A smartphone based method for mouse fundus imaging

Abstract

Noninvasive in vivo imaging of the mouse retina is essential for eye research. However, imaging the mouse fundus is challenging due to its small size and requires specialized equipment, maintenance, and training. These issues hinder the routine evaluation of the mouse retina. In this study, we developed a noncontact imaging system consisting of a smartphone, a 90D condensing lens, a homemade light diaphragm, a tripod, and a Bluetooth remote. With minimal training, examiners were able to capture fundus images from the mouse retina. We also found that fundus images captured using our system from wild type mice, mice with laser-induced retinal injury, and a mouse model of retinitis pigmentosa showed a quality similar to those captured using a commercial fundus camera. These images enabled us to identify normal structures and pathological changes in the mouse retina. Additionally, fluorescein angiography was possible with the smartphone system. We believe that the smartphone imaging system is low cost, simple, accessible, easy to operate, and suitable for the routine screening and examination of the mouse eye.

Keywords: Fluorescein angiography; Fundus imaging; Laser-induced retinal injury; Mouse retina; Retinitis pigmentosa; Smartphone.

Figure 1:

Materials and setup of the smartphone imaging system. (A) Individual components of the smartphone imaging system. 1: 90D condensing lens; 2: ¾ inch Sch40 PVC compression coupling rubber gasket; 3: 3.5 cm long ¾ inch PVC pipe with black spray paint inside and black electrical tape outside; 4: Bluetooth remote; 5: adjustable smartphone holder; 6: tripod. (B) and (C): assembly of the diaphragm using the 90D condensing lens (1), rubber gasket (2), and PVC pipe (3). The 90D condensing lens and PVC pipe were inserted into the rubber gasket with the lens flush with the front of the gasket and the PVC pipe seated directly behind the lens within the gasket. (D) Smartphone imaging system setup. The assembled diaphragm (1–3) was positioned between the mouse eye and smartphone mounted on the holder (5) and tripod (6) until the fundus image was shown on the smartphone screen. Fundus images were captured via the Bluetooth remote (4).

Figure 2:

A comparison of fundus images obtained using the smartphone and Micron IV imaging systems. Each pair of images were taken from the same mouse eye. For image comparison, the entire visible fundus area was cropped, stretched, and presented at the same image size for the two systems. (A) and (B): wild-type (WT) C57BL/6J mouse retina. (C) and (D): laser-induced retinal injury mouse retina (LRI). (E) and (F): retinitis pigmentosa (RP) model mouse retina. (G) and (H): fluorescein angiography (FA) of WT retina. Black arrows: glare/light reflection. White arrows: chromatic aberration. Black triangles: retinal vessel shadow. White triangles: attenuated retinal blood vessels. Asterisks: laser burns. Arrowheads: hemorrhage. The black lines in (C) and (D): diameters of the optic disc (d1 or D1) and diameters of the laser burn (d2 or D2), respectively. The numbers in (G) and (H): retinal blood vessels.