The 6 Most Common Mistakes in Eye Exams and Eyeglass Prescriptions

This is one of the most common mistakes. Some optical stores rely solely on the printout from an autorefractor when making glasses. However, computerized refraction is only a preliminary screening reference—it is not a final eyeglass prescription.

The human eye has a strong accommodative ability. After prolonged visual fatigue, close-up work, or periods of stress, the ciliary muscles may remain in a state of accommodative spasm. An autorefractor may then produce an artificially high refractive result. It cannot reliably distinguish true myopia from accommodative effects, nor can it account for a person's everyday visual habits. It can only provide a starting range for further refraction and should not be used directly as the final basis for making eyeglasses.

Some people focus excessively on achieving very high visual acuity, such as 1.2 or 1.5, believing that higher visual acuity is always better. In reality, the goal of an eyeglass prescription is clear, comfortable, and sustainable vision—not excessive correction.

Overcorrection can keep the eyes under constant accommodative strain. With prolonged wear, it may contribute to visual fatigue, dizziness, nausea, and eye discomfort, and may even aggravate myopia progression. Adults, in particular, may experience a noticeable increase in prescription power or worsening astigmatism.

Many adults go years without updating their prescription and simply use the same numbers when ordering new glasses. However, the condition of the eyes is not static. Factors such as chronic sleep deprivation, excessive near work, dry eyes, and changes in intraocular pressure can affect refractive status and binocular visual function.

Although myopia often becomes more stable in adulthood, astigmatism, binocular balance, and accommodative function can continue to change. Using an outdated prescription may cause the eyes to compensate unnecessarily, resulting in glasses that feel increasingly tiring to wear.

Many people focus only on their myopia prescription and overlook astigmatism or treat the astigmatism axis as an approximate value. An inaccurate axis can cause visual discomfort, including double vision, eye strain, and headaches.

Astigmatism involves an uneven refractive power of the eye and requires accurate measurement of both cylinder power and axis. Estimating or omitting astigmatism correction can be an important contributor to persistent visual fatigue and blurred vision.

One of the biggest weaknesses of rushed eyeglass fitting is skipping the trial-wear stage. Instrument-based refraction measures static optical parameters, but it cannot fully account for dynamic visual situations such as looking at distant and near objects, walking, or working at a desk.

Without adequate trial wear, glasses may provide clear distance vision but cause dizziness during near work, make the ground appear distorted while walking, or create a feeling of imbalance between the two eyes.

Children and teenagers have strong accommodative abilities. Prolonged reading or screen use can easily trigger accommodative spasm and produce an apparently myopic result. A standard refraction may not adequately distinguish true myopia from accommodative effects, potentially resulting in an unnecessarily strong prescription.

According to authoritative myopia-management guidelines, cycloplegic refraction is considered the gold-standard approach for initial examinations in children under 12 and for individuals whose refractive error fluctuates significantly.