Retinal thicknesses of patients with high myopia (HM) during the third trimester of pregnancy are reduced compared with nonpregnant, age-matched patients with HM, according to a study published in BMC Ophthalmology.
Researchers conducted a case-control study to observe and compare the differences in retinal thickness using optical coherence tomography (OCT) between the 2 groups of individuals (N=89). The study included 39 eyes from 39 patients with HM in the third trimester and 50 eyes of 50 age-matched patients who were not pregnant and had HM. Retinal thickness in the macular region was measured using spectral domain OCT, and data from the 2 groups were compared using independent-samples t test. Mean gestational age of the treatment group was 35.09±2.44 weeks.
The study found a significant decrease in the average thickness of the superior retinal foveal and parafoveal area, and the parafoveal superior, inferior, and temporal quadrants of the superficial retina in the study group compared with the treatment group (P <.05). Additionally, average thickness of all quadrants of the retina in the parafoveal area, with the exception of the nasal quadrant, were significantly decreased in the study group compared with the patients in the control group (P <.05).
Sex hormone receptors are contained in the cornea, tarsal gland, choroid, retina, and other ocular tissues, the study explains, and changes in hormone levels during pregnancy affect ocular blood flow. Additionally, estrogen and progesterone serum levels increase throughout pregnancy, which has varying effects though their receptors and mRNA expression.
“Estrogen regulates ocular blood flow by regulating vasodilation,” researchers explain. “Elevated estrogen levels will lead to an increase in the synthesis of nitrous oxide and a decrease in the synthesis of endothelin-1, both of which will lead to a decrease in vasodilation and vascular resistance.”
Research further indicates that during pregnancy, changes to the cardiovascular system, such as changes in heart rate, systemic vascular resistance, and blood volume subsequently affect ocular blood flow.
Study limitations include small sample size and its single-center nature. Additionally, there was no postpartum follow-up.
Liu C, Wei P, Li J. The thickness changes of retina in high myopia patients during the third trimester of pregnancy: a pilot study. BMC Ophthalmol. Published online October 27, 2021. doi:10.1186/s12886-021-02137-5