WHAT IS KERATOCONUS?
Keratoconus is a disease of the cornea which causes thinning of the central portion of cornea. As this progresses the normal eye pressure causes distortion of the natural round shape of cornea and an irregular cone like bulge develops which causes vision impairment.
The poor quality of vision occurs due to distortion of image caused due to distorted corneal surface. This gives rise to image doubling, ghost images, shadows or flared images.
It does not lead to blindness but it can result in disabling vision in advanced stages.
WHAT CAUSES KERATOCONUS?
Recent studies have highlighted that it is caused by genetic as well as environmental factors. It has been reported that about 20 % of patients have an affected family member. Other genetic causes of Keratoconus include Downs syndrome, Ehler-Danlos Syndrome, Marfan’s Syndrome.
Keratoconus is often associated with Atopic diseases like Asthma, Hay fever, Atopic dermatitis.
Excessive and vigorous eye rubbing can break down the collagen fibers of cornea and result in Keratoconus.
It can be difficult to diagnose Keratoconus in early stages as the symptoms can be vague and overlapping. With advancement of disease there is frequent changes in spectacle prescription.
It is usually diagnosed with Opthalmoscopy, Retinoscopy, Slit Lamp examination and Topography. Corneal topographer is the most sensitive instrument to detect early Keratoconus as it creates computer generated colored maps of cornea.
Some other signs of Keratoconus identifiable on eye examination are :
Most patients with early Keratoconus will not have any obvious early signs with respect to cornea or a significant corneal thinning. Corneal topography in such cases becomes absolutely essential because it maps the front and back surface of cornea on a 3D background which highlights subtle abnormalities also.
Secondly any progression over time can be comprehensively documented using corneal topography.
Keratoconus is seen to occur in about 1 in 1700 population worldwide. With advent of technology and better screening modalities, the incidence could be as high as 1 in 500 persons. There is no Gender preponderance. People belonging to certain race could have a higher incidence.
SIGNS AND SYMPTOMS
A YOUNG PERSONS DISEASE
Onset of Keratoconus is usually between age 8 -45 years. The disease becomes apparent in early Adolescence and progresses as age advances. The disease is most aggressive in this age group and hence needs to be detected and treated early as it can have a significant impact on patient socially and economically.
BOTH EYES AFFECTED
Keratoconus in majority of cases affects both the eyes, although the extent of involvement of each eye could vary.
STAGES OF KERATOCONUS
Keratoconus progression varies in different patients of different age groups. Progression is seen to be more rapid if the age of onset is early. Progression continues till about 40 years of age and then tends to stabilize. So the most important time period is first 15-20 years after disease onset.
1. EARLY KERATOCONUS
Also known as Forme Fruste Keratoconus. This is a very early stage which can only be detected on Topography eye test. The patient himself has no symptoms related to Keratoconus. Progression is slow. Easily corrected with glasses or contact lenses.
2. MODERATE KERATOCONUS
At this stage the cornea starts to show corneal irregularities. It can be detected clinically on slit lamp as well. The quality of vision is affected and con be corrected using special RGP lenses. Treatment at this stage with corneal strengthening procedure is very effective.
3. ADVANCED KERATOCONUS
Significant corneal distortion is observed with a poor quality of vision along with other symptoms of Keratoconus. At this stage strengthening procedure becomes absolutely essential and RGP lenses can help to improve vision quality to some extent.
4. SEVERE KERATOCONUS
We find Dramatic corneal distortion and very significant corneal scarring and thinning. The vision is often non functional and not correctable with commonly used devices such as contact lenses. Scarring at the center of cornea warrants a corneal transplant.
KERATOCONUS, unlike many other diseases shows progression in early adolescence and then stabilizes as age approaches 40-50. Thus choosing the best treatment is not easy.
Keratoconus diagnosed at a later age tends to be less aggressive and also its treatment is less radical with good correction possible only with glasses or contact lenses.
Which modality of treatment is best for you will depend on your circumstances. Younger patients who are likely to show progression are likely to consider Crosslinking at an early stage whereas older patients with slow or no progression can often skip Crosslinking and get cured with spectacles or contact lenses.
However there is no known cure for Keratoconus or means of reversing damage done to cornea by Keratoconus.
Broadly treatment for Keratoconus can be divided into two steps. First is to halt progression by modalities such as Corneal Crosslinking, second is to correct vision using modalities such as Glasses, Contact Lenses, INTACS ring Segments, ICL etc.