Eye issues

Dilated pupils (also referred to as mydriasis) describes when the hole in the middle of the iris of the eye is very large. Pupils normally change size in reaction to light changes or a particular emotional state such as anxiety or excitement. 

The pupil is the dark circle located at the center of the iris (the colored portion) of dogs’ eyes. The size of dogs’ pupils varies depending on light levels. When one or both eyes dilate (when the pupil becomes larger), this is called mydriasis.

The pupil is the opening in the center of the eye. Dilated pupils in cats occur normally in response to decreased light levels and some physiologic conditions, such as during the natural fear response.

Keratoconjunctivitis sicca (KCS) refers to an eye condition in dogs commonly referred to as “dry eye.” KCS causes decreased watery tear production, which leads to inflammation of the eye and surrounding tissues.

Blindness in cats can appear varies in severity and can include partial or full blindness. Cats are especially good at learning their environment and adapting to vision loss, so detection of vision loss can be difficult.

Blindness refers to loss of vision, either due to a problem within the eye itself, or within the nerves or brain affecting the processing of visual input from the eyes. Vision loss can affect one eye or both, and be partial or complete.

The retina is located at the back of the eye, and sends visual input to the brain via nerve impulses, creating the sensation of sight. If the retina detaches from the structures underneath it, it loses function, resulting in partial or complete vision loss.

The retina is at the back of the eye and converts light and nerve impulses into vision. The retina can become detached from its underlying tissue causing partial or complete blindness in cats. 

Equine Recurrent Uveitis (ERU), or moon blindness, is an uncommon condition affecting horses, characterized by inflammation within the eye that occurs repeatedly. ERU cycles through periods where it is active, aggressive, and painful, as well as mild phases which often show no symptoms.

Crossed eyes (strabismus) is a common symptom in cats where one or both eyes have abnormal, persistent positioning. Strabismus can be congenital and is most often seen in Siamese, Himalayan, and flame point Persian breeds.

Strabismus describes an uncommon disorder in dogs in which one or both eyes are not correctly aligned, giving the appearance of crossed eyes or eyes not pointing in the same direction together. 

Blepharospasm is a term that describes repeated, spasmodic movement of the eyelids, commonly referred to as squinting. Blepharospasm is a broad symptom that is seen as a feature of different underlying diseases in cats, including injury, infection, inflammation, and developmental abnormalities.

Squinting (blepharospasm) occurs when the eyelids are lowered so that there is only a small space for the eye to look out of. Squinting is considered a symptom in dogs if it continues for a prolonged period and is not related to protecting the eyes from bright light.

Cloudy eye, also called corneal edema, describes an opacification of the eye which makes the outer surface of the eyeball appear gray, white, or blueish instead of clear.

Tumors of the eye, defined as abnormal cell growth in or around the eyes, are uncommon in cats. Most eye tumors are malignant, aggressive, fast-growing, and likely to spread throughout the body where they have serious consequences.

Anisocoria is the term for unequal pupil size in dogs. One pupil is normal, while the other is either constricted or dilated. Anisocoria is common in dogs experiencing Horner’s syndrome, but it also results from a variety of conditions and injuries that either affect one eye directly or the parts of the nervous system that control pupil size.

Blepharitis describes inflammation of the eyelids affecting one or both eyes. Eyelid inflammation is a common presentation in dogs with a variety of underlying triggers.

Progressive retinal atrophy (PRA) is a disorder of the retina which eventually results in blindness in dogs. The retina is a layer of tissue at the back of the eye which translates signals from the eye into images in the brain.

A tumor is a proliferation of cells resulting in uncontrolled tissue growth. Primary eye tumors originate from within the eye, and secondary tumors spread to the eye from somewhere else in the body. Retroviruses, UV exposure, and genetics can predispose a dog to eye tumors.

Coloboma describes the presence of an abnormal hole, or thinning, in part of the eye. Colobomas are rare in dogs but, where present, are most commonly found in the iris and eyelid margin.

Blepharitis is inflammation of the upper or lower eyelid. This condition can affect one or both eyes, and the experience is uncomfortable. Blepharitis is common in cats and is caused by a variety of underlying conditions including infections, birth defects, allergies, immune conditions, environmental irritants, and cancers.

Eye discharge or epiphora is a common symptom in dogs. Causes, as well as treatment of eye discharge, vary greatly. Eye discharge can present in various ways including clear water (tears), crust-like formation on the inner corner of the eye, reddish discharge, white mucus, and yellow discharge.

Nystagmus is involuntary, erratic movement of the eyes. Nystagmus is a very rare symptom in horses, but when present indicates a brain injury or disorder and requires urgent medical attention.

A coloboma, sometimes called a “hole in the eye,” is a congenital condition where tissues in one or more structures of the eye fail to form properly. Eyelid colobomas involve a portion of the eyelid being absent, impacting function.

The uvea describes the internal structures of the eyeball. Uveitis is inflammation of the uvea, and has a number of underlying causes. Urgent care is required for any cat that develops symptoms of uveitis, as the condition is often painful and can result in vision loss.

The cornea is the transparent cover over the front of the eye. When inflamed, it swells with fluid (edema), and becomes cloudy. Corneal edema may appear as a hazy, blue, or milky opacity covering the surface of the colored part of the eye.

Lens prolapse, or luxation, is when the lens of the eye becomes dislocated from its proper position. A dislocated lens can move into the front (anterior) or the rear (posterior) of the eye, and may be primary (inherited) or secondary (occurring due to another condition).

Dacryocystitis is inflammation of the tear sac. The tear sac is part of the system which allows the draining of tears inside the nasal passages. When tear drainage is obstructed, tears overflow from the eye and conjunctivitis develops. 

Dogs have a third eyelid, visible as a pink membrane mostly hidden under the inside corner of the eye. When the bulbous, dark pink gland of the third eyelid slips out of place and becomes visible, this is called a “cherry eye.” 

Keratoconjunctivitis sicca (KCS) is commonly called ‘dry eye’ because it’s caused by a lack of water in the tears. Without watery tears, the surface of the eye dries out and irritants cannot be flushed away.