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EW RESIDENTS 110 March 2016 by Jessica Maslin, MD, Peter Ryg, MD, and Lucy Zhang, MD, Yale School of Medicine contrast sensitivity, or simulated glare testing, affecting activities of daily living, and no other possible cause for decreased vision found. 3 PCO is known to not only affect visual acuity, but also to affect var- ious other measurements of visual function such as contrast sensitivity and color vision. In addition, PCO can affect retinal image contrast, leading to significant glare and impairment of visual function even with excellent visual acuity. The loss of retinal image contrast, resulting in halos, glare at night, and other disruptions of visual function, is measured by intraocular straylight, a measurement of intraocular light scatter. Intraocular straylight can be measured by the C-Quant straylight meter (Oculus, Wetzlar, Germany), which directs light scatter into the eye and compares the resultant scattered light to a reference light P osterior capsular opaci- fication (PCO) is a com- mon complication of routine cataract surgery. PCO occurs due to the proliferation and migration of lens epithelial cells causing inflamma- tion and fibrosis of the capsular bag 1 and can affect postoperative vision. It has been estimated that visually significant PCO occurs in 20–40% of patients in the 2 to 5 years after cataract surgery. 2 The treatment for PCO in the central visual axis is neodymium:YAG (Nd:YAG) laser capsulotomy of the posterior lens capsule, which creates an opening in the central posterior lens capsule to provide a clear visual axis. Accord- ing to Medicare criteria, a patient with visually significant PCO that warrants a YAG capsulotomy should have a visual acuity of 20/30 or worse with Snellen conditions, controlled by the patient. The stray- light meter is a direct quantification of the amount of light scattering in the eye. It has been shown to be a reliable clinical test that is both repeatable and sensitive. 4,5 Yotsukura et al examined the effect of Nd:YAG capsulotomy on visual function in 16 patients with posterior capsular opacification after cataract surgery who complained of blurred vision despite having a visual acuity of 20/20 or better, using straylight measurements and correlating these measurements with wavefront aberrations. This obser- vational case series was performed at Keio University Hospital, Tokyo, and included patients with previous uneventful phacoemulsification who had postoperative visual symptoms of blur and/or glare with distance corrected visual acuity (DCVA) of 20/20 or better. The study exclud- ed patients with pathology of the macula or optic nerve, a history of intraocular inflammation, anterior capsular contraction, ocular surgery other than cataract removal, and implantation of a toric or multifo- cal IOL. The authors also excluded patients who had pitting of the IOL during capsulotomy. Measurements were taken prior to laser capsuloto- my and again 1 week after a stan- dard Nd:YAG capsulotomy of at least 3.0 mm with no anterior capsular contraction. Measurements taken included DCVA, 10% low contrast visual acuity (LCVA), total higher order wavefront aberrations (THOAs), and retinal straylight. THOAs represent the root mean square (RMS) from the third- to sixth-order Zernike co- efficients; the RMS of the third (S3) and fourth (S4) Zernike coefficients were used to represent coma-like and spherical-like aberrations, respectively. Retinal straylight was measured by a C-Quant straylight meter. In this study, retinal stray- light testing was repeated up to 3 times if the computer software in- dicated low reliability. If the results remained unreliable, the subject was excluded from the study. The authors reported that the mean CDVA improved significant- ly (P<0.05) as did LCVA, THOAs and S3, and straylight. Patients' subjective symptoms resolved after capsulotomy in all cases. Prior to capsulotomy, DCVA was correlated significantly with the LCVA and S3, but this correlation was not found after capsulotomy. Straylight also correlated positively with THOAs prior to capsulotomy, but not after- ward. The authors conclude that Nd:YAG laser capsulotomy may provide significant improvement of visual function even in patients with PCO and good visual acuity. They also postulate that straylight mea- surements may be a useful adjunct in determining an indication for Nd:YAG capsulotomy in symptomat- ic patients with 20/20 BCVA. In this study, the authors demonstrated a correlation be- tween Nd:YAG and improvement in measured DCVA, LCVA, THOAs, and straylight in patients who had a preintervention DCVA of 20/20 or better. They pointed out that in clinical practice, the indications for Nd:YAG capsulotomy generally are based on subjective symptoms, DCVA, and morphologic appearance of PCO. However, in patients who have a very early PCO and visual disturbance despite good visual acuity, only a few measurements such as contrast sensitivity and func- tional VA can attempt to quantify those symptoms. Straylight values improved significantly after capsu- lotomy in this study, which leads to the implication that straylight may be a useful method for deter- mining the indication for Nd:YAG treatment for PCO. The results also suggested that Nd:YAG capsulotomy is effective for patients with visual symptoms despite good VA. The authors reported that the correla- tions between straylight and S3 and THOAs were significant before but not after capsulotomy, which they suggest is probably due to all values being restored to a normal range in most cases. One of the strengths of this study is that the authors examined a very specific group of patients, namely the ones who had symptom- atic PCO with excellent visual acuity of 20/20 or better. The question that the authors strive to address in this study is one that many clinicians face in the real world, a scenario in which patients come in complaining of blurred vision, halos, and glare after cataract extraction, yet there is no change in the measured visual acuity. When does the Review of "Effect of Nd:YAG laser capsulotomy in patients with posterior capsule opacification Effect of Nd:YAG laser capsulotomy on visual function in patients with posterior capsule opacification and good visual acuity Erisa Yotsukura, MD, Hidemasa Torii, MD, Megumi Saiki, MS, Kazuno Negishi, MD, Kazuo Tsubota, MD J Cataract Refract Surg (March) 2016;42. Article in press Purpose: To evaluate the effect of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser capsulotomy on visual function in patients with posterior capsule opacification (PCO) and good visual acuity. Setting: Keio University Hospital, Tokyo, Japan. Design: Observational case series. Methods: Eyes were evaluated that had undergone a previous cataract surgery with a clinical diagnosis of posterior capsule opacity requiring Nd:YAG laser capsulotomy regardless of a good corrected distance visual acuity (CDVA) of at least 20/20. The CDVA, 10% low contrast visual acuity (LCVA), wavefront aberrations from the third to sixth order, and retinal straylight were measured before and after Nd:YAG laser capsulotomy. Results: The study included 16 eyes of 16 patients (10 men, 6 women; mean age, 69.5±9.3 years). The mean CDVA, LCVA, and straylight after Nd:YAG laser capsulotomy improved significantly (P<0.05). The root mean square (RMS) of the third Zernike coefficients (S3) and the RMS of the total higher order aberrations from the third to sixth order (THOAs) decreased significantly (P<0.05) after capsulotomy. The straylight was correlated significantly with the THOAs (r=0.727, P=0.002), S3 (r=0.748, P=0.001) before capsulotomy. The subjective symptoms resolved after capsulotomy in all cases. Conclusions: Nd:YAG laser capsulotomy enables a significant improvement of visual function even in patients with PCO with good VA. The straylight measurements may be useful to determine the indications for Nd:YAG laser capsulotomy when patients complain of visual disturbances without decreased VA. EyeWorld journal club

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