Effects of ocular dimensions on IOP-related stress within the opticnerve head and posterior scleral shell

摘要

In glaucoma, retinal axons are damaged as they pass through theconnective tissue beams (the lamina cribrosa) which span the scleralcanal. We created a set of idealized finite element models (FEMs) of theposterior scleral shell of the human eye to study stresses within thelamina cribrosa and surrounding sclera. These models incorporate a rangeof human dimensions for scleral wall thickness (SWT), axial length (AL),and size and shape of the scleral canal. Stresses within the laminartissues of circular canals ranged from 48×IOP (intraocularpressure) to 163× IOP. In regions where laminar tissues insertedinto the surrounding scleral shell, stresses were highest on theanterior (inner) side of the laminar beams. For elliptically shapedcanals, the ratio of vertical to horizontal diameters had an effect onthe maximum laminar stress and maximum stress at the insertion zones,and on the distance from the canal where the sclera withstands increasedstresses. Decreasing SWT led to significant increases in laminar,insertion zone, and peripapillary scleral stress. Changes in AL of thehemisphere had little effect on stresses within the tissues