Dysthyroid optic neuropathy in a smoker with active Graves disease
A 54-year-old woman with Graves disease diagnosed 14 months ago, treated with carbimazole and biochemically borderline (TSH 0.02 mIU/L, free T4 21 pmol/L), attends with three weeks of worsening double vision and a grey veil over her vision. She smokes 20 cigarettes a day. Acuity is 6/12 OD and 6/9 OS, with reduced Ishihara plate scores (4/17 right, 11/17 left). There is a right relative afferent pupillary defect, bilateral lid retraction with 3 mm of proptosis (24 mm right, 23 mm left), and restricted elevation and abduction in both eyes. Intraocular pressure is 26 mmHg in upgaze and 18 mmHg in primary position. Dilated fundoscopy shows a swollen right optic disc. CT of the orbits shows marked apical crowding with a straightened optic nerve and no mass lesion. She asks whether she can be treated as an outpatient because she cares for her elderly mother at home.
1. Make the diagnosis and explain which findings localise the problem and which are misleading incidental findings.
Read the worked answer
This is dysthyroid optic neuropathy (DON) in active thyroid eye disease - sight-threatening and requiring urgent treatment.
Localising findings:
- Reduced acuity with reduced colour vision and a right relative afferent pupillary defect indicate optic nerve dysfunction; the RAPD is present because the disease is asymmetric (it is typically absent in symmetric bilateral disease, which is why its absence is not reassuring).
- Disc swelling with apical crowding and a straightened optic nerve on CT is the anatomical substrate - enlarged extraocular muscles compressing the nerve at the orbital apex.
- The grey veil is consistent with a compressive optic neuropathy rather than a media problem.
Findings that mislead:
- The pressure rise from 18 to 26 mmHg on upgaze is a restrictive myopathy phenomenon, not glaucoma; it reflects the tethered inferior rectus being stretched. It should be documented but not treated as primary glaucoma.
- Proptosis and lid retraction are signs of orbital disease but do not quantify optic nerve risk; severe neuropathy can occur with modest proptosis because the crowded apex, not the anterior orbit, is the problem.
Confirm and stage: visual field testing (central or altitudinal defect), OCT retinal nerve fibre and ganglion cell layers, and colour vision. Assess disease activity (clinical activity score) because treatment choices differ between active and quiescent disease. Ask specifically about smoking, which is the strongest modifiable risk factor for progression and for a poor response to treatment.
2. She is admitted. Outline your acute treatment, including the steroid regimen, monitoring, and the alternatives if she does not respond.
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Immediate treatment: high-dose intravenous glucocorticoid. A common regimen is methylprednisolone 500–1000 mg daily for three consecutive days, or 500 mg weekly for six weeks, followed by oral prednisolone 1 mg/kg/day tapering over weeks to months. The evidence supports intravenous pulses over oral steroids for DON in terms of efficacy and tolerability.
Before and during treatment: baseline blood pressure, blood glucose or HbA1c, renal and liver function, electrolytes, ECG if cardiac risk, and screen for infection (including hepatitis B and tuberculosis where relevant). Monitor glucose and blood pressure daily; watch for mood change, insomnia and arrhythmia. Start bone protection and gastric protection if a long taper is anticipated.
If there is no improvement within 1–2 weeks, or if vision deteriorates on steroids, proceed to urgent orbital decompression - typically a balanced two- or three-wall decompression, removing the orbital floor and medial wall with or without the lateral wall. Do not wait for steroid side effects to accumulate in a patient who is not responding.
Other options: orbital radiotherapy can be used in active disease, particularly in patients who are not severely proptotic and who do not smoke, but its effect takes weeks, so it is not a rescue for acute neuropathy. Steroid-sparing biologics such as teprotumumab, rituximab or mycophenolate have a role in active moderate-to-severe disease, but decompression remains the definitive rescue for compressive neuropathy.
Smoking cessation is part of the emergency treatment, not an optional extra - refer her to a cessation service and explain that continued smoking substantially worsens both the disease and the response to therapy.
3. Once the optic neuropathy is controlled, how do you plan the remainder of her care over the next two years?
Read the worked answer
Steroid phase: taper prednisolone gradually over months, watching for relapse of optic neuropathy and for steroid morbidity. If she relapses on tapering, consider a second course of intravenous pulses plus a steroid-sparing agent, or bring decompression forward.
Thyroid control: aim for a euthyroid state with antithyroid drugs, but be aware that radioiodine can worsen active ophthalmopathy, particularly in smokers; if radioiodine is ever needed, it should be covered with steroids and used when the eye disease is quiescent. Total thyroidectomy is an alternative if control is difficult. Coordinate with endocrinology - she is currently borderline hyperthyroid, which should be corrected.
Rehabilitative surgery, in this order, once the disease is quiescent for at least six months: orbital decompression if proptosis or exposure persists (which may already have been done), then strabismus surgery for the restrictive diplopia, then eyelid surgery for retraction and exposure. Operating on the lids or muscles while the orbit is still active invites recurrence.
General measures: continue smoking cessation support, treat ocular surface disease and exposure with lubricants and taping, monitor intraocular pressure with a plan for glaucoma assessment once congestion settles (the pressure rise on upgaze should resolve), and consider selenium or other supportive measures only where evidence supports them. Warn her that diplopia may persist and that further surgery is common; document all of this in a multidisciplinary record.