Trans-pars-planar illumination enables a 200° ultra-wide field pediatric fundus camera for easy examination of the retina

Abstract

This study is to test the feasibility of using trans-pars-planar illumination for ultra-wide field pediatric fundus photography. Fundus examination of the peripheral retina is essential for clinical management of pediatric eye diseases. However, current pediatric fundus cameras with traditional trans-pupillary illumination provide a limited field of view (FOV), making it difficult to access the peripheral retina adequately for a comprehensive assessment of eye conditions. Here, we report the first demonstration of trans-pars-planar illumination in ultra-wide field pediatric fundus photography. For proof-of-concept validation, all off-the-shelf optical components were selected to construct a lab prototype pediatric camera (PedCam). By freeing the entire pupil for imaging purpose only, the trans-pars-planar illumination enables a 200° FOV PedCam, allowing easy visualization of both the central and peripheral retina up to the ora serrata. A low-cost, easy-to-use ultra-wide field PedCam provides a unique opportunity to foster affordable telemedicine in rural and underserved areas.

Fig. 1.

(A) Optical layout of the prototype PedCam. All off-the-shelf optical components were used for this prototype. (B) Photographic illustration of the prototype PedCam for fundus imaging. (C) Light spectrum, normalized intensity of the light source and ISO 15004-2: 2007 aphacic photochemical hazard weighting function. (D) Trans-pars-planar illuminator was used to create diffused and homogenized illumination inside the eye, the contact OL, consisting of a meniscus lens contacted to the cornea and a condensing lens, is used to produce an aerial retinal image at ∼3 mm from the last surface of the lens set. (E) The relay optics in Fig. 3(A), consisting of a bi-convex lens I, a planoconcave lens II and another bi-convex lens III, working with the camera lens together to relay the aerial retinal image to the camera sensor.

Fig. 2.

(A) Representative fundus images captured with the prototype PedCam from the left eye of a patient with zone III stage 2 ROP. (B) Schematic diagram of the eye showing the location of the pars plana, ora serrata, peripheral retina, and equator of the globe. (C) Schematic diagram of the left ocular fundus, illustrating retinal zones for ROP classification. (D) Representative fundus images captured with the prototype PedCam from the left eye of a patient with plus disease, zone II stage 2 ROP in the nasal region and zone II stage 3 ROP in the temporal region, with trans-pars-planar illumination light delivered from the temporal (D1) and nasal (D2) sides, respectively.

Fig. 3.

Fundus images of a patient previously diagnosed with retinoblastoma. (A) Central view of the fundus captured with the prototype PedCam2 in Fig. 1(A). Treated retinoblastoma lesion surrounded by photocoagulation scars was observed below the optic disc. (B) Vortex vessels, ora serrata and pars plana were observed by slightly tilting the axis of the imaging system for peripheral imaging. (C) Fundus image of the same eye captured by clinical Retcam. (D) Overlapping illustration of two images captured by the 200° prototype PedCam and 130° clinical Retcam.