Cornea is the transparent front surface of the eye. Normally, when looking straight on at the eye, you look right through the cornea and see the coloured iris and black pupil of the eye.
The cornea is avascular i.e. contains no blood vessels to nourish or protect it against infection, unlike other tissues in the body. Instead, it receives its nourishment from the tears and aqueous humour which is present in the anterior chamber. It is mainly composed of cells and proteins.
There are a lot of corneal disorders and diseases seen in routine practice. Enumerating below are a few of the common ones:
Refractive errors
If the cornea is flatter than normal or the eye is short, rays of light are focused behind the retina and causes hyperopia or farsightedness where close objects appear blurred.
Astigmatism is a condition in which the uneven curvature of the cornea blurs and distorts both distant and near objects. The cornea is more curved in one direction than in the other. This causes the rays of light to focus on two separate areas of the retina, distorting the visual image.
Refractive errors are usually corrected by eye glasses or contact lenses. Although these are safe and effective methods for treating refractive errors, refractive surgeries are becoming an increasingly popular option.
Allergies
Allergies affecting the eye are relatively common. They are most commonly related to pollen and dust in the air. They are usually immediate or delayed hypersensitivity reactions. Symptoms can include redness, itching, and burning, tearing, stinging and watery discharge. An increasing number of eye allergy cases are related to medications and contact lens wear. Also, animal hair and certain cosmetics, such as mascara, face creams and eyebrow pencil, can cause allergies that affect the eye. Touching or rubbing the eyes after handling nail polish, soaps, or chemicals may cause an allergic reaction. Some people have sensitivity to lip gloss and eye makeup. Mild forms of these allergic disorders are usually restricted to the conjunctiva. However, moderate and severe allergies usually cause affection of the cornea and may lead to decrease vision. These allergies can be treated effectively with topical medications. Hence, every person who gets frequent episodes of redness, watering and itching should consult an ophthalmologist and seek advice.
Conjunctivitis (red / pink eye)
Conjunctiva is a translucent mucous membrane which lines the posterior surface of the eyelids and anterior aspect of the eyeball. A group of diseases that cause swelling, itching, burning and redness of the conjunctiva are termed as conjunctivitis. It is an inflammation of the conjunctiva associated with a discharge which may be watery, mucoid, mucopurulent or purulent. It can spread from one person to another if proper precautions are not taken. It can be caused by a bacterial or viral infection, allergy, environmental irritants, a contact lens product, eye drops or eye ointments. It is usually painless in the beginning and does not affect vision. But in some forms of conjunctivitis, if the infection is severe, it can cause corneal inflammation and loss of vision. Treatment of conjunctivitis is usually with eye drops. However a consultation with an ophthalmologist is a must to make sure that there is no corneal involvement.
Infections
A breach in the normal epithelial surface of the cornea associated with necrosis of surrounding corneal tissue is termed as corneal ulceration. Two main factors are responsible in the production of a corneal ulcer: damage to corneal epithelium and infection of the eroded area. They usually cause pain, redness, watering, discharge, photophobia i.e. intolerance to light and blurred vision. It can be caused by bacteria, fungi, viruses, acanthamoeba and many other organisms. They cause painful inflammation called keratitis. These infections can reduce visual clarity, produce corneal discharge and perhaps erode the cornea. Corneal infections can also lead to corneal scarring, which can impair vision and may require a corneal transplant. As a general rule, the deeper the corneal infection, the more severe the symptoms and complications. It should be noted that corneal infections, although relatively infrequent, are the most serious complication of contact lens wear. Minor corneal infections are commonly treated with anti-bacterial or anti-fungal eye drops. If the problem is severe, it may require surgical intervention. Frequent visits to an eye care professional may be necessary for several months to eliminate the problem.
