How to ‘define’ childhood glaucoma

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The Childhood Glaucoma Research Network has developed definitions and a classification system for childhood glaucoma.

By Cheryl Guttman Krader; Reviewed by Allen Dale Beck, MD

Atlanta-A new system of classification for childhood glaucoma provides a framework for future glaucoma studies and coding, but can be modified in the future based on findings from new research, said Allen Dale Beck, MD.

The classification system was developed by a multinational committee of members of the Childhood Glaucoma Research Network (CGRN) and revised by the World Glaucoma Association. Details can be seen on the CGRN website (http://www.gl-foundation.org).

Primary and secondary categories

The classification is based on standardized definitions of childhood, glaucoma, and glaucoma suspect, and it is a concise system that divides childhood glaucoma into primary and secondary categories.

Primary childhood glaucoma is further subdivided into primary congenital glaucoma and juvenile open-angle glaucoma.

The category of secondary childhood glaucoma includes four subgroups:

• Glaucoma associated with non-acquired ocular anomalies.

• Glaucoma associated with non-acquired systemic disease or syndrome.

• Glaucoma associated with acquired conditions.

• Glaucoma following cataract surgery.

“Previously, we used a very confusing and overlapping nomenclature when discussing childhood glaucoma,” said Dr. Beck, professor, Emory University, Atlanta, and chairman of the classification committee. “However, unless we are speaking the same language, we cannot talk about these children in the same way, and we cannot study them properly.”

The CGRN is a group of more than 100 pediatric ophthalmologists and glaucoma specialists from six continents. It was started in 2011 by Alana Grajewski, MD, Department of Ophthalmology, University of Minnesota, Minneapolis, and is supported by the Minnesota Lions Fund to Prevent Blindness in Infants and Children and the GL Foundation for Children with Glaucoma.

Once the classification committee developed a system, it was subjected to validation testing using an online survey asking CGRN members to classify 7 test cases. The survey had a 42% response rate, and a majority of responses for each case were consistent with the intended classification.

After discussion of the results, the classification committee approved the system as tested. It then underwent further revision and vetting by a consensus committee of the World Glaucoma Association in July 2013.

Definitions and criteria

The system uses national criteria to define childhood, which is considered anyone <18 years of age in the United States, but ≤16 years in Europe.

The definition of glaucoma was expanded from the Infant Aphakia Treatment Study definition and requires IOP >21 mm Hg, plus at least one of the following:

• Optic disc change.

• Corneal findings, such as Haab striae or edema.

• Ocular enlargement by progressive myopia or axial length.

• Visual field defect consistent with glaucoma.

A “glaucoma suspect” was defined as having either IOP >21 mm Hg on two separate occasions or suspicious optic disc, suspicious visual field, or increased corneal diameter or axial length with a normal IOP.

Discussing the criteria for the various glaucoma types, Dr. Beck said that the primary congenital glaucoma (PCG) is a “lumper type of classification as opposed to a splitter.” It includes eyes that meet the glaucoma definition and have isolated angle anomalies with or without mild congenital iris anomalies.

Eyes meeting these criteria are then subcategorized into three groups based on age of onset:

• Neonatal or newborn (onset age 0 to 1 month).

• Infantile (onset >1 to 24 months).

• Late onset or late recognized (onset >2 years).

“Spontaneously arrested cases with normal IOP but typical signs of primary congenital glaucoma are also classified as PCG,” Dr. Beck said.

Juvenile open-angle glaucoma encompasses eyes with open angle that meet the glaucoma definition and have no evidence of ocular enlargement or other features that would place them in another category.

The definitions for two of the secondary glaucomas-glaucoma associated with non-acquired ocular anomalies and glaucoma associated with non-acquired systemic disease or syndrome-are self-explanatory.

Dr. Beck referred to glaucoma associated with an acquired condition as a “wastebasket category.” It includes eyes that meet the glaucoma definition after recognition of the acquired condition that led to glaucoma, such as trauma, uveitis, or infection. Gonioscopy results should also be noted.

The secondary glaucoma category of glaucoma following cataract surgery replaces the often-used term “aphakic glaucoma.” It includes children with acquired cataract known syndromes-Lowe’s syndrome and congenital rubella-if the glaucoma develops after cataract surgery and also differentiates between eyes with open and closed angles based on gonioscopy.

“Angle status can be important in determining treatment,” Dr. Beck said.

As appropriate with the secondary glaucoma subgroups, details of the ocular anomaly, systemic syndrome or disease, acquired condition, and age of cataract onset and surgery should be recorded.

Allen Dale Beck, MD

E: abeck@emory.edu

Dr. Beck has received travel support and an honorarium from Merck.