To successfully be reimbursed for services rendered, claims you submit to payers must have a procedure code and a correctly linked diagnosis code submitted via International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM). Follow these guiding principles to ensure you select the appropriate ICD-10-CM code.

ICD-10 Codes Should Be Accurate and Complete 

The best code is an actual diagnosis (e.g., H43.811 Vitreous degeneration, right eye). Lacking a diagnosis, the next best code is a sign or a symptom (e.g., H43.391 Floaters, vitreous, right eye). However, when there is no sign or symptom to report, the last resort is supplying a circumstance (e.g., H53.19 Other subjective visual disturbances).

ICD-10-CM codes can be four to seven characters long, and the sixth or seventh character may be alpha or numeric. When a code in the ICD-10-CM Alphabetical Index or Tabular List has a dash (-) at the end, it indicates that additional characters are necessary to complete the code. It is rare that a billable ICD-10-CM code contains only three digits. When a code indicates laterality (e.g., right, left, bilateral or right upper lid, left upper lid, etc.), provide all the required characters; otherwise, the claim will be denied because of an incorrect code. After choosing a code from the ICD-10-CM Alphabetical Index verify the accuracy of the code in the Tabular List.

In ICD-10-CM many but not all glaucoma diagnoses require staging, indicated by a seventh digit. If the code includes eye indicators, then stage each eye. If both eyes have the same stage, select the bilateral code and indicate the stage as the seventh character. If the ICD-10-CM code has no eye indicator, code for the stage of the most severely affected eye. See the Glaucoma Guide at ICD-10-CM for Ophthalmology.

Injury and trauma codes require identification of the patient visit type, indicated by the characters A (an initial encounter), D (a subsequent encounter) and S (for sequela). The A is used as the seventh character when a physician actively treats a condition during an initial encounter, whereas the D is used for encounters after the physician performs the initial treatment, such as when the patient receives care during the healing or recovery phase. ICD-10-CM codes that end in an S are typically submitted to third-party liability, such as workers compensation.

Do not code “probable,” “suspected,” “possible,” or “rule out” codes. Code only what the patient has.
When you have not determined an actual disease or problem, you should not report an ICD-10 code of a diagnosis that is yet to be confirmed. The appropriate ICD-10-CM codes should be related to what you do know — signs, symptoms, complaints, or existing systemic disease.
It is best to use the neoplasm of uncertain behavior classification (D48.1) for eyelid lesions with no confirmed pathology. Likewise consider “pain in and around the eye” (H57.1-) when the patient's complaint has no confirmed ophthalmic problem and you are referring to an ear, nose, and throat physician.

Only report diagnosis codes that pertain to the current encounter.
Often electronic health record (EHR) systems will bring past diagnoses forward when initiating an encounter. Only conditions that pertain to the patient’s complaint and problems addressed during the visit today should be submitted to the payer.

Do not code conditions that are resolved. 
There are no rules or guidelines for what constitutes an acceptable period to code a diagnosis once the condition has resolved. Physicians should use their best judgment when deciding whether a code is appropriate.
For example, a patient returns for follow-up for conjunctivitis, but the conjunctivitis has now resolved. Is the conjunctivitis code still appropriate? In this case, yes. The reason for the encounter was clearly the conjunctivitis that the patient experienced. Using this code establishes medical necessity.