Corneal Collagen Crosslinking for Post-LASIK Ectasia: An Australian Study.

PURPOSE: Post laser-assisted in situ keratomileusis (LASIK) ectasia is a rare and unpredictable complication after LASIK. Corneal collagen crosslinking (CXL) has emerged as a promising technique to address this complication. Our study evaluates the long-term efficacy of CXL for post-LASIK ectasia in an Australian setting. DESIGN: Retrospective review of post-LASIK ectasia patients referred to and treated at 3 corneal refractive surgery institutions in Sydney, Australia. METHODS: Eleven patients (14 eyes; mean age, 39.7 ± 12.6 years) underwent epithelium-off CXL with follow-up ranging from 12-78 months. Best spectacle-corrected visual acuity (BSCVA), simulated keratometry, corneal topography indices, and higher-order aberrations (HOAs) [mean ± standard error of the mean (SEM)] were measured with a rotating Scheimpflug camera (Pentacam, Oculus). Comparisons between baseline measurements and postoperative outcomes were performed using paired t test analysis. RESULTS: At last follow-up, BSCVA improved significantly by 0.2 ± 0.06 logMAR (P = 0.01), and 12 of 14 eyes showed no keratometric deterioration. Of the corneal topography indices, index of height asymmetry showed a trend toward a significant improvement (P = 0.05). There was no progression of corneal HOAs. Central corneal thickness was not significantly altered (P = 0.6). No major postoperative complications were observed. CONCLUSIONS: In the Australian setting, CXL has proven effective at stabilizing the progression of post-LASIK ectasia, inducing corneal regularity, and improving visual acuity.

SMILE Rescue: Delayed Lenticule Removal in a Patient With High Myopia.

PURPOSE: To report successful stromal lenticule extraction, 18 weeks after an aborted small incision lenticule extraction (SMILE) procedure. METHODS: Case report. RESULTS: SMILE was planned in both eyes in another center to correct high myopia. The right eye was treated uneventfully with immediate lenticule extraction and normal postoperative corneal and topographic appearance. Femtosecond laser treatment was applied to the left eye, but the lenticule could not be removed and the procedure was aborted. Eighteen weeks later, lenticule extraction was attempted again with success. Uncorrected distance visual acuity improved from counting fingers to 20/15, with a successful refractive outcome as planned. CONCLUSIONS: Delayed lenticule extraction was successful in achieving the target refractive outcome. To the authors' knowledge, this is the first case of successful delayed lenticule extraction following an incomplete SMILE procedure. Target refractive outcomes were achieved and there were no postoperative complications. [J Refract Surg. 2017;33(3):199-202.].

Relationship of Structural Characteristics to Biomechanical Profile in Normal, Keratoconic, and Crosslinked Eyes.

PURPOSE: To evaluate the correlation of corneal biomechanical parameters with structural characteristics in normal, keratoconic, and collagen crosslinked eyes. METHODS: A prospective observational study that included 50 normal, 100 keratoconic, and 25 crosslinked eyes. All eyes were imaged using a Scheimpflug camera and an ocular response analyzer. The main outcome measures analyzed were central corneal thickness (CCT), corneal volume (CV), maximal keratometry (Kmax), corneal hysteresis (CH), and corneal resistance factor (CRF). RESULTS: Significant differences were noted among all 3 groups of eyes for CCT, CV, Kmax, CH, and CRF values (P < 0.05 by analysis of variance). CH and CRF correlated negatively (CH, r = -0.40; CRF, r = -0.44; both P < 0.0001) with the Pentacam topographic keratoconus classification. Both CH and CRF correlated positively with CCT and CV for the normal, keratoconic, and crosslinked eyes. In contrast, significant negative correlations were observed between CH, CRF, and Kmax in the keratoconic eyes (CH, r = -0.43; CRF, r = -0.53; both P < 0.0001), whereas no association was noted for the normal and crosslinked eyes. CONCLUSIONS: CH and CRF are influenced by the corneal structure, with higher values noted in corneas with greater thickness and volume. Corneal biomechanical parameters progressively decrease as the severity of keratoconus increases. After collagen crosslinking, the relationship of the corneal curvature to the biomechanical profile is similar to normal eyes.

Comparative analysis of corneal measurements obtained from a Scheimpflug camera and an integrated Placido-optical coherence tomography device in normal and keratoconic eyes.

PURPOSE: To assess the agreement between a Scheimpflug camera (Pentacam) and a combined Placido-optical coherence tomography device (Visante OMNI) in measuring corneal curvature, thickness and elevation values in normal and keratoconic eyes. METHODS: Corneal measurements of 110 normal eyes (one eye per subject) and 70 keratoconic eyes were obtained from both devices and compared. Agreement was determined using the Bland-Altman analysis 95% limits of agreement (LoA). RESULTS: The Pentacam measured significantly greater keratometry readings in the flattest (K1) and steepest meridians (K2) in normal and keratoconic eyes. The 95% LoA in normal eyes were -0.32 to 0.59 dioptres (D) (K1) and -0.41 to 0.74 D (K2). In keratoconic eyes, the 95% LoA were -1.35 to 1.92 D (K1) and -1.38 to 1.99 D (K2). The Pentacam recorded significantly higher central corneal thickness (CCT) values in both groups of eyes. The 95% LoA were -4.31 to 39.89 microns (µ) and -12.92 to 41.35 µ in normal and keratoconic eyes, respectively. Pentacam anterior and posterior corneal elevations were significantly greater in both groups of eyes. The devices demonstrated excellent repeatability and reproducibility for corneal curvature and thickness but not elevation measurements. CONCLUSIONS: The Pentacam measured significantly greater corneal curvature, thickness and elevation values compared to the Visante OMNI in normal and keratoconic eyes. The devices agree moderately for anterior corneal elevations in normal eyes and do not appear to be interchangeable for corneal measurements in clinical practice.

Outcome of corneal collagen crosslinking for progressive keratoconus in paediatric patients.

PURPOSE: To evaluate the efficacy of corneal collagen crosslinking for progressive keratoconus in paediatric patients. METHODS: This prospective study included 25 eyes of 18 patients (aged 18 years or younger) who underwent collagen crosslinking performed using riboflavin and ultraviolet-A irradiation (370 nm, 3 mW/cm2, 30 min). RESULTS: The mean patient age was 14.3±2.4 years (range 8-17) and mean followup duration was 20.1±14.25 months (range 6-48). Crosslinked eyes demonstrated a significant reduction of keratometry values. The mean baseline simulated keratometry values were 46.34 dioptres (D) in the flattest meridian and 50.06 D in the steepest meridian. At 20 months after crosslinking, the values were 45.67 D (P=0.03) and 49.34 D (P=0.005), respectively. The best spectacle corrected visual acuity (BSCVA) and topometric astigmatism improved after crosslinking. Mean logarithm of the minimum angle of resolution (logMAR) BSCVA decreased from 0.24 to 0.21 (P=0.89) and topometric astigmatism reduced from mean 3.50 D to 3.25 D (P=0.51). CONCLUSIONS: Collagen crosslinking using riboflavin and ultraviolet-A is an effective treatment option for progressive keratoconus in paediatric patients. Crosslinking stabilises the condition and, thus, reduces the need for corneal grafting in these young patients.

Polymicrobial keratitis after a collagen cross-linking procedure with postoperative use of a contact lens: a case report.

PURPOSE: : To report a case of polymicrobial keratitis caused by Streptococcus salivarius, Streptococcus oralis, and coagulase-negative Staphylococcus sp. in a patient who underwent collagen cross-linking for keratoconus. METHOD: : Case report. RESULT: : A 32-year-old male presented with a 1-day history of a painful red eye, occurring 3 days after he had undergone a collagen cross-linking with riboflavin and UV-A on his left eye for keratoconus. He admitted to removing his bandage contact lens and cleaning it in his mouth before reapplying it in his eye. On presentation, a severe keratitis with an 8-mm epithelial defect and 360-degree ring infiltrate was found. Culture results from his contact lens were positive for S. salivarius and S. oralis, and coagulase-negative Staphylococcus sp. were grown from his corneal scrapings. CONCLUSIONS: : Collagen cross-linking is a promising procedure for the treatment of progressive keratoconus with minimal reported side effects. However, the possibility of a secondary infection after the procedure exists because the patient is subjected to epithelial debridement and the application of a soft contact lens. The role of the UV light on the immune mechanisms of the cornea and its effect on corneal wound healing warrant further investigation.

Corneal perforation associated with pellucid marginal degeneration and treatment with crescentic lamellar keratoplasty: two case reports.

PURPOSE: To describe 2 cases of corneal perforation associated with pellucid marginal degeneration (PMD) and subsequent successful management with crescentic lamellar keratoplasty. METHODS: Two cases are discussed along with the relevant literature. RESULTS: Both patients presented with spontaneous corneal perforations and associated features consistent with PMD. In both cases, there was fellow eye evidence of PMD, and 1 of the patients was already known to our unit with this diagnosis. Initial conservative measures were unsuccessful, and both patients underwent crescentic lamellar keratoplasty as the definitive surgical management with a good visual outcome. CONCLUSIONS: Crescentic lamellar keratoplasty is an effective technique for the management of this rare complication of PMD.

Diffuse lamellar keratitis associated with gonococcal keratoconjunctivitis 3 years after laser in situ keratomileusis.

A 29-year-old man presented with a 5-day history of a red eye with a purulent discharge. Three years previously, he had undergone laser in situ keratomileusis elsewhere. A diagnosis of gonococcal keratoconjuntivitis was made clinically and confirmed with culture. The patient subsequently developed diffuse lamellar keratitis (DLK). The keratoconjunctivitis and DLK resolved with antibiotic therapy and topical steroids. The cause and effect relationship of these 2 uncommon events is of interest.

Recovery from macular phototoxicity after corneal triple procedure.

PURPOSE: Visual recovery from macular phototoxicity in 2 cases after prolonged exposure to operating microscope light from uncomplicated corneal triple-procedure surgery. Recovery is discussed in the context of repair and regeneration. METHODS: Retrospective case reports. RESULTS: Immediately postoperatively, both patients reported positive scotomata and were found to have macular retinal pigment epithelial depigmentation. In 1 case, the fovea was involved. By 6 to 12 months, the scotomata had disappeared despite large areas of retinal pigment epithelial hyperpigmentation remaining. CONCLUSION: Recovery from macular phototoxicity occurs, although the mechanism remains unclear. Positive scotomata in these cases resolved over several months. The time scale of recovery was consistent with the time required for cellular replacement and possible differentiation from neural progenitor cells.

Six-year review of Acanthamoeba keratitis in New South Wales, Australia: 1997-2002.

AIM: To assess the incidence and risk factors for Acanthamoeba keratitis (AK), the diagnostic interval, and the efficacy and outcome of current treatment among the population of New South Wales, Australia. METHODS: A retrospective review was carried out of all cases of AK treated at the Sydney Eye Hospital between January 1997 and December 2002. RESULTS: Twenty patients were identified with a mean follow up of 24.8 +/- 21.5 months. Acanthamoeba keratitis constitutes 4.7% of severe infective keratitis treated at Sydney Eye Hospital. The mean interval from first presentation to diagnosis was 26.6 +/- 35.1 days overall; 17.2 +/- 33.1 days for those presenting directly to our unit (69% being diagnosed within 72 h of presentation), and 44.1 +/- 34.0 days for those first presenting elsewhere. Of those with a diagnostic delay >1 month, 57% had been mistakenly diagnosed with Herpes simplex keratitis. Sixteen (80%) wore contact lenses, and eight (40%) had additional risk factors including poor lens hygiene. Complications occurred in 16 (80%), with seven (35%) requiring surgical intervention. Visual acuity improved in 18 (90%), worsened in two patients (10%), and 75% achieved 6/12 or better at last follow up. CONCLUSIONS: Acanthamoeba keratitis is a rare infection, and contact lens wear remains the commonest association, with poor hygiene constituting significant additional risk. The visual outcome has improved with the availability of effective amoebicidal agents, but patients with a diagnostic delay and non-contact lens wearers are at increased risk of recurrent disease. A high index of clinical suspicion remains the most effective strategy in implementing early treatment, and enabling a favourable outcome.