Corneal disorders and cornea treatment in Delhi

The eye is like a camera in which lenses focus the picture on a light-sensitive film. In the human eye, the transparent cornea and lens focus light on the retina, which changes it into electrical signals. These signals are transmitted to the brain by the optic nerve and perceived as images.

The cornea is the front transparent window of the eye and forms the outermost one-sixth of the eyeball. It is lamellar in nature, like plywood, and is made up of five layers, each with a definite function. To be effective, it must remain transparent.

Cornea

Freezing, heating, molding, lathing, tattooing, excising, incising, and transplanting are all means by which the delicate cornea has been altered for optical, therapeutic, and cosmetic purposes. Because the cornea has no blood vessels, much of its oxygen comes from atmospheric oxygen dissolved in the tear film.

When the eyelids are closed, oxygen enters the cornea from superficial conjunctival vessels. Nutrients pass into it by diffusion, and carbon dioxide and waste products are removed across the tear film. Any deficiency of the tear film can therefore affect the cornea.

The abundant nerve supply of the cornea makes it one of the most sensitive parts of the body. It acts as an excellent watchdog for foreign material entering the eye. Dirt or specks may produce scratching or knife-cutting sensations that the corneal nerves transmit to the brain.

If the cornea loses this sensitivity because of injury or disease, it loses part of its protective function. Foreign bodies may embed in the cornea. A foreign body on the cornea needs urgent attention by an ophthalmologist. One should not attempt to remove it by rubbing the eye.

Cornea injuries

A twig, piece of paper, or fingernail can produce corneal abrasions. If not attended to immediately, secondary infection can occur and may lead to vision-threatening complications.

Contact lenses can also produce an irritable eye from a corneal abrasion. Until an eye specialist can be consulted, the contact lens should be removed and the eye protected.

Injuries from sharp or blunt objects require urgent attention from your ophthalmologist, especially to rule out corneal injuries that can threaten sight.

Acid or alkaline solutions splashed into the eye may be sight-threatening. Symptoms such as pain, redness, watering, and light sensitivity occur immediately after exposure and may be severe.

Chemicals in the eye need to be thoroughly washed out immediately with water. Thereafter, urgent consultation with an eye specialist is necessary.

Inflammation of the cornea, or keratitis, may be secondary to conjunctivitis, blepharitis, or injury. Keratitis is characterised by a painful red eye, sensitivity to light, and an occasional scratching sensation when blinking.

An ulcer may develop after a bacterial, viral, fungal, or other infectious organism invades the outer layer of the cornea. Herpes simplex can invade the cornea after injury and produce keratitis. Herpes zoster may also produce inflammation, especially if the skin of the nose is involved.

Ulcer in the cornea

A marginal ulcer is a corneal infection near the outer edge of the cornea. Central corneal ulcers caused by bacteria, viruses, or fungi can be severe and may even cause loss of the eye. This condition requires immediate attention from an ophthalmologist.

With intensive medical treatment, the infection can be brought under control. Sometimes surgical intervention is required. After the infection is eliminated, residual scarring may require corneal transplantation for restoration of vision.

This grayish, elevated growth of elastic and connective tissue containing blood vessels invades and grows over the cornea. It may result from irritation caused by wind, heat of the sun, dust, or smoke.

If a pterygium grows over the centre of the cornea, sight may be impaired or even lost. Before this occurs, the pterygium may need to be removed surgically.

Conjunctival autografting

At our eye clinic in East Delhi, pterygium is removed by a specialised technique called conjunctival autografting. The pterygium is excised and a conjunctival graft taken from a healthy part of the same eye is used to cover the defect.

This technique helps prevent recurrence that may occur after conventional pterygium removal without grafting. Some people confuse a cataract with a pterygium by calling a cataract a skin growing over the eye. A cataract, however, is clouding of the lens inside the eyeball.

Dystrophies or degenerative aging processes may develop in the cornea and interfere with vision. They are slowly progressive, non-inflammatory, and usually affect or involve both eyes. They may produce haziness or cloudiness of the cornea.

If vision is markedly impaired, contact lenses may be prescribed to improve it. If they do not help, a corneal transplantation may be performed to restore useful sight.

Dry eye syndrome is a leading cause of ocular discomfort affecting millions of people. Dry eye conditions are a spectrum of disorders with varied causes, ranging from mild eyestrain to very severe dry eyes with sight-threatening complications.

Although the typical patient with dry eyes is elderly or has an autoimmune disease, increasing numbers of younger patients who work with computers also experience dry eyes.

Dry eye

Dry eye can be aggravated by pollution, dry weather, decreased ambient humidity from air conditioning or indoor heaters, abnormalities in tear-film components, ocular or systemic diseases, and various drugs.

Dry eye syndrome is usually treated with tear supplements and lubricants. If these do not help, microscopic plugs, temporary or permanent, may be inserted to conserve tears and prevent them from draining away. In severe cases, surgical intervention may be essential.

Normally, the cornea is nearly spherical, allowing light to focus clearly on the retina. In keratoconus, the cornea begins to thin and the normal pressure of the eye makes it bulge forward into a cone shape.

As the cornea becomes more cone-shaped, vision blurs and becomes distorted due to a high degree of astigmatism. Initially, spectacles may correct vision, but as the condition progresses and the cornea becomes more irregular, spectacles become less effective.

Contact lenses

Contact lenses can provide better vision and help retard the progress of the disorder. A rigid gas-permeable or semi-soft lens must be used so it can hold its shape; a soft lens may mould to the existing cornea and not fully correct the problem.

Sometimes a patient is fitted with soft lenses for comfort, over which semi-soft lenses are fitted in a piggy-back arrangement. Fitting contact lenses for keratoconus requires expertise. Well-fitting lenses can dramatically improve vision and quality of life.

Excessive pressure from a poorly fitting lens on the cone apex can cause permanent scarring. Regular follow-up visits are important so corneal changes can be assessed and the lens design updated. Rarely, severe scarring requires a corneal graft.

Corneal collagen cross-linking with riboflavin

C3R, or corneal collagen cross-linking with riboflavin, is a treatment approach intended to increase the mechanical stability of corneal tissue. The aim is to create additional chemical bonds inside the corneal stroma through localised photopolymerisation.

Current indications include corneal ectasia disorders such as keratoconus and pellucid marginal degeneration, iatrogenic keratectasia after refractive lamellar surgery, and corneal melting that does not respond to conventional therapy.

Corneal transplantation, or keratoplasty, is an operation designed to correct blindness resulting from corneal disease. When the cornea is affected by degenerative change, infection, or injury, scar tissue may form during healing.

If the scar involves the centre or the entire cornea, vision may be impaired. Contact lenses rather than spectacles may partially improve vision, but they are often ineffective and a corneal transplant may be required. Corneal tissue from a donor is transplanted into the eye of a living patient blinded by a corneal scar or disease.

The only tissue used in the transplant is the cornea; the whole eyeball is not transplanted. The cornea is like the clear crystal of a watch: if it is cloudy, the face cannot be seen clearly, and replacing the crystal can restore clarity.

A corneal transplantation, like a cataract operation, is usually performed under local anaesthesia. General anaesthesia may be used for children and apprehensive or nervous patients. The operation is painless and takes about one hour to perform.

The diseased, cloudy cornea is removed from the recipient's eye using a special blade and replaced by a new clear cornea, or graft, from a donor's eye. Earlier, the entire thickness of the cornea was transplanted through penetrating keratoplasty.

Today, depending on the extent, location, and type of corneal disorder, surgeons can selectively transplant either the front part through anterior lamellar keratoplasty or the back portion through endothelial lamellar keratoplasty.

Cornea transplant treatment

The new cornea is sutured into place. The number of sutures depends on the size of the graft. If the operation is successful and the graft remains clear, the patient should see well again, provided the lens and retina behind the cloudy cornea are normal.

The patient is usually hospitalised for one day and requires rest for the next month, although returning to light work may be possible. Frequent follow-ups are required over the following six months to one year.

In favourable subjects, the rate of success of corneal transplantation may be as high as 60%, with good final visual acuity with glasses. In unfavourable subjects, the rate may be around 10% to 20%.

Each patient is evaluated individually before definite results can be predicted. Important factors that influence the final result include:

• The basic corneal disease, as some types respond better than others.
• The condition of the donor's cornea.
• Surgical technique and skill.
• The healing ability of the recipient cornea.
• Sensitivity reactions between donor and recipient cornea that may lead to rejection.

Lamellar keratoplasty

The advantages of lamellar keratoplasty, a newer group of techniques, include better visual outcomes, quicker rehabilitation, and lower rates of transplant rejection.

A corneal transplantation will not help every blind person see again. It restores vision only in eyes partially blinded by corneal disease; some vision must be present before transplantation is considered.