Effect of mydriasis on chord mu value in cataract surgery candidates.

PURPOSE

This study investigates the relationship between pupil size during biometry examinations and the chord mu value in candidates for cataract surgery.

METHODS

Retrospective analysis of ocular biometry measurements was performed on consecutive cataract surgery candidates above 50 years of age, examined between 2018 and 2020 at a single tertiary referral center. Statistical analysis assessed the association between pupil size and the chord mu value. The population was categorized into groups based on pupil size, and an analysis was conducted on the barycenter positions of the iris and pupil center for each group.

RESULTS

The analysis included 2877 patients. A weak positive correlation was observed between the chord mu value and pupil size using Pearson's test ( = 0.160,  < 0.01). Group stratification by pupil size indicated temporal and inferior shifts in pupil center barycenter as pupil size increased, reflecting asymmetrical pupil dilation during mydriasis. A moderate positive correlation between the chord mu value and chord alpha value was identified (Pearson's test,  = 0.641,  < 0.01). As expected, no correlation was found between chord alpha value and pupil size.

CONCLUSIONS

Chord mu values were higher in patients with mydriatic pupils, likely due to asymmetric pupil dilation and center displacement. Evaluating chord mu values requires considering pupil status and conducting biometry under standardized lighting to prevent misinterpretation caused by pharmacological dilation. This caution is crucial to avoid erroneously excluding eligible patients from multifocal IOL implants. Alternatively, the chord alpha value could serve as a more appropriate alternative in such scenarios.