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PubMed1987

A study of the value of the central and peripheral isoptres in assessing visual field progression in the presence of paracentral scotoma measurements.

The visual field records of 45 eyes of 45 patients were evaluated to determine whether examination of the peripheral field of vision in patients with glaucoma and field defects adds useful information about the progression of visual field damage. The central scotoma mass, foveal sensitivity, and the central and peripheral mass of the visual field were quantified from measurements on the Tübinger perimeter. Most of the information on visual field progression was contained in the scotoma mass. When both scotoma mass and foveal sensitivity were known, central or peripheral isoptres did not add statistically significant information on progression. Evaluation of scotomas and assessment of central isoptres or of foveal sensitivity made perimetry of the peripheral isoptres redundant. The appearance of fresh peripheral scotomas or the quantification of changes in peripheral scotomas was not examined in the current study, and they would of course be important when they occurred.

Adult↗
PubMed2006

Oculomotor tracking strategy in normal subjects with and without simulated scotoma.

PURPOSE: Experiments were conducted on five subjects with no visual impairment to assess tracking strategy differences in subjects with and without a simulated central scotoma. METHODS: Subjects were asked to visually track horizontally moving periodic and nonperiodic sinusoidal stimuli through a +/-5 degrees range. Scotoma simulation was achieved electronically with a closed-loop feedback system using horizontal eye movement measurements from a monocular limbus eye tracker updated at a rate of 500 Hz. The scotoma was centrally located and had defined horizontal half widths of 1, 2, and 3 degrees . Vertical eye position measurements from a video-based dark-pupil tracker were used to identify and remove trials in which extreme vertical eye position deviations reduced the effectiveness of the simulation. RESULTS: All subjects developed a preferred retinal locus (PRL) in the left visual field and demonstrated a tendency for saccadic redirection to this area. Saccadic endpoints into the PRL outnumbered foveally directed saccades by a factor of 2:1. The PRL was located outside the compromised central vision region, typically near the edge of the scotoma boundary, for all subjects except one. This subject had a PRL within the simulated scotoma under two conditions, but the percentage of total time spent at the "compromised" PRL was less than for other subjects. CONCLUSIONS: Subjects with no visual impairment confronted with a central scotoma develop a preferred retinal locus to replace the nonfunctional fovea and appear to suppress normal refoveating saccadic behavior in favor of this location.

Adult↗
PubMed2003

Modified astigmatism dial diagram for locating eccentric fixation in patients with central scotoma.

PURPOSE: Patients with central scotoma often develop eccentric fixation on a preferred retinal locus (PRL). Identifying the PRL is one of the first steps in low vision rehabilitation training. We present our evaluation of a simple test designed to locate the eccentric fixation in eyes with central scotoma. METHODS: This was a prospective case series of consecutive patients with age-related macular degeneration and bilateral central scotoma. A numeral was added in the center of an astigmatism dial diagram. After one eye was patched, patients with central scotoma were asked to fixate the dial and describe it, then to look at the 12 o'clock position, and then around the clock. The eccentricity at which the central numeral was best seen was compared with the one determined by scanning laser ophthalmoscopy (SLO). The modified astigmatism dial test and SLO were done independently by two masked investigators. The results of the two methods were expressed in clock hour positions and were considered to be in agreement when they did not differ by more than one hour. RESULTS: Nine consecutive patients (18 eyes) with severe age-related macular degeneration and bilateral central scotoma were tested. The six women and three men ranged in age from 61 to 86 years (mean 75.8 years). The pattern test correlated with SLO findings in 12 (66%) of the 18 eyes. When considering the best-seeing eye of each patient, results showed agreement in eight (88%) out of nine cases. CONCLUSIONS: The modified astigmatism dial test appears useful for establishing the location of the eccentric fixation in the best-seeing eye of patients with bilateral central scotoma, allowing visual rehabilitation training to be started without delay.

Aged↗
PubMed1987

Simulation of a retinal scotoma by a stabilized retinal image.

Two methods are described for simulating a retinal scotoma by means of a stabilized retinal image, hence allowing some aspects of the impairment of visual function associated with scotomas to be studied in observers with normal visual fields. In the first method, an optical lever arrangement is used to generate a small artificial scotoma at a controllable position with 15 degrees field of view. The second, direct attachment, method uses a tight-fitting scleral contact lens, to which is attached a very light, aluminium-alloy tube. This carries a small piece of lightweight black card, the stabilized image of this card generating the scotoma. Although precise positioning of the scotoma is more difficult with the second method, the induced scotoma is absolute and the method is relatively cheap and easy to implement.

Contact Lenses↗
PubMed1978

[Scotoma in the binocular field of vision in severe amblyopia and microstrabismus (author's transl)].

Binocular perimetry with Aulhorn's Phase difference haploscope is described. Of 62 patients with primary micro-squint, 21 patients showed no scotoma, 15 patients showed a fixation or zero point scotoma of 0.5-1 degrees, 26 patients showed a larger scotoma (average: 3.7 degrees). In addition, 15 patients with larger angle and deep amblyopia were examined. The scotoma average was 8.8 degrees. A zero point scotoma was always present, whereas the central foveal scotoma was often missing.

Adolescent↗
PubMed1990

Simultaneous pattern reversal ERG and VER recordings. Effect of stimulus field and central scotoma.

The effects of the sizes of the stimulus field and of an artificially created central scotoma on simultaneously recorded pattern-reversal electroretinogram (P-ERG) and pattern-reversal visual-evoked response (P-VER) were investigated. With an increase in the stimulus field from 4 degrees X 4 degrees to 12 degrees X 12 degrees, the amplitude of the P-ERG increased steadily. The amplitude of the P-VER also showed an increase up to a stimulus field of 6 degrees X 6 degrees or 8 degrees X 8 degrees, but showed no increase with further expansion of the stimulus field. A central scotoma, created by placing a square of black paper at the center of the 12 degrees X 12 degrees stimulus field, was increased from 4 degrees X 4 degrees to 10 degrees X 10 degrees by 2-degree increments. Amplitudes of both the P-ERG and the P-VER decreased with increasing central scotoma size. The P-VER decreased significantly with a 4 degrees X 4 degrees central scotoma. Although both the P-ERG and the P-VER were influenced by the overall stimulus field and the central scotoma, there was a distinct difference in their behavior. The P-VER showed saturation above a certain stimulus field size and, with a central scotoma of 4 degrees X 4 degrees, much more reduction than the P-ERG, suggesting that the P-VER depends more on the macular area than does the P-ERG. The P-ERG also exhibited a substantial macular dependency, which, however, was not as great as that of the P-VER. The greater macular dependency of the P-VER compared to the P-ERG, as observed in our study, reflects the larger anatomic representation of the macula at the higher visual level.

Adult↗
PubMed2003

Filling-in phenomenon in patients with age-related macular degeneration: differences regarding uni- or bilaterality of central scotoma.

PURPOSE: The purpose of this study was to explore the presence of the filling-in phenomenon in patients with uni- or bilateral central scotoma (CS) resulting from natural history or laser photocoagulation of choroidal neovascularization in age-related macular degeneration (AMD). METHODS: Sixteen consecutive patients with unilateral CS and 14 patients with bilateral CS were assessed (44 eyes) with a scanning laser ophthalmoscope (SLO). Scotoma was delineated by scotometry with a point (1 degree x1 degree) moving radially from the periphery to the center of the lesion. In addition, patients underwent a line test, consisting of a horizontal line moving vertically and a vertical line moving horizontally, from the periphery to the center. The lines were longer than the macular lesion and were projected onto the retina. Patients were asked to indicate when the lines seemed interrupted. The perceptual filling-in phenomenon was considered to be present when limits of the perceived scotoma, determined by the line test, were smaller than those assessed by scotometry. In patients with bilateral CS, the results were analyzed to distinguish the less or more severely affected eye. RESULTS: In all eyes, the limits of the scotoma obtained with the scotometry test corresponded to the anatomic edges of the macular lesion. In patients with bilateral CS, the filling-in phenomenon was observed in 12 out of 14 (85%) less severely affected eyes, but only in one (7%) of their more severely affected eyes. In patients with unilateral CS, the phenomenon was observed in only one out of 16 (6%) eyes. CONCLUSION: These results suggest that the filling-in phenomenon mostly occurs in patients with bilateral central scotoma, and almost always in their less affected eye. Thus, it did usually not occur in an eye if the fellow eye was better.

Aged↗
PubMed2000

Dynamic random noise shrinks the twinkling aftereffect induced by artificial scotomas.

Physiological alterations in cortical neurons are induced during adaptation to an artificial scotoma, a small homogeneous patch within a dynamic random noise or patterned background. When the dynamic noise is replaced by an equiluminant gray background, a twinkling aftereffect can be seen in the location of the artificial scotoma. Following binocular adaptation, we discovered that the perceived size of the twinkling aftereffect was dramatically smaller than the inducing artificial scotoma. Dichoptic adaptation induced shrinkage in the twinkling aftereffect that was similar to that found after binocular adaptation, suggesting that the twinkling aftereffect and its shrinkage both have cortical origins. We speculate that this perceptual shrinkage may reflect the interaction between two cortical mechanisms: a twinkling aftereffect mechanism that spreads throughout the artificial scotoma, and a filling-in mechanism that has a greater influence at the edges of the artificial scotoma and spreads inwards.

Adaptation, Ocular↗
PubMed1991

Perceptual filling in of artificially induced scotomas in human vision.

Patients with scotomas or blind-spots in their visual field resulting from damage to the visual pathways often report that the pattern from the rest of the visual field 'fills in' to occupy the scotoma. Here we describe a novel technique for generating an artificial perceptual scotoma which enabled us to study the spatial and temporal characteristics of this filling-in process. A homogeneous grey square subtending 1.5 degrees was displayed against a background of twinkling two-dimensional noise of equal mean luminance. On steady eccentric fixation for 10 s the square vanished and was filled in by the twinkling noise from the surround. Using this display we found that 'filling in' is an active visual process that probably involves creating an actual neural representation of the surround rather than merely ignoring the absence of information from the scotoma; filling in can occur separately for colour and texture, suggesting separate mechanisms; the filling-in process does not completely suppress information from the scotoma, even after an image has faded completely from consciousness it can nevertheless contribute to motion perception; and the process can be strongly influenced by illusory contours.

Humans↗
PubMed1995

[The F-L test for determining alternating central scotoma].

BACKGROUND: Based on their experiences several authors consider an alternating central scotoma as the main reason for reading difficulties due to dyslexia. METHODS: Searching for a simple and reliable method for determination of an alternating central scotoma we used a pair of synoptophore fusion images, in the center of which we added the letter F respectively L as central control signs. A spontaneously perceived and persisting E means a perfect and stable orthophoria. A persisting F or L with fusion of the images means a one sided central scotoma. Alternation of F and L with fusion of the images means an alternating central scotoma. RESULTS: By examining normal readers, untreated asthenopic and untreated dyslexic patients, we found mostly rapid alternation of F and L in the latter two groups, whereas most of the normal readers saw F, L and E alternating at longer intervals. CONCLUSIONS: Thus undisturbed reading seems not to demand perfect orthophoria. On the other hand a rapidly alternating central scotoma may be considered as an important factor causing reading difficulties.

Adolescent↗
PubMed2005

Scotomas of age-related macular degeneration detected and characterized by means of a novel three-dimensional computer-automated visual field test.

PURPOSE: We used the recently devised three-dimensional computer-based threshold Amsler grid test to acquire and identify typical patterns of visual field defects (scotomas) caused by age-related macular degeneration (AMD). METHODS: Patients with AMD traced on a computer touch screen the borders of those areas on an Amsler grid that were missing from their field of vision. Scotomas were repeatedly outlined and recorded at different grid contrast levels. The resulting three-dimensional "hole" in the central 25 degrees of the visual field was further characterized by its slope, location, shape, and depth. The results were compared with fundus photographs and fluorescein angiograms. RESULTS: Twenty-five patients and 41 eyes were examined. The three-dimensional depictions consistently demonstrated central scotomas with "scallop"-shaped borders and steplike patterns, with either steep slopes or a combination of steep and shallow slopes. The steep slopes corresponded to nonexudative AMD, while the shallow slopes indicated exudative AMD. CONCLUSION: The three-dimensional computer-automated threshold Amsler grid test may demonstrate characteristic scotoma patterns in patients with AMD that conform to the respective fluorescein angiograms. The test shows promise as an effective tool in accurately evaluating, characterizing, and monitoring scotomas in patients with AMD. It may have the potential as a screening tool for the early diagnosis of AMD.

Aged↗
PubMed2001

Optokinetic nystagmus in patients with central scotomas in age related macular degeneration.

BACKGROUND: Reports on the impact of a loss in the central field of vision on optokinetic nystagmus (OKN) are varied. A study was therefore undertaken to reassess the role of the central retina in the generation of OKN in a large group of patients with age related macular degeneration. METHODS: Four groups of 20 patients were examined: a control group without scotoma and three groups with absolute central scotomas measuring 1 degrees--10 degrees, 11 degrees--20 degrees, and 21 degrees--30 degrees. OKN was elicited with black and white stripes moving nasally to temporally or temporally to nasally on a screen subtending 54 degrees x 41 degrees at four velocities (15, 30, 45, and 60 degrees /s). OKN gain was measured using infrared oculography. RESULTS: There was no significant difference in OKN gain between the control group and those with scotomas of 1 degrees--10 degrees and 11 degrees--20 degrees. A significant difference in OKN gain was found between the group with scotomas of 21 degrees--30 degrees and all other groups at stimulus velocities of 30, 45, and 60 degrees/s (p<0.05). OKN gain significantly diminished with increasing stimulus velocity (p<0.05). No statistically significant difference was found in OKN gain between stimuli moving temporally to nasally and nasally to temporally. CONCLUSION: Abnormalities of OKN gain were noted only in patients with large scotomas. An intact macula is therefore not necessary for the generation of OKN.

Aged↗
PubMed1997

Object identification without foveal vision: evidence from an artificial scotoma paradigm.

The purpose of the present study was to investigate the degree to which foveal information is necessary for object identification. To explore this question, we used an artificial moving scotoma paradigm to eliminate a region of a currently viewed display in real time as a function of eye position. Subjects examined linear arrays of four line drawings of objects while their eye movements were recorded. Immediately following each array, a test probe was presented to test the degree to which the subject had identified those objects. Three conditions were compared, one in which a central foveal scotoma was created, one in which an extrafoveal scotoma was created, and a control condition in which the scotoma was absent. The main result was that identification accuracy was very good, but eye-movement behavior was disrupted when a foveal scotoma was present. These results suggest that foveal information is not necessary but is beneficial for perceptual encoding during object identification; the loss of foveal information can be overcome as long as compensatory extrafoveal processing is possible.

Eye Neoplasms↗
PubMed1997

Using two preferred retinal loci for different lighting conditions in patients with central scotomas.

PURPOSE: Using a scanning laser ophthalmoscope, it was found that some patients with relative central scotomas reliably used two different preferred retinal loci (PRLs) at different stimulus illuminances. This article describes adaptations in a patient's PRL for fixation when dimming the stimulus increased the relative scotoma size. METHODS: Twenty-eight patients with macular diseases had their dense and relative macular scotoma borders mapped with the scanning laser ophthalmoscope. The high-illuminance PRL (PRLhi) and low-illuminance PRL (PRLlo) were operationally defined as the PRLs that patients used to fixate a high or low illuminance stimulus, respectively. The PRLs' abilities to do visual tasks and their characteristics at the corresponding illuminances were assessed. RESULTS: The PRL consistently shifted between the PRLhi and the PRLlo as the stimulus illuminance was changed. Brightness permitting, the visual system prefers to use the PRLhi with generally better performance in visual function such as fixation stability. There were no significant differences between the PRLhi and the PRLlo in pursuit and saccadic abilities, when assessed by subjective ratings. The illuminances that induced shifting ranged from 106 to 3437 trolands. The PRLhi was always located within an area of relative scotoma, usually at the fovea or just outside a dense scotoma. The PRLlo was located in relatively healthy retinal area, and usually below or to the left of the PRLhi in the visual field. CONCLUSIONS: In the visual system, two well-defined PRLs can develop when visual function is adapting to maculopathy, with the use of each depending on the brightness of objects used in visual tasks. Rehabilitation and treatment strategies should consider the existence of multiple PRLs.

Adaptation, Ocular↗
PubMed1998

[Detection of parafoveal scotoma by multifocal electroretinograms].

We investigated the relation between multifocal electroretinograms (M-ERGs) and artificial parafoveal scotoma. M-ERGs were recorded from normal subjects using a circular piece of black paper attached to a monitor. Lower response density around the 10 to 15 degree parafovea region was not observed up to 3 degree scotoma (visual angle), but was detected above 5 degree scotoma in field topography of M-ERGs. The shape of the scotoma in field topography was not circular but somewhat oval. The results from two cases of parafoveal retinal degeneration were in good accordance with this basic study in normal subjects. We proved that detection of parafoveal scotoma by M-ERG is limited in comparison with the results obtained by automated static perimetry.

Electroretinography↗
PubMed1989

Suppression scotomas in primary microstrabismus--a perimetric artefact.

Static perimetry with stereoscopic targets, "stereo-perimetry", was performed on eight patients with primary microstrabismus to find out how strabismic subjects see under natural conditions, i.e. how they ordinarily make use of their squinting eye. In all cases, suppression scotomas were detectable using dissociating perimetric techniques. By means of stereoperimetry, however, the scotomas were not detectable. On the contrary, stereo-acuity was always best in the center of the suppression scotomas. This result indicates that suppression scotomas of the microstrabismic subjects examined here represented perimetric artefacts. In microstrabismic patients, the cooperation of the deviated eye in the central visual field is probably much better than has previously been thought.

Adolescent↗
PubMed1993

Contrast sensitivity peripheral to an absolute central scotoma in age-related macular degeneration and the influence of a yellow or an orange filter.

Contrast sensitivity for static and dynamic gratings was determined in 17 patients with age-related macular degeneration (AMD) and an absolute central scotoma. Using electronic and computerized equipment, we established contrast sensitivity peripheral to the scotoma at spatial frequencies of 0.5, 1.0 and 2.0 cycles/degree. We found that mean contrast sensitivity was significantly (p < 0.001) lower than that of a control group at a comparable eccentricity, and that interindividual variations were large. Furthermore, we investigated the influence of a yellow and an orange filter on contrast sensitivity peripheral to such an absolute central scotoma in AMD. The results showed significant (p < 0.01-0.05) improvements in contrast sensitivity at certain spatial frequencies only, i.e., for the yellow filter at 2.0 c/deg and for the orange filter at 0.5 and 1.0 c/deg, and only with dynamic presentation. No objective improvement in visual acuity could be demonstrated when using filters. Thus, our findings do not unequivocally support the regular prescription of such filters in order to improve contrast vision in AMD with an absolute central scotoma.

Aged↗
PubMed2005

Long-term follow-up of fixation patterns in eyes with central scotomas from geographic atrophy that is associated with age-related macular degeneration.

PURPOSE: To study whether fixation patterns changed over time in patients with central scotomas from geographic atrophy from age-related macular degeneration. DESIGN: Prospective cohort study. METHODS: setting: Institutional. patient or study population: Prospective natural history study of geographic atrophy included 34 eyes of 25 patients with baseline acuity between 20/80 and 20/200 and with subsequent follow-up. observation procedures: Baseline and annual follow-up visits included best-corrected visual acuity, scanning laser ophthalmoscope macular perimetry, reading rate, and clinical evaluation. main outcome measures: Location of eccentric preferred retinal locus for fixation (PRL). RESULTS: At baseline, 77% of study eyes had a PRL. At the final visit (median follow-up, 5.3 years), 91% of study eyes had a PRL, with 81% of the eyes retaining the baseline PRL location. Fixation with the scotoma to the right and fixation with the scotoma superior were the first and second most common fixation patterns, respectively. Reading rates of <50 words/min were present in 54% of eyes. Eyes fixating with the scotoma to the left tended to have lower reading rates than eyes fixating with right or superior patterns. CONCLUSION: Fixation with right pattern remained the most common fixation pattern, both in patients with a PRL at baseline and in patients who had a PRL during follow-up. Eyes with a PRL at baseline generally retained this pattern. The reading rate data suggest an advantage of fixation with right or superior pattern, rather than left. Reading rate declined further during follow-up in most patients.

Aged↗