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In vivo Brillouin spectroscopy pre and post-LASIK

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Session Details

Session Title: Corneal Biomechanics

Session Date/Time: Monday 09/10/2017 | 08:00-10:30

Paper Time: 10:10

Venue: Room 2.1

First Author: : T.G.Seiler SWITZERLAND

Co Author(s): :    P. Shao   E. Amira   T. Seiler   S. Yun           

Abstract Details


Iatrogenic keratectasia is a rare (1 out of 3000) complication of LASIK and SMILE due to further weakening of a preoperatively weak cornea. Risk-parameters are detected today only by shape anomalies of the cornea. Brillouin spectroscopy can non-invasively measure biomechanical constants of tissue like the cornea. In this paper, the first clinically measured Brillouin-shifts of corneas pre- and post-LASIK are presented.


Institute of Refractive and Ophthalmic Surgery (IROC), Zürich, Switzerland and Wellman Center for Photomedicine, Harvard Medical School, Boston, USA


Brillouin-shift measurements were performed using a Brillouin-microscope (Brillouin optical scanning system, BOSS, Intelon Optics, Boston). In brief, the BOSS is mounted on a slitlamp table and the cornea is measured in a sitting position. Although in the majority of the patients a Brillouin-shift map was taken, here we present only the central readings. In this longitudinal study, patients were included receiving uncomplicated femtosecond-LASIK (refractive range +1.5D to -7.5D). The measurements were taken immediately preoperatively, at 1 day and at 1 month postoperatively.


The reproducibility of the measurement (3 different days, same eye and same operator) was ±7.2MHz (SD). Pre-operatively the eyes showed an average Brillouin-shift of 5.7162 ± 0.0242MHz (range 5.6643GHz to 5.7572GHz) which decreased to 5.6784 ± 0.0281GHz (ranging from 5.6337GHz to 5.7493GHz) at day 1 after surgery. This difference (~ 40MHz) was highly statistically significant (p<0.001, two sample unpaired t-test). At 1 month after surgery, the Brillouin-shift (5.7040 ± 0.0300 GHz, ranging from 5.6588GHz to 5.7480GHz) returned to nearly pre-operative values, with no significant difference with values obtained before the procedures (p=0.25, two sample unpaired t-test).


This is the first report on the application of Brillouin microscopy on LASIK-patients. The significant but transient drop in Brillouin-shift (which is equivalent to stiffness) immediately after surgery may have no consequences on the stability of the cornea as stiffness was regained at 1 month after surgery. It can be interpreted as a result of the distorted hydration of the cornea due to the irrigation of the interface. Only long-term studies will figure out whether a reduced preoperative Brillouin-shift will be a prognostic factor for iatrogenic keratectasia.

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