Glaucoma is a disease in which increased pressure inside the eye is associated with damage to the optic nerve and loss of vision. Because of this, physicians have voiced concern about the possibility that a hyperbaric environment might therefore cause increased damage to the eye. Although this would seem to be a logical conclusion, diving thus far has not been shown to be a problem for glaucoma patients. This is most likely because the damage associated with glaucoma is a factor of the difference between the pressure inside the eye and the surrounding pressure, rather than simply the absolute magnitude of the pressure inside the eye.
There are two important considerations for glaucoma patients who wish to dive. Some of the medications used to lower the pressure in the eyes of glaucoma patients may have adverse effects while diving. Timolol, for example, may result in a decrease in heart rate that could theoretically place a small percentage of divers at higher risk for loss of consciousness underwater; acetazolamide (diamox) may cause tingling sensations of the hands and feet that could be mistaken for symptoms of decompression sickness. These and other ocular medications are discussed in detail in the article mentioned in the introduction.
Certain types of glaucoma surgery (collectively called glaucoma filtering procedures) create a communication between the anterior chamber of the eye and the subconjunctival space to help lower the pressure in the eye. Facemask barotrauma may have an adverse effect on the functioning of the filter and result in a need for additional surgery or further damage to the eye from the glaucoma.
Individuals who have had glaucoma surgery or who are taking glaucoma medications should check with their ophthalmologist before diving.
For more information on vision issues, see the complete article by Frank K. Butler Jr., Captain, Medical Corps, United States Navy on High-Pressure Ophthalmology from Alert Diver.