Examination of the canine retina with Optical Coherence Tomography

Background: In veterinary practice the currently in use retinal examination methods do not make it possible to detect fine changes, giving only informing result, what could be confirmed by pathologic methods. Those methods do not support the detection of eye related diseases and other systematics (metabolism disorders chronic inflammations, toxicosis), which early signs appear in the retina. Objectives: The authors present their own clinical examination results, which show how the iVue-100 Optical Coherence Tomography (OCT), the Opthalmic Ultra Sound (US) and the Tonovet can be used combined in the veterinary ophthalmology, including screening for retinal related diseases. Materials and Methods: The posterior segment of the eye, as a whole, was examined with opthalmic US instrument with 10-20 MHz Base scan head. The OCTs principle of operation is similar to the ultra sound systems, but instead of sound it applies a special laser light to scan, which let us examine the retinal layers in vivo, non-invasive with 5 mu m resolution in live animals. The Tonovet calculates the inner ocular pressure with a small probe pushing the cornea several times. In our clinical practice we performed the US, OCT and Tonovet examination of 345 dogs, between the age of 6 weeks and 15 years. Results and Discussion: During the study the authors found that the average corneal thickness is between 440 and 490 mu m with no vascularisation and pigmentation, the corneal angle is between 41.35 +/- 9.7 degree SD. Retinal thickness is 208 +/- 8 mu m SD, while the inner retina's is 63 +/- 4 mu m SD. In these healthy normal cases the intra ocular pressure was between 16-19mm of mercury. The US instrument can answer the question whenever the retina is elevated or not. Considering the normal changes by the age with the combined ways of examinations the OCT, US and Tonovet are suitable for screening and diagnose many eye related diseases in early stages even for preventive means.