Sanjay Asrani

Large diurnal fluctuations in intraocular pressure are an independent risk factor in patients with glaucoma.

Purpose: To study the risk associated with diurnal intraocular pressure (IOP) variations in patients with open‐angle glaucoma. Patients and Methods: Sixty‐four patients (105 eyes) from the practices of two glaucoma specialists successfully performed home tonometry with a self‐tonometer five times a day for 5 days. All patients had open‐angle glaucoma and documented IOP below 25 mm Hg over a mean follow‐up period of 5 years. Baseline status and time to progression of visual field loss were identified from the clinical charts. The level and variability of diurnal IOP obtained using home tonometry were characterized. Risk of progression was analyzed using a nonparametric time‐to‐event model, incorporating methods for correlated outcomes. Results: Although mean home IOP and baseline office IOP were similar (16.4 ± 3.6 mm Hg and 17.6 ± 3.2 mm Hg, respectively), the average IOP range over the 5 days of home tonometry was 10.0 ± 2.9 mm Hg. Baseline office IOP had no predictive value (relative hazard, 0.98). The diurnal IOP range and the IOP range over multiple days were significant risk factors for progression, even after adjusting for office IOP, age, race, gender, and visual field damage at baseline (relative hazards [95% confidence intervals], 5.69 [1.86, 17.35] and 5.76 [2.21, 14.98]). Eighty‐eight percent of patients in the upper twenty‐fifth percentile of IOP and 57% of patients in the lower twentyfifth percentile progressed within 8 years. Conclusions: In patients with glaucoma with office IOP in the normal range, large fluctuations in diurnal IOP are a significant risk factor, independent of parameters obtained in the office. Fluctuations in IOP may be important in managing patients with glaucoma. Development of methods to control fluctuations in IOP may be warranted.

Quantitative detection of glaucomatous damage at the posterior pole by retinal thickness mapping: A pilot study

OBJECTIVE The posterior pole ganglion cell bodies form a substantial fraction of the retinal thickness, prompting the authors to study the feasibility of detecting, by scanning retinal thickness analysis, retinal changes at the posterior pole due to glaucomatous damage. STUDY DESIGN Nonconsecutive case series. PARTICIPANTS One or both eyes of patients with chronic open-angle glaucoma who presented with either a superoinferior asymmetry in visual fields or a localized field loss or a nerve fiber layer defect visible on photography were recruited. Twenty-nine eyes of 18 patients were studied. INTERVENTIONS A laser slit was projected on the retina and scanned, in 400 msec, across a 2- x 2-mm area of the fundus, yielding optical cross-sections that were digitally recorded. Nine such scans covered the central 20 degrees of the fundus. The optical cross-sections were analyzed by an operator-free algorithm to yield a three-or two-dimensional color map. The asymmetry (difference) between the visual sensitivity of the upper and lower hemifields was compared with the asymmetry in retinal thickness deviation from normal. RESULTS Large losses (up to 34%) in retinal thickness were detected at the posterior pole of patients with glaucoma due to the loss of ganglion cells and nerve fibers. A statistically significant correlation was found between the asymmetry in visual sensitivity loss and the asymmetry in deviation from normal thickness (r = 0.72; P < 0.0005). CONCLUSIONS Mapping of the retinal thickness may provide a sensitive method for the detection and monitoring of early glaucomatous tissue loss in the posterior pole, which is unique due to the combination of (1) the direct measurement of neuroretinal loss in the central field of vision; (2) the mapping capability; and (3) the rapid image acquisition.

Optical coherence tomography in the eyes of normal children.

OBJECTIVE To collect a normative database of macular thickness, retinal nerve fiber layer (RNFL) thicknesses, and optic nerve topography in the healthy eyes of children aged 3 to 17 years using optical coherence tomography (OCT) measurements. METHODS Scans were obtained for 286 healthy children (black, 114; white, 154; other, 18). Each child had a dilated eye examination, an axial length measurement using the IOL Master (Carl Zeiss Meditec, Dublin, California), and OCT measurements using the fast macular map, fast RNFL thickness, and fast optic disc protocols of the Stratus OCT (OCT-3; Carl Zeiss Meditec). RESULTS Black children had smaller macular volume and foveal thickness, larger RNFL thickness, and larger cup-disc area ratios compared with white children. Macular volume and average outer macular thickness correlated negatively with axial length in white children. Foveal thickness correlated positively with age in black children only. Average RNFL correlated negatively with axial length in white children only (P < .05 for all). Normative data for all variables were recorded and compared with reported adult values. CONCLUSIONS Stratus OCT-3 measurements of macular and RNFL thickness and optic nerve topography vary with race, axial length, and age in healthy children. Normative pediatric OCT data should facilitate the use of OCT in assessing childhood glaucoma and other diseases.

Imaging the Ocular Anterior Segment With Real-Time, Full-Range Fourier-Domain Optical Coherence Tomography

We have demonstrated a novel Fourier-domain optical coherence tomography system and signal-processing algorithm for full-range, real-time, artifact-free quantitative imaging of the anterior chamber. Cross-sectional full-range images comprising 1024 x 800 pixels (axial x lateral) were acquired and displayed at 6.7 images/s. Volumetric data comprising 1024 x 400 x 60 pixels (axial x lateral x elevation) were acquired in 4.5 seconds with real-time visualization of individual slices and 3-dimensional reconstruction performed in postprocessing. Details of the cornea, limbus, iris, anterior lens capsule, trabecular meshwork, and Schlemms canal were visualized. Quantitative surface height maps of the corneal epithelium and endothelium were obtained from the volumetric data and used to generate corneal thickness maps.

Glaucoma after Congenital Cataract Surgery

OBJECTIVES To study eyes that manifested glaucoma after congenital cataract surgery and to identify factors that might lead to better diagnosis and treatment of such glaucoma. DESIGN A retrospective review of patients treated for glaucoma that developed after congenital cataract surgery. RESULTS Sixty-four eyes of 38 patients were studied. Open-angle glaucoma was the more frequent type of glaucoma (51 eyes, 79.7%). Glaucoma was diagnosed a mean interval of 12.2 years after cataract surgery, but it could occur at any time from months to decades after the cataract surgery. Medications alone were successful in intraocular pressure control in 21 (63.6%) of 33 eyes, and additional surgical procedures resulted in successful intraocular pressure control in 11 of 14 eyes in which they were performed. CONCLUSION The authors cannot predict in which eyes glaucoma will develop after surgery for congenital cataracts. Once detected, the glaucoma can be treated successfully in the majority of cases. Careful follow-up, including examinations with the patient sedated or anesthetized as needed, is required.

Intraocular Pressure Monitoring Sensors

Continuous measurement of intraocular pressure is important in the detection and treatment of glaucoma. While a point check of intraocular pressure in a doctors office using indirect measurements such as the tonometer is helpful, it is inadequate to track circadian variation. Circadian variation is an independent risk factor in addition to elevated pressure levels. This paper is aimed at providing an up-to-date review of various intraocular pressure sensing techniques and in vivo sensor design approaches. The basic operating principles of various implantable sensors are reviewed and categorized into groups to delineate their differences. A discussion is presented identifying the drawbacks of existing designs and key design questions are proposed for future progress.

High failure rate associated with 180 degrees selective laser trabeculoplasty.

Purpose:To determine the efficacy of selective laser trabeculoplasty (SLT) in a tertiary care referral center. Patients and Methods:In this retrospective study of selective laser trabeculoplasty performed by five physicians, 94 eyes from 94 patients were included. A majority (83/92, 90%) underwent 180° selective laser trabeculoplasty. Selective laser trabeculoplasty failure was defined in two ways: (1) IOP decrease <3 mm Hg (definition one), or (2) IOP decrease <20% (definition two), on two successive visits ≥4 weeks after SLT. Results:Overall failure rates were 68% (64/94) and 75% (70/94) (by definitions one and two, respectively). By survival/life-table analysis, mean time to failure was 6 months and 5.5 months, by definitions one and two, respectively. By the end of the study (14.5 months), the failure rates were 86% and 92% by definitions one and two, respectively. By each definition, in both univariable and multivariable analysis, only lower baseline IOP was a significant predictor of failure. Conclusions:Selective laser trabeculoplasty had an overall low success rate in our tertiary clinic population, with overall failure rates of 68% to 74% in those who underwent 180° selective laser trabeculoplasty.

Detailed visualization of the anterior segment using fourier-domain optical coherence tomography.

OBJECTIVE To study details of the anterior chamber drainage angle using Fourier-domain optical coherence tomography in healthy subjects and patients with angle abnormalities. METHODS A high-speed anterior segment optical coherence tomography prototype was developed using a 1310-nm-wavelength swept light source. Six healthy subjects and 6 patients with glaucoma were imaged in an observational cross-sectional study. RESULTS Schlemms canal and the trabecular meshwork were visualized in all of the patients. Fifteen-millimeter scans enabled entire anterior segment visualization providing configuration details of the iris with respect to the angle. Four-millimeter scans permitted detailed views of the angle configuration and its structures. Volumetric imaging was possible and Schlemms canal was visualized along part of its circumference. CONCLUSION Anterior segment Fourier-domain optical coherence tomography permits detailed noncontact imaging of the angle and its structures, providing a tool to improve our understanding of the pathogenesis of narrow-angle glaucoma.

Noninvasive mapping of the normal retinal thickness at the posterior pole.

OBJECTIVE Objective and sensitive measurements of the retinal thickness at the posterior pole are useful to detect and delineate macular edema or retinal atrophy. The authors therefore developed an instrument, the Retinal Thickness Analyzer (RTA), to map the retinal thickness rapidly. The RTA was used to study the normal thickness at the posterior pole and to provide a pilot baseline. DESIGN Cross-sectional study. METHODS A green (540-nm) laser slit was focused on the retina via a scanning mirror placed at the conjugate plane of the pupil. The intersection between the laser slit and the retina was viewed at an angle and recorded by a video camera. Nine scans, each acquired in 200 to 400 msec, covered the central 20 degrees of the fundus. PARTICIPANTS The posterior pole was mapped in 29 normal subjects 19 to 76 years of age (mean, 48 years). RESULTS The thickness maps matched the posterior pole anatomy. Points with maximum thickness were located in the perifovea in a C-shaped manner extending from the disc to above and below the fovea. The local variation (standard deviation) in retinal thickness among the subjects was, on average, 15 microns. Age, gender, and race did not have a large effect (< 35 microns) on the values. CONCLUSIONS Rapid scanning thickness analysis with the RTA provides a detailed map of the retinal thickness. The relatively narrow range of thickness values in normal subjects indicates that the method may provide a sensitive detection of pathologic thickening or thinning of the retina.

Application of Rapid Scanning Retinal Thickness Analysis in Retinal Diseases

PURPOSE The authors have further developed their method of retinal thickness analysis to rapidly generate multiple optical cross sections of the retina and provide thickness maps at the posterior pole. The potential use of this method was evaluated in a number of macular disorders. METHODS A commercial prototype of the scanning retinal thickness analyzer was used to examine patients with a variety of macular diseases. A laser slit beam was projected on the retina and scanned across a 2- X 2-mm retinal area in 200 to 400 msec. The images of the intersection of the laser slit beam with the retina were recorded digitally and used for visualization of disease. Nine scans were combined, and an operator-free algorithm generated a three-dimensional thickness map at the posterior pole. RESULTS Cysts could be visualized in macular edema associated with diabetes mellitus and with retinal vein occlusion. The retinal thickness map quantitated the location, extent, and height of the edema. In serous detachment, the extent and the height of the retinal pigment epithelial elevation could be documented. In cases of suspected macular holes and pseudoholes, the diagnosis was considered more reliable than with conventional biomicroscopy. The extent of epiretinal membranes, the sites of adherence, and associated intraretinal cystic changes were identified. In glaucoma, the anatomic course of localized loss of neuronal retinal tissue could be traced. CONCLUSIONS Scanning retinal thickness analysis provided multiple optical cross sections of the retina and yielded information useful in the diagnosis and monitoring of macular diseases. The three-dimensional thickness map provided quantitative information that may be useful for clinical management.