Coloboma, congenital cataract and congenital glaucoma !

Malformation

Three eye anomalies with an embryonic origin: a slit that did not close, a cloudy lens and a badly formed drain of the eye.

Updated 2026-11-01

See it in 3D: Lens · Iris · Retina · Optic disc · Cornea · Ciliary body · Choroid

What it is

Coloboma is a tissue gap from incomplete closure of the choroid fissure; congenital cataract is clouding of the lens present at birth; primary congenital glaucoma comes from abnormal development of the drainage angle (trabecular meshwork). All three can be picked up on the newborn exam, and some are urgent because of the risk of amblyopia.

Key facts

Coloboma: about 1 in 10,000; it sits in the lower half of the eye and can involve iris, retina, choroid or optic nerve.
Congenital cataract: most have no cause found; known causes include rubella, galactosemia, trisomies 21 and 13, inherited forms.
Maternal rubella in weeks 4–7 damages the lens; later infection tends to affect mainly the ear.
Primary congenital glaucoma: before age 3 with no other anomalies; CYP1B1 in a share of cases.
A dense one-sided cataract is the most likely to cause amblyopia.

Embryological cause

Coloboma: the choroid (optic) fissure, on the underside of the cup and stalk, fails to fuse in week 7; PAX2 and PAX6 are involved.
Cataract: abnormal primary or secondary lens fibers, which come from surface ectoderm; rubella virus damages the forming fibers.
Congenital glaucoma: the trabecular meshwork and iridocorneal angle, from neural crest mesenchyme, fail to mature and aqueous humor cannot drain.

Markers

PAX6
PAX2
CYP1B1
CHD7

How it presents

Iris coloboma: a 'keyhole' pupil pointing down; retinal or optic nerve coloboma can reduce vision.
Coloboma with heart defects, choanal atresia and ear anomalies suggests CHARGE syndrome.
Cataract: white or grey pupil (leukocoria), absent or uneven red reflex, nystagmus, a baby who does not fix and follow.
Congenital glaucoma: tearing, photophobia, an enlarged eye (buphthalmos) and a cloudy cornea.

Diagnosis

Red reflex on the newborn exam: the key screening test.
Slit-lamp exam and dilated fundoscopy.
Glaucoma: intraocular pressure, corneal diameter and angle exam under anesthesia.
Cataract: look for congenital rubella, galactosemia and other systemic causes.

Test yourself

Think of the answer, then tap the question to see it.

Why is a coloboma usually in the lower part of the eye?

Because the choroid fissure, whose closure fails, lies on the underside of the optic cup and stalk.

In which weeks does maternal rubella cause congenital cataract?

Weeks 4 to 7, while the lens is forming.

Which three symptoms suggest congenital glaucoma?

Tearing, photophobia and an enlarged eye with a cloudy cornea.

Which part of the newborn exam detects congenital cataract?

The red reflex: it is absent, whitish or uneven.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

Microorganisms

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Coloboma: MedlinePlus Genetics (U.S. National Library of Medicine, 2024); Congenital cataract: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine, 2024); Early-onset glaucoma: MedlinePlus Genetics (U.S. National Library of Medicine, 2024); Langman's Medical Embryology, 13th ed., ch. 20: Eye (Wolters Kluwer, 2015).

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Representative model, for educational purposes only.