Amblyopia (lazy eye)

Amblyopia, often called lazy eye, is a vision condition that begins in early childhood. It happens when one eye, or both eyes in rare cases, doesn’t develop normal vision because the brain relies more on the stronger eye. Vision changes can range from mild to more noticeable, and many children see meaningful improvement with early care.

Because amblyopia affects how the brain learns to see, timing matters. The brain’s visual system develops most rapidly in the first five to six years of life, which makes early diagnosis especially important. At Penn Medicine, experienced eye specialists focus on identifying amblyopia as early as possible and guiding care during this critical window, when vision has the greatest chance to improve.

Amblyopia doesn’t always cause obvious symptoms, especially in young children. Many kids don’t realize one eye isn’t seeing well. Possible signs include:

• Blurry vision in one eye
• Poor depth perception
• Squinting or closing one eye
• Eyes that don’t appear to work together
• Trouble with reading or hand-eye coordination

A lazy eye can develop for a few different reasons, including:

• Vision differences between the eyes: With refractive error, one eye may be much more nearsighted or farsighted, or have more astigmatism, causing the brain to rely more on the stronger eye.
• Eye conditions that block vision: Problems such as cataracts can prevent light from entering the eye clearly, which can interfere with normal vision development.
• Eye misalignment: When the eyes don’t line up properly or appear crossed, a condition known as strabismus, the brain may rely on one eye and ignore the other to avoid double vision.

Amblyopia is usually found during a regular eye exam. An eye doctor checks how well each eye sees, how the eyes work together, and whether there are refractive differences or alignment issues.

Early screening is key. Many children are diagnosed during routine vision checks, even before symptoms are noticeable at home.

Amblyopia can often be improved when caught early. Care is guided by experienced eye specialists at Penn Medicine, who tailor treatment based on what’s causing the vision problem and closely monitor progress to support the best possible outcome. In some cases, treating an underlying condition, such as removing a cataract, may be needed before vision therapy begins.

Other treatments may include:

• Glasses to correct nearsightedness, farsightedness, or astigmatism.
• An eye patch covering the stronger eye for part of the day to help build strength in the weaker eye.
• Eye drops to temporarily blur the stronger eye instead of a patch.

Amblyopia can’t always be prevented, but it can often be caught early before vision loss becomes permanent. Regular eye exams during infancy and early childhood are the most effective way to protect a child’s vision.

If something seems off, such as eye crossing, squinting, or trouble seeing, it’s worth checking sooner rather than later. Early attention can make a lifelong difference.