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PubMed1975

[Objective determination of accommodation in eyes with permanent central scotoma due to amblyopia (author's transl)].

Objective determination of accommodation in 38 children with permanent central scotoma due to amblyopia on one side (with central and eccentric fixation) revealed: 1. The physiological adaptation of refraction for far and near distances did not serve its purpose. 2. There was either no or an irregular response on hyperopia, which was produced by placing concave lenses in front of the eye while fixing a far object, or on myopia produced by placing convex lenses in front of the eye while fixing a near object. 3. On hindering clear vision which could not be compensated by accommodation there was contrary to normal eyes no reactive change of refraction at all or only a poor one. The accommodation behavior in eyes with permanent central scotoma due to amblyopia does not differ from that in eyes with permanent central scotoma due to organic lesions when using the same test methods.

Accommodation, Ocular↗
PubMed2004

Unveiling the foveal blue scotoma through an afterimage.

The absence of short-wave-sensitive (S-) cones in the human foveola normally goes unnoticed, but the resulting foveal S-cone, or blue, scotoma can be visualized as the negative afterimage of a short-wavelength adapting field on a larger white background. The afterimage has an annular shape with a lighter inner region that corresponds to Maxwell's spot, and a small bright spot in the center corresponding to the foveal blue scotoma. We have shown that the visibility of the center spot in the afterimage approximately follows the spectral sensitivity curve of the S-cones. We further demonstrate that the central bright spot subtends a retinal area that is coincident with the tritanopic region of the foveola. The macular pigment distribution measured for the same observers also peaks in the central fovea, but has a relatively high density over a broader retinal region than the bright spot in the negative afterimage, and more closely corresponds to the lighter annular region of the afterimage. The results support the hypothesis of an active post-receptoral process for filling-in of chromatic scotomas.

Adaptation, Ocular↗
PubMed2001

Filling-in of the foveal blue scotoma.

The blue-blindness (tritanopia) of the human foveola normally goes unnoticed but can be directly visualized by having observers view a flickering, monochromatic, short-wavelength field. The blue scotoma appears as a tiny dark spot in central vision, the visibility of which depends upon the wavelength of the field and the temporal frequency of modulation. Comparisons of fading times as a function of flicker frequency for the blue scotoma, foveal afterimages and optically stabilized images indicate a common time course, consistent with the hypothesis that perceptual filling-in of the foveal blue scotoma reflects the operation of neural processes similar to those involved in fading and regeneration of stabilized images.

Afterimage↗
PubMed1977

Suprasellar tumors and incidental optic disc anomalies. Diagnostic problems in two patients with hemianopic temporal scotomas.

Anomalous optic discs may be associated with relative temporal visual field defects that need to be distinguished from bitemporal field defects of chiasmal compression. Two patients with both anomalous discs and suprasellar tumors were hospitalized with temporal hemianopic scotomatous visual field defects. A 19-year-old woman with a chromophobe adenoma had a monocular temporal hemianopic scotoma in the eye exhibiting an inferior-nasal disc crescent. A 22-year-old man with a hypothalamic-chiasmal germinoma causing bitemporal hemianopic scotomas had minor disc colobomas bilaterally. Careful study of the optic discs and posterior fundus, as well as evaluation of the characteristics of the temporal field defects, should distinguish chiasmal compression in the occasional case where suprasellar tumor and anomalous optic discs coincide.

Adenoma, Chromophobe↗
PubMed1993

A cluster and scotoma analysis based on empiric criteria.

From a collection of 288 visual fields of glaucomatous or glaucoma suspects, 30 were selected at random and were analyzed by one expert interpreter. Visual field damage varied from nonexistent to severe. The interpreter defined clusters or scotomas subjectively according to adjacency criteria: adjacent test locations which exceeded a critical loss value were grouped as clusters or scotomas. A computer algorithm has been devised which simulates such evaluation methods. In general, a standard setting of several parameters produced a cluster display containing the same number of clusters as determined by the expert interpreter. Another display mode grouped clusters according to polygonal areas of a predetermined size (Voronoi diagram). Due to the broad selection of visual field defects, the specificity of the program with regard to various field decay patterns was small and it should thus be applicable to a broad spectrum of glaucomatous field damage.

Algorithms↗
PubMed2005

Transcranial magnetic stimulation in the visual system. II. Characterization of induced phosphenes and scotomas.

Transcranial magnetic stimulation (TMS) induces phosphenes and disrupts visual perception when applied over the occipital pole. Both the underlying mechanisms and the brain structures involved are still unclear. In the first part of this study we show that the masking effect of TMS differs to masking by light in terms of the psychometric function. Here we investigate the emergence of phosphenes in relation to perimetric measurements. The coil positions were measured with a stereotactic positioning device, and stimulation sites were characterized in four subjects on the basis of individual retinotopic maps measured by with functional magnetic resonance imaging. Phosphene thresholds were found to lie a factor of 0.59 below the stimulation intensities required to induce visual masking. They covered the segments in the visual field where visual suppression occurred with higher stimulation intensity. Both phosphenes and transient scotomas were found in the lower visual field in the quadrant contralateral to the stimulated hemisphere. They could be evoked from a large area over the occipital pole. Phosphene contours and texture remained quite stable with different coil positions over one hemisphere and did not change with the retinotopy of the different visual areas on which the coil was focused. They cannot be related exclusively to a certain functionally defined visual area. It is most likely that both the optic radiation close to its termination in the dorsal parts of V1 and back-projecting fibers from V2 and V3 back to V1 generate phosphenes and scotomas.

Adult↗
PubMed2005

The relationship between word length and threshold character size in patients with central scotoma and eccentric fixation.

BACKGROUND: Understanding limitations on text reading with eccentric fixation is of major concern in low vision research. Our objective was to determine, in patients with a central scotoma, whether threshold character size is similar for different word lengths and paragraphed texts. METHODS: In 19 patients, we retrospectively analyzed the relationship between minimum readable character size for isolated words and text. Isolated letters, two, five, and ten-letter words and a paragraphed text were presented randomly through a scanning laser ophthalmoscope in eight different character sizes. RESULTS: Threshold character size varied according to the text stimulus (p<0.05). Threshold character sizes for single letters and two-letter words were matched (p>0.99), as were those for five-letter words, ten-letter words, and paragraphed text (p>0.99). Threshold character size for single letters and two-letter words was significantly lower than that measured with other text stimuli. DISCUSSION: Reading performance is influenced by a variety of factors such as crowding, contextual effects, visual span, degree of oculomotor adaptation needed, and frequency of a defined word. Globally, when reading with a central scotoma, it appears that within word characteristics have more impact than inter-word parameters on threshold character size.

Adult↗
PubMed2006

The irvine prism test: does the positive response indicate suppression scotoma?

PURPOSE: To investigate whether the positive prism test response is due to the presence of a suppression scotoma or the absence of bifoveolar fixation. METHODS: Fifty-one subjects with esotropia (microtropia, small-, moderate- or large-angle esotropia), and 22 subjects with nonstrabismic anisometropic amblyopia were examined. The prism test was performed by using base-out prisms of two different powers (4-PD and 30-PD), and base-in prism of 20-PD, as well as base-down prism of 10-PD for each subject. RESULTS: All the subjects with esotropia showed a positive prism test response, whereas all the subjects with nonstrabismic anisometropic amblyopia had a negative prism test response. All the esotropic subjects showed positive response to all magnitudes and positions of the prisms tested. CONCLUSIONS: The positive response to the prism test does not indicate suppression scotoma in subjects with microtropia and small-angle esotropia because all the esotropic subjects showed the positive response regardless of the amount of deviation or the sensorial adaptation mechanisms. Also, the positive response, seen in the esotropic subjects, did not alter to negative by using the prisms of different powers and directions.

Adolescent↗
PubMedDate not supplied

Significance of scintillating scotoma of late onset.

Scintillating hemianopic scotomas are usually caused either by migraine or, more rarely, vertebral-basilar insufficiency. We report two patients in whom this symptom was probably caused by platelet microthrombi in pial vessels of the visual cortex. These patients were similar in that they had scintillating scotomas which began after the age of fifty and abnormal platelet aggregability. Since increased platelet aggregability is associated with cerebral vascular accidents and is treatable, older patients who develop teichopsias should have appropriate hematological tests.

Age Factors↗
PubMed1993

Is there a systematic location for the pseudo-fovea in patients with central scotoma?

The retinal location of preferential fixations of twenty-four patients with central scotoma were studied when reading digits projected onto their retina with a scanning laser ophthalmoscope. In the majority of cases the fixation was located on the left part, or the inferior part of the visual field relative to the central scotoma. The fact that the inferior visual field is used is coherent with the notion that the lower visual field is important for locomotion. However the preferential use of the left field appears contradictory with data showing superiority of visual faculties in the right visual field. This result may possibly be explained in relation to the need for left-to-right readers to monitor where their eyes have landed relative to the word previously fixated on the left.

Adult↗
PubMed2001

Cortical plasticity revealed by circumscribed retinal lesions or artificial scotomas.

We review the work of others in which the effects of circumscribed, topographically corresponding binocular retinal lesions on the topographic organization of the visual cortex revealed that there is a substantial degree of topographical plasticity in the primary visual cortices of adult cats and macaque monkeys. Despite the evidence indicating that the reorganization of the topographic map in primary visual cortices of adult cats and macaques related to the input from one eye could be suppressed for a long time by inputs related to the other eye, we observed a substantial degree of topographical plasticity in the primary visual cortices of adult cats in which we have made circumscribed monocular retinal lesions. Overall, in both binocularly and monocularly lesioned adult animals, most cells recorded in the cortical projection zone of the retinal lesion (LPZ), several hours, several weeks or several months after placement of the lesions exhibited 'ectopic' excitatory visual receptive fields (RFs) which were displaced to the normal retina in the immediate vicinity of the lesion. The presence of ectopic RFs in cells recorded in the cortical LPZ, combined with the presence of normal cortical representation of the part of the retina in the vicinity of the lesion, indicate a clear expansion of the cortical representation of the part of the retina surrounding the lesion. When stimulated via the ectopic RFs, cortical cells exhibited normal orientation tuning and in the case of animals with monocular lesions, the orientation tuning of binocular cells when stimulated via ectopic RFs appeared to be very similar to that when the cells were stimulated via the RFs in the normal, unlesioned eye. In both binocularly and monocularly lesioned animals, the responses evoked by optimal visual stimuli from the ectopic RFs were substantially weaker than those evoked from their normal counterparts. Similarly, upper velocity limits were significantly lower when visual stimuli were presented via the ectopic RFs. In contrast to cats in which the retinal lesions were made in adulthood, in cats lesioned monocularly in adolescence (8-11 weeks postnatal), both the peak discharge rates and upper velocity limits of responses to photic stimuli presented via the ectopic RFs were very similar to those to stimuli presented via the normal eye. The intracortical mechanism(s) underlying the long-term cortical plasticity revealed by retinal lesions are likely to be closely linked to the mechanism(s) underlying the short-term reversible enlargement of cortical receptive fields observed with artificial scotomas. Furthermore, a similar putative intracortical mechanism(s) appears to underlie psychophysical phenomena observed in studies of retinal scotomas in humans. Overall, the research reviewed here strongly challenges the view that receptive fields of neurons in mammalian visual cortices are 'hard-wired'.

Animals↗
PubMed1991

Fluctuation of the differential light threshold at the border of absolute scotomas. Comparison between glaucomatous visual field defects and blind spots.

The outcome of repeated measurements of the differential light sensitivity fluctuates slightly. This fluctuation can be markedly increased in glaucoma patients but has also been described at the border of the blind spot of healthy subjects. The question arises, therefore, whether in glaucoma this increase may be due to the fact that many test locations may touch the border of (detected or undetected) scotomas. This study compares the behavior of the threshold at the border of glaucomatous defects and blind spots. The threshold was measured with program F8 of the Octopus 201 (Interzeag, Inc, Schlieren, Switzerland) automated static perimeter. The results revealed that the borders of glaucomatous defects are less steep than those of blind spots, the fluctuation is largest just at the border of the scotomas in both groups, and that the fluctuation is significantly larger at the edge of glaucomatous defects than at the edge of blind spots of normal subjects.

Glaucoma, Open-Angle↗
PubMed2000

Entoptic perimetry screening for central diabetic scotomas and macular edema.

OBJECTIVE: The aim of this study was to compare entoptic perimetry, using conventional television, to Amsler grid and patient-reported visual loss for the detection of functional diabetic maculopathy and macular edema. DESIGN: Observational case series. PARTICIPANTS: A single eye from each of 104 consecutive patients with diabetes in an academic retina clinic. INTERVENTION: Each eye was screened by Amsler grid, entoptic perimetry, and Humphrey 10-2 threshold visual field testing (HVF 10-2; Humphrey Instruments Inc., San Leandro, CA) in random order. Eyes were then examined clinically. MAIN OUTCOME MEASURES: The presence or absence of new visual decline since the patient's last clinical examination, the presence or absence of central visual field abnormalities using an Amsler grid, entoptic perimetry, HVF 10-2, and the presence or absence of clinically significant macular edema (CSME). RESULTS: The sensitivities and specificities for the detection of central diabetic scotomas as evidenced by HVF 10-2 abnormalities were: subjective impression, 31 of 90 eyes (34.4%) and 11 of 14 eyes (78.6%); Amsler grid, 29 of 90 eyes (32.2%) and 13 of 14 eyes (92.9%); and entoptic perimetry, 58 of 90 eyes (64.4%) and 11 of 14 eyes (78.6%). Entoptic perimetry was statistically more sensitive than both subjective impression (P < 0.001) and Amsler grid (P < 0.001), but the specificities were statistically indistinguishable. The sensitivities and specificities for the detection of CSME were: subjective impression, 6 of 24 eyes (25.0%) and 52 of 80 eyes (65.0%); Amsler grid, 9 of 24 eyes (37.5%) and 59 of 80 eyes (73.8%); and entoptic perimetry, 17 of 24 eyes (70.8%) and 44 of 80 (55.0%) eyes. These results are also statistically significant, with entoptic perimetry being more sensitive and less specific than both subjective impression (P = 0.007 and P = 0.011, respectively) and Amsler grid (P = 0.008 and P < 0.001, respectively) in this subset of patients. CONCLUSIONS: Entoptic perimetry is 87% more sensitive than the subjective impression of visual decline (P < 0.001) and 100% more sensitive than Amsler grid (P < 0.001) for the detection of central scotomas in diabetic patients. For the detection of CSME, entoptic perimetry is 183% more sensitive than subjective impression (P = 0.007) and 89% more sensitive than Amsler grid (P = 0.008). Hence, entoptic perimetry, performed using conventional television, has the potential to be an effective, inexpensive, and widespread adjunct to surveillance examinations for the early detection of diabetic maculopathy.

Adult↗
PubMedDate not supplied

Artificial scotoma-induced perceptual distortions are orientation dependent and short lived.

Conditioning human observers with an "artificial scotoma"-a small retinal area deprived of patterned stimulation within a larger area of dynamically textured noise-results in contractions and expansions of perceived space that are thought to reflect receptive-field changes among cells in the primary visual cortex (Kapadia et al., 1994). Here we show that one-dimensional counter-phase flickering grating patterns are also potent stimuli for producing artificial scotomata capable of altering three-element bisection ability analogous to those results reported earlier. Moreover, we found that the magnitude of the induced spatial distortions depends critically on the relative orientations of peri-scotomatous and test-stimulus spatial contrast. In addition, the perceptual distortions are found to be relatively short lived, decaying within 660 ms. The results support the hypothesis that artificial scotoma-induced perceptual distortions are generated by dynamic alteration of connection efficacy within a network linking cortical areas of similar orientation specificity, consistent with established anatomical and physiological results.

Humans↗
PubMed1995

Responses of cells in monkey visual cortex during perceptual filling-in of an artificial scotoma.

When we view a scene through one eye, we typically do not see the scotomas created by the optic disc and the blood vessels overlying the retinal surface. Similarly, when a texture field containing a hole is steadily viewed in peripheral vision (artificial scotoma), the hole appears to fill in with the surrounding texture in a matter of seconds, demonstrating that the visual system fills in information across regions where no information is available. Here we show that, in monkeys viewing a similar texture field with a hole, the responses of extrastriate visual neurons with receptive fields covering the hole increase gradually to a level comparable to that elicited by the same texture without a hole. The time course of these dynamic changes in activity parallels the time course of perceived filling-in of the hole by human observers, suggesting that this process mediates perceptual filling-in.

Animals↗
PubMed2004

[Correlation between glaucomatous hemifield scotomas in white-on-white perimetry and blue-on-yellow perimetry using the oculus twinfield perimeter].

INTRODUCTION: The "Twinfield Perimeter" can be used for white-on-white and blue-on-yellow perimetry. Since the normative database which is used fort the calculation of the visual field indices for both strategies is based on data from white-on-white perimetric evaluations of normal persons using the "Tübinger Automatikperimeter", the validity of this approach may be questioned. In the study presented here we compared the correlation of white-on-white (W/W) and blue-on-yellow (B/Y) visual fields in glaucoma patients with a hemifield scotoma. PATIENTS AND METHODS: One eye each from 40 normal persons and from 40 glaucoma patients was included in the study. Both W/W-perimetry and B/Y-perimetry was performed using the "Twinfield Perimeter" (Oculus, Modell 56 900, Wetzlar, Germany). From the sensitivity values determined with the 30/2 strategy, we calculated the mean sensitivity (MS), mean deviation (MD) of the total field and of both hemifields (HMS bzw. HMD) separately. Normal values derived from the normal persons of the present study were compared with the normal values used by the Twinfield Perimeter. To determine the strength of the association of B/Y- and W/W-hemifield scotoma, we calculated the linear correlation coefficient (Pearson's R) between the HMD of B/Y und W/W-hemifields. RESULTS: MS of both glaucoma patients and normal persons were determined to be significantly higher for B/Y visual fields (14.17 +/- 4.15 and 20.97 +/- 3.56) when compared with W/W-visual fields (10.70 +/- 3.19 or 15.98 +/- 3.3). When normal values from the Twinfield Perimeter were applied, the MD for normal persons was calculated to be - 4.69 +/- 3.22 compared with 0 +/- 3.6 when the MD was calculated with the normal values from the study. For both normal values we confirm a strong correlation between HMD-values of W/W- and B/Y-visual fields. CONCLUSIONS: Since the mean sensitivity of B/Y visual fields is higher than the mean sensitivity of W/W visual fields, calculations of the MD of B/Y visual fields of glaucoma patients should be based on normative databases which are derived from B/Y visual fields of normal persons.

Aged↗
PubMed1982

[Parafoveolar scotomas in microinfarcts of the optic pathways (author's transl)].

Small parafoveolar scotomas in microinfarction of the optic pathways are often not demonstrated, or only inaccurately so, in conventional kinetic perimetry. By using Amsler's grid it is possible to determine accurately the shape and position of such visual field defects. Some remarkable variants of these scotomas are described.

Adult↗
PubMed1992

Xanthic scotoma and yellow foveolar shadow caused by a pseudo-operculum after vitreofoveal separation.

The biomicroscopic detection of a small opacity (pseudo-operculum) suspended in front of the normal foveal retina is a sign of vitreofoveal separation. This report concerns five patients in whom slit-lamp illumination of the pseudo-operculum produced a yellow spot (shadow) on the adjacent pigment epithelium. This occurred in two patients who presented because of a small yellow central scotoma. In one patient, the yellow spot and scotoma disappeared after complete posterior vitreous separation. One patient presented because the referring physician misinterpreted the yellow spot as a Stage 1 impending macular hole.

Aged↗