Feature, Soapbox

The world of neuro-ophthalmology

Neuro-ophthalmology (N/O) is an interesting subspecialty because it crosses boundaries. Almost exclusively a ‘medical–type’ specialty rather than ‘surgical’, about half of its practitioners in Australia and New Zealand are neurologists and the other half are ophthalmologists.

In fact, the only surgical procedure that is regarded as principally in our domain is optic nerve sheath fenestration: creating a hopefully permanent drain of cerebrospinal fluid from within the optic nerve sheath and thus protect the optic nerve from progressive ganglion cell and nerve fibre loss in chronic papilloedema (much like a trabeculectomy that drains aqueous from the anterior chamber).

Most ophthalmic members of the Neuro-Ophthalmology Society of Australia (NOSA) run busy N/O clinics in the larger public hospital eye departments. There are no full-time N/Os in Australia or New Zealand compared with other countries with much larger populations. Thus, we usually subspecialise in combinations of ocular-motility, medical retina, oculoplastics and general ophthalmology, while our neurological colleagues also deal with strokes, migraines, headaches and epilepsy, among others.

Because many of our patients have chronic conditions with interesting clinical signs, they often feature in trial practice and final FRANZCO exams; this is when our expertise is particularly valued by trainees.

A large proportion of our work involves victims of trauma whether from vehicular accidents, assault with loss of vision, visual field problems from visual pathway damage and double vision from ocular motor nerve palsies etc.

Other intriguing aspects are pupillary, lid and orbital problems plus, of course, stroke complications and the weird and wonderful syndromes that make our work so fascinating. Sorting out visual and/or field loss and cranial nerve palsies from patients with brain tumours, particularly pituitary and suprasellar tumours such as craniopharyngiomas and meningiomas, provide regular work. Hence, we liaise closely and share patients with: neurologists, neurosurgeons, endocrinologists, plastic and maxillofacial surgeons, cardiologists, rheumatologists and immunologists.

A sad indictment of our transition to sedentary lifestyles, plus the rise of poor diets, is the huge rise in prevalence of idiopathic intracranial hypertension (IIH), with its curious predilection for obese young women. The previous term ‘benign intracranial hypertension’ has been replaced by IIH as this disease certainly is rarely benign. I’ve seen too many medicolegal cases of gross field loss and/or legal blindness wherein the patients’ headache was misdiagnosed and treated as migraine as no one had done fundoscopy and thus not detected the papilledema indicating an actual diagnosis of IIH.

In terms of diagnostic advances, a wonderful ‘new’ clinical tool for N/O is OCT. It must be remembered that visual acuity and visual field tests are purely subjective and depend on the will, whim and intelligence of the patient. Testing for a relative afferent pupillary defect (RAPD) was the only objective test available to us. Now, an OCT test gives us objective evidence of damage to the retinal nerve fibre layer and ganglion cell layer which precedes detection by our much less sensitive computerised field tests.

We perform OCT tests prior to neurosurgical decompression of, for example, tumours that are embarrassing the optic nerve or chiasmal function and thus enable us to predict whether visual recovery is likely or not following surgery. This information is of great help. The evolution of neuro-imaging has been the most helpful factor in confirming accuracy of our N/O diagnosis.

In the US, the high rate of sub- specialisation has led to a dearth of general ophthalmologists and so N/Os are filling that niche. Certainly, we tend to be referred patients with symptoms and signs our colleagues are unable to diagnose.

As for a career in N/O, most have done overseas fellowships in the larger N/O centres in the UK, US or Canada, but they need consultant positions in our teaching hospitals to maintain their expertise. Most NOSA members are in the older age group (myself included), but fortunately we’ve welcomed new young colleagues to our ranks. But we need to recruit more. Those interested should arrange time with a N/O to discuss training pathways. Recently trained members returned from overseas can also help.

Finally, may I conclude with a plea to referring optometrists? Please desist in faxing black and white copies of OCT results as these are absolutely indecipherable: much better to email colour copies instead!

ABOUT THE AUTHOR:

Name: Professor John L. Crompton; AM, RFD, MBBS, FRANZCO, FRACS.
Business: Eye Consultants SA.
Position: Clinical Professor (Ophthalmology), University of Adelaide. Past President of NOSA.
Location: North Adelaide plus teaching N/O & ocular-motility surgery at Royal Darwin Hospital.
Years in profession: 44.

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