A Sharply Defined Pattern of Central Retinal Thinning
Think of the choroid as the soil feeding the retina from beneath, rich with the blood vessels that keep photoreceptor cells alive. Central areolar choroidal dystrophy is best pictured as a single, sharply defined patch of that soil eroding directly beneath the macula, while the surrounding ground stays firm and untouched. That sharp, well-demarcated boundary — rather than a gradually fading edge — is one of the condition's most recognisable features on examination.
Nigerian patients typically arrive with this condition in their thirties or forties, often after a routine eye exam picked up a distinctly outlined pale patch that a local ophthalmologist recognised as atypical for ordinary age-related change at that age.
The hallmark is slow, gradual central vision blur developing over years rather than months, with a well-defined blind spot forming directly in central vision as the atrophic patch expands. Reading and recognising faces become progressively harder, while side vision remains essentially untouched throughout. Night vision, notably, tends to stay intact — a detail that distinguishes this condition from rod-driven dystrophies like retinitis pigmentosa, where night vision is typically affected early.
Mutations in the PRPH2 gene are the most commonly identified cause, disrupting a protein essential to the structure of photoreceptor outer segments. The choriocapillaris, retinal pigment epithelium, and photoreceptors immediately overlying it degenerate together in a sharply confined central area, rather than diffusely across the retina. Inheritance is typically autosomal dominant.
A fundus examination reveals a clearly demarcated atrophic patch centred on the macula, and fundus autofluorescence is particularly useful for outlining exactly where that atrophy border sits. OCT assesses how much photoreceptor tissue survives at the margins of the patch, and electroretinography is typically near-normal — a finding that itself helps separate this condition from broader, more generalised retinal dystrophies. Genetic testing for PRPH2 completes the diagnostic picture.
Care centres on tracking the pace at which the atrophic patch is expanding, since that rate varies meaningfully between patients and shapes how urgently intervention is considered. Regenerative stem cell therapy is evaluated for eligible patients as a way of supporting the still-viable tissue surrounding the atrophic zone, alongside low-vision planning built around the specific shape and size of the central blind spot as it develops.
Not at all — normal night vision is actually expected and consistent with this specific diagnosis, since the damage stays confined to the central macula rather than affecting the rod cells responsible for night vision. It's one of the details that helps confirm this particular condition rather than a broader retinal dystrophy.
The pace varies considerably from person to person, which is exactly why we track it with sequential imaging over time rather than relying on a single snapshot. Some patients see very gradual change over many years, while others progress somewhat faster.
The appearance can look similar — a well-defined atrophic patch — but this condition is inherited and tends to begin decades earlier than the geographic atrophy seen in older age-related disease. Genetic testing and the age of onset are what distinguish the two.
In most cases, no — the damage in this condition stays confined to the central macular area rather than spreading outward, so peripheral vision and general mobility are typically preserved even as central vision changes over time.