Spectral domain optical coherence tomography evaluation of the feline optic nerve and peripapillary retina

To describe and to establish normative data for the feline optic nerve and peripapillary retina using SD-OCT (Spectralis^® HRA+OCT2).

Slit-lamp biomicroscopy and rebound tonometry were performed in seven male-intact (0.65 ± 0.02 years;4.34 ± 0.33 kg) and seven female-spayed (0.74 ± 0.03 years; 3.13 ± 0.28 kg) cats. All eyes were pharmacologically dilated with 1% tropicamide prior to indirect ophthalmoscopy examination. Animals were then placed under general anesthesia. Optic nerve and peripapillary retinal morphology was evaluated using SD-OCT device by infrared imaging and volumetric scans (circle and radial). Optic disc area, optic cup depth, peripapillary retinal thickness (RT), and retinal nerve fiber layer thickness (RNFLT) were measured. The RNFLT:RT ratio was calculated in the superior, nasal, temporal, and inferior peripapillary region.

Intraocular pressure in all cats was 20.68 ± 4.87 mm Hg (mean ± SD). Mean RT and RNFL were thickest in the superior retina (264.7 ± 13.95 µm and 70.22 ± 11.78 µm, respectively) (P < 0.0001). Inferior RT was significantly thinner than nasal and temporal retina (P = 0.0013 and P = 0.0010, respectively). The RNFLT:RT was significantly higher in the superior retina (0.27 ± 0.04) (P < 0.0001). Optic disc area OU was 1.39 ± 0.26 mm² . Optic cup depth OU was 168.36 ± 67.74 µm. All parameters tested were not affected by gender, intraocular pressure, body weight, or tested eye. Most eyes had a Bergmeister papilla that was only visible on OCT. Some animals had a recessed area over the center of the ONH meniscus.

Normative peripapillary ONH OCT data have been introduced. A Bergmeister papillae is commonly seen in young cats on OCT examination. OCT is a helpful tool to evaluate the retina in cats.