What does chorioid mean?
Chorioid refers to the delicate, richly vascularized membrane that forms the middle layer of the wall of the eye, sandwiched between the light-sensitive retina on the inside and the tough white sclera on the outside. Its dense network of blood vessels delivers oxygen and nutrients to the outer layers of the retina, while its dark pigmentation absorbs stray light and prevents reflections from blurring vision. The word functions as a noun in formal anatomical and medical contexts and appears most often in textbooks, clinical literature, and discussions of ocular conditions such as inflammation of this layer. 'Chorioid' is now largely a historical or regional variant spelling of the standard term 'choroid', so readers will encounter it mainly in older sources. Understanding the term offers insight into how finely structured the eye is, and why its layered design is essential to sharp sight.
nounThe vascular layer of the eye lying between the retina and the sclera; a variant spelling of 'choroid'. It supplies oxygen and nourishment to the outer layers of the retina.
- The pigmented, highly vascular membrane between the retina and sclera of the eye that nourishes the outer retinal layers.
"Light entering the eye passes through the retina before reaching the darkly pigmented chorioid beneath it."
"Damage to the chorioid can impair the supply of nutrients to the photoreceptors."
"In his lecture, the ophthalmologist traced the blood vessels branching across the chorioid."
Rarely pluralized, since each eye has a single chorioid; the plural may appear when discussing multiple specimens or both eyes in comparative anatomy.
"The dissection compared the chorioids of several mammalian species."
Before 'choroid' became standard, anatomists spelled this eye layer with an extra 'i' — and 'chorioid' still survives in older medical textbooks.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chorioid
'Chorioid' derives from the Greek 'chorioeidēs', formed from 'chorion', meaning a membrane or afterbirth-related membrane, combined with '-eides', meaning 'like' or 'having the form of'. The term entered English medical vocabulary in the seventeenth century as anatomists adopted Greek descriptive terminology. It shares its root with 'chorion' and 'chorionic', both still current in embryology, and exists alongside its shortened variant 'choroid', which ultimately displaced it in common usage.
How chorioid is actually used
'Chorioid' is chiefly found in older or British medical literature; contemporary anatomy texts overwhelmingly prefer the spelling 'choroid'. The term belongs to formal scientific register and would not appear in casual conversation.
Easily confused with chorioid
'Chorioid' is the vascular middle layer of the eyeball, while 'coriander' is an aromatic herb used in cooking.
'Choroid' is the standard modern spelling and 'chorioid' is an older variant of exactly the same anatomical structure.