diving and undersea medicine for the non-medical diver, the non-diving
physician and the specialist.
Fitness to Dive: Eye Problems
and the Instructor
The ocular aspects of scuba diving and other hyperbaric exposures were reviewed in a landmark paper by Dr. Frank Butler in 1995. [Butler FK: Diving and hyperbaric ophthalmology, Surv Ophthalmol 39:347, 1995.] Most of the material included here are condensations of sections of that paper and more recent articles reviewed by Dr. Butler.
Pressure and the Eye
Normal intraocular pressure as measured by a tonometer is usually read as 15 mm. Hg. This is absolute “gauge” pressure and is actually 775 mm of Hg. [775 less 760 = 15]. The eye ball is fluid filled and changes in pressure are experienced equally throughout the eye. Any gas in the eye will be affected by pressure changes as would any other gas containing space and decrease in size with depth and increase in size with ascent. [Boyle's Law].
Eye Considerations in the Fitness-to-Dive Evaluation
---Ability to see.
A diver should have adequate visual acuity to be able to read his or her gauges and perform safely underwater. Possession of a driver’s license is corollary evidence that a potential diver has sufficient visual acuity to meet this standard.
---Recent eye surgery
A person who has recently undergone ophthalmic surgery should refrain from diving until the recommended convalescent interval has passed.
Individuals who suffer from glaucoma may dive safely unless they have had 'filtering' surgery performed. Medications [carbonic anhydrase inhibitors] are best avoided in glaucoma patients who wish to dive because of possible confusion between medication-induced neurological symptoms [paresthesias] and decompression sickness.
---Acute eye disorder
Any individual who is suffering from an acute ocular disorder that causes significant pain, decreased visual acuity, or other disabling symptoms should refrain from diving until these symptoms are resolved.
---Gas bubbles in the eye
Gas bubbles are occasionally placed in the eye to stent the retina against the retinal pigment epithelium after repair of retinal detachments. This is an absolute contraindication to both diving and hyperbaric chamber exposures. Diving with a gas bubble may cause pain on descent due to compression of the globe as the gas phase is compressed. Extra gas diffuses into the bubble and the absolute pressure is reduced, the bubble to grows and intraocular pressure rises.
Considerations in Fitness to Dive Evaluations
Guidelines have been published on medical standards for divers which include considerations concerning the eye. Visual considerations differ extensively according to whether the diving is to be recreational or occupational.
Fitness to dive evaluations are most often done in one of two settings; either recreational and occupational. The first evaluation requires a decision based entirely on medical safety considerations for the patient.
A dive evaluation done in an occupational setting in which a patient who is currently or hopes to be a military or commercial diver is evaluated by a physician who works for the organization in question, with interests of both the organization and the prospective employee. Economic, medico legal and liability considerations effect considerations in decisions about diving fitness in the occupation setting.
The fitness to dive considerations for sport divers should focus only on medical safety and attempt to address three issues:
(1) Does the condition impair the individual in such a way as to endanger himself or his associates in the hazardous hyperbaric environment (e.g. inadequate visual acuity);
(2) Is the condition one which may be made worse by hyperbaric exposures (e.g. Neurological residua from DCS);
(3) Would hyperbaric exposures possibly result in complications from a pre-existing condition (e.g. vision threatening barotrauma from diving with intraocular gas).
Contra-indications to Diving from Eye Problems
Post-operative gas in the eye
Diving should not be allowed early in the post-operative period because of the possibility of gas having been inserted purposefully or inadvertently. Boyle's Law dictates that the air will change in volume inversely in proportion to the depth and the possibility of injury to the eye would be great.
Hollow orbital implant
The implant would implode at depth, severely injuring the orbit and endangering the diver.
Any acute disorder
Pain, double vision or decrease in visual acuity would interfere with the problem solving and decision making process of the diver.
Recent eye surgery within the convalescent period.
Visual problems from previous DCS or AGE.
there is loss of vision severe enough as to make it dangerous for
them to function in an underwater environment.
Divers who have undergone recent glaucoma filtering surgery. A minimum of two months convalescence is recommended after this procedure. Functioning filters are a relative contraindication to diving. There are two basic types of glaucoma filtering surgery. In one type, a fluid drainage hole is created in the eye wall, and in the other type, a plastic drainage device is implanted through the eye wall. After both types of surgery, fluid from the eye drains out of the eye into a pocket behind the eyelids and is absorbed into the blood stream. This lowers the pressure inside the eye so that the damage from glaucoma can be stopped.
Underwater Refractive Correction
If contact lenses are to be used for diving, soft contact lenses are preferred. Hard (polymethylmethacrylate) contact lenses have been associated with nitrogen bubbles in the precorneal tear film during decompression and after dives, resulting in swelling of the cornea.
Although the increased gaseous diffusion properties of rigid gas-permeable contact lenses theoretically decrease the chance of bubble formation in the tear film, use of these lenses while diving has been demonstrated to cause bubble formation under the lens, leading to secondary corneal epithelial disruption. Symptoms resolve upon removal of the lens at the surface.
Corneal edema was not observed in one series in which soft contact lenses were studied.The most frequent complication of soft contact lens use in diving is loss of the lens. Lens loss can be minimized by ensuring a good seal on the face mask and minimizing the amount of water that gets into the air space of the mask. Should the mask become displaced during the dive, narrowing of the palpebral fissures helps decrease the chance of the contact lens floating off the surface of the eye.
A prescription ground face mask is another refractive alternative, as is a face mask with a lens bonded onto the surface of the mask. Masks and lenses may be lost in high swells or rough surf, however, leaving a diver without refractive correction.
Refractive corrections for presbyopia [far sightedness from age] presents special challenges underwater. Presbyopic contact lens-corrected myopes may require greater adds underwater than when viewing the same objects in air because of the increased percentage of shorter-wave length light rays underwater. Presbyopes should consider monovision correction to facilitate underwater visual tasks.
Refractive Surgery and Diving
Laser refractive surgery is a safe and effective means of correcting refractive errors in divers. Photorefractive keratectomy has been allowed in U.S. Navy divers since 1996. Laser-in-situ keratomileusis (LASIK) is presently a more commonly done procedure. Although this procedure presents the potential for both inflammation and trauma under the corneal flap as well as traumatic dislocation of the flap, these conditions have not to date been reported as complications of diving. Visual acuity appears to be maintained in the hyperbaric environment. Acute hyperbaric stress does not appear to significantly alter refractive power after corneal surgery.
Diving After Eye Surgery
Individuals who have undergone ophthalmic surgical procedures should allow an appropriate period for wound healing before resuming diving.
Factors increasing the risk of post-operative complications:
Marine organisms may cause infections when they contaminate non-epithelialized wound surfaces of the cornea, sclera, conjunctiva, or lid tissues
These pathogens may enter the eye through unhealed corneal or scleral wounds and result in vision threatening endophthalmitis
The risk of infection due to contact of the eye with water is much greater when diving in potentially contaminated ocean, river, or lake water than when showering or bathing in chlorinated city water.
Gas in the anterior chamber or vitreous cavity.
This may be affected by changes in pressure and result in vision threatening intraocular barotrauma
Negative pressure in the air space of a face mask caused by a mask squeeze.
This may result in subconjunctival hemorrhage, lid bruising and swelling, and could theoretically cause the rupture of incompletely healed corneal or scleral wounds.
In chamber dives, only gas in the eye remains a consideration.
There are no controlled studies specifically addressing the requisite length of convalescence before a return to diving. The recommendations below are based on the application of wound healing observations in other studies and on clinical experience.
Diving after refractive surgery
There are often inquiries about radial keratotomy [RK], a surgical procedure with long-term implications for diving. RK is currently a widely performed keratorefractive procedure. Individuals whose myopia has been corrected with this procedure are prohibited from entering diving programs in the Navy.
Applicants who have had this procedure may not even be allowed to serve in less visually demanding Navy positions. Two recent reviews of RK in the military have recommended that the procedure continue to be disqualifying for Navy divers and for Army aviators. Edmonds, Lowery and Pennefather recommend that no one who has had RK be allowed to dive unless they have face masks designed to equalize the pressure within the mask to that of the ambient pressure. Davis and Bove state that until further data is available, a person who has had RK should be permanently disqualified from diving.
Complications of RK that impact the diver.
diurnal fluctuations in visual acuity
decrease in best corrected visual acuity
recurrent corneal erosions
increased susceptibility to traumatic corneal rupture
possible barotrauma induced rupture of RK incisions in the hyperbaric environment (No reports)
Dr. Frank Butler has seen only one clinically significant case of face mask squeeze in many years of association with Navy and sport diving activities. Most of the reports of corneal rupture following RK have been the result of direct blunt trauma to the eye. Also worthy of note are the reports of blunt trauma severe enough to cause hyphema and facial fractures in which radial keratotomy scars remained intact.
Sport divers who have had radial and astigmatic keratotomy that does not entail full thickness corneal incisions or prolonged topical steroid therapy, may be allowed to dive after three months.
Photorefractive keratectomy (PRK) is a new refractive surgical procedure. Unlike radial keratotomy, it entails no corneal incisions which may decrease the ability of the cornea to withstand blunt trauma. Published studies of the outcomes of PRK have shown this procedure to be relatively free of post-operative complications when compared to RK. Individuals who have had this procedure may be allowed to dive two weeks after their surgery, assuming that they have had a normal post-operative course with resolution of pain and photophobia.
LASIK (laser in situ keratomileusis)
1. There are no case reports that document diving related complications after LASIK.
2. There are at least three potential complications that might occur in post-op LASIK patients as a result of diving:
- Globe rupture from face mask barotrauma (unlikely)
- Interface keratitis (infection of the flap interface)
- Flap displacement from interface bubbles
3. Complications that might impact the safety of divers include;
Night diving complaints
These decrease from 25+% early to about 4% in one year.
4. It is recommended waiting a minimum of one month before resuming diving after LASIK. [Butler]
5. This should always be discussed with the personal ophthalmologist, so that he or she will be able to add any special knowledge about your specific situation that would be relevant.
In corneal surgery with full thickness incisions very little healing is noted in the first week, followed by a rapid rise to about 30% of normal strength at 1 month. Wound strength then gradually increases to approximately 50% of normal by 3 to 6 months. Penetrating keratoplasty in which full thickness incisions are made in the cornea should be followed by a six month convalescent period.
For cataract surgery, the post operative waiting period varies with the type of incision used. There should be a 3 months wait if a non-corneal valve incision is used: if a corneal valve incision is used, the clear corneal type requires a 2 month wait and the scleral tunnel needs only a one month waiting period.
Glaucoma filtering surgery (relative contra-indication) requires about a two month wait before diving.
Pterygium excision and conjunctival surgery require two weeks of convalescence and there should be a one week wait after corneal suture removal.
Argon laser trabeculoplasty or iridectomy and Yag laser capsulotomy necessitate no wait.
With vitreoretinal surgery, such as vitrectomy, retinal detachment repair and pneumatic retinopexy, there must be a two month waiting period before diving with assurances that all air or gas has been absorbed. A two week wait would be sufficient for retinal cryopexy or laser photocoagulation for breaks.
For oculoplastic surgery, skin grafts and strabismus surgery, a two week wait is recommended, with the caveat that there must be complete epitheliazation of skin grafts and that there is no air filled prosthesis.
Ocular and Periocular Barotrauma
The eye is normally filled with noncompressible fluid and solid tissues and is therefore protected from barotrauma. However, once a mask is placed over the face, a different circumstance exists. The face mask is an air-filled space bounded on one side by the eyes and ocular adnexa. As a diver descends, if he or she does not expel gas through the nose into the airspace of the face mask, a relative negative pressure develops in this space. If this negative pressure becomes great enough, the eyes and ocular adnexa are drawn towards the space. Marked lid edema with ecchymosis and subconjunctival hemorrhage may develop as tissues and blood vessels are disrupted by this distention. These signs may be alarming to the diver but typically resolve without sequelae. In a more severe case, such as that which may occur when an unconscious diver sinks a significant distance in the water column, more serious injury, including hyphema, may occur.
Barotrauma is also possible in persons with gas bubbles in the anterior chamber or vitreous cavity. Pressure-induced changes in the volume of this bubble may result in retinal, uveal, or vitreous hemorrhage, as well as partial collapse of the globe. Permanent loss of vision may ensue. Persons with intraocular gas should not be allowed to dive as long as the bubble remains in the eye. The necessity of adding extra gas to the face mask during descent makes it obvious that swim goggles, which cover only the eyes and not the nose, should never be used for diving.
Facemask barotraumas may also result in damage to the periocular tissues. There are reports of numbness and paresthesias in the distribution of the infraorbital nerve that resulted from maxillary sinus barotrauma and diplopia with orbital hemorrhage.
of the Eye
Normally, the eye is protected from barotrauma because the eye is filled with non compressible fluids, the aqueous [in front of the lens] and vitreous [behind the lens] humors.
A mask has air filled space that is compressible, affecting the eye and surrounding tissues.
If the diver does not expel gas through the nose into the mask on descent, negative pressure develops inside this space, sucking the eyes and lids toward this space.
This negative pressure results in marked lid edema and bruising as well as bleeding under the conjunctivae of the eyeballs. These changes look a lot worse than they really are but can be disconcerting to the diver and his buddy.
Hyphema [marked swelling with bleeding], a more serious injury, can occur in the eyes if the diver becomes unconscious and sinks to a greater depth without being able to equalize the mask. This can also result in bleeding under the periosteum of the bones of the orbit.
Vitreoretinal surgery with air placed in the eye contraindicates diving so long as any of the bubble remains. Pressure induced changes in the volume of these bubbles may result in hemorrhage inside the eye and also may result in partial collapse of the eyeball.
Ocular involvement in decompression sickness (DCS) are infrequently reported in the ophthalmic literature, but there are a number of reports of ocular involvement with DCS in the diving medical literature. Reported manifestations include eye flicking, double vision, visual field defects, blind spots, half visual field blindness, muscle pain, cortical blindness, crossed eyes, inflammed optic nerve, and central retinal artery occlusion. The incidence of visual symptoms in patients with DCS was found to be 7% in one large series.
DCS is treated with oxygen breathing and recompression on an emergent basis. Ophthalmologists seldom encounter this disease in an acute setting because most divers know to seek recompression therapy for signs or symptoms of DCS. Since treatment generally results in resolution of all symptoms, most persons with visual symptoms before treatment are asymptomatic after recompression treatment and are therefore not referred to ophthalmologists.
Incomplete response to treatment or recurrence of symptoms after treatment may bring a victim with ocular DCS to the ophthalmologist on a less emergent basis. The victim should be managed in conjunction with a diving medicine specialist. Recompression therapy and hyperbaric oxygen should be administered even when a significant delay has occurred between the onset of symptoms and initial evaluation of the victim, since treatment may be effective despite delays of up to several weeks.
Ocular Fundus Lesions in Divers
Fluorescein angiography of divers has documented changes that were attributed to decompression-induced intravascular gaseous microemboli. The incidence of these lesions was related to the duration of diving and a history of DCS. Other abnormalities noted more frequently in divers were low retinal capillary density at the fovea [blind spot], microaneurysms [small dilations], and small areas of capillary non-perfusion. Studies show that adherence to safe diving practice confers some protection against the macular abnormalities known to occur in divers with a history of DCS.
Arterial Gas Embolism
Blockage of larger arteries to the eye with blindness is found with arterial gas embolism. Management is similar to that for DCS, with emergent recompression and hyperbaric oxygen therapy indicated in all cases.
Hyperoxic Myopia [nearsightedness]
Individuals who undergo prolonged exposures to hyperoxic gas mixtures may experience lens changes from oxygen toxicity that is manifest initially by nearsightedness. This myopic shift is progressive and is usually reversible if the hyperoxic exposures are discontinued. Although this condition is most common in patients undergoing repeated hyperbaric oxygen exposures in a chamber for medical conditions, it has also been reported in a SCUBA diver doing a series of prolonged dives using a gas mix with a constant partial pressure of oxygen of 1.3ata. And occurs in caisson workers.
The Effect of Oxygen Toxicity on the Eye
Manifestations of Oxygen Toxicity
Eyelid twitching is the most commonly seen manifestation of O2 toxicity and usually is a warning that a full-blown seizure is imminent. In addition, there can be blurred vision, visual field constriction, visual hallucinations, transient one-sided loss of vision. All of these are reversible after termination of the O2 exposure.
Treatment is removal of the O2 source immediately. No residua occur unless secondary trauma or near-drowning occur from a convulsion. Oxygen toxicity can be prevented by using appropriate O2 concentrations at proper depths.
Ocular jellyfish stings
Divers and swimmers may occasionally be stung by jellyfish on and around the eyes. Signs and symptoms are painful but typically self-limited, usually resolving within 24-48 hours. There are reports of unusually severe and prolonged eye eye problems and elevation of intraocular pressure, with glaucoma and persistent inflammation. All patients with ocular jellyfish stings that do not resolve with 24-48 hours should be seen urgently by an ophthalmologist.
Decreased Vision after Diving
A frequent complaint is of diminished vision after diving. DCS and arterial gas embolism should be considered whenever vision is acutely decreased after diving because of the possible emergent need for recompression therapy, especially if any other manifestation of DCS or arterial gas embolism are present.
Other disorders may also affect vision after a dive. Corneal edema resulting from the formation of gas bubbles under polymethylmethacrylate and rigid gas-permeable contact lenses may cause decreased vision. A soft contact lens wearer who complains of blurred vision after a dive may have a lost or displaced lens.
Recurrent mild ocular irritation and blurring of vision can occur after dives on which soft contact lenses were worn. The lenses have been noted to be tightly adherent to the cornea, probably as a result of a decrease in water content in the lens after contact with hypertonic sea water. Symptoms are relieved with a few drops of isotonic artificial tears. Decreased movement of soft contact lenses on the cornea has been reported to occur from exposure to swimming pool water as well.
Another possible cause of nondysbaric decreased vision after a dive is inflammation induced by chemical agents used to reduce face mask fogging. Improper use of commercial antifog agents chemicals can result in blurred vision, sensitivity to light, tearing, and spasm of the eyelids that may not develop until several hours after the dive.
Divers sometimes use a transdermal scopolamine patch (placed behind the ear) to prevent motion sickness. This may result in dilated pupils, decreased accommodation, and blurred vision. Hyperoxic myopia may be a possible etiology for the vision loss if the diver has had recurrent or prolonged exposures to elevated partial pressures of oxygen. Divers often use oxymetazoline nasal spray to assist in equalizing the pressure in their ears. The vasoconstriction caused by this medication has been reported to cause temporary vision loss.
Migraine-like phenomena have been reported after hyperbaric exposures. Flashing blind spots have been noted shortly after surfacing with no other manifestations of decompressions sickness. These events may represent only a migraine event temporally associated with diving or they may be an atypical manifestation of decompression sickness.
Finally, the loss of vision may be caused by ocular disorders that occurred during or shortly after the dive, but were not a direct result of the dive itself.
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