Faculty Bibliography

OBJECTIVE: To evaluate optical coherence tomography (OCT), a novel noncontact and noninvasive imaging technique, for the diagnosis and quantitative characterization of epiretinal membranes. METHODS: Optical coherence tomography is similar to an ultrasound B-scan, except that light rather than sound is used, which enables higher resolution. Over a 2-year period, OCT was used to examine 186 eyes of 160 patients who had a diagnosis of an epiretinal membrane. Optical coherence tomograms were correlated with visual acuity, slit-lamp biomicroscopy, fluorescein angiography, and funds photography. RESULTS: Based on OCT, the epiretinal membrane was clearly separated from the retina with focal points of attachment in 49 eyes and globally adherent (no observed separation) in 125 eyes. Globally adherent membranes were associated with the following features: macular pseudohole (32 eyes), a difference in optical reflectivity between the membrane and retina (65 eyes), and/or a visible membrane tuft or edge (92 eyes). The membrane was undetectable on OCT in 12 eyes. The membrane thickness (mean +/- standard deviation) was 61 +/- 28 microns in the 169 eyes in which the thickness could be measured with OCT. Mean central macular thickness measured with OCT correlated with visual acuity (R2 = 0.73). CONCLUSION: Optical coherence tomography was able to provide a structural assessment of the macula that was useful in the preoperative and postoperative evaluation of epiretinal membrane surgery. Quantitative measurements and the assessment of membrane adherence with OCT may be useful in characterizing the surgical prognosis of eyes with an epiretinal membrane.

PURPOSE: Optical coherence tomography (OCT) is a new technology that uses near-infrared light in an interferometer to produce approximately 10-microns resolution cross-sectional images of the tissue of interest. The authors performed repeated quantitative assessment of nerve fiber layer thickness in individuals with normal and glaucomatous eyes, and they evaluated the reproducibility of these measurements. METHODS: The authors studied 21 eyes of 21 subjects by OCT. Each subject underwent five repetitions of a series of scans on five separate occasions within a 1-month period. Each series consisted of three circular scans around the optic nerve head (diameters, 2.9, 3.4, and 4.5 mm). Each series was performed separately using internal (fixation with same eye being studied) and external (fixation with contralateral eye) fixation techniques. The eye studied and the sequence of testing were assigned randomly. RESULTS: Internal fixation (IF), in general, provides a slightly higher degree of reproducibility than external fixation (EF). Reproducibility was better in a given eye on a given visit than from visit to visit. Reproducibility as measured by intraclass correlation coefficients were as follows: circle diameter (CD), 2.9 mm, 0.51/0.57 (normal/glaucoma) (IF), 0.43/0.54 (EF); CD, 3.4 mm, 0.56/0.52 (IF), 0.43/0.61 (EF); CD, 4.5 mm, 0.53/0.43 (IF), 0.42/0.49 (EF). CONCLUSIONS: Nerve fiber layer thickness can be reproducibly measured using OCT. Internal is superior to external fixation; each circle diameter tested provides adequate reproducibility.

The ocular hypotensive efficacy and safety of brimonidine tartrate 0.2%, a highly selective alpha 2-adrenergic agonist, was compared with that of timolol 0.5%, a nonselective beta-blocker in two multicenter, randomized, double-masked studies. Combined data from a 12-month completed study and 6-month interim data from an ongoing study are reported. Efficacy and safety were evaluated at baseline, weeks 1 and 2, and months 1, 2, 3, 6, 9, and 12. Intraocular pressure (IOP) was measured at peak (2 hours after the morning dose) and trough (12 hours after the evening dose). Patients (n = 926) instilled either brimonidine tartrate 0.2% or timolol maleate 0.5% twice daily. At peak, the mean decreases from baseline IOP ranged from 5.9 +/- 3.2 mm Hg to 7.6 +/- 3.6 mm Hg for brimonidine and 6.0 +/- 3.4 mm Hg to 6.6 +/- 3.6 mm Hg for timolol (p < 0.001 within groups compared with baseline). No significant between-group differences were seen at peak except for weeks 1 and 2 and month 3 (p < or = 0.04), when brimonidine had lower mean IOP. At trough the mean decreases from baseline ranged from 3.7 +/- 4.0 mm Hg to 5.0 +/- 3.0 mm Hg for brimonidine and 5.9 +/- 3.4 to 6.6 +/- 3.0 for timolol. A significant between-group difference was seen at trough at all visits (< 0.001), when timolol had a lower mean IOP. Brimonidine and timolol showed sustained efficacy. Both drugs were well-tolerated. The brimonidine group had more ocular allergy, oral dryness and conjunctival follicles. The timolol group had more burning and stinging. In the brimonidine group, 38/513 (7.4%) discontinued treatment due to ocular allergy. The timolol group had significantly lower mean heart rate compared to baseline. The effect on blood pressure was minimal for both drugs. Brimonidine showed efficacy similar to timolol and a relatively low rate of ocular allergy. Brimonidine 0.2% administered twice daily is an effective and safe ocular hypotensive agent that maintains IOP-lowering in chronic use.

OBJECTIVE: The authors used optical coherence tomography (OCT), a new technique for cross-sectional imaging of the retina, to morphologically study eyes with nonexudative and exudative age-related macular degeneration (AMD). In patients with untreated exudative AMD, OCT was compared with fluorescein angiography in the identification and classification of choroidal neovascularization (CNV). METHODS: Optical coherence tomography imaging is analogous to ultrasound, except that the use of light rather than sound enables higher longitudinal resolution with a noncontact and noninvasive measurement. Optical coherence tomography was performed on 391 patients with the clinical diagnosis of AMD and was compared with conventional clinical examination to establish the cross-sectional morphology of different lesions and to develop a classification scheme for CNV. Optical coherence tomograms and fluorescein angiograms then were reviewed and correlated independently in 90 eyes of 86 patients who had exudative AMD without previous laser treatment. RESULTS: Pigmentary changes, soft drusen, and detachments of the neurosensory retina and retinal pigment epithelium all had distinct presentations on OCT. Subretinal and intraretinal fluid caused changes in retinal thickness or elevation that could be quantified directly from the images. Choroidal neovascularization was evident in the tomograms as a thickening and fragmentation of a reflective layer, which corresponded to the retinal pigment epithelium and choriocapillaris. Changes in the reflection from this layer were observed during the progression of neovascularization, and after laser photocoagulation treatment. Classic CNV consistently presented with well-defined boundaries on OCT, whereas occult CNV had a variable cross-sectional appearance. CONCLUSIONS: Optical coherence tomography was useful in quantitatively evaluating subretinal and intraretinal fluid, assessing possible subfoveal involvement of neovascularization, and in monitoring CNV before and after laser photocoagulation. Optical coherence tomography was unable to detect CNV beneath serous pigment epithelial detachments. Optical coherence tomography may have potential in accurately defining the boundaries in a subset of angiographically occult CNV.

BACKGROUND: The syndrome of inflammatory precipitates on the trabecular meshwork is a rare form of inflammatory glaucoma that was described by Chandler and Grant in 1968 and subsequently given the eponym Grant's syndrome. METHODS: We present two cases of elevated intraocular pressure associated with inflammatory precipitates on the trabecular meshwork in otherwise relatively quiet eyes, consistent with Grant's syndrome. We review the epidemiology, clinical features, and mechanism of this syndrome. In addition, we demonstrate the use of ultrasound biomicroscopy for imaging angle inflammatory precipitates. RESULTS: Our patients demonstrate the cardinal features of Grant's syndrome, including acute onset, significant elevation of tension, trabecular meshwork precipitates in an otherwise quiet eye, limited response to typical pressure lowering agents, excellent response to topical steroids, evidence of recurrence with bilaterality, and systemic association with sarcoidosis. Ultrasound biomicroscopy proves to be a useful adjunct for pathologic imaging. CONCLUSIONS: The syndrome of glaucoma with inflammatory precipitates on the trabecular meshwork is a rare entity that should be considered as a possible diagnosis of elevated intraocular pressures in otherwise apparently quiet eyes.

BACKGROUND AND OBJECTIVE/OBJECTIVE:Acute and long-term effects of contact transscleral cyclodiathermy (CTCD) were studied in rabbits. MATERIALS AND METHODS/METHODS:In the acute phase, three evenly spaced applications were placed at the limbus in each of four quadrants using the Ophthalmic Diathermy TR4000 (MIRA, Inc., Waltham, MA). Each quadrant of 17 eyes of 13 Dutchbelted rabbits was treated with radio frequencies (RFs) of 1.0 to 4.5, for times of 0.5, 0.75, 1.0 to 3.0, and 4.0 to 10.0 seconds. Eyes were then immediately enucleated and fixed in Karnovsky's solution after the rabbits had been sacrificed with 3 ml of pentobarbital sodium. In the longitudinal phase, four groups of six rabbits each were treated with 20 evenly spaced applications at the limbus at one of four settings: 1.5 RFs/4 seconds, 2.0 RFs/3 seconds, 2.5 RFs/2 seconds, or 3.0 RFs/2 seconds. Intraocular pressures were measured on alternate days for 1 week prior to treatment and for 4 weeks after treatment, following which the eyes were enucleated and fixed in Karnovsky's solution. RESULTS:Gross examination of the acute phase eyes revealed blanching of the ciliary processes at RF settings of 2.5 and higher with exposure times of 1.5 seconds or longer. Gross and light microscopic studies showed that levels of destruction correlated positively with RF settings and exposure times. Higher RF levels resulted in scleral coagulation necrosis on light microscopy. In addition, there was coagulation necrosis of the pigmented and nonpigmented ciliary epithelium and stroma. Longitudinal phase study showed a significant decrease in intraocular pressure (IOP) in the four groups of rabbits treated over the 4-week follow-up period (P = .005, multivariate analysis of variance [MANOVA]). Rabbits treated at higher RF levels sustained a greater IOP-lowering effect (P = .025, MANOVA). Gross and light microscopic examination revealed focal atrophy, fusion, and fibrosis of the ciliary processes. CONCLUSION/CONCLUSIONS:Nonpenetrating CTCD results in focal destruction of the ciliary body in rabbits. The authors found that significant reduction in IOP was possible over the 4-week follow-up period in the Dutch-belted rabbits treated, with greater IOP and tissue effects at higher RF settings.