Mask squeeze

An experienced recreational diver conducted a dive to a depth of 30 m in a Swiss lake within the no-decompression limit. During the ascent, he suddenly noticed impaired vision in his right eye. After surfacing, his vision was blurred and foggy in both eyes, whereupon he was given oxygen due to suspicion of a diving accident. After just ten minutes, his vision was completely restored. The diver reported having experienced similar problems with his right eye during previous dives. His mask was “completely watertight.”

Subconjunctival hemorrhages and fluid under the conjunctiva

The clinical picture corresponds to mask barotrauma (mask squeeze). This is caused by negative pressure in the diving mask when insufficient pressure equalization occurs during descent. In order to equalize pressure, the mask must have a nose bridge that allows the diver to blow air into the mask through the nose. If this is not possible, the negative pressure in the mask creates suction on the eyes and surrounding structures. Therefore, a correctly fitting mask with easy access to the nose is essential to reliably prevent mask barotrauma.

Typical in the image shown are subconjunctival hemorrhages – bleeding under the conjunctiva – caused by the negative pressure created in the mask during descent if pressure equalization is insufficient. As a result of this suction, fine vessels in the conjunctiva can tear. In addition, pronounced fluid accumulation under the conjunctiva is noticeable, which impressively reflects the extent of the negative pressure.

But why did the diver's vision deteriorate? The conjunctiva itself is not responsible for vision. However, its dysfunction can lead to impaired wetting of the cornea due to disturbed tear flow. Pale areas above the iris and extending to the pupil are visible, indicating acute dehydration of the cornea. This temporary lubrication disorder explains the blurred vision at the end of the dive and shortly after surfacing. As soon as the tear film normalizes, vision clears up again. The bleeding is impressive, but has no consequences and disappears on its own within a few days.

The administration of oxygen had no direct influence on the mask barotrauma, but was absolutely justified in the context of a suspected diving accident. The actual therapy consisted of removing the mask and equalizing the negative pressure.

The fact that the diver uses a completely watertight mask and repeatedly reports problems with his right eye indicates that pressure equalization has already failed several times. He should therefore critically check the fit of his mask and ensure that pressure equalization is reliably guaranteed during every dive.

I would like to thank Dr. Eva Grams for her ophthalmological review.