Clinical Study Of Optical Quality After Implantation Of Aspheric Toric Intraocular Lens In Cataract Surgery

Objective Toric intraocular lens(IOL), known as intraocular lens with composite surface, is a new refractive IOL to correct astigmatism by cylindrical lens combined with spherical IOL. It could correct corneal regular astigmatism of cataract patients. With the introduction of aspheric platform on intraocular lens recently, the aspheric platform was also applied on toric intraocular lens to decrease spherical aberration to improve optical quality on the basis of correcting corneal astigmatism effectively. The research aim to evaluate the effect of aspheric toric intraocular lens on improving optical quality by comparing the contrast sensitivity, high order aberration and values of optical quality analysis system after implantation aspheric toric intraocular lens (Acrysof IQ Toric IOL) and spheric toric intraoculer lens.Methods1.one hundred and fourteen eyes of one hundred and two subjects with regular corneal astigmatism (range0.75D to3.OD) were enrolled from Tianjin Medical University Eye Hosptical. The mean preoperative corneal astigmatism was (1.62±0.63) D for all patients with a mean age of73.58years±6.72(SD)(range49to84years). Patients with glaucoma, keratitis, fundus diseases and undergoing ocular operation were excluded.50eyes of44patients with AcrySof IQ Toric IOL (SN6AT) implantation were used in the test group (aspheric group) and50eyes of45patients with AcrySof Toric IOL (SN60TT) implantation were used in the contral group (spheric group)2. Postoperative examinations were performed at1day,1week,1month and3months, including visual acuity, slitlamp evaluation and fundoscopy. The orientation of toric IOL axis was determined by slitlamp retro-illumination after pupillary dilation at1day postoperatively and other examinations including UDVA, CDVA, subjective refractions and IOL axis rotation were performed at3months postoperatively. 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 of3and5mm using iTrace aberrometer. Objective optical quality were measured using optical quality analysis system(OQAS), included MTFcutoff, OSI, Strehl ratio, OV100%, OV20%and OV9%.3. Statistical Analysis:All data were collected in an Excel database (Microsoft Office2003, Microsoft Corp.)-Data analysis was performed using SPSS for Windows (version13.0, SPSS Inc.). Normality of all data samples was first checked using the Kolmogorov-Smirnov test. When parametric analysis was possible, the Student t test for paired data was performed for all parameter comparisons. When parametric analysis was not possible, the Mann-Whitney U test was applied to assess the significant of differences. The counting data were compared with the chi-square test; the ranked data were compared with the Mann-Whitney U test, using in all cases the same level of significance (P<0.05).Results1. Postoperatively, the mean UDVA of aspheric and spheric group were0.19±0.11and0.21±0.11LogMAR respectively; the mean CDVA were0.08±0.09and0.10±0.10LogMAR respectively. The UDVA was20/40or better in92%of eyes in aspheric group and20/40or better in88%of eyes in spheric group. No statistically significant differences were noted between groups.2. The mean residual refractive cylinder were0.50±0.30D in aspheic group and0.59±0.32D in spheric group respectively. No statistically significant differences were noted between groups.3. The mean absolute misalignment were3.74±1.88degrees in aspheic group and3.84±1.68degrees in spheric group respectively. No statistically significant differences were noted between groups.4. Aspheric group performed better than spheric group under mesopic and mesopic glare conditions at moderate and high spatial frequency (P<0.05). There was no statistically significant in every spatial frequency under photopic condition between two groups. There was statistically significant in the spatial frequency of12cpd and18cpd under mesopic condition and in the spatial frequency of6cpd,12cpd and18cpd under mesopic with glare conditions.5. Mean ocular spherical aberration of aspheric group at3-mm pupil was significantly less than spheric group and mean total higher order aberrations and spherical aberration of aspheric group at5-mm pupil were significantly less than spheric group (P=0.0011,P<0.001and P<0.001, respectively).6. The mean MTFcutoff, OSI, Strehl ratio, OV100%, OV20%and OV9%of aspheric group were better than spheric group, but were not statistically significant (P>0.05).Conclusions1. Both aspheric and spheric toric IOL implantation were an effective and safe method to correct corneal astigmatism during cataract surgery and had excellent predictability and rotational stability, and high patient-satisfaction ratings.2. Aspheric toric IOL performed better optical quality than spheric toric IOL.3. Contrast sensitivity and glare sensitivity were sensitive to the description of visual function and had important significance for evaluating visual function of aspheric IOL implantation.4. iTrace wavefront aberrometry could provide wavefront aberrations rapidly and accurately and had important clinical significance for evaluating the effect of wavefront aberrations on the optical quality.5. Double-pass optical quality analysis system was useful for characterizing objectively and analyzing quantitatively optical quality and had important significance for the optical quality of Acrysof toric IOL implantation.