Abstract
Purpose :
High-resolution photography of the ocular surface is challenging due to the convex shaped eyeball, which results in a limited, in-focus field-of-view when imaged onto a plane image sensor. An imaging system was developed featuring a novel lens design to solve this mapping problem with one snapshot.
Methods :
The imaging system comprises a custom-made objective to map the eye’s convex surface onto a plane image sensor. The optical unit features a set of seven lenses and can be used on-axis in a compact design. The lateral imaging resolution was determined in the central and peripheral locations of the ocular surface to be 15 µm. Furthermore, the optical unit features an integrated fixation target and a LED ring to control additional imaging parameters. The optical unit is aligned to the patient’s eye using a motorized three-axis stage. This stage is controlled by custom-made software that allows a semi-automated capturing of standardized ocular surface images in terms of position, illumination and focus. The images were further processed to enhance vascular contrast or extract ocular surface imaging biomarkers, e.g., redness.
Results :
A photograph of a healthy volunteer’s eye is shown exemplarily in Fig. 1A. The visible ocular surface was imaged with a field-of-view of 21.3 x 16 mm, where the cornea, sclera, limbus and tear film are entirely in focus. Imaging is supported by eye-tracking and auto-focus to ensure operator-independent, standardized imaging, where the iris is centered. The high-resolution images can further be enhanced using image processing. Figure 1B demonstrates the photograph’s capabilities to extract the ocular surface vasculature over the entire field of view, showing small limbal vessels and larger peripheral vessels. Standardized illumination allows to extract ocular redness from the sclera and could be used for objective, image-based redness grading, as indicated in Fig. 1C. Other ocular surface imaging biomarkers might be measured with great detail, see Fig. 1D.
Conclusions :
An imaging system for standardized color photography was developed, which can image the entire visible ocular surface in-focus in a single shot. In addition, the images were enhanced to demonstrate the suitability of the system to visualize and quantify various ocular surface imaging biomarkers such as vascularization, conjunctival redness, or the extraction of geometric features.
This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.