ICD-10 Code H16.309 – Unspecified interstitial keratitis, unspecified eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H16.309 – Unspecified interstitial keratitis, unspecified eye
What it is
Use this code for interstitial keratitis when the corneal inflammation is documented, but the cause is not specified and the affected eye is not identified. It indicates a deeper corneal inflammatory process rather than a superficial keratitis.
Clinical signs
Typical findings include corneal haze or opacity, stromal inflammation, redness, pain, and reduced vision. Clinical features vary; refer to documentation.
When to use this code
Use H16.309 when the chart states interstitial keratitis but does not name the eye or provide a more specific cause. It is appropriate when laterality is missing or the provider documents the condition as unspecified. If the record later clarifies the eye or etiology, update coding accordingly.
Do not use for
Do not use this code for keratitis with a documented infectious, traumatic, or other specific cause. Do not use it when the provider identifies the eye and a more specific code is available.
Coding tip
Check the note for laterality and cause before assigning H16.309; unspecified coding should be a last resort.