Objective Cataract Grading Cut-Offs For Reestablishment Of The Far Distance Contrast Sensitivity After Multifocal Intraocular Lens Implantation

The implantation of a multifocal intraocular lens (MIOL) can result in the reduction of the far distance contrast sensitivity (CS) in comparison to the preoperative period. This could lead to some complaints, especially in refractive lens exchange on which the crystalline lens has not still developed cataracts. On the other hand, patients with cataracts can improve their distance CS in comparison to the preoperative period at some stages of the cataract development. The purpose of this study was to determine the cut-offs for age and objective grading methods of cataract classification for which the patient would perceive an improvement in CS instead of a decrease after MIOL implantation.

107 subjects were monocularly measured during the preoperative screening for cataract surgery with the HD Analyzer (Visiometrics), iTrace (Tracey), and Pentacam AXL Wave (Oculus), grading the cataract with the Ocular Scatter Index (OSI), Dysfunctional Lens Index (DLI) and Pentacam Nucleus Staging (PNS), respectively. The CS defocus curve was measured with the Multifocal Lens Analyzer (Qvision) from +1.00 to -4.00 D. A logistic regression was conducted to calculate the probability of obtaining a far distance CS of 0.8 logCS depending on age, OSI, DLI and PNS. This threshold value was selected considering the published CS defocus curve in previous studies with Liberty (Medicontur), AT Lisa Tri (Zeiss) and Versario3F (Valeant).

Both age and objective systems for grading cataracts were able to predict the CS equal or above 0.8 logCS, however OSI and age resulted in higher areas under the receiving operating curves (0.85 and 0.84) than DLI and PNS (0.74 and 0.63). The best model fit was obtained with the OSI (r-square = 0.48) and the poorest with the PNS (r-square = 0.08). The cut-offs that maximized the sensibility and specificity for predicting a CS ≥ 0.8 logCS according to the Youden index calculation were ≤ 62 for age, ≤1.25 for OSI, ≥7.67 for DLI and ≤1 for PNS.

Subjects younger than 62 with cataract gradings below to 1.25 for OSI and 1 for PNS, or above 7.76 for DLI, should be alerted in the preoperative period that the CS at far distance can be decreased in comparison to their current state before surgery if they are going to be implanted with MIOLs. Although the threshold was selected considering the published CS defocus curve with Liberty (Medicontur), AT Lisa Tri (Zeiss) and Versario3F (Valeant), results can be applicable to other MIOLs since less differences are usually found at far distance.