Diagnostic Protocol for Perceptual Visual Difficulties in Children with Cerebral Visual Impairment

Test group: Children with features suggestive of CVI, referred by a paediatric neurologist with systemic diagnosis will be taken as the test group. After IQ assessment/ Autism Score will be included in the study. All children will be assessed by paediatric neurologist, paediatric ophthalmologist, Rehabilitationist and optometrist. Children will be examined in the presence of their parents and caregivers/ special educators.

Control group :

Children between 2 to 18 years of age who are developmentally age matched to the test group will be taken as the control group.  Children with age appropriate development (as ascertained by history), no co occurring ocular or neurologic co mordbidity are recruited. These children are not required to undergo neuroimaging.

Both groups will undergo history, examination and the visuoperceptual or functional vision tests.

History: Antenatal and perinatal history will be documented. Challenges encountered by the child in day-to-day life, visual complaints, atypical visual behaviour, and learning will be documented.

Dr Dutton’s Mini CVI questionnaire consisting of 5 questions will also be documented. 6

Neuroimaging:

MRI findings will be characterised as brain maldevelopments, white matter (WM) lesions, grey matter (GM) lesions, miscellaneous abnormalities, or normal MRI7.

Ocular Examination:

Standard ocular exams including visual acuity age and ability-appropriate charts will be used). Dynamic retinoscopy to assess accommodation will be performed 8. Cycloplegic retinoscopy, anterior segment and fundus will be performed. In case of refractive errors, best glasses will be prescribed.

Strabismus evaluation and binocular single-vision evaluation will be performed with best glasses.

Visuoperceptual (VP) tests:

Children who were nonverbal will assessed with the help of the caregiver or parent and a special educator. Each child will be asked to perform all tests demonstrated by the observer or special educator for at least 2 to 3 trials. Even after the trials, if the child cannot perform the test, the result will be recorded as “absent.” If the child did not attempt the test, it will be categorized as “not testable**.” 9**

Visual Perceptual tests based on the L94 protocol for 2 to 5-year-olds 10,11  and DTVP 3 testing methods for children more than 5 years 12 will be used. The tests will include fixation time, visual field, contrast, colour vision, visual discrimination, visual closure, form constancy, biological motion, saccades, pursuits, visual memory, figure-ground discrimination, visual agnosia, ataxia, reading performance etc will be assessed. VP tests will be categorised for dorsal and ventral streams.

Based on the pattern of difficulties in the test battery, we shall analyse if certain domains are specifically affected in certain neurological abnormalities. If VP tests can be used as a standard measure to diagnose the presence of CVI in a child. VP pattern will be correlated to MRI abnormalities to see if they are associated with or represent structurally abnormal areas.