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B.A. Ameline, M.G. Puech, A. El Maftouhi, E.A. Brasnu, L. Laroche; Thin Corneas Undergoing Lasik 4 Years Follow Up Clinical and OCT 3 Analysis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4378.
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Purpose: The aim of this study was to evaluate the stability of thin corneas after Lasik procedures. Methods: We retrospectively examined 12 eyes of 7 patients, who underwent a Lasik procedure, from March 1998 to December 1999, even though their ultrasonic corneal pachymetry ranged from 465 to 505µ (Mean pachymetry 495.5 + 10.8µ). Their mean ametropia was –6.55 + 3.14D. The maximum correction was –9 D. Corneal anterior topographies showed no sign of keratoconus (Rabinowitz criteria) The flap was created with an ALKe® (7 eyes) or a Hansatome® (5 eyes), Excimer ablation was performed with a Technolas 217c. Four years later we studied their refraction and its stability, their keratometry by TMS2® and Orbscan® and we performed for each eye an OCT3 examination including the optical measurement of their corneal pachymetry, flap thickness and residual posterior wall. Results: At the final examination 45% of the eyes were within 0.5 D of emetropia and 82% within 1.5 D. The myopic shift between the 6 month and four years end points was 0.62+0.63D. No eye lost more than one line of best corrected visual acuity. No corneal ectasia was detectable with the Orbscan®. Optical corneal pachymetry was comparable to ultrasonic measurement (+6µ), whereas Orbscan® underestimated the total pachymetry by 49µ in average. Optical measurement of the flap thickness ranged from 135 to 218µ (M=169+25µ). Posterior wall was 264+44µ in average, but ranged from 203 to 334µ. Conclusions: OCT3 examination has allowed a retrospective in vivo analysis of the flap thickness and residual stroma. None of our patients showed any sign of corneal ectasia during a four years follow up even though the posterior wall could be as thin as 203µ.
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