Minnesota Lions Eye Bank

This volume discusses an in-depth theory of function spaces in an Euclidean setting, including several new features, not previously covered in the literature. In particular, it develops a unified theory of anisotropic Besov and Bessel potential spaces on Euclidean corners, with infinite-dimensional Banach spaces as targets. It especially highlights the most important subclasses of Besov spaces, namely Slobodeckii and Hölder spaces. In this case, no restrictions are imposed on the target spaces, except for reflexivity assumptions in duality results. In this general setting, the author proves sharp embedding, interpolation, and trace theorems, point-wise multiplier results, as well as Gagliardo-Nirenberg estimates and generalizations of Aubin-Lions compactness theorems. The results presented pave the way for new applications in situations where infinite-dimensional target spaces are relevant – in the realm of stochastic differential equations, for example.

PURPOSE: The Salisbury Eye Evaluation Project is a longitudinal study of risk factors for age-related eye diseases and the impact of eye disease and visual impairment on physical disability. In this article, the authors report the prevalence of visual impairment in their population and explore the relations among the various measures of visual function. METHODS: A population-based sample of 2520 residents of Salisbury, Maryland, between the ages of 65 and 84 years were enrolled in the study. Twenty-six percent of participants were black. Vision tests included best-corrected Early Treatment Diabetic Retinopathy Study acuity, Pelli-Robson contrast sensitivity with and without glare, Randot stereoacuity, and 60 degrees Humphrey visual fields. RESULTS: Visual function decreased linearly with age for the acuity, contrast sensitivity, glare, and visual field tests. Stereoacuity remained constant into the mid-70s and declined at an accelerating rate thereafter. Black participants had lower contrast sensitivity, reduced stereoacuity, and worse visual fields, at all ages compared to white participants; however, white participants were more sensitive to glare. The overall prevalence of visual acuity impairment in blacks was 5.6% versus 3.0% for whites, using the traditional United States definition (worse than 20/40 to better than 20/200) and 3.3% for blacks versus 1.6% for whites, using the World Health Organization definition (worse than 20/60 to 20/400). Acuity was correlated moderately with contrast sensitivity, stereoacuity, and visual fields (Spearman rho = 0.50, 0.35, and 0.34, respectively). The correlation between acuity and glare sensitivity was low (rho = 0.12). CONCLUSIONS: Many aspects of visual function, not just acuity, decline with age. Black participants have more visual impairement than do white participants for all tests except glare sensitivity. The prevalence of visual acuity impairement in the Salisbury Eye Evaluation population is lower than that reported by other studies using similar test procedures. Low-to-moderate correlations among vision test scores suggest that several different dimensions of visual function are being assessed.

BACKGROUND/AIMS: To determine to what extent subjects implanted with the Argus II retinal prosthesis can improve performance compared with residual native vision in a spatial-motor task. METHODS: High-contrast square stimuli (5.85 cm sides) were displayed in random locations on a 19″ (48.3 cm) touch screen monitor located 12″ (30.5 cm) in front of the subject. Subjects were instructed to locate and touch the square centre with the system on and then off (40 trials each). The coordinates of the square centre and location touched were recorded. RESULTS: Ninety-six percent (26/27) of subjects showed a significant improvement in accuracy and 93% (25/27) show a significant improvement in repeatability with the system on compared with off (p<0.05, Student t test). A group of five subjects that had both accuracy and repeatability values <250 pixels (7.4 cm) with the system off (ie, using only their residual vision) was significantly more accurate and repeatable than the remainder of the cohort (p<0.01). Of this group, four subjects showed a significant improvement in both accuracy and repeatability with the system on. CONCLUSION: In a study on the largest cohort of visual prosthesis recipients to date, we found that artificial vision augments information from existing vision in a spatial-motor task. Clinical trials registry no NCT00407602.

PURPOSE: To report the safety and efficacy of descemetorhexis without grafting as a primary intervention in Fuchs dystrophy, and the use of a ROCK inhibitor, ripasudil as a salvage agent in failing cases. METHODS: Twelve eyes of 11 patients underwent central descemetorhexis not exceeding 4 mm. All had Fuchs dystrophy-producing visual symptoms, requesting intervention. Exclusion criteria were a peripheral endothelial cell count <1000 and central edema. Corneal clearance and visual parameters were recorded monthly until corneal clearance was observed, then at intervals of 6 months. Cases failing to clear by month 2 were considered for salvage treatment. This consisted of treatment with 1 of 2 formulations of Rho-associated kinase inhibitor eye drops. Endothelial keratoplasty was planned as the final salvage procedure in unsuccessful cases. RESULTS: Nine of 12 eyes cleared spontaneously between 2 and 6 months. One eye failed to clear by month 5 and topical Y-27632 was administered, without success. Endothelial keratoplasty was performed. In 2 eyes, healing stalled at 3 and 2 months. In both cases, topical ripasudil administered 6 times a day for 2 weeks resulted in complete corneal clearance. In cases achieving corneal clearance, best spectacle corrected visual acuity improved from a mean of 0.26 to 0.125 (logMAR) with subjective improvement in quality of vision. CONCLUSIONS: In Fuchs dystrophy with visual degradation due to central guttae, descemetorhexis without grafting is a viable procedure for visual rehabilitation. Careful patient selection is required, but the advent of topical ripasudil as a salvage agent suggests that a broader application of the surgery may be possible. Further study into the use of this agent is now needed.

The American Medical Association's (AMA) visual efficiency scale, a vision disability metric based on visual impairment measurements, was adopted in 1925. That scale was based on a 30-year history of theoretical models in vision economics, a misinterpretation of Snellen notation for visual acuity, and an erroneous application of Weber's psychophysical law. The AMA visual efficiency scale survived uncontested for 75 years. In 2001, the AMA adopted a new vision disability scale based on logarithmic transformations of visual acuity and visual field diameter. Like the earlier visual efficiency scale, the new scale is theoretical-it is not supported by any data that speak to the relationship between vision disability and visual impairments. Attempts to measure vision disability date to the early 1980s with the development of self-assessment visual function rating scale questionnaires. Nearly all of the questionnaires developed over the last 20 years use Likert scales, but use them incorrectly. The development of a vision disability metric based on Likert scaling parallels the historical development of other forms of measurement. A tutorial review of psychometrics-classical test theory, item response theory, and Rasch analysis-shows how vision disability measurement scales can be estimated from Likert-type visual function rating scales. We conclude that preliminary data relating measures of vision disability to measures of visual acuity and visual fields support the new AMA vision disability scale.

PURPOSE: To determine the association between visual field loss and orientation and mobility (O&M) performance in a population-based sample of older adults and to identify the specific regions of the visual field that are most strongly associated with O&M performance. METHODS: A population-based sample of 1504 persons between the ages of 72 to 92 was enrolled in the third round of Salisbury Eye Evaluation. Monocular visual fields (60 degrees radius) were tested with the 81-point, single intensity (24 dB) screening test strategy on the Humphrey Field Analyzer. Binocular visual fields were estimated from a combination of the monocular fields. The number of points missed was calculated for the overall visual field and for 3 non-overlapping regions: central (< or = 20 degrees radius), upper- and lower-peripheral visual fields. Orientation and mobility performance was evaluated by walking speed, number of bumps, and number of orientation errors on a circuitous, 32.8-m course seeded with obstacles. Log-linear regressions and linear regressions, adjusting for age, gender, body mass, height, cognitive and general health status, were performed. RESULTS: Loss in the overall visual field was associated with an increase in the number of bumps and decrease in walking speed. Visual field loss was not associated with the number of orientation errors. Out of the three visual field sub-regions that we tested, in terms of percentage of loss, the central and lower peripheral regions showed comparable decrements in walking speed and the central region was most strongly associated with number of bumps. CONCLUSIONS: The loss in visual field, which occurs with aging, is associated with a decline in mobility performance. Walking speed decreases, and the number of bumps into obstacles increases, with decreases in the visual field. The number of orientation errors is not associated with the loss in visual field that occurs with aging.

During the current coronavirus disease 2019 (COVID-19) epidemic, the concern for reducing disease transmission has led to a worldwide increase in face mask utilization. During this period, we have observed a corresponding increase in ocular irritation and dryness among regular mask users. This finding has not been previously described in the literature but has important implications on eye health and infection prevention, as mask use is likely to continue for the foreseeable future.

Abstract Citizen science is gaining increasing prominence as a tool for science and engagement. However, despite being a potentially valuable tool for sustainable development, citizen science has little visibility in many developing countries. We undertook a collaborative prioritisation process with experts in conservation and the environment to assess the potential of environmental citizen science in East Africa, including its opportunities, benefits and barriers. This provided principles that are applicable across developing countries, particularly for large‐scale citizen science. We found that there was great potential for citizen science to add to our scientific knowledge of natural resources and biodiversity trends. Many of the important benefits of citizen science were for people, as well as the environment directly. Major barriers to citizen science were mostly social and institutional, although projects should also consider access to suitable technology and language barriers. Policy implications . Citizen science can provide data to support decision‐making and reporting against international targets. Participation can also provide societal benefits, informing and empowering people, thus supporting the United Nations’ Sustainable Development Goals. In developing countries, innovation is needed to further develop culturally relevant citizen science that benefits participants and end users. This should be supported through regional networks of stakeholders for sharing best practice.

PURPOSE: Recently, we found that 17beta-estradiol induces cytokine and MMP gene expression in SV40 immortalized human corneal epithelial cells (SV40 HCEs). The purpose of this study was to determine if 17beta-estradiol stimulates MMP secretion by cultures of SV40 HCEs and primary human corneal epithelial cells. Further, we determined if estrogen influenced cytokine and MMP gene expression in the primary cultures. METHODS: Gelatin zymography was used to identify MMP-2 and MMP-9 gelatinase activity in the culture medium from SV40 HCEs and primary human corneal epithelial cell cultures exposed to vehicle or 17beta-estradiol for 6 or 24 hour. In addition, 17beta-estradiol effects on cytokine and MMP gene expression in primary cultures were evaluated by real-time PCR methods. RESULTS: 17beta-estradiol had no significant effects on MMP activity in the culture media of either SV40 HCEs or primary corneal epithelial cell cultures. SV40 HCEs secreted predominantly MMP-2, whereas the primary cultures secreted predominantly MMP-9. In primary cultures, 17beta-estradiol caused a significant decrease of IL-6 and IL-8 gene expression, but had no effect on the levels of IL-1beta, MMP-2, and MMP-9 gene expression. CONCLUSIONS: Our findings suggest that 17beta-estradiol effects on gelatinase gene expression in SV40 HCEs are not translated into changes in secreted MMP activity. Estrogen influences on gene expression of cytokine and MMPs in primary cultures are different from those in SV40 HCEs.

PURPOSE: To investigate the incidence of fungal infections after corneal transplantation to determine whether storage media supplementation with an antifungal should be considered. METHODS: Adverse reactions reported to the Eye Bank Association of America through the online adverse reaction reporting system between January 1, 2007, and December 31, 2010, were reviewed to identify cases of recipient fungal infection. Data were collected regarding the donor, the donor cornea, recovery and processing, and mate culture and clinical course of the recipients. RESULTS: Thirty-one cases of culture-proven fungal keratitis (n = 14) and endophthalmitis (n = 17) were reported out of 221,664 corneal transplants performed using corneal tissue distributed by domestic eye banks (1.4 cases per 10,000 transplants performed). Although the annual incidence of postkeratoplasty fungal infection has not increased significantly since 2005, a trend toward an increasing rate of fungal infection has been observed. Fungal infections were more commonly reported after endothelial keratoplasty procedures (0.022%) than penetrating keratoplasty procedures (0.012%), but the difference was not statistically significant (P = 0.076). Additionally, no association was found between fungal infection after endothelial keratoplasty and whether the lamellar tissue cut was performed by the surgeon or the eye bank technician. Seventy-three percent (16 of 22) of the fungal cultures performed on the mate corneas were positive, with infection developing in 67% (10 of 15) of recipient eyes (endophthalmitis in 6 eyes and keratitis in 4 eyes). CONCLUSIONS: Although a nonsignificant increasing trend in the rate of fungal infection has been observed over the past 6 years, it is not sufficiently compelling to pursue antifungal supplementation of donor storage media.

Histologic studies seem to imply that the mechanical compliance of the optic nerve head, namely, its displacement under a given pressure, may be altered in glaucoma. We have developed a method to noninvasively measure the optic nerve head displacement. In postmortem human glaucomatous eyes, the optic nerve head compliance decreased as the visual field worsened (n = 15, r = -.34). The mean difference between the optic nerve head displacement of the two eyes in subjects with symmetric clinical findings differed significantly from the mean in subjects with asymmetry. In the latter group, the lower value was always measured in the more affected eye. No significant correlation was found between age and the optic nerve head compliance. Overall, the results indicate that, in glaucoma, there is a stiffening of the mechanical support of the optic nerve head.

Importance Chat Generative Pre-Trained Transformer (ChatGPT) has shown promising performance in various fields, including medicine, business, and law, but its accuracy in specialty-specific medical questions, particularly in ophthalmology, is still uncertain. Purpose This study evaluates the performance of two ChatGPT models (GPT-3.5 and GPT-4) and human professionals in answering ophthalmology questions from the StatPearls question bank, assessing their outcomes, and providing insights into the integration of artificial intelligence (AI) technology in ophthalmology. Methods ChatGPT's performance was evaluated using 467 ophthalmology questions from the StatPearls question bank. These questions were stratified into 11 subcategories, four difficulty levels, and three generalized anatomical categories. The answer accuracy of GPT-3.5, GPT-4, and human participants was assessed. Statistical analysis was conducted via the Kolmogorov-Smirnov test for normality, one-way analysis of variance (ANOVA) for the statistical significance of GPT-3 versus GPT-4 versus human performance, and repeated unpaired two-sample t-tests to compare the means of two groups. Results GPT-4 outperformed both GPT-3.5 and human professionals on ophthalmology StatPearls questions, except in the "Lens and Cataract" category. The performance differences were statistically significant overall, with GPT-4 achieving higher accuracy (73.2%) compared to GPT-3.5 (55.5%, p-value < 0.001) and humans (58.3%, p-value < 0.001). There were variations in performance across difficulty levels (rated one to four), but GPT-4 consistently performed better than both GPT-3.5 and humans on level-two, -three, and -four questions. On questions of level-four difficulty, human performance significantly exceeded that of GPT-3.5 (p = 0.008). Conclusion The study's findings demonstrate GPT-4's significant performance improvements over GPT-3.5 and human professionals on StatPearls ophthalmology questions. Our results highlight the potential of advanced conversational AI systems to be utilized as important tools in the education and practice of medicine.

Intrastromal corneal rings can flatten the human cornea, providing a potential new method of keratorefractive surgery. We investigated the effect of implanting various ring sizes of a given thickness in 8.50-mm intrastromal channels dissected in human eye bank corneas. A new intraoperative corneal topography device was used to obtain serial data. Smaller rings with no expansion pressure on the channels were found to induce corneal flattening presumably due to the ring thickness alone. Rings of increasing diameters produced high degrees of corneal flattening at progressively declining rates; this suggests that shear stresses may have expanded the channel due to mechanical stresses placed by our particular experimental technique. Implantation techniques that minimize stress on the outer channel lamellae appear advisable. New ring designs should take ring thickness into consideration along with outer edge configurations that minimize shear stresses on the lamellar channels.

PURPOSE: To evaluate the immediate postoperative corneal topography after the deep lamellar endothelial keratoplasty procedure. METHODS: Eight eye bank eyes underwent deep lamellar endothelial keratoplasty through a 9.0-mm limbal incision replacing the central 7.0 mm of posterior stroma and endothelium through the lamellar pocket wound. Orbscan topography was performed before and after surgery, and simulated keratometry readings and central corneal diopter power were recorded. The change in astigmatism and corneal power from preoperative to postoperative readings was then determined. RESULTS: The net change in corneal astigmatism averaged 0.4+/-0.5 diopters (range, -0.1 to 1.1 diopters). The net change in corneal power averaged -0.2+/-0.4 diopters of flattening (range, -0.9 to +0.2 diopters). Neither the astigmatism nor the corneal power levels after this surgery were significantly different from the preoperative topography (p = 0.22 and 0.27, respectively). CONCLUSIONS: The deep lamellar endothelial keratoplasty procedure, with its absence of corneal surface incisions or sutures, has no significant effect on immediate postoperative corneal topography. The potential advantages of this procedure over penetrating keratoplasty in the treatment of endothelial dysfunction are considerable.

INTRODUCTION: The incidence of ectasia following refractive surgery is unclear. This review sought to determine the worldwide rates of ectasia after photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) based on reports in the literature. METHODS: A systematic review was conducted according to modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Publications were identified by a search of eight electronic databases for relevant terms between 1984 and 2021. Patient characteristics and preoperative values including manifest refractive spherical refractive equivalent (MRSE), central corneal thickness (CCT), anterior keratometry, postoperative residual stromal bed (RSB), and percent tissue altered (PTA) were summarized. In addition, annual rates of each refractive surgery were determined, and incidence of post-refractive ectasia for each type was calculated using the number of ectatic eyes identified in the literature. RESULTS: In total, 57 eyes (70 eyes including those with preoperative risk factors for ectasia) were identified to have post-PRK ectasia, while 1453 eyes (1681 eyes including risk factors) had post-LASIK ectasia, and 11 eyes (19 eyes including risk factors) had post-SMILE ectasia. Cases of refractive surgery performed annually were estimated as 283,920 for PRK, 1,608,880 for LASIK, and 96,750 for SMILE. Reported post-refractive ectasia in eyes without preoperative identifiable risk factors occurred with the following incidences: 20 per 100,000 eyes in PRK, 90 per 100,000 eyes in LASIK, and 11 per 100,000 eyes in SMILE. The rate of ectasia in LASIK was found to be 4.5 times higher than that of PRK. CONCLUSION: Post-refractive ectasia occurs at lower rates in eyes undergoing PRK than LASIK. Although SMILE appears to have the lowest rate of ectasia, the number of cases already reported since its recent approval suggests that post-SMILE ectasia may become a concern. Considering that keratoconus is a spectrum of disease, pre-existing keratoconus may play a larger role in postoperative ectasia than previously accounted for in the literature.

Persistent corneal epithelial defects (PEDs or PCEDs) result from the failure of rapid re-epithelialization and closure within 10-14 days after a corneal injury, even with standard supportive treatment. Disruptions in the protective epithelial and stromal layers of the cornea can render the eye susceptible to infection, stromal ulceration, perforation, scarring, and significant vision loss. Although several therapies exist and an increasing number of novel approaches are emerging, treatment of PEDs can still be quite challenging. It is important to treat the underlying causative condition, which may include an infection, limbal stem cell deficiency, or diabetes, in order to facilitate wound healing. Standard treatments, such as bandage contact lenses (BCLs) and artificial tears (ATs), aim to provide barrier protection to the epithelial layer. Recently-developed medical treatments can target the re-epithelialization process by facilitating access to growth factors and anti-inflammatory agents, and novel surgical techniques can provide re-innervation to the cornea. PEDs should be treated within 7-10 days to avoid secondary complications. These interventions, along with a step-wise approach to management, can be useful in patients with PEDs that are refractory to standard medical treatment. In this review, we discuss the epidemiology, etiology, diagnosis, current and novel management, and prognosis of persistent epithelial defects.

PURPOSE: The aim of this study was to evaluate preparation outcomes of tissue prepared for Descemet membrane endothelial keratoplasty (DMEK) from diabetic and nondiabetic donors. METHODS: In this nonrandomized, consecutive case series, DMEK grafts were prepared from diabetic and nondiabetic donors by experienced technicians in 2 eye banks using slightly different, modified submerged manual preparation techniques to achieve "prestripped" graft tissue. Graft preparation results were analyzed retrospectively. The main outcome measure was the rate of unsuccessful (failed) DMEK graft preparations, defined as tears through the graft area that prevent tissue use. RESULTS: A total of 359 corneas prepared from 290 donors (114 diabetic and 245 nondiabetic) were included in the statistical analysis of graft preparation failure. There were no significant differences between diabetic and nondiabetic donor tissue characteristics with respect to donor age, death to preservation time, death to preparation time, endothelial cell density, percent hexagonality, or coefficient of variation. DMEK tissue preparation was unsuccessful in 19 (5.3%) cases. There was a significant difference in the site-adjusted rate of DMEK preparation failure between diabetic [15.3%; 95% confidence interval (CI), 9.0-25.0] and nondiabetic donors (1.9%; 95% CI, 0.8-4.8), and the corresponding site-adjusted odds ratio of DMEK graft preparation failure in diabetic donor tissue versus nondiabetic donor tissue was 9.20 (95% CI, 2.89-29.32; P = 0.001). CONCLUSIONS: Diabetes may be a risk factor for unsuccessful preparation of donor tissue for DMEK. We recommend caution in the use of diabetic tissue for DMEK graft preparation. Further study is needed to identify what subset of diabetic donors is at risk for unsuccessful DMEK graft preparation.

PURPOSE: To investigate the incidence of adverse reactions after corneal transplantation, reported to the Eye Bank Association of America. METHODS: Incidence of adverse reactions from January 1, 2007, to December 31, 2014, was analyzed. RESULTS: Of the 354,930 transplants performed in the United States, adverse reactions were reported in 494 cases (0.139%). Primary graft failure (PGF) predominated (n = 319; 0.09%) followed by endophthalmitis (n = 99; 0.028%) and keratitis (n = 66; 0.019%). The procedure type predominantly associated with PGF was endothelial keratoplasty (EK) in 56% (n = 180; 11 per 10,000 grafts), followed by penetrating keratoplasty (PK) in 42% (n = 135; 6.9 per 10,000 grafts). The procedure type predominantly associated with endophthalmitis and keratitis was EK in 63% (n = 104; 6.3 per 10,000 grafts) followed by PK in 34% (n = 56; 2.8 per 10,000 grafts), anterior lamellar keratoplasty in 1% (n = 2; 2.7 per 10,000 grafts), and keratoprosthesis in 1% (n = 2; 12.4 per 10,000 grafts). Although the incidence of PGF and endophthalmitis between PK and EK was noteworthy, the difference was not statistically significant (P = 0.098). Endophthalmitis-associated pathogens were isolated in 78% of cases: predominantly Candida species (65%), gram-positive organisms (33%), and gram-negative rods (2%). Keratitis-associated pathogens were isolated in 64% of cases: predominantly Candida species (81%), Herpes simplex virus (7%), gram-negative organisms (7%), and gram-positive organisms (5%). CONCLUSIONS: PGF was the most commonly reported adverse reaction, disproportionately associated with EK. An increasingtrend in the rate of endophthalmitis and keratitis was observed, disproportionately associated with EK and Candida species.

PURPOSE: The purpose of this study was to determine whether persons with advanced vision impairment, when walking an unfamiliar route, visually sample the environment in a different manner than do persons with normal vision. METHODS: Direction of gaze was measured in six persons with retinitis pigmentosa (RP) and in three persons with normal vision as they walked an unfamiliar, obstacle-free route while viewing the environment in a head-mounted display. RESULTS: Persons with RP fixated over a larger area in the environment and at different features than did persons with normal vision. Persons with normal vision directed their gaze primarily ahead or at the goal, whereas persons with RP directed their gaze at objects on the walls, downward, or at the layout (i.e., edge-lines or boundaries between walls). The results also showed a significant negative correlation between the horizontal visual field extent of the RP subjects and the proportion of downward-directed fixations. CONCLUSIONS: Persons with advanced vision impairment as a result of RP visually sample the environment in a manner different from persons with normal vision.

Square scleral corneal, square clear corneal, and rectangular clear corneal incisions were constructed in six cadaver eyes that had no previous intraocular surgery. The 3.2 mm or smaller wounds had sutureless closures. To determine their relative abilities to resist leakage and iris prolapse, eyes were tested at external pressures of up to 525 pounds per square inch (psi) at one of two intraocular pressure (IOP) ranges: 10 to 15 mm Hg or 20 to 25 mm Hg. The square scleral corneal (3.2 mm x 3.2 mm) and square clear corneal wounds (3.2 mm x 3.2 mm, 2.0 mm x 2.0 mm, 1.0 mm x 1.0 mm) withstood external pressure without effect at both IOP ranges, up to the maximum 525 psi. This level of external pressure was far greater than pressures withstood by rectangular clear corneal wounds, especially the wound usually constructed in clinical practice (3.2 mm x 2.0 mm), which leaked and demonstrated iris prolapse at 13 psi at the lower IOP. The square clear corneal wounds that were stable at 525 psi, however, are either clinically impractical (visual axis encroachment from 3.2 mm x 3.2 mm wound) or not technologically feasible until the size of phacoemulsification tips and intraocular lenses can be further reduced. Thus, of the procedures for small incision cataract surgery presently in use, the square scleral corneal incision with 1.5 mm internal corneal lip appears to offer greater stability and safety than the conventional rectangular clear corneal incision (3.2 mm x 2.0 mm).