Systemic hypertension (high blood pressure) is a common problem in companion animals, particularly in cats. Frequently, there are no obvious systemic signs indicating your pet has high blood pressure. The first sign observed may be the sudden onset of blindness. The retina lines the back of the eye and functions similarly to film inside a camera. Long-standing elevations in blood pressure lead to damage of the blood vessels throughout the body and this occurs in the retina of the eye as well. These damaged blood vessels leak ﬂuid, which accumulates under the retina and causes it to detach, resulting in blindness. Some owners will notice that their pet’s pupil is very large, that one pupil is a different size than in the other eye, or that the green “eye shine” is more obvious. Other signs may be bleeding within the eye or neurologic changes.
Normal blood pressure in cats and dogs is similar to humans and should be around 120 mmHg. However, due to the effects of stress on our patients in the hospital, even normal animals can have blood pressure readings significantly higher than the normal range. Your doctor will take into consideration many factors in determining a treatment plan for your pet. It is important that your pet has their blood pressure monitored in a quiet setting and in a consistent manner with as little distress as possible for accurate measurements. If your pet is placed on medications it is imperative that these medications be consistently administered as directed by your veterinarian and never be stopped abruptly. If medications are stopped, signs will likely return.
Most cats and dogs affected with high blood pressure have developed this condition as a result of another underlying health problem such as kidney disease, heart disease or an endocrine disease (Hyperthyroidism, Cushing’s disease, Diabetes Mellitus, or others). To manage high blood pressure appropriately, it is important to identify and treat any underlying diseases. Thus, a full health history, current blood work, and urine analysis are extremely helpful when dealing with this syndrome. Early diagnosis and treatment will improve overall health and decrease the risk of ongoing retinal damage and systemic side effects. Systemic hypertension is not only blinding, if severe damage to the other organs occurs, it can be a life-threatening disease as well.
Depending on the degree of retinal detachment, the amount of bleeding and the duration of retinal disease, your pet may regain vision with treatment. Regular eye examinations and blood pressure monitoring will be required long-term. Your veterinary ophthalmologist and your primary veterinarian will work together to determine the best treatment and monitoring plan for your pet.