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L. Alarcon-Martinez, P. De La Villa, M. Salinas-Navarro, D. García-Ayuso, I. Cánovas, M. Avilés-Trigueros, M. P. Villegas-Pérez, M. Vidal-Sanz; Laser Photocoagulation of the Perilimbal and Episcleral Veins Induced Elevation of the Intraocular Pressure. Functional Effects in the Albino Mice Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4354.
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To investigate functional changes in the retina associated with elevation of the intraocular pressure.
Laser photocoagulation (532nm wavelength, 300mW power, 0.5 second duration, 100 µm diameter spot size) was applied to limbar and episcleral veins of one eye in a series of adult swiss mice (30-45 g). Intraocular pressure (IOP) was measured in both eyes by using the Tonolab tonometer prior to and at 24-48 h, 1, 2, 4, weeks after lasering (group I). A second series of animals (group II) was also analyzed at 6 and 8 weeks after photocoagulation. Electroretinographic (ERG) responses were recorded from both eyes prior to lasering and at 24-48h, 1, 2, 4, 6 or 8 weeks after eye photocoagulation. Ganzfeld dome or light emission diodes were used for light stimulation; light intensities ranging from -6 to 2 log cd·s·m-2 were used. ERG a and b waves were analyzed in scotopic conditions.
Laser treatment induced an increase in mean intraocular pressure of approximately 90% over baseline that was maintained throughout the first few days. In group I basal IOP values (mean ±SD) were 13.1±1.7 (n=14), increased to 24.3 ±6.8 at 48 hours and decreased to basal values by one week. In group II similar values were observed: basal IOP values (14.7±1.7; n=5) increased to 22.2 ±8.9 at 48 hours and decreased to basal values by one week. In group I, mean ERG a- or b-wave amplitudes at 24h, 1, 2 and 4 weeks represented 39 or 30, 36 or 33, 53 or 36 and 54% or 34% of their basal, pre-treatment values, respectively. In group II, mean ERG a- or b-wave amplitudes at 24h, 1, 2, 4, 6 and 8 weeks represented 36 or 43, 27 or 32, 35 or 46, 54 or 53, 48 or 43, and 46% or 41% of their basal, pre-treatment values, respectively.
Lasering of the perilimbar and episcleral veins in swiss mice results in elevation of the intraocular pressure that leads to severe amplitude diminution of both the a- and the b-waves of the ERG. These diminutions appear as early as 24 hours after lasering and do not recover significantly. These results suggest that elevation of the IOP results in inner and outer retinal layer damage.
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