Keratoconus is an ectatic corneal degenerative disorder in which the cornea begins to weaken up. “It further starts thinning and steepening (bending) causing visual disturbances, but not blindness,” said Dr Sridevi Haldar, Ophthalmologist/Eye Surgeon, Ortho Vision Clinic, Noida.
The expert added that as the name itself suggests, the spherical cornea in Keratoconus becomes conical in shape, hence the name ‘keratoconus’ – (kerato -meaning cornea and conus-meaning conical). “The clear transparent cornea focuses the light beam onto the retina. Any anomaly in its shape cause visual disturbances,” she explained.
What causes keratoconus?
It generally starts around adolescence and progresses till 35-40 years of age. Researchers have not been able to discern the exact cause of the disease, although a number of risk factors associated have been fairly identified.
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Major risk factors include childhood eye allergies like VKC (vernal keratoconjunctivitis), intense eye rubbing, long-term use of steroid eye drops, and sometimes genetic components as well.
“These patterns lead to progressive steepening or bending of the cornea and the central corneal thinning followed by abrupt rupture of Bowman’s membrane layer of the cornea. This leads to acute hydrops leaving behind acentral corneal scar drastically reducing the vision,” she told indianexpress.com.
Any cylindrical power >1.25D should be thoroughly evaluated for early detection of this disease.
If one is frequently changing glasses and finding themselves not quite comfortable with the quality of vision, then keratoconus may be the case.
Increased cylindrical power can also be a sign of keratoconus.
Sudden blurring of vision during pregnancy may also occur owing to hormonal effects. This may also sometimes lead to keratoconus.
“Management of keratoconus depends on the stage of the disease. In the early stages of keratoconus, the refractive error can be corrected by glasses but in the advanced stages vision may not be very clear with them,” said Dr Haldar.
That is when, she said, one might need special contact lenses called rigid/hard contact lens. These lenses are available in various types, depending upon the extent to which cornea is steepened:
• RGP(rigid gas permeable lenses)
• Miniscleral lenses
• Rose k lenses
• Scleral lenses.
Corneal collagen cross-linking(C3R)
• Corneal cross-linking is a procedure that can be done in mild-moderate cases of keratoconus with documented evidence of progression over a year (increase in steepening by 1D)
• This involves treating the cornea with Riboflavin eyedrops for 20-30 minutes (priming procedure) which is followed by UVA radiation beam exposure for 10-30 minutes in order to fortify and strengthen the cornea so that it does not bend further.
• In advanced asymmetric cones (as seen on corneal topography), intacs or intracorneal segments are placed in the cornea to regularise the shape of the cone so that contact lenses would fit better and visual quality is enhanced. They do not correct the existing refractive error completely but only modify the shape of the cornea.
Corneal transplantation (keratoplasty)
• In advanced keratoconus, such as post hydrops scarring where Bowman’s membrane layer of cornea is already ruptured due to too much thinning of cornea leaving behind a scar in centre of cornea thus obstructing the visual axis
• Cornea surgeons may perform a partial thickness or a full-thickness corneal graft to replace the scarred cornea with a transparent cornea of the donor.
• The donor corneal graft is sutured to host corneal rim with 16-20 fine sutures which are subsequently removed after 8-9 months till the time donor cornea is fully integrated with host rim. However, one can start doing routine activities just after a week.
These are the best available options for keratoconus with a few modifications in every procedure to maximize the visual outcome in our patients.