Eye prescriptions measure the eye’s refractive error, which is its inability to focus light correctly onto the retina. Common refractive errors include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (irregular curvature of the cornea). The prescription provides the lens power needed to bend incoming light so it lands precisely on the retina, ensuring clear vision. How often these measurements change depends heavily on a person’s age, underlying health, and lifestyle.
The Routine Frequency for Healthy Adults
For the average adult between the ages of 18 and 60 who has no existing risk factors or chronic diseases, a comprehensive eye exam is recommended every one to two years. This routine frequency is the baseline for monitoring vision stability and overall ocular health.
During this regular check, the eye doctor screens for silent diseases that do not immediately affect vision, such as glaucoma. Glaucoma involves damage to the optic nerve and often develops without symptoms in its early stages. Therefore, a regular exam is not solely about updating a prescription but also about maintaining the long-term integrity of the eye structure.
How Age Influences Stability
Vision stability is closely linked to the body’s physical development, making age the single most significant factor influencing how often a prescription changes.
In childhood and adolescence, prescriptions change frequently due to the rapid physical growth of the eye. The elongation of the eyeball, known as axial length growth, often leads to the progression of myopia (nearsightedness). This period of frequent, often annual, changes slows down as the body reaches physical maturity, with vision generally stabilizing around age 25.
Young adulthood, spanning the 20s and 30s, represents the period of greatest refractive stability for many people. The eye has completed its growth, and the prescription often remains steady for several years at a time. However, a small percentage of adults can experience continued, slow progression of myopia, sometimes linked to intense visual demands.
The mid-40s mark the onset of presbyopia, a universal change where the eye’s natural lens begins to lose flexibility and harden. This makes focusing on near objects difficult, requiring a new “add” power for reading, often leading to the need for bifocals or progressive lenses. The near-vision correction needed for presbyopia continues to increase gradually into the early 60s as the lens becomes completely inflexible.
Later in life, vision changes are often driven by the development of cataracts, the clouding of the eye’s lens. A developing cataract can cause a refractive shift, often increasing nearsightedness, requiring a new prescription. After age 65, annual exams are recommended because the risk of developing sight-threatening conditions, including cataracts and macular degeneration, increases significantly.
Health Factors That Accelerate Change
Certain systemic health conditions and life events can cause rapid or unpredictable shifts in refractive error outside of normal aging patterns.
Diabetes is a prime example, as uncontrolled blood sugar levels directly affect the eye’s lens. When blood glucose is elevated, the lens swells with fluid, temporarily changing its shape and causing a shift in prescription, often toward nearsightedness. A new prescription should not be issued until blood sugar levels have been stable, as vision will fluctuate until glucose is controlled.
Hormonal fluctuations during pregnancy can induce temporary changes in vision. Increased fluid retention and hormonal shifts can cause the cornea to swell and change its curvature. These temporary changes may lead to a noticeable shift in prescription, which typically reverts to the pre-pregnancy state several months after delivery.
Prolonged and intense near-work, such as extended daily use of digital screens, can accelerate myopia progression even in adults. This sustained visual stress can lead to pseudo-myopia, where the eye’s focusing muscles remain tensed after close-up work, making distance vision temporarily difficult. While often reversible with rest, continuous near-work has been linked to permanent, slower worsening of nearsightedness in adults.
Signs You Need an Urgent Appointment
While some gradual blurring is expected, certain symptoms indicate a more significant or potentially serious change that requires immediate professional evaluation.
A sudden or rapid blurring of vision, especially if it affects only one eye, warrants an urgent appointment. The sudden appearance of flashing lights or a shower of new floaters (small spots drifting across the visual field) can signal a serious issue like a retinal tear or detachment. This is particularly true if the flashes and floaters are accompanied by a shadow or curtain moving across the field of view.
Other concerning symptoms include the sudden onset of double vision, which may indicate an eye alignment or neurological issue. Frequent headaches coinciding with visual tasks, halos around lights, or significant difficulty with night driving may also signal that the prescription has changed enough to cause substantial eye strain.