ICD-10 Code H49.42 – Progressive external ophthalmoplegia, left eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H49.42 – Progressive external ophthalmoplegia, left eye
What it is
This code identifies progressive weakness of the eye muscles affecting the left eye. It is used when the chart specifies progressive external ophthalmoplegia limited to that side.
Clinical signs
Typical findings include slowly worsening limitation of eye movements and drooping eyelid on the left. Clinical features vary; refer to documentation.
When to use this code
Use H49.42 when the provider documents progressive external ophthalmoplegia and clearly states the left eye is involved. It may be supported by exam notes showing restricted extraocular motion or ptosis on that side. If laterality is not documented, check documentation before coding.
Do not use for
Do not use this code for nonspecific ptosis, general diplopia, or eye movement problems without a documented diagnosis of progressive external ophthalmoplegia. Do not assume laterality if the record does not state left eye.
Coding tip
Confirm both the diagnosis and laterality in the provider note before assigning H49.42.