Objective: To assess refractive outcome and compare the accuracy of SRK-II and SRK/T formula in acute primary angle closure and primary angle closure patients with normal open angle patients undergoing cataract surgery.
Material and Method: This retrospective study included 517 eyes divided in 3 groups; 19 eyes in acute primary angle closure group, 184 eyes in primary angle closure group and 368 eyes in normal open angle group, undergoing cataract surgery by using single-piece IOL implantation. The SRK-II and SRK/T formula were used to calculate IOL power in all groups. The accuracy of each formula was analyzed by comparing the mean difference between the predicted post-operative spherical equivalent in each formula and post-operative spherical equivalent (ME). Anterior segment biometry including axial length and anterior chamber depth were compared for searching the related factor of inaccuracy of IOL power calculations.
Results: In acute primary angle closure group, the mean best-corrected visual acuity in logarithm of the minimum angle of resolution was worst, the number of anti-glaucoma drugs was most using, the intraocular pressure was highest, the axial length was shortest, the anterior chamber depth was most shallow, the pre-operative refractive error was worst and more hyperopic result than other groups. SRK/T formula show lesser mean error than using the SRK-II formula in all groups. All mean error in both formulas show hyperopic shift than predicted. The primary angle closure patients were statically significant difference more hyperopic shift than the normal open primary closure (p = 0.002275). The acute primary angle closure patients was statically significant less hyperopic shift than primary angle closure patients (p = 0.004408) but not statically significant different with normal open angle patients (p = 0.320347). The pre-operative axial length and anterior chamber depth are not related to inaccuracy of IOL power calculations.
Conclusion: IOL power prediction is more accurate when use SRK/T formula. All groups of patients have to choose the IOL power producing the myopic predicted post-operative refractive error. The primary angle closure patients have to choose the power that the predicted post-operative refractive error more myopic than acute primary angle closure and normal open angle patients. The pre-operative axial length and anterior chamber depth are not related to inaccuracy of IOL power calculations.

Keywords: Refractive outcome, Cataract surgery, Acute primary angle closure, Primary angle closure