Unraveling the Secrets of High Myopia: Changes in Eye Structure
Authors: Markov, P.P., Eliasy, A., Pijanka, J.K., Htoon, H.M., Paterson, N.G., Sorensen, T., Elsheikh, A., Girard, M.J. and Boote, C.
Journal: Molecular vision
Publication Date: Dec 2018
WAXS polar plot vector maps comparing one non-myopic (A–B) and two highly myopic (C–F) posterior scleras. A: Full map of non-myopic specimen N4. B: 30 × 30 vector plot zoom of N4. C: Full map of highly myopic specimen HM1. D: 30 × 30 vector plot zoom of HM1. E: Full map of highly myopic specimen HM2. F: 30 × 30 vector plot zoom of HM2. G: Map of myopic specimen HM3. The zoomed regions are denoted by a red square on the full maps. The peripapillary scleral region is shown bounded by black lines, in which largely circumferential collagen alignment is observed. Arrows: interruption of the circumferential collagen orientation (normally limited to the SN quadrant in non-myopic eyes) is more extensive in highly myopic specimens. S, N, I, and T denote the superior, nasal, inferior, and temporal directions, respectively.
Summary:
Myopia, or nearsightedness, is the most common visual disorder and affects about a quarter of the world's population. High myopia, a severe form of the condition, affects those with a refractive error of more than 6 diopters. This group is at an increased risk of developing serious complications, such as glaucoma, cataracts, macular degeneration, and retinal detachment. As the prevalence of myopia continues to rise, understanding its causes and consequences has become a global concern.
Our research aimed to investigate any changes in the structure of the posterior sclera, the white fibrous tissue that makes up most of the eye's outer layer, in individuals with high myopia. To do this, we used a technique called wide-angle X-ray scattering (WAXS) to map collagen orientation in the posterior sclera of both non-myopic and highly myopic human eyes.
We found that non-myopic eyes displayed a consistent and well-conserved microstructure, including strong collagen alignment in specific regions of the sclera. However, all three highly myopic specimens showed notable alterations in the peripapillary sclera, a region around the optic nerve head. Specifically, these eyes exhibited a partial loss of normal circumferential collagen alignment and redistribution of the collagen anisotropic proportion, a measure of the alignment of collagen fibers within the tissue.
These changes in the eye structure could be the result of the remodelling of the posterior sclera during the axial lengthening that occurs in myopia. Alternatively, they may represent a mechanical adaptation to increased tissue stresses induced by fluid pressure or eye movements, which could be exacerbated in enlarged eyes. Further research is required to determine the exact cause of these structural changes.
Understanding the changes in eye structure that occur in high myopia is crucial for developing more effective treatments and prevention strategies for this condition. Our findings contribute to a better understanding of the biomechanical changes in the eye in high myopia, which can inform future modelling studies and help guide clinical interventions.