Cloudy Eye: Etiology, Pathology, Diagnosis & Treatment

Overview

A condition where the eye appears to be cloudy or have material in the anterior chamber that makes it appear cloudy , so it is called Cloudy Eye.
Cloudy Eye

Etiology

Most commonly the condition is due to a local or systemic infection but may also be due to rapid changes in water quality (i.e., ammonia, nitrites, pH, salinity or osmolality). Several protozoan parasites such as Ichthyophthirius multifiliis, Cryptocaryon irritans, and Tetrahymena corlissi have been known to directly infest the epithelium of the cornea, causing it to become cloudy. Occasionally monogeneans (e.g., Neobenedenia sp.), turbellarians, and copepods (e.g., Lernaea spp. and Argulus spp.) may directly parasitize the cornea and surrounding tissues of the eye. Lymphocystis, a generally benign viral disease, has also been reported to affect the cornea and retrobulbar tissues of the eye. Larval digenetic trematodes (e.g., Austrodiplostomum spp.) can invade the anterior and posterior chambers of the eye. Dietary deficiencies, such as vitamin A, thiamin or riboflavin, may also contribute to the development of cloudy eye in fish. 
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Route of transmission

Depends on specific etiology. Host range: All fish species are presumably susceptible to the various conditions that cause cloudy eye. Clinical presentation: The condition may be due to corneal edema, corneal opacity or material in the aqueous humor of the eye, all of which may cause the cloudy eye appearance and compromise vision.

Pathology

Both ulcerative keratitis and nonulcerative keratitis can result in corneal edema and a cloudy appearance to the eye. Superficial abrasions of the eye can rapidly result in corneal ulcerations, which left unchecked can lead to rupture of the globe and subsequent enophthalmos Non-ulcerative keratitis can result in edema of the cornea, accumulation of cellular infiltrates and fibroplasia in the anterior chamber, giving the eye a cloudy appearance. 

Differential Diagnosis

The most common differential would be cataracts. Cloudy eye or corneal edema should not be confused with corneal opacification that commonly occurs postmortem, especially with fish that are chilled.

Diagnosis

Most commonly diagnosed by visual inspection of the eye, though the etiology may be more difficult to identify. The diagnosis should include examination of the water parameters and various systemic diseases.

Management / Control

Providing optimal water quality and adequate nutrition is essential. For infectious conditions an antibacterial or antifungal agent may be needed to resolve the situation. Administration of a topical ophthalmic therapeutic for ulcerative keratitis is accomplished by placing the therapeutic on the eye of an out-of-water sedated fish for approximately one minute before placing a layer of n-butyl cyanoacrylate or other ophthalmic adhesive over the ulcerative lesion. In freshwater fish, increasing the environmental salinity to 1–2 ppt (g/L) will reduce the osmotic gradient across the cornea and may help resolve corneal edema. Periodic monitoring for parasitic and bacterial diseases will help reduce the incidence of these etiologies.

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