Thyroid Eye Disease (Graves' Ophthalmopathy)
The provisional diagnosis is Thyroid Eye Disease (TED), also known as Graves' ophthalmopathy, given the patient's known Graves' disease, bilateral proptosis, upward gaze limitation, and dry cornea. 1
Type of Double Vision
This patient has binocular diplopia (double vision that resolves when either eye is closed), which results from extraocular muscle enlargement and restriction causing disconjugate gaze between the two eyes. 1, 2 The upward gaze limitation indicates inferior rectus muscle involvement, which is the most commonly affected muscle in TED and causes vertical diplopia that worsens when looking up. 2
Four Additional Clinical Signs in Thyroid Eye Disease
Eyelid retraction - Upper eyelid retraction creates a characteristic "stare" appearance and contributes to corneal exposure 3, 4
Periorbital edema and chemosis - Inflammatory swelling of the eyelids and conjunctival injection/edema are hallmarks of active disease 4, 5
Lagophthalmos - Incomplete eyelid closure due to proptosis and lid retraction, measurable as the distance between lid margins when attempting to close eyes 6
Extraocular muscle enlargement on imaging - CT or MRI demonstrates characteristic fusiform enlargement of extraocular muscles (typically sparing the tendinous insertions), with inferior and medial recti most commonly affected 1, 6
Three Blinding Complications
1. Compressive Optic Neuropathy - The most serious sight-threatening complication occurs when enlarged extraocular muscles at the orbital apex compress the optic nerve, causing progressive vision loss, color vision defects, visual field defects, and afferent pupillary defect. 3, 6, 4 This represents a true ophthalmic emergency requiring urgent high-dose corticosteroids or surgical orbital decompression. 3, 6
2. Exposure Keratopathy - Severe proptosis combined with lagophthalmos and eyelid retraction leads to corneal desiccation, epithelial breakdown, ulceration, and potentially corneal perforation or infectious keratitis. 3, 6, 4 The dry cornea noted in this patient already indicates early exposure changes.
3. Subluxation of the Globe - Extreme proptosis can result in anterior displacement of the globe beyond the orbital rim, causing inability to close the eyelids, acute corneal exposure, and potential vascular compromise. 4 This rare but catastrophic complication requires emergency surgical intervention.
Critical Management Considerations
Immediate ophthalmology referral is mandatory to assess for optic neuropathy through visual acuity, color vision testing (Ishihara plates), visual fields, pupillary examination, and fundoscopy. 3
Smoking cessation is non-negotiable as smoking significantly worsens orbitopathy progression and reduces treatment response. 3
Optimize thyroid function with methimazole as the preferred antithyroid drug, maintaining euthyroid state since both hyper- and hypothyroidism can worsen eye disease. 3
MRI or CT orbits with contrast should be obtained to document extraocular muscle enlargement, assess for optic nerve compression at the apex, and establish baseline severity. 1
Ocular lubricants are essential - Aggressive lubrication with preservative-free artificial tears during the day and ointment at night to prevent exposure keratopathy. 3
Common Pitfalls to Avoid
Do not assume mild symptoms mean mild disease - Optic neuropathy can occur with minimal external signs and requires active screening. 3, 6
Never perform strabismus surgery before orbital decompression if both procedures are anticipated, as decompression unpredictably changes ocular alignment. 3
Screen for myasthenia gravis as its incidence is increased in TED patients, and both conditions can cause diplopia and ptosis. 3
Avoid starting corticosteroids empirically without adequate workup, as this can mask other diagnoses and worsen outcomes in unrecognized infections or malignancies. 7