Cortical visual impairment — formative SAQs

SAQ 1 (10 marks)

A 10-month-old girl born at 26 weeks gestation is reviewed because she does not reliably fix and follow or reach for toys held in front of her. She has spastic diplegia and turns toward the window light, sometimes ignoring her mother's face held close. Her external eye exam, red reflexes and dilated fundus are normal, with clear media and a healthy retina. [6]

Question: (a) What is the diagnosis, and what does the normal eye exam signify? (b) Outline the assessment and investigation. (c) Outline the habilitative management and the prognosis. (10 marks) [2]

Model answer

(a) Diagnosis and the normal-eye clue (3 marks). The most likely diagnosis is cortical visual impairment (CVI), in which reduced visual function arises from damage to the brain's post-chiasmal visual pathways and occipital cortex rather than from the eye. The extreme prematurity and spastic diplegia point to periventricular leukomalacia, and the paradoxical behaviours — light-gazing and ignoring near faces — fit the CVI profile. The normal eye exam is the central clue: clear media, normal red reflex and healthy retina mean the eye is structurally intact, so the visual difficulty must lie in the brain. The older term cortical blindness is avoided because she is not blind and her vision fluctuates; cerebral visual impairment is the preferred umbrella term. [1] [2]

(b) Assessment and investigation (4 marks). Confirm the eye is normal with a full ophthalmology assessment including cycloplegic refraction, to exclude a severe refractive error or optic nerve hypoplasia that could mimic CVI. Arrange MRI of the brain to identify the periventricular white-matter injury, confirm the cause and exclude a treatable structural lesion such as hydrocephalus. Use a structured assessment tool — the CVI Range (Roman-Lantzy) — to quantify her functional vision across the ten characteristic behaviours and establish a baseline. Combine these with the parents' account of how she uses vision at home, observing the fluctuation, the distance-versus-near pattern, and any field deficit, to build the functional profile that guides habilitation. [9] [6]

(c) Habilitative management and prognosis (3 marks). There is no drug or surgery for the injured cortex, so management is habilitative. The foundation is environmental modification: reduce visual clutter so she faces a plain background, present single high-contrast objects in her best field and at the preferred distance, control the lighting, and allow extra processing time. Build individualised visual stimulation using movement, colour and contrast to engage spared pathways, and coordinate the multidisciplinary team — ophthalmology, neurology and neurodisability, education and therapy — with a shared written plan across home and school. The prognosis is generally one of improvement through neuroplasticity over months and years, though residual deficits such as the lower-field loss and crowding intolerance usually persist and continue to shape learning. [11] [7]

SAQ 2 (10 marks)

Question: A 5-year-old boy with known cortical visual impairment and a ventriculoperitoneal shunt for post-haemorrhagic hydrocephalus is brought to the emergency department. Over two days he has stopped tracking objects, developed vomiting and become drowsy. His decline was abrupt rather than fluctuating. (a) What is the most likely cause of his acute deterioration, and why is this not the chronic fluctuation of CVI? (b) Outline the immediate investigation and management. (c) State the features that, in a child with stable CVI, would instead indicate routine review. (10 marks) [4]

Model answer

(a) The acute cause and why it is not chronic fluctuation (3 marks). The most likely cause is a shunt malfunction or raised intracranial pressure from hydrocephalus. A child with a ventriculoperitoneal shunt who develops abrupt visual deterioration with vomiting and drowsiness has shunt failure until proven otherwise. This is not the chronic fluctuation of CVI because stable CVI fluctuates with fatigue and environment over hours and days but does not abruptly and progressively decline, and it is not accompanied by vomiting and drowsiness. The natural history of stable CVI is fluctuation and gradual improvement or plateau — never abrupt deterioration with signs of raised intracranial pressure. [4] [1]

(b) Immediate investigation and management (4 marks). Arrange urgent neuroimaging — a shunt series and CT or MRI of the brain — to assess the shunt and the ventricular size and exclude raised intracranial pressure, a new stroke or a mass. Involve the neurosurgical team urgently for shunt interrogation and revision if malfunction is confirmed. Manage the airway, breathing and circulation, treat raised intracranial pressure if present, and monitor closely. The visual deterioration may reverse with relief of the pressure, so time matters — reassurance and a routine review without imaging would be a serious error that could cost the child's remaining vision or life. [4] [1]

(c) Features indicating routine review in stable CVI (3 marks). Features that fit the chronic trajectory and warrant routine rather than urgent review include the day-to-day fluctuation of visual attention tied to fatigue and environment, gradual improvement or plateau over months and years, and the consistent paradoxical pattern (distance-better-than-near, light-gazing, crowding difficulty) without new neurological signs. In stable CVI the child is reviewed periodically in the neurodisability and ophthalmology clinics, the functional assessment is updated at developmental transitions, and the environmental and educational plan is revised. Any departure from this chronic trajectory — abrupt decline, progressive worsening, headache, vomiting, new seizures or new focal signs — reactivates the urgent-imaging pathway rather than the routine-review pathway. [9] [7]