Ayaka Iijima, Kimiya Shimizu, Mayumi Yamagishi, Hidenaga Kobashi, Akihito Igarashi and Kazutaka Kamiya

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1 Assessment of subjective intraocular forward scattering and quality of vision after posterior chamber phakic intraocular lens with a central hole (Hole ICL) implantation Ayaka Iijima, Kimiya Shimizu, Mayumi Yamagishi, Hidenaga Kobashi, Akihito Igarashi and Kazutaka Kamiya Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan ABSTRACT. Purpose: To evaluate the subjective intraocular forward scattering and quality of vision after posterior chamber phakic intraocular lens with a central hole (Hole ICL, STAAR Surgical) implantation. Methods: We prospectively examined 29 eyes of 29 consecutive patients (15 men and 14 women; ages, years) undergoing Hole ICL implantation. We assessed the values of the logarithmic straylight value [log (s)] using a straylight meter (C-Quant TM, Oculus) preoperatively and 3 months postoperatively. The patients completed a questionnaire detailing symptoms on a quantitative grading scale (National Eye Institute Refractive Error Quality of Life Instrument-42; NEI RQL-42) 3 months postoperatively. We compared the preoperative and postoperative values of the log(s) and evaluated the correlation of these values with patient subjective symptoms. Results: The mean log(s) was not significantly changed, from preoperatively, to postoperatively (Wilcoxon signed-rank test, p = 0.641). There was a significant correlation between the preoperative and postoperative log(s) (Spearman s correlation coefficient r = 0.695, p < 0.001). The postoperative log(s) was significantly associated with the scores of glare in the questionnaire (Spearman s correlation coefficient r = 0.575, p = 0.017). Conclusions: According to our experience, Hole ICL implantation does not induce a significant additional change in the subjective intraocular forward scattering. The symptom of glare after Hole ICL implantation was significantly correlated with the postoperative intraocular forward scattering in relation to the preoperative one. Key words: C-Quant Hole ICL ICL intraocular forward scattering subjective forward scattering Acta Ophthalmol. 2016: 94: e716 e720 ª 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd doi: /aos Introduction The Visian Implantable Collamer Lens (ICL, STAAR Surgical, Nidau, Switzerland), a posterior chamber phakic intraocular lens (IOL), has been reported to have a long-term beneficial effect on the correction of moderate to high ametropia (Sanders et al. 2004; Kamiya et al. 2009; Alfonso et al. 2011; Igarashi et al. 2014). A new ICL with a central artificial hole (Hole ICL) has been developed to rectify disadvantages of conventional ICL such as cataract formation and necessity for laser iridotomies (Fujisawa et al. 2007; Shiratani et al. 2008; Uozato et al. 2011; Kawamorita et al. 2012). The presence of the central artificial hole does not require additional laser iridotomies or peripheral iridectomy and may also reduce the risk of cataract formation. We previously demonstrated that Hole ICL offered good results for all measures of safety, efficacy, predictability and stability (Shimizu et al. 2012a,b) and that Hole ICL implantation was essentially equivalent in the induction of higher-order aberrations (HOAs) and in contrast sensitivity function to conventional ICL implantation (Shimizu et al. 2012a,b). As intraocular forward scattering can lead to image quality degradation on the retina, resulting in the deterioration of visual performance, this measurement could provide valuable insights into visual function, especially after phakic IOL implantation. It has been demonstrated that the intraocular forward scattering of conventional ICL-implanted eyes was equivalent to that of healthy eyes and Hole ICL-implanted eyes (Kamiya et al. 2012a,b, 2013). The straylight meter (C-Quant, Oculus, Optikger ate, GmbH, Wetzlar, Germany), which psychometrically assesses the intraocue716

2 lar forward scattering based on the compensation method, has been reported to be helpful for the subjective assessment of the forward scattering (Franssen et al. 2006), and to provide good repeatability and reproducibility of the measurements (Cervi~no et al. 2008; Guber et al. 2011; Iijima et al. 2015), in a clinical setting. As far as we can ascertain, there has been no detailed studies so far on the subjective forward scattering after Hole ICL implantation. The purpose of the current study is twofold to prospectively quantify the subjective forward scattering after Hole ICL implantation and to evaluate the relationship of the forward scattering with the subjective symptoms such as glare. Patients and Methods Study population A total of 29 eyes of 29 patients (15 men and 14 women), who underwent implantation of the posterior chamber phakic IOL with a central hole (Hole ICL, KS-APTM, STAAR Surgical) for the correction of moderate to high myopia and myopic astigmatism, were included in this prospective study. The patients were recruited in a continuous cohort. Only one eye per subject was randomly selected for statistical analysis. The patient age at the time of surgery was years (mean age standard deviation (SD); range, years). Any history of concomitant eye disease or eye surgery, corrected visual acuity lower than 20/20, amblyopia or any systemic diseases, was excluded from the study. Eyes with keratoconus were also excluded from the study using the keratoconus screening test of Placido disk videokeratography (TMS-2; Tomey, Nagoya, Japan). The study was approved by the Institutional Review Board at Kitasato University School of Medicine and followed the tenets of the Declaration of Helsinki. Informed consent was obtained from all patients after explanation of the nature and possible consequences of the study. Hole implantable collamer lens power calculation Hole ICL power calculations were performed by the manufacturer (STAAR Surgical) based on a modified vertex formula. Toric Hole ICL power calculation was also performed based on the astigmatism decomposition method. The size of the ICL also was chosen by the manufacturer based on the horizontal corneal diameter and anterior chamber depth measured with scanning-slit topography (Orbscan IIz; Bausch & Lomb, Rochester, NY, USA). Hole implantable collamer lens surgical procedure The surgical procedures of Hole ICL implantation were as follows (Shimizu et al. 2012a,b; Kamiya et al. 2013): on the day of surgery, the patients were administered dilating and cycloplegic agents. After topical anaesthesia, a model V4 ICL was inserted through a 3-mm temporal clear corneal incision with the use of an injector cartridge (STAAR Surgical) after placement of a viscosurgical device (Opegan; Santen, Osaka, Japan) into the anterior chamber. After the ICL was located in the posterior chamber, the viscosurgical device was fully washed out of the anterior chamber with balanced salt solution, and a miotic agent was instilled. The patients did not undergo any preoperative laser iridotomies or intraoperative peripheral iridectomy. Postoperatively, steroidal (0.1% betamethasone; Rinderon; Shionogi, Osaka, Japan) and antibiotic (0.3% levofloxacin; Cravit; Santen, Osaka, Japan) medications were administered topically 4 times daily for 2 weeks, the dose being reduced gradually thereafter. Measurement of subjective intraocular forward scattering We measured the subjective intraocular forward scattering of the eye using the C-Quant straylight meter (Oculus Optikger ate, GmbH, Wetzlar, Germany) preoperatively and 3 months postoperatively. This device uses the compensation comparison method which comprises a psychometric function designed to describe the (stochastic) characteristics of the responses, as described previously (Franssen et al. 2006). The centre of the test field is divided into half. Outside the centre is a ring-shaped flickering light source, which serves as the straylight source. While compensation light is presented in one-half of the centre test field, no compensation light is presented in the other. As a result, two flickers are perceived that differ in modulation depth: one result from straylight only, the other is a combination of straylight and compensation light. The subjects are queried to select which semicircle is flickering more strongly, and they press the button on the left or the right side of the device. The straylight meter will change the luminance of the stimulus and counter-phase modulating light automatically until the two halves are balanced. To obtain the straylight value, this process is repeated with different levels of compensation light, resulting in a logarithmic straylight value, which is abbreviated as log(s). We accepted the measurements only when the estimated standard deviation was lower than 0.08, and when the quality factor was higher than 1.00 (Coppens et al. 2006). All log(s) measurements were performed without glasses or contact lenses, while the other eye was covered. We used cleaned trial glasses if necessary. Questionnaire of vision-related quality of life Vision-related quality of life was determined (with no correction) using a National Eye Institute Refractive Error Quality of Life Instrument-42 (NEI RQL-42) as a questionnaire detailing symptoms on a quantitative grading scale (Hays et al. 2003; McDonnell et al. 2003; Nichols et al. 2003). We used the adapted Japanese version of the NEI RQL-42 in all patients undergoing Hole ICL implantation 3 months postoperatively, as described previously (Kobashi et al. 2014). In brief, this 42-item instrument has 13 scales covering specific aspects of quality of life as follows: clarity of vision, expectations, near vision, far vision, diurnal fluctuations, activity limitations, glare, symptoms, dependence on correction, worry, suboptimal correction, appearance and satisfaction with correction. Each scale has a score from 0 to 100. A higher score implies a higher selfreported quality of life. Statistical analysis All statistical analyses were performed using a commercially available statistical software (Ekuseru-Toukei 2015, Social Survey Research Information e717

3 Co, Ltd., Tokyo, Japan). The normality of all data samples was first checked by the Kolmogorov Smirnov test. As the data did not fulfil the criteria for normal distribution, the Wilcoxon signed-rank test was used to compare the pre- and postsurgical data, and the relationship between two sets of data was analysed by Spearman s rank correlation test. The results are expressed as mean SD, and a p-value <0.05 was considered statistically significant. Results Table 1 shows the preoperative and postoperative demographic data of the study population. All surgical procedures were uneventful, and no postoperative complications such as cataract formation, pigment dispersion syndrome, pupillary block or axis rotation were seen throughout the 3-month observation period. No eyes were lost during the 3-month follow-up in this series. The mean log(s) was not significantly changed, from preoperatively, to months postoperatively (Wilcoxon signed-rank test, p = 0.641). We found a significant correlation between the preoperative and postoperative log(s) values (Spearman s correlation coefficient r = 0.695, p < 0.001). Figures 1 and 2 show Bland Altman plots of the preoperative and postoperative log(s) and these log(s) as a function of age, respectively. Table 2 shows the NEI RQL-42 scale scores and their relationships with the postoperative log(s). The postoperative log(s) was significantly associated with the scores of glare (Spearman s correlation coefficient r = 0.575, p = 0.017), but not with other scores (p > 0.05) in the questionnaire. Discussion In the present study, our results showed no significant difference between the preoperative and postoperative log(s) values in Hole ICL-implanted eyes. It is indicated that Hole ICL implantation itself does not induce a significant additional change in the subjective intraocular forward scattering of eyes. Until now, there have been only a few studies on the quantitative measurements of the central peak of the point spread function (PSF), as an objective index of intraocular forward scattering in ICL-implanted eyes using the Optical Quality Analysis System (OQAS, Visiometrics, Terassa, Spain) (Kamiya et al. 2012a,b, 2013; Kurian et al. 2012). The C-Quant used in the current study is the straylight meter which psychometrically assesses the intraocular forward scattering based on the compensation method (Franssen et al. 2006), and thus, it is essentially different from the OQAS as the PSF meter, based on the double-pass method (G uell et al. 2004). The OQAS aims to assess the central peak of the PSF, whereas the log(s) assesses the outer area of the PSF. The C-Quant may more accurately reflect the subjective symptoms, such as glare and halo, of the patients than the OQAS, because this measurement directly provides the subjective data of intraocular scatter- Table 1. Demographic data of the study population undergoing Hole implantable collamer lens (ICL) implantation. Demographic data Age (years) years (range, 20 to 54 years) Gender (% female) 48.0% Preoperative Manifest spherical equivalent (D) D (range, 1.25 to D) Manifest cylinder (D) D (range, 0.00 to 4.50 D) LogMAR UDVA (range, 2.00 to 0.30) LogMAR CDVA (range, 0.15 to 0.30) Axial length (mm) mm (range, to mm) Mean keratometry (D) D (range, to 45.75D) Log(s) (range, 0.73 to 1.47) Postoperative (3 months) Manifest spherical equivalent (D) D (range, 0.00 to 2.00 D) Manifest cylinder (D) D (range, 0.00 to 1.50 D) LogMAR UDVA (range, 0.52 to 0.30) LogMAR CDVA (range, 0.00 to 0.30) Mean keratometry (D) D (range, to 45.75D) Log(s) (range, 0.73 to 1.45) D = dioptre, logmar = logarithm of the minimal angle of resolution, UDVA = uncorrected distance visual acuity, CDVA = corrected distance visual acuity. Fig. 1. Bland Altman plots representing the difference of the preoperative and postoperative log(s) divided by the mean of the preoperative and postoperative log(s). The middle line represents the mean difference. The upper and lower lines represent the upper and lower borders of the 95% limits of agreements. e718

4 Fig. 2. A scatterplot showing the preoperative and postoperative log(s) as a function of age. ing. We previously showed a modestly significant correlation between the values of the log(s) and the OSI in healthy subjects, indicating that the subjective forward scattering may be reflected, to some extent, by the objective one, but that the subjective scattering does not necessarily coincide with the objective one in a clinical setting (Iijima et al. 2015). The mean value of log(s) of preoperative normal eyes in this study was slightly higher than that of log(s) of normal eyes in our previous study (Iijima et al. 2015) ( versus ), possibly resulting from the differences of age ( years versus years) and refraction ( D versus D). As far as we can ascertain, this is the first published study to assess the subjective forward scattering after Hole ICL implantation. It has been reported that the objective intraocular scattering of conventional ICL-implanted eyes was essentially equivalent to those of healthy eyes (Kamiya et al. 2012a) and Hole ICL-implanted eyes (Kamiya et al. 2013). Therefore, coupled with our current and previous findings, the intraocular forward scattering of eyes Table 2. The National Eye Institute Refractive Error Quality of Life Instrument-42 (NEI RQL-42) scale scores and its correlation with the log(s) 3 months after Hole implantable collamer lens (ICL) implantation. Scale Score (Mean SD) Correlation with the log(s) r p value Clarity of vision Expectations Near vision Far vision Diurnal fluctuations Activity limitations Glare Symptoms Dependence on correction Worry Suboptimal correction Appearance Satisfaction with correction SD = standard deviation, log(s) = log(straylight), r = Spearman s correlation coefficient. undergoing Hole ICL implantation may be subjectively and objectively equivalent to those of healthy eyes. With regard to the straylight after refractive surgery, the mean straylight was increased after radial keratotomy (Veraart et al. 1992), but was not significantly increased after photorefractive keratectomy or laser in situ keratomileusis (Beerthuizen et al. 2007; Patel et al. 2007; Lapid-Gortzak et al. 2010; Lorente-Velazquez et al. 2010; Cervino et al. 2011; Li & Wang 2011). On the other hand, the straylight showed a significant reduction (Paarlberg et al. 2011), or showed no significant change (Landesz et al. 1995), after iris-supported phakic IOL implantation. The latter findings of irissupported phakic IOL implantation were in agreement with our findings of Hole ICL implantation. We also found a significant correlation between the postoperative log(s) and the score of glare in the NEI RQL-42 questionnaire after Hole ICL implantation. It has been demonstrated that binocular photopic contrast sensitivity with and without glare at 12 and 18 cycles/degree was significantly correlated with several NEI RQL-42 scales and that low mesopic contrast sensitivity without glare at three cycles/degree was significantly correlated with the indices for near vision, far vision, glare, dependence on correction, suboptimal correction and satisfaction with correction in phakic refractive lens-implanted eyes (Perez-Cambrodı et al. 2013). It has been also demonstrated that the scale for glare was not significantly associated with the postoperative magnitude of ocular HOAs in these eyes. These findings suggest that the intraocular scattering might play a major role in this disturbance after ICL implantation. It has been shown that Hole ICL implantation was essentially equivalent in the induction of HOAs and contrast sensitivity function to conventional ICL implantation (Shimizu et al. 2012a,b). To our knowledge, this is also the first study to assess the relationship of subjective symptoms such as glare with the subjective forward scattering after Hole ICL implantation. In the present study, there was a significant correlation between the preoperative and postoperative log(s) values, suggesting that the postoperative intraocular forward scattering may be considerably reflected by the e719

5 preoperative one. It has been shown that the OSI, as an objective measure of intraocular scattering, was significantly associated with age (Kamiya et al. 2012a,b), and with the degree of myopia (Miao et al. 2014), in healthy subjects. We should be aware that the postoperative subjective symptoms such as glare are more likely to appear in eyes with higher patient age and higher myopia. There are several limitation to this study. Firstly, the sample size was relatively small in the current study, although the sample size in this study offered 80% statistical power at the 5% level. Secondly, we did not confirm the repeatability of the log(s) measurements in eyes undergoing Hole ICL implantation. However, the straylight meter provides good repeatability and reproducibility of the measurements in healthy subjects (Cervi~no et al. 2008; Guber et al. 2011; Iijima et al. 2015). A further study is necessary to confirm the repeatability of the measurements even in Hole ICL-implanted eyes. Thirdly, we performed the log(s) measurements at 3 months postoperatively. A long-term follow-up is required to confirm our short-term findings. In conclusion, our results support the view that the subjective intraocular forward scattering of eyes remained unchanged after Hole ICL implantation, suggesting that the ICL with an artificial hole itself does not induce a significant additional change in the subjective forward scattering of the eye. In addition, the postoperative forward scattering was significantly associated with the subjective symptom of glare, indicating that the intraocular forward scattering plays a key role in the symptom of glare in Hole ICL-implanted eyes. References Alfonso JF, Baamonde B, Fernandez-Vega L, Fernandes P, Gonzalez-Meijome JM & Montes-Mico R (2011): Posterior chamber collagen copolymer phakic intraocular lenses to correct myopia: five-year follow-up. J Cataract Refract Surg 37: Beerthuizen JJG, Franssen L, Landesz M & van den Berg TJTP (2007): Straylight values 1 month after laser in situ keratomileusis and photorefractive keratectomy. J Cataract Refract Surg 33: Cervino A, Villa-Collar C, Gonzalez-Meijome JM, Ferrer-Blasco T & Garcia-Lazaro S (2011): Retinal straylight and light distortion phenomena in normal and post-lasik eyes. Graefes Arch Clin Exp Ophthalmol 249: Cervi~no A, Montes-Mico R & Hosking SL (2008): Performance of the compensation comparison method for retinal straylight measurement: effect of patient s age on repeatability. Br J Ophthalmol 92: Coppens JE, Franssen L & van den Berg TJ (2006): Reliability of the compensation comparison method for measuring retinal stray light studied using Monte- Carlo simulations. J Biomed Opt 11: Franssen L, Coppens JE & van DBT (2006): Compensation comparison method for assessment of retinal straylight. Invest Ophthalmol Vis Sci 47: Fujisawa K, Shimizu K, Uga S, Suzuki M, Nagano K, Murakami Y & Goseki H (2007): Changes in the crystalline lens resulting from insertion of a phakic IOL (ICL) into the porcine eye. Graefes Arch Clin Exp Ophthalmol 245: Guber I, Bachmann LM, Guber J, Bochmann F, Lange AP & Thiel MA (2011): Reproducibility of straylight measurement by C-Quant for assessment of retinal straylight using the compensation comparison method. Graefes Arch Clin Exp Ophthalmol 249: G uell JL, Pujol J, Arjona M, Diaz-Douton F & Artal P (2004): Optical Quality Analysis System; Instrument for objective clinical evaluation of ocular optical quality. J Cataract Refract Surg 30: Hays RD, Mangione CM, Ellwein L, Lindblad AS, Spritzer KL & McDonnell PJ; For the NEI-RQL Research Group (2003): Psychometric properties of the National Eye Institute-Refractive Error Quality of Life instrument. Ophthalmology 110: Igarashi A, Shimizu K & Kamiya K (2014): Eight-year follow-up of posterior chamber phakic intraocular lens implantation for moderate to high myopia. Am J Ophthalmol 157: Iijima A, Shimizu K, Kobashi H, Saito A & Kamiya K (2015): Repeatability, reproducibility, and comparability of subjective and objective measurements of intraocular forward scattering in healthy subjects. Biomed Res Int 2015: Kamiya K, Shimizu K, Igarashi A & Komatsu M (2009): Four-year follow-up of posterior chamber phakic intraocular lens implantation for moderate to high myopia. Arch Ophthalmol 127: Kamiya K, Shimizu K, Igarashi A, Kobashi H, Ishii R & Sato N (2012a): Clinical evaluation of optical quality and intraocular scattering after posterior chamber phakic intraocular lens implantation. Invest Ophthalmol Vis Sci 53: Kamiya K, Umeda K, Kobashi H, Shimizu K, Kawamorita T & Uozato H (2012b): Effect of aging on optical quality and intraocular scattering using the double-pass instrument. Curr Eye Res 37: Kamiya K, Shimizu K, Saito A, Igarashi A & Kobashi H (2013): Comparison of optical quality and intraocular scattering after posterior chamber phakic intraocular lens with and without a central hole (Hole ICL and Conventional ICL) implantation using the double-pass instrument. PLoS ONE 8: e Kawamorita T, Uozato H & Shimizu K (2012): Fluid dynamics simulation of aqueous humour in a posterior-chamber phakic intraocular lens with a central perforation. Graefes Arch Clin Exp Ophthalmol 250: Kobashi H, Kamiya K, Igarashi A, Matsumura K, Komatsu M & Shimizu K (2014): Long-term quality of life after posterior chamber phakic intraocular lens implantation and after wavefront-guided laser in situ keratomileusis for myopia. J Cataract Refract Surg 40: Kurian M, Nagappa S, Bhagali R, Shetty R & Shetty BK (2012): Visual quality after posterior chamber phakic intraocular lens implantation in keratoconus. J Cataract Refract Surg 38: Landesz M, Worst JG, Siertsema JV & van Rij G (1995): Correction of high myopia with the Worst myopia claw intraocular lens. J Refract Surg 11: Lapid-Gortzak R, van der Linden JW, van der Meulen I, Nieuwendaal CP, Mourits MP & van den Berg TJ (2010): Straylight before and after hyperopic laser in situ keratomileusis or laser-assisted subepithelial keratectomy. J Cataract Refract Surg 36: Li J & Wang Y (2011): Characteristics of straylight in normal young myopia and changes before and after LASIK. Invest Ophthalmol Vis Sci 52: Lorente-Velazquez A, Nieto-Bona A, Collar CV & Gutierrez Ortega AR (2010): Intraocular straylight and contrast sensitivity (1/2) and 6 months after laser in situ keratomileusis. Eye Contact Lens 36: McDonnell PJ, Mangione C, Lee P, Lindblad AS, Spritzer KL, Berry S & Hays RD; For the NEI- RQL Research Group (2003): Responsiveness of the National Eye Institute Refractive Error Quality of Life instrument to surgical correction of refractive error. Ophthalmology 110: Miao H, Tian M, He L, Zhao J, Mo X & Zhou X (2014): Objective optical quality and intraocular scattering in myopic adults. Invest Ophthalmol Vis Sci 55: Nichols JJ, Mitchell GL, Saracino M & Zadik F (2003): Reliability and validity of refractive error-specific quality-of-life instruments. Arch Ophthalmol 121: Paarlberg JC, Doors M, Webers CA, Berendschot TT, van den Berg TJ & Nuijts RM (2011): The effect of irisfixated foldable phakic intraocular lenses on retinal straylight. Am J Ophthalmol 152: Patel SV, Maguire LJ, McLaren JW, Hodge DO & Bourne WM (2007): Femtosecond laser versus mechanical microkeratome for LASIK: a randomized controlled study. Ophthalmology 114: Perez-Cambrodı RJ, Blanes-Mompo FJ, Garcıa-Lazaro S, Pi~nero DP, Cervi~no A & Brautaset R (2013): Visual and optical performance and quality of life after implantation of posterior chamber phakic intraocular lens. Graefes Arch Clin Exp Ophthalmol 251: Sanders DR, Doney K & Poco M; ICL in Treatment of Myopia Study Group (2004): United States Food and Drug Administration clinical trial of the Implantable Collamer Lens (ICL) for moderate to high myopia: three-year follow-up. Ophthalmology 111: Shimizu K, Kamiya K, Igarashi A & Shiratani T (2012a): Early clinical outcomes of implantation of posterior chamber phakic intraocular lens with a central hole (Hole ICL) for moderate to high myopia. Br J Ophthalmol 96: Shimizu K, Kamiya K, Igarashi A & Shiratani T (2012b): Intraindividual comparison of visual performance after posterior chamber phakic intraocular lens with and withouta centralholeimplantationformoderatetohigh myopia. Am J Ophthalmol 154: Shiratani T, Shimizu K, Fujisawa K, Uga S, Nagano K & Murakami Y (2008): Crystalline lens changes in porcine eyes with implanted phakic IOL (ICL) with a central hole. Graefes Arch Clin Exp Ophthalmol 246: Uozato H, Shimizu K, Kawamorita T & Ohmoto F (2011): Modulation transfer function of intraocular collamer lens with a central artificial hole. Graefes Arch Clin Exp Ophthalmol 249: Veraart HG, van den Berg TJ, IJspeert JK & Cardozo OL (1992): Stray light in radial keratotomy and the influence of pupil size and straylight angle. Am J Ophthalmol 114: Received on January 15th, Accepted on March 17th, Correspondence: Kazutaka Kamiya, MD, PhD Department of Ophthalmology University of Kitasato School of Medicine Kitasato, Sagamihara Kanagawa Japan Tel: Fax: kamiyak-tky@umin.ac.jp Dr. Shimizu is a consultant of STAAR Surgical who has assisted with the development of patented technologies. No other author has a financial or proprietary interest in any material or method mentioned. e720