Overview

Fovea diameter≈1.5 mm (≈5°)

Foveola (rod-free zone)≈0.35 mm (≈1.25°)

Foveal avascular zone≈0.5 mm

Peak cone density≈200 000/mm²

At the fovea the inner retinal layers (ganglion cells, inner nuclear layer, blood vessels) are pushed aside to form a pit, so light reaches the photoreceptors with minimal scatter. Its central floor, the foveola (≈0.35 mm, ≈1.25°), contains only slender, densely packed cones (peak ≈200 000/mm²) — no rods and almost no S-cones. Each foveal cone connects to its own midget bipolar and midget ganglion cell (1:1 "private line"), so spatial sampling is limited only by cone spacing — allowing acuity of ≈1 arc-minute (6/6 or 20/20) or better.

Cone axons run obliquely away from the pit as the Henle fibre layer, which is why macular exudates form a star pattern. The central ≈0.5 mm is the foveal avascular zone (FAZ), supplied entirely by the choroid; its size increases in diabetic retinopathy.

The fovea lies on the visual axis about 5° temporal to the optical axis of the eye. A foveal reflex (bright pinpoint) is seen on fundoscopy in young eyes. The fovea is not mature at birth — cones elongate and pack centrally over the first ≈4 years — so infant acuity is low.

Location: Centre of the macula lutea at the posterior pole, ≈4 mm temporal and ≈0.8 mm inferior to the centre of the optic disc.

Anatomy

Arterial supply: Avascular centre (FAZ ≈0.5 mm) — nourished by the choriocapillaris; parafoveal capillary ring from branches of the central retinal artery.
Histology: Foveola: only cone outer segments, outer limiting membrane, outer nuclear layer and Henle fibres; inner layers absent.

Function

Highest visual acuity and colour discrimination
Target of fixation for saccades and smooth pursuit

Clinical significance

Cherry-red spot

When the inner retina becomes opaque (central retinal artery occlusion, Tay–Sachs and Niemann–Pick disease) the thin foveola still reveals the red choroid.

Foveal hypoplasia

Absent pit in albinism and aniridia (PAX6) — poor acuity and nystagmus.

Solar and laser maculopathy

Looking at the sun (eclipse viewing) or a laser pointer focuses energy precisely on the fovea, causing a permanent central scotoma.

Test yourself

Why does the fovea provide the highest visual acuity?

It contains the highest density of rods
It is supplied directly by the central retinal artery
It lies at the optic disc where ganglion axons converge
Inner retinal layers are displaced and densely packed cones connect almost 1:1 to ganglion cells

Answer: Inner retinal layers are displaced and densely packed cones connect almost 1:1 to ganglion cells

The foveola is rod-free, packed with slender cones (≈200 000/mm²), the overlying layers and vessels are pushed aside, and each cone has a "private line" via a midget bipolar to a midget ganglion cell. It is avascular and nourished by the choroid.