Navigating the ICD-10 Transition

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One of the most important things in  preparing for ICD-10 is to understand  the structure of the ICD-10 book, which is laid out intelligently into chapters  and subchapters. Once a practitioner  understands the anatomy of the book,  it’s easy to navigate in a functionally  successful way. There are two main  sections - the alphabetical index, where the coding process begins with the first three digits, and tabular list to finalize with the fourth, fifth, sixth and seventh digits if necessary.

If there’s one word to describe ICD-10, it is the word  specificity. The ICD-9 book has up to 14,000 codes. The  new ICD-10 book has more than 140,000 codes. The  transition is effective October 1, 2015 and unfortunately there will be no overlap period where both code sets can be used. The transition may be difficult because there is very little in common between our current coding  paradigm and the new one. More importantly, it requires the doctors, not the staff, to do most of the coding since often only a doctor can answer the questions that are  required for the most specific level of coding. 

The Alphabetical Index is a list of terms and  corresponding codes that also contains the Index of Injury, the Index of Disease, Table of Neoplasms, the Table of Drugs and Chemicals and the Index of External Causes of Injury. 

The Tabular List is a chronological list of codes divided into chapters based on body systems. There are 21 chapters broken into different specialties. Eye care practitioners will primarily use Chapter 7, Diseases of the Eye and Adnexa. These codes all begin with the letter “H.” 

Inside Chapter 7 there are subchapters based on  anatomical area, such as disorders of eyelids, lens,  conjunctiva, cornea, retina/choroid, glaucoma, vitreous, optic nerves, refraction, etc. Chapter 7’s last subchapter  has codes for intra-operative and post procedural  complications, which must be coded when encountered.

There will be times when eye specialists will need to leave Chapter 7 and move to different chapters. Some important chapters to note:

Chapter 4 for endocrine, nutritional and metabolic diseases is where one will find codes for diabetic  complications such as diabetic retinopathy. 

Chapter 12 has codes for skin, for dermatologic conditions like herpes zoster, herpes simplex,  acne rosacea and others. 

Chapter 18 codes describe symptoms and signs as  opposed to an exact diagnosis. They are accepted when a definitive diagnosis has not yet been established. 

Chapter 19 is where one would select codes for injuries  including ocular injuries. Eye practitioners should limit  their search to injuries of the head (S00. to S09.). The  sub-category, injuries to the eye, is then subdivided  into injuries at the eye and orbit (S05.-), and injury of the eyelid and periocular area (S00-). After selecting a  Chapter 19 ocular trauma code it is recommended, but  not required, that one proceed to Chapter 20 and search the external cause codes.

Chapter 20 codes describe the external causes of  morbidity. It is recommended to use a full range of  external cause codes to completely describe the cause  of the injury, place of occurrence, activity of the patient at the time of the event and the status for all other  injuries due to an external cause.

Final codes in ICD-10 may be 3, 4, 5, 6 or 7 characters long. The format and structure is consistent. The first character  is always a letter and the second character is numeric.  Characters 3-7 can be either alpha or numeric and the  decimal point is always after the third character. Sub  categories are characters four and five.

Often codes will contain blank spaces, in which case it is necessary to insert the letter “X” to be used as a placeholder character. This allows the claims to be successfully sent through third-party clearinghouses and for future  expansion of codes without revision of the book itself.

Seventh Character Code Extensions are always necessary in coding for injuries. The seventh character extension for a patient receiving their initial treatments is the letter “A,” subsequent encounters would be defined by the letter “D,” and the letter “S” in the seventh character is used to define any sequelae indicating a complication or a condition that arises as a result to the initial Injury.

Seventh character extensions are also used in glaucoma coding to define stage or severity of disease. The numeral “1” indicates mild stage glaucoma, “2” defines moderate stage glaucoma, “3” defines severe stage of glaucoma, “4” is used when the severity has not yet been determined because the patient cannot take a visual field test or it is  not reliable.

Laterality is defined in the seventh character extension  by the following convention: “1” equals right, “2” equal  left, “3” equals bilateral, and “0” or “9” is non-specified.  Exceptions for this convention are when coding for eyelids: “1” indicates the right upper lid, “2” right lower lid, “3” the right eye unspecified lid, “4” the left upper lid, “5” the left lower lid, “6” the left unspecified lid, and “9” is an  unspecified eye, unspecified lid.

Combination codes have been created to allow  practitioners to bundle what was previously three or four different ICD-9 codes. Now one code can be reported that gives information about three or four different conditions. The most significant example is when coding for diabetic retinal complications. The first question is whether the  diabetes is Type 1 or Type 2; the second question is what type retinopathy has been found; the third question is the stage; and the fourth question is whether macular edema  is present or not present. Once these questions have been answered, a single code can be found in Chapter 4 (Endocrine) to describe all 4 points.

It is obvious that there is no direct crosswalk from version 9 to version 10 codes. It is impossible to go from a very low level of specificity coding to a very high level of specificity, so therefore one code on ICD-9 can translate into hundreds of codes in version 10. 

There are many tools to assist practitioners and staff in  selecting ICD-10 codes. One of simplest to use is the  general equivalence mapping (GEM) software which is  a free download from the CMS website. Using general equivalence mapping functions to get you close to the final code saves time and allows you to finalize a code  using the ICD-10 book or other tools. 

Visit PEN’s website at for detailed instructions on how to get and use the  ICD-10 GEM file as well as links other useful tools to help you transition to ICD-10. 

By Dr. John A. McGreal, Jr.

Dr. McGreal is practice in St. Louis, Mo. and has delivered clinical seminars for 28 years. His coding and compliance programs began 18 years ago with Primary Eyecare  Network (PEN). Dr. McGreal may be reached at