Keratoconus, unstable, unspecified eye

This code signifies an unstable form of keratoconus, a progressive corneal ectasia characterized by corneal thinning and a conical protrusion, in an unspecified eye. "Unstable" indicates ongoing progression of the corneal steepening or thinning, which can lead to significant visual impairment.

Use this code when documentation confirms a diagnosis of keratoconus with evidence of progression (e.g., increasing K-readings, worsening astigmatism, or decreasing visual acuity) but the affected eye is not specified. This code is appropriate when the physician explicitly states "unstable keratoconus" without laterality.

• Ensure the medical record clearly states "unstable" or provides evidence of progression to justify this specific subcategory.
• Avoid using this code if the laterality (right or left eye) is documented; instead, choose the more specific H18.621 or H18.622.
• This code is typically used for initial encounters or when laterality cannot be determined from the available documentation.