Cataract or Waterfall: The Etymology of Words in Ophthalmology

What does the word cataract have to do with a cloudy lens?

Why is the word pupil also a term for a student?

Why is it called the conjunctiva? 

These are a few of the questions that we will answer below as we explore the etymology of common ophthalmology terms.


Pupil

The term for the black space in the center of the eye stems from the Latin pupillo/a, a diminutive of pupo/a, a term for “boy/girl.”  To understand why those in Antiquity would use such a term, we must remember that prior to microscopy, observers were limited to what could be seen with the naked eye.  And, when we look at another person’s pupil, we see:  ourselves, and truthfully a small version of ourselves.  Hence it is believed that the term pupillo/a gradually came to describe the black space in the center of the eye as one would see his or her minified reflection. (1) (2)

Romance languages, such as Spanish, do retain this dual-meaning, though the word pupilo/a has gradually shifted to mean variously “orphan, ward of the state”. (3)  French similarly retains this connotation with pupille. (4)

Ancient and Modern Greek kore [κόρη] retains the dual meaning of “girl” and “anatomical pupil.”  So does Hebrew with ishon [אִישׁוֹן] meaning both “pupil” and being the diminutive of “man”, in a similar way that pupillus is the diminutive of pupus. (5)

Pupil is also cognate with the English pupa, the term used to describe the immobile metamorphotic insect stage.


Cataract

As with the pupil, ancient observers were limited to what they could see with the naked eye.  As such, mild nuclear sclerosis or cortical changes would be invisible.  Cataracts in Antiquity would not have been noticeable until practically white.  Ancient observers believed cataracts to be comprised of corrupt or abnormal humor (as in related to the Hippocratic notion of bodily humors).  Terms such as the Latin suffusio (“spreading out”) and the Ancient Greek hypochyma (ὑπόχυμα, “fluid under/beneath”) were used to describe cataracts, and both relate to this dispersion of abnormal humor. (6)  However, many terms aside from these were used to describe a cataract, and Ancient writers specifically believed that the opacification was in front of the lens, not within the lens itself as we now know today.

The modern term cataract stems from the Latin cataracta, meaning waterfall, a meaning still retained in English today.  This was likely borrowed from the Ancient Greek katarraktes (καταρράκτης), meaning “rush or dash down.”  There does not appear to be a consensus as to why a term for waterfall was used to describe a cataract.  Several theories include:

1. The appearance of whitening of the pupil resembles the white water often seen in waterfalls and rapids.  Indeed, in Arabic, a cataract can be referred to as “white water.” (7)

2. The blurring of vision resembles that of looking through a waterfall.

3. A belief that cataracts stemmed from fluid traveling in the eye.  This is supported by text written by Abu Ubayd al-Juzjani, a student of the philosopher and physician Avicenna, who claimed that cataracts are caused by the “pouring-out of corrupt humor into the eye.” (8)  This links to the aforementioned concept in Antiquity of a cataract as being related to abnormal humor.  Indeed, to this day, we continue to describe the eye as filled with humor, if only semantically (i.e. aqueous and vitreous humor).

4. In Latin, cataracta had a secondary meaning of a large gate, what we would now refer to as a portcullis.  Perhaps the obstruction of vision by a cataract was likened to the obstruction of an entryway by a portcullis. (9)


Glaucoma

The history of the terminology used for glaucoma and the etymology of the term glaucoma remain complex and somewhat controversial.  The likely origin lies with the Ancient Greek glaukos (γλαυκός), a term used variously to describe a sea-green/blue-gray color. (10)  It is believed that in Antiquity, glaukos was used to describe various ocular conditions with opacification visible to the naked eye, including numerous corneal conditions and even cataracts.  However, it was also used to describe eye (i.e. iris) color in the general, non-pathologic sense. (11) 

As acute angle-closure glaucoma often presents with corneal edema, ancient observers would have noted the typical blue-gray opacification of the eye and hence used the term glaukos to describe this condition.  Alternatively, as dense cataract is a risk factor for angle-closure (such as in a phacomorphic presentation), patients in Antiquity who presented in acute angle-closure may have manifested dense cataracts that would have been described as glaukos.

Indeed, the word glaucous remains in use in English and describes a “bluish-green-gray” hue.  Open-angle glaucoma would have been indistinguishable from other asymptomatic forms of vision loss, such as retinal vascular disorders or optic neuropathies, and would have been termed amblyopia, stemming from the Ancient Greek amblos (ἀμβλύς), meaning “dull, blunt”, i.e. literally “blunted vision.” (10)  As the pathologies lumped into the catch-all term amblyopia were discovered and were given their own terminologies, we were left with our modern amblyopia, also an asymptomatic form of vision loss with no discernible ocular pathology on examination or testing.

Arabic scholars translated glaukos to zarqaa, a term meaning “blue.” (10)  To this day, glaucoma is referred to as “blue water” in Arabic. (12) (13)  The addition of “water” to the term may stem from the belief that the discoloration was due to swelling (which is true), or that a cataract, which already was believed to arise from a derangement of humors in the eye, played a role in the condition (incidentally also true).  In Hebrew, the term for glaucoma, barqit (בַּרְקִית), shares its root with that for “lightning, sheen, glint”, possibly also relating to the abnormal reflectance or appearance of an eye suffering from acute-angle closure.

Some scholars attempt to turn back the clock ever further and suggest that Bronze Age Greek peoples are the ultimate source of the term glaucoma, having derived it from glaux, meaning “owl.” (14)  The evidence rests in the common Greek folk tradition of naming diseases after animals (e.g. alopecia stems from alopex, “fox”, one of many examples).  Perhaps an owl, with its big eyes, reminded these Ancient people of the edematous and bullous corneas of acute-angle closure. (15)  This would be no different from our modern use of buphthalmos (Greek for “ox eye”) to describe the enlarged globes of those suffering from pediatric glaucoma.


Iris

The term for the diaphragm of the eye stems from the Ancient Greek iris, meaning “rainbow,” likely called so due to the many colors of the human iris.  A similar meaning appears in Russian (raduzhnaya oblochka, радужная оболочка, or “rainbow membrane”) and in Hebrew (kashtit, קַשְׁתִּית, derived from the same root as “rainbow”).  In English, as in Spanish and French, the word for the flower and the eye part are the same, though this is not always the case (as in Russian and Hebrew, where the flower is known as an “iris”).


Sclera:  Derived from the Ancient Greek skleros (σκληρός) meaning “hard,” and from where the term sclerotic derives.  The sclera used to be termed tunica albuginea oculi, or “white coat of the eye”.

Lens:  Derives from Latin lens, i.e. a “lentil.”

Umbo:  A word used to describe the boss, or protuberance, at the center of a shield, and by extension, any anatomical depression or excavation.  Unrelated, but from umbo we derive the term umbilicus.


Various terms in ophthalmology are actually abbreviations of longer phrases, and in many cases what used to be an adjective is now used as a noun.  The terms below are examples of such:

Conjunctiva:  Shortening of membrane conjunctiva, Latin for “conjoining membrane,” likely so-termed as the conjunctiva connects the globe and eyelids via a single membrane.

Retina:  Shortening of tunica retina, Latin for “net-like coat.”  This may be a Latin translation of an Arabic translation of an originally Greek term. (16)

Macula:  Shortening of macula lutea, Latin for “yellow spot,” due to the accumulation of xanthophyllic pigment (xanthos describing a hue of yellow in Ancient Greek).

Fovea:  Shortening of fovea centralis, Latin for “central pit.”  The term fovea is a general anatomical term not limited to the eye.

Cornea:  Shortening of tela cornea, Latin for “horn-like tissue” (i.e. cornea is an adjective though now is used as a noun). (17)  Adjectival forms of the word use the Ancient Greek “kerato-”, similarly related to “horn.” The reason behind the use of the word “horn” to describe the cornea is unclear, though it may relate to the similar appearance of the cornea compared to animal horn shavings, or to the durable and hard nature of the cornea. (18)  The latter theory receives support from similar uses of the root to describe durable and tough tissue, such as the stratum corneum of the skin.


If you speak a language other than the ones in this blog post, what is the word for pupil in your language, and does it relate to any connotation of “child, small person, student, or orphan”?  Is the term for iris the anatomical part and iris the flower the same?  What is the term for “glaucoma”?  Please leave your comments below!


References

1. pupil (n.2). Online Etymology Dictionary. [Online] [Cited: 5 26, 2023.] https://www.etymonline.com/word/pupil.
2. 'Pupil': One's own reflection in somebody's eye. Word Histories. [Online] [Cited: 5 27, 2023.] https://wordhistories.net/2018/02/01/pupil-origin/.
3. Real Academia Espanola. pupilo, la. Madrid, ES : Asociacion de Academias de la Lengua Espanola.
4. Pupille. Dictionnaire de l'ancienne langue française et de tous ses dialectes du IXe au XVe siecle. Paris : s.n., 1884.
5. First, Mitchell. JewishLink. [Online] 10 4, 2022. [Cited: 6 11, 2023.] https://jewishlink.news/ishon-the-little-man-in-the-eye/.
6. Cataract. [Online] [Cited: 5 2023, 22.] http://www.mrcophth.com/Historyofophthalmology/cataracthistory.htm.
7. Cataracts (White Water). [Online] 6 6, 2022. [Cited: 5 23, 2023.] https://www.dallah-hospital.com/english/cataracts-(white-water)-news.
8. Mistaken Science. [Online] April 22, 2008. [Cited: May 15, 2023.] https://wordcraft.infopop.cc/eve/forums/a/tpc/f/756604565/m/2881057435?csra=Y&f=756604565&a=tpc&m=2881057435&s=441607094.
9. cataract. Online Etymology Dictionary. [Online] [Cited: 5 25, 2023.] https://www.etymonline.com/word/cataract.
10. What was Glaucoma Called Before the 20th Century? Leffler, Christopher T, et al. s.l. : Ophthalmol Eye Dis, 2015, Vol. 7.
11. The early history of glaucoma: the glaucous eye (800 BC to 1050 AD). Leffler, Christopher T, et al. s.l. : Clin Ophthalmol, 2015, Vol. 9.
12. Glaucoma (Blue Water). Jawad Vision. [Online] 10 1, 2019. [Cited: 5 23, 2023.] http://www.jawadvision.com/en/2019/10/01/glaucoma-blue-water/.
13. Glaucoma (Blue Water). Saudi Ministry of Health. [Online] 3 1, 2015. [Cited: 5 23, 2023.] https://www.moh.gov.sa/en/HealthAwareness/EducationalContent/Blog/1436/Pages/Blog-2015-03-01-01.aspx.
14. Glaucoma and the Origins of Its Name. Laios, Konstantinos, Moschos, Marilita M and Androutsos, George. 5, s.l. : Journal of Glaucoma, 2016, Vol. 25.
15. Controversies in the history of glaucoma: is it all a load of old Greek? Tsatsos, Michael and Broadway, David. 11, s.l. : Br J Ophthalmology, 2007, Vol. 91.
16. retina. Online Etymology Dictionary. [Online] [Cited: 5 24, 2023.] https://www.etymonline.com/word/retina.
17. Cornea. Vocabulary.com. [Online] [Cited: 5 23, 2023.] https://www.vocabulary.com/dictionary/cornea.
18. Cornea. Anatomy Almanac. [Online] 12 4, 2007. [Cited: 5 24, 2023.] http://anatomyalmanac.blogspot.com/2007/12/cornea-from-latin-cornu-animal-horn-and.html.
19. [Online] “blue.”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4601337/#b34-oed-7-2015-021 .
20. [Online] https://www.moh.gov.sa/en/HealthAwareness/EducationalContent/Blog/1436/Pages/Blog-2015-03-01-01.aspx .


The Author would like to thank Polina Minchuk Macklin for her assistance with the Hebrew etymologies.