An in vitro investigation into the impact of corneal rinsing on riboflavin/UVA corneal cross-linking.

BACKGROUND: Corneal cross-linking (CXL) using riboflavin and ultraviolet-A light (UVA) is a treatment used to prevent progression of keratoconus. This ex vivo study assesses the impact on CXL effectiveness, as measured by tissue enzymatic resistance and confocal microscopy, of including a pre-UVA corneal surface rinse with balanced salt solution (BSS) as part of the epithelium-off treatment protocol. METHODS: Sixty-eight porcine eyes, after epithelial debridement, were assigned to six groups in three experimental runs. Group 1 remained untreated. Groups 2-6 received a 16-min application of 0.1% riboflavin/Hydroxypropyl methylcellulose (HPMC) drops, after which Group 3 was exposed to 9 mW/cm2 UVA for 10 min, and Groups 4-6 underwent corneal surface rinsing with 0.25 mL, 1 mL or 10 mL BSS followed by 9 mW/cm2 UVA exposure for 10 min. Central corneal thickness (CCT) was recorded at each stage. Central 8.0 mm corneal buttons from all eyes were subjected to 0.3% collagenase digestion at 37 °C and the time required for complete digestion determined. A further 15 eyes underwent fluorescence confocal microscopy to assess the impact of rinsing on stromal riboflavin concentration. RESULTS: Application of riboflavin/HPMC solution led to an increase in CCT of 73 ± 14 µm (P < 0.01) after 16 min. All CXL-treated corneas displayed a 2-4 fold greater resistance to collagenase digestion than non-irradiated corneas. There was no difference in resistance between corneas that received no BSS rinse and those that received a 0.25 mL or 1 mL pre-UVA rinse, but each showed a greater level of resistance than those that received a 10 mL pre-UVA rinse (P < 0.05). Confocal microscopy demonstrated reduced stromal riboflavin fluorescence after rinsing. CONCLUSIONS: All protocols, with and without rinsing, were effective at enhancing the resistance to collagenase digestion, although resistance was significantly decreased, and stromal riboflavin fluorescence reduced with a 10 mL rinse. This suggests that a 10 mL surface rinse can reduce the efficacy of CXL through the dilution of the stromal riboflavin concentration.

National survey of corneal cross-linking (CXL) practice patterns in the United Kingdom during 2019.

OBJECTIVE: To provide an insight into trends in corneal cross-linking (CXL) practice in the UK, including criteria for progression of corneal ectasia, identification of patients for CXL, the CXL procedure itself and post-operative management. METHODS: All ophthalmologist members of the UK Cross-linking (UK-CXL) Consortium were invited to complete an online survey about CXL practice for the year 2019. The data collected was anonymised by site and analysed with descriptive statistics. RESULTS: Responses were received from 16 individual CXL centres (16/38; 42% response rate) and the data represented ~2,000 CXL procedures performed in the UK in 2019. The commonest indication for CXL was progressive keratoconus. Between centres, there were variations in diagnostic evaluation, patient selection for CXL, the CXL procedure and the pre- and post-operative monitoring of patients. CONCLUSION: Consistent with the wide number of CXL treatment techniques described in the published literature world-wide, variations in the monitoring of corneal ectasia, indications for CXL, CXL practice and post-CXL follow-up were found to exist between UK-based CXL centres.

Returning to cataract surgery after a hiatus: a UK survey report.

OBJECTIVES: Cataract surgeons may periodically take time away from operating which can lead to skills fade. There is a paucity of research investigating the experiences of returning cataract surgeons and how different individual circumstances impact on their return. Our aim was to investigate the subjective experiences of UK ophthalmologists simultaneously returning to surgery following the nationwide elective surgical hiatus due to the Covid-19 pandemic. METHODS: An online survey was nationally distributed between 01/09/2020 and 29/10/2020 to registered UK ophthalmologists. Participants indicating a surgical hiatus of 8 weeks or more were included. RESULTS: 232 of 264 responses were analysed. Covid-19 was the most frequent reason for a surgical hiatus (median 15 weeks). Perceived operating difficulties were found in 29.1%. Transient anxiety (51.7%), reduced confidence, and perceived increased surgical time were commonplace. Trainees and females were more likely to encounter negative experiences (p < 0.001) and barriers to resource accessibility. Eyesi® and online videos were the most available and accessed pre-return resources. Childcare was five times more likely to present as a barrier to resource access for females than males. CONCLUSIONS: Technical skills fade such as capsulorhexis difficulties were commonly perceived by trainee surgeons in addition to transient anxiety, reported in more than half of all surgeons following a hiatus as short as 8 weeks. Eyesi® simulation offers the potential to negate technical de-skilling. Few had formal return plans or awareness of RCOphth guidance. We believe there is scope for more specialised and targeted support for future returning cataract surgeons thereby optimising patient care.

Effects of intraocular lens glistenings on visual function: a prospective study and presentation of a new glistenings grading methodology.

OBJECTIVE: To investigate the effect of intraocular lens (IOL) glistenings on visual performance and evaluate a new glistenings grading methodology. METHODS AND ANALYSIS: Thirty-four patients (34 eyes) were recruited. Corrected distance visual acuity (CDVA), mesopic gap acuity (MGA), functional contrast sensitivity (FCS) and forward light scatter were measured (Advanced Vision and Optometric Tests, City Occupational, London, UK). The IOL centre was imaged and glistenings density graded by three observers using the Miyata scale and a new system. Inter-rater reliability, association between the two grading scales, and correlations between glistenings grades and visual performance parameters were evaluated. RESULTS: The intraclass correlation coefficient between graders for the new grading system was 0.769 (95% Confidence Interval [CI] 0.636 to 0.868). There was a significant association between the Miyata scale and the new grading system for all graders (rs=0.533-0.895, p≤0.001). There was no association between CDVA or MGA and glistenings grade (rs=- 0.098, p=0.583 and rs=0.171, p=0.359, respectively). There was no association between FCS at mesopic light levels and glistenings grade (rs=-0.032, p=0.864), or the straylight parameter and glistenings grade (rs=0.021, p=0.916). No association was found between the integrated straylight parameter and glistenings grade (rs=0.078, p=0.701). CONCLUSION: The new glistenings grading scale was highly reproducible. In this cohort, glistenings in the same hydrophobic acrylic IOL after cataract surgery were not associated with changes in visual function, as assessed by a series of tests not previously used in glistenings research.

Risk-Adjusted CUSUM Analysis of the Learning Curve of Femtosecond Laser Assisted Cataract Surgery.

Objectives: To determine the length of the learning curve of femtosecond laser-assisted cataract surgery (FLACS) by a risk-adjusted cumulative sum method. Materials and Methods: This was a retrospective review of the first 288 FLACS performed by three surgeons over a 12-month period. The learning curves were analyzed separately for each surgeon and as pooled data via risk-adjusted cumulative sum methods. Change-point analysis was performed to estimate the length of the learning curve. Results: Rates of complications were as follows: anterior capsular tear (ACT) (3.4%), posterior capsular rupture (PCR) (0.7%), vitreous loss (0.3%), iris trauma (0.7%), Descemet's membrane tear (0.3%). There was a strong confidence level (96%) that there was a stable performance in terms of PCR after case 16 for the pooled data. Surgeon 1 did not have any cases of PCR, surgeons 2 and 3 exhibited change points at case 5 and 16, respectively (confidence levels = 99%, 98%). There was a strong confidence level (99.8%) that there was stable performance in terms of ACT after case 14 for the pooled data, however the individual surgeons demonstrated individual change points at case 1 (surgeon 1, confidence 99%), case 14 (surgeon 2, confidence 99%), and case 49 (surgeon 3, confidence 96%). Conclusions: The results suggest that there is an increased risk of ACT and PCR in FLACS within a surgeon's first 14 and 16 operations, respectively. Measures should be adopted to minimize harm to patients during this phase. However, overall rates of complications were safe.

Refractive surprise after routine cataract surgery with multifocal IOLs attributable to corneal epithelial basement membrane dystrophy.

We describe two patients in whom postsurgical refractive error occurred after routine refractive lens exchange cataract surgery with multifocal intraocular lens insertion most likely attributable to the presence of underlying corneal epithelial basement membrane dystrophy (EBMD). In Case 1, there was an unexpected hyperopic postoperative spherical equivalent refractive error of +1.50 diopters and in Case 2, a cylindrical refractive error of 2.75 diopter cylinder. We examine the possible causes of error and discuss potential management strategies to prevent and address these unpredictable postoperative outcomes. The importance of comprehensive and careful ocular surface assessment before cataract or refractive surgery as part of the presurgical workup is reemphasized. EBMD can be subtle and if overlooked, can affect the validity of biometric keratometric measurements preoperatively, resulting in an inaccurate biometry measurement, incorrect IOL selection, and reduced visual performance and patient satisfaction.

A randomized controlled trial comparing femtosecond laser-assisted cataract surgery versus conventional phacoemulsification surgery.

PURPOSE: To compare the clinical results of conventional phacoemulsification surgery (CPS) with femtosecond laser-assisted cataract surgery. SETTING: Guy's & St Thomas' NHS Foundation Trust, London, United Kingdom. DESIGN: Single-center prospective randomized interventional case-controlled trial. METHODS: Patients undergoing cataract surgery were randomized to receive either CPS or femtosecond laser-assisted cataract surgery. The surgery was performed with a femtosecond laser (Lensx), and all operations were performed with a gravity-fluidics torsional phacoemulsification machine (Infiniti). The visual acuity, refraction, central corneal thickness (CCT), central foveal thickness (CFT), endothelial cell loss, and rates of intraoperative and postoperative events were recorded. Quality of life outcomes were measured with the EuroQOL 5 dimensions questionnaire (EQ-5D) and patient-reported quality of vision was assessed with a cataract surgery patient-reported outcome measures questionnaire (Cat-PROM5). RESULTS: The study comprised 400 eyes of 400 patients who had CPS (n = 200) or femtosecond laser-assisted cataract surgery (n = 200). Seven patients (3.5%) in the femtosecond laser-assisted group were not able to complete the treatment and received CPS. The mean uncorrected distance visual acuity (logarithm of the minimum angle of resolution [logMAR]) 0.15 ± 0.21 (SD) and 0.15 ± 0.19 logMAR after CPS and femtosecond laser-assisted surgery, respectively (P = 1.0); the pinhole-corrected visual acuity was 0.04 ± 0.12 and 0.04 ± 0.12, respectively (P = 1.0); the increase in CCT was 13 ± 19 µm and 15 ± 25 µm, respectively (P = .5); and the endothelial cell loss was 9.7 ± 13.7 % and 10.2% ± 13.7, respectively (P = .76). The manifest refraction spherical equivalent error was -0.14 ± 0.60 diopters (D) after CPS and -0.12 ± 0.60 D after femtosecond laser-assisted surgery (P = .74); the mean change in CFT was 9 ± 35 µm and 6 ± 35 µm, respectively (P = .55); and the rate of posterior capsule rupture was 3% and 0%, respectively (P = .03). CONCLUSIONS: This study confirms the nonsignificant differences between 2 treatment modalities, notwithstanding a significant reduction in posterior capsule ruptures in the femtosecond laser-assisted surgery group.

Comparison of Standard Versus Accelerated Corneal Collagen Cross-Linking for Keratoconus: A Meta-Analysis.

Purpose: To systematically compare epithelial-off standard (SCXL) to accelerated corneal collagen cross-linking (ACXL) for the treatment of keratoconus. Methods: PubMed, Embase, the Cochrane Library, and the US trial registry were searched for trials comparing SCXL and ACXL for keratoconus up to October 2017. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Primary outcomes were changes in uncorrected distance visual acuity, maximum keratometry (Kmax), and mean keratometry (mean K). Secondary outcomes were changes in corrected distance visual acuity, mean refractive spherical equivalent, central corneal thickness (CCT), and endothelial cell density (ECD). Results: Eleven trials were included. For primary outcomes, SCXL showed a greater reduction in Kmax (SMD 0.32; 95% CI 0.16, 0.48) than ACXL. For secondary outcomes, the decrease in CCT (SMD 0.32; 95% CI 0.03, 0.61) and ECD (SMD 0.26; 95% CI 0.06, 0.46) was less with ACXL than with SCXL. For the other outcomes, there were no statistically significant differences. Conclusions: SCXL has a greater effect in terms of reduction in Kmax than ACXL, while ACXL induces less reduction in CCT and ECD than SCXL. Further well-designed randomized controlled trials comparing ACXL and SCXL are indicated.

Refractive outcomes after limbal relaxing incisions or femtosecond laser arcuate keratotomy to manage corneal astigmatism at the time of cataract surgery.

PURPOSE: To compare the results of manual limbal relaxing incisions (LRIs) performed during conventional phacoemulsification surgery with those of nonpenetrating femtosecond laser arcuate keratotomies performed during femtosecond laser-assisted cataract surgery to manage corneal astigmatism. SETTING: Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom. DESIGN: Randomized case-controlled trial. METHODS: This was a secondary outcome of a randomized controlled trial comparing 400 patients treated with conventional phacoemulsification surgery or femtosecond laser-assisted cataract surgery. All patients with corneal astigmatism greater than 0.9 diopter (D) were offered LRIs or femtosecond laser arcuate keratotomy based on the original randomization. Visual acuity, postoperative refraction, and corneal topography were recorded 4 weeks postoperatively. Vector analysis was performed using the Alpins method. RESULTS: Fifty-one eyes of 51 patients received LRIs, and 53 eyes of 53 patients received femtosecond arcuate keratotomies. The mean target induced astigmatism was 1.50 D and 1.38 D, respectively, with 1.02 D and 1.23 D surgically induced astigmatism (P = .21), resulting in the femtosecond arcuate keratotomy group having a smaller difference vector (1.17 D versus 0.89 D; P = .02) and a greater correction index (0.48 versus 0.73; P = .02). Forty-four percent of patients in the femtosecond arcuate keratotomy group and 20% in the LRI group attained a postoperative cylinder of less than 0.50 D (P = .01). CONCLUSIONS: The femtosecond arcuate keratotomy group achieved a higher correction index and a smaller difference vector. The femtosecond arcuate keratotomy patients showed less postoperative cylinder than LRI patients.

An Investigation of the Effects of Riboflavin Concentration on the Efficacy of Corneal Cross-Linking Using an Enzymatic Resistance Model in Porcine Corneas.

Purpose: To investigate riboflavin concentration on enzymatic resistance following corneal cross-linking (CXL). Methods: Ninety-six porcine eyes were divided into five groups in two treatment runs. Group 1 remained untreated. Group 2 received riboflavin 0.05%, group 3 riboflavin 0.1%, group 4 riboflavin 0.2%, and group 5 riboflavin 0.3%. Treated eyes underwent CXL with ultraviolet A at 9 mW/cm2 for 10 minutes. Eight-millimeter discs from each cornea were submerged in pepsin digest solution. In the first run, disc diameters were measured daily. After 10 days, dry weights were recorded from five samples in each group. In the second run, dry weights were recorded in five samples in each group at 10 and 20 days. Results: CXL-treated corneas took longer to digest than untreated (P < 0.001). Although eyes treated with higher riboflavin concentrations generally took longer to digest, there were no significant differences between groups (P = 0.3). Dry weights at 10 days demonstrated, with each increase in concentration, an increase in weight of residual undigested tissue (P < 0.001). In the second run, with each increase in riboflavin concentration there was an increase in weight of residual tissue (P < 0.001) at 10 days. At 20 days, the dry weight was lower with 0.05% riboflavin compared to 0.3% (P < 0.001) and 0.2% and 0.1% solutions (P < 0.05), with no other difference between groups. Conclusions: There is a consistent dose-response curve with higher concentrations of riboflavin achieving greater CXL efficacy, suggesting that manipulation of riboflavin dosage as well as the UVA protocol can be used to optimize CXL.

Evaluation of a hub-and-spoke model for the delivery of femtosecond laser-assisted cataract surgery within the context of a large randomised controlled trial.

AIMS: To test a hypothesis that cataract operating room (OR) productivity can be improved with a femtosecond laser (FL) using a hub-and-spoke model and whether any increase in productivity can offset additional costs relating to the FL. METHODS: 400 eyes of 400 patients were enrolled in a randomised-controlled trial comparing FL-assisted cataract surgery (FLACS) with conventional phacoemulsification surgery (CPS). 299 of 400 operations were performed on designated high-volume theatre lists (FLACS=134, CPS=165), where a hub-and-spoke FLACS model (1×FL, 2×ORs=2:1) was compared with independent CPS theatre lists. Details of operative timings and OR utilisation were recorded. Differences in productivity between hub-and-spoke FLACS and CPS sessions were compared using an economic model including testing hypothetical 3:1 and 4:1 models. RESULTS: The duration of the operation itself was 12.04±4.89 min for FLACS compared with CPS of 14.54±6.1 min (P<0.001). Total patient time in the OR was reduced from 23.39±6.89 min with CPS to 20.34±5.82 min with FLACS (P<0.001)(reduction of 3.05 min per case). There was no difference in OR turnaround time between the models. Average number of patients treated per theatre list was 9 for FLACS and 8 for CPS. OR utilisation was 92.08% for FLACS and 95.83% for CPS (P<0.001). Using a previously established economic model, the FLACS service cost £144.60 more than CPS per case. This difference would be £131 and £125 for 3:1 and 4:1 models, respectively. CONCLUSION: The FLACS hub-and-spoke model was significantly faster than CPS, with patients spending less time in the OR. This enabled an improvement in productivity, but insufficient to meaningfully offset the additional costs relating to FLACS.

Time and motion studies of National Health Service cataract theatre lists to determine strategies to improve efficiency.

AIM: To provide a quantitative assessment of cataract theatre lists focusing on productivity and staffing levels/tasks using time and motion studies. METHODS: National Health Service (NHS) cataract theatre lists were prospectively observed in five different institutions (four NHS hospitals and one private hospital). Individual tasks and their timings of every member of staff were recorded. Multiple linear regression analyses were performed to investigate possible associations between individual timings and tasks. RESULTS: 140 operations were studied over 18 theatre sessions. The median number of scheduled cataract operations was 7 (range: 5-14). The average duration of an operation was 10.3 min±(SD 4.11 min). The average time to complete one case including patient turnaround was 19.97 min (SD 8.77 min). The proportion of the surgeons' time occupied on total duties or operating ranged from 65.2% to 76.1% and from 42.4% to 56.7%, respectively. The correlations of the surgical time to patient time in theatre was R2=0.95. A multiple linear regression model found a significant association (F(3,111)=32.86, P<0.001) with R2=0.47 between the duration of one operation and the number of allied healthcare professionals (AHPs), the number of AHP key tasks and the time taken to perform these key tasks by the AHPs. CONCLUSIONS: Significant variability in the number of cases performed and the efficiency of patient flow were found between different institutions. Time and motion studies identified requirements for high-volume models and factors relating to performance. Supporting the surgeon with sufficient AHPs and tasks performed by AHPs could improve surgical efficiency up to approximately double productivity over conventional theatre models.

Cost-Effectiveness Analysis of Corneal Collagen Crosslinking for Progressive Keratoconus.

PURPOSE: To evaluate the cost effectiveness of corneal collagen crosslinking (CXL) for progressive keratoconus from the healthcare payer's perspective. DESIGN: A probabilistic Markov-type model using data from published clinical trials and cohort studies. PARTICIPANTS: Two identical cohorts, each comprising 1000 virtual patients with progressive bilateral keratoconus, were modeled; one cohort underwent CXL and the other cohort received no intervention. METHODS: Both cohorts were modeled and evaluated annually over a lifetime. Quality-adjusted life years (QALYs), total cost, disease progression, and the probability of corneal transplantation, graft failure, or both were calculated based on data from published trials and cohort studies. These outcomes were compared between the 2 cohorts. In our base scenario, the stabilizing effect of CXL was assumed to be 10 years; however, longer durations also were analyzed. One-way sensitivity analyses were performed to test the robustness of the outcomes. MAIN OUTCOME MEASURE: Incremental cost-effectiveness ratio (ICER), defined as euros per QALY. RESULTS: Assuming a 10-year effect of CXL, the ICER was €54 384/QALY ($59 822/QALY). When we adjusted the effect of CXL to a lifelong stabilizing effect, the ICER decreased to €10 149/QALY ($11 163/QALY). Other sensitivity and scenario analyses that had a relevant impact on ICER included the discount rate, visual acuity before CXL, and healthcare costs. CONCLUSIONS: Corneal collagen crosslinking for progressive keratoconus is cost effective at a willingness-to-pay threshold of 3 times the current gross domestic product (GDP) per capita. Moreover, a longer stabilizing effect of CXL increases cost effectiveness. If CXL had a stabilizing effect on keratoconus of 15 years or longer, then the ICER would be less than the 1 × GDP per capita threshold and thus very cost effective.

Corneal collagen crosslinking for corneal ectasias: a review.

PURPOSE: To review the published literature on corneal collagen crosslinking (CXL). METHODS: Importance has been placed on seminal publications, systemic reviews, meta-analyses, and randomized controlled clinical trials. Where such evidence was not available, cohort studies, case-controlled studies, and case series with follow-up greater than 12 months were examined. RESULTS: Corneal collagen crosslinking with riboflavin and ultraviolet A (UVA) 370 nm radiation appears to be capable of arresting the progression of ectatic corneal disorders, with most studies reporting significant improvements in visual, keratometric, and topographic measurements. Its mode of action at the molecular level is undetermined. Follow-up is limited to 5-10 years but suggests sustained stability and enhancement in corneal shape with time. Nearly all published long-term data and comparative studies are with epithelium-off techniques. Epithelium-on investigations suggest some efficacy but less than with epithelium-off treatments and long-term data are unavailable. Accelerated techniques with higher UVA fluencies and shorter treatments times, delivering the same UVA energy dosage, are the subject of recent investigation, with some laboratory and clinical studies suggesting reduced efficacy compared to the standard 3 mW/cm2 for 30 minutes irradiation procedure. Combined methodologies of CXL with techniques such as photorefractive keratectomy and intrastromal rings show promise but long-term follow-up is indicated. Sight-threatening complications of CXL are rare. CONCLUSIONS: Studies of epithelium-off CXL with irradiation at 3 mW/cm2 for 30 minutes support its efficacy. Refinement in techniques may allow for safer and more rapid procedures with less patient discomfort but require further investigation.

An investigation into corneal enzymatic resistance following epithelium-off and epithelium-on corneal cross-linking protocols.

The aim of this study was to investigate corneal enzymatic resistance following epithelium off and on riboflavin/UVA cross-linking (CXL). One hundred and fourteen porcine eyes were divided into four non-irradiated control groups and seven CXL groups. The latter comprised; (i) epithelium-off, 0.1% iso-osmolar riboflavin, 9 mW UVA irradiation for 10 min, (ii) disrupted epithelium, 0.1% hypo-osmolar riboflavin, 9 mW UVA for 10 min, (iii) epithelium-on, 0.25% hypo-osmolar riboflavin with 0.01% benzylalkonium chloride (BACS), 9 mW UVA for 10 min, (iv) epithelium-on, 5 min iontophoresis at 0.1 mA for 5 min with 0.1% riboflavin solution, 9 mW UVA for 10 min or (v) 12.5 min, (vi) epithelium-on, prolonged iontophoresis protocol of 25 min with 1.0 mA for 5 min and 0.5 mA for 5 min with 0.25% riboflavin with 0.01% BACS, 9 mW UVA for 10 min or (vii) 12.5 min. Enzymatic resistance was assessed by daily measurement of a corneal button placed in pepsin solution and measurement of corneal button dry weight after 11 days of digestion. This study revealed that the enzymatic resistance was greater in CXL corneas than non-irradiated corneas (p < 0.0001). Epithelium-off CXL showed the greatest enzymatic resistance (p < 0.0001). The prolonged iontophoresis protocol was found to be superior to all other trans-epithelial protocols (p < 0.0001). A 25% increase in UVA radiance significantly increased corneal enzymatic resistance (p < 0.0001). In conclusion, although epithelium-on CXL appears to be inferior to epithelium-off CXL in terms of enzymatic resistance to pepsin digestion, the outcome of epithelium-on CXL may be significantly improved through the use of higher concentrations of riboflavin solution, a longer duration of iontophoresis and an increase in UVA radiance.

Sixteen-year follow-up of hyperopic laser in situ keratomileusis.

PURPOSE: To assess the long-term efficacy and safety of hyperopic laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. DESIGN: Prospective cohort study. METHODS: Hyperopic LASIK was performed using a mechanical microkeratome, an optical zone of 6.5 mm, and a blend zone of 1.5 mm. Simple hyperopia was treated. RESULTS: The mean patient age was 51.6 years (range 34 to 60 years). Preoperatively, the mean spherical equivalent (SE) was +3.74 diopters (D) (range +1.25 to +6.50 D). The mean attempted correction was +3.64 D (range +1.5 to +6.0 D). The mean follow-up was 16.5 years. The mean SE was +0.28 D (range -1.0 to +1.5 D) at 12 months, +0.84 D (range -0.75 to +3.35 D) at 5 years, and +1.74 D (range -0.75 to +4.13 D) at 16 years, representing an increase in hyperopia of +1.47 D ± 1.43 (SD) between 1 year and 16 years (P < .0001) and of +1.13 ± 0.8 D between 5 years and 16 years (P < .03). The uncorrected distance visual acuity improved at 16 years (P < .0001); corrected distance visual acuity (CDVA) was unchanged (P < .2). The efficacy index was 0.5 and the safety index, 1.09. One eye (3%) lost 2 lines of CDVA. Keratometry remained stable between 1 year and 16 years (P < 1.0). Four eyes (12%) had cataract surgery, and 2 (6%) had laser iridotomy. There was no ectasia. CONCLUSIONS: After hyperopic LASIK, an increase in hyperopia occurred between 1 and 5 years and 16 years. At 16 years, efficacy was limited but with no sight-threatening complications. FINANCIAL DISCLOSURES: Dr. Marshall was a consultant to Summit Technology, Inc. Dr. O'Brart holds a noncommercial research grant from Alcon Laboratories, Inc. None of the other authors has a financial or proprietary interest in any material or method mentioned.

Enzymatic Resistance of Corneas Crosslinked Using Riboflavin in Conjunction With Low Energy, High Energy, and Pulsed UVA Irradiation Modes.

PURPOSE: To investigate the effect of various riboflavin/ultraviolet light (UVA) crosslinking (CXL) protocols on corneal enzymatic resistance. METHODS: A total of 66 enucleated porcine eyes, with the corneal epithelium removed, were divided into 6 groups. Group 1 remained untreated. Groups 2 to 6 received riboflavin/dextran for 30 minutes. Group 3 underwent standard CXL (SCXL) with 3 mW/cm(2) UVA for 30 minutes (total energy dose 5.4 J/cm(2)). Groups 4 and 5 underwent high intensity CXL (HCXL) using 30 mW/cm(2) UVA for 3 minutes (5.4 J/cm(2)) and 30 mW/cm(2) for 4 minutes (7.2 J/cm(2)), respectively. Group 6 was exposed to 8 minutes of 30 mW/cm(2) UVA in a 10-second on/10-second off pulsed-radiation mode (p-HCXL; 7.2 J/cm(2)). A central 8-mm disk from each cornea was submerged in pepsin digest solution at 23°C and measured daily. After 13 days, the dry weight was recorded from 5 samples in each group. RESULTS: The CXL-treated corneas took longer to digest than nonirradiated corneas (P < 0.0001). Differences in digestion time also were observed between CXL groups, such that, HCXL (5.4 J/cm(2)) < SCXL (5.4 J/cm(2)) < HCXL (7.2 J/cm(2)) < p-HCXL (7.2 J/cm(2); P < 0.0001). The dry weight of the SCXL (5.4 J/cm(2)) group was higher than the HCXL (5.4 and 7.2 J/cm(2); P < 0.001) and p-HCXL 7.2 J/cm(2) (P <0.05) groups. No difference was detected between the HCXL and p-HCXL 7.2 J/cm(2) groups. CONCLUSIONS: The intensity and distribution of the crosslinks formed within the cornea vary with different UVA protocols. The precise location and amount of crosslinking needed to prevent disease progression is unknown.

Eighteen-year follow-up of hyperopic photorefractive keratectomy.

PURPOSE: To investigate the long-term efficacy of hyperopic photorefractive keratectomy (PRK). SETTING: University Hospital, London, United Kingdom. DESIGN: Prospective case series. METHODS: Patients with a follow-up of 18 years ± 0.7 (SD) attended for examination. All had spherical corrections with a 6.5 mm optical zone and 1.5 mm blend zone. RESULTS: Twenty-five patients (45 eyes) were included. The mean preoperative spherical equivalent (SE) refractive error was +4.11 ± 1.8 diopters (D) (range +1.125 to +7.25 D). Between 1 year and 18 years, in eyes that had no cataract surgery (n = 34), there was a +1.14 ± 1.48 D increase in the mean SE (P < .0002). The increase between 7.5 years and 18.0 years did not reach clinical significance (P = .1). Uncorrected distance visual acuity improved at 18 years (P < .02). Corrected distance visual acuity (CDVA) was reduced (P < .001). The efficacy index was 0.47, and the safety index was 0.83. Six eyes (18%) lost 2 lines of CDVA, of which 4 eyes had preexisting cataract. Keratometry remained stable between 1 year and 18 years (P = .2). Forty percent still had traces of peripheral haze, and 4 (9%) had Salzmann-like changes. Eleven eyes (24%) had cataract surgery and 4 (9%) had laser iridotomy. There was no evidence of ectasia. CONCLUSIONS: Hyperopic PRK showed an increase in hyperopic SE between 1.0 year and 7.5 years but was generally stable thereafter. The efficacy was limited. Peripheral haze was evident in 40% of cases with Salzmann-like changes in some. Ocular comorbidity in relationship to cataract was common and reduced CDVA. FINANCIAL DISCLOSURE: Dr. Marshall was a consultant to Summit Technology, Inc. No author has a financial or proprietary interest in any material or method mentioned.