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In message <01BCC91D.22266F30@DB*>, Carlos Accioly
<carlos@me*.co*.br*> writes
>Esat Atikkan said:
>
>>I for one would B very interested in the info U gathered RE: Glaucoma &
>>diving.
>>
>>Maybe U can provide the results, if not 2 much of a bother.
>
>....and Dave Walton said:
>
>It would be great if you summarized the information you got and posted
>on a newsgroup somewhere, so that in the future, search engines will be
>able to direct interested people to it. Be sure to include references
>and phone numbers too...
>
Folks
There is literature out there, despite all reports to the contrary and I
am surprised that all you good people don't know about it. I am putting
here an article I wrote for our medical committee on eyes and diving,
gleaning information from several sources, but one source in particular
which is quoted at the end. Here is the article in plain text, so you
don't all say "But I don't have Word..." :-). Therefore, apologies for
the formatting.
GENERAL MEDICAL STANDARD 19
DIVING AND OPHTHALMOLOGICAL PROBLEMS
Underwater Refractive Correction
The two choices that can be made are contact lenses and prescription
face masks. If contact lenses are to be worn, soft contact lenses are
to be preferred. Hard contact lenses have been shown to cause corneal
oedema during decompression and after dives [1-4]. These changes are
caused by the formation of nitrogen bubbles in the precorneal tear film
which interfere with normal tear film physiology and result in
eptihelial oedema. With soft contact lenses which do not appear to
cause corneal oedema [1,5], the most frequent complication is loss of
the lens, which can be minimized by making sure that the mask fits well.
This problem may be ameliorated to a certain extent by using the
disposable "one day" soft lenses and carrying an extra pair of lenses on
board the boat or in the diving kit bag.
Prescription face mask lenses provide the other alternative.
These can be expensive, especially if the wearer has a degree of
astigmatism. A face mask with corrective lenses bonded onto the face
plate of the mask is also a possiblility, but may present problems with
eventual erosion of, or bubble formation in the bonding substance used.
Ocular Barotrauma
Unless the diver expels gas through the nose into the face mask on
descent, a relative negative pressure develops in the air space between
the face plate and the face. Marked lid oedema and ecchymosis together
with subconjunctival haemorrhage may result. The effects can be
disconcerting, but usually resolve without sequelae. Overpressure is
generally not a problem as the air escapes around the face mask seal.
Barotrauma may also occur in patients who dive with intraocular
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 haemorrhage, as well as partial collapse of the
globe. Diving with any trace of an intraocular gas bubble is therefore
contraindicated.
Ophthalmic Decompression Illness
It is worth remembering that the first observations of decompression
illness were made by Robert Boyle in 1670 when he observed gas bubbles
in the anterior chamber of the eye of a viper which had been
experimentally exposed to decreased pressure [6]. Although
ophthalmological manifestations of DCI are fairly rare, they may include
nystagmus, diplopia, visual field defects, scotomas, and homonymous
hemianopias. Fluorescein angiography studies of divers have documented
retinal pigment epithelial abnormalities indistinguishable from those
seen in eyes with choroidal ischaemia. These changes have been
attributed to decompression-induced intravascular gaseous microemboli
[7]. The incidence of these lesions was directly related to the length
of diving and a history of DCI. No divers suffered a loss of visual
acuity from these abnormalities, but the paper notes that the long-term
effects of this phenomenon remain to be studied.
Retrochiasmal defects such as hemianopia or cortical blindness
are potential ocular manifestations of DCI caused by arterial gas
embolism, the commonest cause of which is pulmonary barotrauma.
Treatment of DCI is by prompt recompression.
Decreased Vision After Diving
The following causes should be considered:
* DCI
* Corneal oedema (hard lens users)
* Loss of a lens (soft lens users)
* Antifog keratopathy (resulting from the volatile compounds used in
mask antifogging preparations)
* Ultraviolet keratitis
* Contact lens adherence syndrome (contact with sea water can cause soft
lenses to become tightly adherent to the cornea).
Diving After Eye Surgery
Diving after eye surgery can only be carried out after a suitable time
for the wound to heal. A number of factors will increase the risk of
post-operative complications:
* The water in which diving is performed may harbour pathogens which can
infect non-epithelialised surfaces.
* Such pathogens may enter the eye through non-healed wounds and result
in vision-threatening endophthalmitis.
* Gas in the eye resulting from surgery can be affected by changes in
pressure and this can give rise to vision-threatening intraocular
barotrauma.
* Face mask barotrauma may result in subconjunctival haemorrhage and
might cause rupture of incompletely healed wounds.
Unfortunately, there are as yet no controlled studies on the length of
time a subject should not dive after different forms of ophthalmic
surgery. Therefore the following comments are based on current "best
practice".
Corneal surgery: Studies on the rate of full thickness corneal
scar healing show little healing in the first week, followed by a rise
to approximately 50% of normal by 3-6 months. Procedures such as
penetrating keratoplasty should be followed by a lay-off period of 6
months before being allowed to return to diving. Patients who have
undergone radial and astigmatic keratotomy which do not involve
prolonged steroid therapy, may be allowed to dive after a 3 month rest
period. Photorefractive keratotomy in which there are no incisions may
allow a return to diving as soon as re-epithelialisation of the cornea
is complete and the acute post-operative symptoms subside.
Cataract surgery: A three month wait before resuming diving will
generally be sufficient after extracapsular cataract surgery. Scleral
tunnel incisions as used in phacoemulsification procedures will require
a period of one month off diving to allow for healing to take place.
Glaucoma
Glaucoma may be treated either medically or surgically to reduce the
intraocular pressure. Therefore, there may be concern when it is
realised that diving may raise the intraocular pressure to very high
levels. However, saturation divers working at depths of 250 metres have
intraocular pressures in excess of 19,000 mmHg without suffering from
symptoms of glaucomatous optic neuropathy. Thus, it appears to be the
magnitude of the difference between the extraocular and intraocular
pressures that is important and during diving this difference should be
very low.
There are two possible complications that may arise in patients that
undertake diving after glaucoma filtering surgery. These are a).
subconjunctival haemorrhage due to face mask squeeze and chemosis that
may compromise the operation of the filter and b). late endophthalmitis
as a result of pathogens gaining access to the anterior chamber through
the conjunctiva. In practice, neither of these complications has been
reported as a complication of diving. A two month lay-off period is
advised after this form of surgery and patients should be advised to
avoid face mask barotrauma.
Further Reading
Butler FK. "Diving and hyperbaric ophthalmology" Surv.Ophthalmol.
39(1995)347-66.
References
Cotter J. "Soft contact lens testing on fresh water SCUBA divers"
Contact Lens 7(1981)323-6.
Josephson JE, Caffery BE. "Contact lens considerations in surface and
subsurface aqueous environments" Optom.Vis.Sci. 68(1991)2-11.
Socks JF, Molinari JF, Rowley JL. "Rigid gas permeable contact lenses in
hyperbaric environments" Am.J.Opt.Phys.Optics 65(1988)942-5.
Edmonds C, Lowry C, Pennefather J. "Diving and subaquatic medicine"
Oxford, Butterworth-Heinemann 1992 3rd ed. Chap. 30, p408.
Simon DR, Bradley ME "Adverse effects of contact lens wear during
decompression" JAMA 244(1980)1213-4.
Boyle R. "A digressive experiment concerning the expansion of bloud and
other animal juyces" Phil.Trans.Roy.Soc.Lond. 63(1670)2033-44.
Polkinghorne PJ, Cross MR, Sehmi K et al. "Ocular fundus lesions in
divers" Lancet (1988)1381-3.
Rashid ER, Waring GO. "Complications of radial and transverse
keratotomy" Surv.Ophthalmol. 34(1989)73-106.
If you're really interested in the subject, you must read the Surveys in
Ophthalmology article, 'cos it's really good. For those of you without
any access to articles of this kind, I might be persuaded to send you a
copy of it - I never said this of course, due to the copyright
restrictions.
Good vision to you all...
Chris.
--
Dr. Chris. Edge
--
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