A comprehensive review highlighted the extensive physiological and pathological changes that occur in the eye during and after pregnancy, including those that persist long after delivery.

In their Clinical and Experimental Optometry article, researchers from the University of Melbourne, Monash University, and the University of Tasmania emphasized that pregnancy introduces hormonal fluctuations and metabolic changes that can manifest in ocular structures from the anterior to posterior eye.

"While many pregnancy-associated changes are temporary and resolve postpartum, it is also recognized that some changes persist after pregnancy, with a notable absence of literature on ocular changes with loss or termination of pregnancy," Bao N Nguyen and colleagues wrote in the review.

Hormonal Mechanisms of Ocular Changes

The researchers explained that pregnancy induces dynamic hormonal changes that directly affect ocular tissues through specific receptor activity. Sex hormones play a functional role in modulating ocular surface homeostasis by influencing tear production, immune regulation, wound healing, and cell regeneration.

"Specific receptors for sex hormones have been found in various structures of the anterior eye, such as estrogen, progesterone, and androgen receptors in the conjunctiva, lacrimal gland, meibomian gland, tarsal plate, cornea, iris and ciliary body," they described.

In the posterior eye, androgen, estrogen, and progesterone receptor messenger RNA have been identified in the retina, choroid, and retinal pigment epithelial cells. Additionally, pregnancy-related circulatory changes, including increased blood volume and cardiac output, affect the eye's vascular layers.

Physiological Changes in Normal Eyes

The review also catalogued numerous pregnancy-related physiological changes in healthy eyes:

Eyelids

Melasma, characterized by brown to gray-brown patches of increased pigmentation, can occur around the eyes and eyelids with a reported prevalence of up to 45% depending on ethnicity/skin color. Onset typically occurs in the first or second trimester and may persist postpartum in approximately 9% of cases.

Tear Film

Using clinical Schirmer testing, several studies have reported relatively low tear production during pregnancy, which appears to recover immediately postpartum. The researchers noted: "Poor tear film quality can also occur with decreased lipid production and secretion from the meibomian glands, corroborated by recent reports of reduced tear break-up time and loss of visible meibomian glands on clinical evaluation."

Cornea

Pregnancy is associated with increased corneal thickness and curvature, especially in the second or third trimesters. According to the review: "corneal changes are thought to arise from increased tissue hydration or water retention, a common finding throughout a pregnant woman's body, and reportedly return to prepregnancy values by 3 months after delivery."

Intraocular Pressure

Reduced intraocular pressure (IOP) during pregnancy is "attributed to increased fluid outflow facility (blood vessel dilatory effects of estrogen and progesterone) and reduced peripheral vascular resistance (reduced episcleral venous pressure), rather than a change in aqueous humor formation." IOP reportedly rebounds 3 to 6 weeks after delivery to levels that are indistinguishable from the first trimester.

Pathological Conditions Newly Onset in Pregnancy

The review further identified several pathological conditions that may develop during pregnancy in otherwise healthy patients:

• Corneal thinning/ectasia in patients who previously underwent corneal refractive surgery
• Idiopathic intracranial hypertension, which—though rare during pregnancy—was associated with "more severe papilledema and more severe and protracted vision loss," according to the review
• Central serous chorioretinopathy which may occur in the second or early third trimester

Exacerbation of Pre-existing Conditions

Pregnancy can worsen several pre-existing conditions:

• Diabetic retinopathy, especially during the second and third trimesters
• Keratoconus; pregnancy potentially causes decreased corneal thickness and increased ectasia
• Dry eye disease; prevalence is estimated as high as 78% in pregnant women

Clinical Recommendations

The researchers emphasized the importance of eye care before, during, and after pregnancy: "For the clinician, in most cases, the physiological and functional changes to the eye and vision appear to be temporary and mostly confined to pregnancy, requiring no active intervention."

However, they recommended that "new glasses or refractive surgeries should be avoided until after the end of pregnancy, once visual function has stabilized or returned to the prepregnancy state."

The review also highlighted significant research gaps, particularly regarding ocular changes associated with pregnancy loss. "Whether pregnancy-related effects on the eye persist with miscarriage or termination, and for how long, remain unanswered questions," the investigators noted.

The researchers declared no competing interests.