Keratoconus (KC) is a progressive, bilateral, but usually asymmetrical ecstatic corneal disease, characterized by progressive corneal protrusion and thinning, that leads to corneal surface distortion. The reported incidence in the general population varies from 1.3 to 25 per 100,000 per year across different populations, with a prevalence of 8.8–229 per 100,000. Onset typically is at puberty with progression of the disease for 10–20 years after which it tends to stabilize. It occurs in all racial groups and equally affects males and females.

Management of keratoconus depends on its severity and the extent of irregular astigmatism. Mild cases are correctable with spectacles and soft toric contact lenses. However, with the more progressive disease, the cornea becomes more irregular and rigid gas permeable lenses are required. In 15–20% of keratoconic patient’s surgery, typically keratoplasty becomes necessary, as a result of contact lens intolerance, corneal scarring and thinning.

Lamellar keratoplasty with augmented thickness:

The recent years have brought about a sea change in the field of corneal transplantation with penetrating keratoplasty being phased to newer lamellar keratoplasty techniques. In keratoconus, the aim of surgery is to augment a thin and steep cornea, and this can be achieved by using a thick lamellar donor of normal curvature, thus tectonically strengthening the cornea (which reduces irregular astigmatism and subsequent ectasia) and reducing corneal steepness (and concomitant high myopia). This is achieved by performing more superficial lamellar dissection of the recipient bed and obtaining a thicker donor lamella. Thanks to the advent of new surgical devices such as advanced microkeratome instrumentation, excimer laser, and femtosecond- laser, the results of lamellar techniques have been encouraging, with rapid visual rehabilitation and vastly reduced risk of immune-mediated transplant rejection.

            To simplify and standardize LK, Excimer laser ablation has been used to prepare the recipient bed, with encouraging results. Excimer laser lamellar keratoplasty (ELLK) of augmented thickness is a procedure in which a deep plano excimer laser ablation is performed on the host cornea and a donor lamellar button, with or without an excimer laser refractive ablation on the posterior surface, is sutured into the recipient bed.17 According to Serdarevic et al18 the overriding advantage of using an ELLK is the laser’s ability to remove tissue with a microscopic precision that is unattainable with other procedures. They assert that the laser does not interfere with wound-healing processes, including cell migration and proliferation, and production of new tissue. In 1992, Kubota et al19 examined the depth of ablation of the recipient bed with different counts of oscillations of an excimer laser beam to determine the correlation between planned and real depth. Their results showed that an excimer laser achieved a precise cut in terms of diameter, site, and in particular thickness, indicating its utility in reproducible corneal photo ablation in LK.

Recently, a distinct layer of corneal collagen, the Dua’s layer has been described, beyond the last row of keratocytes, which is thin but tough, and seems to provide a cleavage plane during the DM baring procedure.

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