Provocative test combining water drinking and homatropine eye drops. Applanation versus tonography.

In a previous study (Leighton, Phillips, and Gibbs, 1970), a provocative outflow test using a combination of water drinking (20 ml./kg. body weight) and gutt. homatropine 2 per cent. in 24 open-angle glaucoma suspects caused a significantly greater fall in outflow facility and rise in outflow resistance than either water drinking alone or homatropine alone (0o02 < P < o0os in each case). When applanation tension was considered, water drinking combined with gutt. homatropine again gave the greatest rise; this was again significantly greater than the rise in applanation tension after either water alone or gutt. homatropine alone (P < o.oi in each case). This less marked inter-test difference in change in outflow (i.e. 0f02 < P < 0o05) compared with change in applanation tension (i.e. P <ooi) is likely to have been due to a wider scatter of tonographic than of tonometric readings. The difference between mean rise in applanation tension and mean rise in outflow resistance cannot unfortunately be compared statistically because they are expressed in different units.