Hypotony of unspecified eye due to ocular fistula

This code describes a condition where the intraocular pressure (IOP) in an unspecified eye is abnormally low, specifically caused by an ocular fistula. An ocular fistula is an abnormal communication or tract that allows aqueous humor to leak from the eye, leading to hypotony. This can result from trauma, surgery, or disease.

Use this code when documentation clearly states hypotony in an unspecified eye and explicitly identifies an ocular fistula as the underlying cause. This diagnosis is typically supported by ophthalmological examination findings, including low IOP measurements and evidence of aqueous humor leakage.

• Ensure the documentation specifies "unspecified eye" if laterality is not documented. If laterality is known, use the more specific codes (H44.421 for right eye, H44.422 for left eye).
• Verify that the hypotony is directly attributed to an ocular fistula; other causes of hypotony (e.g., ciliary body detachment) have different codes.
• Code any underlying cause of the fistula (e.g., surgical complication, trauma) as an additional diagnosis, if applicable and documented.