January 07, 2019

Ophthalmic Examination in the Geriatric Cat

German investigators recently examined the effect of aging on feline vision and ocular anatomy.
 
By Natalie Stilwell, DVM, MS, PhD
According to a recent article in the Journal of Feline Medicine and Surgery, scant information is available regarding normal and abnormal ophthalmologic findings in the aging cat. In response, investigators examined the effect of increasing age on vision and ocular parameters.

Methods
Clinicians at the Free University of Berlin in Germany performed an ophthalmic examination as part of routine preventive healthcare screening in feline patients. For statistical purposes, patients were divided into 3 age categories: mature (9-10 years), senior (11-14 years), and geriatric (³15 years).

Patient examination included systolic blood pressure (SBP) measurement, a vision test, Schirmer tear test (STT), lens examination using slit lamp biomicroscopy, intraocular pressure (IOP) measurement using rebound tonometry, and examination of the vitreous, fundus, and optic disk.

The authors aimed to determine ocular parameters in apparently healthy aging cats. Thus, while cats with systemic disease were eligible for inclusion in the study, values from cats with apparent health conditions were excluded from statistical analyses. For example, STT values were excluded from cats with ocular discharge or changes to the conjunctiva or cornea, and SBP values were excluded from cats with hypertensive changes to the eye and those receiving antihypertensive medication.

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Results
A total of 122 male and 87 female cats ranging in age from 9 to 24 years were examined. Most were domestic shorthair cats and lived strictly indoors.

One-quarter of cats had impaired vision, usually due either to glaucoma or to retinal edema, hemorrhage, and/or detachment. Frequently noted findings on ophthalmic examination included lenticular sclerosis (81% of cats), iris and ciliary body atrophy (23%), and iris pigment changes (18%). Increasing age was significantly associated with several changes to the iris, lens, and fundus. In particular, frequency of bilateral enophthalmos, lenticular sclerosis, attenuated retinal vessels, hypertensive retinopathy, and combined iris atrophy with iris pigment changes increased with age.

The authors determined the following mean (+/- range) values for apparently healthy, aging cats:
  • SBP: 153.9 (+/- 29.9) mm Hg
  • IOP: 16.5 (+/- 5.0) mm Hg, with a mean difference of 2.8 mm Hg between the left and right eye
  • STT: 15.8 (+/- 4.8) mm/min

Older cats with relatively high SBP values were more likely compared with other cats to develop retinal abnormalities. Mean SBP in cats with retinal edema and/or hemorrhage was 181.3 (+/- 43.6) mm Hg, while those with retinal detachment had an even higher mean SBP of 215.9 (+/- 49.1) mm Hg. However, SBP and IOP were similar among cats regardless of age category, as were incidences of vision impairment, uveitis, and glaucoma. Contrasting with studies performed in humans and dogs, STT values increased rather than decreased with age in the examined cats, suggesting that reduced tear production is not an issue in geriatric cats.

Conclusions
This study identified a high frequency of age-related ocular changes, many of which may serve as indicators of systemic conditions (such as hypertension) in the aging feline patient.
 

Dr. Stilwell provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting. In addition to her DVM obtained from Auburn University, she holds a MS in fisheries and aquatic sciences and a PhD in veterinary medical sciences from the University of Florida.

 

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