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Biomedical subjects

A C Bird

Publications and source records attributed to A C Bird.

At least 19 recordsLinked to original sources
PubMed1992

Evolution of age-related macular degeneration with choroidal perfusion abnormality.

Prolonged choroidal filling on fluorescein angiography in age-related macular degeneration is thought to indicate diffuse thickening of Bruch's membrane. To test the importance of this clinical sign, we reviewed the evolution of disease in eyes of patients with good visual acuity and a readable transit phase of fluorescein angiography at the time of recruitment into a longitudinal study of age-related macular degeneration. Ninety-six eyes satisfied these criteria. Of the 32 eyes with prolonged choroidal filling, 12 (38%) lost two or more lines, of visual acuity by two years, whereas only nine of 64 (14%) eyes with normal choroidal filling did so. The difference was caused by the higher incidence of geographic atrophy in the first group. The proportion of eyes that developed subretinal neovascularization was the same in the two groups, and no pigment epithelial detachments occurred. These findings indicate that this clinical sign has implications concerning visual prognosis in age-related macular degeneration.

Aged↗
PubMed1992

Severe visual loss associated with retinal telangiectasis and facioscapulohumeral muscular dystrophy.

Facioscapulohumeral (FSH) muscular dystrophy is known to be associated with retinal telangiectasis. However, there are only few reports of severe visual loss due to exudative complications, so the risk to vision has not been established. Because of the possible therapeutic implications, we have described two cases of young girls who developed FSH muscular dystrophy and exudative retinal detachment due to telangiectasis. In the first patient, the severity of the disease precluded visual recovery despite extensive photo- and cryotherapy. In the other, visual acuity in both affected eyes was retained after treatment. Fundus examinations in young children at risk of having the gene for FSH muscular dystrophy may be justified so that retinal vascular disease can be detected before it becomes untreatable.

Blindness↗
PubMed1992

Correlation between biochemical composition and fluorescein binding of deposits in Bruch's membrane.

PURPOSE: The fluorescence of drusen during fluorescein angiography is believed to have important prognostic and pathogenetic implications in age-related maculopathy. It is believed that deposits containing predominantly neutral lipids would be hydrophobic, resulting in hypofluorescence on fluorescein angiography, while the presence of polar phospholipids would be indicated clinically by hyperfluorescence because of its hydrophilic properties. To identify the potential determinants of fluorescence of drusen and Bruch's membrane, a series of macular specimens from human donors older than 60 years of age was examined. No clinical information was available concerning any previous eye disease. METHODS: In vitro fluorescein binding was recorded microscopically, and the presence of fibronectin was sought by immunohistochemistry. The results were correlated with the proportions of phospholipids to neutral lipids identified by histochemical and biochemical studies. RESULTS: It was found that high content of neutral fats was associated with lack of both fluorescein binding and fibronectin, and, conversely, in those specimens with high proportions of phospholipids, fluorescein binding was strong and fibronectin was present. CONCLUSIONS: These observations support the central hypothesis concerning biophysical changes in Bruch's membrane with age and the potential importance of fluorescein angiography in the characterization of Bruch's membrane deposits.

Aged↗
PubMed1992

Exclusion of chromosome 6 and 8 locations in nonrhodopsin autosomal dominant retinitis pigmentosa families: further locus heterogeneity in adRP.

Genetic studies have revealed that 25 to 30% of autosomal dominant retinitis pigmentosa (adRP) families have mutations in the rhodopsin gene, while the remainder do not. More recently linkage data and mutation detection have demonstrated two further loci implicated in adRP, at an as yet unidentified gene on chromosome 8p and at the human gene homologue of the mouse Rds (Retinal Degeneration Slow) gene on chromosome 6p. We have previously reported exclusion of adRP from the rhodopsin locus on 3q in two large adRP families. We now report exclusion data for both families, on chromosomes 6 and 8, demonstrating that the adRP phenotype results from mutations in at least four locations.

Chromosome Mapping↗
PubMed1992

Quantification of the ocular reactions to microfilaricides in the chemotherapy of onchocerciasis.

Severe adverse systemic and ocular reactions have complicated the chemotherapy of onchocerciasis. A method for the quantification of ocular reactions to chemotherapy has been devised at the Onchocerciasis Chemotherapy Research Centre, at Hohoe, in Ghana. Symptoms, visual function, anterior segment inflammation and disease of the posterior segment are graded. The information is entered into a computerised database which allows reaction scores to be calculated both for individual patients, and for treatment groups. This system enables comparison of adverse ocular reactions to various new chemotherapeutic regimens.

Anterior Eye Segment↗
PubMed1992

A completed screen for mutations of the rhodopsin gene in a panel of patients with autosomal dominant retinitis pigmentosa.

Recently it has been demonstrated that some families with autosomal dominant retinitis pigmentosa (adRP) have mutations in the rhodopsin gene while others do not. Previously we have identified six such mutations in seven adRP families in this laboratory, one of which was previously described in US patients. We now present a completed screen of the rhodopsin gene in a panel of 39 adRP families, by a rapid screening technique which will be of use for routine diagnosis. Nine different mutations were ultimately found, in a total of twelve of the 39 families. These include the six previously identified mutations, in codons 68-71, 190, 211, 255, 296 and 347, two new ones in codons 53 and 106, and another mutation first identified in a single US patient, in codon 58. Thus approximately 30% of adRP families have 'Rhodopsin RP' while the remainder probably have a defect elsewhere in the genome. Of those families in which rhodopsin mutations have been found, four have been classified D type, three as sectorial RP and the remainder are of uncertain classification. All families excluded from chromosome 3q by linkage have been classified R type. These data suggest a correlation between clinical sub-classification and the underlying rhodopsin/non-rhodopsin heterogeneity.

Amino Acid Sequence↗
PubMed1992

Controlled trial of laser photocoagulation of pigment epithelial detachments in the elderly: 4 year review.

Patients who were enrolled in a controlled treatment trial of laser grid photocoagulation for retinal pigment epithelial detachment as part of age-related maculopathy were reviewed 4 years after entry into the trial. The data imply that the original conclusion that this form of treatment did not improve the visual prognosis at 18 months was also justified at 4 years. It has become clear that lesions with evidence of subpigment epithelial new vessels were included in the trial. In a retrospective study the lesions were separated into those in which there was evidence of subretinal neovascularisation and those in which no such evidence existed. A difference was identified in the behaviour of the treated and untreated lesions designated avascular in that the treated eyes had a poorer visual outcome. These cases accounted for the different behaviour between two management groups in the initial study such that the original conclusion that grid photocoagulation of avascular pigment epithelial detachments in the elderly does not improve the visual prognosis is justified.

Humans↗
PubMed1992

Detection of subpigment epithelial neovascularisation in cases of retinal pigment epithelial detachments: a review of the Moorfields treatment trial.

The entry angiograms of 42 eyes with detachment of the retinal pigment epithelium in a treatment trial of laser photocoagulation were reviewed in a masked fashion by three observers in order to assess the possible presence of subpigment epithelial neovascularisation. Vascularity or avascularity was designated with reference to a list of clues believed to imply the presence of subpigment epithelial neovascularisation. As a predictor of outcome the initial assessment achieved a sensitivity and specificity of 77% and 82% respectively. Despite notable parity of the degree of sensitivity and specificity among the three observers, full agreement on the initial assessments was reached in only 23 eyes (55%), 10 with vascular and 13 with avascular outcome. Of these, only one eye which developed new vessels after 4 years had an outcome which differed from that predicted by classification of the entry angiograms.

Aged↗
PubMed1992

Abnormal dark adaptation kinetics in autosomal dominant sector retinitis pigmentosa due to rod opsin mutation.

The time course of dark adaptation was measured in 10 subjects from three families with autosomal dominant sector retinitis pigmentosa (RP) due to mutations in the first exon of the rod opsin gene. In each subject cone adaptation and the early part of the recovery of rod sensitivity followed the normal time course, but the later phase of rod adaptation was markedly prolonged. The recovery of rod sensitivity is much slower than that reported in any other outer retinal dystrophy. Using a model based upon primate data of rod outer segment length and turnover, we have calculated that the delayed phase of the recovery of rod sensitivity in the RP patients tested following strong light adaptation could be due in part to formation of new disc membrane with its normal concentration of rhodopsin rather than in situ regeneration of photopigment.

Adolescent↗
PubMed1992

Confocal imaging of the fundus using a scanning laser ophthalmoscope.

A confocal scanning laser ophthalmoscope (cSLO) was used to examine the effects of confocal optics on the image of the human fundus in vivo. Patients from a retinal clinic and a glaucoma clinic were examined using the cSLO in the confocal mode. A degree of optical sectioning could be achieved, and the results agree with a best axial resolution of 300 microns measured in a model eye. The main advantage of using a confocal system was found to be the improved contrast of the images. This improved the resolution of structures such as the lamina cribrosa and optic disc drusen which are seen in low contrast in conventional images. The improved contrast of the confocal images is partly achieved by excluding light which has been scattered within the plane of focus. Structures which multiply scatter light will become less visible with confocal optics and hard exudates were found to be an example of such a structure. The cSLO and the fundus camera are seen as complementary instruments rather than as alternatives for imaging the fundus. It is envisaged that confocal imaging will enable details of the fundus to be revealed which are at present not seen in conventional images.

Fundus Oculi↗
PubMed1992

Nine generations of a family with autosomal dominant retinitis pigmentosa and evidence of variable expressivity from census records.

We present a nine generation family with autosomal dominant retinitis pigmentosa (ADRP). Evidence of blindness in the early generations, as obtained from census returns and clinical records, and examination of current patients show variable expressivity with a spectrum which ranges from asymptomatic in late life to blindness in the third decade of life. The family is not linked to any of the chromosomal locations so far described in ADRP and further illustrates the heterogeneity of the disorder.

Adolescent↗
PubMed1992

Macular disease in an elderly population.

In order to obtain more accurate information concerning the prevalence of macular diseases in an elderly population, a clinical study was undertaken on a sample of 430 members of the general population over the age of 65 years in London. Degenerative age-related macular changes were clinically visible in about 25%, and 2.8% had a lesion causing loss of visual acuity due to macular disease. Age was the only risk factor identified for age-related changes. No correlation was identified with the prevalence of hypertension, smoking, or diabetes mellitus between groups. In addition, symmetry was shown in the number of drusen, as well as their size, density and fluorescence in the central and peripheral areas between the eyes of affected subjects. The prevalence data from this study represent a baseline for the interpretation of hospital-based data and for the planning of health care.

Aged↗
PubMed1992

Recombination between rhodopsin and locus D3S47 (C17) in rhodopsin retinitis pigmentosa families.

Autosomal dominant retinitis pigmentosa (adRP) has shown linkage to the chromosome 3q marker C17 (D3S47) in two large adRP pedigrees known as TCDM1 and adRP3. On the basis of this evidence the rhodopsin gene, which also maps to 3q, was screened for mutations which segregated with the disease in adRP patients, and several have now been identified. However, we report that, as yet, no rhodopsin mutation has been found in the families first linked to C17. Since no highly informative marker system is available in the rhodopsin gene, it has not been possible to measure the genetic distance between rhodopsin and D3S47 accurately. We now present a linkage analysis between D3S47 and the rhodopsin locus (RHO) in five proven rhodopsin-retinitis pigmentosa (rhodopsin-RP) families, using the causative mutations as highly informative polymorphic markers. The distance, between RHO and D3S47, obtained by this analysis is theta = .12, with a lod score of 4.5. This contrast with peak lod scores between D3S47 and adRP of 6.1 at theta = .05 and 16.5 at theta = 0 in families adRP3 and TCDM1, respectively. These data would be consistent with the hypothesis that TCDM1 and ADRP3 represent a second adRP locus on chromosome 3q, closer to D3S47 than is the rhodopsin locus. This result shows that care must be taken when interpreting adRP exclusion data generated with probe C17 and that it is probably not a suitable marker for predictive genetic testing in all chromosome 3q-linked adRP families.

Chromosome Mapping↗
PubMed1992

Abnormal dark adaptation and rhodopsin kinetics in Sorsby's fundus dystrophy.

Scotopic visual thresholds and time courses for dark adaptation were determined in eight patients with Sorsby's fundus dystrophy. Rhodopsin regeneration also was recorded in two. All patients had poor night vision and a visible yellow deposit at the level of Bruch's membrane that was confluent in the posterior pole. In retinal regions with the yellow deposit, scotopic thresholds were elevated, the rod-cone break was delayed or indistinct, the time courses for the rod portion of the dark adaptation curve was prolonged, and rhodopsin regeneration was slow in the one patient in whom measurements were made. In regions of ophthalmoscopically normal retina, dark adaptation was affected minimally, and in one patient, rhodopsin was regenerated at a normal rate. It was hypothesized that the abnormal dark adaptation and rhodopsin kinetics might be caused by reduced metabolic exchange across a thickened Bruch's membrane.

Adult↗
PubMed1992

[The Bruch membrane and choroid. Angiography and functional characteristics in age-related changes].

Age-related changes in the retinal pigment epithelium and Bruch's membrane are believed to play an important role in the pathogenesis of age-related macular degeneration. Ophthalmoscopically visible drusen in the macular area may precede the complications causing visual loss. In addition to these localized depositions of debris in Bruch's membrane, histological methods could demonstrate linear deposits in Bruch's membrane which may also profoundly influence the development of complicated macular aging changes. It is difficult to identify linear deposits clinically, but as an indirect criterion for diffuse thickening and linear deposits in Bruch's membrane regression of the choriocapillaris with consequent prolongation of the choroidal filling phase in fluorescein angiography is suggested. This feature was observed in 26% of elderly patient. In association with these areas of regressed choroidal capillaries, loss of visual function was found in fine matrix perimetry.

Aged↗
PubMed1992

Functional loss in age-related Bruch's membrane change with choroidal perfusion defect.

During a prospective study of age-related macular degeneration, evidence of diffuse Bruch's membrane disease was sought using fluorescein angiographic evidence of a prolonged choroidal filling phase. Dark-adapted static perimetry was done on eight eyes with this angiographic sign and on six eyes with a similar number of drusen but no manifest choroidal perfusion abnormality. Scotopic threshold was measured using the Humphrey automated perimeter and fine matrix mapping. In eyes without delayed choroidal perfusion, no discrete areas of increased threshold were found compared with the background sensitivity. By contrast, in seven of the eight eyes with fluorescein angiographic evidence of prolonged choroidal filling, discrete areas of scotopic threshold elevation (up to 3.4 log units) were recorded; these corresponded closely to regions of choroidal perfusion abnormality. It was postulated that diffuse deposits of abnormal material might account for both the perfusion abnormality and functional loss by acting as a diffusion barrier between the choriocapillaris and the retinal pigment epithelium.

Aged↗