SUMMARYVisual performance was measured in sixty-six subjects aged from 5 to 94 years. The curve of contrast sensitivity against spatial frequency was obtained for each subject. This curve had a peak contrast sensitivity in the 2-6 c/deg (cycles/degree) range with the fall-offs to either side of the peak described, on a double logarithmic plot, by straight lines. With advancing age, the position of the peak sensitivity remained unchanged but there was an overall decrease in contrast sensitivity. The highest spatial frequency which could be perceived remained constant up to 50 years, thereafter it fell with increasing age. The slope of the low frequency straight line remained unchanged while that of the high frequency straight line fell with increasing age, i.e. the loss ofcontrast sensitivity was greater for middle range spatial frequencies than for higher spatial frequencies. The possible site of these changes, i.e. the optics of the eye, the retina/brain or higher decision making centres, is discussed.

1 The ability of cyclizine (50 mg) and perphenazine (2.5 and 5.0 mg) to counteract the emetic effects of pethidine (100 mg) and morphine (10 and 15 mg) was compared in women undergoing a standard minor operation with a standard anaesthetic. 2 Perphenazine (5.0 mg) was as effective an anti-emetic as cyclizine (50 mg) and both were more effective than perphenazine (2.5 mg). 3 The reduction in vomiting and nausea by cycizine (50 mg) and perphenazine (5 mg) was approximately the same following pethidine (100 mg) and morphine (10 mg) but much less against the larger dose of morphine. 4 Both anti-emetics had a rapid onset of action but their anti-emetic activi-y did not last as long as the emetic effect of morphine. 5 Perphenazine (5 mg) was accompanied by an unacceptably high incidence of restlessness. 6 In clinical practice cyclizine (50 mg) is preferred to perphenazine (5 mg) as an anti-emetic.

We have measured monocular and binocular contrast sensitivities in response to medium to high spatial frequencies of vertical sinusoidal grating patterns in normal subjects, anisometropic amblyopes, strabismic amblyopes and non‐amblyopic esotropes. On binocular viewing, contrast sensitivities were slightly but significantly increased in normal subjects, markedly increased in anisometropes and esotropes with anomalous binocular single vision (BSV) and significantly reduced in esotropes and exotropes without BSV. Application of a prismatic correction to the strabismic eye in order to achieve bifoveal stimulation resulted in a significant reduction in contrast sensitivity in esotropes with and without anomalous BSV, in exotropes and in non‐amblyopic esotropes. Control experiments in normal subjects with monocular viewing showed that degradative effects of the prism occurred only with high prism powers and at high spatial frequencies, thus establishing that the reduced contrast sensitivities were the consequence of bifoveal stimulation rather than optical degradation. Displacement of the image of the grating pattern by 2 deg in normal subjects and anisometropes by a dichoptic method to simulate a small angle esotropia had no effect on the contrast sensitivities recorded through the companion eye. By contrast, esotropes showed similar reductions in contrast sensitivity to those obtained with the prism experiments, confirming a fundamental difference between subjects with normal and abnormal ocular alignments. The results have thus established a suppressive action of the fovea of the amblyopic eye acting on the companion, non‐amblyopic eye and indicate that correction of ocular misalignments in adult esotropes may be disadvantageous to binocular visual performance.

SUMMARYThe NI, P1, N2 and P2 components of the pattern visual evoked response (PVER) have been recorded to the onset of presentation of a sinusoidal grating pattern of 3 and 8 cycles/deg in groups of young (15-34 years) and old (53-94 years) subjects. The negative components were taken to arise from striate cortex and the positive components from extrastriate cortex. For grating contrasts of 3-40%, the time-to-peak of the NI, P1 and N2 components, but not the P2 component, increased with age while the amplitude and rise time showed no consistent changes. Comparisons between 3 and 8 cycles/deg revealed a longer time-to-peak of NI and P1 at 8 cycles/deg within the young group though not within the old group, i.e. an additional increment in the time-to-peak had occurred at 3 cycles/deg with ageing. This was also reflected for grating contrasts which were multiples of each individual's contrast threshold, irrespective of age. Now, the time-to-peak of NI, P1 and N2 was similar in young and old groups at 8 cycles/deg. At 3 cycles/deg, however, the time-to-peak was still longer in the old group, though the intervals between components were similar to those of the young group. This suggested the requirement for a further increment in contrast to make the time-to-peak similar, due to a selective loss of sensitivity in ageing within the low-spatial-frequency channels which are additionally sensitive to temporal modulation. Thus, it appeared that, by incrementing the stimulus contrast by the appropriate amount, the PVER of the old group could be made to resemble that of the young group. These results are consistent with the occurrence of neural changes during ageing in the retino-geniculate pathway prior to the visual cortex.