Biomechanical Strain Responses in the Sclera, Choroid, and Retina in Glaucoma Patients After Intraocular Pressure Lowering

This study measured the strain response to intraocular pressure (IOP) change in the sclera, choroid, and retina of glaucoma patients whose optic nerve head region was imaged by optical coherence tomography (OCT) before and after IOP-lowering by laser suturelysis following trabeculectomy surgery. The strain response was calculated from digital volume correlation of the prior and after images. The strain response of the sclera, choroid, and retina were compared to those previously published for the anterior lamina cribrosa (ALC). Mean strains were lowest in the retina and highest in the prelaminar neural tissue (PLNT). Maximum principal and maximum shear strains were significantly increased with greater IOP decrease in all five eye regions. Maximum principal and maximum shear strains in the anterior lamina cribrosa and the sclera were significantly related (p = 0.0094). Strain in the radial direction was negative in the ALC and PLNT, but positive in the sclera (p = 0.017). In conclusion, the strain response of the sclera, choroid, and retina is related to the magnitude of IOP change and is smaller than those of the ALC. The strain response of the ALC and sclera are significantly related to each other.