Evidence points to routine retinal screening benefit for older cats

Routine fundic examination of geriatric cats (those older than 8 years of age) can help identify ocular lesions associated with hypertension before they produce clinical signs, according to a study in the New Zealand Veterinary Journal. These screenings may be valuable with or without an elevated blood pressure reading, as accurate blood pressure measurements can be difficult to obtain in cats.

The study, performed at Massey University in Auckland, examined cats older than 8 for the presence of hypertensive ocular lesions in order to identify the usefulness of routine fundic examination in older cats with or without existing vision impairment.

Just over 100 client-owned cats were enrolled in the study. To increase the researchers’ chances of obtaining accurate blood pressure readings, each cat was given time to acclimate to the clinic environment before five blood pressure measurements were taken using high-definition oscillometry. All cats received a complete physical examination and blood and urine sample screening for evidence of chronic kidney disease, hyperthyroidism and diabetes mellitus. Cats were categorized as having any of these concurrent diseases only if clinical signs corroborated the laboratory data.

Only cats for which consistent blood pressure measurements could be obtained were included. Of the 73 cats meeting the criteria, 12 (16 percent) had hypertensive ocular lesions identified on fundic examination. Ten of these cats were also hypertensive. Ocular lesions associated with systemic hypertension include retinopathies, choroidopathies and optic neuropathies.

However, only three of the cats with hypertensive ocular lesions included in the analysis showed clinical signs of visual disturbance, and these had more severe lesions (vitreal haemorrhages and retinal degeneration) than the nine without clinical signs. Chronic kidney disease was the most common underlying condition identified, with six of the 12 cats exhibiting signs and diagnostic results. The cats with hypertensive ocular lesions were treated with amlodipine besylate and all showed improved fundic morphology on followup examinations.

“Ocular fundic examination of cats over 8 years of age allows identification of cats with hypertensive ocular lesions, often before the owner or veterinarian is aware the cat has a problem with its vision. This may result in diagnosis of systemic hypertension, allowing early treatment and resolutions of lesions,” the published report states. “Ocular lesions resulting from hypertension occur frequently enough in cats ... to support the recommendation for fundic examination in cats over 8 years of age as part of the routine physical examination.”

The retinal fundus camera used in the study was the ClearView Optical Imaging System, which is produced by Optibrand and distributed in the United States by Dan Scott and Associates.