Biomedical subjects
Publications and source records attributed to A C Bird.
Seventeen patients with retinitis pigmentosa and vascular leakage were studied for humoral immunological abnormalities. Apart from raised levels of IgM in 5 patients no other abnormalities were found.
In this paper 4 patients are described who had bilateral symmetrical confluent retinal swelling followed by apparent necrosis and sloughing of the retina into the vitreous. The disease was accompanied by signs of uveitis and the clinical appearance suggested inflammation rather than infarction as the pathogenic mechanism. No systemic abnormalities were found by which the aetiology could be identified.
Twenty-six patients are described who suffered from acute bilateral multifocal pigment epithelial disease. In 7 the pattern of disease was indistinguishable from acute posterior multifocal placoid pigment epitheliopathy, while in 8 it was indistinguishable from Harada's disease. In a further 9 cases the pigment epithelial disease was associated with serious detachment of the retina simulating Harada's disease but without systemic symptoms; spontaneous resolution occurred within a few days, and there was no recurrence. One additional case had short-lived disease with detachment initially, but this was followed by severe recurrence, and the last patient had serious detachment in 1 eye but not the other. When seen as a whole these patients appeared to represent a continuous spectrum of disease making it difficult to define boundaries between one condition and another. The difficulties in distinguishing diseases according to morphology alone are emphasised.
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In a single-blind controlled clinical trial patients with optic neuritis caused by demyelination were given a single retrobulbar injection of triamcinolone. Though the treated group showed a trend towards more rapid recovery of vision than the controls, there was no significant difference in visual acuity, colour vision, or visual fields during the first six months after treatment. We conclude that routine use of corticosteroids is not justified in unilateral optic neuritis when vision in the other eye is good. Shortening the period of visual disability in bilateral disease or unilateral disease when vision in the other eye is poor, however, may be justifiable.
Eight patients with abetalipoproteinaemia have been followed for 3-4 to 15-8 years. Management included dietary fat restriction and supplements of the fat-solublevitamins A, E, and K. In the 3 oldest patients serial studies of retinal and neurological function suggest that treatment with large doses of oral vitamin E may have delayed the development or progression of the neurological and retinal lesions.
Development of senile disciform degeneration in the second eye was studied in a group of 104 patients over a period of up to five years. 12 to 15% of these patients develop disciform degeneration in the other eye each year. Patients with large and confluent drusen, especially if combined with accumulation of dye on fluorescein angiogram, were at greatest risk of developing disciform degeneration in the second eye.
Small retinal arterioles in the pig retina were occluded by argon laser photocoagulation and the morphology and topography of the resulting lesions studied by ophthalmoscopy, histology, and electron microscopy. Two days after laser coagulation ischaemic necrosis of the inner retina was observed in the territory of occluded arterioles, and swollen axon terminals packed with cytoplasmic organelles were found in the retinal nerve-fibre layer on the peripheral border of the infarcts and their border nearest to the disc. These swellings gave rise to localised zones of opacification (cotton-wool spots) at the borders of the retinal infarcts, and similar zones developed in relation to the laser burns. Amino-acid uptake and transport in retinal ganglion cells was studied in these animals by autoradiography following an intravitreal injection of tritiated leucine. When 3H-leucine was injected at the same time as laser coagulation and arteriolar occlusion, label became concentrated in the swollen axon-terminals on the peripheral aspect of 2-day-old infarcts but was absent from the terminals on the disc side of infarcts. The accumulation of 3H-leucine and organelles was attributed to interruption of orthograde axoplasmic transport. When 3H-leucine was injected into the vitreous 2 days prior to laser occlusion, label became distributed throughout the axoplasm and then accumulated in swollen axon terminals on both sides of infarcts after a further 2 days. An obstruction to both orthograde and retrograde axoplasmic flow was thus demonstrated. We concluded that cotton-wood spots should be redefined as accumulations of cytoplasmic debris in the retinal nerve-fibre layer caused by obstruction of orthograde or retrograde axoplasmic transport in ganglion cell axons.
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Posterior segment ocular lesions were examined in 244 selected patients with onchocerciasis from the Sudan-savanna and rain-forest areas of the United Cameroon Republic. Fluorescein fundus angiography was performed on 210 cases. As a result of this study the following conclusions were drawn: 1. The heterogeneity of single lesions, and the occurrence of different types of lesion in a single eye or two eyes, prevented subdivision of the disease into distinct forms and suggested that inflammation alone was responsible for fundus lesions in onchocerciasis. 2. Optic nerve disease, alone or in the presence of choroido-retinal changes, was responsible for a large proportion of the blindness due to posterior segment lesions in onchocerciasis (87.6 per cent in this series).
The overlying retinal blood vessels were abnormal in five cases of congenital hypertrophy of the retinal pigment epithelium. This illustrated the well-recognized association between outer retinal degeneration and obliteration of the overlying retinal vasculature. The proposed pathophysiological mechanisms, however, seem inadequate to explain completely the morphological changes of the retinal blood vessels in the presence of atrophy of the outer retina.
Peak angular saccadic velocities were measured during 30 degrees saccades in 18 patients with internuclear ophthalmoplegia who had full or nearly full adduction range, and 25 normal subjects. The following observations were made: 1. In the normal group adduction velocities were significantly faster than abduction velocities and centring movements were faster than decentring movements. 2. In patients with internuclear ophthalmoplegia adduction movements were significantly slower than in normal subjects and were significantly slower than abduction velocities. 3. Abduction velocities in patients with internuclear ophthalmoplegia were significantly slower than abduction velocities in normal subjects. It was concluded that measurements of peak angular velocities during saccades may be useful in detecting internuclear ophthalmoplegia or confirming the presence of suspected internuclear ophthalmoplegia. Slow abduction suggests that many patients with internuclear ophthalmoplegia (60 per cent in this series) have lesions affecting the supranuclear pathways subserving horizontal conjugate gaze.
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Suprathreshold fundus lesions produced by ruby and argon laser photocoagulation were studied within 24 hours by light and electron microscopy. It was shown that damage was maximal in the outer retina in all ruby laser lesions and extramacular argon laser lesions. In both monkey and human, inner retinal damage occurred independently of outer retinal damage in macular lesions produced by the argon laser. In lesions produced by equal energy, inner retinal damage was more severe in humans than in monkeys. In both species outer retinal damage was less severe in the foveal than the parafoveal region and this disparity was greater in humans than in monkeys. These findings are important to the therapeutic use of argon laser energy for mascular disease. In particular, absortion of energy in the inner retina reduces the energy available in the treatment of subretinal lesions in the foveal area, and causes unwanted neuroretinal damage. The higher sensitivity to argon laser irradiation of the human fovea compared with the monkey fovea, has not been appreciated when defining laser safety limits.
Of 107 consecutive patients with genetically-determined retinitis pigmentosa, 23 were provisionally diagnosed as having inherited the disease in an X-linked fashion. 42 affected males and 61 females were examined, and from the data obtained the following conclusions were drawn: (1) X-linked retinitis pigmentosa exists and is distinct from choroideremia. (2) In contrast to the results of previous surveys, X-linked retinitis pigmentosa is a common form of this disease and over 20 per cent. of retinitis pigmentosa is probably transmitted in an X-linked manner. (3) (a) In contradistinction to the findings of previous investigators, most if not all adult heterozygous females have detectable degenerative changes in the ocular fundus. (b) The ocular changes in heterozygous females are most easily detected by fundus examination, visual field testing, dark adaptation measurements, and estimation of retinal rhodopsin concentration. The single most frequent abnormality is peripheral retinal pigment epithelial atrophy, which is found in all adult heterozygous females. (c) The pattern of retinal dysfunction in heterozygous females, and in particular preservation of the ocular electrical responses, suggests that the disease in women is qualitatively different from that in men and in other genetic forms of retinitis pigmentosa. There is some evidience that the disease in heterozygous women is patchy. (d) Degeneration in heterozygous females is usually symmetrical, but great variation was found in the severity of degeneration amongst heterozygotes of similar ages. No non-genetic influences were found to account for this. No evidence came to light by which the importance of X-chromosome inactivation could be assessed in determining the phenotype of heterozygous women. (4) No evidience is available to determine the number of X-linked genes transmitting the disease.