Corneal modifications in high myopic patients are still under debate some studies reported modifications in corneal biomechanical properties in high myopic patients, such as lower hysteresis. This kind of modification can contribute to the development of many complications that will be discussed in this chapter. These modifications lead to the fact that in highly myopic eyes, sclera is thinner in the part that goes posterior to the equator, while the anterior part does not show any significative difference with normal eyes.
In highly myopic eyes, also a remodeling of the extracellular matrix is observed during the extension of the eyeball, even if its mechanisms are not fully understood. The reason can be searched in the alteration of its ultrastructure (which is more layered and lamellar compared to the normal sclera), in thinning and decreased diameter of the collagen fibers, and also in configuration and conformation of the collagen fibrils. In highly myopic eyes, these properties are altered with tensile strength reduced and augmented elasticity especially at the posterior pole of the globe. Normal sclera has also well-known tensile and elastic properties. In normal nonelongated eyes, scleral thickness decreases from the limbus to the equator, then increasing again to the posterior part of the eye. Sclera is the most external layer of the eye. Many modifications in normal eye anatomy and structure occur in high myopic patients. We will focus on visual rehabilitation interventions, such as visual biofeedback and visual aids that in many cases are the only chance that the ophthalmologist has in order to help patients suffering from pathologic myopia to use at their maximum their residual vision. Many treatments are available for pathologic myopia complications depending on their type, such as vascular endothelial growth factor (anti-VEGF) injections and surgery. For educational purposes, in this chapter, complications of pathologic myopia will be divided into anterior (when structures external to the globe or anterior to the ora serrata are involved, such as motility disturbances and cataract) and posterior (when structures posterior to the ora serrata are involved, such as lacquer cracks, chorioretinal atrophy, Fuchs maculopathy, myopic choroidal neovascularization, and retinal detachment). Pathologic myopia is one of the major causes of blindness, and it represents a serious issue, since incidence of myopia and high myopia is constantly rising. When high myopia is able to decrease best corrected visual acuity (BCVA) due to its complications, it is called pathologic myopia. High myopia, defined as refractive error of at least −6.00D or an axial length of 26.5 mm or more, can induce many modifications in eye’s anatomy that can lead to complications.
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