An eyeglass prescription is a precise measurement of the eye’s refractive error, determining the power needed to focus light onto the retina. Refractive errors (nearsightedness, farsightedness, and astigmatism) occur when the eye’s shape prevents light from bending correctly. Since the eye is a dynamic organ influenced by growth, age, and health, this measurement is not fixed. The frequency of prescription updates depends on variables affecting the eye’s structure and focusing power.
Standard Recommended Review Schedule
Routine eye examinations are recommended based on a person’s age and general health status. For children and adolescents, annual checks are necessary because the eyes are still growing rapidly. Physical changes during growth spurts can lead to frequent shifts in nearsightedness, requiring timely correction to support visual development.
For healthy adults aged 18 to 64 with no known risk factors, a comprehensive eye exam is typically recommended every one to two years. This schedule allows for the detection of subtle changes in vision or early signs of eye disease.
Individuals 65 and older should schedule an examination every year. The increased prevalence of age-related eye conditions makes annual checks important for monitoring eye health and ensuring an accurate prescription.
Key Factors Driving Prescription Changes
Age is a common factor driving vision shifts, notably with the onset of presbyopia, which typically begins in the early to mid-40s. This condition arises because the crystalline lens gradually hardens and loses elasticity. This reduced flexibility impairs the eye’s ability to focus on near objects, requiring a progressive increase in reading power.
The development of cataracts, or clouding of the eye’s natural lens, is another age-related change that directly alters the prescription. As the lens becomes denser, its refractive index changes, often causing a “myopic shift” where the eye becomes more nearsighted. Frequent and noticeable changes in an eyeglass prescription can sometimes be an early indicator that a cataract is developing.
Systemic health conditions, particularly diabetes, can destabilize vision through fluctuations in blood sugar levels. High blood sugar alters the osmotic balance in the eye’s lens, leading to temporary swelling or shrinkage that causes transient shifts in refractive error. Doctors often advise against prescribing new glasses until blood glucose levels have been stable for several weeks.
High blood pressure does not typically change the prescription itself, but it can damage retinal blood vessels, causing hypertensive retinopathy. This damage leads to vision problems, such as blurriness or visual field changes, necessitating an exam to assess retinal health. Glaucoma, which damages the optic nerve, is also linked to refractive error, as high nearsightedness is a risk factor for primary open-angle glaucoma.
Prolonged near-work, such as extensive reading or digital screen use, is associated with the progression of nearsightedness, especially in younger individuals. Continuous close focus engages the eye’s accommodative mechanism, which can accelerate the physical elongation of the eyeball (axial length growth). This elongation is the primary structural cause of nearsightedness. Spending time outdoors may be protective against this progression, providing natural light and opportunities for distance viewing that relax the eye’s focusing muscles.
Warning Signs Indicating an Immediate Need for Review
A prescription change may be needed immediately if a person experiences new or worsening symptoms, regardless of the last scheduled exam date. Frequent or persistent headaches, especially after close-up work or driving, can signal that the eyes are straining to focus through an outdated prescription.
Noticeable blurriness, whether at distance or near, that does not clear with blinking is a strong indicator of a refractive change. Difficulty driving at night, including increased glare sensitivity or the appearance of halos around lights, suggests the current correction is insufficient for low-light conditions.
Other concerning symptoms include constant squinting, persistent eye strain or fatigue, or any instance of double vision. These changes mean the current optical correction is no longer providing the clear, comfortable vision required.