Understanding Neurology

Neurological investigations 59investigated by combined pituitary functionstimulation tests comprising the insulin tolerance test,also with gonadotrophin releasing hormone (GnRH)and thyrotrophin releasing hormone (TRH) injection.66DISEASE AT ‘SHARED’ SITESOrbitOrbital disorders may present to the neurologist aswell as to the ophthalmologist, and it important thatneurologists are aware of the appropriateinvestigations for this area.Methods of visual field testingIt must be remembered that confrontation using a redpin is a relatively crude means of mapping visualfields, both for peripheral vision and for assessing theblind spot. Peripheral visual fields are better testedwith a Goldmann perimeter (67). Here, a movingtarget is brought in from the periphery, and thepatient must indicate as soon as he is aware of thetarget. It is thus possible to map out peripheral visualfields well.While central fields may be assessed using aGoldmann perimeter, this is more accurately doneusing the Humphrey field analyser, which records thethreshold at which a static light source is seen atvarious central points.66 Magnetic resonance image of a pituitary tumour (arrow).Fixationpoint67Peripheral120 105 90 75 6070field1354560501504030 Central field16530201510180 90 80 70 60 50 40 30 20 10 10 20 30 40 50 60 70 80 90 01020195345Blind spot3021040503302256070315240 255 270 285 300 Right eye67 Diagram to demonstrate Goldmann perimetry.Goldmann perimeter