Performance profile of sodium hyaluronate in patients with lipid tear deficiency: randomised, double-blind, controlled, exploratory study.

AIM: To assess the short-term efficacy of hypotonic 0.18% sodium hyaluronate in patients with evaporative tear-sufficient dry eye due to lipid tear deficiency (LTD). METHODS: This was a randomised, double-blind, controlled, exploratory study. A total of 10 patients with dry eye due to LTD were treated as follows: one drop of hypotonic 0.18% sodium hyaluronate in one eye and one drop of isotonic 0.3% hydroxypropyl-methylcellulose (HPMC)/0.1% dextran in the other eye. Non-invasive tear film break-up time (NIBUT) evaluated by using a tear scope with grid pattern and subjective ocular symptoms of dry eye were assessed at 15, 30, 60 and 90 min after instillation. RESULTS: Both sodium hyaluronate and HPMC/dextran caused a significant (p<0.05) improvement in NIBUT and symptoms. Mean (SD) NIBUT in the sodium hyaluronate group was 3.2 (1.0), 6.4 (2.8), 5.5 (1.9), 5.3 (1.3) and 3.9 (1.7) s at 0, 15, 30, 60 and 90 min, respectively, compared with 3.6 (1.9), 5.5 (3.2), 5.0 (1.5), 4.4 (2.2) and 3.5 (1.2) s in the HPMC/dextran group. However, increase in NIBUT was significantly (p<0.05) greater and longer in the sodium hyaluronate group than in the HPMC/dextran group. CONCLUSION: Treatment with sodium hyaluronate and HPMC/dextran eye drops is useful for treating patients with dry eye due to LTD. However, sodium hyaluronate caused a significantly (p<0.05) greater increase in NIBUT values than HPMC/dextran in such patients.

Real time intraocular pressure and lamellar corneal flap thickness in keratomileusis.

BACKGROUND: To measure real time intraocular pressure (IOP) during keratomileusis and to determine variability of corneal flap thickness by using different suction ring pressure settings. METHODS: Eight human cadaver eyes, two groups of four each, were used. The suction ring of the UniversalKeratome was applied to each eye, the same as for a standard automated lamellar keratoplasty (ALK) or laser in situ keratomileusis (LASIK) procedure, to create a lamellar corneal flap. The pressure of the suction ring on each eye was raised to one of two different levels, four eyes to 488 and the remaining four to 600 mm Hg. IOP was continuously recorded by manometer, from application of the suction ring through the end of the passage of the microkeratome. Central corneal thickness was measured, both before and after each procedure. RESULTS: IOP increased by >90 mm Hg after application of the suction ring at a pressure of either 488 mm Hg or 600 mm Hg. Corneal flaps performed under a suction ring pressure of 488 mm Hg measured 159.98+/-5 microm, whereas flap thickness for the 600-mm Hg group varied 1.4-266.2 microm. Two flaps exhibited irregular configurations. CONCLUSIONS: Real time IOP can be measured during keratomileusis. The results demonstrated a significant increase in IOP during the procedure. Suction ring pressure setting is an important variable in determining consistent corneal flap thickness during the keratomileusis procedure.

Excimer laser phototherapeutic keratectomy for corneal diseases.

The efficacy and safety of excimer laser phototherapeutic keratectomy (PTK) for treatment of various corneal pathologies were determined. The preoperative indications included lattice dystrophies (10 eyes), Reis-Bücklers dystrophies (4 eyes), macular dystrophies (2 eye), and corneal scarring secondary to trauma (1 eye). Mean follow-up time was 9.9 months (range 6-18 months). Uncorrected visual acuity postoperatively improved in 15 eyes (88.2%); not improved in 1 eye (5.9%) and decreased in 1 eye (5.9%). Corneal clarity improved in 14 of 17 eyes (82.4%) which corresponded to the improvement of uncorrected visual acuity. Ocular discomfort improved in 16 eyes (94.1%), decreased in 1 eye (5.9%) which subsequently developed double vision. The complications included delayed reepithelialization (> 7 days) in 6 eyes (35.3%) and corneal scarring 1 eye (5.9%). Sixty four per cent had increased significant hyperopia (> 4 D) and 7.1 per cent had significant induced astigmatism (> 2 D). One eye (5.9%) needed retreatment due to remaining corneal opacity. One eye (5.9%) had double vision due to irregular astigmatism. Excimer laser PTK is effective and safe for treatment of various corneal pathologies. It thus appears to be an alternative to penetrating keratoplasty in some patients.

Excimer laser photorefractive keratectomy and laser in situ keratomileusis for myopia and astigmatism.

The efficacy, predictability, safety, and short-term stability of excimer laser photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for treatment of myopia and astigmatism were determined. The preoperative myopia ranged from -1.50 to -15.75 D and the astigmatism was less than 4.0 D. Of the 147 eyes, 73 and 74 underwent PRK and LASIK, respectively. Mean preoperative spherical equivalent refraction (SE) was -3.72 +/- 1.69 D in the PRK group and -7.66 +/- 2.30 D in the LASIK group. Mean postoperative SE at the last examination (3 to 6 months) was -0.13 +/- 0.82 D and -0.38 +/- 1.19 D in the PRK and LASIK groups, respectively. Eighty six percent in the PRK group and 77 per cent in the LASIK group achieved a SE within +/- 1.0 D and the refractions were stable between 1 month and 3-6 months. Uncorrected visual acuity of 20/40 or better was noted in 91 per cent in the PRK group and 97 per cent in the LASIK group. No eyes lost one or more lines of best spectacle-corrected visual acuity in both groups. PRK and LASIK appear to be effective, safe, predictable, and short-term stable in treating myopia and astigmatism. Longer follow-up studies will help evaluate the long-term stability of the procedure and possibility of later complications.

Toxicity of topical anesthetic agents to human keratocytes in vivo.

PURPOSE: To test the potential toxicity on human keratocytes of topical anesthetic agents used after photorefractive keratectomy (PRK) to reduce or eliminate pain. SETTING: Department of Ophthalmology, Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. METHODS: Cultured human keratocytes were incubated with commercially available tetracaine and proparacaine at reduced concentrations of 0.001%, 0.01%, 0.1%, and 0.25%. Evaluations were performed by phase-contrast microscopy and tetrazolium salt colorimetric assay every 2 hours for 12 hours after adding 1 of the anesthetic agents to the media. RESULTS: After time of incubation and concentration were adjusted, both drugs reduced overall cell viability; however, tetracaine produced a larger decrease in cell viability than proparacaine (P = .008). For both drugs, significant differences were found among concentrations for and across time (P < .001 and P = .004, respectively). CONCLUSION: Both tetracaine and proparacaine had toxic effects on stromal keratocytes related not only to drug concentrations but also to time exposure. These findings underscore the widespread concern that anesthetic drugs may affect corneal stromal wound healing after PRK.

Effect of topical ascorbic acid on free radical tissue damage and inflammatory cell influx in the cornea after excimer laser corneal surgery.

OBJECTIVE: To evaluate the effect of topical ascorbic acid on oxygen free radical tissue damage and the inflammatory cell influx in the cornea after excimer laser keratectomy. METHODS: Five New Zealand white rabbits underwent bilateral phototherapeutic keratectomy with the 193-nm argon fluoride excimer laser. Following treatment, the right eye of each rabbit was treated with 10% ascorbic acid every 3 hours for 24 hours. The left eyes served as controls. After 24 hours, all animals were killed and their corneas were trephined and processed. Sections were stained with fast blue B and with hematoxylin-eosin. Oxidative tissue damage in the form of lipid peroxidation was detected by fluorescent peroxidized carbonyl compounds using a confocal laser scanning microscope. The quantity of these compounds was determined using the National Institutes of Health digital image analysis system. Statistical comparisons of lipid peroxidation and polymorphonuclear cell count between the ascorbic acid groups and the controls were performed using the Student t test. RESULTS: Lipid peroxidation and polymorphonuclear cell counts were significantly decreased in the superficial cornea of ascorbic acid-treated eyes compared with control eyes (P <.03 and <.02, respectively). CONCLUSIONS: Topical ascorbic acid application decreased oxygen radical tissue damage following excimer keratectomy; moreover, topical application of ascorbic acid was shown to reduce the acute inflammatory reaction efficiently. This suggests that topical ascorbic acid could be considered a complementary treatment in the pharmacological modulation after excimer laser corneal surgery. CLINICAL RELEVANCE: Corneal opacity may complicate excimer keratectomy. The use of an antioxidant to reduce tissue damage could help minimize postoperative stromal opacification.

PRK-induced anisometropia in the rabbit as a model of myopia.

BACKGROUND: Current animal models of myopia, such as the chick and the tree shrew, have characteristics that limit their applicability to human myopia and/or their use among researchers. The purpose of this study was to establish a rabbit model of myopia based on photorefractive keratectomy (PRK)-induced anisometropia. METHODS: A group of five pigmented rabbits was treated with a monocular -5 D PRK at 5 weeks of age. At 10 weeks of age, two of the eyes were retreated with a second -5 D PRK procedure to compensate for partial regression of the refractive effect. A second group of six pigmented rabbits was treated with a monocular -6 D PRK at 10 weeks of age. Longitudinal measurements of corneal curvature, refraction, and axial length were performed until the rabbits were 13 and 21 weeks of age in groups 1 and 2, respectively. The rabbits in each group were from the same litter. RESULTS: Keratometry and retinoscopy measurements confirmed the refractive effect of the PRK procedures. At the final measurement point in group 1, the PRK-treated eyes were significantly longer than the untreated eyes (16.01 +/- 0.45 mm vs 15.45 +/- 0.56 mm). In group 2, the PRK-treated eyes were significantly longer by 0.19 mm and 0.20 mm at ages 19 and 21 weeks, respectively. CONCLUSIONS: PRK-induced anisometropia is an effective technique to induce hyperopic error compensation in the rabbit as a model of myopic development. The technique is effective if the PRK procedure is performed at either 5 or 10 weeks of age. However, after PRK at 5 weeks of age, partial retreatment may be necessary due to regression of the PRK effect.