What is the initial treatment for dysthyroid optic neuropathy?

Initial Treatment for Dysthyroid Optic Neuropathy

High-dose intravenous methylprednisolone is the first-line treatment for dysthyroid optic neuropathy, followed by orbital decompression surgery if response is inadequate. 1, 2

Understanding Dysthyroid Optic Neuropathy (DON)

Dysthyroid optic neuropathy is a sight-threatening complication of thyroid eye disease (TED) that occurs in approximately 5-8% of TED patients. 3, 1 It requires prompt recognition and management to prevent permanent vision loss.

Pathophysiology

• Compression of the optic nerve at the orbital apex by enlarged extraocular muscles (>90% of cases) 3
• Excessive stretching of the optic nerve (minority of cases) 3, 1

Risk Factors

• Advancing age 3, 1
• Male gender 3, 1
• Smoking 3, 1
• Diabetes mellitus 3, 1

Diagnosis

Diagnosis is based on a combination of clinical findings, with at least two of the following:

• Decreased visual acuity unexplained by other ocular disorders 3, 1
• Decreased color vision 3, 1
• Relative afferent pupillary defect 1
• Visual field defects 1
• Optic disc edema 3, 1

Diagnostic Imaging

• CT or MRI showing apical crowding with enlarged extraocular muscles compressing the optic nerve 3
• Optical coherence tomography (OCT) to help confirm diagnosis 3

Treatment Algorithm

First-Line Treatment

• High-dose intravenous methylprednisolone (ivMP) - 1g daily for 3 consecutive days 4, 2
  • Rapid improvement in visual acuity can be seen immediately after completion of pulse therapy 4
  • Maintenance with oral prednisone following pulse therapy 4

Second-Line Treatment (if inadequate response to steroids)

• Orbital decompression surgery 3, 1, 2
  • Indicated when response to steroids is poor or absent
  • Can have positive outcomes even in cases of severe vision loss or delayed surgery 3
  • Most common surgical complication is worsening strabismus 3

Alternative Treatments

• Orbital radiotherapy 3, 5, 2

  • May delay or avoid the need for surgery 3
  • Can be combined with corticosteroids in high-risk individuals 3
  • Beneficial for patients with restricted ocular motility who are poor surgical candidates 2

• Biologic targeted therapy 2

  • Emerging options include teprotumumab and tocilizumab 2
  • May be considered for patients with contraindications to ivMP/orbital decompression 2
  • Rituximab should be avoided due to conflicting data and risk of adverse events 2

Monitoring and Follow-up

• Careful surveillance for optic neuropathy with attention to acuity, color vision, visual fields, pupillary exam, and fundus exam 6
• OCT and Humphrey visual fields to monitor response to treatment 3

Important Considerations and Pitfalls

• Delayed diagnosis and treatment can lead to permanent vision loss 3, 1
• Patients with risk factors should be referred promptly to an ophthalmologist or specialized clinic 3
• If orbital decompression is indicated, strabismus repair should be delayed until after decompression as new onset or exacerbated strabismus may result 6
• Even with appropriate management, some cases of DON can result in irreversible loss of visual function 1

Management requires a multidisciplinary approach involving ophthalmologists, endocrinologists, and sometimes orbital specialists for optimal outcomes 1.