Robert E. Christensen

The electroretinogram in advanced open-angle glaucoma

Fourteen patients with advanced open-angle glaucoma were evaluated prospectively by electroretinography and the results were compared with normal controls who were matched for age and sex. All glaucoma patients had visual acuity of 20/50 or better, cup-to-disc ratios of 0.7 or greater in at least one eye, and visual field loss consistent with advanced glaucoma. Numerous electroretinographic parameters were significantly abnormal when compared with the control group.

Inhibition of the Epinephrine-Induced Reduction of Intraocular Pressure by Systemic Indomethacin in Humans

In a prospective, randomized, double-masked study, 2% epinephrine applied topically twice each day for two weeks to the eyes of patients with glaucoma or ocular hypertension caused an 8.1 +/- 1.4-mm Hg (mean +/- S.E.M.) reduction of intraocular pressure in placebo-treated patients, but only a 1.9 +/- 0.6-mm Hg decrease in patients treated with 25 mg of orally administered indomethacin four times each day (P less than .0005). Systemic treatment with indomethacin for one week did not significantly increase intraocular pressure by itself (baseline, 19.7 +/- 0.6 mm Hg, vs 20.1 +/- 1.4 mm Hg after indomethacin treatment). When indomethacin treatment was discontinued in those patients receiving topical epinephrine, there was a further significant (P less than .05) reduction in intraocular pressure compared with the placebo-treated group. Since the ocular hypotensive effect of topically applied epinephrine is inhibited by indomethacin, a cyclo-oxygenase inhibitor, these results suggest that this reduction of intraocular pressure is at least partially mediated by the endogenous production of prostaglandins, or other cyclo-oxygenase products, and that the intraocular pressure of glaucoma patients undergoing epinephrine therapy may increase when systemic cyclo-oxygenase inhibitors such as indomethacin or aspirin are taken.

Biometric Variables in Patients with Occludable Anterior Chamber Angles

Biometric studies of the ocular dimensions in eyes with narrow anterior chamber angles provide insight into the pathophysiology of pupillary block and may show which eyes are more prone to develop angle-closure glaucoma. We reviewed the records of 56 patients with occludable angles examined between 1980 and 1984. Initial biometric data obtained on the patients included corneal diameter, anterior chamber depth, lens thickness, and ocular axial length. The average length of follow-up was five years. Of 54 patients with complete clinical records, 20 (37%) eventually required peripheral iridectomy after a mean duration of 16 months from the initial examination. Coxs survival analysis showed a strong correlation between shortened duration to peripheral iridectomy and increasing lens thickness/ocular axial length ratio factor (P = .03). No other variables were significantly related to outcome. This suggests that the lens thickness/ocular axial length ratio may be useful as a predictor of clinical outcome in narrow-angle glaucoma.

Adverse Ocular Effects of Acetate Hemodialysis

In order to better define ocular dynamics during hemodialysis, we studied intraocular pressure (IOP) and anterior chamber depth (ACD) serially during both acetate and bicarbonate hemodialysis in 10 stable hemodialysis patients. IOP did not change significantly in any patient during dialysis. In contrast, however, ACD decreased significantly during acetate but not bicarbonate dialysis. ACD could be maintained during acetate dialysis by concomitant administration of mannitol. We conclude that acetate dialysis might adversely affect ocular dynamics in susceptible patients with glaucoma or recent ocular surgery. In such individuals administration of mannitol or use of a bicarbonate dialysate should be considered.

The effects of Nd: YAG laser iridotomy on the corneal endothelium

We studied 18 eyes of 18 patients undergoing Nd:YAG laser peripheral iridotomy for occludable anterior chamber angles. A Q-switched laser was used for all treatments. Preoperative and postoperative pachymetry and corneal endothelial cell counts were obtained centrally, in the nontreated superonasal quadrant, and in the treated superotemporal quadrant. No significant differences were found between preoperative and postoperative corneal thickness at any site. A small decrease in endothelial cell count (95 cells/mm2) at the treated site was statistically significant (P = .04).

Effects of argon laser iridotomy on the corneal endothelium

We studied 14 eyes of 14 patients undergoing argon laser peripheral iridotomy for occludable (narrow) anterior chamber angles. Preoperative and postoperative pachymetry and corneal endothelial cell counts by specular microscopy were obtained centrally and in both the treated and nontreated superior quadrants. No significant differences were found between preoperative and postoperative measurements of corneal thickness and endothelial cell counts in any area.

A Clinical Evaluation of the BioPen

We conducted a clinical trial on the Oculab BioPen, a portable, handheld applanation instrument designed to measure ocular axial lengths. We compared the measurements obtained from the BioPen with those obtained from the Ultrascan Digital B System IV from CooperVision. Accuracy and reproducibility were assessed in vitro by performing ten measurements with each instrument on a precalibrated 25.8-mm plastic test block. The in vivo reproducibility of the BioPen was evaluated by performing five serial readings on each eye of 58 patients. Keratometry measurements were also recorded to determine whether the BioPen provided consistent readings regardless of corneal curvature. We found the BioPen to be as accurate and reproducible as the Ultrascan Digital B in vitro and in vivo. Corneal curvature had no effect on the in vivo reproducibility of the BioPen.