Corneal Edema

Cornea is a clear, transparent, dome-shaped structure that covers the front portion of the eye. An adult cornea is about 0.5 millimeters thick. It comprises five major layers, namely, epithelium (outer portion, having the ability to regenerate), Bowman's membrane (hard, protective layer), stroma (thickest layer with collagen fibrils), Descemet's membrane (thin layer) and endothelium (one-celled thick innermost layer). Since there are numerous nerve endings in the cornea, it is extremely sensitive. On the contrary, cornea is devoid of blood vessels and hence appears transparent.

Cornea functions as a powerful refracting medium, contributing the maximum focusing power to the eyes. Cornea is kept transparent for the maximum vision clarity by supplying oxygen from the tears and pumping of water from the endothelium layer. When there is excess hydration or accumulation of fluid in the cornea portion, then it causes corneal swelling; a common eye problem referred to as corneal edema.

Corneal Edema: Causes and Symptoms

Corneal edema is caused by the problems related to dehydration, viral infections, endothelial disorder, ocular surgery, traumatic injury, increased ocular pressure and at times, toxins. Among these, endothelial Fuch's dystrophy is the most common cause of corneal edema. It is a hereditary disorder, characterized by slow and gradual loss of endothelial cells. Women are at a higher risk of endothelial dystrophy than men.

An infection by herpes viruses results in inflammatory responses in the cornea, leading to corneal edema. Corneal edema may also occur immediately or few years after the ocular surgery. It may occur due to impairment of endothelial layer by ultrasound radiation, damage of Descemet's membrane and/or infusion of toxic medications in the cornea. In addition, strong topical and systemic medications can lead to corneal edema.

The most notable early symptoms of corneal edema are distorted or blurred vision, halos around light, eye discomfort, photophobia (increased sensitivity to light) and sensitivity to foreign particles. Symptoms may progress to severe pain in the eye due to the corneal nerve damage. Pseudophakic bullous keratopathy (PBK) that results in the formation of fluid-filled bullae or blisters is commonly observed after the cataract surgery.

Corneal Edema: Diagnosis and Treatment

As early symptoms of corneal edema are similar to cataracts, it is necessary to undergo ocular evaluation for the correct diagnosis of corneal edema. The eye care specialist may conduct specular microscopy, ultrasound and optical pachymetry (measurement of corneal thickness) in order to confirm the diagnosis.

The treatment of corneal edema varies based on the exact cause of the condition. In case of condition caused by ill-fitting or over wear of contact lenses, the use of correct contact lenses is recommended. Similarly, corneal edema caused by increased eye pressure is treated by lowering the pressure. Corneal edema developed as a post-surgery complication can be improved by administering eye drops prescribed by the eye care practitioner. The doctor may prescribe antibiotics and anti-inflammatory eye drops for the infection related corneal edema.

In case, corneal swelling is restricted to the epithelial layer, it can be treated by using common salt solution. Over here, salt solution extracts the excess fluid accumulation in the cornea by osmosis. In severe cases, corneal transplant may be recommended as a treatment option. Proper eye care and eye exercise should be practiced to relieve the symptoms of corneal swelling.

If corneal edema is left untreated for a prolonged duration, then the symptoms may worsen to chronic eye conditions such as stromal edema and intercellular epithelial edema. Hence, in order to avoid such complications, it is always recommended to seek advice from a qualified eye specialist for early diagnosis and correct treatment of corneal edema.