Welcome to question of the day #349

Eyetool question of the day #349

I work with a lot of older people and am worried that I might miss the presence of glaucoma because my older patients are unable to undergo a visual field test. Do you have any tips?

I won’t go into increased and/or high cup-to-disc ratios, optic disc margin haemorrhages, or deep cups here. What I want to concentrate on are three signs involving optic nerve blood vessels that I find useful in helping me decide if a patient is a glaucoma suspect especially if they are unable to perform visual field testing.

The first of these is referred to as bayonetting. This is a sign that neuro-retinal rim material has been destroyed by the glaucoma process. This is like a rope being hung over the edge of a sharp vertical cliff face. If the cliff face behind the rope is eroded then when viewed from a helicopter the rope on the ground above the cliff face will be visible as will the rope at the base of the cliff but the length in between will be displaced into the excavation and not be visible anyone in the helicopter. The rope visible at the bottom will be laterally displaced compared to the rope at the top. This displacement causes a bayonet appearance like a bayonet on an old rifle. In the eye, the rope is a blood vessel and the neural retinal rim is the cliff face.

The next is baring of blood vessels. Again, caused by erosion of the neural retinal rim. These are originally curved blood vessels that lie on top of superior and inferior neural retinal rim tissue. As the glaucoma process advances and superior and/or inferior nerves beneath the blood vessel are destroyed the blood vessel is left ‘airborne’. This is often termed a ‘bare’ blood vessel.

Thirdly, other vessels that seem to ‘hang in space’ when a lot of neural retinal rim tissue has been destroyed are called fly-over vessels as they fly over empty space.

I recently referred two patients as suspect primary open-angle glaucoma cases. The first was a lady 100 years old who had had regular eye examinations elsewhere but when I saw her, she had a cup-to-disc ratio of 0.9 in each eye. Her eye pressures were 12 and 13. The other patient was 72 years old and also had had regular eye examinations elsewhere and had cup-to-disc ratios of 0.6 but with a flyover blood vessel in her right eye. Her eye pressures were 23 and 22.