These eye conditions could be due to refractive errors which happen when the eye does not bend or refract light onto a single focusing point, resulting in blurred vision.
Myopia, or shortsightedness, is the most common refractive error of the eye. In myopia, the image the eye receives is not clear because the light rays come to focus before they reached the retina.
If you are shortsighted, you will be able to see well for close-up tasks such as reading, but have difficulty reading road signs and seeing distant objects clearly.
Hyperopia, or longsightedness,is a common focusing problem which occurs when the focal point of a visual image falls behind the retina instead of directly on it.
If you are longsighted, you may be able to see distant objects well but have difficulty focusing on near objects.
Astigmatism (“San Guang”) is also a refractive error where problem lies in how the eye focuses light. This happens when the light fails to come to a single focus on the retina due to the irregular shape of the cornea.
If you have Astigmatism, your vision would likely be blurred or distorted to a certain degree at all distances.
Presbyopia, also known “Lao Hua”(“ageing eye”), is an age-related eye condition which usually occurs beginning around age 40. This happens when the lens is not able to change its shape as it grows larger with age. Thus, it loses its elasticity and ability to focus on near objects.
If you are starting to have presbyopia, you will find yourself holding reading materials like books and magazines further away in order to read clearly.