Topographical corneal changes in keratoconus patients treated with collagen cross linking: A before and after intervention study with one year follow up
Abstract
Keratoconus is a progressive asymmetrical, bilateral, non-inflammatory corneal ectasia casing refractive errors. Various techniques are used to manage these cases. Corneal collagen cross linking (accelerated method) is one of such technique. A hospital based follow up study was conducted on 30 Keratoconus patients to find out the effect of corneal collagen cross linking (accelerated method) on refractive variables of Keratoconus patients. After this procedure, there was improvement in Best Corrected Visual Acuity 0.382, decrease in Cylindrical Refractive Power at 0.73%, decrease in Spherical Refractive Power at 19.32%, decrease in Spherical Equivalent at -6.15%, decrease KMAX of 0.712%, decline Mean Irregularity of 9.09%, Corneal thickness (Thinnest Point) decreased by 3.48%, Anterior Best Fitted Sphere Values decreased by 1.49% and Posterior Best Fitted Sphere decreased by 1.16%. It can be concluded from this present study that there is a significant improvement in topographic corneal changes and refractive results in patients with corneal ectasia after C3R. These results can illustrate the efficacy and usage of CXL for keratoconus among Indian patients. However, more studies and clinical trials are required to establish definite conclusions on the efficacy of C3R.
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Introduction
Keratoconus is a progressive asymmetrical, bilateral, non-inflammatory corneal ectasia which is characterized by corneal thinning protrusion of central cornea leading to decreased vision and irregular astigmatism. Keratoconic eyes have altered corneal biomechanical profile and appear to be more elastic and less rigid than normal eyes. Its incidence is 54 in 100000. 1 It is aggravated by puberty, pregnancy, vernal kerato-conjunctivitis and lid rubbing.
Corneal cross linking is a recently introduced treatment for addressing progressive keratoconus. It is a minimally invasive procedure and the only option that halts or slows the progression of disease. Riboflavin and ultraviolet-A rays2,3 induce crosslinking through photopolymerization of collagen mediated by reactive oxygen species. These induce generation of stiffer collagen fibrils and a rearrangement of corneal lamellae within the matrix and thus increase corneal biomechanical rigidity and biomechanical resistance by 300 percent.
Therefore, C3R could potentially reduce the need for corneal grafting in patients with keratoconus which occurs generally in young population.
In India, very few studies have been done on collagen cross linking and its long-term outcomes. It achieves a result not so far achieved by any other modality of treatment. 4
Conclusion
It can be concluded from this present study that the procedure of collagen cross linking with riboflavin and UVA radiation definitely has beneficial effects on improving corneal strength and stability, thereby playing a significant role in halting the further progression of keratoconus. All the variables under study showed improvement or status quo in long term. Moreover post-operative complications were minimal and tolerable, Hence making the procedure worthy of consideration as a first line of management in Keratoconic population. However more such studies are required for establishing the efficacy and safety of C3R in general use.