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Meixiao Shen, Jianhua Wang, Dexi Zhu, Ming Li, Michael R. Wang; Characterization of Human Ocular Surface Shape Using Ultra-long Scan Depth Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1747.
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To characterize human ocular surface shape using ultra-long scan depth spectral domain optical coherence tomography (UL-OCT).
A total of 10 eyes from 10 participants (6 males and 4 females, mean ± SD age: 31.2 ± 6.4 years) were recruited. A custom built UL-OCT (7.2mm scan depth and 6µm axial resolution) was used to image the entire ocular surface (18mm scan width) in both horizontal and vertical meridians. Custom image processing algorithm was applied to automatically yield the surface shape variables. These variables included sagittal depths at the central 6, 10, 12 and 15mm zones, the curvature and location of the corneal-scleral junction angle. A model surface eye was used to calibrate and validate the measurement. The junction angle was defined as the maximum change in the negative curvature (valley in the curvature profile, marked as green arrow in Figure 1, in diopter[D]).
The sagittal height profile of the model surface eye, determined by UL-OCT, agreed well with the known data. The overall root mean squared error between the UL-OCT and known data was 0.14µm. On the human eye, the sagittal depths at the 6mm and 10mm zones were significantly different between the horizontal and vertical meridians (t-test, P < 0.01, 0.59 ± 0.03mm vs. 0.60 ± 0.04mm at 6mm zone, 1.73 ± 0.08mm vs 1.87 ± 0.09 mm at 10mm zone). No significant differences of sagittal depths were found in other tested zones. The junction angle was detected on 5 eyes at the nasal side, none at the temporal side, 7 at the inferior side and 8 at the superior side. The location was found around 6-7mm chord distance from the apex. The averaged curvature at the detected junction angle was 12.99 ± 8.24D.
We have demonstrated the feasibility using UL-OCT for characterizing the ocular surface shape by measuring the sagittal depths and junction angle. UL- OCT is a powerful tool for providing the biometry of the peripheral cornea and sclera and may help in fitting contact lenses and lens design.
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