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Eye Exams

Patient Having an Eye Exam

South Texas Eye Institute offers comprehensive routine eye care exams. You will be able to receive immediate appointments in emergency situations, otherwise we will do our very best to schedule you within a convenient time frame.

Please contact us within 48 hours if you are unable to keep your scheduled eye exam appointment. We offer a 15 minute window for your to arrive at your scheduled appointment time. We look forward to seeing you at our San Antonio office soon!

Refractive Errors

The eye is comprised of numerous structures, including the cornea (clear surface of the eye), lens (part that refracts/focuses light), iris (colored part of the eye), pupil (open part in center of iris), retina (eye structure that converts image into electrical energy), and optic nerve (pathway to brain stem).

Often, the eye is compared to a camera. When working properly, the eye is able to take in light rays, refract it, and clearly interpret the image. However, if the eye is shaped irregularly or if light rays do not properly focus on the retina, then vision can become blurred. Imperfect vision is typically the result of a refractive error, like nearsightedness, farsightedness, astigmatism, or presbyopia.


Nearsightedness, or myopia, is the inability of a person to clearly see distant objects. The condition, named for a person’s ability to only see near objects, occurs when an eye is too long or its cornea is too steeply curved for the eye’s shape. This irregularity causes light to focus in front of (not on) the retina, creating a blurred appearance of distant objects.


Just the opposite of nearsightedness, farsightedness, or hyperopia, is the inability of a person to clearly see near objects. A person with farsightedness also has a misshapen eye; however, the eye is either too short or the cornea is too flat. In hyperopic patients, light focuses behind the retina, resulting in blurred near vision.


Unlike nearsightedness and farsightedness, astigmatism is not caused by the eye’s length. Where an eye without astigmatism has a smooth and evenly shaped lens and cornea, an astigmatic eye has a cornea or lens that is irregularly shaped in some areas. This irregularity can distort both near and far vision.


Unlike the other refractive errors, presbyopia is not caused by the shape of the eye, but by the aging of the aging of the eye. A young, healthy eye is able to use accommodation, the ability to shift focus from near to far (and all distances in between). However, as the eye ages, the eye’s crystalline lens begins to lose its flexibility and has trouble focusing on near objects. Typically around the age of 40, a person will notice that he or she has difficulty with close-up tasks, like reading.

Nearsighted individuals may be able to see better simply by removing their glasses for near tasks. Others will either need to get bifocals (if they already wear glasses for farsightedness or astigmatism) or begin to use reading glasses. Because the hardening of the eye’s lens is a natural part of the aging process, all adults will eventually be affected by presbyopia.