Assessment Of Positive Dysphotopsia For Various Monofocal Intraocular Lenses With Decentration And Tilt

There are several studies that assessed the effect of Intraocular Lens (IOL) decentration and tilt on the image quality. A few publications also compare the dysphotopsia or glare for
different Monofocal IOLs. However, there is no known published study that addresses the impact of decentration and tilt on dysphotopsia. The current study evaluates positive dysphotopsia or glare type photic phenomena for four marketed IOL models with decentration and tilt in a schematic model eye.

A non-sequential schematic model-based study at Alcon Research, LLC, Fort Worth, Texas, USA.

A non-sequential ray trace based schematic model eye was developed to assess dysphotopsia with decentration and tilt for four different Monofocal IOL models (Alcon Clareon
CNA0T0, JnJ Tecnis ZCB00, B&L enVista MX60, Hoya Vivinex XY1). Optical ray trace simulations of incoming light were generated based on a collimated light source with a wavelength of 550 nm for various off-axis angles (35-70 degrees) of illumination at a mesopic pupil size of 5 mm. The decentration values of 0.3 and 0.5 mm; and tilt angle of 3 and 5 degrees were used for the comparative study.

This analysis reveals two unwanted components of light that can be attributed to reflected and transmitted glare because of the IOL decentration and tilt. The CNA0T0 IOL
produced distinct focused image compared to all other IOL models. Both MX60 and XY1 IOLs produced on-axis focused image like CNA0T0, however, the transmitted glare is an order of magnitude higher as compared to CNA0T0. The ZCB00 and MX60 IOLs produced dispersed images at on-axis and increasing amount of glare characteristics starting at 35 degrees of off-axis illumination. 

The CNA0T0 IOL designs with full 6-mm functional optics and precision edge curvature demonstrated the lowest level or absence of glare with decentration and tilt at a
large mesopic pupil of 5 mm. Our results also demonstrated that dysphotopsia or glare type photic phenomenon can be higher for IOLs with reduced functional optic diameter, peripheral non-imaging optic geometry and straight edge profiles. Both reflected and transmitted unwanted light could be a source of potential dysphotopsia. The model eye-based assessment can only be confirmed with clinical studies.