Feline keratitis and conjunctivitis (Proceedings) - Veterinary Healthcare


Feline keratitis and conjunctivitis (Proceedings)


Eosinophilic keratoconjunctivitis may be a bilateral disorder with no other history of eye disease consistent with FHV-1, or present unilaterally (occasionally bilateral) with a history consistent with previous FHV-1 infection. With the former presentation, it is usually young mature to middle aged cats (3-8 years). It is not necessarily a symmetric presentation. White to grey "plaques" appear on the corneal surface and over raised areas of lateral or nasal limbal neovascularization. It may or may not be painful and appears to be fairly seasonal in occurrence with summer months more common. Diagnosis is obtained via scrapings and cytology which show eosinophils, eosinophilic granules and occasional mast cells. This disease presentation often responds well to topical and/or systemic corticosteroids. When patients present with a history of previous FHV-1, topical steroids must be used with caution. These patients may have other prior signs (keratitis, dendritic ulcers, conjunctivitis, sequestra, symblepharon) and may respond well to topical/systemic steroids, or the eye may worsten (so monitor them closely). Systemic and topical antivirals are indicated when obvious ulcers are present and may be iniated prior to the use of topical steroids for safety. Systemic steroids in lieu of topical steroids in conjunction with antivirals may also be initiated in some refractory cases. Megestrol acetate 2.5-5mg mg per day for first 7-10 days, followed by weaning to a final dose sometimes as low as 1.25 mg every other week can be attempted,when topical therapy is not possible due to owner or patient compliance. Owners must be warned of the risks of diabetes mellitus and mammary gland hyperplasia with the use of Megestrol acetate and bloodwork must be submitted prior to the initiation of this medication.

Stromal keratitis patients often present with blepharospasm, the appearance of corneal edema (corneal infiltrates) and neovascularization. Often there is a history of conjunctivitis that was treated with topical or oral steroids. This condition is thought to represent a hypersensitivity to stromal viral antigens. Therefore, antiviral therapy alone or along with JUDICIOUS use of topical steroids can help control this painful condition. I will usually start topical antivirals alone. If disease progression is seen, I will add in oral antivirals. If the disease continues to progress, I may increase the dose of oral antivirals or initiate topical steroids, always warning clients of the potential for worsening the disease.

Symblepharon is a term that describes "adhesions" that occur between the conjunctiva, either to itself or to the cornea. It may involve the bulbar, palpebral or third eyelid conjunctiva. It will often result in a lack of palpebral/bulbar cul-de-sacs due to scarring and may appear as a membrane covering the entire corneal surface. It is often seen secondary to early FHV-1 infections and/or neonatal ophthalmia and tends to affect young cats in first few months of life. It is the most common cause of chronic epiphora in young cats due to the nasolacrimal duct system scarring over. If the cat is visual and comfortable without restriction to movement of the third eyelid, no therapy is necessary. If the cat is visually impaired, surgical excision of these membranes from the cornea, and/or manual break down of these adhesions can be attempted to reconstruct the conjunctival the cul-de-sacs. Concurrent antiviral therapy until the corneal and conjunctiva is healed is recommended. Recurrence of these adhesions is common and surgery often frustrating in severe cases.

Keratoconjunctivitis sicca is not commonly recognized in cats, and if often misdiagnosed given tear production in cats is normally lower than it is in dogs. Schirmer Tear Tests in cats can also be difficult to interpret because the sympathetic nervous system can cause STT values to be very low in normal cats. The diagnosis can made based on both low STT (commonly 5 or less) and other clinical signs such as a lackluster (dull appearing) cornea, a horizontal axial band of exposure keratitis, and often superficial corneal neovascularization. The heavy blood vessel in-growth, scarring and pigmentation seen in dogs is not common in cats with KCS. Some feel that FHV-1 infection is the initiating cause of KCS in most cats and is not immune mediated as it is in dogs. Therefore, therapy involving the use of cyclosporine-A may not be effective and must be used with caution as it may cause herpes recrudescence. Topical or systemic pilocarpine seems to do little good (as in dogs). Supportive lubrication works well and is recommended in all affected cats with conjunctivitis. Newer products that contain preservative free sodium hyaluronate are well tolerated and seem to make these patients more comfortable.


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