Validation of Clinical Protocol of Astigmatism Induction in Pseudophakic Patients

Purpose: Validate a novel approach for assessing residual astigmatism's impact on visual acuity in pseudophakic patients using defocus curves and spherical equivalent compensation.

Materials and methods: Thirteen patients over 40 with cataracts and normal ophthalmological examinations were enrolled in a prospective, non-randomized cohort study. The defocus curve method was employed, wherein visual acuity was measured with spherical lenses ranging from -2.50 to +2.50 diopters in 0.5 diopter increments based on subjective refraction. Cylindrical lenses (+1, +2, and +3 diopters) were introduced at each spherical diopter's 90° and 180° axes. Curves' results were compared at each defocus point to assess the impact of astigmatism. The Kruskal-Wallis test was used to determine if astigmatism significantly affected visual acuity post-phacoemulsification surgery with intraocular lens implantation.

Results: Significant p-values were observed only for defocus curve points of -0.5, 0, +0.5, and +1, indicating rejection of the hypothesis of no difference between the 90° and 180° groups at these points. Although statistical significance was not achieved, the against-the-rule (ATR) group was inclined toward improved near and intermediate visual acuity. In contrast, the with-the-rule (WTR) group tended to enhance distance visual acuity and myopic tolerance.

Conclusion: This novel methodology is both reproducible and valuable. It offers potential insight into residual astigmatism tolerance in pseudophakic patients. Its application may aid in surgical planning and intraocular lens decision-making.