By Richard P. Wilson, M.D.
A clear watery fluid called aqueous is being produced by the ciliary body of the eye at all times. This fluid circulates through the front of the eye and exits through the trabecular meshwork, or drain of the eye, into the bloodstream. The ciliary body is a band of tissue just behind where the clear cornea meets the white of the eye. At this point, a laser can be focused to burn and destroy part of this tissue. The amount of decrease in aqueous production is proportional to the amount of the ciliary body destroyed by the laser.
Neodymium: YAG laser cyclophotocoagulation of the ciliary body is our final and last ditch procedure to save an eye from the glaucomas that are most difficult to control. It has been used at Wills Eye Hospital over the last four to five years with excellent success. Indeed, if the procedure can be repeated until intraocular pressure is controlled, the success rate is well up in the 90% range. However, everyone reacts differently. In some people only one treatment is adequate. In others three or four different treatments have been necessary over a one to three year period in order to permanently control their glaucoma.
This procedure is only used in eyes whose condition is such that attempts to create a drain would be totally unsuccessful. If one cannot increase the fluid outflow from the eye in order to control intraocular pressure, one must decrease the amount of fluid made. This accounts for the destructive nature of the surgery. Because the surgeon is actually trying to kill part of the tissue in the eye that makes fluid, there are significant risks associated with the procedure. These risks include pain in the postoperative period, marked inflammation of the outside and inside of the eye, and markedly decreased vision for a period of one to six weeks after the procedure. Twelve percent of patients during a four year study at Wills developed too low a pressure as their ciliary body was not healthy enough to sustain the damage from the laser and continue to make an adequate amount of fluid. In patients with good vision, this loss of intraocular pressure resulted in decreased vision. Less commonly seen complications include permanent decrease in visual acuity in those with advanced glaucoma or retinas susceptible to swelling with intraocular inflammation. There have been no instances of infection and bleeding is quite rare.
While these side-effects sound frightening, they are far better than the side-effects and complications associated with cyclocryotherapy, which has been the mainstay of difficult glaucoma management until the 1980’s. With this procedure, 12% of the treated eyes lost all pressure and in many cases much of their sight. Neodymium: YAG laser cyclophotocoagulation of the ciliary body is really a significant advance in the treatment of severe glaucomas that are resistant to other therapies. Patients with this kind of glaucoma cannot avoid risk. If they do nothing, their vision, and in some cases their eyes, will become lost. The vast majority of patients who have undergone this procedure have been markedly helped.