Anim. Eye Res. Brief Note Application of Optical Coherence Tomography (OCT) for Ophthalmologic Examination in Cynomolgus Monkeys Tomoaki ARAKI, Arisa HIGASHI, Koji KABAYAMA, Takayuki ICHI, Haruna NAGAE and Yojiro OOSHIMA Drug Safety Research Laboratories, Shin Nippon Biomedical Laboratories, Ltd. 2438 Miyanoura, Kagoshima 891-1394, Japan Tel: 099-294-2600 Summary Optical coherence tomography (OCT) is an analytical technique which enables non-invasive cross sectional imaging of the ocular fundus by computing wave intensity and positional information from the interference of the light reflected from bordering regions of different tissue density with that from the original light source when the fundal region is exposed to low-coherence near infra-red light 1). The cynomolgus monkey is widely used for safety evaluation in drug development and, with its macula lutea resembling those of humans, there are abundant background data on the evaluation of ophthalmic toxicity in this species. When ocular fundal abnormalities are to be investigated, examinations can be made with an aspheric lens and indirect ophthalmoscope. However, a considerable degree of proficiency is necessary to gain an understanding of the threedimensional positional relationship for all tissue layers of the ocular fundus. Furthermore, it is difficult specify to the locations of small abnormalities. We investigated the application of OCT by taking tomographic images of the ocular fundi of cynomolgus monkeys with macular and peripheral macular degeneration for a comparison with normal cynomolgus monkey. In addition, we report on a comparison of OCT and electroretinography (ERG) in the cynomolgus monkey. Received: November 30, 2011 Accepted: December 11, 2011 Keywords: Optical Coherence Tomography OCT, cynomolgus monkey
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Fig. 1. OCT image of the right fundus in a normal monkey. NFL: Nerve fiber layer, GCL: Ganglion cell layer, IPL: Inner plexiform layer, INL: Inner nuclear layer, OPL: Outer plexiform layer, ONL: Outer nuclear layer, ELM: External limiting membrane, IS: Photoreceptor inner segment, IS/OS line: Photoreceptor inner and outer segments line, OS: Photoreceptor outer segment, VM: Verhoeff membrane, RPE: Retinal pigment epithelial layer, CL: Choroid layer. The green line represents the cutting plane. Fig. 2. Ocular fundus photograph and OCT image of the left fundus in an abnormal case (case A). Macular hole (arrow), and thinning of entire retinal layer. The green line represents the cutting plane. Fig. 3. Ocular fundus photograph and OCT image of the left fundus in an abnormal case (case B). Detachment of nerve fiber layer (arrow). Partial loss (arrow head) and degeneration between the nerve fiber layer and retinal pigment epithelial layer. The green line represents the cutting plane. 25
Fig. 4. ERG waveforms. (a) Maximal combined response. (b) Cone response. : Normal monkey. : Case A. : Case B. Fig. 5. Ocular fundus photograph and OCT image of the left fundus in an abnormal case (case C). Cystic degeneration of the nerve fiber layer (arrow). The green line represents the cutting plane. Fig. 6. Ocular fundus photograph and OCT image of the left fundus in an abnormal case (case D). Cystic degeneration of the ganglion cell layer (arrow). The green line represents the cutting plane. 26
Fig. 7. Ocular fundus photograph and OCT image of the right fundus in an abnormal case (case E). Choroidal neovascularization (arrows). The green line represents the cutting plane. Fig. 8. Ocular fundus photograph and OCT image of the right fundus in an abnormal case (case F). Partial breakage and degeneration between the inner plexiform layer and retinal pigment epithelial layer (arrows). The green line represents the cutting plane. 27