Jonathan Yeoh

Repeatability of manual subfoveal choroidal thickness measurements in healthy subjects using the technique of enhanced depth imaging optical coherence tomography.

PURPOSE The aim of this study was to investigate the repeatability of manual measurements of choroidal thickness in healthy subjects imaged on spectral domain optical coherence tomography (OCT) using the enhanced depth imaging (EDI) technique. METHODS Fifty consecutive, healthy, young, adult volunteers with no known eye disease were enrolled prospectively. Two good-quality horizontal and vertical line scans through the fovea were obtained for each eye. Using the manual calipers provided by the software of the proprietary device, two experienced OCT readers measured the subfoveal choroidal thickness (SFCT) of the horizontal and vertical line scans for all eyes. The readers were masked to each others readings. Intraobserver, interobserver, and intrasession coefficients of repeatability (CRs) were calculated. RESULTS Mean (standard deviation [SD]) age of the study subjects was 38 (5) years (range, 30-49 years). Mean (SD) subfoveal choroidal thickness was 332 (90) μm (right eyes) and 332 (91) μm (left eyes). Intraobserver CR was approximately 23 (95% confidence interval [CI], 19-26) μm, whereas interobserver and intrasession CRs were greater at 32 (95% CI, 30-34) and 34 (95% CI, 32-36) μm, respectively. There was no significant difference in SFCT between all pairs of SFCT measurements except for the two intrasession vertical line scans. CONCLUSION A change of >32 μm was likely to exceed interobserver variability in SFCT. Future studies are required to estimate the repeatability of SFCT measurements in patients with chorioretinal pathology.

Topographic Variation and Interocular Symmetry of Macular Choroidal Thickness Using Enhanced Depth Imaging Optical Coherence Tomography

PURPOSE To report and analyze factors influencing topographical and interocular variations in choroidal thickness (CT) in a healthy adult population. METHODS One hundred eyes of 50 healthy subjects underwent visual acuity and axial length measurements and optical coherence tomography (OCT) with enhanced depth imaging (EDI). CTs at the fovea and at 3 mm nasal, temporal, superior, and inferior to the fovea were measured manually. Topographic variation, relative interocular differences in CT and predictors of CT were analyzed. The relationships between interocular differences in CT and differences in age and interocular axial length were explored. RESULTS The mean (SD) foveal CT in the right and left eyes were 334 (95) and 333 (90) μm, respectively. For foveal CT, there was a high correlation between the two eyes (r = 0.90) with a relative interocular 95% limits of agreement of -80 to +83, and a median (range) absolute difference of 21 (0.4-135). There was no significant variation in the relative and absolute interocular differences in CT. Axial length was the main predictor of CT for nasal and foveal CT. Symmetry in CT in the horizontal and vertical meridians was seen in eyes with axial length shorter than 23.50 mm (P < 0.05). CONCLUSIONS There was no significant relative interocular difference in CT. Axial length contributes to some of the variances in CT but has a significant influence on the CT profile. Although relative interocular difference is not significant, absolute interocular differences in CT may reach 85 μm.

Use of spectral-domain optical coherence tomography to differentiate acquired retinoschisis from retinal detachment in difficult cases

Purpose: This study presents a series of 10 patients who posed a diagnostic challenge regarding the diagnosis of acquired retinoschisis (RS) or retinal detachment (RD), where spectral-domain optical coherence tomography (OCT) with the Spectralis HRA and OCT device (Heidelberg Engineering, Heidelberg, Germany) was able to help make a correct diagnosis. Methods: Ten patients (five with acquired RS and five with RD) were referred to a vitreoretinal clinic at Moorfields Eye Hospital for definitive diagnosis and further management. All patients underwent scans with the Spectralis HRA and OCT device. Results: The Spectralis HRA and OCT was able to make a clear diagnosis of RS or RD in all patients. Of the five patients with RS confirmed on OCT, two were referred with RD, and of the five patients with RD, four were referred with RS. New OCT features of RS include the double schisis cavity phenomenon, intraretinal pillars through the schisis cavity, and irregularity of the inner surface of the attached outer leaf. Conclusion: Spectral-domain OCT is a useful tool in distinguishing RS from RD, eliminating previous diagnostic uncertainty. The Spectralis HRA and OCT device has the added advantages of being able to reliably image anterior retinal pathology and produce high-definition images.