Four Questions for Every Clinician Diagnosing and Monitoring Glaucoma

Abstract

We pose 4 questions for the clinician diagnosing and monitoring glaucoma, and supply evidence-based answers. The first question is: "When do you perform a 10-2 (2-degree grid) visual field (VF) test?" We argue the best answer is: anyone you would do, or have done, a 24-2 (6-degree grid) VF on should have both a 24-2 and a 10-2 VF within the first 2 visits. Second, "When do you perform an optical coherence tomography (OCT) scan of the macula?" We argue that, if you are performing an OCT test, then it should include both the macula and disc, either as a single scan or as 2 scans, one centered on the macula and the other on the disc. Third, "How do you know if the VF and OCT tests agree?" The poor answer is, "I use summary statistics such as 24-2 mean deviation and global or quadrant average of retinal nerve fiber layer (RNFL) thickness." It is much better to topographically compare abnormal regions on the OCT to abnormal regions on the VF. Finally, the fourth question is: "When do you look at OCT images?" We argue that, at a minimum, the clinician should be directly examining an image of the circumpapillary RNFL, and this image should be sufficiently large and with sufficient resolution so that local damage can be seen, and the segmentation evaluated.

An Automated Method for Assessing Topographical Structure–Function Agreement in Abnormal Glaucomatous Regions

“…First, the sample size of 53 glaucomatous and 45 healthy control eyes, involved in the development and evaluation of the new method, is relatively small. Nonetheless, the results of this study agree with a previous qualitative analysis of a different data set of a similar nature, 2 and the results from the validation group of 101 eyes showed excellent agreement. The age difference between the two groups (i.e., DG and H eyes) is also not desirable, mainly in diagnostic studies, although ours is not.…”

“…Using a reference database from the OCT device manufacturers (data provided by Topcon, Inc.), we generated age-corrected deviation/probability maps, as previously described and employed in an established OCT widefield report. 6 The reference database included eyes with (1) normal 24-2 VFs (abnormal defined as Glaucoma Hemifield Test "outside normal limits" and/or Pattern Standard Deviation (PSD) <5%), (2) no eye pathology, and (3) intraocular pressure lower than 21 mm Hg. The The RGC+ and RNFL probability plots, respectively, with the 24-2 and 10-2 locations superimposed as large (24-2) and small (10-2) circles.…”

“…Hood and De Moraes 2 have recently suggested, through the results of a pilot study, that a topographic comparison of structural and functional defects shows good agreement, which significantly increases if both 24-2 and 10-2 VF tests were performed and if structural (i.e., OCT) information from both the RGC and RNFL layers was included. However, their report carried some limitations, which included the qualitative, and therefore subjective, aspect of their analysis, as well as the retrospective nature of their study and its related biases (e.g., selection bias).…”

Structure-Function Agreement Is Better Than Commonly Thought in Eyes With Early Glaucoma

“…In any case, if structural damage does precede functional damage, then a clinical comparison between a VF (functional) test and an OCT (structural) test may be of questionable value, at least in the case of early damage. However, we5,7 and others6,8 have argued that the extent to which structural and functional glaucomatous damage agree depends upon various factors, such as the particular test and test measures used, and the baseline conditions for a particular patient. In addition, structural damage, as measured by OCT retinal nerve fiber layer (RNFL) thickness, and functional damage, as measured with VFs, parallel each other, often in a linear fashion 5,9.…”

editorial

“…Chen et al showed that if two points were added to the superior macular region of the Humphrey 24-2 pattern, it increased the number of abnormal locations G in individuals with glaucoma 10 . Thus, clinicians should be aware of the limitations of the 24-2 in the presence of suspicious discs and "normal" visual fields 11 .…”