Samir A. Melki

LASIK complications: Etiology, management, and prevention

Laser in situ keratomileusis (LASIK) is a rapidly evolving ophthalmic surgical procedure. Several anatomic and refractive complications have been identified. Anatomic complications include corneal flap abnormalities, epithelial ingrowth, and corneal ectasia. Refractive complications include unexpected refractive outcomes, irregular astigmatism, decentration, visual aberrations, and loss of vision. Infectious keratitis, dry eyes, and diffuse lamellar keratitis may also occur following LASIK. By examining the etiology, management, and prevention of these complications, the refractive surgeon may be able to improve visual outcomes and prevent vision-threatening problems. Reporting outcomes and mishaps of LASIK surgery will help refine our approach to the management of emerging complications.

Late traumatic dislocation of laser in situ keratomileusis corneal flaps

PURPOSE To report the management and outcome of late-onset traumatic dislocation of laser in situ keratomileusis (LASIK) flaps. DESIGN Retrospective, observational case series. PARTICIPANTS Four patients with late-onset LASIK flap dislocation occurring after mechanical trauma at various intervals (10 days-2 months) after the procedure. INTERVENTION In all cases of postoperative traumatic LASIK flap dislocation, the flap was refloated with scraping and irrigation of the underlying stromal bed within 12 hours of the injury. A bandage contact lens was placed, and a regimen including topical antibiotics and corticosteroids was instituted in all cases. MAIN OUTCOME MEASURES Best spectacle-corrected visual acuity and complications associated with the surgery were monitored. RESULTS Postoperative follow-up ranged from 4 to 21 months. Nonprogressive epithelial ingrowth was noted in one patient and diffuse lamellar keratitis developed in another patient. All patients recovered pretrauma spectacle-corrected visual acuity. CONCLUSIONS Corneal LASIK flaps are prone to mechanical dislocation as late as 2 months after the procedure. Appropriate management results in recovery of optimal visual outcomes.

Evaluation of umbilical cord serum therapy for persistent corneal epithelial defects

Aims: To evaluate umbilical cord serum therapy as a means of promoting the healing of persistent corneal epithelial defects. Methods: Umbilical cord serum or autologous serum drops were used to promote the healing of persistent epithelial defects. The study design was a prospective randomised controlled clinical trial. 60 eyes of 59 patients were divided into two groups, 31 in the cord serum group and 29 in the autologous serum control group. Epithelial defects measuring at least 2 mm in linear dimension resistant to conventional medical management were included. Serial measurements of the size of the epithelial defects—namely, two maximum linear dimensions perpendicular to each other, and the area and perimeter was done at start of therapy and follow up days 3, 7, 14, 21. Rate of healing of the epithelial defects were measured as percentage decrease from the baseline parameter at each subsequent follow up. The data were analysed by the non-parametric Wilcoxon rank sum test using STATA 7.0. Results: The median percentage decrease in the size of the epithelial defect was significantly greater in the cord serum group at days 7, 14 and 21 (p<0.05) when measured in terms of the area and perimeter. A greater number of patients showed complete re-epithelialisation with umbilical cord serum (n = 18) than with autologous serum (n = 11) (Pearson χ = 0.19). None of the patients reported any side effects or discomfort with either treatment. Conclusions: Umbilical cord serum leads to faster healing of the persistent corneal epithelial defects refractory to all medical management compared to autologous serum.

Collagen Cross-Linking Using Rose Bengal and Green Light to Increase Corneal Stiffness

PURPOSE Photochemical cross-linking of corneal collagen is an evolving treatment for keratoconus and other ectatic disorders. We evaluated collagen cross-linking by rose bengal plus green light (RGX) in rabbit eyes and investigated factors important for clinical application. METHODS Rose bengal (RB, 0.1%) was applied to deepithelialized corneas of enucleated rabbit eyes for 2 minutes. The diffusion distance of RB into the stroma was measured by fluorescence microscopy on frozen sections. RB-stained corneas were exposed to green (532-nm) light for 3.3 to 9.9 minutes (50-150 J/cm(2)). Changes in the absorption spectrum during the irradiation were recorded. Corneal stiffness was measured by uniaxial tensiometry. The spatial distribution of the stromal elastic modulus was assessed by Brillouin microscopy. Viable keratocytes were counted on H&E-stained sections 24 hours posttreatment. RESULTS RB penetrated approximately 100 μm into the corneal stroma and absorbed >90% of the incident green light. RGX (150 J/cm(2)) increased stromal stiffness by 3.8-fold. The elastic modulus increased in the anterior approximately 120 μm of stroma. RB was partially photobleached during the 2-minute irradiation, but reapplication of RB blocked light transmission by >70%. Spectral measurements suggested that RGX initiated cross-linking by an oxygen-dependent mechanism. RGX did not decrease keratocyte viability. CONCLUSIONS RGX significantly increases cornea stiffness in a rapid treatment (≅12 minutes total time), does not cause toxicity to keratocytes and may be used to stiffen corneas thinner than 400 μm. Thus, RGX may provide an attractive approach to inhibit progression of keratoconus and other ectatic disorders.

Intraocular Pressure Measurement by Radio Wave Telemetry

PURPOSE To determine the biocompatibility of a new wireless intraocular pressure (IOP) transducer (WIT) in rabbit eyes and to correlate its measurements with other pressure-measuring devices. METHODS The WIT is a ring-shaped intraocular device that allows wireless IOP measurements through radiofrequency. It was implanted into six eyes of New Zealand White rabbits after extracapsular lens extraction. A sham rabbit eye with no transducer implanted was used as a control. The animals were observed and examined by microscopy at various intervals up to 25 months after surgery. IOP was measured at various intervals by pneumotonometry, tonometry, WIT, and manometry. The data from the various devices were compared and analyzed for reproducibility. Two eyes were enucleated at 5.5 and 20 months after implantation and analyzed by histology. RESULTS The WIT appears to be well tolerated in the rabbit eye, with no evidence of significant inflammation or scar formation by microscopic in vivo examination. Histology did not reveal intraocular inflammation or membrane formation. Repeated IOP measurements with pneumotonometry, tonometry, and the WIT resulted in SDs of 2.70 mm Hg, 3.35 mm Hg, and 0.81 mm Hg, respectively. The concordance between the WIT and direct manometry measurements was high. A downward drift in IOP measured by the WIT was noted in three rabbits, necessitating recalibration. CONCLUSIONS The WIT is well tolerated by the rabbit eye. Its measurements are reproducible and in close concordance with manometry. A downward IOP drift warrants further investigation.

Potential acuity pinhole: A simple method to measure potential visual acuity in patients with cataracts, comparison to potential acuity meter

OBJECTIVE To describe the potential acuity pinhole (PAP) test and compare its accuracy to the potential acuity meter (PAM) in predicting visual outcome after cataract surgery. STUDY DESIGN Prospective case series. PARTICIPANTS A total of 56 preoperative patients with cataracts participated. MAIN OUTCOME MEASURES Accuracy of predicting postoperative distance visual acuity was measured. METHODS Lines of inaccuracy were calculated by subtracting actual postoperative best-corrected distance visual acuity (BCVA) from predicted values. Variables analyzed were method of prediction, preoperative BCVA, and preoperative spherical equivalent. RESULTS The PAP test predicted visual outcomes within 2 lines in 100%, 100%, and 56% of eyes with preoperative BCVA of 20/50 and better (group 1), 20/60 to 20/100 (group II), and 20/200 and worse (group III), respectively. The PAM predictions within 2 lines for the same groups were 42%, 47%, and 0%, respectively. Mean lines of inaccuracy of PAP predictions were 0.83, 1.11, and 3.50 lines for groups I, II, and III, respectively. Mean lines of inaccuracy for PAM predictions were 2.50, 2.68, and 6.22 lines for the same groups. Differences in lines of prediction between PAM and PAP were 1.67 (P = 0.004), 1.58 (P = 0.0002), and 2.72 lines (P = 0.0001) for groups I, II, and III, respectively. There was no statistically significant correlation between PAP predictions and preoperative myopic spherical equivalent. CONCLUSIONS The PAP test is a simple, inexpensive, and relatively reliable method to estimate visual outcome after uncomplicated cataract surgery in eyes with no coexisting disease. It is less accurate in patients with preoperative BCVA worse than 20/200. It appears to be more predictive than PAM.

Pterygium: current concepts in pathogenesis and treatment.

A pterygium is a commonly occurring ocular surface disorder, named for its resemblance to an insect wing. The multitude of treatment options currently advocated and practiced in different parts of the world is characterized by the absence of a universal approach. However, some of the traditional methods of treatment, such as bare sclera technique have fallen out of favor because of high recurrence rates (19.4% to 75%). Other adjunctive therapies, such as b-irradiation and postoperative topical mitomycin-C, have also become less popular because of cost, operational issues or occurrence of serious complications such as scleral necrosis and intraocular infections. In recent years, new modalities of treatment have included conjunctival autografts (CAs), amniotic membrane transplantation (AMT) and fibrin glue instead of sutures. The purpose of this article is to present a summary of the currently advocated treatment options from a review of the recent literature.

Laser in situ keratomileusis buttonhole: Classification and management algorithm

PURPOSE: To report the classification, management, and visual outcomes after laser in situ keratomileusis (LASIK) flap buttonhole caused by a microkeratome cut. SETTING: Private practice, Boston, Massachusetts, USA. METHODS: This retrospective observational case series comprised 15 patients with an intraoperative LASIK flap buttonhole or near buttonhole. In all cases, the flap was left in place or repositioned without excimer laser treatment. Buttonholes were classified by stage, and a treatment algorithm based on the stage was devised to determine the timing and type of intervention. The uncorrected visual acuity (UCVA), best spectacle‐corrected visual acuity (BSCVA), and complications associated with the laser vision correction surgery were reported. RESULTS: Postoperative follow‐up ranged from 1 week to 23 months. All 9 patients who were retreated had a postoperative UCVA of 20/25 or better. No retreated patient lost BSCVA. Before retreatment, the median UCVA was 20/80 (range 20/40−1 to counting fingers), the median BSCVA was 20/20−2 (range 20/15−1 to 20/70), and the spherical equivalent (SE) refractive errors ranged from −1.00 to −6.62 diopters (D). After retreatment, the median UCVA was 20/20−2 (range 20/15−1 to 20/25−1), the median BSCVA was 20/20 (range 20/15 to 20/20−3), and the SE refractive errors ranged from +0.50 to −0.75 D. Complications after laser correction treatment included overcorrection in 3 patients and corneal haze in 2 patients. CONCLUSIONS: Classification of buttonholes was helpful in guiding treatment. Good UCVA and BSCVA were achieved by following a simple treatment algorithm based on surface ablation.

Intraocular pressure fluctuation and glaucoma progression: what do we know?

While mean intraocular pressure (IOP) has long been known to correlate with glaucomatous damage, the role of IOP fluctuation is less clearly defined. There is extensive evidence in the literature for and against the value of short-term and long-term IOP fluctuation in the evaluation and prognosis of patients with glaucoma. We present here the arguments made by both sides, as well as a discussion of the pitfalls of prior research and potential directions for future studies. Until a reliable method is developed that allows for constant IOP monitoring, many variables will continue to hinder us from drawing adequate conclusions regarding the significance of IOP variation.

Corneal Crosslinking With Rose Bengal and Green Light: Efficacy and Safety Evaluation.

Purpose: To evaluate crosslinking of cornea in vivo using green light activation of Rose Bengal (RGX) and assess potential damaging effects of the green light on retina and iris. Methods: Corneas of Dutch belted rabbits were de-epithelialized, then stained with Rose Bengal and exposed to green light, or not further treated. Corneal stiffness was measured by uniaxial tensiometry. Re-epithelialization was assessed by fluorescein fluorescence. Keratocytes were counted on hematoxylin and eosin (H&E)–stained sections, and iris cell damage was assessed by lactate dehydrogenase staining. Thermal effects on the blood–retinal barrier (BRB) were assessed by fluorescein angiography and those on photoreceptors, retinal pigment epithelium (RPE), and choriocapillaris by light microscopy and transmission electron microscopy. Results: RGX (10-min irradiation; 150 J/cm2) increased corneal stiffness 1.9-fold on day 1 (1.25 ± 0.21 vs. 2.38 ± 0.59 N/mm; P = 0.036) and 2.8-fold compared with controls on day 28 (1.70 ± 0.74 vs. 4.95 ± 1.86 N/mm; P = 0.003). Keratocytes decreased only in the anterior stroma on day 1 (24.0 ± 3.0 vs. 3.67 ± 4.73, P = 0.003) and recovered by day 28 (37.7 ± 8.9 vs. 34.5 ± 2.4, P = 0.51). Iris cells were not thermally damaged. No evidence of BRB breakdown was detected on days 1 or 28. Retina from RGX-treated eyes seemed normal with RPE cells showing intact nuclei shielded apically by melanosomes, morphologically intact photoreceptor outer segments, normal outer nuclear layer thickness, and choriocapillaris containing intact erythrocytes. Conclusions: The substantial corneal stiffening produced by RGX together with the lack of significant effects on keratocytes and no evidence for retina or iris damage suggest that RGX-initiated corneal crosslinking may be a safe, rapid, and effective treatment.