Effect of hinge location on corneal sensation and dry eye after laser in situ keratomileusis for myopia.

PURPOSE: To evaluate the effects of a superior or nasal hinge location on corneal sensation and dry eye after laser in situ keratomileusis (LASIK). SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: This prospective randomized masked study included 47 patients having bilateral myopic LASIK surgery. The first eye was randomly assigned to have a nasal or superior hinge flap; the fellow eye had the alternate location. Visual acuity, contrast sensitivity, corneal sensation, basic secretion test, tear film breakup time, conjunctival and corneal staining, and a subjective questionnaire were evaluated preoperatively and postoperatively at 1 week and 1, 3, and 6 months. The Wilcoxon signed rank test and paired t test were used for comparison. RESULTS: Dry eye occurred with the same frequency in both groups. However, eyes with the nasal hinge had significantly better nasal sensation than those with the superior hinge (P<.05) at 1 month. CONCLUSION: Better nasal corneal sensation was found at 1 month in the nasal hinge group but there was no difference in any other parameters measured.

Photodynamic therapy with verteporfin in a rabbit model of corneal neovascularization.

PURPOSE: To determine the efficacy of photodynamic therapy (PDT) with verteporfin (Visudyne; Novartis AG, Basel, Switzerland) for treatment of corneal neovascularization in a rabbit eye model. METHODS: Corneal neovascularization was induced in Dutch belted rabbits by placing an intrastromal silk suture near the limbus. Verteporfin was administered by intravenous injection at a dose of 1.5 mg/kg, and the pharmacokinetics of verteporfin distribution in the anterior segment or PDT-induced (laser energy levels 17, 50, and 150 J/cm(2)) regression of corneal blood vessels were then determined. To assess PDT-induced toxicity of the anterior segment, corneal and iris/ciliary body histology, and IOP were evaluated after PDT. RESULTS: Verteporfin accumulation in vascularized regions of the cornea and the iris/ciliary body tissue were time dependent and maximum levels achieved at 60 minutes after injection. In rabbits, PDT of corneal vessels using laser energy of 17 or 50 J/cm(2) resulted in 30% to 50% regression of corneal neovascularization; however, in these animals, a rapid regrowth of new blood vessels occurred between 3 and 5 days. In the rabbits receiving PDT using laser energies of 150 J/cm(2), the mean vessel regression was 56%. During the nine days of the laser therapy follow-up period, no vessel regrowth was observed in these rabbits. Histologic examination of the anterior segment after PDT (150 J/cm(2)) showed localized degeneration of the corneal blood vessels without observable change in other anterior segment structures. CONCLUSIONS: These results provide evidence that PDT can produce significant regression of neovascular corneal vessels with no observable toxicity to the anterior segments. However, the optimal laser energy necessary to induce long-term regression (150 J/cm(2)) was three times that used to treat choroidal neovascularization.

Diffuse lamellar keratitis: evaluation of etiology, histopathologic findings, and clinical implications in an experimental animal model.

PURPOSE: To induce diffuse lamellar keratitis (DLK) and investigate the potential causative agents in an animal model. SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: In 70 eyes of 35 Dutch Belted rabbits, a corneal flap was cut and the interface randomly exposed to 1 of 7 substances: Pseudomonas aeruginosa endotoxin, 1 of 2 Staphylococcus aureus exotoxins, meibomian gland secretion, povidone-iodine 10%, Palmolive Ultra soap, and Klenzyme soap. Slitlamp examinations were performed 1, 3, 5, and 7 days postoperatively. The DLK was staged from 1 to 4. On day 7, the rabbits were killed and the eyes enucleated and processed for histopathologic examination. RESULTS: At the end of the study, 54 eyes (46 exposed, 8 control) were available for evaluation. The 8 eyes studied concurrently in the control group remained clear and did not show interface inflammation. Thirty-one of 46 eyes (67%) treated with the various test substances developed DLK. The highest DLK rates were found with the cleaning soap Palmolive Ultra (100%; P =.022) and P. aeruginosa lipopolysaccharide endotoxin (90%; P =.026). CONCLUSIONS: Interface inflammation was consistently induced in the animal model. All 7 agents caused DLK in at least some eyes. The histopathologic evaluation showed the morphologic profile of the marked inflammatory cellular reaction that occurred in almost all the specimens.

Flap thickness accuracy: comparison of 6 microkeratome models.

PURPOSE: To determine the flap thickness accuracy of 6 microkeratome models and determine factors that might affect flap thickness. SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: This multicenter prospective study involved 18 surgeons. Six microkeratomes were evaluated: AMO Amadeus, Bausch & Lomb Hansatome, Moria Carriazo-Barraquer, Moria M2, Nidek MK2000, and Alcon Summit Krumeich-Barraquer. Eyes of 1061 consecutive patients who had laser in situ keratomileusis were included. Age, sex, surgical order (first or second cut), keratometry (flattest, steepest, and mean), white-to-white measurement, laser used, plate thickness, head serial number, blade lot number, and occurrence of epithelial defects were recorded. Intraoperative pachymetry was obtained just before the microkeratome was placed on the eye. Residual bed pachymetry was measured after the microkeratome cut had been created and the flap lifted. The estimated flap thickness was determined by subtraction (ie, mean preoperative pachymetry measurement minus mean residual bed pachymetry). RESULTS: A total of 1634 eyes were reviewed. Sex distribution was 54.3% women and 45.7% men, and the mean age was 39.4 years +/- 10.6 (SD). In addition, 54.5% of the procedures were in first eyes and 45.5%, in second eyes. The mean preoperative pachymetry measurement was 547 +/- 34 microm. The mean keratometry was 43.6 +/- 1.6 diopters (D) in the flattest axis and 44.6 +/-1.5 D in the steepest axis. The mean white-to-white measurement was 11.7 +/- 0.4 mm. The mean flap thickness created by the devices varied between head designs, and microkeratome heads had significant differences (P<.05). Factors that explained 78.4% of the variability included microkeratome model, plate thickness, mean preoperative pachymetry, Kmin, surgery order, head serial number, blade lot number, and surgeon. Factors such as age, sex, Kmax, Kaverage, white to white, and laser had no significant correlation to flap thickness. CONCLUSIONS: The results demonstrated variability between the 6 microkeratome models. Device labeling did not necessarily represent the mean flap thickness obtained, nor was it uniform or consistent. Thinner corneas were associated with thinner flaps and thicker corneas with thicker flaps. In addition, first cuts were generally associated with thicker flaps when compared to second cuts in bilateral procedures.

Refractive Surgery Survey 2001.

In February 2001, a questionnaire on the practice of refractive surgery was sent worldwide to all 8196 members of the American Society of Cataract and Refractive Surgery; 1511 responses (18.4%) were received. Although laser in situ keratomileusis (LASIK) was the most common refractive procedure reported, phakic intraocular lenses, clear lens extraction, and photorefractive keratectomy were also widespread. Nineteen percent of the respondents said they had had refractive surgery, and that group reported performing significantly more procedures than those who had not had a refractive procedure (P < .0001). The most common complication of LASIK was dry eyes, occurring in more than half of the cases in one fourth of the practices; however, only 30% of surgeons said they perform a Schirmer test before surgery. High-volume surgeons reported seeing fewer cases of flap striae (P = .002) and slipped flaps (P = .02) than low-volume surgeons. Seventy-seven percent said that wavefront LASIK ablation will increase the quality of vision and of those already performing wavefront ablation, 92% stated they believe it will improve outcomes.

Corneal flap complications in refractive surgery: Part 1: development of an experimental animal model.

PURPOSE: To report the outcome, learning curve, and complication rates of an experimental animal model for corneal flaps in refractive surgery. SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Charleston, South Carolina, USA. METHODS: Corneal flaps with a nasal or a temporal hinge were created in 190 eyes of 95 Dutch Belted rabbits using the Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical). Diffuse lamellar keratitis (DLK) was induced by inoculating the corneal interfaces with 1 of 7 substances. Postoperatively, the eyes were examined with a slitlamp. Special emphasis was placed on corneal flap complications and the relationship between slipped flaps and hinge position and/or inoculation agent. RESULTS: A good corneal flap was achieved in 174 eyes (92%). The eyes with a nasal hinge had a lower incidence of slipped flaps (14%) than eyes with a temporal hinge (37%) (P =.02). CONCLUSION: With the animal model described, corneal flaps were created in a precise and reproducible way in more than 90% of eyes. Nasal hinged flaps showed less postoperative displacements than temporal hinged flaps and are adequate for further study.

Corneal flap complications in refractive surgery: Part 2: postoperative treatments of diffuse lamellar keratitis in an experimental animal model.

PURPOSE: To induce diffuse lamellar keratitis (DLK) and investigate a prophylactic treatment with pharmacological agents. SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Charleston, South Carolina, USA. METHODS: In 100 eyes of 50 Dutch Belted rabbits, a nasal corneal flap was cut and the interface inoculated with Pseudomonas aeruginosa lipopolysaccharide endotoxin (n = 50) or Palmolive Ultra soap (n = 50). The eyes were randomly assigned to treatment with a mast-cell stabilizer, a nonsteroidal antiinflammatory drug (NSAID), a fluoroquinolone antibiotic agent, a corticosteroid, or left without treatment as a control. Slitlamp examinations and photographs were performed 1, 3, 5, and 7 days postoperatively, and DLK was graded by a masked observer from 0 (no DLK) to stage 4. RESULTS: At the end of the study, 80 eyes were available for evaluation. Ninety-four percent of the untreated eyes developed DLK compared to 56% of eyes treated with NSAIDs and 63% of eyes treated with steroids (P<.05, Fisher exact test). The DLK rates with the mast-cell stabilizer and fluoroquinolone antibiotic agent were 86% and 76%, respectively. The DLK incidence in the latter 2 groups was not significantly different from that in the control eyes (P>.05, Fisher exact test). CONCLUSIONS: Postoperative prophylactic treatment with NSAIDs and corticosteroids led to a statistically significantly lower incidence of postoperative DLK. The study demonstrated that corticosteroids and NSAIDs can be used to treat DLK after LASIK. While steroids are a generally accepted treatment for DLK, NSAIDS may offer an additional potent modality.

Evaluation of preoperative and postoperative prophylactic regimens for prevention and treatment of diffuse lamellar keratitis.

PURPOSE: To investigate preoperative and postoperative prophylactic treatment with different pharmacological agents before flap cutting and exposure to a diffuse lamellar keratitis (DLK) causative agent. SETTING: Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: The study comprised 48 eyes of 24 Dutch-belted rabbits. Three days before a corneal flap was cut and the corneal interface was exposed to Pseudomonas aeruginosa lipopolysaccharide endotoxin, a DLK causative agent, the eyes were randomly assigned to treatment with a mast-cell stabilizer, a nonsteroidal antiinflammatory drug (NSAID), or a corticosteroid or left without treatment as controls. The treatment was maintained throughout the 1-week follow-up. Slitlamp examinations and photographs were performed at 1, 3, 5, and 7 days; DLK was graded by a masked observer from 0 (no DLK) to IV. Corneal interface scrapings were performed in selected eyes on day 7. RESULTS: At the end of the follow-up, 36 eyes were available for evaluation. At 1 week, 100% of the control eyes and the eyes treated with the mast-cell stabilizer developed DLK; in the NSAID-treated and corticosteroid-treated eyes, the DLK rate was 86% and 70%, respectively. At 1 day, the severity of DLK was significantly lower in eyes treated with the mast-cell stabilizer (0.44) and at 7 days, it was significantly lower in corticosteroid-treated eyes (0.3) than in the control group (1.5 and 1.4, respectively) (P<.05, Wilcoxon test). Corneal interface scraping from an eye with grade III DLK showed numerous inflammatory cells. CONCLUSIONS: Preoperative and postoperative treatment with corticosteroids significantly reduced the severity of DLK compared to the untreated control eyes in this animal model. Treatment with a mast-cell stabilizer and an NSAID had less effect on the postoperative course of DLK.

Fluorescein angiographic lesion type frequency in neovascular age-related macular degeneration.

OBJECTIVE: To assess the frequency of lesion types using fluorescein angiography (FA) in neovascular age-related macular degeneration (nAMD). DESIGN: Cross-sectional study. PARTICIPANTS: Two hundred cases of nAMD. METHODS: Fluorescein angiograms from 908 patients (university-based, tertiary retinal referral practice [UP] = 478; comprehensive, community-based eye clinic [CC] = 430) were reviewed to identify 200 cases of nAMD (100 from each center). Two graders evaluated the frequency of angiographic subtypes. MAIN OUTCOME MEASURES: Identifying (1) the frequency of subfoveal nAMD lesions that meet the definition of "predominantly classic," "minimally classic," "occult with no classic"; (2) lesion location, size, and subtype; and (3) the intergrader agreement (kappa). RESULTS: There was little difference in the frequency of lesion type between the UP and the CC. Most nAMD lesions were subfoveal (78.5%, 157 of 200), and of these, 20% (32 of 157) were predominantly classic; whereas 73% (114 of 157) were occult with no classic, and 7% (11 of 157) were minimally classic. Of the 200 angiograms, 33 (16.5%) were juxtafoveal, and 10 (5%) were extrafoveal. Twenty of the 43 juxtafoveal and extrafoveal lesions (47%) were predominantly classic. Classic with no occult subfoveal lesions were smaller than minimally classic or occult with no classic (1.7 vs. 3.7 and 2.8 mm; P = 0.001 and 0.01, respectively). Of 114 subfoveal occult with no classic lesions, 54 (47%) had both smaller lesion size <==4 disc areas (DA) and lower visual acuity <20/50, whereas 107 (94%) had a smaller lesion or lower visual acuity. CONCLUSIONS: Most angiographic lesions of patients who undergo FA for nAMD are subfoveal and occult. We estimate that 20% of subfoveal lesions are predominantly classic. Approximately half of the juxtafoveal and extrafoveal lesions are predominantly classic. Nearly 30% of all nAMD lesions have both small occult lesions (size <==4 DA) and a visual acuity less than 20/50. We found minimal difference in lesion type between a UP and a CC.