Macula Ganglion Cell Count (GCC) Measurements in Myopic Patients
Illustration that demonstrates the inferior vulnerability zone consists of macular fibers,
and the superior vulnerability zone does not consist of macular fibers.10
The analysis of the inner retinal thickness in the macula is complementary to the RNFL scan and provides useful diagnostic information in glaucoma detection. The macular ganglion cell complex (GCC) measures the thickness of the inner retinal layers that are involved in glaucomatous damage. Glaucoma is a progressive condition that affects the RNFL or the axons of ganglion cells. The GCC measurement detects thinning of the RNFL and GCL where the cell bodies are located. In some cases of glaucoma where early damage is seen in the macular region first, taking only RNFL measurements would fail to detect disease. This is highlighted by the work of Don Hood and the vulnerability zones. Due to the inferior displacement of the macular compared to the optic nerve head, the inferior vulnerability zone of the optic nerve head consists of macular fibers. Macular measurements may particularly be important for myopic patients as RNFL measurements may be complicated due to tilting of the optic nerve and staphylomas. In some studies, macular measurements were shown to have a greater diagnostic power than RNFL scans.11 Macular measurements should be performed in all glaucoma suspects and particularly in myopic patients in the absence of macular pathology.