The intervertebral disc is an avascular tissue, maintained by a small population of cells that obtain nutrients mainly by diffusion from capillaries at the disc-vertebral body interface. Loss of this nutrient supply is thought to lead to disc degeneration, but how nutrient supply influences viable cell density is unclear. We investigated two factors that influence nutrient delivery to disc cells and hence cell viability: disc height and blood supply. We used bovine caudal discs as our model as these show a gradation in disc height. We found that although disc height varied twofold from the largest to the smallest disc studied, it had no significant effect on cell density, unlike the situation found in articular cartilage. The density of blood vessels supplying the discs was markedly greater for the largest disc than the smallest disc, as was the density of pores allowing capillary penetration through the bony endplate. Results indicate that changes in blood vessels in the vertebral bodies supplying the disc, as well as changes in endplate architecture appear to influence density of cells in intervertebral discs.

SUMMARYpattern is almost always clockwise. We believe that this specific pattern is likely to be due to the effect of the elec tromagnetic fields of the eye on the migrating epithelial cells and present a theory to explain this phenomenon. In 3 eyes of 2 other patients with chronic epitheliopathies we observed a random distribution of cells that did not con form to any specific pattern. We have termed this con dition 'blizzard keratopathy'.

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The range of clinical changes that occur in posterior uvei tis have been well documented. We describe two clinical features of anterior uveitis which we have termed 'iris pigment epithelitis' and 'iris vasculitis'. Other clinical forms of iritis also exist and together with our described findings parallel the spectrum of clinical presentations in posterior uveitis.

We studied the pupil dilatation of patients with pseudoexfoliation, normals, diabetics and patients with chronic open angle glaucoma to establish whether there was a significant difference in the mydriasis achieved with cyclopentolate and phenylephrine.