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As many coding professionals may know by now, the ICD-10-CM coding system brings with it several significant changes from the ICD-9-CM coding system. In general, the character length of the codes will increase—from ICD-9’s three to five to ICD-10’s length of up to seven.

In ICD-9 alphanumeric characters only were used for V, E and M codes, which designated certain code types and certain sections of the code book. In ICD-10 any code in any section of the book could be alphanumeric. A code may begin with any letter, A–Z, or a number, 0–9. The letters “O” and “I” will not be used in ICD-10 to avoid confusion with the number 0 and 1.

“Laterality” also is a new feature in ICD-10—one that did not exist for ICD-9 code assignment. For diseases and conditions that involve bilateral anatomy, the code set has increased significantly due to this feature. In ICD-10, there is a code for a bilateral condition, and a separate code for each unilateral side, specifically left and right.

One such area significantly affected by this feature is ophthalmologydiseases of the eye. In the ICD-10-CM code book, this specialty is covered in Chapter 7: Diseases of the Eye and Adenex, and the code set begins with the letter H.

Moving from ICD-9-CM to ICD-10-CM

The ICD-9 code book includes one diagnosis code choice for a nuclear cataract, which is 366.16—nuclear sclerosis. This code includes cataracta brunescens and nuclear cataract.

When assigning a diagnosis code for a nuclear cataract from the ICD-10 code book, there is a choice of four codes. You will need to “see” more specific detail in the practitioner’s documentation.


366.16      Nuclear sclerosis

H25.1 Age related nuclear cataract * fourth character required

Includes:  Cataract brunescens

Includes:  Cataract brunescens

Nuclear cataract

Nuclear sclerosis cataract

H25.10 Age related nuclear cataract, unspecified eye

H25.11 Age related nuclear cataract, right eye

H25.12 Age related nuclear cataract, left eye

H25.13 Age related nuclear cataract, bilateral

As you can see in the example above, the ICD-9 diagnosis code description is very general. It does not require very specific documentation to assign this code. The ICD-10 diagnosis code is more specific and will require that the documentation contain more specific information for the most accurate code assignment.

Specifically, the documentation should include the disease and the anatomical side of the body that the disease affects—right, left, or both. Always assign the code based on the documentation and beware when more than one condition is listed. For example, the patient may have bilateral cataracts but another medical reason, a broken leg, may be the reason for the inpatient admission. You would need to assign the code for the bilateral cataracts, secondary to the broken leg, as described in the documentation.

If the patient is an outpatient and the reason for the encounter is for the treatment of the cataract, be careful not to fall into the bilateral trap. For example, the documentation may state “has bilateral cataracts.” When you read the documentation carefully, you may see that the patient may have bilateral cataracts, but this encounter may only be for the treatment of the left side. You will want to assign a diagnosis code for the left eye only and not the bilateral diagnosis code.

As always, try to assign the most specific, accurate code based on the documentation to reflect the patient’s visit. If that is not always possible, an “unspecified eye” code does exist.

Documenting for ICD-10 will be a new experience for the physicians also. They may need some coaching to identify what the coding professional needs to see to determine the most accurate code.

Also be aware that the information you specifically need may not always appear on the discharge summary but may be available in other parts of the record. Thoroughly read all other acceptable documents in the record before querying the physician or assigning an unspecified code.

About the Author

Mary C. Maloy is an AHIMA-approved ICD-10 Instructor and a senior healthcare consultant for Panacea Healthcare Solutions, Inc., St. Paul, MN.

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