In Reply We thank Shinojima and colleagues for their interest in our study1 on exercise and swimming goggles in a model of spaceflight associated neuro-ocular syndrome (SANS). Spaceflight provokes increases in both intracranial pressure (ICP) and intraocular pressure (IOP).2 However, there is a greater increase in ICP relative to IOP, which results in an IOP-ICP mismatch and an anteriorly directed translaminar pressure gradient across the lamina cribrosa (LC).2 A negative translaminar pressure gradient is associated with adverse ocular changes2; accordingly, countermeasures that normalize this are of major importance in protecting the health of astronauts. To date, most SANS countermeasures have focused on reversing the spaceflight-associated fluid shifts to lower ICP, with tools such as a lower-body negative-pressure device.2 Our findings1 indicated that slightly increasing IOP with an inexpensive and convenient countermeasure, such as swimming goggles, could also normalize the translaminar pressure gradient. In addition, goggles may be a relatively safe intervention; the increase in IOP with goggles is small (approximately 3 mm Hg),1 and goggles are worn by competitive swimmers for hours daily without an increased prevalence of glaucoma.3
Scott JM, Tucker WJ, Haykowsky MJ. Lamina Cribrosa Pore Diameter and Spaceflight-Associated Neuro-ocular Syndrome—Reply. JAMA Ophthalmol. 2019;137(11):1331. doi:10.1001/jamaophthalmol.2019.3322
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