Inferior Macular Damage in Glaucoma: Its Relationship to Retinal Nerve Fiber Layer Defect in Macular Vulnerability Zone

Abstract

Purpose of the Study: 

The purpose of the study was to investigate the prevalence of abnormal thinning of the inferior macular ganglion cell-inner plexiform layer (mGCIPL) in glaucoma and to understand its relationship to abnormal regions of the peripapillary retinal nerve fiber layer (pRNFL), including the macular vulnerability zone (MVZ).

Patients and Methods: 

We evaluated 186 eyes (186 patients) with glaucoma. An integrated deviation map was merged by superimposition of mGCIPL and pRNFL deviation maps (from a spectral-domain optical coherence tomography) onto RNFL photography as aligned by Photoshop software based on vascular landmarks. The peripapillary area was divided into 2 locations according to a previously suggested schematic model: (1) the MVZ; and (2) the inferoinferior portion.

Results: 

The key findings of the topographic analysis of mGCIPL and pRNFL deviation maps were as follows: (1) 145 of 186 eyes showed inferior mGCIPL loss; (2) if a defect existed in the MVZ of the pRNFL (63 eyes), there was also an inferior mGCIPL defect; (3) however, the other 82 eyes with inferior mGCIPL abnormalities showed an abnormal mGCIPL without a corresponding pRNFL defect in the MVZ.

Conclusions: 

There was no single case of pRNFL defect in the MVZ without inferior mGCIPL loss. However, there were a few cases of inferior mGCIPL loss without pRNFL defect in the MVZ. These findings signify that detection of inferior mGCIPL loss might be earlier than that of pRNFL defect in the MVZ. Therefore, pRNFL analysis of the optical coherence tomography disc cube scan alone is insufficient for detection of early-stage glaucomatous damage.