The increasing frequency of surgery for cataract

The increasing frequency of cataract operation was investigated by examining the age related cataract extraction rates for Glasgow. Detailed analysis of case records of sample patients over the past decade was carried out to characterise trends in frequency of intraocular lens implantation, age of the patient at operation, preoperative visual acuity and rate of operation on the second eye. Between 1980 and 1987 the rate of cataract operation per thousand increased from 7.1 to 10.5 for patients aged 75 years and over and from 3.6 to 4.2 for those aged 65 to 74 years. There was a marked rise in the number of cataract operations relative to other eye operations between 1977 and 1988, from 19.3% to 37% and this increase was greatest in patients of 70 years and over. The same decade has seen intraocular lens implantation rise from 0% to 94.6% of cataract extractions. Visual acuity data show a significant trend towards operation at a better level of acuity in patients aged 70 years and over (p = 0.028) but not in younger age groups. There was no change in the visual acuity of the fellow eyes and no change in the frequency of operation on the second eye. It appears that cataract surgery is increasing more than can be predicted from the age of the population and this must be recognised in planning the future level of ophthalmology services.

Abnormality of the pattern electroretinogram and pattern visual evoked cortical response in esotropic cats

In six 3-week-old kittens, the tendon of the lateral rectus muscle of one eye was sectioned under anaesthesia in order to induce an esotropic (nasally-directed) squint. At maturity, the pattern electroretinogram (PERG) and pattern visual evoked response (PVER) were recorded under anaesthesia to phase-reversal at 1.67 Hz of a 0.5c/deg square wave grating pattern of 75% contrast. Refraction was determined by retinoscopy and confirmed by recording the PERG for different trial lenses. The amplitude and time-to-peak of the PERG and PVER were compared between operated and unoperated eyes, and with the responses of one normal and two sham-operated cats. With stimulation of the operated eye, the amplitude of the PVER was consistently reduced by 50% compared with the non-operated eye, confirming that the cats had become amblyopic as a result of the squint. While the appreciable inter-eye variations in the amplitude of the PERG of the normal and sham-operated cats precluded identification of a change in the esotropic cats, there was a consistent prolongation of the time-to-peak of the PERG by 50% with stimulation of the operated eye. This result is consistent with a retinal component to strabismic amblyopia.