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Does the rate of dehydration of the stroma during LASIK depend on the start hydration and type of laser used?

Session Details

Session Title: Corneal Femtosecond

Session Date/Time: Monday 07/10/2013 | 14:30-16:30

Paper Time: 16:20

Venue: Elicium 1 (First Floor)

First Author: : S.Patel SPAIN

Co Author(s): :    J. Alio               Pini

Abstract Details


To determine if the stromal dehydration during photoablation in vivo was associated with, i) initial hydration of the stromal bed and ii) type of excimer laser delivery system according to pulse rate.


Vissum/Institute of Ophthalmology, Alicante, Spain


Measurement of refractive index (RI) of the stroma is a non-destructive indirect estimate of hydration (H). H can be reliably estimated according to the Fatt-Harris equation (F-Heq). RI was measured after lifting the flap, just before (R) and immediately after routine uncomplicated LASIK in consecutive randomised cases using a digital surgical hydrometer (VCH-1) based on the principles of Abbé refractometry. The duration of the photoablation was timed (x, secs). Two excimer lasers were investigated A) Technolas 217, stated pulse rate 100Hz (Bausch & Lomb), B) Esiris, stated pulse rate 200Hz (Schwind). In all cases, flap was created using mechanical microkeratome (Moria).


Change in RI (?R) was significantly correlated with R and x. Multiple linear regression revealed, A) ?R = 0.447-0.321R +2.09 x10 -4 x, (r=0.573, n=31, F=7.584, p=0.002) B) ?R = 0.339-0.241R +8.85 x10 -5 x, (r=0.446, n=174, F=21.381, p=<0.001). Converting RI to H using F-Heq, over the range of RI values, the rate of tissue dehydration was 2.36 times greater using A) compared with B).


Stromal dehydration during LASIK depends on several factors including initial hydration, duration of treatment and type of laser according to pulse rate of eximer laser delivery system. Less dehydration is associated with faster treatment and higher pulse rate systems.

Financial Interest:

... receives non-monetary benefits from a company producing, developing or supplying the product or procedure presented., ... research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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