Why does my cat have a black dot in its eye? Caretakers of cats suffering from feline corneal degeneration or corneal sequestration may wonder. This pathology consists of the focal degeneration of collagen together with the accumulation of pigment in the cornea of the affected cat, which manifests itself with a blackish spot oriented around the center of the small feline's eye.
In the initial stages it can be confused with a corneal ulcer, but the sequestrum evolves to a dark color that does not stain with fluorescein. This ocular disorder produces a lot of pain in our cats equivalent to the degree of penetration into the cornea, along with signs such as excessive tearing and blinking, mucopurulent discharge and photophobia, among others. The diagnosis must be made quickly, detecting the cause and being treated to solve the sequestration medically or surgically depending on the severity of the condition.
What is feline corneal sequestration?
Feline corneal sequestration, also called feline corneal degeneration, is a condition of the cornea in which there is afocal collagen degeneration and the presence of porphyrins which is a brown pigment. This pigment is diffusely located in the upper stroma of the cornea and gradually transforms into an irregular black plaque that is sometimes surrounded by new blood vessels and enters the stroma of the cornea and can perforate and even make the cat lose the affected eye.
This corneal disorder occurs primarily in cats between 2 and 7 years of age and usually only affects one of the the two eyes of the feline. With regard to racial predisposition, the Persian cat seems to suffer from it with greater prevalence, although in other breeds it can also appear more frequently, such as:
- The Siamese
- The sphynx
- The Himalayan
- The common European
- The exotic
Feline corneal sequestration symptoms
Clinical signs in cats with corneal sequestration are as follows:
- Blackish plate in a more or less central position in the cat's eye.
- Eye pain.
- Photophobia or light intolerance.
- Excessive tearing or epiphora.
- More frequent blinking or blepharospasm.
- Mucopurulent discharge.
- Corneal edema.
- Corneal neovascularization.
- Cellular infiltrate in the cornea.
- Protrusion of the nictitating membrane.
In general, a cat can be suspected of having corneal sequestration when it has a non-healing ulcer or changes color, darkening, and the cat does not want to open the eye completely, especially when there is a lot of light, it is also accompanied by pain, discharge, tearing and excessive blinking.
Here you can find more information about Cat's Eye Ulcer, its causes and treatment.
Causes of feline corneal sequestration
Now that we know what feline corneal sequestration is and its symptoms, let's see what causes it. Reports of feline corneal sequestration are not fully established but it is thought that they may be induced by continuous irritation of the cornea derived from processes such as:
- Entropion
- Corneal ulcers
- Trichiasis
- Tear film alterations
Feline corneal degeneration may also have a hereditary component, be secondary to trauma, and some authors suggest that the cause may be primary stromal dystrophy.
Another cause that has been associated with feline corneal sequestration includes feline herpesvirus infection type 1 (feline rhinotracheitis) because it is It is common for this virus to produce ocular symptoms such as ulcers or conjunctivitis, being isolated in up to 50% of cases of this condition.
Feline Corneal Sequestration Diagnosis
To diagnose corneal sequestration in a cat, a full eye examination should be performed, beginning with viewing the eye in white light to see the color of the sequestration, noticing a dark spot more or less centered on the cornea that is usually surrounded by new blood vessels and that stains with Rose Bengal and not with fluorescein.
It is a good idea to also perform a Schirmer test to determine the amount of tear produced and the measurement of intraocular pressure with a tonometer, as well as examine the fundus of the eye.
In order to diagnose a feline herpesvirus infection, you should:
- Take a conjunctival sample.
- Perform PCR.
- Use of Optical Coherence Tomography: it is a useful technique for the diagnosis of this condition and does not require sedation of the cat by not contacting the corneal surface, so you do not feel pain. This technique consists of the emission of an infrared light source that penetrates the tissues of the eye and is reflected on the retina and when it returns, the light creates an interference that produces a color image that shows the structures of the eye and its measurements. based on colors, with the cold ones indicating less thickness and the warm ones indicating greater thickness.
This technique is used for diagnosis, the decision of the surgical treatment technique and for postoperative control to assess the continuity of the layers and the integration of the graft in the cornea.
Feline corneal sequestration treatment
The treatment of feline corneal sequestration is medical or surgical depending on the severity, in addition to treating the cause that originated it, which it ranges from the use of drugs to surgery to correct damage to the eye that causes irritation.
Depending on the degree of pain and depth of the sequestration, a medical treatment will be carried out.
- In milder cases: consists of the use of antibiotic eye drops (frequently with tobramycin, chloramphenicol or ciprofloxacin), anti-inflammatories (prednisolone or dexamethasone) or ophthalmic ointments, together with recombinant interferon 2alpha and antiviral therapy (idoxyuridine, acyclovir, trifluorothymidine) in case of associated rhinotracheitis.
- In cases of greater depth of sequestration and greater pain: surgical treatment will be necessary through techniques such as keratotomy, which consists of the removal of dead tissue so that the cornea can regenerate.
- In very deep cases: corneal grafts will be necessary to fill in the removed area. Other less used techniques are corneal-conjunctival translation, flaps or corneal transplants.
