Quantitative spatial analysis of the distribution of NADPH-diaphorase-positive neurons in the developing and mature rat retina.

NADPH-diaphorase (NADPH-d) histochemistry labels a subpopulation of nitric oxide-synthesizing amacrine cells in the inner nuclear layer of the rat retina. We have studied their morphology and distribution in postnatal and adult rats in whole-mounted retinae. NAPDH-d-positive neurons are detected as early as postnatal day (P)5, especially in the peripheral retina; intense labeling of somata and long lengths of dendrites is obtained between P10 and P18, after which only the somata exhibit NADPH-d activity. The density and number of these cells increase progressively from P7 to P14, with a significantly higher density in the central retina as compared to the periphery. The sociology of these cells was analyzed quantitatively studying the Voronoi domains: a polygon area can be drawn that delineates the territory of the map that is closer to the cell than to any other cell of the map. In addition, we calculated the conformity ratio of Cook, i.e., the mean nearest neighbor distance/standard deviation of all the nearest neighbor distances, in order to reveal whether or not these cells are regularly distributed through the retina. We find that the distribution of the NADPH-d-positive cells tends to be regular throughout the retina: the local coefficient of variation (obtained by comparing the size of each Voronoi polygon area to those of its neighbors) tends to regularity at P14 and remains unaltered through maturity. Therefore, as other cell types, NADPH-d-positive amacrine cells are almost regularly distributed from the time of eye opening and nitric oxide may play a role in the development of retinal circuitry and in the regulation of retinal blood flow.

Intraocular pressure and progression of visual field damage.

Contradicting results concerning IOP control and visual field deterioration are presented. Some of these inconsistencies may be due to the statistical method of analysis. Sixty POAG patients with a perimetric follow-up over 3 years were selected. Mean and maximum IOPs were considered during the same period. The patients were divided into two groups according to the IOP control (well controlled or poorly controlled). Visual field progression was defined as a reduction in sensitivity over the fifth percentile in more than four points. Mean IOPs were not significantly different in the group of patients with a visual field deterioration compared to the stable ones, but the percentage of patients with a visual field deterioration was significantly higher in patients with higher IOPs. This holds especially true if IOP below 16 mmHg (G) is considered the 'target pressure'. IOP reduction seems to play an essential role in visual field progression. In glaucomatous patients, a strict (<16 mmHg (G)) might be necessary.