When our pets have an eye problem, we worry about two main outcomes: pain and vision loss. Pain speaks for itself; we don't want our pets in pain. As our pets' guardians, we need to help them when they are in pain, and need to help them protect their precious eyesight which means watching closely for signs of ocular discomfort and getting them veterinary care right away. The sooner an eye problem is diagnosed and treated, the quicker pain relief can occur and the better chance to save your pet's eyesight.
The main sign to look for in your pet is fortunately pretty obvious: excessive squinting/blinking (termed blepharospasm). Other signs such as redness and excessive tearing often accompany the blepharospasm. Sometimes the blepharospasm can be subtle, so it is important to pay close attention. Your pet may paw at the affected eye(s) indicating discomfort, or rub their face/eye(s) on the floor/furniture. Sometimes the self trauma can lead to even worse consequences than the initial eye problem itself. If you notice your pet trying to rub at a painful eye, stop them and seek veterinary care. If you have an Elizabethan collar (E-collar) at home, place it on your pet in the meantime.
There are many conditions that can lead to painful eyes, and the amount of pain varies from pet to pet and condition to condition. But a painful eye is a painful eye, and none should be ignored. Many of the conditions that cause painful eyes can ultimately lead to vision loss if left ignored (and sometimes even despite medical intervention
Conjunctivitis has many causes and simply means inflammation of the conjunctiva (the tissue of the whites of the eyes and the inner eyelids), manifesting mostly as 'redness' of the eye with varying degrees of discomfort. Quite common in our pets, it is usually a mild condition caused by allergies/irritants, viral/bacterial infections or trauma/foreign bodies and can usually be readily treated/controlled. In some cases, it can be severe and quite painful but usually does not lead to vision loss.
Corneal Ulcer/Erosion is a defect in the outer clear layer of the eye and is usually quite painful. This defect is either in the form of a scratch, a puncture or a wide area of the cornea that is missing tissue. You may notice a haziness to the eye or actually see an indent. The defect can be very superficial, just barely scratching the surface, or can be very deep to the point of penetrating the eye globe itself. Usually caused by trauma (dogs/cats running into bushes, foxtail grass awns caught in the eyelids, fights with cats), viruses (cats with herpes) or other eye disorders (eyelid issues, dry eye), corneal ulcers/erosion can usually be treated but in some cases a vision-impairing scar can remain long after healing. Sometimes, a deep, infected or non-healing ulcers not responding to medical therapy may require some form of surgery.
Anterior Uveitis had many causes and simply means inflammation of the anterior uvea (the tissue of the iris–the colored internal eye tissue controlling the pupil size), manifesting as a painful eye that may be red, cloudy, bloody, or swollen (if a secondary glaucoma occurs). The inflammation can be caused by eye conditions (trauma, lens luxation) or from systemic, whole body disorders (infections, cancers, immune-mediated diseases). Sometimes the uveitis is mild but the underlying disorder is very serious; other times the uveitis is severe but caused by a minor trauma that will be easily resolved. Depending on the cause, the uveitis (and/or the underlying condition) may or may not be treatable/curable and in some cases can lead to vision loss.
Keratoconjunctivitis Sicca (KCS) is a disorder known as dry eye, usually caused by an immune mediated destruction of the glands that produce the water portion of tears. Without it, the eyes (conjunctiva and cornea) become dry, red, painful and goopy. Usually quite obvious (the eyes look bad!), this disorder requires constant, lifelong treatment that, without, leads to ulcerations/erosion and ultimately to scarring and darkening of the corneas that lead to variable vision loss, in severe cases, total blindness.
Glaucoma is a condition is which there is an increase in the fluid pressure within the eye (intraocular pressure–IOP), which is very painful and if too high and left untreated for one to three days can lead to blindness. It can sometimes be a primary disorder (something wrong with your pets' genetics/anatomy) more common in certain breeds, while other times, it’s secondary to other internal eye problems like anterior uveitis or a lens luxation. It can occur very suddenly and is often an emergency condition. In most cases, medication is not enough and some form of surgery is needed to keep the pressures normal,for pain relief and to save vision. If vision is already lost, and pain cannot be controlled, removing the eye is often indicated.