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In conventional fundus photography, illuminating light is delivered to the interior of the eye through the pupil. To avoid reflection from cornea and crystalline lens, peripheral area of the pupil is used for delivering illumination light and only the central part of the pupil can be used for collecting imaging light. Therefore, the optical design of conventional fundus cameras is sophisticated, the field of view is limited, and pupil dilation is required for evaluating the retinal periphery which is frequently affected by diabetic retinopathy (DR), retinopathy of premature (ROP), and other chorioretinal conditions. Trans-scleral illumination has been proposed as one alternative illumination method to achieve wide field fundus examination not requiring pharmacologic pupil dilation. However, clinical deployment of trans-scleral illumination failed due to the contact mode illumination and imaging, and complication of instrument operation. Here we report a nonmydriatic wide field fundus camera employing trans-pars-planar illumination which delivers illuminating light through the pars plana, an area outside of the pupil without contacting the eye. Trans-pars-planar illumination frees the entire pupil for imaging purpose only, and thus wide field fundus photography can be readily achieved with less pupil dilation. For proof-of-concept testing, using all off-the-shelf components a prototype instrument that can achieve 90° fundus view coverage in single-shot fundus images, without the need of pharmacologic pupil dilation was demonstrated.
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