A comparison of retinal nerve fiber layer (RNFL) thickness obtained with frequency and time domain optical coherence tomography (OCT).

To diagnose glaucoma and other diseases of the retinal ganglion cell/ optic nerve, the thickness of the retinal nerve fiber layer (RNFL) is routinely measured with optical coherence tomography. Until recently, these OCT measurements were made almost exclusively with a time domain OCT (tdOCT) machine from a single manufacturer. Recently, a number of OCT machines, based upon an improved frequency domain OCT technology (fdOCT), have appeared. We compared measurements made using a new fdOCT machine to those from the older tdOCT machine. The results were comparable. More importantly, we learned that the key factor determining whether results from different machines will be comparable is the algorithm used to segment RNFL thickness, not the type of OCT.

Intra-observer and inter-observer reliability and reproducibility of slit-lamp-adapted optical coherence tomography for evaluation of anterior chamber depth and central corneal thickness.

BACKGROUND AND OBJECTIVE: To evaluate the intra-observer and inter-observer reproducibility of anterior chamber depth (ACD) and central corneal thickness (CCT) measurements taken by slit-lamp-adapted optical coherence tomography (SL-OCT) and to evaluate concordance of CCT and ACD values obtained by SL-OCT with gold standard devices. PATIENTS AND METHODS: Three images of each eye were taken by two different operators using SL-OCT. ACD and CCT values obtained by each operator were determined and compared to one another and to ultrasonic pachymetry (CCT) and axial OCT biometry (ACD) values obtained by a third, masked operator. Intra-observer and inter-operator reproducibility was assessed using the intraclass correlation coefficient (ICC). RESULTS: Forty-one eyes of healthy subjects were enrolled. Mean CCT was 0.556 +/- 0.020, 0.557 +/- 0.019, and 0.532 +/- 0.032 and mean ACD was 3.12 +/- 0.36, 3.13 +/- 0.38, and 3.50 +/- 0.44 for operators 1, 2, and 3, respectively (P < .001, for both CCT and ACD). Intra-operator reproducibility for CCT (ICC of 0.948 to 0.995) and ACD (ICC of 0.972 to 0.987) was excellent. CONCLUSION: SL-OCT provides highly reproducible measures for both CCT and ACD. SL-OCT yields higher values for CCT compared to ultrasonic pachymetry and lower values for ACD compared to axial OCT biometry. Caution should be taken when extrapolating these data into clinical practice until the differences between SL-OCT, axial OCT biometry, and ultrasonic pachymetry can be further elucidated.

Anatomic relationships between disc hemorrhage and parapapillary atrophy.

PURPOSE: Parapapillary atrophy (PPA) and disc hemorrhage (DH) are associated with glaucoma. We sought to determine whether they are anatomically related. DESIGN: Retrospective study. METHODS: All digital optic nerve stereophotographs obtained over a one-year period were screened for the presence of DH. Only patients with DH were included. The location of the greatest beta zone PPA width as defined by the radial distance between the scleral rim and the outer border of the beta zone was compared in each patient. The clock hour location of the DH was determined. Baseline central corneal thickness, intraocular pressure, vertical cup-to-disc ratio, and visual field indices were obtained. RESULTS: Photographs from 1,559 glaucoma patients were evaluated and 46 eyes with unilateral DH were identified; 42 (91.3%) had beta zone PPA and 38 eyes had asymmetric PPA width. DH occurred more frequently in the eye with the greater PPA width (29/38 eyes [76.3%]; kappa = 0.611; P < .001). The DH fell on the point of greatest PPA width in 10 (23.9%) of 42 eyes (P < .05, Fisher exact test) and within two clock hours of the greatest PPA width in 31 (73.8%) of 42 eyes (P < .001, Chi-square test). Logistic regression analysis determined that greater PPA width (odds ratio, 17.16; 95% confidence interval, 5.34 to 55.12; P < .001) was the only ocular characteristic to predict the laterality of the DH. CONCLUSIONS: DHs tend to occur in the eye with the greatest PPA width and usually are found within the region of its greatest width.