original article

Our study reports on a cohort from the Indian subcontinent. To our knowledge this is the Þ rst report of its kind. This study like other studies from Europe shows that corneal collagen crosslinking with riboß avin is eff ective in stopping the progression of keratoconus by ’’freezing” the cornea.^[2,14,19] A good safety proÞ le has been documented.^[21] The postoperative change in the keratometry at the apex of the cone (K apex) showed a mean decrease of 2.68 at six months and continued towards reduction at 12 months.

The success of cross-linking treatment in keratoconus is not surprising, because a signiÞ cantly reduced tensile strength has been measured biomechanically ^[22] in keratoconus and a signiÞ cant increase in corneal rigidity has been measured in porcine and rabbit corneas treated by riboß avin/UVA using quantitative biomechanical stress strain measurements.^[16,17] Caporossi et al.,^[2] showed in human eyes that refractive results showed a reduction of about 2.5 D in the mean spherical equivalent, topographically conÞ rmed by the reduction in mean K. Results of surface aberrometric analysis showed improvement in morphologic symmetry with a signiÞ cant reduction in coma aberrations.^[2] In addition, Raiskup- Wolf et al.,^[19] who followed up patients up to six years and reported on a larger cohort of patients too concluded that the improvement in vision aft er cross-linking is caused by a decrease in astigmatism and corneal curvature as well as by topographical homogenization of the cornea as a result of the increased rigidity in the cross-linked cornea. In addition, the Þ tt ing of contact lenses is improved.^[19]

This leads to an increase in both, the unaided visual acuity and BCVA, not only through astigmatism improvement (K readings reduction) but also in terms of corneal symmetry indices improvement aft er cross-linking. Another possible explanation of cross-linking success, especially concerning keratoconus stabilization, is the new more compact collagen lamellar structure aft er corneal cross-linking as demonstrated in recent studies by Wollensak^[23] and Mazzott a.^[24] It is important to note that in this cohort of patients we did not come acrossany complications.

The importance of cross-linking lies in the fact that it is a low-invasive, outpatient procedure. It achieves a result so far not off ered by any other modality of treatment. This includes conservative approaches like contact lenses and surgical options like intracorneal rings, and keratoplasty. Keratoplasty is oft en the only choice in many patients. In epidemiological studies up to 21% of patients have ended up needing keratoplasty

for visual rehabilitation.^[25,26] The problems for a treatment like keratoplasty for keratoconus in a country like India are compounded by lack of adequate tissue availability. Also, it is the Þ rst treatment option for patients with keratoconus that off ers a possibility of mild regression in the condition. Thus cross linking helps in various ways: improves vision, helps regression of disease, stabilizes future progression, and thus probably delays or avoids keratoplasty in a given patient. It
would require a longer study to adequately validate these comments.

It thus also has a signiÞ cant psychosocial value. Keratoconus being a disease of the young causes significant loss of productivity and has a disproportionate impact on the quality of life. Any procedure that can improve the quality of life in a given disease deserves a close look. This study though the Þ rst from the Indian subcontinent has several limitations. Being retrospective in nature the data bias is a possibility. However, looking at various international studies published earlier
this may not be a major deÞ cit. The numbers in our analysis are limited. A larger multicentric study for collagen crosslinking in keratoconus would be needed to derive stronger conclusions.

Raiskup-Wolf et al.,^[19] had two patients in their series who needed repeat treatment with cross-linking. However, these patients had acute exacerbation of neurodermatitis. This study also reported the longest series of patients followed from three to six years aft er treatment. Thus, it is important to cross-link corneas with progressive keratoconus as early as possible. In the future, we may be able to further improve vision by combining the cross-linking procedure with procedures such as intracorneal ring implantation.^[27] and topography-guided photorefractive keratectomy.