What is normal IOP in cats and how do we measure it?Īs elevations in IOP contribute to the progression of glaucoma, an accurate and reliable means of measuring IOP is crucial to effective diagnosis and monitoring of this disease. ( 5- 6) In such cases, a diagnosis of glaucoma relies on the identification of characteristic posterior segment changes, supported by other secondary abnormalities, as described later in this review. Furthermore, in advanced glaucoma, degeneration of the ciliary body may limit aqueous production, ultimately lowering IOP. ( 4) It is clear that a single measurement of IOP obtained during an office visit may not accurately reflect the cumulative IOP to which the eye has been exposed. The magnitude of circadian fluctuation in IOP observed in glaucomatous cats in one recent study that utilized a Tono-pen XL, ( 3) was 2 to 8 times that reported for normal cats, which demonstrated circadian fluctuations in IOP in the order of 4 mmHg. In glaucomatous cats, as in other species including glaucomatous dogs and humans, ( 1- 2) IOP may fluctuate considerably, both within and between days. Conversely, a diagnosis of glaucoma cannot be excluded based on a single low or normal IOP reading. Both ocular hypertension and glaucoma should be distinguished from falsely increased IOP measurements due to improper tonometric technique, inappropriate restraint, patient stress and corneal factors that may render the tonometer inaccurate. Elevated IOP in the absence of clinical evidence of glaucomatous optic nerve and retinal damage is termed “ocular hypertension”, to distinguish it from overt glaucoma. However, caution should be exercised in diagnosing glaucoma based solely on a single, elevated IOP reading. The single most important risk factor for the development of glaucoma in humans and animals is intraocular pressure (IOP).

Glaucoma is therefore widely considered a neuro-degenerative disease.

In all species, this group of disorders is unified in their final common pathway of characteristic optic nerve and retinal pathology resulting in loss of vision. Rather, “the glaucomas” should be considered to represent a large, diverse group of disorders.

Relax and take notes cat