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Biomedical subjects

A C Bird

Publications and source records attributed to A C Bird.

At least 163 records · Page 9Linked to original sources
PubMed1994

Analysis of lipid deposits extracted from human macular and peripheral Bruch's membrane.

OBJECTIVE: Lipids in Bruch's membrane may affect the evolution of age-related macular disease. To determine whether these show differences in regional distribution, we analyzed lipid deposits in Bruch's membrane at macular and peripheral sites. METHODS: Thin-layer chromatography was used to measure different lipid classes extracted from macular and peripheral Bruch's membrane of 32 eye bank eyes. RESULTS: The quantity of lipid extracted was consistently higher in the macula than in the periphery of human eyes. The total from both sites and the difference between the sites increased with age. The extracted lipids consisted largely of phospholipids, triglycerides, fatty acids, and free cholesterol. There was little cholesterol ester. CONCLUSIONS: Accumulation of lipids with age appears to be greater in the central than in the peripheral region of the fundus, indicating that lesions in age-related macular degeneration and Bruch's membrane lipid deposits share a common spatial distribution. The composition is consistent with the lipids being of cellular origin.

Adolescent↗
PubMed1994

Cutaneous melanoma-associated retinopathy.

PURPOSE: To define further the syndrome of cutaneous melanoma-associated retinopathy, of which only five affected patients have been reported previously. METHODS: Three men with melanoma-associated retinopathy were examined and studied electrophysiologically. Two were studied in detail psychophysically. RESULTS: Visual symptoms consisted of flickering black and white spots, shimmering patches of colors, and night blindness. The onset was acute and nonprogressive. Reduced amplitudes were observed in the flash electroretinographic b-wave and the pattern electroretinogram. Color vision, contrast sensitivity, and light- and dark-adapted perimetric sensitivities were abnormal. In one patient, the rate of dark adaptation was normal with elevated final cone and rod thresholds. CONCLUSIONS: Melanoma-associated retinopathy is a paraneoplastic syndrome distinct from cancer-associated retinopathy with a different visual prognosis. It may preferentially affect men.

Aged↗
PubMed1994

Bilateral macular drusen in age-related macular degeneration. Prognosis and risk factors.

BACKGROUND: In patients with unilateral visual loss related to age-related macular disease, the risk of visual loss in the second eye is documented as being between 7% and 10% per year. The risk is uncertain in those with good vision with each eye and bilateral macular drusen. METHODS: In a prospective study, 126 patients with bilateral drusen were reviewed annually for up to 3 years. Serial fundus photographs and fluorescein angiograms were analyzed independently by two readers in a masked fashion using a standardized grading scheme, including size, number, density, and fluorescence angiographic behavior of drusen. RESULTS: New lesions occurred in one or both eyes of 17 (13.5%) of the 126 patients. The cumulative incidence of exudative or nonexudative lesions was 8.55% at 1 year, at 2 years 16.37%, and 23.52% at 3 years for patients older than 65 years of age. Significant risk factors included the degree of confluence of drusen within 1600 microns of the center of the fovea (P = 0.023), focal hyperpigmentation (P = 0.004), slow choroidal filling (P = 0.023), and focal extrafoveal areas of atrophy of the retinal pigment epithelium (P = 0.042). CONCLUSIONS: The results give an estimate for the incidence of complicating lesions in patients with bilateral drusen and identify those features indicating higher than average risk of visual loss.

Aged↗
PubMed1994

Acute zonal occult outer retinopathy (AZOOR) associated with multifocal choroidopathy.

Acute zonal occult outer retinopathy (AZOOR) may be precipitated by various retinal disorders and is characterised by rapid loss of visual field which cannot be explained by the ophthalmoscopic changes consequent upon the initiating disease. The electroretinogram is abnormal, indicating that the field loss is due to retinal dysfunction. The phenomenon was first recognised in the multiple evanescent white dot syndrome (MEWDS) as the enlarged blind spot syndrome. It was subsequently described with multifocal inner choroidopathy and acute macular neuropathy (AMN). We have identified 7 patients who presented with widespread visual loss associated with multifocal inner choroidopathy in whom functional loss was documented with electroretinography and automated visual field testing. All patients were young, myopic, and otherwise healthy women. Initial photopsia was noted by 4 patients. Fundus findings included scattered small partially pigmented yellowish lesions resembling those in multifocal inner choroidopathy or pseudo presumed ocular histoplasmosis syndrome, disc swelling, vitritis, and secondary choroidal neovascularisation. Two patients had bilateral involvement. All patients had an enlargement of the blind spot, and widespread visual field loss which was not explained by fundus changes. All had an abnormal electroretinogram suggesting widespread retinal disease. In AZOOR retinal dysfunction occurs without corresponding visible retinal lesions. This disorder appears to be precipitated by several conditions, although the causal relationship between the initiating event and the widespread functional loss is unknown.

Acute Disease↗
PubMed1994

Screening for ophthalmic manifestations of sickle cell disease in the United Kingdom.

There are marked variations in the manifestations of sickle disease in different populations. The ocular complications of this condition amongst the Afro-Caribbeans living in the United Kingdom have not previously been reported. We present the preliminary results of an ophthalmic screening programme at King's College Hospital, London. One hundred eyes of 50 patients with sickle cell disease were assessed. Full ocular examination was performed including fundus fluorescein angiography. We have looked at the haematological and clinical profile of the patients involved as well as the number of days spent in hospital during the year preceding the eye examination. The incidence of grade II retinopathy was found to be significantly higher than grade I in SC disease. This concurs with the results of the Jamaican screening and confirms that these patients are at higher risk of visual impairment than those with SS disease. Our results also agree with the Jamaican experience which suggest that visual morbidity is mostly due to complications of proliferative sickle retinopathy (PSR). However, the findings in patients without proliferative changes are different; in particular, angioid streaks leading to disciforms are an important cause of visual loss in Jamaica, but were not seen in any of the 98 eyes examined in this study. No correlation was found between the grade of retinopathy and age, sex, systemic complications and various haematological parameters except for the percentage of haemoglobin F, which was significantly higher in patients with grade I (7.6) compared with grade II (4.2) retinopathy (p = 0.0127).

Adolescent↗
PubMed1994

Inherited venous beading.

Inherited retinal venous beading is a rare autosomal disorder. We describe three affected members in three generations of a single family. It is evident that there may be gross asymmetry of affection between the two eyes, and highly variable expressivity such that the diagnosis may not be evident without a family survey. One patient had remarkable spontaneous recovery of vision.

Adolescent↗
PubMed1994

Identification of a sixth locus for autosomal dominant retinitis pigmentosa on chromosome 19.

We report the mapping of a sixth locus for autosomal dominant retinitis pigmentosa (adRP) to 19q13.4. After a total genome linkage search using over 300 markers in a single large pedigree, marker loci on the long arm of chromosome 19 showed significant linkage with the disease locus. Since the mapping information for the marker loci used in this study was derived from two different genome maps, we established genetic distances between relevant marker loci so that linkage information could be combined from both maps. A conventional three point analysis between the adRP phenotype and markers D19S180 and D19S214 gave a maximum lod score of 4.87. Combining data from these and other markers, we used the recently described multiple two point programme FASTMAP to simulate a multipoint analysis of the full data set. This gave a lod score of 5.34 in the interval between markers D19S180 and D19S214. Recently this laboratory has also reported the linkage of another form of retinal degeneration known as cone-rod dystrophy (CRD) to a genetically different set of markers from 19q. Linkage data presented here clearly supports the existence of two separate retinal genes in this part of the genome.

Chromosome Mapping↗
PubMed1994

Recurrent choroidal neovascularization after laser photocoagulation in Sorsby's fundus dystrophy.

BACKGROUND: Patients with autosomal dominant Sorsby's fundus dystrophy are at high risk of severe visual loss due to choroidal neovascularization (CNV) during the fourth or fifth decade of life. METHODS: To assess the efficacy of argon laser photocoagulation for extrafoveal well-defined CNV, we analyzed retrospectively the clinical course in 10 eyes of 7 patients who had Sorsby's fundus dystrophy with CNV 200 microns to 2,500 microns from the center of the foveal avascular zone, and who subsequently underwent laser photocoagulation. RESULTS: All treated eyes developed severe visual loss as a consequence of recurrent or persistent CNV occurring on the foveal side of the treatment scar, which extended under the fovea. The average time until occurrence of angiographically documented CNV after initial treatment was 8.1 +/- 8.9 weeks, but ranged from 2 weeks to 32 weeks. Retreatment for persistent or recurrent extrafoveal CNV was performed in 5 eyes, but CNV recurred in all 5. CONCLUSIONS: Results of this study suggest that the risk of persistence or recurrence of CNV after laser photocoagulation for extrafoveal CNV is unusually high in patients with Sorsby's fundus dystrophy, and that this treatment is ineffective in preventing severe visual loss in such patients.

Adult↗
PubMed1994

Ocular manifestations in autosomal dominant retinitis pigmentosa with a Lys-296-Glu rhodopsin mutation at the retinal binding site.

A lysine to glutamic acid substitution at codon 296 in the rhodopsin gene has been reported in a family with autosomal dominant retinitis pigmentosa. This mutation is of particular functional interest as this lysine molecule is the binding site of 11-cis-retinal. The clinical features of a family with this mutation have not been reported previously. We examined 14 patients with autosomal dominant retinitis pigmentosa and a lysine-296-glutamic acid rhodopsin mutation. Four had detailed psychophysical and electrophysiological testing. Most affected subjects had severe disease with poor night vision from early life, and marked reduction of visual acuity and visual field by their early forties. Psychophysical testing showed no demonstrable rod function and severely reduced cone function in all patients tested.

Adolescent↗
PubMed1994

Peripheral retinal vasculature in normal Jamaican children.

A prospective study of the peripheral retinal vasculature in a Jamaican cohort of subjects with sickle cell disease has been in progress over a period of 12 years using fluorescein angiography. Various vascular patterns were identified but their significance was unclear since no comparable records were available in subjects of a similar age with normal (AA) haemoglobin genotype. Fluorescein retinal angioscopy and angiography have been performed in 76 haemoglobin AA controls participating in the cohort study. The peripheral retinal capillary bed could be seen and photographed in a limited portion of the temporal peripheral fundus in a majority of this group, and there was considerable variation in the vascular pattern which could be characterised. These observations allow deviations from normal to be identified in the retinal vasculature in subjects with sickle cell disease.

Adolescent↗
PubMed1994

New classification of peripheral retinal vascular changes in sickle cell disease.

The systemic complications of homozygous sickle cell disease (SS) are more severe than in sickle cell haemoglobin C (SC) disease, and yet visual loss due to proliferative retinopathy is more common in the latter. This anomaly is unexplained. It is believed that proliferative disease occurs in response to closure of the peripheral retinal vasculature, yet a systematic longitudinal survey of the peripheral retinal vascular bed has not been undertaken. In the Jamaica Sickle Cohort study all subjects are scheduled to receive annual ocular examination and fluorescein angiography. The results have now been analysed in subjects with SS and SC disease using a new classification system based on a comparison of the peripheral retinal vascular bed with that recorded in the cohort with normal haemoglobin (AA) genotype. The vascular patterns could be classified as qualitatively normal (type I) or abnormal (type II). An abnormal vascular pattern was identified more commonly with age, in a significantly larger proportion of subjects with SC than SS disease, and was associated with the development of proliferative disease. In order to establish the dynamics of change, the angiograms were analysed in the 18 subjects (24 eyes) who developed proliferative disease. It is shown that a qualitatively normal vascular pattern may be retained despite loss of capillary bed and posterior displacement of the vascular border. A border which is qualitatively abnormal does not revert to normal, and once abnormal, continuous evolution may occur before development of proliferative lesions. The peripheral border of the retinal vasculature was too peripheral to photographed in 13 of the 24 eyes before it becoming qualitatively abnormal. It is concluded that a normal border, if posterior, results from gradual modification of the capillary bed and indicates low risk of proliferative disease. A qualitatively abnormal vascular border occurs as a radical alteration of retinal perfusion in subjects in whom little modification of the vascular bed occurred before the event, and signals risk of proliferative disease. This classification system is useful in identifying the likelihood of threat to vision in young Jamaicans with sickle cell disease, and the higher frequency of proliferative retinopathy in SC can be explained by the higher prevalence of a qualitatively abnormal peripheral retinal vasculature.

Adolescent↗
PubMed1994

Retinitis pigmentosa families showing apparent X linked inheritance but unlinked to the RP2 or RP3 loci.

Three families with retinitis pigmentosa (RP) are described in which the disorder shows apparent X linked inheritance but does not show linkage to the RP2 and RP3 regions of the short arm of the X chromosome. The families are also inconsistent with a localisation of the disease gene between DXS164 and DXS28. In one case, reassessment of the family in the light of these results suggested that the family may have an autosomal dominant form of RP. The remaining two families are consistent with X linkage and suggest the possibility of a new X linked RP (XLRP) locus. These families highlight the difficulties in determining the mode of inheritance on the basis of pedigree structure and clinical data alone. Molecular genetics plays an important role in confirming the mode of inheritance and in detecting potential misclassifications, particularly in a group of disorders as heterogeneous as RP. They emphasise that caution is required in genetic counselling of RP families, particularly in the absence of any molecular genetic analysis.

Adult↗
PubMed1994

Natriuretic peptides and their receptors in human neural retina and retinal pigment epithelium.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) play a role in transepithelial fluid movement in the kidney and at the blood-aqueous barrier. We sought a similar natriuretic peptide-mediated regulatory system at the level of the blood-retinal barrier by investigating human neural retina and retinal pigment epithelium for the presence of ANP, BNP and their receptors. ANP and BNP binding to receptors could be demonstrated autoradiographically in all layers of the retina inclusive of the retinal pigment epithelium. Competitive preincubation with unlabeled peptides blocked the binding of the respective radioactive peptide. ANP and BNP could also be demonstrated immunohistochemically in both the neural retina and the retinal pigment epithelium. Our results suggest a role of these peptides both in the regulation of intraretinal fluid movement and--by analogy with other peptides--as possible neutrotransmittors. The localisation of ANP and BNP in the retinal pigment epithelium suggests that these peptides may influence ocular fluid homeostasis at the outer blood-retinal barrier by modulating pigment epithelial function.

Atrial Natriuretic Factor↗
PubMed1994

[Biochemical and histochemical analysis of age related lipid deposits in Bruch's membrane].

In histochemical studies the age-related deposition of different lipids in Bruch's membrane has been seen. This is important for the pathogeneses of age-related macular degeneration due to changes in diffusion characteristics. Because the specificity of histochemical results is limited, a correlation of histochemical lipid analysis with biochemical methods was performed. The macular Bruch's membrane of 27 donors (age 1-97 years) was analyzed. The results of this analysis demonstrated that the increasing histochemical staining for lipids in Bruch's membrane corresponded with an increasing amount of lipids extracted from Bruch's membrane in biochemical analysis. This lipid deposition progressed exponentially with age. However, a large variation in the type of lipid deposited could be observed, with predominant deposition of phospholipids in some eyes and of neutral lipids in others. Furthermore, the phospholipids extracted were differentiated into 50% phosphatidylcholine, 30% phosphatidylethanolamine and 20% phosphatidylinositol and phosphatidylserin. The deposition of lipids, especially neutral lipids, in Bruch's membrane may change its diffusion characteristics. This appears to be important for the pathogenesis of age-related pigment epithelium detachments. The composition of the phospholipids extracted from Bruch's membrane supports, furthermore, the concept that the material deposited is the result of metabolic limitations in the degradation of photoreceptor outer segment material.

Adolescent↗
PubMed1994

[Macular drusen. Changes in the retinal pigment epithelium and angiographic characteristics as prognostic markers].

Drusen in the macular area may precede other manifestations of age-related macular disease associated with severe visual loss. To identify fundus changes that might be predictive of advanced age-related maculopathy, we examined 79 patients with drusen for up to 3 years. Fundus photographs and fluorescein angiograms were independently analysed by two readers in a masked fashion using a standardized grading scheme. Fourteen patients (17.7%) developed a new exudative or nonexudative lesion involving the fovea. Delayed choroidal perfusion on the fluorescein angiogram, interpreted as an indicator for diffuse thickening of Bruch's membrane and relative atrophy of the choriocapillaris, was observed in 12 patients, 5 of whom developed geographic atrophy of the retinal pigment epithelium during follow-up (P < 0.009). Additional predictive characteristics included focal hyperpigmentations (P < 0.005) and focal extrafoveal areas of atrophy of the retinal pigment epithelium within 1600 microns of the center of the fovea (P < 0.031). These ocular features allow identification of patients with macular drusen at high risk for the development of complicating macular lesions.

Aged↗
PubMed1994

Membrane-bound carbonic anhydrase in human retinal pigment epithelium.

PURPOSE: Inhibition of carbonic anhydrase (CA) by acetazolamide causes a decrease in the standing potential of the retinal pigment epithelium (RPE) and an increase in the rate of subretinal fluid absorption, and it may improve cystoid macular edema. These effects are thought to be mediated by the RPE. Given the solubility coefficient of acetazolamide, the drug is most likely to act by direct inhibition of membrane-bound CA (CA IV). To identify a substrate for acetazolamide in the RPE, the distribution of CA activity and the isoform of CA in the RPE membrane were investigated. METHODS: Carbonic anhydrase activity was determined by Hansson's technique in fresh human eyes from donors of both sexes and different ages. The presence of the membrane-bound isoform CA IV was investigated immunohistochemically at the light and electron microscopic level, as well as by Western blotting in fresh RPE, and in adult and fetal RPE cultures. RESULTS: Hansson's histochemical method demonstrated CA activity on the apical and basolateral cell membrane of the RPE. Using the gamma-globulin fraction of a polyclonal antibody against pure CA IV, immunocytochemistry showed labeling for CA IV on the apical RPE membrane or morphologically polarized human adult and fetal RPE cultures. Gel electrophoresis and Western blotting demonstrated a major immunoreactive band at 55 kDa in homogenates, which was consistently reduced to approximately 35 kDa by incorporation of 0.1% Triton X-100 detergent. CONCLUSIONS: These results suggest that the clinical effects of carbonic anhydrase inhibitors on RPE function may be mediated via membrane-bound carbonic anhydrase activity in RPE and that CA IV is responsible for activity on the apical surface.

Adolescent↗