Clinical Vignette—Initial Presentation
A 6-year-old female spayed German shepherd presents with the owner complaint of red eyes and decreased vision. Examination reveals bilateral corneal edema (white) with branching vascularization and raised vascularized tissue (granulation tissue), and focal spots of brown pigmentation. There is only a small clear window of cornea left medially. From what can be seen, the intraocular structures appear normal. There is minimal discharge and no blepharospasm. The bulbar conjunctiva is markedly hyperemic.
Problem Definition
The cornea plays a critical role in the two most important aspects of ophthalmology—vision and comfort. Corneal disease affects the transparency of the cornea that impacts vision (Table 49-1). Wounding of the cornea causes marked ocular pain and distress. The cornea may also be affected secondarily by intraocular disease. Understanding the signs of superficial versus deep corneal disease and the diagnostic tests appropriate for each will direct the practitioner toward an accurate diagnosis and treatment plan.
Pathophysiology
The cornea maintains transparency by the epithelium on the surface that provides a barrier to the tear film as well as to surface pathogens, and by the endothelium that uses an active pump mechanism to keep the corneal stroma from imbibing aqueous. The cornea is avascular in health, receiving nutrition from the tear film and aqueous. Any disease process that damages the epithelium or endothelium can result in corneal edema. Any disease process that results in corneal vascularization can affect corneal transparency by the vessels alone or associated edema, cellular infiltrate, fibrosis, crystalline infiltrates, or pigmentation. Corneal vascularization is a unique phenomenon in that it occurs as a healing response or when the cornea is being deprived of its normal source of nutrition—both serving as an effort to preserve the cornea; however, the end result can be loss of corneal transparency that is essential for normal vision.
TABLE 49-1. Types and descriptions of corneal opacities
| Type | Description |
| White | |
| Edema | Smokey blue/gray/white; can be focal or diffuse |
| Cellular | White, cream, or yellow; usually indicates presence of white blood cells within the cornea, often associated with infectious agent (bacteria primarily, less commonly fungal); usually associated with blood vessels Other cellular infiltrates: fungal hyphae, epithelial inclusion cyst |
| Fibrosis | White, homogeneous; density depends on the depth of the scar (the deeper the injury/disease usually the denser the scar); may be associated with chronic blood vessels |
| Crystalline | Cholesterol: a fine glitter-like, white, refractile appearance Calcium: refractile but less sparkly than cholesterol; with magnification they appear like tiny etching lines in glass; when scraped they have a gritty texture |
| Keratomalacia | White, gelatinous texture to cornea (“melting”) |
| Red | |
| Blood vessels | Superficial: branching and crossing the limbus Deep: coming from the limbus; usually straight with less large branching Chronic: thinner caliber and/or isolated with large branching (“tree”) Active: larger caliber and/or intense branching (“bush”) |
| Granulation tissue | Pink-red, raised tissue always associated with blood vessels |
| Stromal hemorrhage | Uncommon; geriatric dogs seem predisposed; small, focal red spot as if placed by a light paint brush stroke; may or may not have a small vessels associated with it; etiology is unclear but should rule out systemic hypertension |
| Neoplasia | Rare; originate at the limbus; squamous cell carcinoma is raised with an irregular surface; hemangioma/hemangiosarcoma appear as predominantly vascular growths |
| Brown/black | |
| Pigment | Superficial: brown pigment indicates chronic irritation to the cornea, or can be seen as part of a corneal scar Deep: dark brown pigment on the ventral corneal endothelium is usually due to ruptured iris cysts |
| Sequestrum | Can be a pale amber to brown to black; occurs in cats; may or may not have associated blood vessels; represents a necrotic area of stroma |
| Neoplasia | Epibulbar melanomas originate on the sclera but can extend into the cornea; dark brown to black, smooth, round and well demarcated |
| Iris prolapse | Dark brown to black pigmented area in the base of a ruptured descemetocele or protruding from a ruptured descemetocele or laceration; associated with anterior synechia and hyphema |
Corneal Disease
Corneal disease can be divided into superficial or deep, and ulcerative or nonulcerative (Tables 49-2 and 49-3
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
