Histological changes of high axial myopia

Abstract

To describe pathological changes in the anatomy of highly myopic (axially elongated) eyes, enucleated globes were examined by light microscopy and ocular structures were measured histomorphometrically. These studies revealed that highly axially myopic eyes show continuous thinning of the sclera starting at or behind the equator with a maximal thinning at the posterior pole; a profound thinning of the choroid decreasing from B250 to o10 mm in extreme axial myopia, secondary macular defects in the Bruch's membrane associated with a complete loss of retinal pigment epithelium and choriocapillaris, and retinal photoreceptors; a Bruch's membrane of normal thickness in contrast to the profound thinning of the choroid and the sclera; an up to 10-fold elongation and thinning of the peripapillary scleral flange as anterior roof of the orbital cerebrospinal fluid space, and subsequently a retrobulbar extension of the cerebrospinal fluid space; an increased distance of the peripapillary arterial circle of Zinn-Haller to the optic disc border; an elongation and thinning of the lamina cribrosa with a subsequently decreased distance between the intraocular pressure compartment and the retrobulbar orbital cerebrospinal fluid pressure compartment; an increasing exposure of the peripheral posterior lamina cribrosa surface to the cerebrospinal fluid space, no longer buffered by the solid optic nerve tissue; and the development and enlargement of parapapillary gamma zone, in contrast to a myopia-independent parapapillary beta zone. These anatomical changes may be associated with high axial myopia-related complications such as an increased susceptibility of glaucomatous optic neuropathy and myopic retinopathy.

Lamina cribrosa depth according to the level of axial length in normal and glaucomatous eyes

“…Hence, posterior displacement of the LC is a key feature of glaucomatous ONH changes. Histologic evaluation showed that the LC was thinner in highly myopic eyes [7,8], suggesting that axial elongation of the eyeball can induce thinning of the LC. Thinner LC may be more vulnerable to glaucomatous damage at a similar level of IOP, and a thin LC may be predictive of glaucoma progression [9][10][11].…”

Advances of optical coherence tomography in myopia and pathologic myopia

“…Jonas et al recently reviewed the histological changes of high-axial myopia. 4 In brief, there is profound thinning of the choroid associated with the loss of choriocapillaris and RPE. The thinning of the sclera starts at or behind the equator with maximal thinning at the posterior pole, and the elongated peripapillary scleral flange (defined as the canal between the optic nerve border and the point where dura mater merges with the sclera) and lamina cribrosa is stretched thin with subsequent decreased distance between the retrobulbar cerebrospinal fluid space with the intraocular pressure compartment.…”

Controversial opinion: evaluation of EGR1 and LAMA2 loci for high myopia in Chinese populations

“…We selected to test the LAMA2 gene based on two justifications: first, its biological function role in posterior sclera remolding, which is a crucial process for myopisation (Jonas and Xu, 2014;Harper and Summers, 2015); second, recent GWAS from multiple center data indicated a strong association of the SNP markers in the LAMA2 gene region with myopia (Cheng et al, 2013;Kiefer et al, 2013;Verhoeven et al, 2013). Despite the robust data from previous works regarding functional and genomic research, we did not find the association of the adjacent selected SNPs in the LAMA2 gene region with high myopia.…”

“…It is thought to mediate the attachment, migration, and organization of cells into tissues during embryonic development (Schéele et al, 2007). The LAMA2 gene encodes the Laminin α2 protein, which is the subunit of Laminin and plays an important role in the connection of sclera collagen fiber (Jonas and Xu, 2014). Extracellular matrix remolding of sclera is the major histological feature in eye growth or myopia (Harper and Summers, 2015).…”