The College of Optometrists

does someone who has an early pit tumour show a field plot with superior temporal hemianopia first, due to the way the inferior nasal fibres cross or is it also to do with pre and post fixed chiasm?

The nasal fibres that dissociate are split into the anterior knee of willbrand (containing the inferior peripheral nerve fibres) and posterior knee of willbrand (superior nasal fibres). In most Px the chiasma is directly above the pit gland and when it grows it presses on the anterior nasal fibres first in the majority of cases.

If it is pre fixed it is thought this will lead to pressure on the posterior part of chiasma and to bitemporal scotoma first.

Post fixed i would think leads to superior temp field loss again but not too sure.

It all depends on the way the tumour is growing too so you don't get a fixed picture all the time. Just refer any sudden field losses in both eyes as a matter of urgency. I think that is safe enough.

Pituitary tumour may be very slow growing and the bitemporal changes can be very subtle initially, remember there may well be systemic symptoms because of the hormonal changes induced by pituitary abnormality.

thank you