ICD-10-CM for Glaucomatologists

Practices face major changes.

By Cynthia Mattox, MD

The implementation of ICD-10 was set in motion, not by the Affordable Care Act, but by the Health Insurance Portability and Accountability Act of 1996. The goal was to create a system that improves and develops methods for the electronic transmission of health-related information. The Centers for Disease Control’s National Center for Health Statistics, along with stakeholders, developed the ICD-10-CM code sets that were adopted by the Secretary of Health and Human Services. Final rule making in 2009, and a subsequent delay by the Secretary, set an implementation date of October 1, 2014, despite numerous medical societies’ pleas to halt the endeavor.

ICD-10 exponentially expands the codes we physicians use for diagnoses. The entirety of ICD-9 encompasses about 14,000 codes, whereas ICD-10 is estimated to include more than 69,000. The expansion incorporates digits used for designations important to ophthalmology such as laterality and staging that were absent in ICD-9. The sections on trauma and tumors are also far larger.

In ICD-10, codes are divided into chapters, and codes will have three to seven digits, alpha and numeric. New in ICD-10 is the placeholder character “X,” used, for example, when a seventh digit is required but a sixth digit does not exist.


While the Eye chapter “H” roughly mimics the organization of ICD-9, now, some of the common eye-related codes such as diabetic eye disease are located outside the Eye chapter, while other codes within the chapter need modifying codes described outside that section. The basic coding conventions that we have always used still apply: we should code diagnoses to the highest degree of accuracy, and if there are additional digits available, we should use them. If a definitive diagnosis does not exist, then we should code a sign or symptom code, but we should not routinely add these codes to elaborate on a diagnosis.

Even in ICD-9 coding, there were two sections within the code set: an alphabetical index and the tabular list. In ICD-10, especially for less familiar diagnosis codes, our best strategy is first to locate the diagnosis in the alphabetical index and then verify the code in the tabular list. Only full-code digits such as laterality and staging are listed in the tabular list. A code will be invalid if it is not coded to the full number of digits required. Although designations for additional digits vary in definition and position from code to code, no matter where the laterality digit resides (in the codes that require it), 1 is right, 2 is left, 3 is bilateral, and “unspecified” (ie, not recorded in the medical record) is either 0 or 9.


The diseases of the eye and adnexa are listed in chapter 7. The glaucoma section codes begin with H40 “glaucoma” or H42 “glaucoma in diseases classified elsewhere.”


Most, but not all, glaucoma codes incorporate both laterality and stage of disease. Laterality may be found in either the fifth or sixth digit position, while the staging code is always the seventh digit. Again, if there is no sixth digit in the code, then “X” is to be used as a placeholder.

Inexplicably, this first version of ICD-10 does not incorporate laterality for five code sections:

  1. primary open-angle glaucoma H40.11-

  2. unspecified open-angle glaucoma H40.10-

  3. unspecified primary angle-closure glaucoma H40.20-

  4. other specified glaucoma H40.89

  5. unspecified glaucoma H40.9

Because all other codes in the glaucoma section require laterality digits, the discrepancy is quite confusing and will interfere with data analysis for future research and benchmarking work. The discrepancy was brought to the attention of the ICD-CM committee several times during the past few years, and the 2015 version is supposed to incorporate laterality consistently throughout the glaucoma codes.

The glaucoma staging code digits are to use the same definitions as the add-on codes in ICD-9 (see Glaucoma Staging Codes). In ICD-9, staging was designated for the more severely affected eye. In ICD-10, if laterality is included in the code, we will use the seventh digit to indicate the stage for each eye. In other words, if the stage differs for the patient’s two eyes, we will use two codes, but if the stage is the same in both eyes, we will use the one bilateral code. If laterality is not required (eg, primary open-angle glaucoma), we will continue to code the more severely affected eye. As an example, if the patient has different stages of chronic angle-closure glaucoma in his or her eyes, coding would be as follows:

  • H40.221(right eye)1(mild stage) = H40.2211
  • H40.222(left eye)3(severe stage) = H40.2223

In contrast, if both eyes have moderate glaucoma, the coding would be H40.223(bilateral)2(moderate stage) = H40.2232.

(See Specific Diagnoses Located Elsewhere or Requiring Additional Codes Outside of the Glaucoma Section and Other Discrepancies.)


This article suggests how enormous a change ICD-10 represents for our practices. The American Academy of Ophthalmology and other medical societies are developing resources to help us with the transition. It is imperative that our practices and electronic health record vendors be prepared and that we plan and train for the new system prior to the go-live date of October 1, 2014.

Cynthia Mattox, MD, is vice chair and associate professor of ophthalmology, Department of Ophthalmology, Tufts University School of Medicine, New England Eye Center, Boston. Dr. Mattox may be reached at (617) 636-8108; cmattox@tuftsmedicalcenter.org.


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