Springe zum Inhalttxcc.netMenü und WidgetsSuche nach:PagesData protection statementHow do Glasses Work?How do Glasses Work?The eyes are complex organs that must work together to respond to light and produce clear vision. In the presence of light, an individual is able to see because light reflects of objects and enters the eyes through the cornea (the clear, front surface of the eye).The cornea focuses light onto the back of the eye. It comprises five main layers:Epithelium – the thin surface layer. This layer contains fast-growing, easily regenerated cells. It is kept moist with tears.Bowman’s layer – a tough layer comprising mainly protein fibres. It stops the cornea from swelling forwards.Stroma – the thick middle layer making up the majority of the cornea. It contains highly arranged protein fibres and supporting cells called keratocytes.Descemet’s membrane – the thin inner layer that is important for the health of the endothelial cells in the endothelium of the cornea.Endothelium – the layer that is rich in cells that regulate fluid. It prevents the cornea from getting too wet.Light passes from the cornea to the aqueous humour (an area of clear fluid) and the pupil (the circular opening in the centre of the iris, the coloured part of the eye). The iris can contract, limiting the amount of light that can enter the eye, or dilate, increasing the amount of light that can enter the eye. Light then passes from here through a clear, curved structure called the crystalline lens. The lens further focuses light.With the help of ciliary muscles, the lens can change its shape to focus on light reflecting from near or distant objects. This process is called accommodation. Light then passes through vitreous (clear jelly) and onto its final destination, the retina (the light-sensitive tissue at the back of the eye). The retina contains cells called photoreceptors, which send signals via nerve fibres to the optic nerve at the back of the eye.The optic nerve then sends these signals to the visual cortex, an area in the back of the brain that controls an individual’s sense of sight. The visual cortex interprets these signals to build a representation of the object in question.Problems that result when the eyes do not focus properlySometimes, the eyes are not able to focus properly. This can cause a number of problems, including:Myopia (near-sightedness)Myopia, also known as near-sightedness or short-sightedness, occurs when the eye ball is too long from front to back. This means that light rays do not reach the retina. Instead, they stay in the front of the eye, causing distant objects to look blurry.Myopia is usually the result of a combination of genetic and environmental factors that disrupt the normal growth of the eye. Symptoms often start around puberty and gradually worsen until the eye is fully grown (by around the age of eight).Hyperopia (far-sightedness)
Hyperopia, also known as far-sightedness or long-sightedness, occurs when the eye ball is