Tools
Visual Discrimination
Definition/Introduction
Visual discrimination is the ability to detect differences and classify objects, symbols, or shapes based on characteristics such as color, position, form, pattern, texture, and size. In the simplest terms, the eyes receive input from the environment, and various cells detect and transmit signals to the brain. Specifically, the visual cortex, located in the occipital lobe, is responsible for processing the shape and orientation of objects. The 3 cell types in the primary visual cortex—simple, complex, and hypercomplex—demonstrate correspondingly increased ability to respond to motion and degree of linearity. A more detailed explanation of the visual cortex is covered in a separate neuroanatomy topic. Please see StatPearls' companion resource, "Neuroanatomy, Visual Cortex," for more information.
The classification and categorization of vision form the foundation for understanding how humans receive and process visual stimuli. For instance, studying visual texture helps reveal the complex relationships between task modulation and perception.[1] Visual discrimination is closely linked to other brain and bodily functions, including hearing, memory, movement, and ambulation.[2][3][4][5][6][7][8] Humans depend on learned visual and motion cues to interpret their surroundings.[9] Human performance can be analyzed through a visual perspective. In sports, a study on gender differences in fencing revealed both significant similarities and differences in various visual capabilities.[10] In the arts, experimental data show that musicians have lower discrimination thresholds for visual, auditory, and auditory-tactile stimuli.[11]
Visual discrimination should not be confused with visual acuity, which refers to the sharpness of vision. Both can be assessed during eye examinations using a traditional eye chart, where patients identify letters or symbols to determine clarity at a distance. Questionnaires can also evaluate a patient’s visual function. Further research into technological applications is needed to enhance and assess key aspects of human visual function. Facial recognition, as objectively measured by electroencephalogram (EEG), is more effective in upright orientations than inverted ones, supporting the role of visual categorization and orientation in human perception.[12] Humans can also be compared to computers to evaluate their respective visual processing abilities. Currently, human sensitivity to discriminating prototypical and complex facial expressions still exceeds the capabilities of artificial intelligence.[13]
Issues of Concern
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Issues of Concern
Changes and limitations in vision are important concerns for patients at all stages of life. A significant amount of visual learning occurs during infancy and early childhood.[14][15][16] Aging-related degeneration, as well as oncogenic processes, can impact vision in various ways.[17][18][19][20][21] Vision can be affected by both orbital tumors and tumors or other pathologies affecting the optic nerve.
Sudden loss of vision or visual disturbances may indicate serious conditions, such as a cerebral vascular accident. A loss or deficiency in visual discrimination can have more subtle clinical implications, such as increasing difficulty in accurately discerning and describing the shape of a circular clock over time. Any condition affecting overall vision may also impact visual discrimination, as patients cannot categorize objects they cannot see.
Clinical Significance
Conditions that affect vision and present clinically typically have neurological, degenerative, anatomic, or oncogenic causes. For example, visual agnosia is a condition where individuals lose the ability to recognize faces or objects.[22] This may occur secondary to traumatic brain injury, dementia, or neurodegenerative conditions, such as multiple sclerosis.
Tumors can lead to various visual discrimination deficiencies.[23][24] Identifying and removing these tumors can be challenging without damaging surrounding tissue, including the visual cortex or important visual pathways.[25] While brain tumors and ophthalmic malignancies often affect children, their long-term effects can be observed into adulthood, as seen in survivors of retinoblastoma.[26][27]
Red-green color blindness is the most common type of color vision deficiency and is predominantly seen in males due to its X-linked inheritance. Please see StatPearls' companion resource, "Color Vision," for more information. This condition arises from a deficiency or absence of certain cone photoreceptors in the retina. A simple test, known as the plate test, can identify various types and degrees of color blindness. In some cases, specialized eyewear can help patients perceive a broader range of colors.
A variety of visual discrimination effects are also seen secondary to:
- Diabetic retinopathy [28]
- Dyslexia [29]
- Lewy body disorders [30]
- Amyotrophic lateral sclerosis (ALS) [31]
This list is not all-inclusive; many other clinical examples of visual discrimination issues exist. These conditions affect individuals across all age groups and can arise from various primary causes or diseases, leading to secondary visual effects.
Nursing, Allied Health, and Interprofessional Team Interventions
Various diseases and developmental deficits can cause disturbances in visual discrimination. Practitioners should be aware of and knowledgeable about when to refer a patient to a specialist for further examination and workup. This is particularly important for family physicians and ophthalmologists, who are often the first to identify visual issues in patients.
Occupational and physical therapies are available to help children improve visual organization skills. Rehabilitation therapies are also offered for individuals with traumatic brain injuries affecting the visual cortex. Additionally, newer training methods are increasingly used to enhance athletic performance.
Nursing, Allied Health, and Interprofessional Team Monitoring
Patients should be screened for visual changes, disturbances, and deficiencies at any age. These issues can also be identified during well-child visits or routine adult physical examinations.
References
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Li Q, Yu H, Li X, Sun H, Yang J, Li C. The informativity of sound modulates crossmodal facilitation of visual discrimination: a fMRI study. Neuroreport. 2017 Jan 18:28(2):63-68. doi: 10.1097/WNR.0000000000000719. Epub [PubMed PMID: 27926629]
Kayser SJ, Philiastides MG, Kayser C. Sounds facilitate visual motion discrimination via the enhancement of late occipital visual representations. NeuroImage. 2017 Mar 1:148():31-41. doi: 10.1016/j.neuroimage.2017.01.010. Epub 2017 Jan 8 [PubMed PMID: 28082107]
Forder L, Lupyan G. Hearing words changes color perception: Facilitation of color discrimination by verbal and visual cues. Journal of experimental psychology. General. 2019 Jul:148(7):1105-1123. doi: 10.1037/xge0000560. Epub 2019 Mar 14 [PubMed PMID: 30869955]
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Hijazi MM. Attention, Visual Perception and their Relationship to Sport Performance in Fencing. Journal of human kinetics. 2013 Dec 18:39():195-201. doi: 10.2478/hukin-2013-0082. Epub 2013 Dec 31 [PubMed PMID: 24511355]
Sharp A, Houde MS, Maheu M, Ibrahim I, Champoux F. Improved tactile frequency discrimination in musicians. Experimental brain research. 2019 Jun:237(6):1575-1580. doi: 10.1007/s00221-019-05532-z. Epub 2019 Mar 29 [PubMed PMID: 30927044]
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Moret-Tatay C, Lemus-Zúñiga LG, Tortosa DA, Gamermann D, Vázquez-Martínez A, Navarro-Pardo E, Conejero JA. Age slowing down in detection and visual discrimination under varying presentation times. Scandinavian journal of psychology. 2017 Aug:58(4):304-311. doi: 10.1111/sjop.12372. Epub 2017 Jul 2 [PubMed PMID: 28670767]
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Level 2 (mid-level) evidenceBoven L, Jiang QL, Moss HE. Diffuse Colour Discrimination as Marker of Afferent Visual System Dysfunction in Amyotrophic Lateral Sclerosis. Neuro-ophthalmology (Aeolus Press). 2017 Dec:41(6):310-314. doi: 10.1080/01658107.2017.1326153. Epub 2017 Jun 1 [PubMed PMID: 29344070]