Utilization rate and usage patterns of phakic and pseudophakic donor corneas recovered by the Singapore Eye Bank.

PURPOSE: To compare the utilization rate and usage patterns of pseudophakic and phakic donor corneas recovered by the Singapore Eye Bank. METHODS: Records of local donor corneas recovered by the Singapore Eye Bank from 2012 to 2017 were examined. Corneas that were deemed suitable for clinical use were stratified into phakic and pseudophakic groups. We examined the basic demographic pattern of both groups and the initial type of surgery/ies that the corneas were suitable for based on tissue parameters such as time from harvesting, stromal clarity, the clear central corneal area, the presence of Descemet's membrane tears or defects, and endothelial cell density and quality. We also identified the types of corneal grafts that the corneas were eventually used for; Penetrating Keratoplasty (PK), Anterior Lamellar Keratoplasty (ALK), Endothelial Keratoplasty (EK). Finally, the overall utilization rates for each group were determined. RESULTS: A total of 986 corneas deemed suitable for transplant were analyzed, 908 (92%) were phakic and 78 were pseudophakic (8%). The average age of pseudophakic donor corneas was (65 ± 8 yrs. old) and there was a slight male preponderance for both groups (55%). Age adjusted analysis of pseudophakic corneas showed the endothelial cell density (ECD) (mean: 2327 ± 47.1 cells/mm2) and clear area (mean: 7.0 ± 0.7 mm) were lesser than phakic corneas. The percentage of pseudophakic corneas that were of EK standard (ECD >2500 cells/mm2) were lower compared to phakic corneas (37% and 77% respectively, p < 0.001). There was significant correlation between previous cataract surgery and the endothelial cell count of the donor corneas (p < 0.001), and regression analysis also showed a strong association of ECD with cataract surgery in reference to non-cataract surgery (-478.8 (95% CI-576.9 to -380.7). The overall utilization rate for pseudophakic corneas was 58% compared to that of phakic corneas at 83%. The most common reason for pseudophakic corneas not to be utilized was due to the presence of Descemet's membrane (DM) tears or defects under the main or side port incision created during phacoemulsification (30%). Phakic corneas were used primarily for optical grafts 84% (mainly EK) while pseudophakic corneas were used mostly for therapeutic/tectonic grafts 47% (mainly ALK or patch grafts). CONCLUSION: Compared to phakic donor corneas, pseudophakic corneas generally have lower overall tissue quality leading to lower uptake by surgeons and lower utilization rates. Eye banks must continuously refine their donor acceptance criteria and engage surgeons to optimize utilization of each recovered tissue.

Descemet Membrane Endothelial Keratoplasty With a Pull-Through Insertion Device: Surgical Technique, Endothelial Cell Loss, and Early Clinical Results.

PURPOSE: To describe a surgical technique for Descemet membrane endothelial keratoplasty (DMEK) using a pull-through, endothelium-in insertion device, the DMEK EndoGlide. We evaluated the endothelial cell loss (ECL) associated with the EndoGlide-DMEK (E-DMEK) technique in both ex vivo and prospective clinical studies. METHODS: The ex vivo study involved calcein acetoxymethyl staining and preparation of DMEK grafts, which were trifolded endothelium-in, loaded into the EndoGlide, pulled through, and unfolded in imaging dishes. Inverted fluorescent microscopy was performed, and ECL was quantified using trainable segmentation software. The prospective clinical series describes the outcomes of consecutive surgeries using the E-DMEK technique. Grafts were pulled through the EndoGlide with forceps and unfolded in the anterior chamber endothelium-down. Our main outcome measure was ECL in both studies. RESULTS: In the ex vivo study with 9 human donor corneas, mean ECL was 15.2% ± 5.4% (n = 9). In our clinical series of 69 eyes, leading indications for surgery were pseudophakic/aphakic bullous keratopathy (47.8%), previous failed grafts (23.2%), and Fuchs endothelial dystrophy (18.8%). Rebubbling and primary graft failure rates related to E-DMEK were 11.6% and 1.5%, respectively. Among eyes with at least 6 months of follow-up, mean preoperative endothelial cell density was 2772 (range 2457-3448) cells/mm, and postoperative endothelial cell density was 1830 (range 541-2545) cells/mm. Mean ECL was 33.6% (range 7.5-80.4; n = 32) at the 7.1 (range 6-11) months follow-up. CONCLUSIONS: The ex vivo and pilot clinical studies suggest that E-DMEK shows acceptable rates of ECL, with safe and promising early clinical outcomes.

Lamellar Dissection Technique for Descemet Membrane Endothelial Keratoplasty Graft Preparation.

PURPOSE: To describe a novel lamellar dissection technique for Descemet membrane endothelial keratoplasty (DMEK) graft preparation, and to evaluate the rate of endothelial cell loss (ECL) and graft preparation failure associated with this technique. METHODS: We conducted an ex vivo laboratory-based study comparing ECL between the lamellar dissection and peeling techniques. Eight pairs of human donor corneas underwent calcein acetoxymethyl staining-all right eyes underwent the peeling technique and all left eyes underwent the lamellar dissection technique. ECL was quantified by image analysis with trainable segmentation software and compared between groups. We also conducted a retrospective analysis of 161 consecutive DMEK graft preparations by a single surgeon using the lamellar dissection technique from 2010 to 2018. Data on donor characteristics and graft preparation failures were obtained. RESULTS: Baseline donor characteristics were comparable in both arms of the laboratory-based study. Mean (SD) ECL with the lamellar dissection and peeling techniques was 13.8% (4.2%) and 11.2% (6.1%), respectively. There was no significant difference between the two (P = 0.327). In the clinical series, there were 2 graft preparation failures in 161 cases (1.2%). Among cases performed on diabetic donor tissue, the rate of graft preparation failure was 4.7%. CONCLUSIONS: The lamellar dissection technique has a similar rate of ECL compared with the peeling technique for DMEK graft preparation. This technique also has a low rate of graft preparation failure and may be a useful technique for diabetic donor tissue.

A cellular and proteomic approach to assess proteins extracted from cryopreserved human amnion in the cultivation of corneal stromal keratocytes for stromal cell therapy.

BACKGROUND: Human corneal stromal keratocytes propagated in culture media supplemented with human amnion extract (AME) can correct early corneal haze in an animal model. Clinical application of cultivated keratocytes is limited by infectious disease screening before amnion products can be used in humans. It remains unclear if AME from cryopreserved versus fresh human amnion can support human keratocyte propagation, and which components of the extract promote keratocyte growth. METHODS: Three placentas were collected for the preparation of fresh and cryopreserved amnion tissues followed by homogenization and protein extraction. AME protein profiles were studied using isobaric tagging for relative and absolute quantitation (iTRAQ) proteomics. Enriched gene ontology (GO) terms and functional classes were identified. Primary human keratocytes from 4 donor corneas were cultured in media supplemented with fresh AME (F-AME) or cryopreserved AME (C-AME). Cell viability, proliferation and keratocyte marker expression were examined by confocal immunofluorescence and flow cytometry. RESULTS: AME proteomics revealed 1385 proteins with similar expression levels (between 0.5- and 2-fold) between F- and C-AME, while 286 proteins were reduced (less than 0.5-fold) in C-AME. Enriched GO term and biological pathway analysis showed that those proteins with comparable expression between F-AME and C-AME were involved in cell metabolism, epithelial-mesenchymal transition, focal adhesion, cell-extracellular matrix interaction, cell stress regulation and complement cascades. Human corneal stromal keratocytes cultured with F-AME or C-AME showed similar morphology and viability, while cell proliferation was mildly suppressed with C-AME (P > 0.05). Expression of aldehyde dehydrogenase 3A1 (ALDH3A1) and CD34 was similar in both cultures. CONCLUSION: AME from cryopreserved amnion had limited influence on keratocyte culture. It is feasible to use protein extract from cryopreserved amnion to propagate human keratocytes for potential translational applications.

Knowledge and attitudes toward corneal donation among Singaporean youth: a cross-sectional study.

BACKGROUND: To assess the knowledge of Singaporean youth regarding corneal donation and gauge their willingness to donate their corneas. METHODS: We conducted a cross-sectional study among 500 students from five tertiary institutions in Singapore. All students answered self-administered questionnaires which included seven questions that tested knowledge and three questions that determined willingness to donate corneas. RESULTS: Among 500 Singaporean youth aged 18 to 25, most students (73.2 %) answered 3 or fewer of the 7 questions about corneal donation correctly. With regards to the willingness to donate, 155 (31 %) were willing to donate their corneas, 111 (22.2 %) were not willing to donate their corneas, and 234 (46.8 %) were undecided. Willingness to donate corneas was associated with an older age group (21 to 25 years old), those who are non-Muslims, and have good basic knowledge. Particularly, students with good basic knowledge were 1.71 times more likely to willingly donate their corneas. CONCLUSION: The knowledge of the Singaporean youth regarding corneal donation and transplantation is poor. Since insufficient information was cited as the most common reason for being undecided in regards to corneal donation, specific and tailored programs to increase knowledge and awareness are needed to convince the youth to support corneal donation.

Cost Minimization Analysis of Precut Cornea Grafts in Descemet Stripping Automated Endothelial Keratoplasty.

Descemet stripping automated endothelial keratoplasty (DSAEK) is the most common corneal transplant procedure. A key step in the procedure is preparing the donor cornea for transplantation. This can be accomplished via 1 of 3 alternatives: surgeon cuts the cornea on the day of surgery, the cornea is precut ahead of time in an offsite facility by a trained technician, or a precut cornea is purchased from an eye bank. Currently, there is little evidence on the costs and effectiveness of these 3 strategies to allow healthcare providers decide upon the preferred method to prepare grafts.The aim of this study was to compare the costs and relative effectiveness of each strategy.The Singapore National Eye Centre and Singapore Eye Bank performed both precut cornea and surgeon-cut cornea transplant services between 2009 and 2013.This study included 110 subjects who received precut cornea and 140 who received surgeon-cut cornea. Clinical outcomes and surgical duration were compared across the strategies using the propensity score matching. The cost of each strategy was estimated using the microcosting and consisted of facility costs and procedural costs including surgical duration. One-way sensitivity analysis and threshold analysis were performed.The cost for DSAEK was highest for the surgeon-cut approach ($13,965 per procedure), followed by purchasing precut corneas ($12,659) and then setting up precutting ($12,421). The higher procedural cost of the surgeon-cut approach was largely due to the longer duration of the procedure (surgeon-cut = 72.54 minutes, precut = 59.45 minutes, P < 0.001) and the higher surgeon fees. There was no evidence of differences in clinical outcomes between grafts that were precut or surgeon-cut. Threshold analysis demonstrated that if the number of cases was below 31 a year, the strategy that yielded the lowest cost was purchasing precut cornea from eye bank. If there were more than 290 cases annually, the cheapest option would be to setup precutting facility.Our findings suggest that it is more efficient for centers that are performing a large number of cornea transplants (more than 290 cases) to set up their own facility to conduct precutting.

A cost-minimization analysis of tissue-engineered constructs for corneal endothelial transplantation.

Corneal endothelial transplantation or endothelial keratoplasty has become the preferred choice of transplantation for patients with corneal blindness due to endothelial dysfunction. Currently, there is a worldwide shortage of transplantable tissue, and demand is expected to increase further with aging populations. Tissue-engineered alternatives are being developed, and are likely to be available soon. However, the cost of these constructs may impair their widespread use. A cost-minimization analysis comparing tissue-engineered constructs to donor tissue procured from eye banks for endothelial keratoplasty was performed. Both initial investment costs and recurring costs were considered in the analysis to arrive at a final tissue cost per transplant. The clinical outcomes of endothelial keratoplasty with tissue-engineered constructs and with donor tissue procured from eye banks were assumed to be equivalent. One-way and probabilistic sensitivity analyses were performed to simulate various possible scenarios, and to determine the robustness of the results. A tissue engineering strategy was cheaper in both investment cost and recurring cost. Tissue-engineered constructs for endothelial keratoplasty could be produced at a cost of US$880 per transplant. In contrast, utilizing donor tissue procured from eye banks for endothelial keratoplasty required US$3,710 per transplant. Sensitivity analyses performed further support the results of this cost-minimization analysis across a wide range of possible scenarios. The use of tissue-engineered constructs for endothelial keratoplasty could potentially increase the supply of transplantable tissue and bring the costs of corneal endothelial transplantation down, making this intervention accessible to a larger group of patients. Tissue-engineering strategies for corneal epithelial constructs or other tissue types, such as pancreatic islet cells, should also be subject to similar pharmacoeconomic analyses.

Risk factors for donor endothelial loss in eye bank-prepared posterior lamellar corneal tissue for descemet stripping automated endothelial keratoplasty.

PURPOSE: The aim of this study was to investigate donor, tissue, and precut procedure risk factors for endothelial cell density (ECD) loss in posterior lamellar corneal tissue preparation by an eye bank for Descemet stripping automated endothelial keratoplasty. METHODS: A total of 259 corneoscleral rims precut by the Singapore Eye Bank from October 2011 to August 2013 were evaluated. Donor characteristics, tissue characteristics, and precut procedure parameters were analyzed. RESULTS: The mean donor age was 57.18 ± 11.35 years, and the mean cutting transition time was 4.16 ± 0.75 seconds. The mean ECD was 2826 ± 225 and 2787 ± 224 cells per square millimeter before and after precutting, respectively, with an average ECD change of -1.38% ± 3.28%. The precutting procedure failure rate was 1.2%. Mutivariate regression analysis showed that an older donor age, a higher ECD before cutting, and a slower cutting transition speed were significant factors. Corneas with an ECD >2800 cells per square millimeter before precutting, cutting transition time >5.5 seconds, and corneas with donor age >65 years were significantly more likely to have greater than 5% ECD loss after precutting (odds ratio, 6.42, 1.66, and 1.62; 95% confidence interval, 1.44-29.43, 1.45-2.72, and 1.66-5.82, respectively). Donor source, death-to-preservation time (range, 0.67-10.88 hours), death-to-precutting time (range, 0-7 days), and graft thickness (range, 43-232 µm) were not statistically significant factors. CONCLUSIONS: The ECD loss in the precut tissue prepared by the eye bank was very low. The risk factors identified provide better understanding of how to improve the quality and safety profiles when preparing graft tissue for Descemet stripping automated endothelial keratoplasty.

Prevalence and risk factors of meibomian gland dysfunction: the Singapore Malay eye study.

PURPOSE: To describe the prevalence and associations of meibomian gland dysfunction (MGD) in an urban Malay population in Singapore. METHODS: Population-based cross-sectional study of 3280 (78.7% response rate) Malay persons aged 40 to 80 years, living in Singapore. MGD was defined by a slit-lamp clinical examination as either lid margin telangiectasia or meibomian gland orifice plugging in at least one eye. Participants underwent a standardized questionnaire and clinical examination, including laboratory investigations. Data were analyzed for 3271 persons. RESULTS: The age-standardized prevalence of MGD was 56.3% [95% confidence interval (CI), 53.3-59.4]. A higher MGD prevalence was found in male participants across all age groups [odds ratio (OR), 1.30; 95% CI, 1.35-1.79], postmenopausal women (OR, 1.64; 95% CI, 1.19-2.33), and all participants with pinguecula (OR, 2.43; 95% CI, 2.08-2.85), high diastolic blood pressure (OR, 1.32; 95% CI, 1.08-1.62), and use of angiotensin II receptor blockers (OR, 4.02; 95% CI, 1.74-9.27). CONCLUSIONS: MGD was highly prevalent in this Asian population and associated with various systemic and ocular conditions.

Donor and surgical risk factors for primary graft failure following Descemet's stripping automated endothelial keratoplasty in Asian eyes.

BACKGROUND: Descemet's stripping automated endothelial keratoplasty (DSAEK) has been shown to have superior refractive and visual results compared with penetrating keratoplasty, but higher rates of primary graft failure (PGF). This paper presents donor and surgical risk factors for PGF in DSAEK cases in Asian eyes. DESIGN: Retrospective case-control study. PARTICIPANTS: All consecutive patients who underwent DSAEK at a tertiary referral teaching hospital from March 2006-December 2008. METHODS: DONOR DETAILS ANALYZED WERE: age of donor, cause of donor death, death to harvesting time, donor storage time, distribution distance of tissue, preoperative endothelial cell count. Surgical factors analyzed were: donor diameter, donor thickness, and method of donor insertion. These risk factors in cases of PGF were compared with patients with successful DSAEK as the control group. MAIN OUTCOME MEASURE: PGF. RESULTS: A total of 124 DSAEK procedures were performed. Six DSAEK procedures (five eyes of five patients; one eye with two failures) resulted in PGF (4.8%). Significant risk factors were found for PGF to include graft insertion using a folding technique (odds ratio [OR], 34.03; 95% confidence interval [CI], 3.75-314.32; P = 0.0017) and a small donor diameter (OR, 39.94; 95% CI, 2.18-732.17; P = 0.013). CONCLUSION: The results of this study suggest that in Asian eyes with shallow anterior chambers, surgical trauma relating to the technique of donor insertion, and the use of a small donor are major risk factors for PGF following DSAEK.

Corneal arcus is a sign of cardiovascular disease, even in low-risk persons.

PURPOSE: To examine the association of corneal arcus to cardiovascular disease (CVD) in an adult, ethnic Indian population. DESIGN: Population-based cross-sectional study. METHODS: Population-based study of ethnic South Asian Indians 40 to 80 years of age in Singapore from June 2007 through March 2009. We obtained a 75.5% response rate (3397/4497). All participants underwent standardized interview and systemic and ocular examinations, followed by nonfasting blood sampling. Corneal arcus was detected using a standardized slit-lamp examination. The main outcome measure was CVD, defined from a self-reported history of previous myocardial infarction, angina, or stroke. RESULTS: Corneal arcus, found in 1701 (50.1%) of 3397 participants, was associated with older age (odds ratio [OR], 3.07; 95% CI, 2.78 to 3.40; P < .001), male gender (OR, 2.17; 95% CI, 1.81 to 2.62; P < .001), higher levels of total cholesterol (OR, 1.14; 95% CI, 1.05 to 1.24; P = .002), hypertension (OR, 1.14; 95% CI, 1.05 to 1.24; P = .013), and cigarette smoking (OR, 1.59; 95% CI, 1.25 to 2.03; P < .001). Corneal arcus was associated with CVD (OR, 1.31; 95% CI, 1.02 to 1.7; P = .0038) independent of the above-named cardiovascular risk factors. Participants with low-risk Framingham scores were more likely to be associated with CVD if they had corneal arcus (men: OR, 2.02; 95% CI, 1.20 to 3.40; P = .008; women: OR, 2.78; 95% CI, 1.36 to 3.01; P < .001). Corneal arcus was associated with CVD independent of the Framingham score (men: Akaike information criterion, 1524.39 for Framingham Score and corneal arcus vs 1527.38 for Framingham Score alone; women: 1000.14 vs 1003.54, respectively). CONCLUSIONS: Corneal arcus is associated with CVD, independent of risk factors in ethnic Indian adults, even in those at low risk for vascular disease.

Prevalence and causes of visual impairment and blindness in an urban Indian population: the Singapore Indian Eye Study.

PURPOSE: To describe the prevalence and causes of visual impairment and blindness in an urban Indian population. DESIGN: Population-based study. PARTICIPANTS: Ethnic Indians aged more than 40 years living in Singapore. METHODS: Participants underwent standardized ophthalmic assessments for visual impairment and blindness, defined using best-corrected visual acuity (BCVA) and presenting visual acuity (PVA), according to US and modified World Health Organization (WHO) definitions. MAIN OUTCOME MEASURES: Unilateral visual impairment or blindness was defined on the basis of the worse eye, and bilateral visual impairment or blindness was defined on the basis of the better eye. Primary causes of visual impairment were determined. RESULTS: A total of 3400 eligible individuals (75.6% response rate) participated. On the basis of US definitions, the age-standardized prevalence was 0.4% for bilateral blindness (≤20/200, better eye) and 3.4% for bilateral visual impairment (<20/40 to >20/200, better eye). Another 0.3% of bilateral blindness and 13.4% of bilateral visual impairment were correctable with refraction. Cataract was the principal cause of best-corrected bilateral blindness (60.0%) and bilateral visual impairment (65.7%). Other major causes of blindness and visual impairment included diabetic retinopathy, age-related macular degeneration, glaucoma, corneal opacity, and myopic maculopathy. CONCLUSIONS: The prevalence of bilateral blindness and visual impairment in Indians living in Singapore is lower than estimates from populations living in India, but similar to estimates obtained from Singapore Malay and Chinese populations. Cataract is the leading cause of blindness and visual impairment. One in 20 cases of bilateral blindness and 1 in 10 cases of bilateral visual impairment are attributable to diabetic retinopathy. These data may have relevance to many ethnic Indian persons living outside India.

Effect of corneal arcus on central corneal thickness, intraocular pressure, and primary open-angle glaucoma: the Singapore Malay Eye Study.

OBJECTIVES: To examine the association of corneal arcus with central corneal thickness (CCT), intraocular pressure (IOP), and the prevalence of primary open-angle glaucoma. METHODS: This was a population-based cross-sectional study of Malay participants aged 40 to 80 years living in Singapore. Participants underwent a standardized interview and systemic and ocular examinations, including CCT, IOP, and corneal curvature radius measurements. Corneal arcus, assessed using a slitlamp, was defined as gray-white or yellow opacity located near the periphery of the cornea but separated from the limbus by a clear zone. RESULTS: Corneal arcus was found in right eyes among 1747 (57.9%) of 3015 participants. After adjusting for age, sex, and systemic factors, IOP was higher (15.87 vs 14.86 mm Hg, P < .001) and CCT was thinner (540.6 vs 543.4 µm, P = .03) in eyes with vs without corneal arcus. In multiple linear regression models, eyes with corneal arcus had on average 1.14 mm Hg higher IOP than eyes without corneal arcus. In the presence of corneal arcus, the linear correlations of CCT × IOP and of corneal curvature radius × IOP were altered. The prevalence of ocular hypertension, but not primary open-angle glaucoma, was significantly higher among participants with corneal arcus than among participants without corneal arcus (P = .02). CONCLUSIONS: Corneal arcus was associated with higher IOP and lower CCT independent of age, sex, and systemic and ocular factors. Further research is required to investigate the clinical implications of these findings for IOP assessment in eyes with corneal arcus.

Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians.

PURPOSE: Current knowledge of ethnic variability in the epidemiology of major eye diseases in Asia is limited. This report summarizes the rationale and study design of the Singapore Indian Chinese Cohort (SICC) Eye Study, a population-based study of ethnic South Asian (Indians) and East Asian (Chinese) older adults in Singapore. METHODS: The SICC examined a population-based cross-sectional sample of 3,300 ethnic Indians and 3,300 ethnic Chinese aged 40-80+ years residing in the South-Western part of Singapore. RESULTS: From two lists of 12,000 names of each ethnic group provided by the Ministry of Home Affairs, age-stratified random sampling was used to select 6,350 names in each group, with a target sample size of 3,300. Invitations were sent to attend a central clinic using letters, telephone calls and home visits. Examination procedures included interviews, measurement of blood pressure, anthropometry, presenting and best-corrected visual acuity, subjective refraction, ocular biometry, Goldmann applanation tonometry, slit-lamp biomicroscopy, optic disc imaging and digital photography of the lens and retina, using a standardized protocol. Selected participants underwent gonioscopic examination, visual field testing, and anterior and posterior segment optical coherence tomography. Blood, tear, and urine samples were collected for biochemical analyses, and stored for genetic and proteomic studies. CONCLUSIONS: In conjunction with the Singapore Malay Eye Study, the SICC study will permit an in-depth evaluation of the prevalence, risk factors, and impact of major eye diseases in Chinese, Indians and Malays, three distinct Asian ethnic groups, whose combined numbers represent half the world's population.

Femtosecond laser creation of donor cornea buttons for Descemet-stripping endothelial keratoplasty.

PURPOSE: To evaluate the accuracy of the thickness and diameter of corneal disks obtained with the Femtec femtosecond laser (20/10 Perfect Vision) for Descemet-stripping endothelial keratoplasty (DSEK). SETTING: Singapore National Eye Centre, Singapore. METHODS: A femtosecond laser was used to create posterior stromal ablations at varying depths, producing donor lenticules 150 to 200 microm thick with diameters of 7.0 to 9.5 mm (n = 40). After stromal ablation, the central corneal thickness was measured by anterior segment optical coherence tomography and the diameters were measured using imaging software. RESULTS: The mean deviation from the attempted thickness was 15 +/- 14 microm. No correlation was found between the preoperative corneal thickness and the accuracy of the laser ablation (P = .91). No statistically significant differences were found in the accuracy of the laser ablation with multiple-pass nomograms (P = .15). The laser was accurate in producing circular diameters with an arc length between 7.0 mm and 9.5 mm (r2 = 0.935, P = .001). CONCLUSION: The femtosecond laser produced posterior stromal ablations that were accurate in depth of ablation and circularity.

Femtosecond laser-assisted endothelial keratoplasty: a laboratory model.

PURPOSE: To evaluate the ability of a 40-kHz femtosecond laser in performing posterior stromal ablation for endothelial keratoplasty. METHODS: Human corneoscleral rims were mounted on an artificial anterior chamber. After corneal pachymetry, the femtosecond laser was used to create a donor lenticule by using a variety of diameter ablations, 150 microm from the Descemet membrane. After ablation, the donor lenticule was peeled from the posterior surface and examined under light and scanning electron microscopy. Grading of ease of peeling and removing of the donor lenticule was assessed. RESULTS: The 40-kHz laser was able to produce effective dissection at low power in the posterior stroma. Modification of laser parameter settings was needed to improve the quality of stromal bed ablation. Double pass ablation of the bed significantly improved ease of peeling and removing of the donor lenticule. This was corroborated by smoother ablations on light and scanning electron microscopy. However, multiple pass ablations did not improve vertical rim dissections, which were satisfactory when single passes were used. CONCLUSIONS: Femtosecond laser-assisted endothelial keratoplasty is a viable alternative to microkeratome-assisted endothelial keratoplasty. Customized nomograms are needed for deep stromal ablation.

Risk factors for contact lens-related fusarium keratitis: a case-control study in Singapore.

OBJECTIVE: To evaluate the specific contact lens-related or other factors that may contribute to the outbreak of Fusarium keratitis. METHODS: A case-control study was conducted of Fusarium keratitis in contact lens users in Singapore from March 1, 2005, to May 31, 2006, and included 61 patients with Fusarium keratitis and 188 population-based and 179 hospital-based control subjects. Interviewers asked about contact lens solution use and other risk factors. RESULTS: Patients with Fusarium keratitis were more likely to use ReNu contact lens solutions (Bausch & Lomb, Rochester, NY) 58 [95.1%] of 61 cases) than were either population-based (62 [34.3%] of 181) or hospital-based (50 [30.1%] of 166) control subjects. After controlling for age, sex, contact lens hygiene, and other factors, the use of ReNu with MoistureLoc significantly increased the risk of Fusarium keratitis (odds ratio, 99.3; 95% confidence interval, 18.4-535.4; P<.001), and the risk was 5 times higher compared with the risk with use of ReNu MultiPlus, a multipurpose solution (odds ratio, 21.5; 95% confidence interval, 4.0-115.5; P<.001). CONCLUSIONS: The use of ReNu contact lens solutions significantly increased the risk of contact lens-related Fusarium keratitis in Singapore. Our data support the recall of ReNu MultiPlus from the Singapore market and the need for further investigations into the role of ReNu MultiPlus in the development of Fusarium keratitis in other populations.

Autologous cultivated conjunctival transplantation for pterygium surgery.

PURPOSE: To investigate the safety and efficacy of autologous cultivated conjunctival transplantation for the treatment of primary pterygium. DESIGN: Prospective nonrandomized clinical trial. METHODS: Forty patients with primary pterygium were recruited. Excision of the pterygium was followed by reconstruction using a serum-free derived autologous cultivated conjunctival equivalent in 22 patients (group A) and conventional denuded amniotic membrane transplantation in 18 patients (group B). In group A patients, conjunctival epithelial equivalents were constructed by the ex vivo expansion of conjunctival epithelial cells on human amniotic membranes (HAM). The main outcome measures were conjunctival epithelialization, recurrence, survival analysis, and incidence of complications. RESULTS: The mean follow-up was 14.1 +/- 3.9 months (range, 12 to 25 months). Complete epithelialization was achieved within five days after surgery in group A patients compared with approximately three weeks for group B patients. The proportion of patients that had true recurrences was 22.7% in group A and 25.0% in group B. The mean time to recurrence was 4.8 +/- 1.6 months in group A and 5.0 +/- 2.9 months in group B. No ocular complications were noted in group A, while one eye (6.0%) in group B developed scleral necrosis associated with a persistent epithelial defect. CONCLUSIONS: Transplantation of an autologous cultivated conjunctival epithelial sheet facilitated early postoperative epithelialization and recovery, and may aid in preventing serious complications associated with simple denuded HAM transplantation, such as scleral necrosis and secondary infection. This may provide a novel method for conjunctival epithelial replacement in the treatment of ocular surface disorders.