Nearsightedness (myopia) is when parallel light rays are focused in front of the retina after passing through the refractive system of the eye in a relaxed state of adjustment. The far point of myopia is at a point in front of the eye.
(a) Myopia classification.
1. According to refractive component.
Refractive myopia (refractive myopia)
Axial myopia (axial myopia)
2. According to the degree of myopia.
Mild myopia (mild) <-3.00 degrees
Moderate myopia (moderate) -3.00 ~ -6.00 degrees
High myopia (high) -6.00 ~ -9.00 degrees
Ultra-high myopia (ultra-high >-9.00 degrees)
3.Classification according to disease progression and pathological changes
(1) Simple myopia: refraction within -6.00 degrees, corrected visual acuity can reach normal.
(2) Pathological myopia: The eye axis is still lengthening after the age of 20 and causes pathological changes. For example: arcuate spots, lattice degeneration in the peripheral part of the retina, leopard-like fundus; macular hemorrhage or subretinal neovascular membrane, Fuchs’ spots; vitreous liquefaction, clouding and posterior vitreous detachment, posterior scleral staphyloma.
(ii) Clinical manifestations.
Blurred vision at distance, good vision at near. Since no or little adjustment is used when looking at near, the collecting function is weakened, which easily causes exotropia or exotropia. Squinting when looking at distance.
In addition to poor distance vision, higher myopia is often accompanied by poor night vision, flying mosquitoes, floating objects, and flashing sensation.
Fundus changes: arcuate spots, leopard’s stripe fundus, macular hemorrhage or subretinal neovascular membrane, Fuchs’ spots, retinal peripheral lattice degeneration, cystic degeneration. Vitreous liquefaction, clouding and posterior vitreous detachment, and posterior scleral staphyloma.
Pathological myopia is prone to retinal detachment and macular hemorrhage, which can seriously affect visual acuity and even lead to blindness.
(C) Myopia correction.
Applying suitable concave lenses to make the light diverge and then focus on the retina.
1.Frame glasses
2.corneal contact lens.
3.Refractive surgery.