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Blue Stimulus (blue + stimulus)
Selected AbstractsComparison of chromatic macular ERG and multifocal ERG in diabetic macular edemaACTA OPHTHALMOLOGICA, Issue 2007MA ARAKELYAN Purpose: To evaluate the degree of macular function disturbances in patients with diabetes mellitus and high glycosylated haemoglobin (HbA1c). Methods: 11 patients with type II diabetes were included in our study. In 6 patients a clinically significant macular edema was detected; other 5 patients showed slight vascular changes and absence of macular pathology. All patients had much too high (8-10%) or extremely high (above 10%) levels of HbA1c and underwent a chromatic macular ERG test to red, green and blue stimuli (MBN, Russia). A RETIScan system for multifocal ERG was also used (Roland Consult, Germany). Results: Patients with macular edema and long duration of the disease had significant reduction of a- and b-wave amplitudes of macular ERG, whereas those with short duration of diabetes showed slight decrease of macular ERG amplitude. The density of photoreceptors in multifocal ERG and amplitudes of N1 and P1 components were analyzed in area of 15° of visual angle: the mean of 3 central rings' values was calculated. Correlation between mf-ERG data and macular ERG amplitudes were found. In patients without macular edema and duration of the disease from 7 to 10 years who had background diabetic retinopathy no significant changes of function testing of the macula were revealed. The amplitude values were close to lower normal data. Conclusions: Macular function in diabetic patients is mainly safe in spite of high levels of glycosylated haemoglobin. The complexity of pathogenetic mechanisms of diabetic retinopathy along with functional tests is still the subject of an investigation. [source] Just how useless is an amblyopic eye?OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Eve Panesar Purpose:, The extent to which individuals with amblyopia are visually disadvantaged has generated renewed research interest. Investigation of the contribution of the amblyopic eye to visual performance under habitual conditions is a key component of this issue. This study aims to evaluate the contribution of each eye to a simple light detection task when both eyes are open and in their habitual motor position. Methods:, A custom program on the Humphrey Field Analyzer (Carl Zeiss Meditec Inc., Dublin, CA, USA) was used to measure detection thresholds for a blue light on a yellow background along the horizontal meridian at two degree intervals to an eccentricity of 25 degrees either side of fixation. Three viewing conditions were used: (1) both eyes open, (2) a yellow filter in front of the amblyopic eye and (3) a yellow filter in front of the fellow eye. The purpose of the yellow filter was to produce minimal dissociation as it only prevented the eye behind the filter from seeing the blue stimulus; the fixation mark and the background remained visible to both eyes. Participants included 10 visual normals and 16 volunteers with amblyopia. Results:, Within the sample of amblyopes there were three basic patterns of results, and each applied to around one third of the group: (1) habitual sensitivity governed by the sensitivity of the fellow eye at each stimulus location, (2) habitual sensitivity exceeding the sensitivities of either eye at each stimulus location and (3) a pattern of contribution that varied across the range of eccentricities. Surprisingly, in one amblyope the habitual sensitivity appeared to be governed by the sensitivity of the amblyopic eye. The pattern of contribution of each eye to the habitual sensitivity did not vary in a manner that was predictable by the visual acuity deficit or the presumed aetiology of the amblyopia. The control sample showed either pattern 2 (70%) or pattern 3 (30%). Conclusions:, The amblyopic eye did not contribute to the habitual performance in approximately one-third of cases in this simple detection task. Thus, in many cases the amblyopic eye may be a useful contributor to visual performance in the binocular field. This challenges the traditional view that an amblyopic eye is useful only for peripheral vision. [source] The prevalence of suppression in amblyopic individualsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Brendan Barrett Purpose:, A popular view of visual functioning in individuals with amblyopia is that the weaker eye is suppressed in key regions of the binocular visual field. Indeed, some have argued that chronic interocular suppression may represent the cause of amblyopia. Here we evaluate the prevalence of amblyopic-eye suppression in a simple light detection task when the eyes are open, minimally dissociated and in their habitual motor position. Methods:, A custom program on the Humphrey Field Analyzer (Carl Zeiss Meditec Inc., Dublin, CA, USA) was used to measure detection thresholds for a blue light on a yellow background along the horizontal meridian at two-degree intervals to an eccentricity of 25 degrees on either side of the fixation mark. The fellow eye was prevented from seeing the target using three different methods: (1) full-occlusion (i.e. no light entered the fellow eye), (2) a translucent occluder (3) a yellow filter in front of the fellow eye. In (3), the yellow filter only prevented the fellow eye from seeing the blue stimulus; the fixation mark and the background remained visible (minimal-dissociation condition). Fourteen amblyopes participated in the study, of whom 11 had strabismus. Results:, Three basic patterns of results were observed. (1) Only three of the fourteen participants (,21%) showed evidence of suppression, where amblyopic-eye sensitivity was lower with the fellow eye open. In these cases, the retinal locations that showed greatest suppression corresponded to the direction and angle of the strabismus. (2) Three participants (,21%) showed the opposite effect to the result in (1); i.e. amblyopic-eye sensitivity was greatest when the fellow was open with minimal dissociation between the eyes. One possible explanation is that the dominance of the fellow eye caused this reduction. (3) Seven participants (50%) exhibited patterns of amblyopic sensitivity that did not depend upon the occlusion status of the fellow eye. The results for one participant did not fit into any of the above patterns. Conclusions:, Suppression appears not to be a universal feature of central amblyopic vision. Our results for this simple detection task suggest that suppression may exist in as few as 20% of amblyopes. These results present a challenge to the view that suppression represents a root cause of amblyopia but they are consistent with the view that the amblyopic eye makes a useful contribution under habitual viewing conditions. [source] Short wavelength automated perimetryACTA OPHTHALMOLOGICA, Issue 6 2001John M. Wild ABSTRACT. Short Wavelength Automated Perimetry (SWAP) utilizes a blue stimulus to preferentially stimulate the blue cones and a high luminance yellow background to adapt the green and red cones and to saturate, simultaneously, the activity of the rods. This review describes the theoretical aspects of SWAP, highlights current limitations associated with the technique and discusses potential clinical applications. Compared to white-on-white (W-W) perimetry, SWAP is limited clinically by: greater variability associated with the estimation of threshold, ocular media absorption, increased examination duration and an additional learning effect. Comparative studies of SWAP and W-W perimetry have generally been undertaken on small cohorts of patients. The conclusions are frequently unconvincing due to limitations for SWAP in the delineation of abnormality and of progressive field loss. SWAP is almost certainly able to identify glaucomatous visual field loss in advance of that by W-W perimetry although the incidence of progressive field loss is similar between the two techniques. Increasing evidence suggests that functional abnormality with SWAP is preceded by structural abnormality of the optic nerve head and/or the retinal nerve fibre layer. SWAP appears to be beneficial in the detection of diabetic macular oedema and possibly in some neuro-ophthalmic disorders. [source] | ||||||||||