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Re: Wang et al.: Acute peripapillary retinal pigment epithelium changes associated with acute intraocular pressure elevation (Ophthalmology 2015,122:2022-8)

      To the Editors:
      We read with great interest the study by Wang et al,
      • Wang Y.X.
      • Jiang R.
      • Wang N.L.
      • et al.
      Acute peripapillary retinal pigment epithelium changes associated with acute intraocular pressure elevation.
      in which folding and/or centrifugal sliding of the peripapillary retinal pigment epithelium (RPE) were observed in 95% of eyes suffering an acute increase in intraocular pressure (of >15 mmHg) after a dark room prone provocative test. These morphologic changes reversed after intraocular pressure reduction and were not observed in control eyes.
      These RPE features occurred at the end of the peripapillary Bruch's membrane and the authors hypothesize that centrifugal RPE movement may be caused by a push owing to a shift of neuroretinal tissue (thinning) from the optic nerve head.
      We propose an alternative explanation where RPE morphologic changes were related to the expansion of Bruch's membrane opening (BMO) based on the following assumptions. First, anterior optic canal wall expansion has been described previously in monkey eyes.
      • Bellezza A.J.
      • Rintalan C.J.
      • Thompson H.W.
      • et al.
      Anterior scleral canal geometry in pressurised (IOP 10) and nonpressurised (IOP 0) normal monkey eyes.
      Second, a recently proposed paradigm suggests that there are 2 components of intraocular pressure-induced deformation of the lamina cribrosa, one acting on the anterior lamina cribrosa surface contributing to the posterior displacement and another, which causes canal expansion and tautening or anterior lamina cribrosa movement.
      • Crawford Downs J.
      • Roberts M.D.
      • Sigal I.A.
      Glaucomatous cupping of the lamina cribrosa: a review of the evidence for active progressive remodeling as a mechanism.
      • Sigal I.A.
      • Wang B.
      • Strouthidis N.G.
      • et al.
      Recent advances in OCT imaging of the lamina cribrosa.
      Last, we recently found a significant enlargement of the BMO in 17 eyes during the acute episode of anterior ischemic optic neuropathy, followed by a significant BMO diameter shrinking at 2 months (P = 0.008) with no change in the contralateral healthy unaffected eyes. Shrinking of the BMO correlated with progressive thinning of the retinal nerve fiber layer at 2 months (ρSpearman = 0.750; P = 0.001). Based on this finding, we speculated that BMO enlargement was mainly owing to optic disc swelling that distended neural canal at onset, and reversed as edema reduced.

      Muñoz-Negrete FJ, Rebolleda G, García-Montesinos J, et al. Changes in lamina cribrosa and prelaminar tissue in anterior ischemic optic neuropathy. Paper presented at: EVER 2015 Congress, October 8, 2015; Nice, France.

      These findings suggest that the optic nerve head space is not as rigid as we might think and it may behave as a dynamic structure. Unfortunately, Wang's study lacked data about BMO diameter before and after the dark room prone provocative test. We would appreciate if the authors can give any information related to this topic. These data would be very helpful to better define associated factors and to correlate their RPE findings with changes in the diameter of the BMO.

      References

        • Wang Y.X.
        • Jiang R.
        • Wang N.L.
        • et al.
        Acute peripapillary retinal pigment epithelium changes associated with acute intraocular pressure elevation.
        Ophthalmology. 2015; 122: 2022-2028
        • Bellezza A.J.
        • Rintalan C.J.
        • Thompson H.W.
        • et al.
        Anterior scleral canal geometry in pressurised (IOP 10) and nonpressurised (IOP 0) normal monkey eyes.
        Br J Ophthalmol. 2003; 87: 1284-1290
        • Crawford Downs J.
        • Roberts M.D.
        • Sigal I.A.
        Glaucomatous cupping of the lamina cribrosa: a review of the evidence for active progressive remodeling as a mechanism.
        Exp Eye Res. 2011; 93: 133-140
        • Sigal I.A.
        • Wang B.
        • Strouthidis N.G.
        • et al.
        Recent advances in OCT imaging of the lamina cribrosa.
        Br J Ophthalmol. 2014; 98: ii34-ii39
      1. Muñoz-Negrete FJ, Rebolleda G, García-Montesinos J, et al. Changes in lamina cribrosa and prelaminar tissue in anterior ischemic optic neuropathy. Paper presented at: EVER 2015 Congress, October 8, 2015; Nice, France.

      Linked Article

      • Acute Peripapillary Retinal Pigment Epithelium Changes Associated with Acute Intraocular Pressure Elevation
        OphthalmologyVol. 122Issue 10
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          To assess changes in the peripapillary retinal pigment epithelium (RPE) in association with an acute intraocular pressure (IOP) elevation provoked by a dark room prone provocative test (DRPPT).
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      • Reply
        OphthalmologyVol. 123Issue 5
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          We thank Rebolleda et al for their interest in our study, who proposed that the morphologic changes of the retinal pigment epithelium (RPE) seen after an acute increase in intraocular pressure (IOP) may be related to a potential increase in IOP associated expansion of Bruch's membrane opening.1 As reported in another recent article, the increase in IOP observed in the dark room prone provocative test was associated with a widening and deepening of the optic cup, a decrease in neuroretinal rim width, and a thinning of the lamina cribrosa.
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