David Glasser
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Hi all -
I'm an ophthalmologist who has been asked about eye pressure at depth. It's been too many years for me to rely on my recall of the details from college physics, so I thought I would post here and ask the experts.
At sea level the normal intraocular pressure (IOP) ranges from about 10-20 mm Hg, let's say 15 mm Hg, higher than ambient atmospheric pressure. At depth, I assume that the pressure inside the eye does not increase, since, like the rest of the body structures that contain no gas, the eye is not compressible. Do I have this right so far?
If the above is correct, for someone who has had eye surgery, where a full-thickness incision into the eye has healed but never gains the full strength of the unoperated eye wall, I would also assume that there is no risk of incision rupture due to pressure changes.
However, as a diver descends, doesn't the air in the mask compress, leading to an increase in the differential between the pressure inside the eye and the air pressure inside the mask? I understand that divers equalize this pressure by adding air to the mask as they descend. Has anyone ever looked at how close to "normal" this equalization is? Could it be off by 10, 20, 30 mm Hg or more?
If the pressure differential between the inside of the mask and the eye is high enough, I imagine it might risk rupturing an incision. Or even in divers with no history of eye surgery, could it cause gradual damage to the pressure-sensitive optic nerve, as in glaucoma, if the differential is maintained for hours at a time? Do professional divers stay down that long? I am not aware of any increased risk of glaucoma-like damage in divers, at least in the medical literature, but I only found one reference with a PubMed search (below). It didn't address this directly, and raised yet another question: why would angles narrow further, risking precipitation of an acute narrow angle glaucoma attack, during ascent?
Appreciate it if any of you are able to educate me further.
Thanks,
David Glasser
Klin Monatsbl Augenheilkd. 1976 Feb;168(02):253-7.
[Intraocular pressure in snorkling and diving (author's transl)][Article in German]
Kalthoff H, John S.
The reactions of the intraocular pressure (i.o.p) in snorkling and scuba diving were studies on 29 healthy subjects. A patient with chronic glaucoma simplex was examined in a pressure tank. The results confirm the author's opinion, that a well compensated chronic glaucoma simplex with intact discs and fields does not exclude fitness to dive. However, a diver with narrow angel glaucoma risks sudden rise in i.o.p. and acute glaucoma while ascending to the surface. Persons, who are examined for fitness to dive, should be seen by an ophthalmologist, if they have a glaucoma or if they are hypermetropic and over 40 years of age.
PMID: 957553 [PubMed - indexed for MEDLINE]
I'm an ophthalmologist who has been asked about eye pressure at depth. It's been too many years for me to rely on my recall of the details from college physics, so I thought I would post here and ask the experts.
At sea level the normal intraocular pressure (IOP) ranges from about 10-20 mm Hg, let's say 15 mm Hg, higher than ambient atmospheric pressure. At depth, I assume that the pressure inside the eye does not increase, since, like the rest of the body structures that contain no gas, the eye is not compressible. Do I have this right so far?
If the above is correct, for someone who has had eye surgery, where a full-thickness incision into the eye has healed but never gains the full strength of the unoperated eye wall, I would also assume that there is no risk of incision rupture due to pressure changes.
However, as a diver descends, doesn't the air in the mask compress, leading to an increase in the differential between the pressure inside the eye and the air pressure inside the mask? I understand that divers equalize this pressure by adding air to the mask as they descend. Has anyone ever looked at how close to "normal" this equalization is? Could it be off by 10, 20, 30 mm Hg or more?
If the pressure differential between the inside of the mask and the eye is high enough, I imagine it might risk rupturing an incision. Or even in divers with no history of eye surgery, could it cause gradual damage to the pressure-sensitive optic nerve, as in glaucoma, if the differential is maintained for hours at a time? Do professional divers stay down that long? I am not aware of any increased risk of glaucoma-like damage in divers, at least in the medical literature, but I only found one reference with a PubMed search (below). It didn't address this directly, and raised yet another question: why would angles narrow further, risking precipitation of an acute narrow angle glaucoma attack, during ascent?
Appreciate it if any of you are able to educate me further.
Thanks,
David Glasser
Klin Monatsbl Augenheilkd. 1976 Feb;168(02):253-7.
[Intraocular pressure in snorkling and diving (author's transl)][Article in German]
Kalthoff H, John S.
The reactions of the intraocular pressure (i.o.p) in snorkling and scuba diving were studies on 29 healthy subjects. A patient with chronic glaucoma simplex was examined in a pressure tank. The results confirm the author's opinion, that a well compensated chronic glaucoma simplex with intact discs and fields does not exclude fitness to dive. However, a diver with narrow angel glaucoma risks sudden rise in i.o.p. and acute glaucoma while ascending to the surface. Persons, who are examined for fitness to dive, should be seen by an ophthalmologist, if they have a glaucoma or if they are hypermetropic and over 40 years of age.
PMID: 957553 [PubMed - indexed for MEDLINE]