A Low-Cost and Simple Imaging Technique of the Anterior and Posterior Segments: Eye Fundus, Ciliary Bodies, Iridocorneal Angle

PURPOSE. The authors recently used topical endoscopy to image the mouse eye fundus. Here, they widened the field of application for this ophthalmologic tool, imaging both the posterior and the anterior eye segments in larger animals commonly encountered in research laboratories and veterinary clinics. METHODS. Pupils were dilated, and local anesthetic and gel were applied to the animal cornea. The endoscopic probe was placed in contact with the cornea of conscious rats, sedated cats and dogs, anesthetized sheep, and nonhuman primates. RESULTS. High-resolution digital images of the eye fundus were obtained in all investigated animals using the endoscopic probe along the eye axis. Arteriovenous filling time was monitored with fluorescein angiography in pigmented rats. The retinal periphery and ciliary bodies could be visualized with the probe placed at an oblique angle. The probe was inclined further to observe the iridocorneal angle such that the pectinate ligaments could be seen at high resolution in cats. The authors used the probe on eyes with retinal detachment, luxation of a cataractous lens, and pigment infiltration in the iridocorneal angle, demonstrating its potential use in eye diseases. CONCLUSIONS. This topical endoscopic technique provides a unique tool for single eye examinations. The authors obtained a circular view of the anterior (iridocorneal angle) and the posterior (fundus) eye segments from all animal species studied. This technique is inexpensive and easy to use. It can be easily moved to the eye of the patient who cannot move to stand in front of classic apparatus, offering new opportunities in ophthalmology. (Invest Ophthalmol Vis Sci. 2008;49: 5168‐5174) DOI:10.1167/iovs.07-1340 I maging eye structures has become essential in diagnostic examinations and follow-up of retinal diseases or lesions in humans and animals. Imaging the eye fundus, for instance, detects retinal detachment, retinal atrophy, and blood vascular occlusion, and examination of the iridocorneal angle can reveal factors underlying an increase in intraocular pressure leading to glaucoma and ganglion cell degeneration. Eye examinations of the cornea, anterior chamber, lens and posterior chamber, and vitreous are usually carried out with a slit lamp apparatus. Images of the eye fundus can then be obtained using indirect ophthalmoscopy or confocal scanning laser ophthalmoscopy (cSLO). 1 These techniques not only provide reflection images of the retina, they generate fluorescent images from natural pigments (autofluorescence) or fluorescent dyes (e.g., fluorescein and indocyanine green) administered to the patient or animal. Such dye-induced images are particularly useful for assessing blood circulation and blood vessel permeability in the retina and the choroid. Anatomic sections of the in vivo retina can be obtained by optic coherence tomography (OCT), a technique recently associated with cSLO. 2 These techniques all use eye optics to visualize the fundus without any contact with the cornea. However, they do not enable the far retinal periphery to be visualized. OCT can provide images of the iridocorneal angle of the eye and ciliary bodies. 3,4 Ultrasound biomacroscopy (UBM) can also provide images of the iridocorneal angle and of the ciliary bodies in humans 5 and mice. 6 To visualize these eye structures for surgery, a goniolens must be used on the cornea to obtain overall circular visualization through indirect ophthalmoscopy. 7,8 However, this approach does not allow a particular area of interest to be targeted by the clinician. We recently described a new endoscopic technique to obtain eye fundus images in the mouse retina. 9 In this study, we extended this low-cost technique to use in larger mammals, including nonhuman primates. Furthermore, we used it to visualize other eye structures, including the iridocorneal angle, in a single examination by simply changing the angle of the endoscopic probe on the cornea.