Assessment of established cases of chronic simple glaucoma

Quantitative relationship between cupping of the optic disc and visual field loss in chronic simple glaucoma

The extent of cupping was measured from optic disc photographs of 300 patients with ocular hypertension and suspected or established chronic simple glaucoma, and their visual fields were recorded. The incidence of field defects increased as the vertical cup:disc ratio increased, a value of 0-70 for this ratio being a particularly useful guide to the presence or absence of field loss. There was a significant correlation between the extent of cupping and the size of the visual field. The vertical cup:disc ratio was the most useful quantitative index of cupping.

Partial angle closure

During the course of negative provocative test for closed-angle glaucoma using pilocarpine and phenylephrine 60% of eyes develop significant reductions in outflow facility at some stage during the test. It is shown that these reductions can be explained by postulating the presence of partial-angle closure since: (1) A random sample (6) of 53 eyes showing an abnormal response subsequently had a peripheral iridectomy. On reprovoking they then behaved as normal eyes with a uniform increase in outflow. (2) Fifty-eight eyes that had a peripheral iridectomy for closed-angle glaucoma (spontaneous or induced) responded to provocative testing as do normal eyes.

The variation and covariation of cup and disc diameters

The variation and covariation of cup and disc diameters were studied in a material derived from a population survey and consisting of 2,334 fundus photographs from as many eyes in 1,322 subjects. A simple device was used to facilitate focusing of the camera. The colour slides were projected on to a screen at a fixed distance and measured on ruled paper. The effect of refraction on the magnification in the eye-camera system was compensated by the use of a simple correcting factor. Some apparently quite normal discs, nevertheless, had an area more than four times larger than that of other equally normal ones. The sizes of discs and cups covaried, however, to a suprisingly great extent (r = 0.8) and changes in disc diameter were in general parallelled by similar changes in cup diameter. The amount of tissue in the optic nerve head therefore varied somewhat less than the disc size. Cup diameters were widely dispersed, unevenly distributed and heavily dependent on disc size. The "average rim breadths", on the other hand, were much less dispersed, normally distributed and independent on the disc diameter. By taking the covariation of cup and disc diameters into account the detection of any enlargement or diminution of the optic cup ought to be facilitated.

Emergence point and angulation of disc vessels in the normal eye

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