ICD-10-CM 2027
ICD-10 code for deep keratitis
From the official ICD-10-CM alphabetic index entry “Keratitis (nodular) (nonulcerative) (simple) (zonular) › deep”. Page updated September 29, 2026.
About coding deep keratitis
The ICD-10-CM code for deep keratitis is H16.309 (Unspecified interstitial keratitis, unspecified eye). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on H16.309.
Within H16.30, choose H16.309 (unspecified eye) only when documentation doesn't support a more specific option: right eye (H16.301), left eye (H16.302) and bilateral (H16.303).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 124 (Other Disorders of the Eye with MCC or Thrombolytic Agent, relative weight 1.2471) and DRG 125 (Other Disorders of the Eye without MCC, relative weight 0.7702), in MDC 02 (Diseases and Disorders of the Eye), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific deep keratitis codes (official index)
- specified type NEC H16.399 — Other interstitial and deep keratitis, unspecified eye
Common questions about deep keratitis ICD-10 codes
What is the ICD-10 code for deep keratitis?
- H16.309 — Unspecified interstitial keratitis, unspecified eye. More specific codes apply when the documentation supports them: H16.399.
Is H16.309 billable?
- Yes. H16.309 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can H16.309 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict H16.309 as a principal diagnosis.
Is H16.309 a CC or MCC?
- No. H16.309 is neither a CC nor an MCC under MS-DRG v44.0.