Retinal Degeneration in Dogs

 

The retina is the tissue that lines the inner surface of the eye, and is the light sensitive part of the eye that acts as the brain’s camera, transmitting images through the rods and cones that are part of its structure, thus enabling the experience of vision. The retina is part of the central nervous system (CNS) and the only part of the CNS that can be easily imaged and examined. In retinal degeneration, the cells of the retina begin to decline in function, thereby leading to impaired vision or even blindness. There are many causes for retinal degeneration.

 

Symptoms and Types

 

• Night blindness that progresses to blindness in light as well
• Dilated pupils
• Inability to see clearly in bright light
• In some conditions, only central vision may be lost, the animal may still retain peripheral vision
• The pupil (opening of the eye) has abnormal reactions to light
• The retinal structure appears abnormal when a doctor examines it with an ophthalmoscope; cataract may be observed
• The liver may also be affected, obesity may be observed
• Sudden blindness may be due to sudden acquired retinal degeneration syndrome (SARDS)

 

Dogs

 

• Progressive retinal atrophy (PRA) is a group of disease that worsens over time, and is seen especially in collies, Irish setters, miniature poodles, cocker spaniels, Briards and Labrador retrievers, mastiffs, X-linked in Samoyeds and Siberian huskies
• Central progressive retinal atrophy (eye disease that leads to loss of central vision, but retention of peripheral vision possibly for years) may be seen in Labrador retrievers
• Neuronal ceroid lipofuscinosis (a nervous system disorders with swelling and/or changes in some retinal cells) occurs in most breeds
• Inability to see clearly in bright light (known as hemeralopia) may occur in Alaskan malamutes
• Sudden blindness due to sudden acquired retinal degeneration or SARD is more common in middle-aged and older dogs; 70 percent are female

 

Mean Age and Range

 

• Early progressive retinal atrophy may occur three to four months of age up to two years of age
• Clinical signs of late progressive retinal atrophy are seen dogs older than four to six years of age

 

Causes

 

• Genetic
  • Hereditary degeneration is common
  • This is characterized by the formation and development of a faulty group of cells, which gradually worsen in function over life
• Degenerative
  • Long-term glaucoma, scarring inflammation or separation of the retina due to trauma
• Abnormal structure
  • Abnormal structure at birth or abnormal development of the retina with age
• Metabolic
  • Insufficient or excess amounts of certain enzymes
• Cancer
  • Cancer from other parts of the body that has spread to the retina
• Nutritional
  • Deficiency of Vitamin A or E
• Infectious/Immune
  • Infections of the retina or infections that spread from other parts of the body
• Idiopathic (Unknown Cause)
  • Sudden blindness due to sudden acquired retinal degeneration syndrome (SARDS)
• Toxic
  • Adverse Reactions to specific drugs

 

Diagnosis

 

You will need to give a thorough history of your dog’s health, onset of symptoms, and possible incidents that might have led to this condition, such as trauma or exposure to toxic substances. Your dog’s diet will also be taken into consideration, since this may be a supporting cause.

 

Your veterinarian will perform a complete physical exam on your dog, taking into consideration your dog’s lineage and whether there might be a genetic link. Standard laboratory tests include a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis, in order to rule out other causes of disease.

 

 

The physical exam will entail a full ophthalmic exam using a slit lamp microscope. During this exam, the retina at the back of the eye will be closely observed for abnormalities and the electrical activity of the retina will also be measured.

 

Genetic testing may also be done if your dog belongs to a breed that is prone to familial retinal disease. Additionally, hormonal causes may bring about retinal disease, and this will be considered as well. X-rays, computed tomography (CT) and magnetic resonance imaging (MRI) can be used effectively to screen for the effects of hormonal abnormalities.

 

Retinal Hemorrhage in Dogs

 

The retina is the innermost lining of the eye, laying just beneath the middle choroid coat, which in turn lies between the retina and the sclera – the white lining of the outer eye. The choroid coat contains connective tissue and blood vessels, which deliver nutrients and oxygen to the outer layers of the retina. In some cases the retina may separate from this layer. This is termed retinal detachment. Retinal hemorrhage is a condition in which the innermost lining of the eye has a local or generalized area of bleeding into that lining. The causes of retinal hemorrhage are usually genetic and breed specific.

 

Symptoms and Types

 

• Vision loss / blindness, demonstrated by bumping into objects
• Bleeding in other body parts – small bruises throughout the body
• Blood in urine, feces
• Whitish-appearing pupil
• Pupil may not contract when bright light is shone in the eyes
• Sometimes, no signs may be observed

 

Causes

 

Genetic (present at birth):

• Faulty development of the retina or the lubricating fluids of the eyes (vitreous humor)
• Some breeds are more at risk than others: Shetland Sheep Dogs, Collies, Labrador Retrievers, Australian Shepherds, Sealyham Terriers, Bedlington Terriers, English Springer Spaniels and Miniature Schnauzers

Acquired (condition that develops sometime later in life/after birth):

 

Diagnosis

 

Your veterinarian will perform a complete physical exam on your dog. You will need to give your veterinarian a thorough history of your dog’s health, onset of symptoms, and possible incidents that might have led to this condition. Standard laboratory tests include a blood chemical profile, a complete blood count, an electrolyte panel, a blood pressure test and a urinalysis, so as to rule out other causes of disease.

 

 

The physical exam will entail a full ophthalmic exam using a slit lamp microscope. During this exam, the retina at the back of the eye will be closely observed for abnormalities. The electrical activity of the retina will also be measured. An ultrasound of the eye may also be done if the retina cannot be visualized due to hemorrhaging. Samples of vitreous humor (eye fluid) may be taken for laboratory analysis. Genetic testing may also be done if your dog belongs to a breed that is prone to familial retinal disease.

 

Trichiasis, Distichiasis, and Ectopic Cilia in Dogs

  

Trichiasis, distichiasis, and ectopic cilia are eyelash disorders that are found in dogs. Trichiasis is in-growth of the eyelashes; distichiasis is an eyelash that grows from an abnormal spot on the eyelid; and ectopic cilia are single or multiple hairs that grow through the inside of the eyelid. In all of these conditions, the eyelash hair can come into contact with and damage the cornea or conjunctiva of the eye.

 

These conditions are commonly seen in young dogs but dogs of any age or breed may be affected. However, trichiasis does tend to appear more frequently in Pekingese, English cocker spaniel, pugs, and bulldogs; distichiasis is common in cocker spaniels, miniature long haired dachshunds, English bulldogs, golden retrievers, toy and miniature poodles, Shetland sheepdogs and Pekingese; and ectopic cilia are more commonly found in dachshunds, lhasa apsos, shih tzus, boxers, golden retrievers, and Shetland sheepdogs.

 

Symptoms and Types 

 

Trichiasis

• Change in pigmentation of the iris (colored portion of the eye)
• Abnormal ticking or twitching of the eyelid (blepharospasm)
• Overflow of tears (epiphora)
• Swelling of eyes

 

Distichiasis

• Mostly no symptoms can be seen
• Stiff cilia (eyelash)
• Pawing at eye
• Abnormal tick or twitch of eyelid (blepharospasm)
• Overflow of tears (epiphora)
• Increased blood vessels in the cornea
• Change in iris pigmentation
• Corneal ulcers

 

Ectopic cilia

• Eye pain
• Severe abnormal ticking or twitching of the eyelid (blepharospasm)
• Overflow of tears (epiphora)

 

Causes

 

• Facial conformation and breed predisposition
• Unknown etiology in many cats

 

 

 

Diagnosis

 

Your veterinarian will carefully inspect the eye structures and eyelashes to discern exactly which eyelash disorder your dog has. The diagnosis is usually straightforward in most cases. Your veterinarian will perform a Schirmer tear test to measure tear production and evaluate whether the affected eye is producing enough tears to keep it moist, and a fluorescein stain over the surface of the eye to make corneal ulcers visible. Determination of intraocular (within the eye) pressure is also an important test in evaluating the eye. This test will allow your veterinarian to evaluate the level of fluid pressure inside the eye. More specific testing may be performed to evaluate both the superficial and deep structures of eye.

  

 

Disease of the Optic Nerve in Dogs

 

Glaucoma is a condition in which pressure is placed on the eye, causing inadequate fluid drainage in the eye. If the condition becomes chronic or persists without treatment, it will eventually cause permanent damage to the optic nerve, resulting in blindness.

 

Glaucoma is common in certain dog breeds that are genetically predisposed, such as samoyeds, cocker Spaniels, poodles, chow chows, and Siberians. Unfortunately, 40 percent of dogs affected by glaucoma will become blind in the affected eye within the first year, regardless of medical or surgical treatment.

 

Symptoms and Types

 

There are two main types of glaucoma: primary and secondary. Symptoms for sudden primary disease, due to the eye’s inability to drain through the filtration angles of the eye, are as follows:

 

• High pressure within the eye
• Blinking of the eye
• The eyeball may recede back into the head
• Redness of the blood vessels in the whites of eyes
• Cloudy appearance at front of the eye
• Dilated pupil – or pupil does not respond to light
• Vision loss

 

Long-term, advanced disease:

 

• Enlargement of the eyeball (buphthalmos)
• Obvious loss of vision
• Advanced degeneration within the eye

 

Symptoms for secondary glaucoma, or glaucoma due to secondary eye infection(s), include:

 

• High pressure within the eye
• Redness of the blood vessels in the whites of eyes
• Cloudy appearance at front of the eye
• Inflammatory debris visible in the front of the eye
• Possible constriction of the pupil
• Possible sticking of the iris to either the cornea or the lens
• Possible that the edge of the iris circularly sticks to the lens

 

In addition, there may be:

 

• Headaches, with head pressing to relieve feelings of pressure in head
• Loss of appetite
• Change in attitude, less desire to play or interact

 

Causes

 

High pressure in the eye occurs when the normal outflow of fluid in the eye is impaired due to a primary eye disease such as the improper development of the eye’s filtration angles, or secondary to other eye diseases such as primary lens luxation (slipping of the lens in the eye), inflammation of the tissues of the eye, eye tumor(s), or blood collection in the front of the eye from injury. In dogs, secondary glaucoma is more common than primary glaucoma.

 

Diagnosis

 

You will need to give a thorough history of your dog’s health, onset of symptoms, as far as you have been able to tell, and possible incidents that might have preceded this condition, such as injuries to the eye (even those which you consider minor). During the physical examination, your veterinarian will test the pressure within your dog’s  eyes using a tonometer on the surface of the eye. If the disease began suddenly, your veterinarian will refer your dog to a veterinary ophthalmologist for a detailed examination of both eyes, including evaluation of the filtration angles by gonioscopy — measuring the anterior of the eye. Pressure within the eye can measure as high as 45 to 65 mmHg, making this a very painful condition.

 

Electroretinography will be also performed by the veterinary ophthalmologist to determine if the eye will remain blind despite treatment. In secondary diseases, X-rays and an ultrasound may show abnormalities within the eye.

 

Often both eyes are affected, but not always. In cases where only one eye is affected, steps will be taken to protect the unaffected eye from developing a diseased condition.

 

 

Cloudiness of the Eye Lens in Dogs

 

Cataract refers to the cloudiness in the crystalline lens of the eye, varying from complete to partial opacity. When the eye lens (located directly behind the iris) is clouded, it prevents light from passing to the retina, which can cause vision loss.

 

Most cases of cataracts are inherited. For instance, Miniature poodles, American cocker spaniel, miniature schnauzer, golden retrievers, Boston terriers, and Siberian huskies are all predisposed to cataracts.

 

Symptoms and Types

 

Symptoms typically relate to the degree of vision impairment. Dogs with less than 30 percent lens opacity, for example, display little or no symptoms, whereas those with more than 60 percent opacity of the lens may suffer from loss of vision or have difficulty seeing in dimly lit areas.

 

Meanwhile, if your dog has diabetes mellitus-related cataract, you may also observe increased thirst, increased frequency of urination, and weight loss in your dog, along with vision impairment symptoms.

 

Causes

 

Although most cases of cataracts are inherited, the following are other causes and risk factors associated with the condition:

 

• Diabetes mellitus
• Old age
• Electric shock
• Inflammation of the eye’s uvea (uveitis)
• Abnormally low levels of calcium in blood (hypocalcemia)
• Exposure to radiation or toxic substances (e.g., dinitrophenol, naphthalene)

 

Diagnosis

 

If you should observe cloudiness in one or both of the dog’s eyes, you should bring it in to see a veterinarian immediately. There, the veterinarian will ask for a thorough history of your dog’s health, including the onset and nature of the symptoms, and possible incidents that might have precipitated the problem. He or she will then perform a complete physical examination, focusing on the eyes and ocular region, to determine the severity of the problem.

 

Routine diagnostic tests, such as complete blood count, biochemistry profile, and urinalysis, may be conducted. However, the results of these tests are usually non-specific unless another concurrent disease like diabetes mellitus or hypocalcemia are at the root of the problem. Ultrasounds or electroretinography (which measures the electrical responses of cells present in the retina) are two forms of advanced diagnostic exams which also help determine the severity of the issue and may confirm whether surgery is necessary to correct a cataract.

 

 

Congenital Ocular Anomalies in Dogs

 

Congenital abnormalities of the eyeball or its surrounding tissue are generally evident shortly after a puppy’s birth, but may develop within the first six to eights weeks of life. Most defects are genetically inherited; for example, persistent pupillary membrane (PPM), which occurs when strands of fetal tissue remain on the eye after birth, is more prone in Basenjis, Pembroke and Cardigan Welsh Corgis, chow chows, and mastiffs.

 

Meanwhile, persistent hyperplastic tunica vasculosa lentis (PHTVL) and persistent hyperplastic primary vitreous (PHPV) is most frequently inherited in Doberman pinschers. Multifocal retinal dysplasia (malformation of the retina) is found in English springer Spaniels; collie eye anomaly in collies, Shetland sheepdogs, and Australian shepherds; retinal dystrophy in Briards, photoreceptor dysplasia (malformation of the cells that perceive light and color) in Collies, Irish Setters, miniature schnauzers, and Norwegian elkhounds.

 

Ocular abnormalities can also develop spontaneously (e.g., colobomas of ther anterior) or occur in utero. Exposure to toxic compounds, lack of nutrients, and systemic infections and inflammations during pregnancy (such as panleukopenia) are other potential risk factors for ocular abnormalities.

 

Symptoms and Types

 

There are a variety of abnormalities that can affect a dog’s eye or surrounding tissues. The following are some of the more common issues and their corresponding signs:

 

• Colobomas of the lid
  • May appear as notch in eyelid, or tissue of the eyelid may be missing
  • Variable eyelid twitching and watery eyes
• Colobomas of the iris
  • Misshapen iris
  • Sensitivity to bright light
  • Does not typically affect vision
  • Most common in herding dogs (i.e., Basenji, Collie, Australian sheepdog)
• Persistent pupillary membranes (PPM)
  • Fetal tissue will remain on the eye after birth
  • Variable iris defects
  • Variable cataracts
  • Variable colobomas of the uvea
  • Common in Basenjis
• Dermoids
  • Tumor-like cysts on eyelid(s) conjuctiva, or cornea
  • Variable eyelid twitching and watery eyes
• Iris cysts
  • Often not visible, as the cyst is located behind the iris
  • May not have symptoms besides slight bulging of the iris, unless the cyst is interfering with the field of vision
• Congenital glaucoma (high pressure within the eye) with buphthalmos (abnormal enlargement of eyeball)
  • Tearing
  • Enlarged, red, and painful eye
• Congenital cataracts
  • Cloudiness in the eyes
  • Often inherited (e.g., Cavalier King Charles spaniels)
• Congenital keratoconjunctivitis sicca (KCS)
  • Also referred as dry eye
  • Common in Yorkshire terriers
• Other congenital issues
  • Lack of pupils or abnormally-shaped pupil
  • Lack of tear duct openings (Cocker Spaniels)
  • Lack of iris
• Persistent hyperplastic tunica vasculosa lentis (PHTVL) and persistent hyperplastic primary vitreous (PHPV)
  • Begins in utero, with progressive atrophy of the vascular system that supports the eye lens
  • Common in Briards, Cocker Spaniels, beagles, rottweilers
• Retinal dysplasia
  • Appears as folds or rosette shapes on the retina
  • Common in Briards
• Retinal detachment
  • Retina detaches from the back of the eye causing blindness
  • Common in Labrador retrievers, Bedlingtons, and Sealyham terriers
• Photoreceptor dysplasia
  • Night blindness (when rods are affected)
  • Day blindness (when cones are affected)
  • Slow or absent pupillary reflex to light (when pupil does not contract or dilate normally)
  • Involuntary eye movement
• Optic nerve underdevelopment
  • Often results in blindness
  • Common in Miniature and toy poodles
• Rod-cone malformation
  • Rod and cone malformation common in Irish setters and collies
  • Rod malformation common in Norwegian elkhounds
  • Cone malformation in Alaskan malamutes

 

In addition, hereditary defects, such as corneal opacities, PPM, cataracts, retinal detachement, and dysplasia, are often associated with the following factors:

• Abnormally small eyes
• Missing eyeball
• Hidden eyeball (due to other eye deformities)

 

Causes

 

• Genetic
• Spontaneous malformations
• Uterine conditions (e.g., infections and inflammations during pregnancy)
• Toxicity during pregnancy
• Nutritional deficiencies during pregnancy

 

Diagnosis

 

You will need to provide as much of your dog’s medical history as you have available to you, such as in utero conditions (i.e., whether its mother was ill, her diet, etc.), and the dog’s development and environment after birth. After taking a thorough history, your veterinarian will test the health of the eye.

 

A Schirmer tear test may be used to see if your dog’s eyes are producing an adequate amount of tears. If high pressure in the eye (glaucoma) is suspected, a diagnostic tool called a tonometer will be applied to your dog’s eye to measure its internal pressure. Abnormalities within the eye, meanwhile, will be examined with an indirect ophthalmoscope and/or a slitlamp biomicroscope.

 

An ultrasound of the eyes may also reveal problems with the lens of the eyeball, the vitreous humor (the clear fluid which fills the space between the lens and retina), the retina, or other problems that are taking place in the posterior (back) segment of the eye. In the case of iris cysts, ultrasound will help your doctor determine if the mass behind the iris is in fact a cyst or a tumor. Cysts do not always behave uniformly: some grow, while others shrink. In most cases follow-ups to check the progress of the cyst will be the extent of treatment, until further intervention is warranted.

 

Another useful diagnostic method called angiography can also be used for viewing problems in the posterior of the eye, such as detachment of the retina and abnormal blood vessels in the eye. In this method, a substance that is visible on X-ray (radiopaque) is injected into the area that needs to be visualized, so that the full course of blood vessels can be examined for irregularities.

 

 

Uveal Melanoma in Dogs

 

The uvea is the part of the eye that is made up of the iris (the colored part of the eye surrounding the pupil), the ciliary body (which produces the fluid within the eye [aqueous humour] and controls the ciliary muscle contractions that aid in near focus), the choroid (which provides oxygen and nourishment to the retina – the inner surface of the eye), and the pars plana (at the front of the eye, where the iris and sclera [white of the eye] touch). A melanoma is clinically characterized by malignant growth of melanocytes, cells that are dark in appearance due to the inclusion of the melanin pigment.

 

Uveal melanomas usually arise from the front of the iris’ surface, with extension to the ciliary body and choroid. These tumors tend to be flat and diffuse, not nodular (unlike intraocular melanomas, which are raised masses). Such tumors initially have a benign (non-spreading) clinical and cellular appearance. Uveal melanomas are the most common primary intraocular neoplasm in dogs. They are usually benign and unilateral, affecting the anterior uvea most often. However, uveal melanomas are just as often capable of destroying the eye. Anterior uveal melanomas have a four percent rate of cancerous spread through the bloodstream to the lungs and visceral organs. Choroidal melanomas rarely metastasize.

 

Symptoms and Types

 

Anterior Uveal Melanoma

• Pigmented scleral (white part of the eye) or corneal (the transparent front part of the eye) mass
• Pigmented mass visible
• Irregular pupil
• Inflammation of the eye (the uvea)
• Glaucoma (Increased pressure in the eyes)
• Hyphema  (Blood in the eye)
• No vision loss unless mass obstructs the pupil or glaucoma has developed

 

Choroidal Melanomas

• Often missed because of tumor location
• Mass farther back in the eye
• Very slow-growing; rarely requires removing the eye
• Rare tumor

 

Causes

 

• Unknown
• Flat, pigmented iris freckles have potential to transform into melanomas
• There is a presumed autosomal (non-sex-linked) recessive inheritance in Labrador retrievers

 

Diagnosis

 

Your veterinarian will perform a thorough physical exam on your dog, including a complete ophthalmic exam (including testing pressure within the eye and proper drainage of the eye’s aqueous humor). A complete blood profile will also be conducted, including a chemical blood profile, a complete blood count, a urinalysis and an electrolyte panel. Evidence of metastasis may may be present in the blood profile, or the blood count may show increased white blood cells, which can be indicative of the body’s immune system fighting the malignant cell growth. You will need to give a thorough history of your dog’s health and onset of symptoms.

 

X-rays and an ultrasound may also help to determine the extent of metastatic disease in the eye. During the ophthalmic exam, tonometry will be used to measure the pressure in the eyes, and gonioscopy will be used to see if the melanoma has spread to the drainage angle. Slit-lamp biomicroscopy can be used to gage the size and location of the mass. The mass should be transilluminated, a technique which uses strong light to shine through the eyeball, illuminating it throughout as an aid to diagnosis. Indirect ophthalmoscopy can also be used to investigate the eye, with or without concomitant scleral indentation.

 

Horner’s Syndrome in Dogs

 

Horner’s syndrome is a nerve disorder that is characterized by a drooping eye, an eyelid that is protruding from the eye, or a severely constricted eye pupil. Any brain or spinal injury may cause this syndrome, and it has also been linked to conditions affecting the middle ear, but in many cases the origin remains unknown. The cause of Horner’s syndrome remains elusive in most cases, and it may affect any breed of dog, though it appears to be more common in male golden retrievers.

 

Symptoms and Types

 

• Smaller size eye pupil (miosis)
• Abnormal elevation of inner eyelid – located between cornea and inner corner of eyelids (third eyelid)
• Drooping of upper eyelid
• Eyes appear sunken into eye socket
• Inflammation of ear

 

Causes

 

• Unknown (idiopathic) in most cases
• Brain injury, brain stem lesions
• Brain tumor
• Spinal cord lesions
• Infections

 

Diagnosis

 

You will need to give a detailed history of your dog’s health, onset and nature of symptoms, and possible incidents that might have brought this condition on, such as brain trauma, injury to the head or back, ear infections, and any other previous health problems. The veterinarian will perform a thorough physical exam on your dog, with a standard blood blood count, blood profile, and urinalysis. The routine laboratory tests are not required for diagnosis of this syndrome, but may be useful for determining other diseases or infections that may be present.

 

Radiography remains the important technique for evaluating brain and spinal cord lesions, and skull X-rays are helpful for evaluation of ear problems. More advanced techniques like computed tomography (CT-scan), magnetic resonance imaging (MRI), and ultrasonography are also frequently used to diagnose this syndrome. In some cases, a cerebrospinal fluid (CSF) sample is taken to analyze for brain and spinal cord disease.

 

Hypopyon and Lipid Flare in Dogs

 

An inflammatory breakdown of the blood-aqueous barrier that allows for entry of blood cells into the front (anterior) chamber of the eye, further allowing for an accumulation of white blood cells in this this chamber, is characteristic of a condition known as hypopyon. Chemoattractants, the chemical substances that influence the migration of cells, can act as a conveyor for this cellular movement. The cells often settle in place because of gravity, forming a fluid line in the lower front chamber of the eye.

 

Lipid flare, on the other hand, resembles hypopyon, but the clouded appearance of the anterior chamber is caused by a high concentration of lipids (the fatty substance in the cells) in the aqueous humor (the thick watery substance between the eye’s lens and cornea). It requires a breakdown of the blood-aqueous barrier and concurrent hyperlipidemia (an elevation of lipids in the blood stream) to occur. There is no age, gender or breed predilection.

 

Symptoms

 

Hypopyon

• White to yellow opacity within the anterior chamber
• May be an accumulation of cells in the lower area, or it may completely fill the anterior chamber
• Concurrent ophthalmic signs can include:
  • Blepharospasm (twitching of the eye)
  • Epiphora (excessive tear production)
  • Diffuse corneal swelling
  • Aqueous flare
  • Miosis (constriction of the pupil of the eye)
  • Swelling of the iris
  • Vision loss/blindness

 

 Lipid flare

• Diffuse milky appearance of the anterior chamber
• Usually obscures visualization of structures within the eye
• Concurrent ophthalmic signs may include:
  • Vision loss
  • Mild blepharospasm (twitching)
  • Mild to moderate diffuse corneal swelling

 

Causes

 

Hypopyon

Any underlying condition which causes uveitis – inflammation of the middle layer of the eye – can result in hypopyon. Most commonly, hypopyon is associated with severe forms of uveitis, but hypopyon can also result from tumor cell accumulation in cases that involve ocular lymphoma (eye tumors).

 

Lipid Flare
Lipid flare often results from a condition of hyperlipidemia (raised or abnormal levels of lipids – the fatty substance of the bloodstream – in the blood stream), and concurrent breakdown of the blood-aqueous barrier (due to uveitis). Hyperlipidemia may also destabilize the blood-aqueous barrier directly. High levels of lipids in the circulating blood following a meal (postprandial lipemia) may occasionally result in the appearance of lipemic aqueous if uveitis is present.

 

 

Diagnosis

 

Your veterinarian will perform a thorough physical and ocular examination on your dog, taking into account the background history of symptoms and possible incidents that might have led to this condition.

 

Hypopyon may be diagnosed by the presence of fibrin (the protein end product of coagulated blood) in the anterior chamber – generally forms an irregular clot, not a ventrally located horizontal line.

 

Lipid flare will need to be differentiated from severe aqueous flare, which does not appear as milky/white as lipid flare. Dogs that are affected with severe aqueous flare generally exhibit much more ocular pain than animals with lipid flare.

 

Diffuse corneal edema, a severe corneal edema, may be confused with anterior chamber opacity, but corneal stromal (connective tissue) thickening, keratoconus (degenerative non-inflammatory disorder of the eye), and corneal bullae (fluid-filled blister) are more typically noted with diffuse corneal edema than with hypopyon or lipid flare.

 

Iris Atrophy in Dogs

 

The degeneration of the iris — the colored part of the eye — is referred to as iris atrophy. This can be as a result of normal aging or, if due to a secondary type, because of chronic inflammation or high intraocular pressure, which is often associated with glaucoma. Iris atrophy can affect any breed, but appears to be more common in small breed dogs, such as chihuahuas, miniature poodles, and miniature schnauzers.

 

Symptoms and Types

 

Vision is not usually affected by iris atrophy, but there may be some sensitivity to light. Other typical symptoms associated with this of disorder include:

 

• Incomplete pupillary light reflex, accompanied by a normal menace response (the reflex to close the eyes when a finger is stabbed toward the eye)
• Unilateral — may note unequal pupil sizes (anisocoria)
• Irregular, scalloped edge to the pupillary margin
• Thin or absent areas of the iris on transillumination
• Strands of iris occasionally remain, spanning across portions of the pupil
• Holes within the iris stroma — black spots that may resemble additional pupils
• Swelling (edema) of the cornea

 

Causes

 

• Normal aging
• Uveitis (inflammation of the uvea portion of the eye)
• Glaucoma

 

Diagnosis

 

Your veterinarian will perform a thorough physical and ophthalmological exam on your dog. The initial goal will be to differentiate iris atrophy from congenital iris anomalies, as there are a variety of other eye issues that can be the cause of the symptoms, such as iris aplasia (failure of the iris to develop normally), iris hypoplasia (underdevelopment or incomplete development of the iris), iris coloboma (a complete, full-thickness area of lack of development of all layers of the iris), and polycoria (when more than one pupil is present in a single iris within the animal’s eye, each with the apparent ability to constrict).