PURPOSETo study the differences in disease caused by two wild-type strains of Candida albicans in a model of contact lens-facilitated keratitis in rabbits.METHODSTwo strains, SC5314 and VE175, were examined. Standardized inocula were placed on the debrided corneal surface of one eye in Dutch belted rabbits and covered with a contact lens. A temporary tarsorrhaphy was opened after 24 hours with removal of the contact lens. Six days later, corneas were photographed and animals killed. Corneas were bisected with one half for quantitative isolate recovery and the other for stromal penetration by hyphae.RESULTSStrain SC5314 was significantly more virulent. The mean hyphal penetration into the cornea was 24.4% +/- 8.5% of the corneal thickness, and in three of six corneas hyphae penetrated through the entire cornea. In contrast, for VE175, the mean hyphal penetration was 2.6% +/- 1.2%. The difference between these two strains was statistically significant (P = 0.0297). Hyphae did not penetrate into the deep layers of the cornea in any of the six rabbits infected with VE175. The grading of clinical disease was consistent with histology, in that strain SC5314 caused more severe infection than VE175 and the difference was statistically significant (P = 0.0048). There was no difference in isolate recovery.CONCLUSIONSWild-type strains of C. albicans can differ significantly in virulence as measured by depth of fungal invasion into corneas and clinical evaluation of infection. Further characterization of the intrinsic genetic differences between such strains may help identify factors responsible for fungal virulence.

PURPOSE:A model of experimental keratomycosis was established that mimics human disease in which the only fungi present are those that are actively growing within the cornea.METHODS:Dutch-belted rabbits received a subconjunctival injection of triamcinolone acetonide to one eye. One day later the epithelium was removed from the central cornea and a standardized inoculum of Candida albicans blastoconidia was placed on the corneal surface and covered with a contact lens. The lids were closed with a lateral tarsorrhaphy. After 24 hours, the lid sutures and contact lens were removed. Five days later the animals were killed, and their corneas were subjected to separate isolate recovery and histology studies. A group of similarly infected rabbits without corticosteroid injection served as controls.RESULTS:Both groups developed invasive corneal disease. Although isolate recovery was not significantly different from corticosteroid-treated rabbits compared with controls, fungal biomass was increased. Hyphal invasion was limited to the anterior cornea in control eyes, but penetrated deep stroma in most of the corticosteroid-treated rabbits.CONCLUSIONS:Invasive corneal disease can be established with a surface inoculum. Corticosteroid administration increased corneal penetration of hyphae. Quantitative isolate recovery is not a reliable measure of the fungal load within the cornea.

Trabeculectomy with early postoperative slit lamp laser suture lysis is a controlled means of maximizing bleb filtration and reducing intraocular pressure. However, this procedure is not possible in children and even some adults. Thus, an effective alternative method for postoperative laser suture lysis was investigated. Dissection of 15 scleral flaps was performed on two human cadaver eyes. Each flap was closed with two 10-0 nylon sutures and the conjunctiva repositioned to cover the sutures. Laser suture lysis was performed using an optical fiber probe for the Argon/Dye laser and a Hoskins laser lens. Five different wavelengths were studied: red (630 nm), orange (595 nm), yellow (577 nm), blue-green (488 - 514 nm), and green (514 nm). Each individual wavelength was studied using six scleral flap sutures, and a single laser application was applied to each suture. Suture lysis was attainable with each wavelength, however the argon green lysed 100 percent of the sutures. Histologic analysis demonstrated no conjunctival injury with any of the above wavelengths. These findings suggest that multiple wavelengths are effective in laser suture lysis without a slit lamp biomicroscope.

A free electron laser (FEL) may be tuned to novel wavelengths to explore laser-tissue interactions for development or improvement of laser surgical procedures. This study investigated the effect of selected infrared wavelengths upon human cornea and optic nerve tissues. Human cadaver eyes were placed in 10% dextran solution to normalize corneal thickness, and solution was injected intraocularly to achieve a physiologic intraocular pressure. The corneas and optic nerves were lased with the 6.0 micrometer amide I band, 6.1 micrometer water absorbency peak, 6.45 micrometer amide II band, and 7.7 micrometer. The Vanderbilt FEL produces 5 microsecond long macropulses at 10 Hz with each macropulse consisting of 1 ps micropulses at 3 GHz. Histologic examination of the corneal tissue showed the least amount of collateral damage (10 - 20 micrometers) with the 6.0 micrometer amide I band, while marked shrinkage occurred with the 7.7 micrometer wavelength. For optic nerve tissue, the least amount of collateral damage (0 micrometer visible) occurred at 6.1 micrometer water absorbency peak and 6.45 micrometer amide II band, while the most damage (30 - 50 micrometers) was observed with the 7.7 micrometer wavelength. We conclude that different tissues may have different optimal wavelengths for surgical laser procedures.

An endoscope allows visualization of the anterior chamber angle in porcine eyes despite the presence of cloudy corneas. The pectinate ligaments in the anterior chamber angle are a surgical model for primary infantile glaucoma. This study investigated the histologic results, one month after treating the anterior chamber angle with a goniotomy needle, the holmium:YAG laser, or the erbium:YAG laser coupled to a small endoscope. The anterior chambers were deepened with a viscoelastic material in one-month-old anesthetized pigs. An Olympus 0.8 mm diameter flexible endoscope was externally coupled to a 23 gauge needle or a 300 micron diameter fiber. The angle was treated for 120 degrees by one of the three methods, and the probe was removed. During the acute study, all three methods cut the pectinate ligaments. The histologic findings one month after healing demonstrated minimal surrounding tissue damage following goniotomy with a needle and the most surrounding tissue damage following treatment with the holmium:YAG laser.