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Basics ⬇

Outline

BASICS

Overview!!navigator!!

Calcific band keratopathy consists of depositions of calcium (hydroxyapatite) in or adjacent to the basement membrane of the corneal epithelium and anterior stroma and is a possible complication of chronic uveitis. The ophthalmic system is affected.

Signalment!!navigator!!

All ages and breeds affected.

Signs!!navigator!!

  • In addition to signs of chronic uveitis (e.g. synechiae, miosis, aqueous flare), variably dense, white, dystrophic bands or chalky plaques are noted in the interpalpebral region of the central cornea. These areas are often associated with scattered areas of fluorescein retention, usually the result of the lesions elevating the overlying epithelium
  • Calcium deposited at the level of the corneal epithelial basement membrane may accumulate and disrupt the epithelium to result in painful ulcers and a secondary reflex uveitis

Causes and Risk Factors!!navigator!!

The exact pathogenesis of calcium band keratopathy is unknown. It is an occasional complication of chronic cases of uveitis and has been noted following the chronic application of topical corticosteroids or phosphate-containing solutions (usually as a therapy for uveitis). Alterations of pH in the superficial cornea of the interpalpebral space and evaporation of tears in the same region have been postulated as contributing factors for the development of this condition.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Lid abnormalities such as distichiasis, trichiasis, and entropion resulting in keratitis and corneal injury; bacterial or fungal keratitis; eosinophilic keratitis; corneal lipid degeneration; neuroparalytic and neurotrophic keratitis; keratoconjunctivitis sicca; corneal dystrophies; corneal foreign bodies; and chronic epithelial erosion (indolent ulceration).

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests, Diagnostic Procedures!!navigator!!

  • Rule out infectious causes (bacterial or fungal) with corneal scrapings for cytology and culture. Scraping procedure causes audible and tactile evidence of mineralization
  • The dull, gritty appearance and character of corneal calcium are helpful in the diagnosis
  • Biopsy sample can be taken to histologically support the diagnosis of calcific band keratopathy. Von Kossa and alizarin red stains can detect the presence of calcium

Imaging!!navigator!!

N/A

Pathologic Findings!!navigator!!

  • Special stains (e.g. Kossa's method or alizarin red) confirm the presence of calcium deposits at the level of the lamina propria of the epithelium and underlying superficial stroma
  • Vascularization is often noted, and an associated lymphocytic and neutrophilic cellular reaction is frequently present around the calcium deposits

Treatment ⬆ ⬇

TREATMENT

  • Superficial keratectomy is recommended. If calcific deposits are not removed, affected eyes remain painful despite medical treatment because of persistent or recurrent ulceration. Debridement with a diamond burr or application of topical EDTA during debridement may be effective in removing some superficial mineral
  • Inappropriate topical corticosteroid therapy may cause delayed corneal healing

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Topically administered calcium-chelating drugs (dipotassium EDTA 13.8%; Sequester-Sol) to dissolve the calcium deposits are usually only helpful if the corneal epithelium is absent or compromised
  • Topical antibiotic (e.g. chloramphenicol, bacitracin–neomycin–polymyxin B), atropine (1%), and systemic nonsteroidal anti-inflammatory drugs (e.g. flunixin meglumine 0.25–1 mg/kg BID PO, IM, IV) should be used to protect any ulcerations and treat any resultant uveitis until the keratectomy site heals

Contraindications/Possible Interactions!!navigator!!

Risk of opportunistic infections due to topical corticosteroids for treatment of uveitis. The rate of post-keratectomy infections can be high, usually owing to a compromised cornea from chronic uveitis or prior use of topical corticosteroids.

Follow-up ⬆ ⬇

FOLLOW-UP

Expected Course and Prognosis

  • Healing of keratectomy sites can occur with slight to severe scarring
  • Recurrence of calcium band keratopathy is possible with continued episodes of uveitis
  • The prognosis for vision is guarded because of subsequent corneal scarring and further uveitis episodes
  • Horses with dystrophic calcification due to severe corneal injury or infection in areas other than the interpalpebral fissure usually fare better than those with palpebral fissure lesions

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Complication of uveitis.

Suggested Reading ⬆ ⬇

Brooks DE. Ophthalmology for the Equine Practitioner, 2e. Jackson, WY: Teton NewMedia, 2008.

Brooks DE, Matthews AG. Equine ophthalmology. In: Gelatt KN, ed. Veterinary Ophthalmology, 4e. Ames, IA: Blackwell, 2007:1165–1274.

Gilger BC, ed. Equine Ophthalmology, 3e. Ames, IA: Wiley, 2017.

Author(s) ⬆

Author: Caryn E. Plummer

Consulting Editor: Caryn E. Plummer