Resolution of slit-lamp microscopy photography using various cameras

Abstract

Purpose: To evaluate the resolutions of slit-lamp microscopy photography using various cameras.

Design: Evaluation of diagnostic test or technology.

Participants: Healthy subjects were imaged with these adapted cameras through slit-lamp microscopy.

Methods: A total of 8 cameras, including 6 custom-mounted slit-lamp cameras and 2 commercial slit-lamp cameras, were tested with standard slit-lamp microscopy devices for imaging of the eye. Various magnifications were used during imaging. A standard resolution test plate was used to test the resolutions at different magnifications. These outcomes were compared with commercial slit-lamp cameras.

Main outcome measures: The main measurements included the display spatial resolutions, image spatial resolutions, and ocular resolutions. The outcome also includes the relationships between resolution and the pixel density of the displays and images.

Results: All cameras were successfully adapted to the slit-lamp microscopy, and high-quality ocular images were obtained. Differences in the display spatial resolutions were found among cameras [analysis of variance (ANOVA), P<0.05]. Higher display resolutions were found with cameras using the high-definition multimedia interface (HDMI) compared with others, including cameras in smart phones. The display resolutions of smart phone displays were greater than cameras with video graphics array displays. The display spatial resolutions were found as a function of display pixel density (r>0.95, P<0.05) and magnification (r>0.85, P<0.05). Different image spatial resolutions were found among cameras (ANOVA, P<0.05) as a function of image pixel density (r>0.98, P<0.05) and magnification (r>0.85, P<0.05). The commercial slitlamp with a single lens reflex camera yielded the highest image spatial resolution. However, the ocular resolution through binocular viewing of the slit-lamp microscopy was found to have the highest resolution compared with the display and image spatial resolutions of all of the cameras.

Conclusions: Several cameras can be adapted with slit-lamp microscopy for ophthalmic imaging, yielding various display and image spatial resolutions. However, the resolution seemed to not be as good as ocular viewing through the slit-lamp biomicroscope.