DAN Answers Divers' Most-Asked Questions About Their Eyes
By Frank K. Butler Jr., Captain, Medical Corps, United States Navy
The Eye and Diving
Our eyes normally exist in a world where the pressure around them is the result of the combined weight of all of the gases in the earth's atmosphere. Diving exposes the eyes to increased pressures. While most of the time this has little or no negative effects on the diver, increased eye pressure in scuba diving can result in ocular decompression sickness and other dysbaric disorders. It may also raise new questions about the management of common eye conditions in divers. The issues discussed here, for the most part, historically have not been well addressed in ophthalmology literature.
Is it safe to dive after radial keratotomy?
Radial keratotomy (RK) is a surgical procedure designed to cure myopia (nearsightedness). In this operation, the surgeon makes a small number of radially-oriented incisions in the cornea of the eye. These incisions cause a decrease in the strength of the cornea and may increase the risk of serious injury if the eye is subjected to subsequent trauma, including barotrauma such as a facemask squeeze. Despite this theoretical risk, there have been no reports of which I am aware involving a traumatic rupture of the cornea resulting from diving after RK.
Divers who have had this procedure should wait at least three months after the surgery before returning to diving and should be careful to avoid a facemask squeeze - it's important to avoid imposing the "Boyle's Law Stress Test" on these corneal incisions.
If you are a diver and considering having this procedure done, I would recommend that you also ask your eye surgeon to discuss the potential advantages of photorefractive keratectomy, the alternative refractive surgical procedure discussed below.
Is it safe to dive after having had the new laser refractive surgery (photorefractive keratectomy, or PRK)?
Yes. This procedure uses laser reshaping of the cornea instead of incisions to treat myopia. This method results in no decrease in the structural integrity of the cornea and no risk of corneal rupture as a result of facemask squeeze. It should be safe to dive approximately two weeks after this surgery. Discuss your plans with your physician and have a final evaluation before you dive.
What are the best contact lenses to wear underwater?
Divers who wish to wear contact lenses while diving should ask their ophthalmologists or optometrists to prescribe "soft" contact lenses. "Hard" lenses or rigid gas-permeable lenses, the other two commonly prescribed types of lenses, have been found to sometimes cause symptoms of eye pain and blurred vision during and after dives, in which the diver accumulates a significant inert gas load. These symptoms occur as a result of gas bubbles forming between the cornea and the contact lens.
Can individuals who have had cataract surgery dive?
Yes. Most cataract surgeons now use surgical incisions designed to provide maximum post-operative wound strength. The recommended waiting time prior to returning to diving depends on exactly what type of incision was made. Ask your surgeon for recommendations for your particular type of surgery.
Is it dangerous to dive if you have glaucoma?
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.
Is it possible to get ocular (eye) decompression sickness?
Ocular decompression sickness is a relatively uncommon event, but one which does occur and it is very important that divers be aware of this possible presentation of DCS. Symptoms may include:
I just came up from a dive and noticed that my vision is now blurry. What conditions could cause this symptom?
Possible causes of blurred vision after diving include:
I just came up from a dive and one of my eyes has a bright red spot on it. What could cause this? Do I need to see an eye doctor?
The most common cause of a red spot on the eye after a dive is a subconjunctival hemorrhage. This is a collection of blood over the sclera (white part) of the eye. It is usually caused by a mild mask squeeze and does not require any treatment. A more severe squeeze could result in other injuries to the eye, however, so it is a good idea to see your eye doctor just in case. It is absolutely essential to see your eye doctor if you have eye pain, double vision, blind spots in your field of vision, or decreased vision after a dive or if you have a history of eye surgery in the past.
I am undergoing hyperbaric oxygen (HBO) treatments and have noticed that my vision is slowly getting worse. Why is this happening?
Hyperbaric oxygen therapy may cause a change in the way that the lens of the eye refracts light. This change occurs slowly and is usually not noticed until after a week or two of treatment. If the HBO therapy continues to that point or beyond, the patient may experience a slow myopic (nearsighted) change. This slow change typically continues as long as the HBO treatments continue. It is usually reversible after the treatments are finished, although there have been some reports in which this reversal did not occur or was incomplete.
What eye conditions would preclude someone from diving?
The increased pressures encountered while diving may cause a hollow orbital implant to collapse, resulting in cosmetic problems and a need for further surgery to replace the damaged implant.
Many ocular plastic surgeons are now using implants made of hydroxyapatite, a porous material which is not a contraindication for diving.
In general, it's best to wait until the underlying acute condition has resolved and there are no distracting or disabling ocular symptoms to contend with before returning to diving.
Deciding on your own visual acuity is primarily a judgment call, with few relevant scientific studies available to help resolve the issue. The approach taken in the article was to use statutory visual standards established for another hazardous activity - driving a car, for example - whose visual requirements are more demanding than diving. The recommendation made was that if you see well enough to qualify for a driver's license and operate a motor vehicle safely, then you should be able to see well enough to dive safely.
If a prospective diver has visual acuity which is poor enough to preclude him or her from being allowed to drive, then the fitness to dive decision needs to be individualized with the assistance of an eye physician and dive instructor.
Most of the restrictions to diving mentioned above do not apply to hyperbaric oxygen (HBO) therapy. According to "Diving and Hyperbaric Ophthalmology:"
Hyperbaric exposures in a dry chamber "do not entail immersion of the eye or the possibility of facemask barotrauma. Only the presence of intraocular gas or hollow orbital implants remain as possible ocular contraindications to diving in these patients."
If you have concerns about your eyes and diving, if you're planning to have surgery, or if you have further questions, call DAN's Dive Safety and Medical Information Line at +1-919-684-2948.
From the May/June 1998 issue of Alert Diver.