases of low WTR astigmatism of the anterior cornea as a consequence of steep meridian incision from the superior side.…”