Blurred vision is a common and expected physical change during pregnancy. This temporary alteration in sight is generally not a cause for alarm, as it results from hormonal and physiological adjustments occurring throughout the body. The same mechanisms that cause swelling in the hands or feet can similarly affect the sensitive structures of the eye. Understanding these benign, temporary changes is key, but it is also important to recognize when a vision change signals a potentially serious medical condition.
Hormonal Causes of Temporary Vision Changes
The most frequent reason for sight changes during pregnancy is increased fluid retention, which affects the cornea. The cornea, the clear, dome-shaped front surface of the eye, can swell and thicken due to higher levels of the hormone progesterone. This subtle edema alters the cornea’s curvature, temporarily changing how light enters the eye.
This change in curvature often results in a temporary shift toward nearsightedness, known as a myopic shift, or a change in existing astigmatism, leading to mild blurriness. These refractive changes are typically minor and are most noticeable during the second and third trimesters when fluid volume is at its peak. Because this swelling is tied directly to the pregnancy state, vision usually stabilizes and returns to its pre-pregnancy prescription within a few weeks or months after delivery.
Hormonal fluctuations also directly impact the quality and quantity of the tear film, leading to dry eye syndrome. Increased estrogen and altered androgen balance can disrupt the glands responsible for producing the oily layer of the tear film. When this lipid layer is compromised, tears evaporate too quickly, resulting in dry, irritated eyes and fluctuating vision.
The instability of the tear film often makes wearing contact lenses uncomfortable or impossible for many pregnant individuals. The combination of an altered corneal shape and decreased tear film quality can prevent the lens from sitting properly on the eye’s surface.
Recognizing Serious Vision Symptoms
While many vision changes are harmless, certain severe symptoms signal underlying complications that require urgent medical evaluation. The sudden onset of severe vision changes, such as flashing lights, auras, or persistent blind spots, can be a warning sign of pre-eclampsia. This condition involves high blood pressure and signs of damage to another organ system, typically after the 20th week of pregnancy.
Preeclampsia-related vision issues stem from high blood pressure causing changes in the blood vessels of the retina, a condition called retinopathy. Symptoms like scotoma (areas of vision loss) or photopsia (flashing or shimmering lights) are caused by vascular spasms or damage in the retina or the brain’s visual cortex. In severe cases, high blood pressure can lead to temporary bilateral vision loss or cortical blindness, which usually resolves after delivery but demands immediate treatment.
Gestational diabetes, which is high blood sugar that develops during pregnancy, is another condition linked to problematic vision changes. Elevated blood glucose levels can cause the lens of the eye to swell. This swelling temporarily changes the lens’s refractive index, leading to fluctuating or blurred vision that may change throughout the day based on blood sugar control.
For individuals with pre-existing diabetes, pregnancy can accelerate the progression of diabetic retinopathy, damaging the small blood vessels in the eye. Any sudden change in visual acuity, double vision (diplopia), or the appearance of many new floaters should be considered an emergency. These symptoms indicate a need for prompt intervention to protect both maternal and fetal health.
Practical Management and Care
For common, temporary vision changes, there are several simple strategies to manage discomfort and maintain clear sight. Dry eyes can be managed by using preservative-free lubricating eye drops or artificial tears, which help stabilize the tear film. Individuals who experience discomfort with contact lenses should temporarily switch to wearing glasses.
Attempting to force contact lens use on a temporarily reshaped or dry eye can lead to irritation and potential complications. It is recommended to postpone any permanent changes to an eyeglass prescription until after delivery. Since the refractive changes are temporary, obtaining a new prescription during pregnancy will likely result in glasses that are incorrect postpartum.
The safest time for a new, permanent prescription is typically six to eight weeks postpartum, once hormones and fluid levels have returned to normal. During any routine eye examination, it is important to inform the optometrist or ophthalmologist about the pregnancy. This ensures the eye care professional can differentiate between normal physiological changes and more serious, pathological conditions.