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Visual Agnosia

Visual Agnosia

Visual agnosia is a condition characterized by the inability to recognize visually presented objects despite having normal vision. For instance, a person with visual agnosia can describe the shape and color of an object but cannot identify or name it. This impairment does not affect their visual field, acuity, color vision, brightness discrimination, language, or memory. An example of this condition in a social setting is someone at a dinner party asking for "that silver thing with a round end"...

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Related Experiment Video

Updated: May 21, 2026

Using an Automated Hirschberg Test App to Evaluate Ocular Alignment

Using an Automated Hirschberg Test App to Evaluate Ocular Alignment

Published on: March 24, 2020

A 'web app' for diagnosing hemianopia.

Nato Koiava¹, Yean-Hoon Ong, Maurice M Brown

¹Institute of Neurology, University College London, London, UK.

Journal of Neurology, Neurosurgery, and Psychiatry

|May 31, 2012

Summary

This summary is machine-generated.

A new online visual field test, Read-Right, shows high accuracy in identifying hemianopia, especially in undamaged visual fields. This free tool offers a quick screening method for patients with visual field defects.

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Last Updated: May 21, 2026

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Published on: September 18, 2012

Area of Science:

Ophthalmology
Neurology
Medical Technology

Background:

Hemianopia frequently results from stroke, impacting daily activities and necessitating rehabilitation.
Early identification of visual field defects is crucial for effective patient management.
The Read-Right online visual field test was developed for hemianopic alexia patients as part of a free web-based therapy program.

Observation:

The study validated the Read-Right online visual field test against the Humphrey automated visual field analyzer, a clinical gold standard.
22 patients underwent visual field assessment using both the Read-Right test and Humphrey perimetry on the same day.
Criterion validity was assessed using sensitivity, specificity, kappa (κ) statistics, and intraclass correlation.

Findings:

Read-Right demonstrated high sensitivity and specificity, particularly for the undamaged visual field.
Significant kappa values were observed in the damaged field, especially along the horizontal meridian.
Excellent intraclass correlation indicated strong agreement between Read-Right and Humphrey perimetry for the damaged field.

Implications:

The Read-Right test provides a rapid and accessible screening tool for hemianopia.
While not a replacement for standardized perimetry, it aids in initial patient assessment.
The test is freely available within web-based therapy applications for hemianopic alexia patients.