Remarkable Old Kingdom Lenses and the Illusion of the Following Eye
A Recent Analytical Study of Egyptian Statuary at the Louvre
Professor Jay Enoch of the School of Optometry at U.C. Berkeley delivered our November lecture on the unique lenses used in early Old Kingdom statuary. This lecture was based on research he undertook at the Louvre on the famous seated scribe statue (E-3023) and a “reserve eye” from Saqqara (E-3009) from their collections along with other observations made on pieces found at the the Louvre and Egyptian Museum in Cairo.
These pieces share the common feature of the “illusion of the following eye” best observed at the museums when observing these statues with the aid of a pocket flashlight. Trained as an optical specialist, Dr. Enoch consulted an impressive list of other optical specialists and many noted Egyptologists, including Berkeley’s own Dr. Kathleen Keller and Dr. Carol Redmount trying to turn up answers to this interesting puzzle.
These early lenses appear fully formed about 2600-2575 B.C.E. at Meidum in the famous statues of Rahotep and his wife Nofret and reappear sporadically in small statuary throughout the Fourth and Fifth Dynasties. The peak of development of these lenses was reached circa 2475 B.C.E. The last Old Kingdom example being that of Mitri. Another Fifth Dynasty statue, that of the funerary Priest Kaemked, had eye structures where the rock crystal lenses were replaced with obsidian, a dark volcanic glass. In the Sixth Dynasty, there are no known examples of these eye structures. These elegant lenses/eyes then reappeared in a single example in the First Intermediate period, the statue of King Hor found at Saqqara. Interestingly enough, almost all of these statues are ka statues, the eyes being “the essence of the individual" in a real sense.
The composition of these eyes is a lens of polished rock crystal (either alpha silica or fused silica, formerly known as cystalline quartz and fused quartz which had a convex front surface and a near hemispherical concave ground pupil surface in a flat iris plane (normally covered with resin) at the rear of the lens. The white of the eye (the sclera) was carved/ground in white limestone, cloudy or translucent quartz, or marble, some of the latter contained impurities which simulate the conjunctive capillaries of the eye. These are set into the statue in copper (early forms)or bronze (late form) structures which simulate painted eyelids. they are said to sweep back to form a retina-like surface. Resins sometimes partially or fully obscure the pupillary aperture. This type of eye structure is known as a form of “schematic eye”. The structures of these eyes indicate at a minimum a very advanced understanding of the anatomy of the eye for that time. With the exception of the statue of Mitri (Fifth Dynasty), the eyes are well suited to the facial structures of the statues and Mitri’s eyes may represent a medical condition with which he was afflicted or a stylistic change.
The early examples of Nofret and Rahotep have well developed pupillary structures with thick lenses and a point as part of the pupillary concave ground rear lens, as did the reserve eye E-3009. The ka statue of King Hor has a ring in that ground surface instead of a point and the lens seems not as clear. Dr. Enoch noted that Late Period lenses found by Flinders Petrie at Tanis are simply not in the same class as these much earlier examples. The grinding and polishing of these eye lenses appear to be done in pairs, perhaps from the same larger crystal, and while not exactly the same, each eye is fairly close to the other in execution and their “eye following” ability.
Dr. Enoch noted that the quality of these eyes clearly indicates that these could not have been “first attempts” and must represent a development from earlier models which are lost or await discovery. Where did the technologies for these eyes develop and why were they permanently abandoned are important questions which also need further study. Certainly the Egyptians had learned to work hard stones early in their civilization (Dr. Enoch noted there are only limited examples of quartz beads, a quartz “whiskey-like shot glass” and a carved quartz lion in the predynastic collections in Cairo) - thus there are few examples of work done on early rock crystal pieces in current Egyptian collections. Could the lens technology have been imported from elsewhere and adapted to Egyptian stone working techniques or were the eye structures themselves imports? These are questions which need to be addressed. Egyptian trade routes extended far beyond its borders in the Old Kingdom and early dynastic period.
The schematic eye may be best studied with a “reserve eye” found in the Louvre (E-3009) since it is not blocked with any resins, the top is open for viewing, looking at the image plane and is not in place in any statue. Where did the materials come from to create this schematic eye and how were they worked? Indications from the snugness of the fit in these eyes suggest they may have been turned on a lathe. Egyptian stone working techniques (shown in a jewelry making scene from the tomb of Mereruka at Saqqara) demonstrate the use of the bow drill for cutting stone, probably with an abrasive such as corundum (found in the Levant in the Cyclades Islands and Anatolia and also from the Indus Valley) or emery sands from Egypt’s own eastern desert. Dr. Enoch pointed out that low speed drilling with an abrasive can easily account for the lenses seen in these statues, perhaps using papyrus stem drills and a slurry of water and emery or “good old-fashioned spit”.
A number of opitcal and opthalmic tests were performed on the reserve eye and the scribe Accroupi, a number of which worked while others did not. A keratometer (a device normally used for examining the cornea of a real eye) was used to measure the convex lens mirror surface of the lenses, which were shown to have astimagic errors. It is interesting to note that virtually all ancient lenses demonstrate astigmatism (a structural defect in a lens or eye that prevents light rays from an object from meeting in a single focal point, so the object appears indistinctly formed). The construction of the reserve eye lens (see the two drawings below) results in certain findings which are very close to real human eyes. The image of the pupil of a real eye lies at circa 3.6 mm from the front surface while the image of the pupil of the schematic reserve eye lies at circa 4.6/4.7 mm. Direct measurement of the reserve eye diameter was 14.33 mm, while photographic records of the schematic eye measured 14.2 mm - a remarkable concurrence of measurements, all things considered. The pupil image was circa 1/4 of the diameter of the front lense of the schematic eye. The illusion of the following eye results from a form of image parallax, that is, the main factor is the appearance of the location of the pupil image perceived as you move around the eye structure.
Dr. Enoch’s team was unable to measure the birefringence (double refracting property) of these rock crystal lens elements. The technique used was bot meant for so thick a lens element. The thickness of these lenses proved a surprise! These lens/eye structures were clearly designed to enhance the eye following illusion, and were not meant to wholly mimic real eye structures. These creations utilize defined convex and concave surfaces. Of the pieces examined by Dr. Enoch, the seated scribe from the Louvre has the finest “eye following” ability.
This line of inquiry opens up as many areas of study as it answers. Dr. Enoch reiterated his amazement at the technological achievements these schematic eyes represent, particularly at such an early period in human culture. He knows of no other lenses with these unique “eye following” abilities, past or present. That these lenses were so unique, so well constructed and polished, and so complex suggests that these oldest lenses were not the first lenses.
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