SCUBA Diving and Glaucoma: Pressure, Perfusion, and Post-Surgical Precautions

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Introduction Scuba diving has become a popular recreational sport, but it poses unique challenges for eye health. Divers are exposed to rapid ambient pressure changes underwater, which can influence intraocular pressure (IOP) and blood flow in the eyes. People with glaucoma – a condition where elevated IOP can damage the optic nerve – may worry about the effects of diving. Fortunately, experts report that diving per se hasn’t been shown to worsen glaucoma, likely because diving affects the difference between the pressure inside the eye and the surrounding water, not just the eye’s absolute pressure (). Nonetheless, divers with glaucoma must take precautions. This article reviews how water pressure, mask squeeze, and equalization affect IOP and ocular perfusion, weighs the health benefits of diving against its risks for glaucoma patients, and offers practical guidelines. Every recommendation is grounded in current research and best practices.How Underwater Pressure Affects the Eye Underwater, pressure increases by about one atmosphere every 10 meters (33 feet) of depth. In theory, higher external pressure could compress the eyeball and raise IOP. However, studies generally show the opposite effect: diving or simulated high-pressure environments tend to lower IOP slightly () (). For example, a recent systematic review found that experimental hyperbaric studies often reported reduced IOP under increased pressure (). One trial observed an ~8% drop in IOP measured 30 minutes after a 25-meter dive (); another noted that IOP remained below baseline even during the dive. The reasons are not fully understood, but may include changes in blood flow and oxygenation.Diving also alters ocular perfusion pressure (the difference between arterial blood pressure and IOP). Immersion and cold water trigger peripheral vasoconstriction, which can raise overall blood pressure. This tends to increase ocular perfusion pressure (). In concert, high blood oxygen levels (hyperoxia) cause constriction of retinal and choroidal blood vessels. In fact, one review notes that hyperbaric oxygen often causes ocular vasoconstriction and choroidal thinning, which can further reduce IOP (). In summary, the net effect of diving physiology seems to be a modest decrease in IOP and an increase in perfusion pressure – potentially beneficial for glaucoma if the optic nerve receives more blood flow. Still, the effects may vary and are incompletely understood.Mask Squeeze and Equalization A special concern for divers is the pressure difference between a diver’s mask and the surrounding water. Without equalization, the mask can “suck” on the face and eyes as the pressure increases, a phenomenon known as mask squeeze. To avoid this, divers are trained to equalize the mask by gently exhaling air through the nose into the mask during descent (). This keeps the internal mask pressure nearly equal to the ambient pressure. According to diving experts, skipping equalization can cause serious ocular barotrauma (): the vacuum can pull on the eye and eyelids, leading to bruising (periorbital ecchymosis), lid swelling, and subconjunctival hemorrhages (bleeding under the conjunctiva) (). In severe cases, it can even cause bleeding inside the eye (hyphema) or in the or

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Introduction. Scuba diving has become a popular recreational sport, but it poses unique challenges for eye health. Divers are exposed to rapid ambient pressure changes underwater, which can influence intraocular pressure, IOP, and blood flow in the eyes. People with glaucoma, a condition where elevated IOP can damage the optic nerve, may worry about the effects of diving. Fortunately, experts report that diving per se hasn't been shown to worsen glaucoma, likely because diving affects the difference between the pressure inside the eye and the surrounding water, not just the eye's absolute pressure. Nonetheless, divers with glaucoma must take precautions. This article reviews how water pressure, mask squeeze, and equalization affect IOP and ocular perfusion, weighs the health benefits of diving against its risks for glaucoma patients, and offers practical guidelines. Every recommendation is grounded in current research and best practices. How underwater pressure affects the eye. Underwater, pressure increases by about one atmosphere every 10 meters, 33 feet of depth. In theory, higher external pressure could compress the eyeball and raise IOP. However, studies generally show the opposite effect. Diving or simulated high-pressure environments tend to lower IOP slightly. For example, a recent systematic review found that experimental hyperbaric studies often reported reduced IOP under increased pressure. One trial observed an 8% drop in IOP measured 30 minutes after a 25-meter dive. Another noted that IOP remained below baseline even during the dive. The reasons are not fully understood, but may include changes in blood flow and oxygenation. Diving also alters ocular perfusion pressure, the difference between arterial blood pressure and IOP. Immersion and cold water trigger peripheral vasoconstriction, which can raise overall blood pressure. This tends to increase ocular perfusion pressure. In concert, high blood oxygen levels, hyperoxia, cause constriction of retinal and choroidal blood vessels. In fact, one review notes that hyperbaric oxygen often causes ocular vasoconstriction and choroidal thinning, which can further reduce IOP. In summary, the net effect of diving physiology seems to be a modest decrease in IOP and an increase in perfusion pressure, potentially beneficial for glaucoma if the optic nerve receives more blood flow. Still, the effects may vary and are incompletely understood. Mask squeeze and equalization. A special concern for divers is the pressure difference between a diver's mask and the surrounding water. Without equalization, the mask can suck on the face and eyes as the pressure increases, a phenomenon known as mask squeeze. To avoid this, divers are trained to equalize the mask by gently exhaling air through the nose into the mask during descent. This keeps the internal mask pressure nearly equal to the ambient pressure. According to diving experts, skipping equalization can cause serious ocular barrow trauma. The vacuum can pull on the eye and eyelids, leading to bruising, periorbital echemosis, lid swelling, and subconjunctival hemorrhages, bleeding under the conjunctiva. In severe cases, it can even cause bleeding inside the eye, hyphema, or in the orbit. In practice, experienced divers avoid mask squeeze entirely and typically equalize early in each descent. It's also recommended to use a low-volume scuba mask, a modern design with a small internal airspace, which makes pressure changes easier to manage. In fact, one study on healthy subjects found that simply putting on a well-fitted diving mask did not raise IOP, unlike tight swimming goggles. The mask's larger frame distributes pressure over the bony orbit rather than squeezing the soft eyelids. This suggests a properly fitted dive mask poses less risk to eye pressure than tight goggles. Diving with glaucoma benefits and risks. Health benefits of diving scuba diving offers excellent low-impact exercise and stress relief, which can be good for glaucoma patients. Diving is physically active, swimming against water's resistance strengthens the heart and muscles. Studies show that moderate aerobic exercise, such as swimming or jogging, lowers IOP afterward. For example, IOP after walking or running was consistently lower than before exercise, and the drop was greater for longer or more intense workouts. This mirrors what diving studies found. IOP often drops during or after a dive. In addition, water exercise is gentle on the joints. The resistance of water reduces the stress on joints and muscles, making activities like swimming or diving particularly attractive for older adults. Beyond exercise, diving may improve mental well-being. Many divers describe a calming, zen-like feeling underwater. Controlled breathing and breath holding mimic aspects of meditation or yoga, helping to reduce anxiety. A study noted that divers reported significantly lower stress, anxiety, and insomnia after diving. In short, the combination of natural beauty, focused breathing, and a supportive diving community can reduce stress levels, and stress reduction itself may help glaucoma, since high stress can transiently raise IOP. Thus, for a stable glaucoma patient, diving can be a healthy, low-stress way to stay active. Potential risks for glaucoma patients. Despite these benefits, certain aspects of diving could pose risks for people with glaucoma. Mask squeeze and blebs. As noted, mask squeeze can cause ocular hemorrhages. Of special concern are eyes with a filtering bleb from trabeculectomy, glaucoma surgery. A filtration bleb is a thin, delicate drainage pouch on the eye's surface. Expert reviewers warn that a thin bleb may not withstand the brief negative pressure during mask squeeze. In theory, a bleb could collapse or deflate the eye, potentially causing internal bleeding such as a choroidal hemorrhage, bleeding behind the retina, or hypotony, extremely low IOP underwater. For example, glaucoma specialist Robert Rich and colleagues note that weak mitamycin-enhanced blebs might not tolerate diving and could lead to dangerous bleeding. Therefore, any diver with a new or fragile bleb should be extremely cautious. Post-surgical eye stability. Besides trabeculectomies, tube shunts and less invasive MIGs procedures also alter aqueous flow. Tube shunts, like omid valves, have an external plate, but these generally seal well and may pose less risk than an open bleb. MIGs, such as eye stent or trabecular bypass devices, do not leave an external bleb, so theoretically they carry less barotrauma risk. However, any recent eye surgery, within weeks to a few months, is a concern. For safety, most ophthalmologists advise waiting several weeks after glaucoma or other intraocular surgery before resuming diving until the wounds in any bleb have fully healed. Medication effects. Some glaucoma medications can interact with diving. The Divers Alert Network notes that topical beta blockers, e.g., potentially increasing the risk of underwater blackout in susceptible individuals. Similarly, carbonic anhydrase inhibitors, like acetazolamide, used for pressure and also as a prophylactic for altitude sickness, can cause numbness or tingling in hands and feet, which could be confused with decompression sickness. Eyes with uncontrolled IOP or recent pressure spikes might also bleed into the eye during stress, though this is more a hypothetical risk. In practice, any diver on glaucoma meds should review their regimen with a doctor before diving and consider switching to less systemically active options if needed. Visual field loss. Glaucoma causes loss of peripheral vision. Underwater, good vision in all directions helps avoid hazards like rocks, boats, or buddies. A diver with significant field loss may have tunnel vision and could easily become disoriented or miss important cues. While there is no fixed rule, advanced field loss in one or both eyes would raise safety concerns. Some dive organizations require at least 2040 vision in one eye, though typical scuba gear with mask usually corrects for nearsightedness. Ultimately, a diver with severe visual field impairment may be considered unsafe to dive because of impaired spatial awareness. This is especially important in cold or murky water, where low visibility already challenges all divers. Decompression effects. Rapid pressure changes can cause gas bubbles in the bloodstream, decompression sickness. The eye is highly vascular, so bubbles could theoretically affect the retina or optic nerve. There are rare reports of ocular decompression sickness, retinal or choroidal gas emboli, which can cause visual disturbances. However, these cases are extremely uncommon and relate more to unsafe ascent profiles than to glaucoma itself. Adhering to slow, controlled ascents is the key preventive measure. See below. Safe diving practices for glaucoma patients. Fit and equalize your mask properly. Choose a scuba mask that fits well but isn't overtight. Low-volume masks, modern designs with less internal space, are recommended as they allow easy equalization and less suction force. Adjust the mask's skirt, seal, snugly over the eye socket bone, but avoid excessive strap pressure on the eyelids. During descent, equalize continuously. Gently exhale air through your nose into the mask at least once every few meters. Do not dive with your mask unequalized. As noted, even one missed equalization can tear conjunctival vessels. Between equalizations, it's fine to maintain a slight negative pressure to keep the mask sealed. If your ears or mask do not equalize easily due to congestion or equipment issues, abort the dive. Proper equalization keeps the inside mask pressure almost the same as outside water pressure, preventing barrow trauma without significantly spiking IOP. In fact, one study found that wearing a scuba mask mildly lowered IOP in normal subjects. But always lean on the side of caution. If anything feels wrong, ascend a bit and equalize, rather than ride it out. Ascend slowly and avoid breath holding. Follow standard dive procedures. Never ascend faster than about 10 meters, 33 feet per minute. Going slowly and performing any required safety stops helps off-gas inert nitrogen and minimizes the risk of decompression sickness. It also ensures that pressure changes around the eyes are gradual. Importantly, do not hold your breath when ascending. Holding breath can cause lung overexpansion and bubble formation, and it also pushes more blood volume back toward the head, transiently raising intracranial and eye pressure. Instead, breathe normally and ascend at a safety conscious pace. Monitor intraocular pressure and vision. Before diving, make sure your glaucoma is stable. This means your IOP is well controlled with medications or prior surgery and hasn't spiked recently. If possible, get a recent ophthalmology exam so your doctor can measure IOP and assess the optic nerve and visual fields. If you have a filtration bleb, ask the doctor to check its integrity. A well-healed, diffuse bleb is less worrisome than a tight, high bleb. During your dive trip, pay attention to any eye symptoms, redness, vision changes, during or after dives. If you experience unusual eye pain, double vision, or sudden vision loss, abort diving and seek medical attention immediately. It's also wise to avoid diving if you have an acute eye problem like angle closure glaucoma or a severe ocular infection. These conditions would be absolute contraindications. On the other hand, mild open-angle glaucoma that is controlled with drops is usually only a relative concern. Plan dives appropriate to your condition. Even healthy divers should avoid unnecessarily deep or strenuous dives. For a diver with glaucoma, conservative dive planning is prudent. Stay within recreational depth limits, typically 18 to 30 meters depending on certification and air supply, and prefer day dives over technical deep dives. Maintain good buddy communication so your partner is aware of any vision issues you may have. If visibility is poor, consider diving in a well-lit site or at a time of day when visibility is better. Always use the buddy system, never dive alone, especially if you have any impairment. Keep emergency procedures in mind. Have a dive slate or underwater communicator so you can signal problems to your buddy. After the dive, discuss how you feel, eye discomfort, headache, etc. To catch any early signs of disparic illness. Post-surgery and vision considerations. After filtering, trabeculectomy, or shunt surgery, most ophthalmologists recommend waiting several weeks to months before diving post-surgery to allow the eye and any bleb or incision to heal fully. Some sources even advise that it is generally not recommended to dive after glaucoma filtering surgery due to pressure changes affecting the surgical site. If you have a recent trabeculectomy with mitomycin C bleb, consider this a strong caution or contraindication until the bleb is stable and well evaluated by your surgeon. Tube shunts, valves, may carry less risk, but discuss individually. If you have an external device like a Molteno or Bearvelt implant, ensure the plate and wound are secure. If you had cataract surgery with an implant, most dive medicine guidelines say it's safe after a few weeks once the incision has sealed, similar to routine cataract clearance timelines. But freshly operated eyes of any kind should always wait for a specialist's clearance. Visual field loss, monocular vision. Dive operators typically require diver vision of at least 2040 in one eye, with or without correction. However, peripheral field requirements are not clearly defined in standards. Practically, if your glaucoma has caused significant tunnel vision or asymmetric field loss, you must consider how that affects underwater safety. A conservative rule is: if you cannot comfortably perceive and avoid obstacles or see your buddy with both eyes, diving is risky. Advanced bilateral field loss is generally a relative contraindication. Discuss this openly with your ophthalmologist and dive physician. In mild cases, training, staying close to your buddy, scanning frequently, can mitigate some risk. Fit to dive decision framework. When deciding if a glaucoma patient is fit to dive, an ophthalmologist and dive medicine specialist should collaborate. Consider the following checklist. Ophthalmic assessment. Confirm the type stage of glaucoma, current IOP, and visual field status. Examine for any surgical blebs, implants, or corneal pathology. Check that surgically treated eyes have healed well, no leaks, secure blebs. Disease stability. Has IOP been stable on treatment? No recent pressure spikes or acute events? Stable, well-controlled open-angle glaucoma is a lower-risk scenario. Uncontrolled or quickly progressing glaucoma is higher risk. Medication review. Note all glaucoma drops. If on systemic carbonic anhydrase inhibitors, acetolamide, methazolamide, or non-selective beta blockers, discuss alternatives or dosing adjustments to minimize side effects underwater. Vision requirements. Ensure adequate visual acuity, per dive certification standards, and functional visual field. If glasses contact lenses are used, verify they can be worn under a mask. Soft contacts are usually fine. Medical clearance. If the above factors are acceptable, issue a dive clearance with tailored advice. If there are concerns, e.g., new bleb, advanced field loss, the clearance may be limited or deferred. Dive plan and precautions. Emphasize gentle descent ascent, frequent mask equalization, and buddy awareness of vision issues. Reinforce adherence to safe dive profiles, max 10 m per mince ascent. No single factor automatically bans a glaucoma patient from diving. The final decision depends on a risk-benefit discussion, the patient's enthusiasm and fitness versus the severity of their eye condition. Commercial dive certification agencies may require a medical examiner's sign-off. Ultimately, an informed ophthalmologist's and divers' judgment guides safety. Conclusion. In summary, scuba diving and glaucoma can be compatible with care. Most studies indicate that when done properly, diving does not significantly harm the eye pressure in glaucoma. In fact, IOP often slightly decreases during dives. Diving offers good low-impact exercise and stress relief, both positive for overall glaucoma health. However, specific precautions are essential. Divers must equalize their masks to prevent barotrauma, use properly fitting masks, and follow slow ascent rules. Those with recent glaucoma surgery, especially fragile filtering blebs or very advanced disease, should avoid or postpone diving until fully evaluated. Any diver with glaucoma should carry a note in their dive log or medical alert that they have treated glaucoma and detail their eye surgeries meds. Above all, communication with an ophthalmologist is key. Before diving, patients should have a thorough eye exam and a frank discussion of risks. With stable glaucoma, good diving habits, and expert guidance, many patients can continue to enjoy the benefits of diving safely. All links to sources are available in the text version of this article. You can find the full article at VisualFieldTest.com. Thanks for listening. To check your visual field, click the link at the bottom of this article or visit visualfieldtest.com.