Keratoconus is a bilateral, progressive, non inflammatory, degenerative disease characterized by paraxial stromal thinning and weakening of cornea resulting in a change in shape of cornea from normal round to a cone shape.

The cause is unknown, but the tendency to develop keratoconus is probably present from birth. The extensive research sources suggest that keratoconus likely arises from a number of different factors: genetic, environmental or cellular, any of which may form the trigger for the onset of the disease.

Keratoconus is thought to involve a defect in collagen, the tissue that makes up most of the cornea. Whatever the pathogenetical process, the damage caused by activity within the cornea results in a reduction in its thickness and biomechanical strength.

The earliest symptom is subtle blurring of vision. The patient becomes myopic but the error of refraction cannot be satisfactorily corrected with ordinary glasses owing to parabolic nature of the curvature which leads to irregular astigmatism.

The classic symptom of keratoconus is the perception of multiple 'ghost' images, known as monocular polyopia. The effect can worsen in low light conditions as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern.

There are various modalities of treatment currently advocated:

Contact lenses
In early stages of keratoconus, spectacles or soft contact lenses can suffice to correct for the mild astigmatism. But as the condition progresses, rigid gas-permeable lenses are required to attain satisfactory degree of visual acuity. RGP lenses provide a good level of visual correction, but do not arrest progression of the condition.

Scleral and semi-scleral lenses are larger diameter gas permeable (GP) lenses. The edges of such lenses rests on the sclera hence they are more comfortable.

Surgical options
Corneal collagen crosslinking with riboflavin
Corneal Collagen Crosslinking with Riboflavin also known as CXL, CCR, CCL and KXL is a treatment developed at the Technische Universität Dresden the early results of which indicate that it may be the first treatment available to actually stabilize the keratoconic process. The aims of the treatment are to increase the mechanical stability of the cornea and its resistance to enzymatic digestion, by inducing cross linkage between the corneal collagen fibres. Photochemical collagen crosslinking by riboflavin/UVA appears to provide a simple, safe and technically easy to perform outpatient surgical procedure.

The technique is performed as an outpatient procedure under topical anaesthesia (eye drops). As riboflavin does not penetrate the epithelium (corneal skin), this is removed using a blunt spatula (although some surgeons advocate the use of minor epithelial trauma only, as sufficient to allow riboflavin penetration into the corneal tissue. Riboflavin eye drops 0.1% are applied to the corneal surface five minutes prior to the procedure and then every five minutes during the procedure, which involves, exposing the corneal surface to ultraviolet A radiation (370nm) at a radiance of 3mW/ cm2 for 30 minutes. At this low energy level, UV wavelength and using this concentration of riboflavin, the technique has been shown to be safe with no endothelial damage provided the cornea is thicker than 400µm, with no loss of corneal transparency and no damage to deeper ocular structures.

Corneal ring segment inserts
A recent surgical alternative to corneal transplant is the insertion of intrastromal corneal ring segments. A small incision is made in the periphery of the cornea and two thin arcs of polymethyl methacrylate are slid between the layers of the stroma on either side of the pupil before the incision is closed. The segments push out against the curvature of the cornea, flattening the peak of the cone and returning it to a more natural shape, thus reducing or eliminating morphological irregularities and existing myopia and astigmatism. The procedure, carried out on an outpatient basis under local anaesthesia, offers the benefit of being reversible and even potentially exchangeable as it involves no removal of eye tissue.

In some cases, crosslinking may also be successfully combined with other treatment methods such as corneal ring segment inserts and Keraflex, a new refractive correction procedure. Corrective lenses may still be required after these treatments but with more normal prescriptions possible now, and these newer methods may have an important role in limiting deterioration of vision, increasing unaided/uncorrected vision and reducing the case for corneal transplantation.

Implantable contact lens/ ICL
Implantable contact lens also called as ICL is a type of Phakic Lens. Phakic intraocular lenses are specialized lenses made of plastic or silicone materials, which are implanted into the eye permanently to reduce a person’s dependence on glasses or contact lenses. They are called as Phakic lenses as they are implanted into the eye without removing the eye’s natural lens. The phakic lens is inserted through a small incision and placed just in front of or just behind the iris.

The lens is soft and tiny, much like the natural lens, but does not replace it. The ICL is specially shaped to correct myopia/ hypermetropia/ astigmatism. Toric ICL’s correct the cylindrical errors also thus providing a very sharp vision

Other Operative procedure
Few cases of keratoconus will progress to a point where vision correction is no longer possible. For such cases various surgical procedures are employed like corneal transplantation and DALK transplant.

Keratoconus services at our centre:
We, at our centre, provide all options of contact lenses available for keratoconus patients. C3R surgery with Phakic IOLs that provides a definitive treatment for vision improvement is also available at our centre with excellent results.