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Mechanics of a macular hole: formation and surgical closure
Author(s) -
PEDDADA R,
WEINBERG D
Publication year - 2009
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2009.462.x
Subject(s) - macular hole , perpendicular , deformation (meteorology) , vitreous membrane , retina , foveal , materials science , physics , optics , vitrectomy , retinal , visual acuity , ophthalmology , medicine , geometry , mathematics , composite material
Purpose To elucidate the mechanics of the formation and surgical closure of a macular hole. Methods A parafoveal insertion of vitreous is examined in relation to its effect on the fovea. A force vector analysis is performed to understand the stages of a macular hole formation. A viscoelastic mechanical model is introduced to interpret the time constant of closure of the hole in terms of the physical properties of retina and the surrounding viscous fluid. Results Macular hole develops due to a combination of a tangential (radially outward from the fovea) and perpendicular force components arising from the posterior hyaloid separation (insertion) close to the fovea. The perpendicular force leads to the anterior deformation of the fovea, and therefore in cysts and schisis ("cavitation")formation. The subsequent separation of the photoreceptors from the RPE is also a consequence of the same perpendicular force. The loss of contact with the RPE in the presence of a tangential force lowers the resistance to the radially outward deformation of the foveal tissue and eventual hole formation. The hole closure occurs due to the stored elastic energy of the retina. The relaxation of the fovea is slowed or prevented by the viscosity of the surrounding fluid. Therefore, the hole closure may occur as soon as a few hours or it may never occur depending on the residual fluid and its viscosity at the conclusion of the surgery. The contribution of ILM peeling is discussed. Conclusion Macular hole forms as a consequence of both tangential and perpendicular components of the vitreous traction. The hole closure is promoted by the elasticity of the retina, and retarded by the viscosity of the residual fluid in the foveal region.