October 2020


Research Highlight
What happens to vision during pregnancy

by Maxine Lipner Contributing Writer

“Maybe there is something physiologic going on during pregnancy. Or these women are just waiting to update their prescription for the duration of their pregnancy.”
—Frances Wu, MD

Pregnancy can cause a woman’s vision to fluctuate, but is this cause for concern? Research indicates that there is no significant difference in refractive status among pregnant women compared to their non-pregnant counterparts.1
Frances Wu, MD, wanted to investigate refractive shifts after noticing some of her pregnant patients reported intermittent or recent blurred vision but could correct to 20/20. “I had this question in my mind as to whether there was any change in their refractive status that was causing these reports of blurry vision,” Dr. Wu said. However, the literature was unclear. There was some prior research showing changes in refractive error during pregnancy, but these studies were based on self-reported changes and conducted on a smaller scale. Dr. Wu set out to look at this on a larger, systematic scale.
Investigators drew on data from the National Health and Nutrition Examination Survey (NHANES), which is conducted every 2 years. “In the years from 2005 through 2008 they did collect ophthalmologic data,” Dr. Wu said. Investigators matched 301 pregnant women in the database with 301 non-pregnant women who had similar baseline characteristics. Analysis revealed there was no difference in the objective refraction, Dr. Wu reported.
Looking at more detailed characteristics, specifically 61 women who were pregnant and who wore glasses, Dr. Wu said, “We looked for differences between the objective refraction and lensometry data for the glasses they came in with, and we found that the pregnant and non-pregnant groups were similar.”
However, when information on trimester was taken into account, investigators found a greater change in refraction for those who were later in pregnancy. There was no trend toward either myopia or hyperopia.
Dr. Wu was somewhat taken aback by the results. “There are a lot of studies that show there is some kind of change in refraction, so it is surprising that there was no change,” she said, adding that there might a small subset who had a change not reflected in the greater general population considered in the pooled data.
Investigators were also interested in the refraction change found later in pregnancy. “Maybe there is something physiologic going on during pregnancy,” Dr. Wu said. “Or these women are just waiting to update their prescription for the duration of their pregnancy.”
Dr. Wu thinks women who experience blurry vision later in pregnancy should consider updating their glasses prescription rather than delaying it out of concern that their pregnancy is affecting their refraction.
However, considering refractive surgery for pregnant women is somewhat controversial. The classic thinking is that pregnancy is a contraindication for refractive surgery, Dr. Wu noted. “At least at UCSF, it’s not our practice to do refractive surgery on women who are pregnant,” she said, adding that even though no major changes were shown here, physicians should still proceed with caution given that the study was not prospective. “I still would not be encouraging women to get LASIK or PRK during their pregnancies,” she said.
While most pregnant women are likely willing to postpone refractive surgery until after they give birth, some may already be invested in having the procedure done. Those who wear contact lenses, for example, must commit to not wearing them for a period of time in order to obtain the best measurements, Dr. Wu pointed out. If a woman has already been planning to have refractive surgery and then finds out that she is pregnant after investing time in getting ready for the procedure, she may still wish to undergo the surgery. “In the U.S., 50% of pregnancies aren’t planned,” she said. Still, Dr. Wu maintains her recommendation to wait until after delivery for refractive surgery.
Dr. Wu hopes that others come away from this study with the realization that there is no definitive change in refraction during pregnancy. The difference found late in pregnancy between the patient’s spectacles and her autorefraction may simply reflect a delay in getting a new refraction rather than real physiologic changes. “But we’re not able to say what the true cause is, given the study limitations,” she said.

About the doctor

Frances Wu, MD
Department of Ophthalmology
University of California,
San Francisco (UCSF)
San Francisco, California


1. Wu F, et al. Refractive status during pregnancy in the United States: results from NHANES 2005–2008. Graefes Arch Clin Exp Ophthalmol. 2020;258:663–667.

Relevant disclosures

Wu: None


Wu: franceswu07@gmail.com

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