Relief of Cystoid Macular Edema-Induced Focal Axonal Compression with Anti-Vascular Endothelial Growth Factor Treatment

Abstract

To evaluate the mechanical compression of retinal nerve fiber layer (RNFL) by intraretinal cysts in macular edema and its relief with anti-vascular endothelial growth factor (anti-VEGF) treatment. Methods: Optical coherence tomography scans were used to measure RNFL thickness and reflectance at seven preselected points at and around the peak of the edema before and after anti-VEGF treatment in 10 patients (11 eyes) with branch retina vein occlusion (BRVO) and diabetic macular edema (DME). Scans through nonedematous retina and from the fellow eyes were taken as controls. Correlations were sought between the changes in retinal and RNFL thickness, RNFL reflectance, and the size of the intraretinal cysts. Results: Postinjection RNFL thickness decreased significantly only at peak point of the edema (18.1 ± 2.7 vs. 13.8 ± 1.2 μm; P = 0.038), at its nasal edge (20.1 ± 2.7 vs. 15.5 ± 1.4 μm; P = 0.026), and 500 μm away from its nasal border (35.7 ± 6.0 vs. 20.1 ± 2.7 μm; P = 0.006) suggesting focal stagnation of the axoplasmic flow owing to compression at its peak point. Significant postinjection decreases in RNFL reflectivity were also noted at peak point of the cyst (164.9 ± 10.3 vs. 141.5 ± 12.6 arbitrary units [AU]; P = 0.037), at its nasal edge (166.8 ± 7.8 vs. 135.1 ± 10.2 AU; P = 0.02), and 1500 μm away from temporal edge (160.2 ± 6.2 vs. 141.1 ± 6.4 AU; P = 0.022). Cyst proximity to RNFL (D 50 = 50 μm) was the only determinant significantly affecting the magnitude of the RNFL thickness change after anti-VEGF treatment (P = 0.001). Conclusions: Intraretinal cysts due to BRVO and DME locally compress overlying axons and induce anatomic changes suggestive of axoplasmic stagnation. This compression can be relieved with anti-VEGF treatment.

Anatomical and functional correlates of cystic macular edema in retinitis pigmentosa

“…This method reflects any CME-induced focal changes in retinal nerve fiber layer thickness, which can be missed by studying the nerve fiber layer thickness only at points along the perimeter of a peripapillary circle. The strong correlations we observed between RNFLA, the cyst area, and visual acuity suggest that intraretinal cysts further deteriorate a patient's vision by compressing the retinal nerve fiber layer and leading to axonal stasis, similar to what we reported in diabetic macular edema and retinal vein occlusion [32]. Axonal compression can also be the underlying cause of electrophysiological dysfunction [33] and histologic evidence of ganglion cell death [34,35] in retinitis pigmentosa with CME.…”

“…Best-fit curves indicate that a 3.5 times increase in the RNFLA can result in an average of 15 letters of vision loss. (Fig 4B ) We previously used a mathematical model to estimate the pressure exerted by intraretinal cysts on surrounding retinal tissue [32]. Applying the same model to our current cohort, we may estimate that retinal cysts with an average area of 0.14 ± 0.18 mm 2 and a radius of 0.21 ± 0.24 mm may exert a force on the surrounding retinal tissue comparable to an increase in intraocular pressure up to 77 mmHg.…”

An overview of peripapillary hyperreflective ovoid mass-like structures

“…PHOMS have been reported for in various retinal pathologies such as choroidal neovascularization, dome-shaped maculopathy, retinal vascular occlusions, and white dot syndromes [25,31,33]. As macular edema has been demonstrated to be associated with PHOMS resulting from axonal stasis, this may be the mechanism through which PHOMS developed in patients with choroidal neovascularization and dome-shaped maculopathy [40]. Retinal vascular occlusions may also result in axoplasmic stasis due to retinal and optic nerve head edema.…”