Cortical visual impairment

Cortical visual impairment (CVI) is a form of visual impairment that is caused by a brain problem rather than an eye problem. (The latter is sometimes termed "ocular visual impairment" when discussed in contrast to cortical visual impairment.) Some people have both CVI and a form of ocular visual impairment.

CVI is also sometimes known as cortical blindness, although most people with CVI are not totally blind. The term neurological visual impairment (NVI) covers both CVI and total cortical blindness. Delayed visual maturation, another form of NVI, is similar to CVI, except the child's visual difficulties resolve in a few months. Though the vision of a person with CVI may change, it rarely if ever becomes totally normal.

The major causes of CVI are as follows: asphyxia, hypoxia (a lack of sufficient oxygen in the body's blood cells), or ischemia (not enough blood supply to the brain), all of which may occur during the birth process; developmental brain defects; head injury; hydrocephalus (when the cerebrospinal fluid does not circulate properly around the brain, and collects in the head, putting pressure on the brain); a stroke involving the occipital lobe; and infections of the central nervous system, such as meningitis and encephalitis.

Visual and Behavioural Characteristics of CVI are individual and may include several (but not necessarily all) of the following:

-Vision fluctuations likely to appear, can involve a variety of factors including but not limited to:

1. environment^[1]
2. visual complexity of target^[2]
   1. utilise simplified views e.g. larger text
3. familiarity of target
4. other sensory factors
5. level of fatigue
6. personal state of being (i.e. comfort, sickness)

-Performance may vary eye to eye

1. impact on depth perception

-field of view^[3]

1. tunnel vision
2. nystagmus^[4]
3. Movement
   1. depends on speed, reflective properties
   2. cognitive overload
4. scotomas
5. blindsight, not always effective but an intuitive way of knowing surroundings without seeing them

-Eye contact

1. social acceptance in Western cultures^[5]

-Photophobia

1. sensitivity to changes in light and vision
2. 1/3 of people with CVI
3. possible compulsive staring at light sources^[6]
4. task lighting

-Colours

1. colour perception often intact
   1. colour coding often utilized
   2. high contrast can increase clarity^[7]

The presence of CVI does not necessarily mean that the person's brain is damaged in any other way, but it can often be accompanied by other neurological problems, the most common being epilepsy.

Diagnosing CVI is difficult. A diagnosis is usually made when visual performance is poor but it is not possible to explain this from an eye examination. Before CVI was widely known among professionals, some would conclude that the patient was faking their problems or had for some reason engaged in self-deception. However, there are now testing techniques that do not depend on the patient's words and actions, such as fMRI scanning, or the use of electrodes to detect responses to stimuli in both the retina and the brain.^[8] These can be used to verify that the problem is indeed due to a malfunction of the visual cortex and/or the posterior visual pathway.

Clinical Methods include surveys and vision tests to help identify CVI. They can evaluate mobility, coordination, visual acuity, and focus.^[9]

• Cortical blindness

• Tallent, Aubri & Tallent, Andrei (2012). Little Bear Sees: How Children with Cortical Visual Impairment Can Learn to See. Little Bear Sees Publishing, of Wyatt-MacKenzie. p. 156. ISBN 978-1936214822. OCLC 1936214822.
• Roman-Lantzy, Christine (2019). Cortical Visual Impairment: Advanced Principles. New York: AFB Press. ISBN 978-1616480073. OCLC 1055566701.
• Roman-Lantzy, Christine (2017). Cortical Visual Impairment: An Approach to Assessment and Intervention 2nd Ed. New York: AFB Press. ISBN 978-0891286882.
• Dutton GN, Lueck, AH (2015). Vision and the Brain: Understanding Cerebral Visual Impairment in Children. New York: AFB Press. ISBN 978-0891286394. OCLC 904801331.
• Dutton, Gordon N (2006). "Cerebral Visual Impairment: Working within and around the Limitations of Vision". In Lueck, Amanda Hall; Dennison, Elizabeth; American Foundation for the Blind (eds.). Proceedings of the Summit on Cerebral/Cortical Visual Impairment: educational, family, and medical perspectives. New York: AFB Press. ISBN 0-89128-817-1. OCLC 68133091.
• Dutton GN, Jacobson LK (2001). "Cerebral visual impairment in children". Seminars in Neonatology. 6 (6): 477–85. doi:10.1053/siny.2001.0078. PMID 12014888.
• "Fact Sheet: Cortical Visual Impairment" by Mary Ann Demchak, Charmaine Rickard and Marty Elquist, published by The University of Nevada, Reno in the Nevada Dual Sensory Impairment Project 2002.
• Tran, Amanda; Albertos-Arranz, Henar; Juvier-Riesgo, Tamara; Rosello-Rodriguez, Liliana; Ricur, Giselle; Mendoza-Santiesteban, Carlos E. (2026-02-25). "Virtual Reality Visual Field Testing Reduces Visit Duration in a Neuro-Ophthalmology Clinic". Current Eye Research: 1–5. doi:10.1080/02713683.2026.2632676. ISSN 0271-3683.

• CVI Now A CVI resource hub associated with Perkins School For the Blind
• Little Bear Sees A foundation providing families with information, tools and research which improves the lives of children with CVI
• PCVIS The Pediatric Cortical Visual Impairment Society is a nonprofit promoting research related to the improvement of vision care for children with CVI