A 68-year-old man was referred by his optometrist to HES with suspected LTG due to repeatedly irregular visual field test results, advanced optic disc cupping, normal intraocular pressures (IOPs) and a family history of glaucoma.
The patient subjectively felt that vision in his ‘good’ left eye (LE), which normally had a visual acuity of 6/6 N5, started to deteriorate 6 months earlier; at the point of referral it was best corrected to 6/7.5 N6.
His right eye (RE) was known to be amblyopic with a visual acuity of 6/18 N12.
His medical history included considerable risk factors for systemic vasculopathy, such as hypertension, hypercholesterolaemia, 50 pack-years of smoking and type 2 diabetes with no diabetic retinopathy.
Despite detailed questioning, he denied any new systemic symptoms apart from experiencing increased lethargy.
Clinical examination at HES revealed advanced bilateral cupped optic discs with a cup-to-disc ratio right 0.9 (90%) and left 0.8 (80%; figure 1).
Furthermore, the findings from the referring optometrist of equal and reactive pupils, normal eye movements and IOPs in mid-teens were confirmed.
Computerised perimetry showed constricted visual fields in both eyes, albeit with considerably raised false-negative error rates in excess of 30% (figure 2A).
Since this can be a result of poor concentration and attention span with testing compounded, especially with an amblyopic RE, the field test was repeated 4 weeks later with similar results (figure 2B).
At this visit, the patient experienced further deterioration of his ‘good’ LE.
Visual acuities measured 6/24 (loss of one Snellen line) N36 in his amblyopic RE, and 6/18 (loss of two Snellen lines) N36 in his LE, which now also showed depressed colour vision.
An urgent scan of the patient's head and orbit was requested to rule out a compressive lesion and blood analysis was carried out to screen for other causes of optic neuropathy including vitamin B12, folate levels and inflammatory markers.
MRI revealed a large mass centred at the pituitary fossa measuring approximately 4.5 cm×5.1 cm× 4.8 cm (figure 3A–C) extending into the suprasellar cistern and infrasellar sphenoid sinuses.
The optic chiasm and both optic nerves were displaced superiorly and compressed on both sides.
The mass showed heterogeneous T1 and T2 signals with multiple fluid levels most likely due to previous haemorrhage and low-signal components suggesting calcifications.
The appearance was probably due to a craniopharyngioma or haemorrhagic pituitary adenoma.
The patient was referred urgently to the neurosurgery unit and was found to have markedly raised prolactin levels of greater than 200 000 mIU/L, confirming the diagnosis of a giant prolactinoma.
In cooperation with the local endocrinology service, he was started on cabergoline 500 µg and dexamethasone 8 mg.
Within a week this led to a dramatic improvement of the patient's visual fields and acuities to 6/18 RE and to 6/9 LE.
His prolactin levels showed a similar dramatic response with levels coming down to 336 mIU/L.
Three months later his visual acuity in his RE and LE were 6/18 and 6/5, respectively, and visual field examination showed striking recovery with almost normal results (figure 2C).