Blurry vision, defined as a loss of visual acuity, can be unsettling, especially when it affects only one eye. When the right eye specifically becomes blurry, this is known as monocular vision loss. Causes range from common, easily corrected surface issues to more complex problems deep within the internal structures. Because the visual system is intricate, this information is for educational purposes only and should never substitute for a professional medical diagnosis from an eye care specialist.
Focusing on the Front of the Eye (Refractive Changes and Surface Issues)
The most common reasons for unilateral blurring involve the outermost layers of the eye, which are responsible for initial light focusing. A change in the eye’s primary focusing power, known as a refractive error, is one such cause. This occurs when the shape of the eye prevents light from focusing directly onto the retina, leading to fuzzy vision correctable with lenses. When the refractive error differs significantly between the two eyes, a condition called anisometropia exists, which can make only the right eye feel blurry. This asymmetry may arise from the eyeball growing slightly longer or shorter (myopia or hyperopia) or an uneven curvature of the cornea (astigmatism) affecting one side more than the other.
Issues with the tear film, such as dry eye syndrome, are also frequent causes of blurred vision that can affect one eye more than the other. The tear film provides a smooth, clear surface necessary for sharp vision, and its instability causes fluctuating blurriness that may temporarily improve with blinking. Unilateral dry eye can be linked to factors like sleeping position, a recent eye injury, or specific gland issues in the affected eye. The cornea, the clear dome covering the iris and pupil, is also vulnerable to localized issues that cause blurring. A minor corneal abrasion (a scratch) or a localized infection like keratitis can cloud this normally transparent tissue, disrupting the smooth passage of light.
Conditions Affecting Internal Structures (Lens, Retina, and Optic Nerve)
Blurring that originates deeper within the eye structure often points to more serious or progressive conditions, beginning with the lens. The eye’s natural lens, located behind the iris, focuses light onto the retina, but it can become cloudy over time, a process known as a cataract. While cataracts generally affect both eyes, they frequently progress asymmetrically. This means the opacification in the right eye may be more advanced, causing noticeable blurring, glare, and difficulty with night vision on that side first.
Behind the lens, the retina and macula convert light into neural signals, and issues here can cause profound, unilateral vision changes. Diabetic retinopathy, a complication of diabetes, can cause blood vessels in the retina to leak or swell, leading to fluid buildup in the macula (macular edema) and blurred central vision in one eye. Similarly, age-related macular degeneration (AMD), which involves the deterioration of the macula, can manifest as blurring or distortion in one eye initially, especially in the wet form involving abnormal blood vessel growth.
The optic nerve transmits visual information from the retina to the brain, and its compromise can result in monocular blurring. Optic neuritis, which is inflammation of this nerve, often causes sudden vision loss and pain with eye movement, typically affecting only one eye. Another serious condition is acute angle-closure glaucoma, which involves a rapid buildup of pressure inside the eye that damages the optic nerve. This leads to sudden, painful blurring, often accompanied by nausea or the sight of halos around lights.
Symptoms Requiring Immediate Medical Attention
If blurry vision in the right eye is sudden, severe, or accompanied by other specific symptoms, it may signal a time-sensitive medical emergency. A sudden, painless loss of vision, whether temporary or permanent, may indicate a vascular event, such as an eye stroke (retinal artery occlusion) or a transient ischemic attack (TIA). Vision changes accompanied by severe, deep eye pain, intense headache, nausea, or vomiting are classic signs of acute angle-closure glaucoma.
Any experience of a sudden increase in floaters, flashes of light, or the perception of a dark shadow or “curtain” moving across the field of vision can indicate a retinal tear or detachment. A retinal detachment is an emergency because the retina separates from its nourishing tissue. Delay in treatment can result in permanent vision loss. Neurological symptoms occurring alongside blurring, such as sudden weakness or numbness on one side of the body, difficulty speaking, or imbalance, are critical indicators of a potential stroke.