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Using cone location as a discriminant of visual outcomes after simultaneous topography-guided photorefractive keratectomy and collagen cross-linking

Poster Details

First Author: M.Nicholson INDIA

Co Author(s):    R. Shetty   B. Shetty   A. Roy        

Abstract Details


To evaluate the effect of location of the keratoconus (KC) cone on change in corneal aberrations and biomechanics after combined topography-guided photorefractive keratectomy (T-PRK) and collagen crosslinking (CXL)


Tertiary eye care center and Teaching institute in South India


The study enrolled 38 eyes of 38 patients. T-PRK was performed with a customized T-PRK platform and accelerated crosslinking (CXL) was performed with riboflavin A and conventional intensity (3mW/cm2) ultraviolet light. Outcome parameters including uncorrected (UCVA) and best (BCVA) corrected visual acuity, corneal topography and biomechanics (corneal hysteresis [CH] and corneal resistance factor [CRF] ), and corneal aberrations were assessed before and at 12 months after the procedure. Eyes that had the cone located in the central 2 mm zone were classified as centered (C, n = 26) and the remaining as decentered (DC, n = 12)


UCVA and BCVA improved in both groups, more in C (UCVA: p=0.01; BCVA: p<0.0001) than in DC group (UCVA: p=0.03; BCVA: p=0.03). Similarly, sphere, cylinder, spherical equivalent, steep and flat K improved post-operatively more in C than in DC group and was statistically significant change (p<0.05). Total corneal aberrations root mean square, defocus and spherical aberration showed statistically significant change (p<0.05) after the treatment in C group. In DC group, total RMS was the only aberration variable with statistically change. Interestingly, corneal biomechanics (CH) appeared to improve after treatment more in the DC (p =0.03) than in C group (p =0.71). CRF also improve after treatment but the change was not statically significant (p>0.05)


In simultaneous T-PRK and CXL treatment, C and DC appeared to affect the outcome of the surgery and C group may provide better visual and biomechanical outcomes. It may be necessary to factor the location of the cone in planning of newer treatment protocols to obtain similar outcomes in both groups FINANCIAL INTEREST: NONE

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