The effect of cycloplegia on corneal power and diameter measured by an auto-kerato-refractometer in presbyopic patients with type 2 diabetes mellitus: a post-hoc analysis of a randomized clinical trial

Abstract Background To assess the effect of cycloplegia on keratometry and horizontal white to white (WTW) measurements in presbyopic patients with type 2 diabetes. Methods The post-hoc analysis included 88 eyes from 88 patients with type 2 diabetes aged >40 years. Flat keratometry (Kf), steep keratometry (Ks), mean keratometry (Km), corneal astigmatism (CA), and WTW were measured using the RC-5000 auto kerato-refractometer (Tomey Inc., Nagoya, Japan), before and thirty minutes after the instillation of two drops (administered five minutes apart) of either 0.5% (46 patients) or 1% tropicamide (42 patients). Results The mean changes in Kf, Ks, Km, CA, and WTW were − 0.01 ± 0.26 D, -0.05 ± 0.23 D, -0.03 ± 0.19 D, -0.04 ± 0.31 D, and 0.05 ± 0.24 mm, respectively, in the 0.5% tropicamide group. These values were − 0.07 ± 0.28 D, 0.01 ± 0.23 D, -0.03 ± 0.21 D, 0.08 ± 0.29 D, and 0.04 ± 0.15 mm, respectively, in the 1% tropicamide group. The changes following cycloplegia were not statistically significant (P ˃ 0.05). Conclusions Post-cycloplegia keratometry and WTW measurements were comparable to pre-cycloplegia values in presbyopic patients with type 2 diabetes, suggesting that these measurements can be reliably obtained after cycloplegia. Trial registration IRCT.ir, registration number: IRCT20200829048553N1, 2021-05-31. ClinicalTrials.gov, ID: NCT04932213, 2021-06-21.