Glaucoma is caused by an increase in fluid pressure within the eyeball. Normally, there is a continuous (although very slow) exchange of fluid between the eyeball and the venous circulation. Anything that alters this delicate balance can cause a buildup of pressure and produce inflammation. When the pressure inside the eye becomes higher than blood pressure, blood cannot enter the eye to nourish the retina.
Inflammations and infections within the eye are the most common causes of acquired or secondary glaucoma in cats (uveitis). Other causes are cataracts, eye injuries and cancers inside the eye. Cataracts are defined as any opacity in the lens that interferes with the transmission of light to the retina. A spot on the lens that blocks the light, regardless of its size, technically that is a cataract.
All types of cataracts are uncommon in cats. Most cataracts are caused by eye injuries and infections. Hereditary cataracts may be accompanied by other ocular birth defects, such as microftalmia (abnormally small eye) or persistent pupillary membrane (which is a tissue tag through the iris or iris to the cornea). Cataracts develop in diabetic cats, but this is not common.
In reference to glaucoma, a lens that is out of alignment can block the outflow of aqueous humor. Primary or congenital glaucoma is uncommon, but it has been observed in Persian, Siamese and domestic shorthair cats.
A cat suffering from acute glaucoma exhibits a mild to moderate tearing and narrows the eyes, in addition there is a slight redness of the white part of the eye. The affected pupil is slightly larger than the opposite pupil. They notice pain in the eye when they are gently pressed and it feels harder than the other healthy eye. As the fluid pressure increases to more than 30 to 50 mmHg, the eye becomes noticeably larger and the surface begins to bulge. The normal pressure is 10 to 20 mmHg. Over time, the retina becomes damaged. The lens can be pushed completely or partially out of alignment. This whole sequence can occur suddenly or in a matter of weeks.
To diagnose glaucoma, intraocular pressure is measured with a technique called tonometry, which uses an instrument placed on the surface of the eye. The inside of the eye must also be examined. With a procedure called gonioscopy, fluid flow out of the eye is checked. Ultrasound can also be used to evaluate the eye.
Every effort should be made to distinguish glaucoma from conjunctivitis and uveitis, which produce similar signs. It is vital for your cat's eye health, to start glaucoma treatment before an irreversible retinal injury occurs. Some cats can suffer a permanent loss of vision, so they can be lost before the disease is discovered.
What is glaucoma?
Glaucoma is a excess fluid inside the eye. Normally, the internal structures of the eye continuously synthesize fluids slowly, and then be drained. However, when this synthesis of fluids occurs excessively, excess fluid does not drain quickly enough so that it accumulates, causing significant intraocular pressure.
It is a disease that can be inherited, or appear as a symptom of another pathology such as uveitis or trauma to the eye. In addition, it can also be acute or chronic depending on how fast it develops.
What are the symptoms?
A cat whose eye has or begins to have an accumulation of fluids may have the following symptoms:
- Acute glaucoma: color change in the cornea, dilated and fixed pupil, redness of the eye and possible loss of vision.
- Subacute glaucoma: bluish cornea, visual impairment, in addition to deformity and dilation in the pupils and redness of the eye.
But there will be not only changes in the eye, but also in the behavior of the cat. Apathy, loss of appetite and depression are signs to pay attention to.
In case we suspect you have glaucoma we must take it as soon as possible to the veterinarian. There they will measure your intraocular pressure and examine the inside of your eye to see how much fluid flow there is. If the disease is confirmed, depending on the case, it will give you eye drops to reduce the pressure. When the damage is irreversible, you will choose to remove the eye to prevent infections.
Do not let time pass. For the sake of the cat itself, it must be taken to be examined at the slightest sign of illness. Glaucoma does not heal on its own.
What is glaucoma in dogs and other animals?
Glaucoma in dogs, cats and other animals encompasses a group of diseases that cause progressive damage to the optic nerve, with the consequent decrease in the visual field.
It can affect one eye or both, it does not give symptoms until it is very advanced, and if it is not treated properly it can lead to blindness.
All animals can have glaucoma, in all species.
What is primary or genetic glaucoma? And the secondary glaucoma?
The primary glaucoma It is due to genetic or anatomical causes that prevent the correct circulation of aqueous humor within the eye.
The aqueous humor is a liquid that bathes the eye structures and is continually being renewed to maintain the optical properties of the eye. It is manufactured in one part of the eye and removed by another, but in some cases there may be difficulties for the outflow, so that excess fluid causes an increase in intraocular pressure, and irreversible damage to the optic nerve.
The secondary glaucoma It is the one that appears after trauma or illness. In cats this is the most frequent type of glaucoma.
The Bichón Maltese is one of the races with the greatest predisposition to glaucoma. Photo: Tegioz
Are there more breeds predisposed to glaucoma?
In dogs, primary or genetic glaucoma is more common. There are dog breeds more predisposed to develop glaucoma, such as Cocker, the Bichon Maltese or the French bulldog.
In cats, on the other hand, congenital or primary glaucoma rarely occurs. Glaucoma in cats is usually secondary to other problems such as chronic uveitis or lens dislocations.
The French Bulldog is prone to glaucoma
How do I know if my pet has glaucoma?
The evolution of glaucoma can be slow and asymptomatic, since the loss of visual field caused by glaucoma is progressive.
Only by proper examination with the appropriate means can the diagnosis of glaucoma and its early treatment be confirmed.
The animal with glaucoma adapts to the loss of visual field without realizing it, but over time, if left unchecked, it will be increasingly difficult for it to function normally.
In advanced stages of the disease, we will notice it for a special irritability and even aggressive behavior, as it will get pain.
Acute attacks of glaucoma cause red eyes, blurred vision, severe pain and even nausea and vomiting.
If it is not treated in time, or is monitored on a regular basis, glaucoma can affect the character and end up causing blindness in the affected eye.
Summary of glaucoma symptoms
- No visible symptoms
- Progressive reduction of the visual field, to which the patient adapts without realizing
Advanced glaucoma or acute attacks of glaucoma:
- Red eyes
- Blurry vision
- Intense pain
- Nausea, vomiting
- Irritability and aggressive behavior
At what age does glaucoma usually manifest in dogs and cats?
Glaucoma in pets is usually a genetic problem, so it can appear in very young patients, usually between 2 and 5 years in the most predisposed breeds of dogs, such as Cocker, the Bichon Maltese or the French bulldog.
In cats, glaucoma appears more frequently associated with trauma or other diseases, so there is no determined age.
In all animals, the incidence of glaucoma increases with age.
Olivia is a 2-year-old Shih Tzu who visits us from Andorra to check her glaucoma. Medical treatment allows you to keep your intraocular pressure controlled.
Can glaucoma be prevented in animals?
The only way to prevent glaucoma is through an ophthalmologic examination to detect genetic predisposition or anatomical features.
In some cases, due to the history of parents or siblings, the owner already knows that the animal may be more predisposed to develop it, and in these cases it can be prevented with preventive medication and regular controls.
In other cases, if what is called a "narrow angle" or "dysplastic angle" is detected, it is advisable to start preventive medication with a few drops at night.
Being a strictly ocular pathology, external factors do not have a high incidence in glaucoma, although factors such as arterial hypertension can worsen its evolution and complicate control.
Dr. Paco Simó tells us what glaucoma is treated in companion animals:
How is a pet suffering from glaucoma treated?
Glaucoma treatment aims to preserve vision.
Early detection is essential, since the vision lost by glaucoma is not recovered.
The only known risk factor that can be fought against is high intraocular pressure, which can be avoided in two phases:
- Medical treatment: It is the treatment of choice in milder cases, in which glaucoma is usually managed. If medical treatment does not give the expected result, surgical treatment is chosen.
- Surgical treatment: There are two types of glaucoma surgeries:
- Those that seek to reduce liquid production>
Eye image with glaucoma. Ophthalmologic review is the only way to prevent glaucoma in dogs and cats. Photo: IVO
Acute glaucoma may require emergency hospitalization. Veterinarians use various topical and oral medications to lower intraocular pressure. Mannitol can be used in the short term to reduce eye pressure.
Maintenance medications are used for chronic glaucoma. These may include carbonic anhydrase inhibitors topically or orally and possibly pilocarpine. Any underlying eye disorder must be treated. The treatment will last as long as the cat lives.
The lack of response to medical treatment may suggest surgery, if there is a potential for vision retention. Surgery may try to decrease the production of fluid or increase the flow rate of the eye fluid, in order to reduce the pressure inside the eye. If the eye is blind and also hurts, the best approach is to eliminate the entire eye. A prosthesis can be inserted by appearance.
Some damage to secondary nerves of glaucoma is believed to be due to cellular chemical glutamate. Glutamate is an amino acid and is extremely toxic to retinal ganglion cells, basically it stimulates them excessively. Drugs that block glutamate receptors, and calcium channel blockers that are used to protect the retina and optic nerve, are being studied for possible therapy.
Symptoms of glaucoma in cats
Glaucoma is a silent disease that affects cats, dogs and humans very similarly. Their first symptoms are usually general and not very specific, making them difficult to recognize in cats. Many tutors only perceive some anomaly when their minimum eye shows a blurry appearance or win a bluish hue or grayish, with an obvious pupil dilation. Others arrive at the veterinary clinic telling that their cats began to walk in an unusual way, collapsing or hitting with household objects. In these instances, it is likely that the cat has lost much of his vision, which explains his difficulty in recognizing obstacles in his path.
To enable an early diagnosis of glaucoma, it is important to be aware of your cat's body language to quickly recognize any change in its expression or behavior. The first signs of glaucoma in cats are:
Causes of glaucoma in cats
Feline glaucoma can be primary or secondary, depending on the cause that causes it. Like any degenerative disease, glaucoma has an important genetic load. However, this degenerative process can also be caused by another underlying disease. Inflammations and ophthalmic infections, such as uveitis, cataracts and neoplasms, are among the most frequent causes of acute glaucoma in cats. In addition, eye injuries due to street fights, traumas or accidents can trigger an infectious process that favors the development of glaucoma in felines.
When glaucoma develops as a result of trauma or some underlying pathology, it is considered secondary or acute, while when it occurs for reasons of genetics or malformation, it is primary.
Is it possible to prevent glaucoma in cats?
We cannot intervene in the genetic inheritance of our cats, but we can offer them adequate preventive medicine, a positive environment and the necessary care to help them strengthen their immune system and maintain their good health. For this, it is essential to provide them with a balanced diet and keep them physically and mentally stimulated throughout their lives. Also remember to make regular visits to the veterinarian every 6 months, in addition to respecting your vaccination letter and periodic deworming. And do not hesitate to immediately turn to the professional of your trust when identifying any change in the appearance or behavior of your cat.
This article is purely informative, at ExpertAnimal.com we have no power to prescribe veterinary treatments or make any kind of diagnosis. We invite you to take your pet to the veterinarian in case he presents any type of condition or discomfort.
If you want to read more articles similar to Glaucoma in cats - Causes, symptoms and treatment, we recommend you go to our Eye Problems section.
Symptomatology and characteristics
The symptomatology depends on the stage of glaucoma (acute, subacute or chronic), what the owner can see will be:
- Eye pain (blepharospasm, eye or eyes closed)
- Bluish cornea (change in eye color for corneal edema)
- Dilated and fixed pupil (mydriasis)
- Very red eye (reddened sclera)
- Visual impairment
- Anorexia and depression
- Eye pain (blepharospasm)
- Bluish cornea
- Blindness or visual impairment
- Deformed, dilated and fixed pupils
- Very red eye
- Anorexia and depression
- Variable eye pain
- Vascularization, pigment and corneal edema
- Lenticular opacification
- Red or very red eye
- Blindness or visual impairment
- Dilated, fixed and abnormal pupils
- Anorexia, depression, shyness or aggression
- Increase of the eyeball and appearance of descent lines (depending on species) There may be increases in pressure without symptoms, this process is known as ocular hypertension and is not the same as glaucoma, hypertension can degenerate into glaucoma so it is recommended preventive treatment if necessary or eliminate the cause of it (intense stress for example)