Scleral thickness in normal Indian eyes measured using spectral domain anterior segment optical coherence tomography.

Purpose: To establish normative data on anterior scleral thickness using the spectral domain anterior segment optical coherence tomography (AS-OCT). Methods: In total, 200 eyes of 100 healthy subjects underwent AS-OCT scans in the temporal and nasal quadrants. The scleral + conjunctival complex thickness (SCT) was measured by a single examiner. Mean SCT was analyzed for differences across age groups, gender, and location (nasal versus temporal). Results: Mean age was 46.4 ± 18.3 (21-84) years; male to female ratio was 54:46. Mean SCT (nasal + temporal) of the right eye (RE) was 682.3 ± 64.2 µm in males and 660.6 ± 57.1 µm in females. In the left eye (LE), it was 684.6 ± 64.9 µm in males and 661.8 ± 49.3 µm in females. These differences between male and female for both eyes were statistically significant (P = 0.006 and P = 0.002). The mean SCT of temporal and nasal quadrants in the RE was 678.54 ± 57.50 and 666 ± 66.2 µm, respectively. In the LE, the temporal mean SCT quadrant was 679.6 ± 55.8 µm, and the nasal was 668.6 ± 63.6 µm. Age had a negative correlation with SCT (-0.62 µm/year; P = 0.03), and males had a higher temporal SCT than females (22 µm higher; P = 0.03). After adjusting for age and gender in a multivariate analysis, temporal SCT was significantly (P < 0.001) higher than nasal SCT. Conclusion: In our study, mean SCT decreased with age and males had a higher temporal SCT. This is the first study to evaluate scleral thickness in the Indian population, and the data can be used as a baseline for comparing variations in scleral thickness in disease.

Optical coherence tomography angiography of perilimbal vasculature: validation of a standardised imaging algorithm.

PURPOSE: To test the reliability and accuracy of a standardised non-invasive imaging algorithm using optical coherence tomography angiography (OCTA) in detecting and quantifying pharmacologically induced changes in the perilimbal vasculature. METHODS: In this prospective observational imaging study, 370 angiograms of 15 normal eyes and 10 eyes with nasal pterygiums were obtained using a commercially available OCTA system with split-spectrum amplitude-decorrelation angiography technology. Postprocessing of the images to quantify the area occupied by the blood vessels was performed using the Fiji software. The main outcome measures were reliability (intraobserver and interobserver agreement) and accuracy of the standardised algorithm in detecting and quantifying relative change (vasoconstriction and vasodilatation) in the area occupied by the blood vessels after instillation of topical vasoconstrictors. RESULTS: The intraclass correlation coefficients for intraobserver and interobserver agreement were 0.91 and 0.88 (good to excellent), respectively. In normal eyes, significant vasoconstriction was noted at 5 min (35%-47%) after application of eye-drops, which peaked at 10 min (43%-63%) and was sustained until 20 min (35%-51%), followed by gradual recovery. Greatest effect was noted with a combination of 5% phenylephrine and 0.15% brimonidine tartrate (BT) eye-drops as compared with either one or two drops of BT alone, both at the 10 min (p=0.0058) and 20 min (p=0.0375) time points. This dose-dependent temporal trend was replicated in eyes with primary nasal pterygium (p=0.31). CONCLUSIONS: The findings suggest that OCTA can reliably and accurately detect and quantify relative changes in the perilimbal vasculature in both normal eyes and in eyes with pterygium.