H40.00 ICD-10-CM Code: Preglaucoma, unspecified

H40.00 is the ICD-10-CM diagnosis code for preglaucoma, unspecified. H40.00 sits in the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59), within the section covering glaucoma (h40-h42).

Header codes like H40.00 cannot be reported on claims directly, they organize child codes that share clinical context but the actual diagnosis must be coded to the highest level of specificity supported by the documentation. Coders should look at H40.00's child codes and select the one that matches the patient's documented presentation, since payers reject header codes submitted as the primary diagnosis. For risk adjustment workflows, header codes never contribute to a Medicare Advantage member's RAF score on their own; only billable child codes that happen to map to a payment HCC affect risk-adjusted plan payments.