Refractive Error Information
For your convenience, we have compiled the following information and videos about common refractive error conditions. Just click on the highlighted links to view the videos. For additional information regarding specific medical eye conditions, please visit our patient information pages or call to schedule an appointment at River City Eye Associates (210-930-2015).
Presbyopia is the gradual loss of the eye’s ability to focus on close objects that occurs naturally with age, typically becoming noticeable in the early to mid-40s. It affects virtually everyone regardless of whether they have needed glasses before. The eye’s natural lens becomes progressively stiffer with age, reducing its ability to flex and shift focus for near tasks. The result is that reading, phone use, and other close work become increasingly difficult and require more light or a longer arm’s reach. Common corrections include reading glasses, bifocals, progressive lenses, and multifocal contact lenses. For patients undergoing cataract surgery, premium intraocular lens options can address presbyopia at the time of lens replacement — an important consideration when planning surgical vision correction. Presbyopia is not a disease and cannot be prevented, but it is highly manageable with the right correction strategy.
Hyperopia, commonly called farsightedness, is a refractive error in which the eyeball is shorter than average or the cornea is flatter than normal, causing light to focus behind the retina rather than directly on it. In mild to moderate hyperopia, the eye’s natural lens can compensate through a process called accommodation — which is why many farsighted individuals, particularly younger patients, have no obvious vision complaints. However, this compensation requires constant muscular effort and frequently produces symptoms such as eye strain, headaches, and fatigue after sustained near tasks like reading or screen use, even when distance vision appears normal. In higher degrees of hyperopia, both near and distance vision may be blurred. Uncorrected hyperopia in young children can contribute to amblyopia (lazy eye) and strabismus (eye misalignment), making early detection important. Hyperopia is corrected with plus-powered lenses in glasses or contact lenses.
Myopia, commonly called nearsightedness, is the most prevalent refractive error worldwide, affecting approximately 40% of adults in the United States — a proportion that continues to rise. It occurs when the eyeball is slightly longer than normal or the cornea is too steeply curved, causing light to focus in front of the retina rather than on it. The result is that distant objects appear blurry while near vision remains clear. Symptoms include squinting, eye strain, headaches, and difficulty seeing road signs, whiteboards, or faces at a distance. Myopia typically develops in childhood and progresses through the teenage years before stabilizing in early adulthood. It is corrected with minus-powered lenses in glasses or contact lenses. Patients with high myopia — prescriptions beyond -6.00 diopters — have a meaningfully increased risk of retinal complications including retinal tears and detachment, and benefit from regular dilated eye exams to monitor retinal health even when their vision is otherwise well corrected.
Astigmatism is an extremely common refractive error caused by an irregular curvature of the cornea or natural lens — shaped more like a football than a perfectly round basketball. This uneven curvature prevents light from focusing at a single sharp point on the retina, instead creating multiple focal points that produce blurred or distorted vision at all distances. Astigmatism frequently occurs alongside myopia or hyperopia and is present to some degree in the majority of people, though only optically significant astigmatism affects vision meaningfully. Symptoms include blurred or distorted vision, difficulty with night vision and glare around lights, eye strain, squinting, and headaches. It is corrected with specifically shaped lenses in glasses or contact lenses. For cataract surgery patients, astigmatism correction is an important part of lens selection — toric IOLs and the Light-Adjustable Lens both offer options for addressing astigmatism at the time of surgery, reducing dependence on glasses for distance vision afterward.
A toric intraocular lens is a specialized artificial lens implant used during cataract surgery to correct astigmatism at the same time the cataract is removed. Standard monofocal lenses do not address astigmatism — patients with significant corneal astigmatism who receive a standard lens will typically still require glasses for clear distance vision after surgery. A toric IOL incorporates astigmatism correction directly into the lens implant, aligned to a precise axis during surgery to counteract the eye’s specific corneal irregularity. For appropriately selected patients, toric IOLs can meaningfully reduce or eliminate the need for distance glasses after cataract surgery. Accurate pre-operative corneal measurements are essential for toric lens success. An alternative for patients with astigmatism is the Light-Adjustable Lens, which allows astigmatism correction to be verified and refined with UV light treatments after surgery — based on how the eye actually heals rather than pre-operative estimates alone — offering an added layer of precision for complex cases.