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Advanced Keratoconus: a Conical Cornea Disease

By Edited May 25, 2015 0 0
Advanced Keratoconus surgery
Credit: mRio via Flickr

This is how the eye looks after undergoing cornea transplant surgery. Note that the color of the eye doesn't change, only the scar from the eye replacement is visible.

Keratoconus is caused by a weakening of the cornea, which prevents its treatment with any type of laser. The correction with glasses is not entirely effective in these cases and not all patients with keratoconus are tolerant to the use of contact lenses, although they are way more effective than glasses due to their direct adaptation to the eyes.

What is keratoconus?

The word keratoconus is made out of two Greek words: kerato, meaning cornea, and konos, meaning cone. Keratoconus is a condition in which the normal shape of the cornea gets distorted, developing a cone-shaped deformation, altering and partially impairing the vision, gradually making it more and more blurred. This process depends on the patient's age, and the onset of symptoms. Usually when the patient is younger and the disease appears earlier, the onset of keratoconus progresses faster. It’s always bilateral and asymmetric.

What is the cause of keratoconus?

It may be due to congenital abnormalities, with different genetic severity according to the generations, or it may be caused by the weakening in the corneal tissue (such as when previous surgery or trauma has taken place). Keratoconus usually appears during the teens, associated with episodes of allergy. Rubbing the eyes can also help its chronic development.

How is keratoconus treated?

There are various forms of treatment depending on the severity and the status of the corneal progression process.

Treatment options may include the following as appropriate:

  • Glasses at the beginning of the disease
  • Contact lenses, when glasses are not enough
  • Intrastromal corneal ring segments: when the individual has intolerance towards contact lenses or when there are clear signs that the disease is progressing.
  • Cornea Transplant, in more advanced stages where the other options cannot offer any improvement. (Eg very advanced keratoconus, corneal scars, etc…)

In the early stages, the patient may wear glasses. As the disease progresses, the reduction ot the thickness and deformation of the cornea causes a highly irregular astigmatism that cannot be corrected with eyeglasses. In these cases, gas permeable rigid contact lenses are worn. While contact lenses improve the vision they do not stop the progression of keratoconus.

What are intrastromal rings?

This is a surgical treatment which implements two semicircular segments of varying thickness, 5 mm in diameter, made out of an acrylic material (Perspex CQ), which has been used for over 20 years in the manufacture of intraocular lenses. It is well tolerated by the body without any risk of rejection. It is the most modern and safe way to treat keratoconus in certain stages, but unfortunately at an advanced stage it poses a risk as the cornea layer can be too thin.

What is the surgical procedure?

The surgery implies the partial or total removal of the patient’s own corneal tissue and its replacement with a safe donor’s cornea. Depending on the extent of the area affected, the queratoplasty will be penetrating (all the cornea will be replaced until the point where the blood-irrigated tissue starts) or lamellar (only the central part is replaced, which decreases the likeliness of rejection). The surgery is performed in a surgery facility specially designed and complying with the ophthalmic surgical sterility standards to carry out the procedure. The anesthesia is local, ie only with drops. The procedure is painless and takes about 15 minutes. The use of antibiotic eye drops, anti-inflammatory drugs and lubricants improves the post-operative process and makes it more comfortable for the patient. Usually after three days the person can perform common tasks again.

What are the risks of surgery?

The risks are minimal, but like any surgery, infection is a possible complication. In this case, in addition to the treatment of the ocular infection itsel, it may require the removal of the implants.

After the surgery, when does the patient recover the vision?

The visual recovery is usually fast. The next day, the vision improves and stabilizes slowly by the third month. During this period, normal fluctuations in the vision are likely to occur. Particularly in the morning, the vision is usually better, and during the day it can become slightly more opaque. The patient may need to wear glasses or contact lenses to complement the visual correction. However, the quality of vision is usually better than before surgery even if the use of glasses or contact lenses is still required. It is important to know that the total recovery of the eye function and freedom for the patient to run or carry weights doesn’t come until one year later. This is due to the stromal layers (the transparent part of the cornea) not having blood vessels, making it more difficult for the scar to heal. The eye drops help in this process.

What is the prognosis?

The prognosis for patients who undergo a cornea transplant is really good. Because it’s not a highly invasive operation and it only requires the patient to rest from activities that increase the tension in the eye, it has very high success rates. Generally patients benefit from an improved vision for very long periods of their lives (even for always) with one single successful surgery.

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