Corneal hydration monitored by laser-induced breakdown spectroscopy.
BACKGROUND
Corneal hydration is an important factor in laser corneal ablation. In photorefractive keratectomy (PRK), corneal ablation rate and final ablation surface quality are strongly dependent on corneal hydration. We used a spectroscopic technique for monitoring corneal hydration during PRK.


METHODS
Hydroxyethlymethacrylate (HEMA) was employed for corneal hydration modeling. Hydrated HEMA samples were irradiated with a pulsed Nd:YAG laser (1064 nm, 10 mJ/pulse, pulse duration 15 nsec). Successive emission spectra corresponding to different degrees of hydration were recorded on a gated optical multichannel analyzer. The weight of the sample and hence its water content was monitored during the entire procedure with a sensitive balance. One rabbit and one human cornea were used to demonstrate the spectral analogy between the model and corneal tissue.


RESULTS
The most noticeable dependence on water content of the substrate was that of atomic emission lines of Ca at 393 nm and 396 nm.


CONCLUSIONS
Plasma emission spectra exhibited significant dependence on sample hydration. This dependence can be used for estimation of water content of irradiated model material and real cornea.
Pallikaris
I G
IG
University of Crete, School of Health Sciences, Department of Ophthalmology, Heraklion, Greece. pallikar@med.uch.gr
Ginis
H S
HS
Kounis
G A
GA
Anglos
D
D
Papazoglou
T G
TG
Naoumidis
L P
LP
D000042:Absorption; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism* / Q000601:surgery; D006801:Humans; D066298:In Vitro Techniques; D054018:Lasers, Excimer; D008689:Methacrylates / Q000737:chemistry; D008953:Models, Anatomic; D016343:Monitoring, Intraoperative; D018903:Photorefractive Keratectomy; D011817:Rabbits; D013057:Spectrum Analysis / Q000379:methods
D008689:Methacrylates; C005044:hydroxyethyl methacrylate