The destiny of accurate ophthalmologic informationwill largely be determined by a creative pursuit of

truth by the scientific community. This paper paves theway for an enlightened understanding of the presentlyconfusing issue of the ocular lymphatic system.

Lymphatics are seen throughout the body since theleakage of body fluid from the arterial system cannotbe fully absorbed by the venous system. From a phys-iologic point of view, how can the eye manage fluidimbalance if it lacks an extensive lymphatic system?Without lymphatics, the eye lacks a means of control-ling excess fluid. Yet, cornerstone texts pronounce aspectrum of views on ocular lymphatics from the eyecontains no lymphatics or perhaps to brief commentson ocular lymphatics, usually limited to less than 12sentences. This confusion probably stems from thefact that few have ever claimed to have seen lymphat-ics, therefore the ophthalmologic community visceral-ly does not understand them or really does not believein their existence. Rarely will you see a clinical publi-cation discuss a pathophysiologic theory based on theconjunctival lymphatics. It is understandable that wedoubt their existence since we fail “to see them” withour finest high-resolution microscopes. Herein, wepresent photographs from in vivo videotapes ofhuman conjunctival lymphatics draining vital stainfrom the subconjunctival space. Our videotapes arevisually stunning because one can see the brilliant

Daljit Singh, MD, Ravi Shankar Jit Singh, MD,Kiranjit Singh, MD, Seema K. Singh, MD, InduR. Singh, MD, Ravijit Singh, MD, & Richard J.Fugo, MD, PhD

The Conjunctival Lymphatic System

The conjunctival lymphatic system of the eye is presented and

research in this field is evaluated. Extensive photographic docu-

mentation of the lymphatic system is shown. The microanatomy of

the conjunctival lymphatic system is presented. The importance of

the ocular lymphatic system is also evaluated.

A B S T R A C T

Reprints:Richard Fugo, MD, Fugo Eye Institute, 100 W. Fornance, Norristown, PA 19401 USA

Drs. Daljit Singh, Ravi Shankar Jit Singh, Kiranjit Singh, Seema Singh, Indu Singh, andRavijit Singh are from the Dr. Daljit Singh Eye Hospital, Amritsar, India. Dr. Fugo isfrom the Fugo Eye Institute, Norristown, PA USA

Drs. Daljit Singh, Ravi Shankar Jit Singh, Kiranjit Singh, Seema Singh, Indu Singh, andRavijit Singh have stated that they do not have a significant financial interest or otherrelationship with any product manufacturer or provider of services discussed in thisarticle. Dr. Fugo has a financial interest in this product. The authors discuss the useof off-label products in the USA, which includes unlabeled, unapproved, or investiga-tive products or devices.

AcknowledgmentAcknowledgment is given to Jennifer Fugo for technical assistance.

O R I G I N A L A R T I C L E

ANN OPHTHALMOL. 2003;35(2):99–104 99

trypan blue outlining the lymph vessels over thecourse of 30–60 seconds. We have attempted to presentblack and white photographs in such a manner thatthey capture some of the dynamics and excitement ofour videotape documentation of the conjunctival lym-phatic system. We also present the histologic architec-ture of the conjunctival lymphatic system.

Method and MaterialSubjects. A total of 114 human eyes were studied inthe following sequence. They included: 12 humancadaver eyes were first subjected to our protocol andthen studied histologically; 12 human in vivo blindeyes were then subjected to the test protocol and thenwere followed clinically for 2 months; 60 human invivo pre-surgical filtration eyes were subjected to theprotocol to determine if a given section of conjunctivapossessed healthy lymphatics; and finally 30 humannon-glaucomatous eyes were then subjected to thestudy protocol.

Protocol. A 32-gauge needle was used to inject ster-ile trypan blue (0.1–0.3 mL) to form a small blue sub-conjunctival blister in the pretenons’ area along thelimbus. The pool of trypan blue was observed in orderto evaluate if it remained stagnant, or rather spreadaway from the blister forming distinct branch-liketributaries. Mitomyocin was applied to glaucoma filtersites in every other patient for the first 14 patients.This was stopped after the 14th patient since each ofthese patients developed large avascular conjunctivalblebs. This was determined to cause long-term tissuedamage. Avascular conjunctiva is neither desirablenor physiologic.

ResultsCadaver Eyes. No adverse pathology from the trypanblue was observed during histological examination ofthe cadaver eyes following subconjunctival injectionof trypan blue.

Blind Eyes. No adverse pathology from the trypan

blue was observed. Trypan blue was essentiallycleared from the conjunctiva in 4 to 24 hours, depend-ing on the integrity of the lymphatic system.

Normal Eyes. Each eye demonstrated branch-liketributaries filled with trypan blue.

Glaucoma Eyes. Filtration tracks placed in areaswhere the trypan blue remained pooled inevitablyprovided poor intraocular pressure (IOP) controldespite patent filtration tracks. Filtration tracksplaced in areas where the trypan blue pool formedbranch-like tributaries extending outward from thetrypan blue pool usually produced low filtration blebswith good IOP control. When these eyes formed largeblebs with poor IOP control, the usual cause wastenon cyst formation.

Herein, we present the microanatomy of the con-junctival lymphatic system (Figure 1) based on a com-bination of our research observations and observationsthat have been documented in the literature.

The Lymphatic Circle of Teichmann (Figures 2 & 3)

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Fig 1.—Cornea is in the upper right. The arrow points at where the injected bolus ofsubconjunctival trypan blue meets the limbus. The lymphatic tributaries to the left ofthe bleb are seen in the video of this surgery to progressively increase in size over a30 second period.

Fig 2.—Lymphatic Circle of Teichmann. Small, curly lymph vessels interdigitate withthe vascular arcade (not seen in this image) located along the limbus (Arrow) andabove Schlemm’s canal.

Fig 3.—Enlarged view of Figure 2. When seen in color, the small vessels of Teichmann(Arrow) are very prominent. The cornea is in the upper right.

is a very fine, circular plexus of lymph vessels, whichinterdigitate with the peripheral vascular arcades alongthe limbus. Some of these terminal lymphatics aresuperficial whereas others develop in a deeper level.

Radial Lymph Vessels (Figures 4 & 5) are seen per-pendicular to the lymphatic Circle of Teichmann alongthe limbus. Lymphatic vessels comprising the limbalCircle of Teichmann merge as they leave the limbus,forming a system of radial lymphatic vessels that draintoward the equator of the eye. These conjunctival radi-al lymphatics take either a superficial or deep path.

The superficial radial lymphatics are organized inthe rarely discussed, Palisades of Vogt (Figure 6). ThePalisades are an alternating thin, then thick perilim-bal epithelial layer. These Palisades are perpendicular

to the limbus. The thin epithelial layer has subepithe-lial stromal tissue beneath it, and is flanked by thick-ened epithelial tissue on both sides. This subepithelialstromal tissue acts as a radial aqueduct system inwhich arterial, venous and lymphatic vessels are con-tained. The deep radial lymphatic vessels branch outto form a network of lymphatic vessels that coursebelow the Palisades of Vogt. The superficial and deepradial vessels terminate peripherally in the Peri-corneal Lymphatic Ring.

Pericorneal Lymphatic Ring (Figures 7, 8 & 9) con-sists of two or more large collector channels, whichrun circumferentially 3 to 8 mm behind the limbus. Itremains parallel to the limbus and receives lymphfrom the radial lymph vessels. From the PericornealLymphatic Ring, lymph drains towards the back of theeye in vessels in the superior, inferior, medial and lat-eral quadrants. The lateral, superior and inferior ves-sels are usually composed of one or two large trunkvessels, whereas the medial channel is highly vari-able, often composed of a plexus of small vessels. Thelateral trunk vessel usually runs deep in the conjunc-tiva (Figure 10). The superior and inferior trunk runsuperficially and therefore, these two trunk vesselswere most frequently observed by our clinicalresearch. Regarding the next step for the lymph, webelieve that the preauricular (superficial parotid)lymph nodes appear to drain the lateral portion,whereas the submaxillary nodes drain the medial por-tion. The conjunctiva itself lacks lymph nodes.

Variation in microanatomy. Now that we have pro-vided a general outline of the structure of conjunctivallymphatics, we must emphasize that there exists agreat deal of variation in this outline. As we see in reti-nal vasculature or fingerprints, no two are the same.

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Fig 4.—Upper Left: 32 G needle injecting trypan blue along human eye limbus. UpperRight: 5 seconds after upper left photo, we see trypan blue flowing through lymphat-ic vessels. Lower Left: 6 seconds after upper right photograph, we see continued flowof trypan blue through lymphatic vessels. Lower Right: 8 seconds after lower left pho-tograph, we see radial lymphatic vessels (Left Arrow) feeding into the PericornealLymphatic Ring (Right Arrow). This patient shows two of these rings. The outer ringappears to be deeper in the conjunctiva.

Fig 6.—A high magnification view along the limbus with the cornea on the bottom ofthe photograph. The Palisades of Vogt (Arrow) are seen along the limbus as finger likeprojections that are perpendicular to the limbus. These are prominent in highly pig-mented eyes and may be enhanced with a yellow filter.

Fig 5.—High magnification view of trypan blue, outlining the lymphatic system in ahuman eye. The cornea is in the upper right. Right arrow points at the radial lym-phatic vessels, which feed into the Pericorneal Lymphatic Rings (Center Arrow). Thelymph then flows through the lateral trunk vessel (Left Arrow) which then drains intothe preauricular lymph nodes.

This is also true for conjunctival lymphatics. By exam-ining the photos in this paper, one can see the diversi-ty in conjunctival lymphatics. The lymph vessels areat times straight and smooth, while they may also beirregular in shape and configuration. We see that thereare locations where the walls balloon out, presentingthe appearance of small lymphatic lake that maybranch into lymph tributaries. This diversity shouldbe expected when one examines conjunctival arteriesand veins.

Discussion The history of ocular lymphatics is fascinating. It iseven more interesting to see how so much conjuncti-val lymphatic data from the past two centuries has

largely been dismissed by modern authors. Adler’sPhysiology of the Eye states that: “…the eye has nosystem of lymphatic vessels.”1 Fine and Yanoff’s Ocu-lar Histology states “Because of the standing popula-tion of lymphoid cells in the substantia propria, theconjunctival sac has been likened to an opened uplymph node…”2 Hogan and Alvarado’s classic textHistology of the Human Eye devotes eighteen lines oftext to the topic of conjunctival lymphatics plus onediagram and one histologic section.3 The best text onconjunctival/corneal lymphatics is System of Ophthal-mology by Duke-Elder.4 Yet, not a single one of thesetexts shows an actual photograph of the conjunctivallymphatic system.

The human body is composed of over 95% water.Therein, homeostatic regulatory mechanisms forwater are critical to the body. Under normal condi-tions, the arteries ooze 10%–15% more body fluid thanthe venous system can absorb. Yet, since we routinelyfail to see conjunctival lymphatics, we have ignoredthis physiologic imbalance when evaluating the con-

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Fig 7.—A 20 second sequence of trypan blue flowing through the lymphatics. UpperLeft: initial injection along limbus. Upper Right: trypan blue beginning to flow throughlymph channels. Lower Left: the Pericorneal Lymphatic Ring is now involved. LowerRight: the Pericorneal Lymphatic Ring (Arrows) is now filled with trypan blue on bothsides of the site of trypan blue injection.

Fig 8.—Varied drainage pattern in a 25 second trypan blue sequence. Top Left: begininjection. Top Right: Pericorneal Lymphatic Ring begins to form (Arrow). Lower Left:pericorneal lymphatic ring shows more involvement (Arrow). Lower Right: the Peri-corneal Lymphatic Ring opens into small lymphatic lacunae (lakes) in the conjuncti-va. Also, the left arrow points at a superficial network of lacunae while the right arrowpoints at a deeper network of lymphatic lacunae.

Fig 9.—A 19 second sequence shows the development of the Pericorneal LymphaticRing (Arrows).

Fig 10.—Deep lymphatic vessels are often obscured by overlying tissue (Arrows).

junctiva. In the body, this excess fluid loss is capturedby the lymphatic system. One author (D.S.) has calledthe lymphatic system of the eye the “storm drain sys-tem of the eye” and avascular filtration blebs as “ con-junctival elephantiasis”, a possible sign ofnon-functional lymphatics.

A few concepts on microanatomy are in order. Thelymphatic vessels usually are a larger caliber thanarterial capillaries and have a much thinner endothe-lial lining. The lymphatic vessels have no basementmembrane and lack pericytes or tight junctions. Thewalls of the lymph vessels consist mainly of fibrousconnective tissue. In some areas of the body, largerlymph vessels may contain a thin tunica media(smooth muscle), which rhythmically contracts tosqueeze the lymph in a forward motion. Internally, thelymphatics contain valves to prevent the lymph fromflowing toward the limbus (backflow). Unless they aredraining fluid, lymphatic vessels are frequently col-lapsed, therefore they can be very difficult to visualize.

The central corneal surface has about five layers ofepithelial cells. As we progress toward the limbus, theepithelial layer thickens. At the limbus, the epithelialcells become skin-like. Namely, the skin epidermis isnot uniform, but rather has deep indentations in itsstructure into which pegs of underlying corium pluginto the epidermis. These “rete pegs” create a strongmechanical bond between the epidermis and itsunderlying corium. Similarly, the thickened cornealepithelium along the limbus alternately thickens andthins about 125 times along the limbus. This wave ofthickening followed by thinning remains substantial-ly perpendicular to the limbus. The thinned corridorsof epithelial cells are about 0.5 mm wide and about 2–4mm long and are filled with upward projections ofunderlying stromal papillae, which is lined on eachside by the downward projection of thick epithelialrete pegs. The thin, long layer of epithelium with theupward projection of underlying stromal papillaeappear as whitish, thin finger projections perpendicu-lar to the limbus. These finger projections are calledthe Palisades of Vogt. These represent a mechanism tofirmly anchor the epithelium to the underlying stro-mal tissue as well as a means to organize the routingof artery, vein and lymphatic channels.5

In his classic text Textbook of Ophthalmology,Ernest Fuchs states that, “The cornea contains no ves-sels”. It goes on to say that, “In many places betweenthe lamellae formed from the bundles, open spaces ofgreater or smaller size exist, which are filled withlymph and are hence called lymph spaces.”6 Bowmanreported a system of lymph “tubules” in the cornea in1849. In 1860, Von Recklinghausen reported a compli-cated network of lymph channels in the cornea thatwere coined “Von Recklinghausen’s canals.”4

In the later 1800s and early 1900s, severalresearchers supported the findings of Bowman andVon Recklinghausen. In the mid 1900s, a work byWolter7 again supported the corneal lymphatic theorywhile studies by Friedman8 have often been cited as

proving that corneal lymphatics do not exist.4 Howev-er, reading the original paper by Friedman provides adifferent impression. The last paragraph of Fried-man’s paper states:

“ The subject is not a closed one. It is certain that theendothelial requisites for a true lymphatic systemare not to be found in the cornea, but by entopticmethods it is possible to demonstrate that some kindof channels do appear to exist. All we can say is thatas yet anatomic preparations have yielded onlymisleading artifacts and have been too crude to per-mit us to draw final conclusions.”As a matter of fact, this position presented by Fried-

man differs little from the description provided duringthe prior century by Fuchs.6 It should be understoodthat Fuchs’ text on ophthalmology was considered oneof the foremost classics in the field for decades. Eventoday, it remains truly fascinating reading with anextraordinary scientific approach to ophthalmology.Nonetheless, today the general consensus is thatcorneal lymphatics do not exist, but as we can see thisis really not known definitively (Figures 11 & 12).

The conjunctival lymphatics are another matter. In1861, Teichmann described a system of lymphaticarcades associated with limbal vascular loops.9 Thislymphatic ring was termed the “Lymphatic Circle ofTeichmann”. Between 1880 and 1965, a partial list ofauthors endorsing conjunctival lymphatics includes:Leber (1880), Folli (1894), Zimmerman (1899), Gruneit(1901), Most (1905), Bartels (1909), Elschrig (1915),Bartok (1917), Koeppe (1918), Stübel (1923), Knüsel(1923), Vogt (1930), Nataf (1951), Katagama (1951),Busacca (1955), Chinaglia (1955), Heydenreich (1956),Conrad & Kuhnhardt (1957), Stephanik (1958), andLeffertstra (1962).4

Nonetheless, the studies on the conjunctival lym-phatics have evidently not been sufficiently persua-sive for the ophthalmic community. Most textbookseither fail to discuss the subject or merely dismiss it inseveral sentences. More importantly, it is indeed rarefor authors of clinical publications to have pathophys-iologic mechanisms based on conjunctival lymphat-ics. This even includes texts in ocular immunology. Itis the authors’ contention that this belief, commonlyheld by the vast majority in our profession that con-junctival lymphatics don’t exist is largely due to a lackof convincing photographic evidence of this system.One goal of this work is to demonstrate photographi-cally that conjunctival lymphatics truly exist.

One of the authors (D.S.) has established an exten-sive video collection of trypan blue being absorbed bythe conjunctival lymphatics wherein the normallyinvisible lymphatics were rapidly visualized becausethey were filled with trypan blue. This same authorshowed color images of the conjunctival lymphatics inrecent journals.10-12

Ernest Fuchs referred to aqueous humor as the“lymphatic fluid of the eye.”6 One of the authors (D.S.)is using the plasma ablation of the Fugo Blade to cre-ate a 100-micron ablation pore through the sclera and

ANN OPHTHALMOL. 2003;35(2) 103

cilliary processes then into the posterior chamber.This procedure is called transciliary filtration (TCF)or Singh filtration. This causes aqueous to slowly oozefrom the posterior chamber and then subconjunctival-ly. He is employing this as a 5-minute glaucoma pro-cedure and also uses this to treat xerotic patients.Thereby, the conjunctiva is wetted from its internalsurface. In both cases, excess fluid is removed by theconjunctival lymphatics. Yet, not a single case of flatanterior chamber has been observed in over 400 eyes.In addition, no peripheral iridotomy is needed.

The limbal venous arcade is important for fluid man-agement from Schlemm’s canal. However, the Lym-phatic Circle of Teichmann is intimately interwovenwith the limbal vascular arcades sitting aboveSchlemm’s canal. Since the function of the lymphaticsis body fluid management and this lymphatic circleplexus rests above Schlemm’s canal, does this not pointstrongly at a significant role in aqueous drainage?

The lymphatic system is known to play a crucialrole in immunology. Many eye diseases have animmunologic component. Herein, the conjunctivallymphatic system must be explored to formulate ten-able explanations for ocular pathophysiology. Just con-sider the commonly seen bulbar form of vernal catarrh.

The object and goal of this work is to reintroducethe ophthalmic community to historical informationon the lymphatics, to present new data from ourresearch group and provide convincing evidence that

lymphatics actually do exist. Furthermore, we attemptto highlight that the importance of the lymphatics toocular homeostasis is immense. Ignoring the lym-phatics greatly limits our ability to appropriatelyexplain ocular physiology and pathology.

References1. Moses RA. Adler’s Physiology of the Eye. St Louis, MO: The C.V.

Mosby Company; 1981:200.2. Fine BS, Yanoff M. Ocular Histology. Hagerstown, MD: Harper

and Row; 1979:309.3. Hogan MJ, Alvarado JA, Weddell JE. Histology of the Human Eye.

Philadelphia, PA: W.B. Saunders Co.; 1971:121–126.4. Duke-Elder S, Wybar KC. The anatomy of the visual system. In:

Duke-Elder S, ed. System of Ophthalmology. Vol 2. St Louis, MO:The C.V. Mosby Company; 1961:119–551.

5. Busacca, A. Die Normale Limbusregion bei der Spaltlampen-mikroskopie und in Histologischen Praparaten. Stuttgart: Hoff-mannsche Buchdruckerei Felix Krais; 1934:634–652.

6. Fuchs E. Textbook of Ophthalmology. New York, NY: D. Appletonand Company; 1892:123–124.

7. Wolter J R. The trabecular endothelium. Arch Ophthalmol. 1959;61:928–38.

8. Friedman B. Nature of the corneal canals produced by perilimbalinjections of hydrogen peroxide. Arch Ophthalmol. 1953;50:688–95.

9. Teichmann D. Das Saugadersystem. Leipzig; 1861:1–121.10. Kent C. Revealed: the eye’s lymphatic system. Ophthalmol Man-

agt. 2002;6:114.11. Bethke W C. A new clue to lymphatic drainage? Rev Ophthalmol.

2002;9:12.12. Singh D. Letters: Conjunctival lymphatic system. J Cataract

Refract Surg. 2003;29;632–3.

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Fig 11.—Injection of trypan blue into a decompensated human cornea (30 secondsequence). Upper Left: injection begins in the decompensated cornea. Upper Right:trypan blue infiltrates through the cornea tissue then forms a ring around the limbus(Arrow). Lower Left: from the limbus, the trypan blue then enters radial lymphatic ves-sels (Arrow). Lower Right: the radial vessel then empties into the Pericorneal Lym-phatic Ring (Arrows). Trypan blue was only injected into the cornea, yet we see it beingdrained through the conjunctival lymphatic system.

Fig 12.—High magnification view of trypan blue being injected into a decompensat-ed cornea (large arrow on left). The stain is seen crossing the limbus and entering aradial lymphatic vessel (2 small arrows in center). The stain then enters the Peri-corneal Lymphatic Ring (3 large arrows on right). When seen in color, the trypan bluemakes this path stand out with a brilliant blue color.