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  • Changes in GCC Thickness and Microvasculature in POAG

    By Lynda Seminara
    Selected By: Stephen D. McLeod, MD
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    Journal Highlights

    Ophthalmology, August 2020

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    Research has shown that ocular blood flow impairment and decreased perfu­sion lead to neuronal damage, causing thinning of the circumpapillary retinal nerve fiber layer and ganglion cell complex (GCC). Moreover, reduced ocular perfusion has been detected in glaucomatous eyes. In a prospective longitudinal study, Hou et al. used optical coherence tomography angiog­raphy (OCTA) to detect and compare structural thinning and microvascular density changes over time in healthy, preperimetric, and glaucomatous eyes. Decreases in GCC and macular vessel density were detected in all groups. In eyes with primary open-angle glau­coma (POAG), the decline in macular vessel density occurred more quickly than the GCC thinning.

    The authors recruited participants from the Diagnostic Innovations in Glaucoma Study, and categorized the eyes as healthy (no evidence of glauco­matous damage), preperimetric (suspi­cious signs of glaucoma, no repeatable measured visual field damage), or POAG (repeated verifiable visual field damage). POAG severity was graded at study start and reflected the extent of visual field damage. All patients had full ophthalmologic exams at baseline and six-month intervals, for a mean of at least two years. Using predefined proto­cols, OCTA and spectral-domain OCT scans were performed to measure GCC thinning and macular vascular density. Poor quality images were excluded.

    The final analysis included 139 eyes (23 healthy, 36 preperimetric, 80 POAG). Throughout follow-up, all groups exhibited significant (p < .05) GCC thinning and decreased macular vascular density. The decrease in vascu­lar density was greatest in POAG eyes, and the rate of decrease outpaced that of GCC thinning in these eyes. The rate of macular vascular density decline correlated strongly with glaucoma severity at baseline. Relative rates of GCC thinning and macular vascular density decline coincided with the range of glaucoma severity; quick rates of vascular density loss were common in severe disease. Intraocular pressure (IOP) during follow-up significantly influenced the rate of GCC thinning in all groups (higher IOP = faster thinning) but did not seem related to vessel density decline. These results are consistent with others showing no strong link between IOP and vascular density decline.

    The authors suggest that OCTA may be useful to monitor glaucoma pro­gression and identify factors other than IOP that may contribute to glaucoma. OCTA measurement of macular vessel density may be especially helpful to monitor progression of advanced disease. Further research with larger samples is warranted. (Also see related commentary by Ji Eun Lee, MD, in the same issue.)

    The original article can be found here.