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G B Arden

Publications and source records attributed to G B Arden.

At least 19 recordsLinked to original sources
PubMed2006

Age-related macular degeneration.

Age-related macular degeneration is a common cause of blindness. Its incidence is increasing, partly due to the advancing age of the population in North America and Europe, but there is no doubt that the age-adjusted rates are also increasing, which points to some environmental influence. The condition is characterized by the appearance of retinal deposits called drusen. These and other changes form a barrier between the retinal pigment epithelium and the choroidal circulation. As a result, new vessels may grow from the choroid and penetrate the retina. These new vessels are delicate and can leak or bleed. Such episodes occur in the "wet" form of age-related macular degeneration and cause the well known disciform degeneration, which in turn leads to distortion of the image and rapid loss of vision. Even when this does not happen, areas of retina may atrophy, probably due to anoxia: this is the "dry" form of the disease, also called geographic atrophy. In trials, scattered laser burns have been applied to the retina but the long-term benefits of this are as yet uncertain. New micro-pulse lasers are coming into use which may be more effective. Surgical treatments include translocation of the retina and photodynamic therapy. Medical therapies attracting attention are intraocular injections of anti-angiogenic drugs, such as ranibizumab. These need further evaluation, as does the role of diet. Within a few years blindness due to age-related macular degeneration may be reduced by combining dietary control, screening for visual loss, and medical and surgical methods of treatment.

Aging↗
PubMed2005

Spare the rod and spoil the eye.

This review presents a new unified view of the pathogenesis of three common causes of acquired retinal degenerative disease-diabetic retinopathy, age related macular degeneration, and retinopathy of prematurity. In these three conditions, angiogenesis has a predominant role in the development of sight threatening pathology. Angiogenesis is controlled by among other factors the expression of vascular endothelial growth factor (VEGF), which in turn is regulated by absolute and relative lack of oxygen. The severe pathological manifestations of these three conditions are not part of a general underlying disease process because they are peculiar to the eye, and the profound hypoxia that develops in normal retina during dark adaptation (rod driven hypoxia) is an adequate and elegant additional factor to explain their pathogenesis. A large number of experimental reports support this conclusion, although rod driven anoxia is not generally considered as a causal factor in ocular disease. However, the hypothesis can be critically tested, and also suggests novel methods of treatment and prevention of these conditions that may be simpler and more inexpensive than current therapies and that have a smaller potential for adverse effects.

Animals↗
PubMed2004

Colour vision testing as an aid to diagnosis and management of age related maculopathy.

AIM: To provide a simple test that detects the onset of age related maculopathy (ARM), and can be used to monitor its severity. METHODS: Colour contrast sensitivity was measured using computer graphics techniques. Colour thresholds were measured along tritan and protan colour confusion axes in the presence of dynamic luminance noise. Thresholds were determined separately for two sizes of optotypes (6.5 degrees and 1.5 degrees). Natural pupils were used. Normal values for the test have been established. RESULTS: In all patients with unilateral age related macular degeneration, the smaller optotype was invisible in that eye and in almost all, the larger optotype could not be seen. In the symptomless fellow eyes (with ARM) the larger optotype thresholds were raised. The degree of loss was larger for tritan. For the smaller optotype, protan thresholds were elevated in the majority of patients. Tritan losses were greater and disproportionate to the loss seen with the larger optotype. Every person including those with minimal fundal changes had tritan test results for 1.5 degree optotypes >2 SD above the normal mean. Tritan thresholds varied with the severity of the ARM. CONCLUSIONS: The test is sensitive, simple and quick to administer, and easy for patients. Therefore, it should be useful in detecting and monitoring elderly people with age related changes in their fundi before irreversible loss of vision has occurred.

Aged↗
PubMed2003

Electrical activity in visual cortex associated with combined auditory and visual stimulation in temporal sequences known to be associated with a visual illusion.

When a subject views a visual stimulus paired with a brief click, a second click occurring approximately 80 ms later produces the hallucination of a second visual stimulus. We have used combinations of visual and sound stimuli to evoke cortical activity and have recorded the associated event-related potentials. We have recorded EPs in a conventional manner, and have calculated from multichannel recordings the Laplacian derivations to determine if the currents were generated in primary visual cortex. Clicks alone do not cause significant activity in V1, but if paired with pattern stimulation, modify the evoked potential. The timing of this extra activity almost certainly excludes "feed back" activation from higher centres, and can most simply be explained if sound-activated thalamo-cortical input can rapidly produce extra activity in 'primed' visual cortex. This finding has general implications for cortical function, for the generation of the hallucination and for 'blindsight'.

Auditory Perception↗
PubMed2002

Symptomatic abnormalities of dark adaptation in patients with EFEMP1 retinal dystrophy (Malattia Leventinese/Doyne honeycomb retinal dystrophy).

PURPOSE: To investigate the nature of symptomatic visual disturbance in patients with EFEMP1 retinal dystrophy in the absence of geographic atrophy or choroidal neovascularization. METHODS: Patients presenting to a tertiary referral centre underwent clinical evaluation, fluorescein angiography, colour contrast sensitivity, focal, pattern, and standard electroretinography, electrooculography, scotopic threshold perimetry and dark adaptometry. RESULTS: Clinical features included reduced central vision, difficulty passing from light to dark, and diffuse submacular and peripapillary deposits, which were hyperfluorescent by fluorescein angiography. Colour contrast thresholds were abnormal in all six patients studied and both pattern and focal electroretinograms were abnormal in five of six patients. The scotopic and mixed rod-cone single flash ERG was normal but two patients demonstrated reduced oscillatory potentials and one had borderline delayed 30 Hz responses. Scotopic thresholds were elevated and rod-mediated dark adaptation kinetics were markedly prolonged in all six patients when measured over the central visible confluent deposits. CONCLUSIONS: In patients with EFEMP1 retinal dystrophy with confluent macular deposits, scotopic sensitivity is reduced and dark adaptation kinetics are prolonged over the macular deposits but are normal elsewhere. These results emphasize the localised nature of functional deficits in some patients with EFEMP1 retinal dystrophy and correlate well with the patient's visual symptoms. Symptomatic visual dysfunction may precede the development of clinically evident geographic atrophy or choroidal neovascularization in this disorder.

Color Vision Defects↗
PubMed2000

Effect of alcohol and light on the retinal pigment epithelium of normal subjects and patients with retinal dystrophies.

BACKGROUND: Light absorbed by photoreceptors causes oscillations in the voltage across the retinal pigment epithelium (RPE). This is the basis of the clinical test, electro-oculography (EOG). We have previously shown that alcohol causes a sequence of voltage changes which are so precisely the same as those caused by light that they must be produced by the same RPE machinery. There is good evidence that alcohol produces its effect by a direct action on the RPE. Consequently, in diseases associated with loss of photoreceptors, alcohol should continue to produce the voltage changes of the EOG unless secondary changes have occurred in the RPE. METHODS: The alcohol response in patients with retinitis pigmentosa (RP) was investigated using EOG. RESULTS: In no patient with RP was there any alcohol rise. CONCLUSION: In patients with RP secondary abnormalities of function of the RPE must occur.

Adult↗
PubMed2000

The human electro-oculogram: interaction of light and alcohol.

PURPOSE: To investigate the production of the voltage changes evoked in the retinal pigment epithelium (RPE) by light and alcohol and the interaction of these agents. METHODS: The eye movement potential in humans was intermittently recorded to standard horizontal excursions for long periods during which either retinal illumination was altered or ethyl alcohol was administered by the oral, intragastric, or intravenous route. In other experiments, both light and alcohol were administered. RESULTS: Alcohol and light produced near identical corneofundal voltage changes (positive and then negative) over more than 40 minutes. Differences in timing between alcohol and light increases are explicable by the delays in alcohol absorption. Weak background light suppressed the effect of light steps, and low levels of background alcohol suppressed the response to subsequent doses. Backgrounds of one agent did not affect the voltage changes caused by the other. Minimal alcohol effects were seen after administration of 1 g orally or 270 mg intravenously--that is, doses that produced undetectable changes in breath alcohol. The semisaturating oral dose was approximately 20 mg/kg. CONCLUSIONS: Alcohol and light act through separate pathways to form a final common pathway inside the RPE cell that is responsible for triggering the timing of the slow oscillatory changes of EOG voltage. The sensitivity and duration with which alcohol affects the RPE are comparable with the effect of melatonin or dopamine, although only the former interacts with light similarly to alcohol. Transient modulation of the acetylcholine (Ach) neuronal receptor occurs at similar sensitivity, but all other known actions of alcohol require higher concentrations than this RPE action.

Adult↗
PubMed2000

The electro-oculographic responses to alcohol and light in a series of patients with retinitis pigmentosa.

PURPOSE: Alcohol produces changes in the electro-oculogram (EOG) similar to those caused by light, but indirect evidence indicates that alcohol directly affects the retinal pigment epithelium (RPE). An investigation of the alcohol-induced increase (termed the alcohol rise in this study) in patients with disease of the photoreceptors was therefore of interest. METHODS: Standard EOGs were recorded after oral administration of alcohol in a group of patients with retinitis pigmentosa (RP). RESULTS: The average response of 17 patients to alcohol was a slow decrease of potential, which contrasts with the normal alcohol rise. In patients with considerable residual peripheral field, alcohol produced a small increase of voltage, followed by a prolonged decrease. The slower decrease in the EOG voltage was evident in patients with small fields and could be seen even in those who had lost all visual function. Light caused small increments of EOG voltage (termed light rises), again related to the field size. CONCLUSIONS: It is probable that the intracellular signaling system that causes the alcohol and light rises is lost in RP.

Administration, Oral↗
PubMed1999

The effect of neodymium: YAG capsulotomy on contrast sensitivity and the evaluation of methods for its assessment.

OBJECTIVE: To determine the most appropriate method for measuring the effect on contrast sensitivity of neodymium:YAG (Nd:YAG) posterior capsulotomy for early posterior capsular opacification (PCO). DESIGN: Prospective comparison of five different methods for luminous contrast sensitivity testing in patients undergoing capsulotomy. PARTICIPANTS: Sixteen patients with PCO involving the visual axis and visual acuities of 20/40 or better were recruited sequentially. INTERVENTION: All patients were tested with each of the five tests before and after Nd:YAG capsulotomy. MAIN OUTCOME MEASURES: The contrast sensitivity function was measured with variable contrast sine wave gratings using the Vistech VCTS 6500, Mentor B-VAT-II and a computer graphics system. Peak contrast sensitivity at 3 cyc/deg was compared with two letter tests, the Pelli-Robson chart, and a computer that generated optotypes. RESULTS: Significant generalized improvement that was not frequency selective was measured over the entire contrast sensitivity function after capsulotomy. The five tests did not significantly differ (P > 0.05) in their measurement of peak contrast sensitivity (3 cyc/deg) improvement after capsulotomy. Letter-based tests showed better agreement and lower variance than gratings tests. Visual acuity and contrast sensitivity improvement were poorly correlated. CONCLUSIONS: This study shows that contrast sensitivity is adequately documented by a single measurement at 3 cyc/deg, is an informative supplement to visual acuity, and that little extra information is to be gained by measuring further spatial frequencies in eyes with PCO. Peak contrast sensitivity is best determined using a letter-based test.

Aged↗
PubMed1999

[Color vision in relation to age: a study of normal values].

BACKGROUND: It is difficult to quantify thresholds in most colour vision tests, and this is especially the case for tritan hues, where a strong age-related increase of threshold has been reported. With the development of computer-graphic methods it is possible to remove brightness clues caused by lens absorption. This study attempts to give normative values for colour contrast thresholds and assess the age related changes therein. PATIENTS AND METHODS: 115 patients aged between 6 & 71 years were tested for central and peripheral colour contrast sensitivity. No patient had any systemic or eye disease. As a preliminary, heterochromatic flicker balance between the luminosities of the R and G and B and G phosphors was established, so that all colours subsequently generated were isoluminant for the person tested. Then, using a modified binary search technique, colour contrast thresholds were established using both 2 degree optotypes, for central vision, and a ring, 12.5 degrees in radius for peripheral vision. In the latter case, the observer had to name the position of the missing quadrant in the ring. Stimuli were presented for 200 msec at 1 Hz. Colours were modulated on protan, deutan or tritan colour axis. RESULTS: No correlation between age and central colour vision thresholds was observed. By contrast a significant but only minor increase of peripheral colour vision threshold was observed for the peripheral protan and tritan axis. DISCUSSION: The present system removes luminance clues from colour vision tests and permits both central and peripheral retina to be tested. The results are simple in that the influence of age can be neglected. The variability of threshold results is small, and it is easy to detect the relatively large changes associated with disease. Since high-quality monitors are standardised and calibrated, providing the stimulus parameters described are adhered to, the results given here for upper limits of normal may be used for other similar systems.

Adolescent↗
PubMed1998

Does dark adaptation exacerbate diabetic retinopathy? Evidence and a linking hypothesis.

The paper reviews evidence that before any change in diabetics' fundi, changes occur to blood flow, ERG and visual functions. In the case of colour vision and contrast sensitivity, the changes are partially reversed by breathing oxygen, and therefore are the result of retinal hypoxia. There are also other evidences that hypoxia is a major factor in the development of diabetic retinopathy (DR). Therefore in diabetics with early retinopathy, but normal photopic vision, functional disturbance might appear in dark adaptation, since in such circumstances, (as shown by Linsenmeier and his colleagues) the already low retinal PO2 markedly decreases. This hypothesis has been tested and results consistent with the hypothesis (and with a number of older reports) have been obtained. The significance of this finding to early DR is discussed, and a mechanism suggested whereby prolonged periods of hypoxia during dark adaptation could generate changes in retinal capillaries. Such periods occur each night, and their elimination in diabetics could be therapeutic.

Adult↗
PubMed1998

Incidence of idiopathic full-thickness macular holes in fellow eyes. A 5-year prospective natural history study.

PURPOSE: This study aimed to determine the incidence of idiopathic full-thickness macular hole (FTMH) in normal fellow eyes and to evaluate the role of electrodiagnostic and psychophysical tests in identifying eyes at risk. PATIENTS AND METHODS: A prospective longitudinal natural history study of a cohort of patients with unilateral holes and normal, asymptomatic fellow eyes without posterior vitreous detachment was conducted. Subjects underwent baseline examination, pattern reversal electroretinography, electro-oculography (EOG), and color contrast sensitivity (CCS) testing for protan, deutan, and tritan thresholds and were recalled for clinical examination at 18 months and 5 years. RESULTS: At baseline, 114 patients were examined. Eighty were available for review at 18 months, of whom 6 had full-thickness macular holes develop in the fellow eye. At 5 years, 67 of the remaining 74 patients who had not developed holes at 18 months were re-examined and a further 5 were found to have holes develop in the fellow eye. A posterior vitreous detachment without hole formation had developed in 20 fellow eyes at 5 years. Although mean pattern reversal electroretinography and EOG responses were within normal limits in affected and fellow eyes at baseline, mean CCS protan, deutan, and tritan thresholds were elevated significantly in affected eyes at baseline (P = 0.0001). Unaffected fellow eyes showed normal mean protan and deutan thresholds, but significantly elevated mean tritan thresholds (P = 0.01) at baseline. Mean tritan CCS loss was, however, similar in fellow eyes in which holes later developed and in fellow eyes in which holes did not. CONCLUSIONS: The Kaplan-Meier estimated risk of fellow eye involvement is 15.6% (range, 8.4%-22.3%; P = 0.05) at 5 years. Although electrodiagnostic and psychophysical testing was not predictive of fellow eye involvement, tritan CCS loss at baseline, in apparently normal fellow eyes, may indicate subclinical foveal dysfunction, the nature of which is unclear.

Adult↗
PubMed1998

Comparison of methods to assess visual impairment from glare and light scattering with posterior capsule opacification.

PURPOSE: To compare 2 glare tests to determine their relative usefulness in the assessment of posterior capsule opacification (PCO) and to evaluate the potential benefits of combined visual, acuity, contrast sensitivity, and glare testing. SETTING: Teaching hospital ophthalmology department. METHODS: Sixteen patients had glare, visual acuity, and contrast sensitivity testing before and after neodymium:YAG (Nd:YAG) capsulotomy. Results with the Brightness Acuity Tester (BAT, Mentor), which measures disability glare, and the Straylightmeter (Foundation for Eye Research, The Netherlands), which quantifies forward scatter by direct compensation techniques, were compared. The correlation between glare, ETDRS visual acuity, and Pelli-Robson contrast sensitivity was determined. RESULTS: Pretreatment visual acuity was significantly correlated with contrast sensitivity (P < .01). However, visual acuity and contrast sensitivity were poorly correlated with both the BAT and Straylightmeter (P > .05), indicating that visual acuity is predictive of contrast sensitivity but a poor predictor of glare. Glare was significantly improved (Straylightmeter, P < .0001; BAT, P < .05) following capsulotomy. While the Straylightmeter consistently measured precapsulotomy forward scatter that improved with treatment, corresponding BAT disability glare was unmeasurable in 18.8% of patients with PCO, as their visual acuities improved rather than deteriorated with glare testing. CONCLUSIONS: Glare testing provided more information than contrast sensitivity when combined with visual acuity in the evaluation of PCO. Glare related to PCO is better assessed using the Straylightmeter because the BAT may yield aberrant disability glare results.

Aged↗
PubMed1998

Solar retinopathy. A study from Nepal and from Germany.

319 patients with a solar retinopathy were seen in an eye clinic in Nepal within 20 months. All patients had either a positive history of sun-gazing or typical circumscribed scars in the foveal area. In more than 80% of the patients the visual acuity was 6/12 or better and did not deteriorate over time. 126 (40%) patients had a history of gazing at the sun during an eclipse, 33 (10%) were sun worshipers and 4 (1%) were in both categories. Three years later 29 patients were re-examined in a follow-up study. Only 16 had had visual disturbances directly after they had gazed into the sun. No colour vision defects were seen in any of the 44 affected eyes, when tested with Panel D 15, while four patients (6 eyes) had some uncertainty with the tritan plates of the Ishihara test charts. Metamorphopsia were recorded in 11 eyes. Five German patients with solar retinopathy were examined in more detail. Colour contrast sensitivity (CCS) was tested for the central and the peripheral visual field. CCS for tritan axis was raised in all patients for the central visual field, while it was normal for the peripheral visual field.

Adolescent↗
PubMed1997

An epidemic of optic neuropathy in Tanzania: characterization of the visual disorder and associated peripheral neuropathy.

An epidemic of subacute bilateral visual failure has affected large numbers of teenagers and young adult Africans in coastal Tanzania since 1988. Previous work had indicated that many patients had sensory symptoms, but the nature of the neurological involvement was uncertain. The primary objective of this study was to characterize the accompanying neurological disorder. Furthermore, the nature of the visual loss was uncertain from previous reports as both retinopathy and optic neuropathy had been suggested. Full ophthalmic and neurological examinations were carried out at the Muhimbili University Hospital in Dar es Salaam. Nerve conduction studies, pattern electro-retinograms and cortical visually evoked responses and colour contrast sensitivity tests were carried out. Thirty eight young Africans and 12 controls were included in the study. The characteristic fundus picture was symmetrical temporal optic atrophy, and thinning of the caeco-central nerve fibre layer. Fluorescein angiography was normal. The electrophysiological and colour contrast sensitivity tests confirmed optic neuropathy in the majority of cases but primary retinal involvement was indicated in some. Neurological examination and nerve conduction measurements showed evidence of a peripheral neuropathy in 47% of the patients. The peripheral neuropathy is likely to have involved large fibres (from the nerve conduction studies) but the symptoms suggest small fibre loss also. 42% had developed hearing loss. Urinary thiocyanate levels were uniformly low. Serum was negative for antibodies to HTLV-1. DNA analysis from three cases was negative for three known mutations associated with Leber's hereditary optic atrophy (11778, 3460 and 14484). This entity, occurring predominantly in a young age group, does not correspond closely to other tropical neurological syndromes previously described from East Africa although it is clinically very similar to Strachan's syndrome (originally described in the Caribbean and more recently in prisoners of war) and also to an epidemic of optic and peripheral neuropathy that has recently occurred in Cuba. The aetiology has not yet been determined. A micronutrient deficiency is likely but has not been established.

Adolescent↗
PubMed1997

Partial reversal of protan and tritan colour defects with inhaled oxygen in insulin dependent diabetic subjects.

AIMS: Abnormalities in colour perception occur early in the development of diabetic retinopathy. Whether these changes can be influenced by increasing circulating oxygen saturation was studied in comparison with non-diabetic controls. METHODS: Protan and tritan colour thresholds were measured using a computer graphics system in 37 insulin dependent diabetic subjects, with no or minimal background retinopathy, and 27 matched controls. Colour thresholds were performed after subjects inhaled either gaseous air or 100% oxygen for a minimum of 5 minutes. RESULTS: Diabetic subjects had higher colour vision thresholds when inhaling air when compared with controls (protan (mean 3.93 (SEM 0.39), v 2.36 (0.16), p < 0.0002) and tritan (8.15 (0.62) v 5.42 (0.31), p < 0.002)). The colour vision thresholds observed in diabetic subjects inhaling air fell when they inhaled oxygen (protan (3.93 (0.39) v 3.57 (0.33), p < 0.025) and tritan (8.15 (0.62) v 7.35 (0.59), p < 0.005)). No fall in colour thresholds was seen in non-diabetic controls who inhaled oxygen. CONCLUSION: A small improvement in the colour vision thresholds was observed using computer graphics in diabetic subjects, with minimal or no retinopathy, who inhaled oxygen. This study supports a hypothesis that reduced retinal oxygenation contributes to the colour vision defects in diabetes.

Adult↗