A medieval fallacy: the crystalline lens in the center of the eye

Abstract

ObjectiveTo determine whether, as most modern historians have written, ancient Greco-Roman authors believed the crystalline lens is positioned in the center of the eye.BackgroundHistorians have written that statements about cataract couching by Celsus, or perhaps Galen of Pergamon, suggested a centrally located lens. Celsus specifically wrote that a couching needle placed intermediate between the corneal limbus and the lateral canthus enters an empty space, presumed to represent the posterior chamber.MethodsAncient ophthalmic literature was analyzed to understand where these authors believed the crystalline lens was positioned. In order to estimate where Celsus proposed entering the eye during couching, we prospectively measured the distance from the temporal corneal limbus to the lateral canthus in 30 healthy adults.ResultsRufus of Ephesus and Galen wrote that the lens is anterior enough to contact the iris. Galen wrote that the lens equator joins other ocular structures at the corneoscleral junction. In 30 subjects, half the distance from the temporal corneal limbus to the lateral canthus was a mean of 4.5 mm (range: 3.3–5.3 mm). Descriptions of couching by Celsus and others are consistent with pars plana entry of the couching needle. Anterior angulation of the needle would permit contact of the needle with the lens.ConclusionAncient descriptions of anatomy and couching do not establish the microanatomic relationships of the ciliary region with any modern degree of accuracy. Nonetheless, ancient authors, such as Galen and Rufus, clearly understood that the lens is located anteriorly. There is little reason to believe that Celsus or other ancient authors held a variant understanding of the anatomy of a healthy eye. The notion of the central location of the lens seems to have arisen with Arabic authors in 9th century Mesopotamia, and lasted for over 7 centuries.

The history of cataract surgery: from couching to phacoemulsification

“…(The ancients did not use the term pars plana, or have a modern understanding of the anatomy of this region. However, previous work (141), as well as the analysis presented below, suggest that in antiquity the couching instrument entered the eye at the pars plana). In the earliest Roman work (Celsus) and earliest Indian works (Suśruta and Vāgbhaṭa) the primary instrument (needle or rod) is directly applied to, and punctures, the sclera at the pars plana.…”

Ophthalmology in North America: Early Stories (1491-1801)

“…Placing the couching needle 1/6 in (4.2 mm) posterior to the limbus results in pars plana entry. 181 As the needle is observed just anterior to the lens, rather than the iris, the needle passed posterior to the iris. Thus, the general approach to couching had not changed since described by Celsus in the first century.…”

“…Thus, the general approach to couching had not changed since described by Celsus in the first century. 181 …”

A Family of Early English Oculists (1600-1751), With a Reappraisal of John Thomas Woolhouse (1664-1733/1734)

“…Prior to the 18th century, the cataract which was displaced by couching was believed to be a membrane anterior to the lens. 2 The lens itself was considered the seat of vision, as we might view the retina today.…”

“… 1 Surgeons learned that a cataract is an opacity of the crystalline lens and not an opacity anterior to the lens, as had been believed since antiquity. 2 Angle-closure glaucoma was described in detail. 3 , 4 Other procedures performed included posterior synechiolysis and dacryocystectomy.…”