Purpose
It is well known that the ocular straylight gradually increases with age in normal phakic eyes. A normal reference curve has been defined for phakic eyes. However, the crystalline lens replacement causes considerable change in straylight, which also modifies the steepness of its increase with age. The purpose of this study was to determine a pseudophakic norm for straylight as a new reference. In addition, the proposed model was tested for its predictability of the effect of lens replacement on straylight improvement.
Methods
A retrospective cross-study data analysis was performed to evaluate changes in intraocular scatter upon crystalline lens exchange. The postoperative results were used to define the norm for straylight in pseudophakia with simple linear regression. Linearity was assessed with a loess fit. The normative limits were obtained using quantile regression. The straylight improvement following lens replacement was assessed based on individual pre- and postoperative values. Orthogonal regression was used to determine the break-even point (BEP) with age affect.
Results
The pseudophakic norm was based on 1533 eyes from 13 studies. The new reference as well as the individual postoperative straylight values are presented in Figure 1A. The outcomes of loess fit and quantile regression are shown in Figures 1B and 1C respectively. The straylight improvement as a function of preoperative value is presented in Figure 2. The BEP increase with subject age is shown with the red line in Figure 1A.
Conclusions
We developed a norm for straylight in the pseudophakic eye that differs from the previously published norm for the phakic eye. The loess fit shows that the straylight-age dependency in pseudophakia is no longer logarithmic but linear. Moreover, the BEP values are very close to the reference line (Figure 1A). Therefore, the established reference might be considered as a predictive feature to improve the decision-making process before crystalline lens exchange.