Common questions and answers about contact lens parameters
一、 Why is the base arc related to wearing?
In popular terms, the base arc indicates the curvature of the lens, so its match with the eyeball means the tightness worn. Lens, the smaller the base arc, the tighter, will compress the eyeball and cause discomfort, the base arc is too large and too loose, it is easy to slide or even slide.
二、 Why is it not that the higher the water content, the better?
Although the water content affects the softness and comfort of the lens to some extent, the high water content will also accelerate the water evaporation in the process of wearing. Since the water content required for the lens is fixed, the missing water caused by evaporation is replenished by the tears, which puts some additional burden on the eye. When the wearer's tear secretion is insufficient, there will be obvious dry eyes, pain, tears and other symptoms, which may also cause the wearer to suffer from dry eye disease.
三、 What factors affect the oxygen permeability of the lens?
The material, thickness, and water content of the contact lenses will affect the oxygen permeability of the lens. In terms of materials, the silicon hydrogels are more oxygen-permeable than the hydrogels. In terms of thickness, the thin lens is naturally more permeable, as oxygen is easier to reach the cornea through the lens. In terms of water content, the higher the water content of hydrogel contact lenses, the stronger the oxygen permeability, but the oxygen permeability of silicon hydrogel will not be limited by the water content.
四、 Why is the degree of contact lens different from the degree of frame glasses?
Although contact lenses and glasses are both vision correction tools, they are clearly seen at different distances from the eyeball when worn. Contact lenses are close to the cornea, almost zero distance, and the lens of the glasses has a certain distance from the eyeball. According to optical principle, the degree of myopic contact lens can be slightly lower than the degree of frame glasses commonly, and myopic degree is heavier, the difference of degree is bigger.