Contents
5 Twenty neuro “rules” to keep you out of trouble
If you read only one chapter in this book, read this one. It covers the most common and most serious mistakes made by ophthalmologists and ophthalmic trainees when dealing with neuro-ophthalmic patients.
Twenty neuro “rules” to keep you out of trouble
The following 20 practice guidelines have a good chance of keeping your patients (and you) safe. Naturally, as with all “rules”, there are rare exceptions to all of these, but they are still useful to keep in the back of your mind in the clinic or ophthalmic emergency department.
Patient presentation
- 1.
Beware the “silent” neuro-ophthalmic patient!
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patients with optic nerve or brain tumors will sometimes be referred to you as “cataract”, “glaucoma”, “optic neuritis”, “ischemic sixth nerve palsy”, “senile ptosis” or other benign-sounding diagnoses ( Fig. 1.1 )
1.1
This 62-year-old patient was referred to an ophthalmologist “for treatment of cataracts”. On initial examination visual acuity was right 20/40, left 20/60 despite only very early cataracts being present; color vision was not assessed, visual fields were not tested and no pupillary examination was performed. It was only when vision did not improve after bilateral cataract surgery that another cause was eventually suspected; this pituitary tumor was diagnosed as the real cause of the patient’s blurred vision 2 years after first ophthalmic contact. Final visual acuity after tumor excision was only 20/120 in each eye; visual outcome could have been improved by earlier diagnosis of the tumor.
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Examination
- 2.
Every new eye patient complaining of blurred vision should have:
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confrontation field testing (peripheral and central)
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a “swinging torch test” for a relative afferent pupillary defect (RAPD) before dilation
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perimetry if either of these is abnormal, the patient describes a field defect, or the degree of visual loss is not consistent with the ocular examination ( Fig. 1.2 )
1.2
This 16-year-old girl presented to the ophthalmology department complaining of headaches, blurred vision in her right eye and flashing lights. Visual acuity was 20/20 in each eye and intraocular examination was normal. No visual field testing was performed, and the patient was told her symptoms were due to migraine. Re-examination by another doctor revealed a right homonymous hemianopia ( A , B ) that was easily detected with confrontation testing; C a left thalamic mass lesion was diagnosed on MRI; further investigation showed this to be a cryptococcal abscess.
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Blurred vision or field loss
- 3.
You can never diagnose the cause of optic nerve dysfunction just by looking at the disc ( Fig. 1.3 ).
1.3
Hundreds of different diseases can present with a similar optic disc appearance. For example, these swollen discs have been caused by A sarcoid optic neuritis, B optic nerve infiltration by lymphoma, C non-arteritic AION, D papilledema, E Leber’s hereditary optic neuropathy, F cat scratch disease, G idiopathic optic neuritis and H optic nerve sheath meningioma. In no case was the disc appearance diagnostic; diagnosis was made on careful history, other examination, perimetry and other investigations as suggested in the management flowchart on p. 31 .
- 4.
All patients with non-traumatic ACUTE optic nerve dysfunction who do not meet all the clinical diagnostic criteria for either:
require urgent referral to a neuro-ophthalmologist (or, if this is not possible, urgent investigation as suggested on p. 38 ) ( Fig. 1.4 ).
1.4
Not all acute optic neuropathies in young adults are optic neuritis! A This 32-year-old woman presented with progressive visual loss in the right eye over 3 weeks (right 20/60), pain behind the right eye, a right RAPD and normal optic discs. Her ophthalmologist diagnosed “retrobulbar optic neuritis” and reassured the patient that her vision would return spontaneously. Three months later, vision had worsened (20/200) and optic atrophy had developed; B MRI showed this large nasal tumor compressing the right optic nerve. Vision did not improve after removal of the tumor. Visual outcome would probably have been better with earlier diagnosis. For how to safely diagnose typical optic neuritis, see p. 35 .
Not all acute optic neuropathies with a swollen disc are AION! This 55-year-old hypertensive man complained of progressive loss of vision in his right eye over 7 days. His ophthalmologist found C right visual acuity to be 20/40, a right RAPD and right optic disc swelling. A right inferior altitudinal scotoma was detected on perimetry. The ophthalmologist diagnosed “anterior ischemic optic neuropathy” and advised the patient that there was no treatment. Ten weeks later, right visual acuity (VA) had deteriorated to 20/400 and the right disc had become pale; further investigation revealed an increased serum angiotensin converting enzyme (ACE) and D hilar lymphadenopathy on chest x-ray. Biopsy of a lower eyelid conjunctival granuloma confirmed the diagnosis of sarcoidosis. Because diagnosis was delayed, right VA only returned to 20/80 with steroid treatment. For how to safely diagnose AION, see p. 36 .
- 5.
All patients with CHRONIC optic nerve dysfunction who do not meet all the clinical diagnostic criteria for glaucomatous optic neuropathy ( p. 37 ) require referral to a neuro-ophthalmologist (or, if this is not possible, investigation as suggested on p. 38 ) ( Fig. 1.5 ).
1.5
Not all chronic optic neuropathy with a “cupped” disc is glaucoma! This 48-year-old patient asked her optometrist for a change of glasses because of blurred vision. The optometrist found A , B visual acuity right 20/30, left 20/60, intraocular pressures of right 25, left 29, and bilateral disc “cupping”, and referred the patient to an ophthalmologist for treatment of possible glaucoma. Perimetry was attempted but fields were said to be “unreliable”; the ophthalmologist commenced glaucoma eyedrops. One year later, visual acuity had decreased further to right 20/60, left 20/200, and optic disc pallor was noted; C MRI revealed a large suprasellar meningioma. Visual outcome would probably have been better with earlier diagnosis. For how to safely diagnose glaucoma, see p. 37 .
- 6.
Amblyopia is a specific diagnosis, with specific diagnostic features; never use a history of “lazy eye” as the explanation for worsening vision. Features of optic nerve disease should be absent and a demonstrable cause for the amblyopia should be present ( Fig. 1.6 ).
1.6
A 38-year-old woman presented to her ophthalmologist complaining of blurred vision in her left eye and the left eye “turning in”. She said that the left eye had always been “a bit lazy” so the ophthalmologist recorded “left amblyopia” as the cause of the blurred vision without checking for an RAPD. The ophthalmologist diagnosed “decompensated congenital esotropia” and attributed the poor vision in the left eye (20/80) to “strabismic amblyopia”. Eventually another ophthalmologist investigated the patient and found A , B a large internal carotid artery aneurysm causing compressive optic neuropathy and sixth nerve palsy. Unfortunately, by this time, the left eye was blind.
- 7.
Whenever you look in an eye, think: is the level of vision explained by visible intraocular disease? If not, there could be disease behind the eye. Unexplained poor vision, optic atrophy, disc cupping or field loss always requires investigation ( Fig. 1.7 ).
