Residual Refractive Errors Following Cataract Surgery and its Determinants

To evaluate residual refractive errors after cataract surgery and its determinant factors at Farabi Eye Hospital, Tehran. Simple random sampling was done among cataract surgery scheduled patients over a 4 year period (2003-2006). Exclusion criteria were uveitis, previous intraocular surgery and ocular trauma. After applying the exclusion criteria, 423 patients were studied. Lens calculation was performed using the SRK-II formula. Unexpected refractive errors were defined as the difference between postoperative refractive errors with target refraction. Mean and percentage of this variable were reported based on 0.5, 1 and 2 D of ametropia. Of 558 studied patients, 78.1% had biometric data before and refractive data after surgery. Mean absolute unpredictable refractive error was 0.84±0.89 D. Eyes with normal axial length (AL) had the least (0.76±0.84) and those with long AL had the most unpredictable refractive errors (P<0.001). 45.9%, 73.9%, and 91.7% of the study cases had refractive errors within 0.5, 1 and 2 D of emmetropia, respectively. Eyes with short AL had positive refraction and those with long AL had negative refraction after surgery. The majority of keratometric astigmatism followed extra-capsular surgery while the least measures were associated with phacoemulsification (P<0.001). Axial length was one of the important factors influencing residual refractive errors after cataract surgery. Unpredictable refractive errors were more common in eyes with long and short AL than those with normal AL.