| The purpose of this study was to determine the effect of retinal ganglion cell (RGC) axotomy and death on the thickness of the inner plexiform (IPL), inner nuclear (INL), and outer plexiform layers (OPL), as well as the densities of short- (S) and middle-to-long-wavelength (M/L) cones in the porcine retina.;Unilateral, peripapillary RGC axotomy was performed in six domestic pigs using an argon laser. In eight additional pigs the optic nerve was surgically transected. With the exception of two eyes that underwent sham surgeries, the contralateral eyes were not treated and served as controls. Damage to the retinal vasculature was ruled out with fluorescein angiography. Nine months later the retinas were flat mounted, and biopsies were taken at four retinal locations. Cone densities were determined with anti-visual pigment antibodies, COS-1 for M/L and OS-2 for S pigment. Semithin cross sections were made through all biopsies to measure the thickness of the retinal layers. The effect of axotomy was quantified by optic nerve axon density measurements and RGC counts. The parametric t-test and the nonparametric Wilcoxon rank sum test were used to compare the response variables between the lasered and the contralateral normal eyes (alpha = 0.05, beta = 0.3). Results from the eyes with surgical optic nerve section were used for descriptive statistics.;Five of the six animals that underwent laser surgery completed the study. Treatment of the peripapillary retina with the argon laser resulted in a mean decrease in axon densities of 31%. Only two of the eight eyes that underwent surgery for optic nerve section completed the study. They did not contain any RGCs or optic nerve axons. Severe complications occurred such as retinal detachments and intraocular hemorrhages in the remaining eyes with optic nerve sections. There was no significant difference in the thickness of IPL, INL, and OPL as well as S and M/L cone densities between normal and axotomized retinas. Similarly, no obvious changes were noticed in the retinas of the eyes with complete optic nerve sections.;In conclusion, no signs of retrograde transsynaptic degeneration were observed in porcine retinas nine months after axotomy-induced RGC death. |
