Actual Refractive Error Research Articles

Accuracy of Intraocular Lens Power Estimation in Aphakic Eyes Filled with Silicone Oil

Purpose: To compare preoperative refractive power estimation and actual postoperative refraction after combined silicone oil removal and intraocular lens (IOL) sulcus implantation in silicone oil-filled aphakic eyes.Methods: Records of patients with silicone oil-filled aphakic eyes who received simultaneous silicone oil-removal and IOL sulcus implantation (Group1) and aphakic patients who received vitrectomy combined with IOL implantation (Group 2) were reviewed. Optical biometry including axial length measurements were obtained using IOL master<sup>®</sup> 700 and predicted refractive errors, actual postoperative refractive errors were examined retrospectively.Results: Predicted refractive errors, calculated by subtracting 1 diopter (D) from myopic lens power closest to plano based on sulcus implantation, were 0.50 ± 0.12 D in Group 1, 0.45 ± 0.20 D in Group 2. Six months after operation, mean refractive errors measured -0.76 ± 0.49 D in Group 1, -0.23 ± 0.49 D in Group 2, showing significant myopic shift (<i>p</i> < 0.001, <i>p</i> <0.001). Group 1 showed larger significant myopic shift compared to Group 2 (<i>p</i> = 0.001), especially in 3 eyes with insufficient filling of intravitreal silicone oil showing -1.5 D myopic shift.Conclusions: Ocular biometry of silicone oil-filled aphakic eyes undergoing simultaneous silicone oil removal and IOL sulcus implantation are difficult to measure, showing postoperative myopic shift compared to control. Incomplete intravitreal silicone oil filling showed larger refractive errors needing additional compensations.

Expected vs. Actual Refractive Error in Patients Presenting With Phacomorphic Glaucoma.

AimPhacomorphic glaucoma (PG) is a rare but clinically significant presentation requiring emergent cataract surgery. We chose to investigate whether the expected refractive error based on the intraocular lens (IOL) calculations differed from the expected refractive outcome post-surgery.Materials & MethodsA retrospective analysis of patients with PG between 2009 to 2018 who underwent cataract surgery and had postoperative refraction was included. Information collected included presenting and postoperative best-corrected visual acuity (BCVA), intraocular pressure (IOP) pre­ and postoperatively, and the presence of corneal edema. Predicted spherical equivalence (SphEq) data was collected from IOL calculations, and postoperative SphEq was calculated from postoperative manifest refraction.ResultsTwenty patients with PG who underwent cataract surgery were identified; of these, 10 patients and 10 eyes who underwent manifest refraction post­op were included. Mean BCVA at presentation was 20/544 [Logarithm of Minimal Angle of Resolution (LogMAR) 1.44], and mean pre-op IOP was elevated at 24.6 ± 14.2 mmHg. Mean BCVA measured at one month post-op improved to 20/192 (LogMAR 0.983). Mean IOP decreased to 19 ± 8.8 mmHg at one month post-op. The mean difference between the predicted and actual refractive error, as calculated by SphEq was ­0.088 (p=0.570).ConclusionThe study shows an improvement in visual acuity and IOP post-cataract surgery in patients with PG, as would be expected. The study also demonstrates that patients ended up with a slightly more myopic refractive error than expected postoperatively, and illustrates the clinical variability in postoperative refractive outcomes from a large standard deviation. This is a new and clinically important finding, although not statistically significant, that has not been previously published.

Refractive outcomes after vitrectomy combined with phacoemulsification of idiopathic macular holes.

To report the refractive outcomes after vitrectomy combined with phacoemulsification and intraocular lens (IOL) implantation (phaco-vitrectomy) in idiopathic macular holes (IMH). A total of 56 eyes with IMH (IMH group) that underwent phaco-vitrectomy and 44 eyes with age-related cataract (ARC group) that underwent cataract surgery were retrospectively reviewed. The best corrective visual acuity (BCVA), predicted refractive error (PRE), actual refractive error (ARE), axial length (AL), were measured in both groups before and 6mo after operation. The power calculation of IOL and the predicted refractive error (PRE) were calculated according to the SRK/T formula. The difference of PRE and ARE between the two groups were compared and analyzed. In the IMH group, the diameters of macular holes were 271.73±75.85 µm, the closure rate was 100%. The pre- and post-operative BCVA were 0.80±0.35 and 0.40±0.35 logMAR. The PRE of A-ultrasound and IOL Master in the IMH group was -0.27±0.25 and 0.10±0.66 D. The postoperative mean absolute prediction error (MAE) was observed to be 0.58±0.65 and 0.53±0.37 D in the IOL Master and A-ultrasound (P=0.758). The PRE and ARE of the IMH group were 0.10±0.66 D and -0.19±0.64 D (P=0.102). The PRE and ARE of the ARC group was -0.43±0.95 and -0.31±0.93 D (P=0.383). The difference between PRE and ARE was -0.33±0.81 and 0.09±0.64 D in the IMH and ARC groups (P=0.021). The proportion of myopic shift was 67.9% in the IMH group and 27.3% in the ARC group (P=0.004). The myopic shift can be observed in patients with IMH after phaco-vitrectomy.

Lenstar LS 900 versus Pentacam-AXL: analysis of refractive outcomes and predicted refraction

Analysis of refractive outcomes, using biometry data collected with a new biometer (Pentacam-AXL, OCULUS, Germany) and a reference biometer (Lenstar LS 900, HAAG-STREIT AG, Switzerland), in order to assess differences in the predicted and actual refraction using different formulas. Prospective, institutional study, in which intraocular lens (IOL) calculation was performed using the Haigis, SRK/T and Hoffer Q formulas with the two systems in patients undergoing cataract surgery between November 2016 and August 2017. Four to 6 weeks after surgery, the spherical equivalent (SE) was derived from objective refraction. Mean prediction error (PE), mean absolute error (MAE) and the median absolute error (MedAE) were calculated. The percentage of eyes within ± 0.25, ± 0.50, ± 1.00, and ± 2.00 D of MAE was determined. 104 eyes from 76 patients, 35 males (46.1%), underwent uneventful phacoemulsification with IOL implantation. Mean SE after surgery was − 0.29 ± 0.46 D. Mean prediction error (PE) using the SRK/T, Haigis and Hoffer Q formulas with the Lenstar was significantly different (p > 0.0001) from PE calculated with the Pentacam in all three formulas. Percentage of eyes within ± 0.25 D MAE were larger with the Lenstar device, using all three formulas. The difference between the actual refractive error and the predicted refractive error is consistently lower when using Lenstar. The Pentacam-AXL user should be alert to the critical necessity of constant optimization in order to obtain optimal refractive results.

Preoperative measurement vs intraoperative aberrometry for the selection of intraocular lens sphere power in normal eyes.

PurposeThis study aimed to assess the value of intraoperative aberrometry (IA) in determining the intraocular lens (IOL) sphere power in eyes with no previous ocular surgery.Patients and methodsWe conducted a retrospective review of patients who underwent uncomplicated cataract surgery where standard preoperative (Preop) measurements and IA were performed. Calculated IOL sphere powers and postoperative refractions, both actual and theoretical, were compared based on the measurement method and lens type; lens types included multifocal, toric and aspheric single-vision non-toric IOLs.ResultsA total of 160 eyes of 112 patients were analyzed. The Preop lens power calculated was the same as the IA lens power 46% of the time, though this percentage was lower for multifocal IOLs. Across all lens types, there was a statistically significant bias (chi-square test, P<0.01) toward the IA method suggesting a lower powered lens. Actual postoperative refractive errors were not statistically significantly different when categorized by measurement method. Calculated errors by measurement method showed no statistically significant differences in expected outcomes. There were 63 cases where the Preop calculation and the intraoperative aberrometer calculation differed by 0.5 D. In 56% (35/63) of these cases, the IA result was a better option, and in 44% (28/63) of cases, the Preop calculation was better; this was not statistically significantly different from random expectation (50/50, P=0.53). In the three cases where calculated powers differed by 1.5 D, there appeared to be a positive effect of adjusting the Preop power toward the IA power.ConclusionThe use of IA for the determination of sphere power in eyes with no previous ocular surgery does not appear to improve overall expected clinical outcomes, but it may be helpful in cases where the difference between IA and Preop calculations is high.

The Effect Of Pupil Dilation On Biometric Parameters Of The Aladdin Optical Biometry

Purpose: To evaluate the effect of pupil dilation on biometric parameters of the Aladdin optical biometry and compare the accuracy IOL power calculation according to pupil dilation and difference in anterior chamber depth. Methods: This prospective cross-sectional study included 51 eyes of 42 patients who underwent uneventful phacoemulsification with IOL implantation. Preoperative IOL power calculations were performed using Aladdin optical biometer. Postoperative actual refractive errors and errors predicted by the SRK/T formula in eyes with non-dilated and dilated pupils were analyzed. The mean estimation error (EE), mean absolute estimation error (AEE) and the percentage of eyes within ±0.50 and ±1.00 D of target refraction for each of two groups were calculated and compared. (Group 1: eyes with nondilated pupil, Group 2: eyes with dilated pupil). Results: Smaller mean AEE and EE was provided in non-dilated group, however there was no statistically significant difference between two groups (p=0.12 and p=..... respectively). In non-dilated group, higher percentage of eyes within ±0.50 and ±1.00 D of target refraction was also found (62% and 98%), when compared with dilated group (54% and 94%). Conclusions: Based on the Aladdin biometric data used in our study, although better results was obtained when biometric measurements had been done in eyes with non-dilated pupil, there was no statistically significant difference.

Factors affecting refractive outcome after cataract surgery in primary angle-closure glaucoma.

To evaluate the biometric factors associated with the accuracy of intraocular lens power predictions for cataract surgery in primary angle-closure (PAC) or primary angle-closure glaucoma (PACG) eyes. Cross-sectional study PARTICIPANTS: This study included 103 PAC or PACG patients who had undergone cataract surgery. All participants underwent anterior-segment optical coherence tomography preoperatively. Two novel biometric factors - the relative lens vault (the ratio of lens vault to anterior vault) and the anterior vault (the sum of lens vault and anterior chamber depth) - were measured using customized software. The powers of the implanted intraocular lens and the actual postoperative refractive errors were compared. The mean refractive error and the median absolute error were calculated and compared using repeated measures ANOVA and Wilcoxon matched-pairs signed-rank test. The biometric factors associated with the postoperative refractive error were investigated by multivariate regression analysis. Preoperative anterior-segment biometric factors, difference between predicted and actual postoperative refraction. The Haigis, Hoffer Q and SRK/T formulas all showed a slight tendency toward resultant hyperopia, respectively (P < 0.001, P = 0.05, P = 0.003). The Hoffer Q formula had the least prediction error (P < 0.001). In the multivariate regression analysis, the relative lens vault was the only independent factor predicting postoperative refractive error (β = 0.392, P = 0.011). Intraocular lens power predictions for cataract surgery in PAC or PACG patients can be inaccurate. Such results might be associated with anterior-segment biometric factors. Preoperative relative lens vault appears to be a significant factor predicting refractive outcome after cataract surgery in patients with PAC or PACG.

Comparison of different formulas for intraocular lens power calculation using a new optical biometer

To evaluate and compare the predictability of different formulas for intraocular lens (IOL) power calculation using a new optical biometer (Aladdin). This prospective cross-sectional study included 70 eyes of 70 patients who underwent uneventful phacoemulsification with IOL implantation. Preoperative IOL power calculations were performed using the Aladdin optical biometer. Postoperative actual refractive errors and errors predicted by the SRK/T, SRK II, Holladay 1, Hoffer Q and Haigis formulas were analyzed. The mean estimation error (EE), mean absolute estimation error (AEE) and the percentage of eyes within ± 0.50 and ± 1.00 D of the target refraction for each of five formulas were calculated and compared. This analysis was also repeated in three groups formed based on axial length (AL) (group 1: <22.5mm, group 2: 22.5-24 mm, group 3: >24 mm). In the overall study group, the smallest mean AEE was provided by the Holladay 1 formula, however there was no statistically significant difference in the mean AEE's predicted by the five formulas (P=0.34). The highest percentage of eyes within ± 0.50 and ± 1.00 D of the target refraction was also found by using Holladay 1 (71% and 97%). SRK/T provided smallest mean AEE for groups 1 (n=13) and 3 (n=16). In group 2 (n=41), the smallest mean AEE was obtained using Holladay 1. Based on the Aladdin biometric data used in our study, better results can be obtained using SRK/T formula in eyes with short or long AL. The Holladay 1 formula may be preferred in eyes with moderate AL.

Postoperative Refractive Errors after Posterior Capsulectomy during Combined Vitrectomy and Cataract Surgery

Purpose: To evaluate the difference between the predicted and actual postoperative refractions after combined vitrectomy and cataract surgeries with a posterior capsulectomy. Methods: We performed a retrospective study of 33 eyes of 33 patients who underwent combined vitrectomy and cataract surgeries in our hospital between March 2013 and May 2014. The patients were divided into 2 groups: those who underwent a posterior capsulectomy (group A) and those who underwent combined vitrectomy and cataract surgeries (group B). The actual refractive errors were analyzed 3 months after surgery using spherical equivalent. We compared the results between the predicted and actual refractive errors in the two groups. Results: Group A consisted of 25 eyes of 25 patients and group B of 8 eyes of 8 patients. In group A, the average difference between predicted and actual postoperative refractive errors was -0.16 ± 0.38 D (p = 0.083). The predicted refraction was -0.33 ± 0.46 D and actual refraction was -0.49 ± 0.55 D in group A. There was no statistically significant difference between the predicted refraction and actual refractive errors in group A (p = 0.083). In group B, the average difference between predicted and actual postoperative refractive errors was 0.27 ± 0.29 D (p = 0.078). Additionally, the predicted refraction was -0.49 ± 0.77 D and actual refraction was -0.22 ± 0.59 D. The difference between the predicted refraction and actual refractive errors in group B was not statistically significant (p = 0.078). Conclusions: When a posterior capsulectomy is performed during combined vitrectomy and cataract surgery, no significant difference in refractive errors between the predicted refraction and actual refractive errors was observed 3 months after surgery. Compared with combined vitrectomy and cataract surgeries only, a small amount of myopic refractive change tended to occur 3 months after surgery. J Korean Ophthalmol Soc 2015;56(5):709-714

Postoperative Refractive Errors after Phacovitrectomy with Sulcus Fixation of an Intraocular Lens

Purpose: To evaluate the difference between the predicted postoperative refraction and the actual postoperative refraction after simultaneous vitrectomy and cataract surgery with sulcus fixation of an intraocular lens (IOL). Methods: The records of patients with simultaneous vitrectomy and cataract surgery with sulcus IOL implantation (group 1) and with in-the-bag IOL implantation (group 2) were reviewed. We compared the spread between the predicted and actual refractive errors in the two groups. Results: Group 1 consisted of 19 eyes in 19 patients and group 2 consisted of 23 eyes in 20 patients. The spread between the predicted and actual refraction (spread = actual-predicted) was -0.71 ± 1.02 D in group 1 (p = 0.012) and -0.07 ± 0.74 D in the group 2 (p = 0.86). The actual refractive errors in group 1 shifted toward myopia from the predicted in-the-bag refraction when compared with group 2. Conclusions: For the implantation of an IOL in the sulcus after simultaneous vitrectomy and cataract surgery, the IOL power should be approximately 1.0 D less than the power for in-the-bag fixation. J Korean Ophthalmol Soc 2014;55(4):513-518

Adaptation to astigmatic blur.

Adapting to blurred or sharpened images alters the perceived focus of subsequently viewed images. We examined whether these adaptation effects could arise from actual sphero-cylindrical refractive errors, by testing aftereffects in images simulating second-order astigmatism. Image blur was varied from negative (vertical) through isotropic to positive (horizontal) astigmatism while maintaining constant blur strength. A 2AFC staircase was used to estimate the stimulus that appeared isotropically blurred before or after adapting to images with astigmatism. Adaptation to horizontal blur caused isotropically blurred images to appear vertically biased and vice versa, shifting the perceived isotropic point toward the adapting level. Aftereffects were similar for different types of images and showed partial selectivity so that strongest effects generally occurred when testing and adapting images were the same. Further experiments explored whether the adaptation depended more strongly on the blurring or "fuzziness" in the images vs. the apparent "figural" changes introduced by the blur, by comparing how the aftereffects transfer across changes in size or orientation. Our results suggest that strong selective adaptation can occur for different lower order aberrations of the eye and that these may be at least partly driven by the apparent figural changes that blurring introduces into the retinal image.

Intraocular Lens Power Selection in the Second Eye of Patients Undergoing Bilateral, Sequential Cataract Extraction

To determine if the 1-month postoperative error of predicted refraction of the first eye can be used to alter intraocular lens (IOL) power selection and improve refractive results for the second eye in patients undergoing bilateral, sequential phacoemulsification with IOL implantation (phaco/IOL). Retrospective, consecutive, case series. Three hundred consecutive patients who underwent uncomplicated bilateral, sequential phaco/IOL between January 1, 2006, and December 31, 2007, by a single surgeon using a single IOL platform. The observed second eye 1-month postoperative spherical equivalent refractive error was compared with calculations of the hypothetic 1-month postoperative spherical equivalent refractive error if the first eye error had been fully or partially incorporated into the choice of IOL power for the second eye. The optimal amount of partial adjustment was determined. The error of predicted refraction: the difference between the actual or hypothetic spherical equivalent refractive errors and those predicted by preoperative calculations. A total of 206 patients met inclusion criteria. The average of the absolute value of the unadjusted second eye error (|E(UNADJ)|) was +0.44 diopters (D) compared with +0.42 D for the fully adjusted second eye error (|E(FULL)|). The optimal amount of adjustment of the second eye IOL power was determined to be 50%; the average of the absolute value of this partially adjusted second eye error (|E(PARTIAL,50%)|) was +0.36 D; this was statistically different from |E(UNADJ)| (P<0.0001) and |E(FULL)| (P = 0.001). The statistically significant benefit was observed for patients with either myopic or hyperopic errors in the first eye. The percentages of patients achieving postoperative refractions within 0.5 D and 1.0 D of the predicted refraction were 66.5% and 90.3%, respectively, for the unadjusted second eye, 67.0% and 90.8%, respectively, for the hypothetic fully adjusted second eye, and 74.3% and 93.7%, respectively, for the hypothetic partially adjusted (50%) second eye. Accounting for 50% of the observed error of predicted refraction of the first eye reduced the error of predicted refraction in the second eye. This novel methodology has the potential to improve the refractive outcomes in the second eye of patients with cataract. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Clinical Results of a Corneal Radius Correcting Factor in Calculating Intraocular Lens Power After Corneal Refractive Surgery

To describe the clinical results of a corneal radius correcting factor (CRCF), which is based on the axial length and independent of knowledge from the previous surgical procedure, in calculating intraocular lens (IOL) power in eyes that developed cataract after corneal refractive surgery. Intraocular lens power for 62 eyes that previously underwent corneal refractive surgery was calculated with the SRK/T and SRK II formulas using an axial length-related CRCF, and the expected refractive errors were compared with the actual postoperative refractive errors. Using the CRCF, the refractive outcomes ranged between -3.25 and +1.00 diopters (D) (mean -0.41+/-0.75 D), with 37 (60%) eyes within +/-0.50 D and 53 (85%) eyes within +/-1.00 D of the intended refraction. Using the raw data, without the correcting factor, the refractive outcomes would have ranged between -2.00 and +5.00 D (mean +2.17+/-1.45 D) with 7 (11%) eyes within +/-0.50 D and 15 (24%) eyes within +/- 1.00 D of the intended refraction. Pending further validation through a larger prospective evaluation, the CRCF combined with the SRK/T formula is recommended in eyes with an axial length up to 30 mm and the average IOL power calculated with the SRK/T and SRK II formulas when the axial length is >30 mm.

Biometric calculation of intraocular lens power for cataract surgery following pupil dilatation

The ability to perform biometry accurately on a dilated pupil can greatly facilitate the efficiency of a cataract service as it can be done on the day of surgery. The purpose of this study was to assess the repeatability of axial length (AL) calculations in undilated pupils and measure the difference in predicted and actual refractive outcomes in dilated pupils compared with undilated pupils. First, intraobserver repeatability was assessed by taking two consecutive recordings of AL using applanation A-scan ultrasonography in undilated pupils in 21 eyes. The mean AL for each eye was compared with a measurement made following pupil dilatation. Second, we audited the mean spherical equivalent refractive errors following routine cataract surgery in 38 patients with undilated pupils and 36 patients with dilated pupils. The mean difference in intraobserver measurements was -0.05 mm (standard deviation [SD] 0.15) with pupils undilated. Following pupil dilatation, the mean dilated AL differed from the mean undilated AL reading by only 0.03 mm (P > 0.05). The mean differences between planned and actual refractive error were 0.71D (SD 0.54) and 0.55D (SD 0.41) in dilated and undilated patients, respectively. This was not statistically significant (P > 0.05). The range of differences between target and actual refraction was -1.45D to 2.70D for undilated patients and -1.88D to 1.18D in dilated patients. Although there was a greater spread of postoperative refractive errors in the dilated group, there were no statistically or clinically significant differences in postoperative refractive errors between the two categories of patients. Our study shows that applanation biometry may be safely performed for the purpose of cataract surgery after pupil dilatation.

Prediction of Refractive Error in Combined Vitrectomy and Cataract Surgery With One-Piece Acrylic Intraocular Lens

PurposeTo compare the predicted and actual refractive errors of hydrophilic, one-piece, C-flex®570C (C-flex) intraocular lens (IOL) implantation in simultaneous vitrectomy and lens extraction in various conditions.MethodsOne hundred fifty-nine eyes of patients who had lens extraction between March 2004 and September 2005 were enrolled in a retrospective study. Group 1 had lens extraction and IOL implantation, and Group 2 had lens extraction and IOL implantation with vitrectomy. IOL calculation was done with axial length and keratometry measurements. The actual and predicted refractive errors were compared at 1 and 6 months postoperatively. The factors influencing the postoperative refractive outcomes were analyzed.ResultsThe mean refractive predictive error (i.e., the actual minus predicted spherical equivalent) was +0.19±0.39 D (Diopter) and -0.26±0.45 D at 1 and 6 months postoperatively (all: p<0.001) in group 1, and -0.22±0.39 D and -0.06±0.62 D at 1 and 6 months postoperatively (p=0.013, p=0.399 respectively). In group 2, all surgical factors related to refractive errors were not statistically significant (all: p>0.05).ConclusionsRefractive errors in combined surgery showed myopic shift of -0.50 D and -0.32 D at 1 and 6 months postoperatively compared with C-flex IOL implantation alone. With the hyperopic tendency of IOL and myopic tendency of vitrectomy, the combined surgery made postoperative refractive errors near emmetropia.

Postoperative Refractive Error of Secondary Intraocular Lens Implantation After Simultaneous Vitrectomy and Lensectomy

To determine postoperative refractive errors of secondary intraocular lens (IOL) implantation, this study was performed in 42 eyes of 42 patients following secondary IOL implantation fixed in the sulcus after simultaneous vitrectomy and phacoemulsification and aspiration. Controls were 138 eyes of 124 patients with cataract who underwent phacoemulsification and aspiration and IOL implantation. The spread between expected and actual refraction (actual - expected) was -0.81 +/- 0.86 diopters (average +/- standard deviation) in the study group and 0.01 +/- 0.91 diopters in the control group (statistically significant, P < .001, Student's t test). The actual refractive errors in the study subjects were shifted toward myopia compared with the controls.

VALIDATION OF ICNIRP ESTIMATES OF TOXICITY THRESHOLDS FOR NIR (785 NM) LIGHT IN THE RETINAS OF PIGMENTED RABBITS

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) established eye-safe exposure limits for laser light based on estimates of the 50% exposure dose (ED50) for retinal damage in animals. The ED50 has not been determined for continuous-wave near-infrared (NIR) light, as may be used in instruments for spectroscopic analysis of the eye. The purpose of this study is to determine the ED50 of 785-nm light delivered by a Raman spectroscopy instrument on the retinas of pigmented rabbits, and to compare that ED50 to the ICNIRP estimates. Light of varying power was focused into the anterior chambers of rabbits for 4, 20, or 300 s. Estimates of spot size on the retina were determined by modifying the schematic rabbit eye with actual axial length and refractive error measurements. Masked examiners determined retinal burns from fundus photographs and fluorescein angiograms made immediately after exposure and again 48-72 h later. Thirty-five of 86 exposed eyes had retinal burns. In 12 of these the burn was not visible until 48-72 h. In 6 the burn was visible on color photographs, but not on fluorescein angiography. The ED50 retinal power density from probit analysis was 14,513 mW cm(-2), 10,369 mW cm(-2), and 5,237 mW cm(-2) for 4-s, 20-s, and 300-s exposures, respectively. Thus, the ED50 for retinal burns from 785-nm light is approximately 7 and 7.5 times the ICNIRP permitted limits for 4- and 20-s exposures, and 5.6 times the limit for 300-s exposures. This is consistent with the ICNIRP intention to set power limits several times less than ED50.

Myopic astigmatism and presbyopia trial

PurposeNo prospective double-masked study has evaluated whether low astigmatism benefits or harms patients with presbyopia, whose intermediate and near vision might theoretically benefit from enhanced depth of focus provided by astigmatism. The purpose of the first Myopic Astigmatism and Presbyopia (MAP I) study was to determine whether low myopic astigmatism enhances or harms the visual acuity, stereopsis, or quality of life in patients with presbyopia. DesignProspective, randomized, double-masked, crossover design clinical trial. MethodsFifteen patients with presbyopia aged 45 to 68 years were recruited from an academic center population. These patients were given a baseline eye examination, including manifest refraction, Early Treatment of Diabetic Retinopathy Study (ETDRS) logarithm of minimal angle of resolution (logMAR) visual acuity at distance, intermediate, and near, accommodative amplitudes, and stereo vision. Each patient was then cycled in random order through three masked pairs of soft contact lenses. The power of each contact lens pair was calculated by the subtraction method to maintain a spherical equivalent of −0.5 diopters, while providing either no astigmatism (spherical arm, SPH), 1 diopter of with-the-rule (WTR) astigmatism, or 1 diopter of against-the-rule (ATR) astigmatism. Actual refractive errors produced were measured by masked examiner. Outcomes measured at the end of 1 week of usage of each contact lens arm were binocular (ETDRS) logMAR visual acuity at three distances (far [4 m], intermediate [1 m], and near [33cm]); near stereoacuity, using the quantitative Titmus Stereotest; and quality of life, measured using the Refractive Status and Vision Profile (RSVP), a standardized questionnaire. ResultsVisual acuity results across the three arms were similar. However, 1-m logMAR visual acuity was better for the spherical arm than either astigmatic arm (−0.06 SPH, +0.01 WTR, +0.02 ATR). Near (33 cm) and distance (4 m) acuities were similar across arms. Stereoacuity was better in ATR than WTR (50 vs 102 seconds, P = .01). Subjects preferred SPH slightly over the WTR astigmatic arm by the RSVP quality-of-life survey instrument (101 vs 104, P = .05). Other intergroup comparisons showed no difference in RSVP scores. ConclusionsThis study has demonstrated that intermediate distance acuity and refractive quality of life are slightly better with spherical low myopic refractive error vs either astigmatic arm. Near and far distance acuity were unaffected by low myopic astigmatism compared with spherical low myopia. Near stereopsis was best in the ATR arms, but this did not produce better near visual acuity or RSVP quality of life.

Phacoemulsification and Intraocular Lens Implantation Combined with Trabeculotomy for Open-Angle Glaucoma and Coexisting Cataract

Objective: To study the outcome of phacoemulsification and intraocular lens implantation combined with trabeculotomy. Methods: We performed trabeculotomy combined with phacoemulsification and foldable lens implantation in 25 eyes with open-angle glaucoma and coexisting cataract in 18 patients. The series comprised 9 males (13 eyes) and 9 females (12 eyes). Mean age of the patients was 73.4 ± 10.9 years (45–87 years). Mean follow-up period was 14.3 ± 6.0 months (6–24 months). Results: The preoperative intraocular pressure was 21.4 ± 3.7 mm Hg. The postoperative intraocular pressure 6 months after the surgery was 12.8 ± 3.4 mm Hg. A postoperative tension spike (>30 mm Hg) was observed in 2 eyes. Six months after the operation, the intraocular pressure was controlled under 21 mm Hg in all eyes, and under 16 mm Hg in 18 eyes. The medication score (one point per antiglaucomatous medication) was 2.0 ± 1.6 before the surgery and 0.4 ± 0.7 after the surgery. The mean refractive error after the operation was –0.8 ± 0.7 D (range –2.4 to 0 D). The deviation of the actual refractive error from the predicted one was +0.29 ± 0.54 D (range –0.52 to +1.10 D). Conclusion: The outcome of the combined operation for open-angle glaucoma and coexisting cataract was promising.

Effect of localized defocus on detection thresholds for different sized targets in the fovea and periphery.

Previous studies of optical blur in perimetry have measured the effect of foveal refractive error on peripheral perimetric detection thresholds. Since peripheral refractive error can be significantly different from that of the fovea we wished to remove the ambiguity of previous results by correcting the actual peripheral refractive error first before adding blur. We measured detection thresholds in the fovea and at 30 degrees in the horizontal temporal field in two trained observers. Peripheral refractive error was determined at each location and thresholds measured at the same locations for stimuli ranging in size from 0.2 to 6.4 degrees and refractive errors between +/-4.00 diopters. Foveal thresholds increased immediately with increasing refractive error, particularly for smaller stimulus sizes. At 30 degrees, thresholds for smaller stimuli were less affected by defocus initially and then increased more sharply. Larger stimuli were relatively unaffected by defocus such that when stimulus size reached 1.6 degrees there was little or no increase in threshold for refractive error between +/-4.00 diopters. Peripheral refractive error, largely forgotten by perimetrists, has a significant effect on performance, particularly for smaller stimuli. Differences in foveal vs peripheral viewing can be explained by differences in ganglion cell receptive field sizes.