Ophthalmic Lexicon
What is astigmatism? What happens with cataracts? What does diopter mean? The most important technical terms from ophthalmology explained in a way that anyone can understand!
Astigmatism, also known as corneal curvature.
Astigmatism is caused by a curvature of the cornea or lens that refracts horizontally incident light differently than vertically incident light. Instead of being bundled into a single focal point, the incident rays of light are split into two focal lines. Astigmatism can only be corrected with cylindrical/toric lenses, not spherical lenses.
Diopter is a unit of refractive power and is the reciprocal of the distance in meters between the lens and the focal point.
Diopters indicate the power of the lens.
In medicine, the fundus is the background or floor of an organ, in our case the fundus of the eye. The fundus is the visual area of the retina. It is visible when you look into the eye through the pupil.
Clarity, farsightedness: The refractive power of the eye is too low and/or the length of the eyeball is too short. With sufficient accommodation (autofocus), the eye sees sharply at a distance. Farsightedness is corrected with positive lenses.
Cataract is a clouding of the lens of the eye. It is a progressive process that leads to increased sensitivity to glare, but more importantly, to a decrease in visual acuity, including blindness. A simple operation to replace the diseased lens with an artificial lens can prevent blindness.
Near-sightedness: The refractive power of the eye is too strong and/or the eyeball is too long. The eye sees blurred in the distance and is corrected with negative lenses.
The retina: It is made up of cones for daytime vision. The rods allow us to see in the twilight. The stimuli from the photoreceptors are transmitted to the brain via the optic nerve.
Spherical lenses have the same power over the entire surface. Spherical lenses can correct nearsightedness, farsightedness and presbyopia, but not astigmatism.
In a spherical correction, the proportions of nearsightedness and farsightedness are corrected. Astigmatism (corneal curvature) cannot be corrected.
Studies have shown that with optimal spherical correction, approximately 80% of people can be helped to the point where they can drive safely.
