SUMMARY Monocular and binocular contrast sensitivity function for a range of spatial frequencies was measured in two groups of subjects with normal vision. Statistically significant differences in performance between the younger group (age 20-30 years) and the older group (age 50-87 years) were found at all spatial frequencies sampled between 040 and 19-25 cpd. In the age range 50-87 years there was a linear decline in contrast sensitivity with age for medium and high spatial frequencies, but sensitivity for low spatial frequencies was independent of age.In recent years a number of investigators have used contrast sensitivity function (CSF) as a supplementary measure of visual performance both in normal subjects' 2 and in patients.'--Contrast thresholds are measured for a number of different spatial frequencies (the number of repetitions of a grating pattern, usually sinusoidal, within a unit of distance), and the results are represented graphically by plotting the reciprocal of the contrast threshold (contrast sensitivity) as a function of spatial frequency. In this way the performance of the eye can be specified over a wide working range and gives a broader description of visual function than the more conventional tests of visual acuity. Measurement of contrast sensitivity has revealed visual loss in patients with cerebral lesions,6 multiple sclerosis,37 macular disease,, glaucoma,' cataract,"' and amblyopia."A number of the above disorders are prevalent among older patients in whom age related changes in the eye are likely to influence the results of visual function tests. It is thought that age related changes, such as those found with visual acuity measurement, are attributable not only to lenticular yellowing and senile miosis but also to neuronal and receptor loss in the visual pathway.'2 The implication that the decline with age in human visual performance is the result of loss of neuronal quality and quantity receives support from other sources. Age related changes in the morphology of human cones"' and a decrease in the neuron population density of the macular projection Correspondence to Dr J E Ross,

Objective: To test the ability of a previously generated logistic regression model to predict caregiver strain from carer mood, negative affectivity and perceived patient functional ability. Design: Postal prospective survey. Setting: Spouses of community-residing patients identified from hospital stroke registers. Method: Spouses were assessed at three and six months after stroke. A previously derived equation was used to make predictions at three months of their level of strain at six months, which were compared with observed outcomes. Measures: Spouses were asked to complete the Caregiver Strain Index (CSI), the General Health Questionnaire (GHQ-12), the Positive and Negative Affectivity Schedule (PANAS) and to assess patients' independence in activities of daily living on the Extended Activities of Daily Living Scale (EADL). Results: Of 409 stroke patients, 276 had an identifiable co-resident spouse and 116 (42%) completed the measures. At three months after stroke, 39 carers (34%) were under significant strain with 40 (35%) under strain at six months. The predictive model using the GHQ-12, PANAS and EADL at three months was 78% accurate in predicting levels of caregiver strain at six months. Conclusion: Carers at risk of later strain could be identified for further followup. Services to provide emotional support to carers might be effective in the reduction of carer strain.

Visual function tests are used in chronic simple glaucoma to characterise the disorder, to quantify optic nerve damage, and to estimate visual disability. Conventional psychophysical measures of visual function include the assessment of visual fields and visual acuity. These tests reveal the location and extent of the visual defect and allow the clinician to determine the severity and/or progression of the disease. However, the ability of these tests to indicate the level of disability experienced by the patient is limited.' Indeed, there have been few attempts to quantify visual disability, and although the clinical history is a most important corroboration, this is the least formal aspect of the clinical assessment.

No abstract

No abstract