Fellow eye parameter substitution for IOL calculation in APAC

This retrospective study investigated whether substituting fellow-eye biometric parameters reduced postoperative hyperopic prediction error after cataract surgery in eyes with acute primary angle closure (APAC).

Thirty-six patients (72 eyes) who underwent bilateral cataract surgery for unilateral APAC and the fellow eye were included. For APAC eyes, refractive prediction error (PE) at 1 month postoperatively using the standard method was compared with that calculated by substitution methods in which keratometry (K) and/or axial length (AL) were primarily replaced with corresponding fellow-eye values. Multiple linear regression was performed, with the change in PE between the standard and substitution methods (ΔPE) as the dependent variable, and interocular differences in K (ΔK) and AL (ΔAL) as explanatory variables. Receiver operating characteristic (ROC) curve analysis explored thresholds of ΔK and ΔAL associated with a > 0.50 D reduction in hyperopic PE after substitution.

With the SRK/T formula, the mean PE decreased from + 0.61 ± 0.73 D (standard) to + 0.27 ± 0.93 D with combined K + AL substitution (p = 0.045). Barrett Universal II formula showed a similar trend without reaching statistical significance. ΔPE was significantly associated with ΔAL in SRK/T (β = 2.45, p < 0.001) and with both ΔK (β = 0.77, p < 0.001) and ΔAL (β = 2.77, p < 0.001) in Barrett Universal II. ROC analysis identified a ΔAL threshold of + 0.23 mm as an exploratory cutoff.

Substituting fellow-eye AL during IOL power calculation may reduce hyperopic PE in APAC.