1. 1 P.O. dei Pellegrini; A.S.L. Napoli 1Centro 2 Dipartimento di Oftalmologia, Seconda Università degli Studi Napoli Scheimpflug topography, Scanning-Slit topography and Anterior Segment Oct in patients with keratoconus Luigi Capasso, MD 1 ; M Lanza, MD 2 ; A Tortori, MD 1 ; C Buono, MD 1 ;L Gifuni, MD 1 ;F Amoroso 1 ; N Rosa, MD 2 Authors have no financial interest.

2. BACKGROUND Accurate measurement of corneal thickness is crucial in the monitoring ectatic dystrophies in the preoperative assessment in the planning of surgical procedures such as intrastromal corneal ring segment implantation, corneal collagen cross-linking with riboflavin (C3-R) and deep lamellar keratoplasty.

3. PURPOSE To compare the measurements of the thinnest corneal point (TCP) with three different devices Orbscan II Computerised Topography, Visante Optical Coherence Tomography (OCT) and Pentacam in patients with keratoconus (KC)

4. prospective, clinical study, 71 eyes of 37 consecutive patients with keratoconus. MATERIAL AND METHODS 25 males and 12 females Keratoconus was diagnosed if there was scissoring reflex on retinoscopy and central or paracentral steepening of the cornea on computerized topography with at least one of the following slit lamp findings of keratoconus: central or paracentral thinning, anterior bulging or conicity, Fleisher’s ring. No patient presented Descemet’s breaks or apical scar and subepithelial fibrosis. We studied a spectrum of keratoconic eyes of different severity according to the Amsler scale automatically provided by the Pentacam as follows: early (Amsler 1) 23 eyes; moderate (Amsler 2) 26 eyes; and severe (Amsler 3-4) 22 eyes. Age range: 12 – 29 years (mean= 22.01 ± 4.53) years

5. MATERIAL AND METHODS Measurements were done sequentially by two different operators using Orbscan II computerised topography (Bausch and Lomb Inc), Visante anterior segment OCT (Carl Zeiss) and Pentacam (Oculus). The software of the three devices automatically generates a pachimetry map. All measurements were taken at the same day time, between 1 PM and 5 PM.

6. RESULTS The TCP measured with the Orbscan II and Visante OCT was 424.74 ± 54.91 μm (mean ± SD) and 461 ± 38.48 μm respectively, with a statistically significant difference (p<0.001).

7. RESULTS The TCP measured with the Pentacam and Visante OCT was 461.94 ± 38.94 μm (mean ± SD) and 461 ± 38.48 μm respectively, with no statistically significant difference (p>0.1).

8. RESULTS The TCP measured with the Orbscan II and Pentacam was 424.74 ± 54.91 μm (mean ± SD) and 461.94 ± 38.94 μm respectively, with a statistically significant difference (p<0.001).

9. Discrepancies between the three devices were present, but Pentacam and Visante OCT, showing no significant differences, seem to be more reliable in measuring the corneal thinnest point in patients with keratoconus compared to Orbscan II. CONCLUSIONS

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