Visual defect/dysfunction or blindness depending on damages in the retina (fondus), optic nerve, chiasma, visual radiation, occipital cortex, or other parts of CNS affecting visual perception, cognition, learning, memorizing, and visuomotor skills.
CVI is an umbrella term caused by sensory and motor nerve (nervous system) injuries.
CVI: cerebral visual impairment
OVI: ocular visual impairment (albinism, retinopathy of prematurity, Leber congenital amaurosis, achromatopsia, prechiasmatic optic nerve atrophy)
Cortical visual impairment (cortical blindness): an old medical term
The damages in the cortex (brain cortex) and lesions on other parts of the CNS such as the brainstem, thalamus, and cerebellum can lead to CVI.
Our visual perception and experience are based on electromagnetic waves and their wavelength, frequency, and energy.
Electromagnetic waves contact the cornea in front of the eyes. The different optic rules happen in the eye globe:
Reflection:
Transition: Electromagnetic waves pass through the cornea to reach the retina.
Refraction: The passing of EM waves through the cornea, lens, and vitreous body changes their frequency, wavelength, amplitude, and direction.
Diffraction:
Adsorption: Electromagnetic waves partially be adsorbed in the lens and vitreous body.
Transformation: EM waves are transformed into neuroelectrical waves in the retina and optic nerve.
Visualization: The first step of visualization appears in the retina.
Primary CVI: damage in the central nervous system
Secondary CVI: damage in the retina, eyelid (ptosis), or extraocular muscles. Many types of OVI can lead to CVI.
Transient CVI: nightmares, visual hallucinations in febrile episode
Permanent CVI: in various kinds of permanent CNS damage
Physiologic CVI: visual dream
Okulomotor symptom: nystagmus, oculomotor apraxia
Higher cortical visual function:
Ventral system: spreading of neuroelectrical signals from the primary visual cortex to the temporal lobe
Dorsal system: spreading of neuroelectrical signals from the primary visual cortex to the parietal lobe
Underdiagnosed state
The number of children and adults with CVI increases due to the increased knowledge and skills of healthcare professionals, teachers, and educators.
Improved healthcare and survival for children with complicated disabilities or premature born
High intracranial pressure
Epilepsy (epileptiform activity in the posterior part of the brain, i. e., visual cortex)
PVL (periventricular leukomalacia)
Brain tumor
Cerebral infarction
Intracranial hemorrhage
Malformation
Metabolic disorders
Certain genetic disorders
Wrong visual signal to the brain
Diverging management of visual information
Color recognition can be affected in more severe forms of brain damage (CVI)
Disorientation (spatial and topographic)
Abnormal visus/eye movement
Abnormal visual movement detection, perception, attention, recognition, and memory
Eye-hand/eye-foot discoordination
Difficulty with rapid eye movements
Reduced visual cognition (challenging to recognize letters, numbers, and figures)
Color blindness, sensitivity to light, reduced visual acuity, and deficient contrast assessment may be components of CVI.
Clinical examination:
Eye examination by an ophthalmologist
Visual assessment of optician and visual teacher
Neuropsychological assessment of visual perception and cognition
Neurological examination for patient`s overall assessment
Paraclinical examination:
ERG (elektroretinografi): to see how the fondus (retina) works
VEP (visual evoked potential): to see how optic nerve and opticovisual pathway works
EEG: to exclude epilepsy or other electrophysiological abnormalities in the cortex
MRI of the brain: to visualize and map the brain injury
Metabolic and genetic tests
Focus on objects
To make it easier for children, the object must be placed close to the eye to reduce focus on the background image.
Use colors that are individually easiest to recognize. Use more giant letters with longer intervals.
Special computer programs
Stimulate the child visually and auditory simultaneously (see a word and listen to how it sounds).
The yellow or red color appears better than the other colors. The better appearance is due to lower frequency and higher wavelength.
Objects in slow movement appear better.
Use bright colors and a sharp light contrast.