Characteristics of Posterior Corneal Astigmatism in Cataract Patients with High Myopia

Objective: To evaluate the characteristics of posterior corneal astigmatism (PA) in cataract patients with high myopia. Methods: In this series of case study, 215 eyes of 215 patients from Shanxi Eye Hospital were recruited from January to June 2018 and divided into a high myopia group (94 patients, 94 eyes) and a control group (121 patients, 121 eyes). PA, total corneal astigmatism (TA) and simulated keratometric astigmatism (KA) were measured by arotating Scheimplfulg camera (Pentacam HR). The error produced by TA using KA was calculated with vector and arithmetical analysis. Data were analyzed by t test and correlation analysis Results: In the high myopia group, the mean magnitude of the pa was -0.33±0.20 D, and exceeded 0.5 D in 30.8%. The steepest meridian was vertically aligned in 79.6% of the cases. In the control group, the mean magnitude of the PA was -0.31±0.18 D. There was no significant difference in PA between the high myopia group and the control group (t=0.589, P=0.557). In the high myopia group, the vector error between KA and TA was (0.12±0.21) D@4°. There was a correlation between the magnitude of PA and KA, PA and Km (KA), and PA and Km (PA) (r=0.340, P=0.001; r=0.285, P=0.006; r=0.333, P=0.001). For KA>0.5 D patients, the difference in magnitude between ta and Ka significantly increased with an increase in the magnitude of pa (r=0.235, P=0.004). Conclusion: There was no significant difference in PA between the high myopia group and the control group. In the high myopia group, neglecting PA may lead to an incorrect estimate of ta. Personalized PA should be considered in patients with Toric intraocular lens implants. Key words: posterior corneal astigmatism; high myopia; cataract