An examination of the baropathic nature of axial myopia

Abstract

An examination of how intraocular pressure distending forces on the posterior sclera are an important mechanism in the development and progression of axial myopia has been made. Papers were selected from the results of PubMed (143) and Science Direct (1,398) searches using the key word combinations of ‘axial myopia’ and ‘intraocular pressure’. The main points include that the sclera is exposed to distending forces at all levels of physiological and pathological intraocular pressure. Reversible axial elongation is a common physiological response to elevated intraocular pressure in healthy eyes but more so in myopic eyes. Key variables, which appear to determine pathological (non‐reversible) axial elongation include the thickness, rigidity and viscoelasticity of the posterior sclera and the associated increased susceptibility of it to distending forces. Intraocular pressure appears likely to have a greater role when it is above normal. Intraocular pressure elevations, which are not detected by clinical or experimental tonometry, may be significant contributors to axial elongation. Axial elongation can be pathological in myopic or myopically predisposed eyes, when elongation is not reversible. Axial elongation has also been associated with retinal defocus in both animals and humans, when thinning due to loss of scleral collagen and/or ground substance, which is driven by the retina, appears likely to be associated with increased scleral susceptibility to intraocular pressure. As myopia progresses, signs of retinal and choroidal stretching are an increasingly apparent consequence of the balloon‐like expansion of the posterior sclera in response to intraocular pressure. Avoidance or moderation of activities which are known to elevate intraocular pressure may improve the prognosis for patients with genetic and/or environmental predisposition to myopic progression and may be an important consideration, even when other myopic control measures are being used.

Eye rubbing type and prevalence including contact lens ‘removal‐relief’ rubbing

“…The suggestion that rubbing could contribute to the development of ‘crow's feet’ wrinkles might be helpful. It is unknown whether counselling to avoid rubbing is commonly provided in relation to other corneal diseases or surgery, which may be adversely affected by rubbing trauma or even in relation to baropathic diseases such as glaucoma and axial myopia . Hopefully rubbing avoidance counselling would be more successful for such applications than has been demonstrated in this study for patients with keratoconus.…”

“…Eye rubbing can be a relatively benign activity that occurs sporadically on waking, prior to sleep, as well as throughout the day in response to fatigue or some form of ocular itch or irritation; however, rubbing becomes abnormal and potentially harmful when it occurs too frequently, when it is performed too vigorously, when the duration of rubbing episodes are extended and/or when rubbing habits have been established (perennially or seasonally) over a long period of time . Rubbing has the potential to have pathological significance, if associated elevated intraocular pressure (IOP) contributes to the development or progression of keratoconus or other baropathic diseases, such as glaucoma or axial myopia . For example, rubbing has a strong association with keratoconus and apart from the role of genetic influences in predisposing some corneas to develop keratoconus, it is possible that epigenetic mechanisms can help explain a causal contribution of an environmental factor, such as eye rubbing .…”

A hypothesis that scleral contact lenses could elevate intraocular pressure

“…For example, IOP elevation may contribute to cone progression in keratoconus, acute corneal hydrops and other corneal thinning diseases. Progression of growth in axial length might be promoted by elevated IOP in myopia, with potentially more serious consequences in the case of myopic fundus pathology …”

Novel Anti‐Biofouling Soft Contact Lens: l‐Cysteine Conjugated Amphiphilic Conetworks via RAFT and Thiol–Ene Click Chemistry

“…In recent years, soft contact lenses as one of delicate ophthalmic instruments have been widely employed in visual defect correction . However, nearly 50% wearers are susceptible to some clinical symptoms, such as eye infections and dry eye, which are primarily caused by corneal cell short‐term hypoxia, protein adsorption on lens surface from tears, etc .…”

“…In recent years, soft contact lenses as one of delicate ophthalmic instruments have been widely employed in visual defect correction . However, nearly 50% wearers are susceptible to some clinical symptoms, such as eye infections and dry eye, which are primarily caused by corneal cell short‐term hypoxia, protein adsorption on lens surface from tears, etc . Therefore, in addition to mechanical properties, optical properties, surface hydrophilicity, and oxygen permeability, the resistance to nonspecific protein adsorption is required for the preparation of ideal contact lenses materials, especially the extended‐wear soft contact lenses.…”