Faculty Bibliography

A retinal tracker was integrated into a third-generation commercial clinical optical coherence tomography system (Stratus OCT) manufactured by Carl Zeiss Meditec Inc. (CZMI). The instrument, called tracking optical coherence tomography (TOCT), uses a secondary sensing beam in a confocal reflectometer and steering mirrors to compensate eye motion with a closed loop bandwidth of 1 kHz and a lateral accuracy of less than 15 mu m. Imaging and tracking control systems have been integrated into a single platform and user interface in order to admit new imaging capabilities and considerable simplification in acquisition of clinical data. The system was configured to acquire three-dimensional retinal OCT maps through all subject eye movements and blinks.

PURPOSE: To investigate the structure-function relationship between optical coherence tomography (OCT) macular retinal and peripapillary nerve fiber layer (NFL) thickness and automated visual field (VF) findings. DESIGN: Cross-sectional observational study. METHODS: Retrospective institutional study where 150 consecutive eyes (101 subjects) from a glaucoma service were included. All the participants had full ophthalmic evaluation, VF testing and prototype OCT scanning at the same visit. Orthogonal OCT macular analysis was obtained to maximize the sampling of the area of interest. Pearson age-adjusted correlation was determined between macular retinal thickness and peripapillary NFL thickness. Area under the receiver operator characteristics (AROC) curves for the association between macular retinal thickness and peripapillary NFL thickness and VF findings were calculated in a subgroup of eyes without VF defect and eyes with VF defect confined to one hemifield. RESULTS: The correlation between macular retinal and peripapillary NFL measurements ranged between r =.27 to.54 for quadrants,.44 to.55 for hemiretina, and.52 for the overall mean. Areas under the receiver operator characteristics for macular thickness were higher in areas corresponding to the VF defect location than the noncorresponding locations. Areas under the receiver operator characteristics for peripapillary NFL thickness were higher than for the macular retinal thickness. Including both macular retinal thickness and peripapillary NFL thickness measurements in the logistic regression model yielded AROCs (range:.69 -.77) similar to those found for the peripapillary NFL alone. CONCLUSION: Macular retinal thickness, as measured by OCT, was capable of detecting glaucomatous damage and corresponded with peripapillary NFL thickness; however, peripapillary NFL thickness had higher sensitivity and specificity for the detection of VF abnormalities.

PURPOSE: The measurement reproducibility of the third generation of commercial optical coherence tomography, OCT-3 (StratusOCT, software ver. A2, Carl Zeiss Meditec Inc., Dublin, CA) was investigated. The nerve fiber layer (NFL) thickness, macula thickness map, and optic nerve head (ONH) parameters in normal eyes were studied. METHODS: Ten normal subjects were imaged six times (three before and three after dilation) per day, and the series was repeated on three different days. The order of the scans before pupil dilation was randomized in each of the 3 days of scanning. After pupil dilation, the scans were also randomized in each of the 3 days of scanning. Each series was performed separately for standard-density (128 A-scans per macular and ONH image and 256 A-scans per NFL image) and high-density (512 A-scans per image for all three scan types) scanning. RESULTS: The mean macular thickness was 235 +/- 9.8 micro m. A-scan density (or image acquisition speed) had a statistically significant effect (P < 0.05) on the reproducibility of the mean macular thickness, macular volume, and a few sectors of the macular map. No significant dilation effect was found for any of the macular parameters. The best intraclass correlation coefficient (ICC; 94%) for macular scans was found for dilated high-density scanning, with an intervisit SD of 2.4 micro m and an intravisit SD of 2.2 micro m. The mean NFL thickness for standard scanning was 98 +/- 9 micro m. NFL reproducibility showed mixed results and had interactions between scan density and dilation for some parameters. For most of the NFL parameters, reproducibility was better with dilated standard-density scanning. The mean NFL thickness ICC for dilated standard scanning was 79%, with an intervisit SD of 2.5 micro m and an intravisit SD of 1.6 micro m. For the ONH analysis, the reproducibility was better for dilated standard-density scanning for almost all the parameters, except for disc area, horizontal integrated rim volume, and vertical integrated rim area, which were better before dilation. The best reproducibility was found for cup-to-disc ratio (ICC = 97%, with intervisit SD of 0.04 micro m and intravisit SD of 0.02 micro m). CONCLUSIONS: StratusOCT demonstrated reproducible measurements of NFL thickness, macular thickness, and optic nerve head parameters. The best reproducibility was found for dilated standard scanning for NFL and ONH parameters and for dilated high-density scanning for macular parameters.

Ultrasound biomicroscopy technology has become an indispensable tool in qualitative and quantitative assessment of the anterior segment. Advances in soft-ware design and algorithms will improve theoretical understanding of the pathophysiology of anterior segment disorders. Future applications of quantitative techniques will yield important information regarding mechanisms of angle closure, improving understanding of the dynamic functions of the iris,accommodation, presbyopia, and other aspects of anterior segment physiology and pathophysiology.