Aj. Weber et al., Experimental glaucoma and cell size, density, and number in the primate lateral geniculate nucleus, INV OPHTH V, 41(6), 2000, pp. 1370-1379
PURPOSE, TO examine the effects that elevated intraocular pressure (IOP), a
glaucoma risk factor, has on the size, density, and number of neurons in t
he primate lateral geniculate nucleus (LGN).
METHODS. The monkey model of experimental glaucoma was combined with standa
rd histologic staining and analysis techniques. Fourteen animals were exami
ned.
RESULTS. Mean IOPs higher than 40 mm Hg for 2.5, 4, 8, and 24 weeks resulte
d in reductions of 10% to 58% in the cross-sectional areas of LGN neurons r
eceiving input from the glaucomatous eye. Reductions for animals with lower
mean IOPs (37 and 28 mm Hg) for 16 and 27 weeks were 16% and 30%, respecti
vely. Neurons receiving input from the normal eye also were reduced in size
(4-26%). No differential effect in cell size was seen for magnocellular ve
rsus parvocellular neurons. Elevation of IOP resulted in an increase in cel
l density in all layers of the LGN, The increase was approximately two time
s greater in parvocellular (59%) than magnocellular (31%) layers. When corr
ected for volumetric shrinkage of the LGN, the estimated loss of neurons wa
s approximately four times greater in the magnocellular than parvocellular
layers (38% versus 10%).
CONCLUSIONS. Elevation of IOP affects the size, density, and number of neur
ons in the LGN, and the volume of the nucleus itself. Although higher mean
pressures (more than 40 mm Hg) reduce the period during which these changes
occur, comparable damage can be achieved by ct cn moderate (28-37 mm Hg) l
evels of elevated IOP;On the basis of cell loss, elevation of IOP appears t
o have a more profound degenerative effect on the magnocellular than on the
parvocellular regions of the LGN.