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Revealed: the Eye's Lymphatic System

Thanks to the plasma technology used in the Fugo Blade, Daljit Singh, M.D., an anterior segment surgeon who practices in Amritsar, India, has been able to demonstrate the existence of -- and display the activity of -- an elusive, fragile system of lymphatic vessels that covers a large portion of the scleral surface in the human eye.

As you know, the body normally conducts fluid through three channels: the arteries, veins and lymphatics. The lymphatics drain the interstitial excess body fluid that exists between the cells. Dysfunction of the lymphatic system can cause problems such as elephantitis, in which lymphatic occlusion results in a massively swollen, enlarged leg.

Because a lymphatic system in the eye was never observed, most doctors have assumed that fluid from the conjunctiva was drained by the veins of the eye. Now it appears that the absence of evidence may have been the result of the delicacy of the lymphatic channels; most techniques used to enter the eye damage them too much to allow them to function -- at least in view of the surgeon. The Plasma Blade, however, uses technology that cuts without producing resistance. This has allowed Dr. Singh to
create an opening into the lymphatic channels without damaging them.

Once an incision has been made, Dr. Singh places a small bolus of trypan blue at the opening of the lymphatic channels. Within seconds, the trypan blue progressively fills the otherwise invisible sausage-shaped lymphatic vessels. (See image, above.)

Trypan blue spreads through the system of lymphatic channels covering a large portion of the scleral surface in a patient's eye.

Dr. Singh's team has observed that subconjunctival lymphatics fall into three categories: localized nets of lymphatics, 180° circumferential vessels parallel to the limbus that drain the localized lymphatic nets, and two large vessels (at 6 and 12 o'clock) that drain the circumferential vessels and pass backwards deep into the orbit. The team refers to this system as "the storm drain system of the eye."

The discovery of the subconjunctival lymphatic channels has vast implications for our understanding of fluid management in the eye:

* The existence of the lymphatic "storm drain" system could have profound implications for explaining the genesis of glaucoma. It may also explain the success (or lack of success) of different treatments.

For example, Dr. Singh's research is indicating that the condition of the lymphatics at a given location may determine the success of a filtration bleb. If the lymphatics are poor because of disease or damage caused by previous surgery, the bleb may succeed in filtering fluid from inside the eye to a subconjunctival location, but the fluid will be trapped under the conjunctiva.

In fact, Dr. Singh has found that if the lymphatic system is functioning effectively, the ideal filtration bleb is a flat bleb, not a large bleb. Healthy conjunctival lymphatics drain fluid rapidly, thereby preventing large bleb formation.

As another example, initial results indicate that mitomycin may be contraindicated in glaucoma filtration because it appears to damage the lymphatics.

* In general, thanks to the existence of aqueous suppressants such as timolol maleate (Timoptic), the emphasis of glaucoma therapy has largely been on suppressing the production of aqueous fluid. Medications for increasing drainage of aqueous have been much less effective. Now that the existence of a lymphatic system has been demonstrated, researchers will be able to pursue new avenues of treatment related to the condition of the lymphatic system.

* As with glaucoma, the major therapeutic focus in cases of ocular inflammation and ocular infection has been on suppressing abnormal fluid in the ocular tissue. Now, if a patient displays chemosis of the eye from allergy or infection, surgeons will need to consider not only the source of the chemotic fluid, but also what's happening to the subconjunctival lymphatic system that's causing the fluid to be retained.

* To a large extent, cautery has been used indiscriminately in the past. However, the heat of cautery can inflict tremendous damage on the lymphatic system. Use of this option should probably be avoided in most surgical situations.

More information about the Fugo Blade is available from MediSURG R&MC at (610) 277-3937.