Faculty Bibliography

PURPOSE: To determine the relative contributions to aqueous outflow resistance of the tissues distal to the inner wall of Schlemm's canal. METHODS: While performing constant pressure perfusion at 10 mm Hg, a 193-nm excimer laser (Questek) was used to precisely remove portions of sclera, unroofing Schlemm's canal while leaving the inner wall intact. The laser beam was masked to produce a beam 2 mm by 1 mm. The laser output was constant at a fluency of 75 mJ/cm2 and 20 Hz. The excimer laser at a frequency of 1 Hz was used as the aiming beam. Photoablation was performed on human cadaver eyes at the limbus at an angle of 0 degrees to 45 degrees from the optical axis. As the excimer photoablations progressed, Schlemm's canal was visualized by the fluorescence of the Barany's solution containing fluorescein dye. After perfusion fixation the eyes were immersion-fixed overnight. The facility of outflow before (Co) and after (Ce) the excimer ablation was measured in 7 eyes. RESULTS: The facility of outflow increased in all eyes after the excimer sinusotomy, from a mean of 0.29+/-0.02 before the sinusotomy to 0.37+/-0.03 microl/min per mm Hg after (P < 0.05). The mean ratio of outflow facility after and before ablation (Ce/Co) was 1.27+/-0.08 (range, 1.20-1.39), a reduction of outflow resistance of 21.3%. Using the formula of Ellingsen and Grant (1972), percentage of resistance to outflow eliminated = 100 [1 - alphaCo/Ce - (1 - alpha)Co], where alpha = fraction of the circumference dissected. Assuming that because of circumferential flow approximately 50% of Schlemm's canal is drained by the single opening made in the outer wall ablation studies, this results in resistance to outflow eliminated of 35%, which is consistent with the calculated eliminated resistance derived from the data of Rosenquist et al., 1989. Light and scanning electron microscopy confirmed the integrity of the inner wall Schlemm's canal underlying the area of ablation. CONCLUSIONS: The results provide direct evidence indicating that approximately one third of resistance to outflow in the human eye lies distal to the inner wall Schlemm's canal in an enucleated perfused human eye.

OBJECTIVE:To report two cases of a malignant glaucoma-like syndrome following pars plana vitrectomy. DESIGN/METHODS:Two interventional case reports. INTERVENTION/METHODS:The first patient was treated with a neodymium:YAG laser peripheral iridectomy with hyaloidectomy and with intracameral tissue plasminogen activator. The second patient was treated with a posterior approach iridectomy through residual hyaloid, zonules, and iris. MAIN OUTCOME MEASURES/METHODS:Axial anterior chamber depth and intraocular pressure (IOP). RESULTS:The interventions resulted in deepening of the anterior chambers and normalization of IOPs. CONCLUSION/CONCLUSIONS:A pseudomalignant glaucoma syndrome may be related to obstruction of aqueous flow, either by residual anterior hyaloid or by fibrin and other inflammatory debris at the level of the ciliary body-zonular apparatus. Treatment of this syndrome involves restoring aqueous flow to the anterior chamber by disrupting the residual anterior hyaloid or clearing fibrin or inflammatory debris. The clinician should not disregard the possibility of a pseudomalignant glaucoma syndrome following vitrectomy despite the fact that vitrectomy has traditionally been considered a curative treatment for malignant glaucoma.

PURPOSE/OBJECTIVE:Sialyl Lewis X (sLex), Lewis X (Lex), and N-acetyllactosamine are carbohydrate chains of neolactoglycoconjugates which are expressed by specific cell types and are important in the functioning of cells within an organism. This study attempts to determine the expression of these glycoconjugates on the conjunctiva, cornea, and trabecular meshwork (TM) of both normal and glaucomatous eyes. METHODS:Frozen anterior segment sections of both normal and glaucomatous human cadaver eyes, as well as rabbit eyes, were stained with a panel of monoclonal antibodies (mAbs) to neolactoglycoconjugates using an Avidin Biotin Peroxidase Complex/Alkaline Phosphatase staining method. RESULTS:SLex characteristically stained both human conjunctival and corneal epithelia in normal (n=5) and glaucomatous (n=5) sections. SLex stained corneal and conjunctival epithelia of glaucomatous eyes much more intensely than normal eyes. Rabbit cornea sections stained for sLex, Lex, and N-acetyllactosamine. However, human cornea only consistently stained with sLex. Normal and glaucomatous human TM sections did not stain for sLex, Lex, or N-acetyllactosamine. CONCLUSIONS:The expression of glycoconjugates with sLex side chains appears to be upregulated in the conjunctival and corneal epithelia of glaucomatous eyes. Distinct species specific differences were noted in Lex and N-acetyllactosamine staining patterns in rabbit and human corneal epithelia.

Objective: To analyze glaucomatous eyes with known focal defects of the nerve fiber layer (NFL), relating optical coherence tomography (OCT) findings to clinical examination, NFL and stereoscopic optic nerve head (ONH) photography, and Humphrey 24-2 visual fields. Design: Cross-sectional prevalence study. Participants: The authors followed 19 patients in the study group and 14 patients in the control group. Intervention: Imaging with OCT was performed circumferentially around the ONH with a circle diameter of 3.4 mm using an internal fixation technique, One hundred OCT scan points taken within 2.5 seconds were analyzed. Main Outcome Measures: Measurements of NFL thickness using OCT were performed. Results: In most eyes with focal NFL defects, OCTs showed significant thinning of the NFL in areas closely corresponding to focal defects visible on clinical examination, to red-free photographs, and to defects on the Humphrey visual fields. Optical coherence tomography enabled the detection of focal defects in the NFL with a sensitivity of 65% and a specificity of 81%,. Conclusions Analysis of NFL thickness in eyes with focal defects showed good structural and functional correlation with clinical parameters, Optical coherence tomography contributes to the identification of focal defects in the NFL that occur in early stages of glaucoma.