title: Microstructural changes in sclera under thermo-mechanical effect of 1.56 µm laser radiation increasing transscleral humor outflow.
abstract: OBJECTIVE
  Pores in the sclera are a candidate pathway for aqueous transport and therefore can be utilized to decrease the intraocular pressure (IOP) in glaucomatous eyes. Since pore formation is a well-known mechanism for stress relaxation in solids, laser-induced creation of pores in cartilage increases hydraulic permeability and promotes tissue regeneration. The aim of this paper is to demonstrate the thermo-mechanical effect of non-destructive laser irradiation on microstructural changes in sclera, in particular pore formation, resulting in substantial increase of water permeability of eye tissues that can be a novel approach to normalize the IOP.
  
  
  METHODS
  Experiments were performed ex vivo on eight eyes of four mini-pigs and in vivo on eight eyes of four rabbits using pulse repetitive laser radiation of 1.56 µm in wavelength. Twenty laser spots of 0.6 mm in diameter with laser settings (power 0.9 W, pulse duration of 200 milliseconds, pulse repetition rate of 2 Hz) resulting in substantial increase of sclera hydraulic permeability were applied on the sclera at 1-2 mm from the eye limb. Sclera and underlying structures (choroid and ciliary body) of the rabbits' eyes were examined histologically in 1 and 45 days after laser irradiation, atomic force microscope (AFM) was applied before and after laser irradiation.
  
  
  RESULTS
  Histological and AFM examinations have clearly recognized laser-assisted stable structural alterations: rarefication of the collagen structure in the laser irradiated zone and formation of sub-micron pores. Laser-induced alterations in the structure of ciliary bodies were small in size and mainly reversible. We have proposed a possible mechanism of the arising pores stabilization due to formation of small stable gas bubbles in sclera tissue.
  
  
  CONCLUSIONS
  It is shown, for the first time, that thermo-mechanical effect of pulse repetitive laser irradiation results in pores formation in sclera. That can be a basis of a novel, safe, and effective technique for IOP normalization due to enhancing of uveoscleral outflow under non-destructive laser irradiation of the sclera.
authors.affiliation: Institute on Laser and Information Technologies, Russian Academy of Sciences, 2 Pionerskaya St., Moscow (Troitsk), 142190, Russia.
authors.forename: Olga I
authors.initials: OI
authors.lastname: Baum
authors.forename: Emil N
authors.initials: EN
authors.lastname: Sobol
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Bolshunov
authors.forename: Anatoly A
authors.initials: AA
authors.lastname: Fedorov
authors.forename: Olga V
authors.initials: OV
authors.lastname: Khomchik
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Omelchenko
authors.forename: Evgenii M
authors.initials: EM
authors.lastname: Shcherbakov
mesh_terms: D000818:Animals; D002924:Ciliary Body / Q000187:drug effects* / Q000502:physiology; D007429:Intraocular Pressure / Q000502:physiology / Q000528:radiation effects*; D053844:Lasers, Solid-State; D010539:Permeability / Q000528:radiation effects; D011817:Rabbits; D012590:Sclera / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure; D013552:Swine
keywords: glaucoma; intraocular pressure; pores; sclera; structure; thermo-mechanical effect of laser radiation