Spatial summation in blindsight

AbstractSpatial summation curves were determined in the circumscribed visual-field defects of five patients with blindsight. Under light-adapted conditions that favor the color-opponent system, increment thresholds for white and red targets presented on a white background were measured as a function of stimulus size which ranged from 9–110 min arc. In both normal and defective hemifields, summation was linear for the red stimuli. In contrast, the curves measured with the white stimuli showed some nonlinearity in the normal hemifield, and a pronounced eccentricity-dependent notch in the field defect. The results indicate that the neurons mediating sensitivity differ in their summation properties for wavelength and intensity information.

Download Full-text

Local Relationship between Global-Flash Multifocal Electroretinogram Optic Nerve Head Components and Visual Field Defects in Patients with Glaucoma

Journal of Ophthalmology ◽

10.1155/2015/397495 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Chan Hee Moon ◽

Jungwoo Han ◽

Young-Hoon Ohn ◽

Tae Kwann Park

Keyword(s):

Optic Nerve ◽

Visual Field ◽

Optic Nerve Head ◽

Visual Field Defect ◽

Multifocal Electroretinogram ◽

Visual Field Defects ◽

Global Flash ◽

Field Defect ◽

Normal Controls ◽

Field Defects

Purpose. To investigate the local relationship between quantified global-flash multifocal electroretinogram (mfERG) optic nerve head component (ONHC) and visual field defects in patients with glaucoma.Methods. Thirty-nine patients with glaucoma and 30 normal controls were enrolled. The ONHC amplitude was measured from the baseline to the peak of the second positive deflection of the induced component. The ONHC amplitude was normalized by dividing ONHC amplitude by the average of seven largest ONHC amplitudes. The ONHC amplitude ratio map and ONHC deficiency map were constructed. The local relationship between the ONHC measurements and visual field defects was evaluated by calculating the overlap between the ONHC deficiency maps and visual field defect plots.Results.The mean ONHC amplitude measurements of patients with glaucoma (6.01±1.91 nV/deg2) were significantly lower than those of the normal controls (10.29±0.94 nV/deg2) (P<0.001). The average overlap between the ONHC deficiency map and visual field defect plot was 71.4%. The highest overlap (75.0%) was between the ONHC ratios less than 0.5 and the total deviations less than 5%.Conclusions.The ONHC amplitude was reduced in patients with glaucoma compared to that in normal controls. Loss of the ONHC amplitude from the global-flash mfERG showed a high local agreement with visual field defects in patients with glaucoma.

Download Full-text

Pattern of Visual Field Defects in Newly Diagnosed Primary Open Angle Glaucoma Patients Attending Tertiary Care Hospital, Kathmandu, Nepal

Nepal Medical College Journal ◽

10.3126/nmcj.v22i4.34181 ◽

2020 ◽

Vol 22 (4) ◽

pp. 203-210

Author(s):

Pranisha Singh ◽

AP Rijal

Keyword(s):

Visual Field ◽

Primary Open Angle Glaucoma ◽

Tertiary Care Hospital ◽

Open Angle Glaucoma ◽

Tertiary Care ◽

Visual Field Defects ◽

Care Hospital ◽

Newly Diagnosed ◽

Field Defect ◽

Field Defects

The purpose of this study was to evaluate the location and pattern of visual field defects as measured by Humphrey Field Analyzer (HFA 24-2) in newly diagnosed primary open angle glaucoma (POAG) attending tertiary care hospital. This was a cross sectional, descriptive study. One hundred and four eyes of 52 patients who fulfilled the inclusion criteria during one year were included. They were classified as mild, moderate and severe glaucoma according to severity. Paracentral scotoma in superotemporal and superonasal region was the most frequent visual field defect observed in mild glaucoma. Superior arcuate defect and double arcuate defect was commonly seen among moderate and severe stages of POAG respectively. There was a significant association between severity of glaucoma and pattern of visual field defect (p=0.000). The superior hemifield was affected twice more than the inferior hemifield in newly diagnosed cases of POAG.

Download Full-text

What are the characteristics and progression of visual field defects in patients with Leber hereditary optic neuropathy: a prospective single-centre study in China

BMJ Open ◽

10.1136/bmjopen-2018-025307 ◽

2019 ◽

Vol 9 (3) ◽

pp. e025307

Author(s):

Hong-Li Liu ◽

Jia-Jia Yuan ◽

Zhen Tian ◽

Xin Li ◽

Lin Song ◽

...

Keyword(s):

Visual Field ◽

Optic Neuropathy ◽

Visual Function ◽

Visual Field Defect ◽

Visual Field Defects ◽

Leber Hereditary Optic Neuropathy ◽

The Difference ◽

Field Defect ◽

Hereditary Optic Neuropathy ◽

Field Defects

ObjectiveTo study the characteristics and progression of visual field defects in patients with Leber hereditary optic neuropathy.DesignProspective study.Setting3-A-class hospital in China; single-centre study.ParticipantsFrom 100 patients diagnosed with Leber hereditary optic neuropathy, 80 (160 eyes; 68 men and 12 women; youngest patient, 6 years; oldest patient, 35 years) were recruited.ExposureAll patients were followed up for at least 12 months. Each patient underwent at least three visual field examinations. Patient groups 1–6 were created according to the time of visual field data acquisition. Patient group 7 included patients with a different onset of disease between eyes. Group 8 was composed of patients with a course of disease of 12–24 months when one of the examinations performed. Patients who performed the third examination made up patient group 9.Primary outcome measuresPrevalence of the different visual field defect types on the basis of severity in groups 1–6. Mean of the difference of visual function between eyes in group 7.ResultIn groups 1–6, the prevalences of defects classified using Visual Field Index values were significantly different between groups 1 and 3. In group 7, with the prolongation of the course of the disease, the mean of the difference of visual function between eyes decreased. There was no significant correlation between age and the severity of visual field defect. There was significant correlation between visual acuity and the severity of visual field defect.ConclusionVisual field defects in patients with Leber hereditary optic neuropathy (G11778A) may continuously progress within 6 months of disease development, and remain stable after 9 months. With the progression of the disease, the differences in visual function between eyes may decrease. The severity of visual field defect seems to be independent of age; however, could be related to visual acuity.Trial registration numberNCT03428178,NCT01267422.

Download Full-text

Perimetric Study of Field Defects in Monkeys after Cortical and Retinal Ablations

Quarterly Journal of Experimental Psychology ◽

10.1080/14640746708400098 ◽

1967 ◽

Vol 19 (3) ◽

pp. 232-245 ◽

Cited By ~ 65

Author(s):

Alan Cowey

Keyword(s):

Visual Field ◽

Histological Examination ◽

Striate Cortex ◽

Visual Field Defects ◽

Projection Area ◽

Central Scotoma ◽

Eccentric Fixation ◽

Field Defect ◽

Primary Projection ◽

Field Defects

Monocular visual field defects were studied in two monkeys. In one, the macular retina was destroyed by photocoagulation, producing a central scotoma and consistent 5° eccentric fixation. In a second animal the effects of removal of macular projection area in striate cortex and subsequent photocoagulation of the macula were compared. The cortical operation produced a partial field defect, i.e. a region of diminished sensitivity but not a scotoma, which became with practice much smaller than the region of retina whose primary projection area had been ablated. A 10° eccentric fixation was observed. Following the second, retinal, operation a macular scotoma was demonstrated whose size and position corresponded closely with the area of retinal destruction as determined by photography of the fundus and later histological examination of the retina.

Download Full-text

Monocular Visual Field Defect on Humphrey 24-2 SITA-Fast Testing Later Identified as a Highly Incongruous Homonymous Defect on Humphrey 30-2 SITA-Fast Testing

Case Reports in Ophthalmology ◽

10.1159/000516663 ◽

2021 ◽

pp. 507-512

Author(s):

Caberry W. Yu ◽

Jonathan A. Micieli

Keyword(s):

Visual Field ◽

Visual Field Defect ◽

Anterior Segment ◽

Field Testing ◽

Visual Pathway ◽

Visual Field Defects ◽

Inner Plexiform Layer ◽

Visual Field Testing ◽

Field Defect ◽

Field Defects

Monocular visual field defects generally localize at or anterior to the optic chiasm, while homonymous hemianopias localize to the retrochiasmal visual pathway. Highly incongruous visual field defects may be difficult to identify on 24-2 Humphrey visual field testing, and this case demonstrates the value of optical coherence tomography (OCT) ganglion cell-inner plexiform layer (GCIPL) in rapidly localizing the lesion. A 54-year-old woman was found on routine examination to have an isolated superonasal quadrant visual field defect respecting the vertical meridian in the left eye only on Humphrey 24-2 SITA-Fast testing. She had a remote history of significant head trauma. Visual acuity, anterior segment, and fundus examination were normal. OCT revealed a bow-tie atrophy of the retinal nerve fiber layer in the right eye (OD), and binocular homonymous hemi-macular atrophy of OCT GCIPL, confirming the localization was the left retrochiasmal visual pathway. A repeat Humphrey 30-2 SITA-Fast visual field demonstrated that the visual field defect was also present in the OD in a highly incongruous manner. Magnetic resonance imaging of the brain with contrast showed mild atrophy of the left optic tract. This case demonstrates that highly incongruous visual field defects may be difficult to identify on Humphrey 24-2 SITA-Fast visual fields, and OCT GCIPL serves as a rapid way to localize the lesion. More detailed visual field testing including 30-2 programs should be considered in these cases.

Download Full-text