Cortical visual impairment — branching viva

Opening question

Examiner: Take me through this child. What is the diagnosis, and what is the clue that points you to it? [1]

Candidate: The most likely diagnosis is cortical visual impairment. The key clue is that the child sees poorly despite a structurally normal eye — clear media, normal red reflex and healthy retina. The extreme prematurity and spastic diplegia point to periventricular leukomalacia, and the paradoxical behaviours, turning toward the light while ignoring near faces, fit the CVI pattern. My frame is to confirm the eye is normal, confirm the brain cause with imaging, characterise the functional vision with structured assessment, and then build a habilitative plan. [1] [2]

Examiner: Why has the term moved from cortical blindness to cerebral visual impairment? [1]

Candidate: Because the older term is misleading in three ways. First, most of these children are not blind — they have usable vision that fluctuates. Second, the injury is often not confined to the cortex; it involves the optic radiations and posterior white matter as well. Third, the problem is not just basic acuity but higher-order perception. Cerebral visual impairment is the preferred umbrella term because it captures the retrogeniculate pathway injury and the spectrum from basic to perceptual deficits. [1] [2]

Branch 1 — causes

Examiner: What are the common causes of CVI, and what is the signature injury in this child? [6]

Candidate: The dominant causes are perinatal: hypoxic-ischaemic encephalopathy in the term infant and periventricular leukomalacia in the preterm infant. This child's signature injury is periventricular leukomalacia — the white-matter damage beside the lateral ventricles where the optic radiations travel — which classically produces a lower visual-field deficit alongside the spastic diplegia. Other causes include arterial ischaemic stroke, meningitis and encephalitis, traumatic brain injury including non-accidental injury, hydrocephalus, structural malformations and genetic-metabolic disease. [6] [4]

Examiner: Why does periventricular leukomalacia cause a lower-field deficit specifically? [6]

Candidate: Because the inferior visual-field projection fibres in the optic radiations run closest to the lateral ventricles, where the ischaemic white-matter injury of leukomalacia occurs. The injury to those fibres produces the characteristic inferior visual-field loss, so the child bumps into low objects and ignores items placed low while seeing objects at eye level. The eye is normal; the deficit is in the white matter. [6]

Branch 2 — clinical behaviours and diagnosis

Examiner: Describe the paradoxical behaviours that make up the clinical picture. [2]

Candidate: The behaviours are paradoxical because they contradict the intuitions built from ocular disease. Vision fluctuates with fatigue and environment — good days and bad days. The child may gaze at lights yet ignore near faces. Distance vision is often better than near. Moving and single high-contrast objects are seen better than crowded scenes. Colour preference, often yellow or red, is common. And the lower-field deficit of leukomalacia is the archetype of the field loss. These behaviours, alongside a normal eye exam and a neurological history, are the bedside diagnosis. [2] [11]

Examiner: How do you confirm the diagnosis? [9]

Candidate: Three steps. First, the ophthalmologist confirms the eye is normal with a full assessment including cycloplegic refraction, to exclude a refractive error, optic nerve hypoplasia or retinal dystrophy that could mimic CVI. Second, MRI of the brain identifies the occipital or white-matter injury, confirms the cause and excludes a treatable structural lesion. Third, a structured assessment tool — the CVI Range — quantifies the functional vision across the ten characteristic behaviours and establishes a baseline. The diagnosis is clinical, built on the normal eye, the imaging and the behavioural profile. [9] [2]

Branch 3 — the differential

Examiner: How do you distinguish CVI from delayed visual maturation? [2]

Candidate: Delayed visual maturation is a benign, transient immaturity of the visual system in an otherwise well infant whose vision emerges over the first months of life and normalises fully. It is a diagnosis of exclusion, made only after structural eye disease and CVI have been excluded. The distinguishing features are the normal perinatal and neurological history, the completely normal eye exam, the normal MRI, and the full resolution. In this child, the prematurity, the spastic diplegia and the persistent paradoxical behaviours point away from delayed visual maturation and toward CVI. [2] [9]

Examiner: What would make you worry about an acute or progressive process rather than stable CVI? [4]

Candidate: Sudden visual deterioration, progressive decline over weeks rather than day-to-day fluctuation, headache, vomiting, new seizures or new focal neurological signs. In a child with a shunt these point to shunt malfunction; without one they point to hydrocephalus, raised intracranial pressure, a new stroke or a mass. Progressive cognitive or motor regression alongside visual decline points to a neurodegenerative or metabolic disorder. Any of these warrants urgent neuroimaging, because the natural history of stable CVI is fluctuation and gradual improvement, never abrupt decline. [4] [1]

Branch 4 — management

Examiner: What is the management, given there is no cure for the injured cortex? [11]

Candidate: The management is habilitative. The foundation is environmental modification — reduce visual clutter so the child faces a plain background, present single high-contrast objects in the best field and at the preferred distance, control the lighting, use the colours the child sees well, and allow extra processing time. These adjustments change the child's functional vision immediately and are the single most effective intervention. On top of that, individualised visual stimulation uses movement, colour and contrast to engage the spared pathways, consistently across home and school. [11] [2]

Examiner: Who else needs to be involved, and what is the prognosis? [7]

Candidate: The team is multidisciplinary: ophthalmology monitors the eye and acuity, neurology and neurodisability manage the seizures and motor disorder, educators adapt the classroom, and therapists deliver the stimulation and independence training. The family is the constant, and a shared written plan across settings is what makes the habilitation consistent. The prognosis is generally one of improvement through neuroplasticity over years, but residual deficits usually persist, so support is lifelong and adaptive rather than a one-off course. [7] [11]

Wrap

Examiner: Summarise the CVI stance in one sentence. [1]

Candidate: A child whose vision is poor but whose eye is structurally normal, who gazes at lights and sees distance better than near and loses the object in a crowd, has cortical visual impairment — confirm the normal eye, image the brain, characterise the functional vision, and habilitate through environmental adaptation and multidisciplinary coordination, recognising that the developing brain rewires and most children improve while residual deficits persist and that any abrupt decline signals an acute intracranial process needing urgent imaging. [1] [2]