• Written By: Alan S. Crandall, MD
    Glaucoma

    This article in the June/July issue of the Journal of Glaucoma investigates the use of OCT to measure the macular region in glaucoma patients. The results indicate that in addition to peripapillary retinal nerve fiber layer (ppRNFL) thickness, macular ganglion cell complex (mGCC) thickness in the macular area is a structural parameter that may be useful for detecting preperimetric glaucoma.

    It has been known for a long time that perimetry defects are not apparent early in glaucoma and therefore new technology is required to help with early diagnosis. While some forms of new technology are already used in research centers, OCT would be readily available to most general ophthalmologists.

    In the current study, the authors used spectral domain OCT (SD-OCT) to quantify the thickness of the mGCC, the macular total retina (mTR) and the ppRNFL in apparently normal visual hemifields of 50 patients (50 glaucomatous eyes) with localized visual field loss. They compared these measurements with 25 normal controls (25 eyes) matched for age, sex, and refractive errors. They also analyzed the relationship between the OCT parameters and retinal sensitivity parameters determined by standard automated perimetry (SAP) corresponding to each hemisphere.

    They found that mGCC thickness in the normal hemifield of the glaucomatous eyes was significantly less than in the normal eyes. In contrast, the total thickness of the macular retinas showed no significant difference between glaucomatous and normal eyes. In addition, the thicknesses of the mGCC and ppRNFL in the normal hemisphere of the glaucomatous eyes were significantly correlated with the total deviation in the visual field parameters of the corresponding area.

    These findings suggest that mGCC thickness is a sensitive structural parameter for detecting early functional abnormalities in glaucoma. Based on their analyses, the authors conclude that the reliability of this parameter for detecting early glaucoma is comparable with that of ppRNFL thickness, and this measurement is more sensitive than the entire macular retina thickness measurement.