Gonioscopic grading

In addition to IOP-related codes (see separate thread), another area of discussion from the CRG meeting on 3/23/23 was the identification of gaps in gonioscopic grading. Some felt that these exam areas are not populated consistently, but it sounds like in the UK there is fairly consistent documentation, and that standardized coding in this area would be high-yield. Currently, SNOMED has codes such as "narrow angle of anterior chamber", "wide open angle", and "moderate open angle", but there are not codes to indicate exact grading specification or quadrant of observation. 

Elaine Wooler asked to see what gonioscopic grading typically looks like in the EHR, so I have copied over the interface from Epic Kaleidoscope as an example: 

Open

For each eye (right and left), there are 4 boxes/fields corresponding to each quadrant: superior, nasal, temporal, and inferior. The "method" field allows the clinician to indicate the method of gonioscopic grading used. 

Laterality: Similar to IOP, these would apply to each eye (left eye, right eye). In a further level of specification beyond laterality, each gonioscopic observation has a quadrant designation. Thus, you would have observations for right eye superior, right eye nasal, right eye temporal, and right eye inferior, and similar for left eye. 

Associated Units: None. There is not really a standard "unit" of measurement for these gradings (some assessment of degrees occurs, but typically this will correlate into a grading - see "range of observed values" section below). 

Method of gonioscopic grading: Here are some examples of gonioscopic grading classification systems: 

• Spaeth

• Scheie

• Shaffer

• Van Herick

• Non-codified (just reporting what angle structures are visible) 

During our discussion at the meeting on 3/23, it was felt that some of these may be quite complex (particularly Spaeth). The Spaeth classification system has several components that can be combined together, resulting in a large list of possibile gradings. It was felt that perhaps we should start with codifying the simpler classification systems first, and then if there is user demand for Spaeth, we can deal with those at a later time. 

Range of Observed Values: I am listing the range of observed values below for a few of the classification systems above. Others, please correct if I have made any mistakes. Some references: https://www.aao.org/education/disease-review/gonioscopic-grading-systems

https://www.semanticscholar.org/paper/The-Spaeth-Gonioscopic-Grading-System-Assessing-the-Marsh-Cantor/39bf462444a6f4bc205ea40c6d0f518f6c90f217

• Scheie: Wide (Wide open), I (Slightly narrowed), II (Apex not visible), III (Posterior half of trabeculum not visible), IV (None of angle visible) 

• Shaffer: Grade 4 (45 degree to 35 degree angle; Wide open); Grade 3 (35 degree to 20 degree angle; Wide open), Grade 2 (20 degree angle, Narrow), Grade 1 (less than or equal to 10 degree angle, Extremely narrow), Slit (0 degree angle, narrowed to slit) 

• Van Herick: Grade 4 (Open), Grade 3 (Open), Grade 2 (Narrow), Grade 1 (Angle Closure likely)

• Non-codified (just reporting what angle structures are visible): none, Schwalbe's line, anterior trabecular meshwork, posterior trabecular meshwork, scleral spur, ciliary body band

An additional consideration is grading angle pigmentation, which is codified in Scheie. We did not specifically discuss this in the meeting and I'm not sure how often this is documented or contained in structured form in EHRs, but including here to try to be comprehensive.

• Scheie angle pigmentation: None, I, II, III, IV  (larger numbers indicating greater pigmentation)

Again, Elaine Wooler let me know if any additional info is needed, and thanks everyone for you input on this!

I agree - this is complex!  Perhaps one high priority that is pragmatic:  is an angle is occludable or not?  I.e. 180+ degrees of apposition with posterior trabecular meshwork?  I believe that was the definition used in the EAGLE and ZAP trials (though we should check!).  PAS also important.  Also new vessels and level of pigment may be relevant.  Which quadrant and extent could be post-coordinated?  Just thoughts....

Agree that these elements are important, but I think there is already some level of representation in SNOMED. For example, there is an existing SNOMED code called "occludable anterior chamber of eye" (https://athena.ohdsi.org/search-terms/terms/4227977).  There are also several synechiae-related codes in SNOMED, including "peripheral anterior synechiae" (https://athena.ohdsi.org/search-terms/terms/441016). There are also some related to new vessels ("rubeosis iridis", "neovascularization of the iris and/or ciliary body", "proliferative diabetic retinopathy with iris neovascularization due to diabetes mellitus"). So it looks like these have some level of representation/codification in SNOMED already, but the specific gonioscopic gradings do not.