Remarkable Old Kingdom Lensesand the Illusion of the Following Eye
A Recent Analytical Study of Egyptian Statuaryat the Louvre
Professor Jay Enoch of the School of Optometry at U.C.Berkeley delivered our November lecture on the unique lenses used in earlyOld Kingdom statuary. This lecture was based on research he undertook atthe Louvre on the famous seated scribe statue (E-3023) and a “reserve eye”from Saqqara (E-3009) from their collections along with other observationsmade on pieces found at the the Louvre and Egyptian Museum in Cairo.
These pieces share the common feature of the “illusionof the following eye” best observed at the museums when observing thesestatues with the aid of a pocket flashlight. Trained as an optical specialist,Dr. Enoch consulted an impressive list of other optical specialists andmany noted Egyptologists, including Berkeley’s own Dr. Kathleen Kellerand Dr. Carol Redmount trying to turn up answers to this interesting puzzle.
These early lenses appear fully formed about 2600-2575B.C.E. at Meidum in the famous statues of Rahotep and his wife Nofret andreappear sporadically in small statuary throughout the Fourth and FifthDynasties. The peak of development of these lenses was reached circa 2475B.C.E. The last Old Kingdom example being that of Mitri. AnotherFifth Dynasty statue, that of the funerary Priest Kaemked, had eye structureswhere the rock crystal lenses were replaced with obsidian, a dark volcanicglass. 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 FirstIntermediate period, the statue of King Hor found at Saqqara. Interestinglyenough, almost all of these statues are ka statues, the eyes being “theessence of the individual" in a real sense.
The composition of these eyes is a lens of polished rockcrystal (either alpha silica or fused silica, formerly known as cystallinequartz and fused quartz which had a convex front surface and a near hemisphericalconcave ground pupil surface in a flat iris plane (normally covered withresin) at the rear of the lens. The white of the eye (the sclera) was carved/groundin white limestone, cloudy or translucent quartz, or marble, some of thelatter contained impurities which simulate the conjunctive capillariesof the eye. These are set into the statue in copper (early forms)or bronze(late form) structures which simulate painted eyelids. they are said tosweep back to form a retina-like surface. Resins sometimes partiallyor fully obscure the pupillary aperture. This type of eye structure isknown as a form of “schematic eye”. The structures of these eyes indicateat a minimum a very advanced understanding of the anatomy of the eye forthat time. With the exception of the statue of Mitri (Fifth Dynasty), theeyes are well suited to the facial structures of the statues and Mitri’seyes may represent a medical condition with which he was afflicted or astylistic change.
The early examples of Nofret and Rahotep have well developedpupillary structures with thick lenses and a point as part of the pupillaryconcave ground rear lens, as did the reserve eye E-3009. The ka statueof King Hor has a ring in that ground surface instead of a point and thelens seems not as clear. Dr. Enoch noted that Late Period lenses foundby Flinders Petrie at Tanis are simply not in the same class as these muchearlier examples. The grinding and polishing of these eye lenses appearto be done in pairs, perhaps from the same larger crystal, and while notexactly the same, each eye is fairly close to the other in execution andtheir “eye following” ability.
Dr. Enoch noted that the quality of these eyes clearlyindicates that these could not have been “first attempts” and must representa development from earlier models which are lost or await discovery. Wheredid the technologies for these eyes develop and why were they permanentlyabandoned are important questions which also need further study. Certainlythe 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 collectionsin Cairo) - thus there are few examples of work done on early rock crystalpieces in current Egyptian collections. Could the lens technology havebeen imported from elsewhere and adapted to Egyptian stone working techniquesor were the eye structures themselves imports? These are questionswhich need to be addressed. Egyptian trade routes extended far beyond itsborders in the Old Kingdom and early dynastic period.
The schematic eye may be best studied with a “reserveeye” 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 placein any statue. Where did the materials come from to create this schematiceye and how were they worked? Indications from the snugness of the fitin these eyes suggest they may have been turned on a lathe. Egyptian stoneworking techniques (shown in a jewelry making scene from the tomb of Mererukaat Saqqara) demonstrate the use of the bow drill for cutting stone, probablywith an abrasive such as corundum (found in the Levant in the CycladesIslands and Anatolia and also from the Indus Valley) or emery sands fromEgypt’s own eastern desert. Dr. Enoch pointed out that low speed drillingwith 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 “goodold-fashioned spit”.
A number of opitcal and opthalmic tests were performedon the reserve eye and the scribe Accroupi, a number of which worked whileothers did not. A keratometer (a device normally used for examining thecornea of a real eye) was used to measure the convex lens mirror surfaceof the lenses, which were shown to have astimagic errors. It is interestingto note that virtually all ancient lenses demonstrate astigmatism (a structuraldefect in a lens or eye that prevents light rays from an object from meetingin a single focal point, so the object appears indistinctly formed). Theconstruction of the reserve eye lens (see the two drawings below) resultsin certain findings which are very close to real human eyes. The imageof the pupil of a real eye lies at circa 3.6 mm from the front surfacewhile the image of the pupil of the schematic reserve eye lies at circa4.6/4.7 mm. Direct measurement of the reserve eye diameter was 14.33 mm,while photographic records of the schematic eye measured 14.2 mm - a remarkableconcurrence of measurements, all things considered. The pupil imagewas 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 pupilimage 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 thicknessof these lenses proved a surprise! These lens/eye structures were clearlydesigned to enhance the eye following illusion, and were not meant to whollymimic real eye structures. These creations utilize defined convex and concavesurfaces. Of the pieces examined by Dr. Enoch, the seated scribe from theLouvre has the finest “eye following” ability.
This line of inquiry opens up as many areas of study asit answers. Dr. Enoch reiterated his amazement at the technological achievementsthese schematic eyes represent, particularly at such an early period inhuman culture. He knows of no other lenses with these unique “eye following”abilities, past or present. That these lenses were so unique, so well constructedand polished, and so complex suggests that these oldest lenses were notthe first lenses.
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