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Munira Hussain, Jonathan Greene, Nilesh Raval, Matthew Brumm, Shahzad Mian, Roni Shtein; In vivo corneal confocal microscopy (IVCM) and ocular surface assessments in patients with mechanical microkeratome vs femtosecond laser-assisted LASIK. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2591. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare subbasal corneal nerve density by in vivo confocal microscopy (IVCM) and clinical outcomes 7 to 9 years after laser in situ keratomileusis (LASIK) with flap creation by microkeratome (MK) or femtosecond laser (FL)
Prospective, comparative, IRB approved study of 46 eyes which underwent LASIK, with MK (n=20) and FL (n=26), average of 8 years ago. Sub-basal corneal nerve density by IVCM, tear production by Schirmer test, corneal fluorescein and conjunctival lissamine green staining, tear break up time (TBUT), tear osmolarity, central corneal thickness by ultrasound pachymetry, corneal sensation using Cochet-Bonnet esthesiometry and Ocular Surface Disease Index (OSDI) were assessed in all subjects. Two-tailed t-tests were performed to compare subjects with MK and FL.
There were more females than males in the MK group (90% vs 46%, p=0.029) and there was a trend of younger patients in the MK vs FL group (50 yrs vs 55 yrs, p=0.069). Patients in the FL group had decreased corneal sub-basal nerve density (7.96 mm/mm2 vs 11.40 mm/mm2, p=0.011) and increased corneal sensitivity (5.5 mm vs 4.4 mm, p=0.013) compared to the MK group. There was no significant correlation between corneal nerve density and corneal sensitivity (r=-0.23). Patients who underwent LASIK with FL had significantly thinner corneas (486 µm vs 537 µm, p=0.0005) than those who had MK LASIK. There were no significant differences in OSDI scores (p=0.097), tear osmolarity (p=0.292), tear production (p=0.208), TBUT (p=0.081), lissamine (p=0.532) or fluorescein staining (p=0.853) between the 2 groups.
Our preliminary results indicate that there may not be long-term differences in standard measures of ocular surface health (tear osmolarity, Schirmer, ocular surface stain, OSDI) between patients who had the two techniques of LASIK flap creation. There do appear to be differences in subbasal nerve density, in corneal thickness and in corneal sensitivity. Further research is needed to understand why these differences are observed.
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