Corneal degenerations typically feature the deposition of material, thinning of tissue, and neovascularization. Primary lipid keratopathy (LK) is infrequent and occurs spontaneously as stromal deposits of cholesterol and phospholipids. Primary LK is not associated with elevated serum lipids levels.
The secondary form is associated with previous ocular injury or pathology.
Unlike the primary form, secondary LK is far more common and is characteristically associated with corneal neovascularization. This article focus mainly on the primary form of this entity.
ICD-10: H18.49 - Other corneal degeneration.
LK is a term applied to conditions where lipid degeneration of the cornea occurs. There are only a few cases of primary LK published to date.
LK is supposedly a degenerative disorder with a non-hereditary pattern of occurrence. The accumulation of lipids may result from excessive production, impaired lipid metabolization or both mechanisms.
Corneal lipid deposition may occur secondary to systemic disorders of lipid metabolism (Fish-eye disease, Tangier disease or familial lipoprotein deficiencies). The secondary form is also associated with previous ocular diseases or injury. Herpetic corneal infections are the most frequent pathologies underlying secondary LK. Although rare, it has been reported following corneal edema, as in hydrops or surgical trauma, such as Intacs implantation.
Histological evaluation shows that the keratopathy material consists of intra- and extracellular lipids. Histochemical staining (Oil red 0 and Sudan black B) indicate deposits of neutral fats and phospholipids.
Diagnosis of primary lipid degeneration is based on the presence of lipid deposits in the cornea with no prior vascularization, traumatic or inflammatory change.
Primary LK may be peripheral, central, or diffuse. The disease is usually bilateral, and the central lipid, often with cholesterol crystals, may severely decrease visual acuity. Secondary LK features are dependent on the underlying cause but frequently one can find a characteristic dense yellow-white infiltrate associated with the presence of an adjacent corneal blood vessel.
Patients complaint of progressive reduction of visual acuity due to opacification of the cornea.
The differential diagnosis should include corneal arcus. KP is frequently denser than arcus and may appear as a circular deposit adjacent to blood vessels. Schnyder corneal dystrophy and other corneal diseases with deposits such as cystinosis, tyrosinemia, hyperuricemia, multiple myeloma, monoclonal gammopathy and infectious crystalline keratopathy should also be considered. Depositions from drugs such as gold, chlorpromazine, chloroquine, and clofazimine might also result in corneal deposition.
In secondary LK treatment, should focus on the underlying disease. Abnormal vascularization may be eliminated by argon laser photocoagulation or needle point cautery to induce the absorption of the lipids through the destruction of the feeder vessels. Intrastromal anti-VEGF agents may be an effective therapeutic option for the management of corneal neovascularization.
Although primary LK is extremely rare, penetrating keratoplasty is the preferred approach. Graft outcomes appear to be favorable, possibly because of lack of neovascularization. In secondary LK, corneal grafting remains an option, but it needs a relative quiescence, and the clinical outcome is rather poor because of the corneal thinning, hypoesthesia, and sustained vascularization.
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