Forward light scatter measurement provides information about optical imperfections as the cause of glare disability. Glare disability refers to a reduction in visual performance caused by a glare source, resulting in retinal contrast loss secondary to intraocular stray light.1 Lens extraction reverses the strong age increase in stray light, which is considered an independent source of symptoms.2 Stray light is 1 possible source of unwanted visual phenomena related to patients with implanted multifocal intraocular lenses (IOLs). Recent studies reported little difference in retinal stray light between patients with monofocal IOLs and patients with multifocal IOLs.3 Pupil miosis during retinal stray light measurement and neural adaptation after multifocal IOL implantation may overcome possible differences. However, the best way to analyze the change in visual and optical quality of the eye is to measure before and after a surgical procedure. For multifocal IOLs, measurements should be done in refractive lens exchange (RLE) cases. A recent report concluded that higher-order aberration (HOA) levels are similar before and after RLE with multifocal IOL implantation.4 Then, if patients refer to any visual phenomenon, this may come from the scatter created by multifocality of the IOL; measurements of retinal stray light should be done before and after RLE to corroborate this point. We describe a patient who had symptomatic glare disability despite visual acuity of 20/20 after uncomplicated RLE.
A 54-year-old woman underwent RLE surgery with the AcrySof ReSTOR Natural IOL (SN60D3) implant (Alcon Laboratories, Inc, Fort Worth, Texas) to correct ametropia and presbyopia. Three months after surgery, the patient experienced glare disability under monocular and binocular conditions. Preoperative and postoperative refractions were +3.00 − 1.00 × 90° and +0.50, respectively, in the right eye and +2.50 − 0.50 × 85° and +0.25, respectively, in the left eye. Low-order (defocus and astigmatism) and higher-order (coma-like and spherical-like) aberrations were measured with the LADARWave aberrometer (Alcon Laboratories, Inc) for 3.0- and 5.0-mm pupils. The root mean square of HOAs (excluding defocus and astigmatism) were similar before and after the surgery: in the right eye, 0.049 μm and 0.052 μm, respectively, for the 3-mm pupil and 0.311 μm and 0.299 μm, respectively, for the 5-mm pupil; in the left eye, 0.043 μm and 0.058 μm, respectively, for the 3-mm pupil and 0.287 μm and 0.291 μm, respectively, for the 5-mm pupil. Retinal stray light was measured with the C-Quant stray light meter (Oculus Optikgeräte GmbH, Wetzlar, Germany).2,3,5 In this case, the difference in retinal stray light before and after RLE was considerable: in the right eye, 0.82 log(s) and 1.41 log(s), respectively; in the left eye, 0.87 log(s) and 1.38 log(s), respectively (s indicates the stray light parameter). Best-corrected distance visual acuity was also measured, being 20/20 OU before and after surgery for distance and near vision.
Recent designs of multifocal IOLs effectively improve visual acuity at distance and near vision. However, they can adversely affect visual function owing to the superimposed retinal images on the retina. Theoretical predictions suggest that multifocal IOLs would induce more scatter than monofocal IOLs. The increase of light scatter in our patient was not associated with postoperative reductions in visual acuity or increases in HOA values as both visual acuity and HOA values were similar to those found before the surgery. In comparison, stray light increased more than 3-fold in each eye after surgery (by 3.9 OD and 3.2 OS). The disproportionate effect of light scatter relative to visual acuity and HOA likely reflects differences in scale. Light scatter varies with the wavelength of light measured in micrometers. Visual acuity reflects focal distances measured in millimeters; HOAs are determined by Hartmann-Shack sensors, which are spaced 100 μm apart. The results of this case show that perceived effects of retinal stray light are substantially higher after multifocal IOL implantation, and this may be the cause of glare disability reported by the patient. However, this conclusion cannot be extended to intermediate or near distances, which are still within the operational range of the multifocal lens but not the native lens of this 54-year-old patient. Although the multifocal lens provides a range of fixed focal lengths, the trade-off is increased light scatter and reduced contrast sensitivity at each focal length owing to overlap of multiple defocused images. Measurement of visual acuity under suprathreshold contrast conditions may underestimate the effect of RLE on visual function. Surgeons should be careful with RLE in case an eye has low stray light values. Stray light is an independent source of symptoms, and it should be measured clinically independently from visual acuity–associated symptoms.
Correspondence: Dr Montés-Micó, Optics Department, Faculty of Physics, University of Valencia, C/Dr Moliner 50, 46100 Burjassot, Valencia, Spain (firstname.lastname@example.org).
Financial Disclosure: None reported.
Funding/Support: This work was supported in part by Universitat de Valencia Research Grant UV-AE-20070225 (Dr Montés-Micó) and by Ministerio de Ciencia e Innovación grant SAF2008-01114-E from Red Temática de Optometríia.
Van Den Berg
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