David Tingey

Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis

Purpose: To determine the relationship of intraocular pressure (IOP) and central corneal thickness (CCT) in normal myopic eyes and after laser in situ keratomileusis (LASIK). Setting: TLC The Windsor Laser Center, Windsor, Ontario, Canada. Methods: Intraocular pressure measured by Goldmann applanation tonometry and CCT by ultrasonic pachymetry were determined in a group of untreated corneas of 120 patients (203 eyes) and in 50 patients (85 eyes) pre‐ and post‐LASIK. Statistical analyses were performed with the Pearson correlation coefficient and paired Student t test. Results: In the untreated group of 288 eyes, mean CCT was 544.0 &mgr;m ± 37.3 (SD) (range 461 to 664 &mgr;m) and mean IOP, 15.6 ± 2.7 mm Hg (range 10 to 24 mm Hg). The correlation between IOP and CCT in this group was highly significant (r = 0.44; P < .0001). The slope was 0.032 mm Hg/&mgr;m of CCT or an approximate decrease of 1 mm Hg, for a reduction in CCT of 31.3 &mgr;m. In the post‐LASIK group, mean CCT dropped approximately 73.0 &mgr;m to 479.5 ± 41.2 &mgr;m (range 408 to 503 &mgr;m) and IOP dropped to a mean of 13.6 ± 3.3 mm Hg (range 7 to 22 mm Hg). A significant correlation was found between IOP and CCT after LASIK (r = 0.33; P < .002). The difference between the mean pre‐ and post‐LASIK measurements of applanation IOP was 2.5 mm Hg, which was significant (P < .0001). The post‐LASIK slope was 0.027 mm Hg/Vm, or a decrease of 1.0 mm Hg per 37.8 &mgr;m reduction in CCT. Conclusion: Central corneal thickness is an important variable in the evaluation of applanation IOP and should be included in the assessment of any case of potential glaucoma or ocular hypertension, particularly in eyes with previous photoablative refractive surgery.

Meta-analysis of the effect of latanoprost and brimonidine on intraocular pressure in the treatment of glaucoma

OBJECTIVE The purpose of this study was to indirectly quantify and compare the intraocular pressure (IOP)-lowering effects of latanoprost and brimonidine eye drops at baseline and after 3 and 6 months in the treatment of primary open-angle glaucoma. METHODS This meta-analysis combined data from all randomized controlled trials comparing the effects on IOP of latanoprost and brimonidine treatment in adults with a baseline IOP > or =20 mm Hg. MEDLINE and EMBASE were searched for reports of the ophthalmic administration of either drug versus the other, placebo, or active therapy. Included studies reported IOP as either means or differences (with SD or SE) and sample sizes. A random-effects model was used to pool data within each drug group. As a proxy for success rates, area under the curve (AUC) was calculated for the proportion of patients having an IOP <20 mm Hg. RESULTS One hundred fifty-five articles reporting on 158 trials were identified; 147 papers were rejected (141 were not randomized controlled trials, 5 were duplicates, and 1 had nonextractable data), leaving 9 trials from 8 articles. A total of 2152 patients were included in the meta-analysis: 597 received latanoprost, 571 received brimonidine, and the remainder received timolol or betaxolol. Baseline IOPs were similar in patients randomized to latanoprost or brimonidine (25.3 and 24.6 mm Hg, respectively). At 3 months, latanoprost and brimonidine reduced IOP by 8.4 and 6.5 mm Hg, respectively (P = 0.004 latanoprost vs brimonidine), and at 6 months by 8.0 and 6.2 mm Hg, respectively (P = 0.045). AUC was 0.834 and 0.675 at 3 months for latanoprost and brimonidine, respectively, and 0.817 and 0.715 at 6 months, respectively (both, P < 0.001). CONCLUSIONS This indirect comparison of data from the available randomized clinical trials showed latanoprost to be statistically superior to brimonidine in reducing IOP in adults with primary open-angle glaucoma. Additional long-term, head-to-head comparisons of the efficacy, safety, and cost of latanoprost and brimonidine are needed to support and supplement these findings.

Intraocular pressure control and persistence on treatment in glaucoma and ocular hypertension

BACKGROUND The purpose of this study was to characterize current patterns of treatment of glaucoma and ocular hypertension and to examine the effect of those patterns on intraocular pressure (IOP) control and persistence on therapy. METHODS A retrospective chart review was conducted at 3 ophthalmology practices in Alberta. Data were collected for patients who had begun therapy for newly diagnosed primary open-angle glaucoma or ocular hypertension between May 1, 1998, and Sept. 30, 1999 (phase 1), and for patients who had begun second-line therapy after initial therapy with a beta-blocker had failed (phase 2). Data were collected for a minimum of 24 months for phase 1 and a minimum of 18 months for phase 2. RESULTS We included 115 patient charts in phase 1 and 93 in phase 2. In each phase, the patients for whom latanoprost had been prescribed in unfixed combination with a beta-blocker had the greatest mean percentage reduction in IOP at month 24, and the patients for whom latanoprost had been prescribed alone or in combination with a beta-blocker were more likely to still be on initial therapy at month 24; the difference in persistence on therapy was statistically significant only in phase 1 (p = 0.001). The mean number of switches in therapy was smaller in phase 1 than in phase 2 in all therapy groups. INTERPRETATION Compared with other first- and second-line forms of therapy, treatment with latanoprost, alone or in combination with a beta-blocker, was associated with greater reductions in IOP, better therapeutic persistence, fewer therapy switches and fewer ophthalmologist visits over a 2-year period.

The Effect of Intracameral Ethacrynic Acid on the Intraocular Pressure of Living Monkeys

Previous studies have shown that the sulfhydryl-reactive ethacrynic acid increases outflow facility in living monkeys when perfused via the anterior chamber. To study its potential clinical use further, living monkeys were intracamerally injected with 10 microliters of ethacrynic acid, with concentrations ranging from 0.5 to 7.5 mmol/l. The fellow control eye was injected with 10 microliters of diluent. The status of the anterior segment was monitored by slit-lamp biomicroscopy and the intraocular pressure was measured by pneumatonometry with the monkeys anesthetized with ketamine. The anterior segment of living monkeys tolerated injections up to 3.0-mmol/l ethacrynic acid without marked adverse effects. One of 13 monkey eyes injected with 3.0-mmol/l ethacrynic acid demonstrated mild reversible segmental corneal edema. The greatest mean intraocular pressure reduction in the 3.0- to 3.75-mmol/l group occurred at six hours, with the experimental intraocular pressure decreasing 2.9 mm Hg compared to a mean intraocular pressure increase of 0.1 mm Hg in the control group (n = 19). Concentrations of ethacrynic acid less than 3.0 mmol/l did not provide reliable reduction of intraocular pressure, whereas concentrations greater than 3.75 mmol/l caused a greater incidence and severity of corneal edema. We believe that the intracameral injection of ethacrynic acid can reliably and safely reduce intraocular pressure in living monkey eyes, and that this drug deserves further investigation as a potential antiglaucomatous agent.

Primary intraocular lymphoma arising during methotrexate treatment of temporal arteritis

CASE REPORT Primary intraocular lymphoma arose over a period of 9 months in the left eye of an 81-year-old woman who was blind in both eyes from temporal arteritis. During this period, she was treated with prednisone and methotrexate. Following a sudden total hyphema, the eye was enucleated. Examination revealed that, in addition to iris neovascularisation and central retinal artery occlusion, the neurosensory retina was replaced by atypical lymphocytes. COMMENTS Histological and immunohistochemical studies confirmed the presence of a lymphoma with features indicative of an immunosuppression-related disorder. The relationship of the lymphoma to the vascular changes within the eye is discussed.

Stability of the Antiproliferative Effect of Mitomycin-C after Reconstitution

PurposeThe purpose of this study was to determine the long-term stability of the antiproliferative effect of mitomycin-C (MMC) following reconstitution. MethodsIdentical MMC preparations were reconstituted from the crystalline form and then stored at room temperature or 4°C. Cultured human Tenons fibroblasts were exposed to MMC (0.5 mg/ml) for 2.5 min at 0, 3, 7, 10, 14, 21, 28, 35, and 42 days following reconstitution. After removal of the drug, fibroblast proliferation was measured by tritiated thymidine uptake. ResultsThe percentage of inhibition was maintained at >85% for both the room temperature and the 4°C groups, and this inhibition persisted for the duration of the experiment. There was no statistically significant difference in the results between the storage temperatures. ConclusionsThese data suggest that MMC retains its antiproliferative effect for at least 6 weeks following reconstitution and that this effect is not changed by storage temperature. Cost savings may be realized by storing MMC in unit-dose reconstituted aliquots for these longer periods, providing sterility can be assured.

Summary of Glaucoma Diagnostic Testing Accuracy: An Evidence-Based Meta-Analysis.

Background New glaucoma diagnostic technologies are penetrating clinical care and are changing rapidly. Having a systematic review of these technologies will help clinicians and decision makers and help identify gaps that need to be addressed. This systematic review studied five glaucoma technologies compared to the gold standard of white on white perimetry for glaucoma detection. Methods OVID® interface: MEDLINE® (In-Process & Other Non-Indexed Citations), EMBASE®, BIOSIS Previews®, CINAHL®, PubMed, and the Cochrane Library were searched. A gray literature search was also performed. A technical expert panel, information specialists, systematic review method experts and biostatisticians were used. A PRISMA flow diagram was created and a random effect meta-analysis was performed. Results A total of 2,474 articles were screened. The greatest accuracy was found with frequency doubling technology (FDT) (diagnostic odds ratio (DOR): 57.7) followed by blue on yellow perimetry (DOR: 46.7), optical coherence tomography (OCT) (DOR: 41.8), GDx (DOR: 32.4) and Heidelberg retina tomography (HRT) (DOR: 17.8). Of greatest concern is that tests for heterogeneity were all above 50%, indicating that cutoffs used in these newer technologies were all very varied and not uniform across studies. Conclusions Glaucoma content experts need to establish uniform cutoffs for these newer technologies, so that studies that compare these technologies can be interpreted more uniformly. Nevertheless, synthesized data at this time demonstrate that amongst the newest technologies, OCT has the highest glaucoma diagnostic accuracy followed by GDx and then HRT.

Comparison of intraocular pressure post penetrating keratoplasty vs Descemet's stripping endothelial keratoplasty.

OBJECTIVE To compare the effect of Descemets stripping endothelial keratoplasty (DSEK) with penetrating keratoplasty (PKP) on intraocular pressure (IOP) and use of ocular antihypertensives. DESIGN Retrospective cohort study. PARTICIPANTS Thirty-five eyes in 33 patients undergoing PKP and 43 eyes in 38 patients undergoing DSEK were included in the analysis. Fifteen eyes undergoing PKP and 12 undergoing DSEK had diagnosed glaucoma. Patients undergoing corneal transplant because of trauma, keratoconus, pellucid marginal degeneration, or prior failed transplant were excluded. METHODS Charts were obtained for all patients who underwent PKP or DSEK by a single surgeon at the Ivey Eye Institute between 2003 and 2010. IOP and all IOP-lowering medications were recorded preoperatively and at 1, 4, 8, 12, and 24 weeks postoperatively. Complications, graft survival, and glaucoma surgeries were noted. RESULTS There was no significant difference in preoperative IOP between the 2 groups (p = 0.30). Postoperatively, IOP was significantly higher in the PKP group at 1 week (p < 0.01), 4 weeks (p < 0.01), and 8 and 12 weeks (p < 0.05), but not at 24 weeks (p = 0.62). Mean IOP increased significantly post-transplant in all groups (p < 0.05). In patients without glaucoma, postoperative IOP elevation requiring treatment occurred in 68% of PKP eyes and 23% of DSEK eyes. In patients with prior glaucoma, an increased requirement for ocular antihypertensives occurred in 60% of PKP eyes and 20% of DSEK eyes. Three trabeculectomies and 1 tube shunt were performed in the cohort with glaucoma undergoing PKP. No glaucoma surgery was required in the DSEK cohort. CONCLUSIONS Elevation of IOP requiring treatment occurred at a lower rate after DSEK compared with PKP. This difference was significant during the early postoperative course but nonsignificant at 24 weeks. Additional long-term studies on the effect of DSEK on glaucoma and IOP control are warranted.