Graves’ disease presenting as unilateral anterior ischaemic optic neuropathy

Abstract

We report a case of a 28-year-old man who presented with 1-day history of sudden diminution of vision in the right eye. Examination showed unilateral exophthalmos with restricted eyeball movement on upward gaze in the right eye. MRI of the orbit showed no evidence of compression of the optic nerve on the right side. Visual-evoked potential showed prolonged P100 in the right eye. Fundus examination revealed swollen optic disc and para papillary nerve fibre layer splinter haemorrhages with corresponding altitudinal field defect on perimetry suggestive of anterior ischaemic optic neuropathy.

Background

A common cause of optic neuropathy associated with Graves’ disease is hypertrophy of extraocular muscles causing compression of optic nerve at orbital apex. Anterior ischaemic optic neuropathy (AION) causing vision loss in Graves’ disease is a very rare entity.

To the best of our knowledge only two cases were reported in the literature showing association of Graves’ disease with AION.¹ If diagnosed early, prompt treatment with steroid can alter the course of AION. We recommended AION as a cause for diminished vision be ruled out, in all patients presenting with sudden visual loss in patients with Graves’ disease.

Case presentation

A 28-year-old man presented with sudden onset of diminution of vision in the right eye since 1 day. There was no history of pain in the right eye, no associated features like history of headache, jaw claudication, arthralgias, diabetes, smoking and hypertension. There was no history of trauma to the right eye, sleep apnoea. The patient had history of easy fatigability, weight loss with increased appetite, tremulousness of hands especially in outstretched posture. Examination revealed ‘butterfly-shaped’ swelling in the region of thyroid, resting tachycardia, postural tremors, unilateral (right) proptosis (figures 1 and 2)—features suggestive of Graves’ disease with opthalmopathy. Free T3, T4 were elevated with very low thyroid-stimulating hormone (TSH). Thyroid scan showed diffuse increased uptake of radioiodine. Based on the above clinical and biochemical tests, diagnosis of Graves’ disease was arrived at. Eye examination showed visual acuity of 3/60 for distance, intraocular pressure of 12 mm Hg and relative afferent pupillary defect (RAPD) on the right side. Fundus examination showed segmental pallid disc oedema with inferior peripapillary haemorrhages in the right eye (figure 3) with corresponding superior altitudinal field defect noted on perimetry testing (figure 4). Other systemic examinations were normal.

Figure 1.

MRI of the orbit showing no evidence of compression of the optic nerve on the right side.

Figure 2.

Unilateral right-sided proptosis in our patient of Graves’ disease.

Figure 3.

Fundus photograph of the right eye showing small optic disc which is a risk factor for anterior ischaemic optic neuropathy (AION), and peripapillary haemorrhage was characteristic of AION.

Figure 4.

Perimetry showing right superior altitudinal field defect.

Investigations

Blood test including ELISA/western blot for HIV, Venereal Disease Research Laboratory (VDRL) for syphilis were negative and purified protein derivative testing skin test with chest X-ray were normal. Other routine blood investigations including complete blood picture, renal, liver function tests, C reactive protein levels were normal.

MRI of the orbit showed no hypertrophy of extraocular muscles and no evidence of compression of optic nerve head in the right eye (figure 1).

Other workup to rule out causes of vasculitis such as antinuclear antibody, antineutrophil cytoplasmic antibody, HIV ELISA and VDRL for syphilis were negative.

• Chest X-ray was normal and Manoux test was negative.

• Visual-evoked potential showed prolonged P100 in the left eye.

• Thyroid scan showed diffuse increased uptake of radioactive iodine.

Differential diagnosis

We considered optic neuritis as a close differential diagnosis, but there was no associated pain or redness in the right eye and fundus examination showed swollen disc and peripapillary haemorrhage which is characteristic of AION and rarely seen in optic neuritis.

Ocular infections were also less likely as there was no history of fever, and leucocyte counts were within normal limits and the clinical profile was not suggestive of the same.

Thyroid opthalmopathy was not considered in view of MRI orbit showing no evidence of optic nerve head compression or any significant hypertrophy of extraocular muscles radiologically.

Treatment

The patient was treated with high-dose oral steroids followed by rapid taper.

Outcome and follow-up

The patient on follow-up after 2 weeks reported only minimal improvement of vision in the right eye (right eye vision of 6/60).

Discussion

Anterior ischaemic optic neuropathy is the most common optic neuropathy in adults above 50 years of age.² AION is of two types: arteritic and non-arteritic, the latter one being more common. AION usually results from idiopathic ischaemic insult of the optic nerve head and causes acute, monocular, painless visual loss. Our patient presented with sudden onset of painless visual loss in the right eye, though AION as cause of vision loss in young age is uncommon, in view of the presence of classical presentation and examination showing optic disc oedema and inferior peripapillary splinter haemorrhages, possibility of AION was most likely. Association of Graves’ disease with AION though rare cases were reported in the past.¹

Arteritic AION is most commonly due to giant cell arteritis. Young onset, with no history of headache or jaw claudication with low erythrocyte sedimentation rate and low C reactive protein levels were some of the pointers against arteritic AION in our patient. At the same time, diabetes, hypertension,³ smoking, hyperlipidaemia and obstructive sleep apnoea⁴ which are some of the most common risk factors for non-arteritic AION were absent in our patient.

Our patient had small optic disc (figure 3) which is one of the risk factors for ischaemic optic neuropathy.⁵ The patient had visual acuity of 3/60, perimetry showing superior altitudinal field defect (figure 4) and fundus examination showing swollen disc and peripapillary haemorrhage characteristic of AION. So the patient was started on high-dose oral steroids, Injection methylprednisolone 1 g intravenous once a day for 5 days followed by tapering dose of oral steroids (prednisone 1 mg/kg body weight) over 14 days and stopped.⁶ After 2 weeks, patient reported minimal improvement in vision, with a vision of 6/60 in the right eye.

Learning points.

• Thyroid ophthalmopathy secondary to compression of optic nerve by hypertrophied extraocular muscles is a common cause of diminution of vision in Graves’ disease.

• Anterior ischaemic optic neuropathy is a rare but important cause for potential blindness in a case of Graves’ disease.

• Early treatment with steroids may improve visual acuity.