The optical resolution of the camera is:
Horizontal: 12 μm or better
Vertical: 23 μm or better
However, the above values are simply based on a chart used to measure optical resolution and do not represent the actual resolution for fundus blood vessels. The spatial resolution expected as an answer to this question would be the effective resolution indicating how fine a blood vessel's blood flow distribution and changes can be depicted. In practice, however, this performance is highly dependent on the subject's fixation ability, and if fixation is not stable during measurement, fine vascular patterns cannot be depicted. In examples where fine blood vessels on the optic nerve head of subjects with relatively stable fixation were depicted, it appears that vascular cross-sections could be resolved down to approximately 3 pixels, so if the full width at half maximum of the vascular cross-sectional image is taken as the effective vessel diameter, blood vessels down to approximately 20 microns in diameter can be resolved.
However, as ophthalmologists may have experienced, patients who actually visit ophthalmology clinics often have reduced visual acuity, resulting in unstable fixation, and it is often not possible to capture vascular images this clearly.
For these reasons, when presenting the above resolution in papers or similar publications, we recommend adding the following note:
*This is the effective resolution derived from the optical system and image sensor, and does not represent the resolution of observed blood vessels.
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