Objective: To compare the optical quality after two different types (aspheric and spheric) of toric intraocular lens implantation.
Methods: The study was a prospective study. One hundred eyes of 89 patients with regular corneal astigmatism (range 1.00 D to 3.00 D) underwent implantation of toric intraocular lens in the Tianjin Medical University Eye Hospital from May 2012 to June 2013, including 50 eyes of 44 patients implanted Acrysof IQ Toric IOL (SN6AT) (aspheric group) and 50 eyes of 45 patients implanted Acrysof Toric IOL (SN60TT) (spheric group). Mean age was 73.7 years±6.6 and mean astigmatism was 1.68±0.51D. Main outcomes of two groups evaluated at 3-months of follow-up, included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual refractive cylinder and IOL rotation. Contrast sensitivity testing was performed under photopic, mesopic and mesopic with glare conditions using the CSV-1000E charts. Ocular higher order aberrations, including total higher order aberrations and spherical aberration, were measured at optical zone of 3.0 and 5.0 mm using iTrace aberrometer. Objective optical quality was measured using optical quality analysis system (OQAS), included MTF cutoff, OSI, Strehl ratio, OV100%, OV20% and OV9%. The Student t test was performed for data with normal distribution. The Mann-Whitney U test was performed for data with no normal distribution.
Results: Postoperatively, the mean UDVA of aspheric and spheric group were 0.19±0.11 and 0.21±0.11 LogMAR respectively; the mean CDVA were 0.08±0.09 and 0.10±0.10 LogMAR respectively; the mean residual refractive cylinder were 0.50±0.30D and 0.59±0.32D respectively; the mean absolute misalignment were 3.74±1.88 degrees and 3.84±1.68 degrees respectively. No statistically significant differences were noted between groups in mean UDVA, CDVA, residual refractive cylinder and absolute misalignment (U=1135.50, P=0.414; U=1118.52, P=0.342; U=1035, P=0.128 and t=0.28, P=0.780, respectively). Aspheric group performed better than spheric group under mesopic and mesopic glare conditions at moderate and high spatial frequency. Mean ocular spherical aberration of aspheric group at 3.0 mm pupil was significantly less than spheric group and mean total higher order aberrations and spherical aberration of aspheric group at 5.0 mm pupil were less than spheric group (t=3.49, P=0.003; t=6.46, P<0.001 and U=0.00, P<0.001, respectively). The mean MTFcutoff of aspheric and spheric group were (23.207±5.409) cpd and (25.01±5.46) cpd, the mean OSI were 1.69±0.7 and 1.65±0.77, the mean Strehl ratio were 0.14±0.04 and 0.16±0.04, the mean OV100% were 0.77±0.18 and 0.83±0.18, the mean OV20% were 0.77±0.18 and 0.79±0.21, and the mean OV9% were 0.75±0.20 and 0.78±0.17. No statistically significant differences were noted between groups in mean MTFcutoff, OSI, Strehl ratio, OV100%, OV20% and OV9% (t=0.26, P=0.795; t=1.66, P=0.100; t=1.92, P=0.057; t=1.72, P=0.089; t=0.39, P=0.693 and t=0.98, P=0.328, respectively).
Conclusions: Both aspheric and spheric toric IOL implantation were an effective and safe method to correct corneal astigmatism during cataract surgery. Moreover, aspheric toric IOL performed better optical quality than spheric toric IOL.