Eyeworld

EW RESIDENTS 52 May 2014 by Seanna Grob, MD, MAS, Katherine Talcott, MD, Aristomenis Thanos, MD, and Yewlin Chee, MD, Harvard Medical School ophthalmology residents Review of "Straylight before and after in eyes with preoperative visual acuity main. 3 Computerized straylight me- ters, such as the C-Quant straylight meter (Oculus, Germany), determine the amount of intraocular forward scattered light and have shown reliable and repeatable results for untrained subjects over a range of straylight values. 4,5 Other studies have reported straylight to be an effective addition to preoperative cataract evaluation in predicting whether a patient would benefit from cataract surgery. 4,6 We appreci- ate the efforts of Dr. Lapid-Gortzak and her associates in evaluating the effects of straylight on visual function in early cataracts and its potential benefits for clinical use in cataract evaluation. Study summary The study is a prospective case co- hort that evaluated 160 consecutive eyes from 89 patients who under- went cataract surgery (96 eyes) or refractive lens exchange (64 eyes) with intraocular implantation of monofocal or multifocal lenses at a private refractive clinic. Inclusion criteria included preoperative best corrected visual acuity of 0.1 log- MAR or better. Exclusion criteria included other anterior segment disease (such as corneal opacities or endothelial dysfunction), previous refractive surgery, glaucoma, trau- matic eye disease, or retinal pathol- ogy. A full ophthalmic exam was performed pre- and postoperatively, with particular attention paid to outcome measures of uncorrected distance visual acuity (UDVA), cor- rected distance visual acuity (CDVA), refractive error, and straylight meas- urements. Straylight was measured using the C-Quant straylight meter, where the patient performed a forced choice task of the strongest of 2 flickering half-fields; each eye was measured twice before surgery and twice 3 months after surgery, where averages (expressed as logs) were computed on a psychometric response curve. After cataract surgery or refrac- tive lens exchange, mean UDVA improved 0.38 logMAR (from 0.42 preoperatively to 0.04 postopera- tively) and CDVA improved 0.02 logMAR (from 0.02 to 0.0). Mean preoperative spherical equivalent refraction decreased from +1.01 D (range –8.88 D to +10.13 D) to 0.02 D (range –1.38 D to +1.5 D) postop- eratively. All eyes taken together, there was statistically significant improvement of straylight with surgery, comparable to 1 line on the reading chart, from mean preopera- tive log 1.21 to postoperative log 1.11 (Pearson correlation coefficient of 0.67, p<0.0005). Patients with low preoperative CDVA (44 eyes with CDVA >0.1 logMAR) were noted to have a greater improvement of stray- light after surgery (>0.2 log or 2 lines of improvement on reading chart). Additionally, patients with clinically diagnosed cataracts were more likely to have straylight improvement of >0.2 log (34 of 96 eyes; 35.4%) after surgery than those in the refractive lens exchange group (10 of 64 eyes; 15.6%). Comment This important study continues the significant work of the authors in investigating the contribution of oc- ular straylight in the dysphotopsias experienced by patients before and/ or after cataract and refractive sur- gery procedures. Ocular straylight, or disability glare as previously de- fined, is a growing field of interest in cataract and refractive surgery. This is reflected by the recent introduc- tion of several devices to the market that allow testing and, more impor- tantly, quantification of straylight and glare. While the normal healthy eye has a baseline level of straylight, it has been found that increasing levels of straylight are correlated with cataracts. 4 Technology to meas- ure straylight becomes particularly important in patients with cataracts who complain of significant visual disability from glare, despite main- taining an excellent corrected visual acuity. The results of this study fur- ther support the emerging evidence that straylight and visual acuity measure different aspects of vision quality, and suggest that the meas- urement of straylight can aid in appropriate patient selection for cataract surgery. The inclusion of additional elements to this study would strengthen the results. First, the cornea is a major contributor to optical aberrations of the eye, and a comparison of pre- and postopera- tive topography and/or aberrometry would have been useful in order to conclude that the changes seen in ocular straylight are solely due to EyeWorld journal club Carolyn Kloek, MD, residency program director, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston We all recognize that Snellen acuity does not capture much of the functional disability associated with earlier levels of cataract. This month, I have invited the Mass Eye and Ear residents to review this paper on straylight measurements in cataract patients from the May issue of JCRS. –David F. Chang, MD, chief medical editor Introduction A key component of ophthalmology residency is mastering the evalua- tion and care of patients with cataracts. We are trained to consider a combination of a patient's visual Straylight before and after phacoemulsification in eyes with preoperative corrected distance visual acuity better than 0.1 logMAR Ruth Lapid-Gortzak, MD, PhD, Ivanka J.E van der Meulen, MD, PhD, Jan Willem van der Linden, BOpt, Maarten P. Mourits, MD, PhD, Thomas J.T.P van den Berg, PhD J Cataract Refract Surg (May) 2014; 40:748–755 Purpose: To report the outcomes of changes in straylight before and after phacoemulsification in eyes with preoperative corrected distance visual acuity (CDVA) better than 0.1 logMAR. Setting: Private refractive surgery clinic, Driebergen, the Netherlands. Design: Cohort study. Methods: Standard phacoemulsification with implantation of a monofocal or multifocal intraocular lens (IOL) was performed. Preoperative and 3-month postoperative straylight values, CDVA, and refractive error were compared. Results: The study enrolled 160 eyes (89 patients). The mean CDVA was 0.02±0.05 logMAR (range −0.1 to 0.1 logMAR) preoperatively and 0.00±0.04 logMAR (range −0.1 to 0.2 logMAR) postoperatively. The mean preoperative straylight was 1.21±0.20 log(s) (range 0.80 to 1.74 log[s]) and 1.11±1.16 log(s) (range 0.76 to 1.63 log[s]), respectively; the improvement was statistically significant. There was a correlation between high preoperative straylight values and postoperative improvement in straylight values. Conclusions: In eyes with relatively good CDVA of 0.1 logMAR or better (decimal 0.8 or better; Snellen 20/25 or better), straylight improved by 0.10 log(s) after cataract surgery. A subgroup of 44 eyes had an improvement of more than 0.20 log(s), which is comparable to a 2-line improvement on the vision chart. symptoms, objective measure of acuity, appearance of the cataract on exam, and the potential visual outcome after cataract extraction in determining whether a patient is a candidate for cataract surgery. How- ever, patients often report visual symptoms of cataracts before a sig- nificant decline is noted on visual acuity testing. 1 Since excellent visual acuity is achievable with cataract surgery, there has been an increasing interest in alternative objective measurements of visual function in the assessment of patients with early cataracts. This manuscript analyzes the use of measurements of stray- light on visual function in eyes with preoperative visual acuity better than 0.1 logMAR. Straylight is abnormal light scatter caused by imperfect optical media that results in loss of retinal image contrast, also known as dis- ability glare. 2,3 It is an objective physiologic measure of the large- angle domain of the retinal point- spread function; in contrast, visual acuity assesses the small-angle do-

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