PREGNANCY and EYE

PREGNANCY and EYE

During pregnancy,  progressive physiological changes that occur are essential to support and protect the developing fetus in addition to prepare the mother for parturition.

These changes can lead to few ocular complications.

In general, the ocular effect of pregnancy can be divided in to physiologic and pathologic changes.

The pathologic changes are further divided in to the following:

Ocular changes occurring for the first time during pregnancy

An already existing ocular pathology that is modified by pregnancy

Ocular complications of systemic diseases.

Physiologic Changes

Eyelids

Increased pigmentations around the eye called as melasma or chloasma

Postulated that hormonal variations of pregnancy increase melanin as a result of an increase in both melanogenesis and melanocytosis

Tear

Pregnancy affects the physiology of the tear film resulting in dry eye syndrome.

Cornea

Cornea may show changes in sensitivity, thickness or curvature. Corneal sensitivity tends to decrease. A measurable increase in corneal thickness due to edema has been reported to occur during pregnancy. An increase in corneal curvature also has been reported.

Changes in thickness may alter the refractive index of the cornea; thereby changing refraction. Many women develop contact lens intolerance while pregnant despite a previous success. This intolerance may be due to the increase in either corneal curvature or thickness.

 It is advisable that pregnant women wait until at least several weeks postpartum before obtaining a new spectacle prescription or new contact lens fitting.

Lens

Transient loss of accommodation has been reported previously both with pregnancy and lactation.The timing for refractive surgery in a pregnant woman or in a woman planning to become pregnant can be a difficult decision. It is better to delay refractive surgery during pregnancy and wait until stability of refraction is clear postpartum.

Intraocular pressure

IOP decreases during pregnancy.

Immunity

Pregnancy is associated with immune suppression, an essential physiologic element for the implantation of the embryo. It is associated with lower rates of flare-ups of non-infectious uveitis compared to the non-pregnant state. Pregnancy has a beneficial effect on number of uveitis syndromes including Vogt-Koyanagi-harada syndrome, Behcet disease and the idiopathic uveitis syndrome.

Ocular changes occurring for the first time during pregnancy

Preeclampsia and eclampsia. 

Although visible retinal vascular changes occur in 40 to 100 percent of preeclamptic patients, visual symptoms are reported in 25 to 50 percent. These symptoms, which tend to worsen with increasing disease severity, include blurred or decreased vision, photopsia, scotomata, diplopia, visual field defects, and blindness.The most common ocular finding is constriction or spasm of retinal arterioles, with a decreased retinal artery-to-vein ratio correlating with severity. If the constriction is severe, changes associated with hypertensive retinopathy may occur, including diffuse retinal edema, hemorrhages, exudates, and cotton-wool spots.

Other ocular abnormalities seen in preeclampsia and eclampsia include white-centered retinal hemorrhages, papillophlebitis, Elschnig spots, macular edema, retinal pigment epithelial (RPE) lesions, retinal artery and vein occlusion, optic neuritis, optic atrophy, and ischemic optic neuropathy.

Exudative (or serous) retinal detachment occurs in less than 1 percent of patients with preeclampsia and in 10 percent with eclampsia, although preeclamptic and eclamptic women with HELLP syndrome (hemolysis/elevated liver enzymes/low platelet count) may be approximately seven times more likely to develop a retinal detachment than those who do not have the syndrome

Central serous chorioretinopathy.

 CSCR results in an accumulation of subretinal fluid that leads to a circumscribed neurosensory retinal detachment in the macula at the level of the RPE.

Elevated levels of endogenous cortisol are thought to lead to increased permeability in the blood-retinal barrier, choriocapillaris, and RPE. White fibrous subretinal exudates are found in 90 percent of pregnancy-associated cases of CSCR, compared with 20 percent of general cases.

Although CSCR usually resolves within a few months after delivery and visual acuity returns to normal, changes to the central visual field, metamorphopsia, and RPE alterations may persist. Diagnosis typically is made clinically, but optical coherence tomography has shown value in both identifying and following patients with CSCR.

Occlusive vascular disorders. 

Purtscher-like retinopathy, most likely from arteriolar obstruction by complement-induced leukocyte aggregation, has been documented in the immediate postpartum period. It is associated with preeclampsia, pancreatitis, amniotic fluid emboli, and hypercoagulability. Presentation often consists of severe bilateral visual loss shortly after delivery, with widespread cotton-wool spots with or without intraretinal hemorrhage.

The visual prognosis is guarded, but retinal changes and symptoms may resolve spontaneously. Branch and central retinal artery occlusions, as well as retinal vein occlusions (although these are less common), have been reported in pregnancy, presumably secondary to amniotic fluid emboli or a hypercoagulable state.

Ocular Diseases Modified by Pregnancy

Diabetic retinopathy

DR developing during pregnancy may show a high-rate of spontaneous regression after delivery.

Factors that have been shown to influence the progression of DR in pregnancy include, the pregnant state itself, duration of diabetes, degree of retinopathy at time of conception, metabolic control of diabetes, and the presence of co-existing hypertension.

Diabetic women in child-bearing age should be counseled regarding the risk of development and progression of DR. The risk of retinopathy progression during pregnancy is higher in patients with inadequate glycemic control, thus, whenever possible, tight glycemic control should be attained before conception.

Patients with severe NPDR or proliferative DR (PDR) are at a higher risk of progression during pregnancy thus, it is advisable to postpone conception until stabilization of their ocular disease.

Diabetic patients with PDR during pregnancy should be managed the same way as non-pregnant patient. However, retinopathy level should be monitored closely and treatment initiated early once indicated. Guidelines for screening of diabetic women include, an ophthalmic evaluation before conception and then again in the first trimester. Subsequent examination depends on the level of retinopathy. Women with gestational diabetes are not at an increased risk of DR and thus, don’t need to be examined under these guidelines.

Glaucoma

It was mentioned earlier that IOP decreases during pregnancy as part of normal physiologic changes. During pregnancy women with ocular hypertension demonstrate a similar decrease in IOP that becomes notable during the second trimester and decreases further with advancing pregnancy.The decrease in IOP during pregnancy is likely multifactorial.

Systemic Disease with Ocular Complications

Systemic diseases with ocular complications occurring during pregnancy are either specific to the pregnancy itself such as the eclampsia/pre-eclampsia complex, and Sheehan syndrome, or DIC.

Sheehan syndrome

One of the most common causes of hypopituitarism in the developing countries is an ischemic necrosis of the pituitary gland due to severe postpartum hemorrhage. It is considered a potentially visually-threatening disorder as a result of sudden increase in pituitary size from infarction or hemorrhage. It may present as a sudden onset of headache, visual loss, and/or ophthalmoplegia.

VF defect presents in 64% of cases and visual acuity (VA) abnormalities present in 52% of cases. VF defect results from upward expansion of the tumor, which compresses the optic chiasm, optic tracts, or optic nerve. The classic VF defect is a bitemporal superior quadrantic defect.

Ophthalmoplegia occurs in 78% of cases. It results from compression of the cavernous sinus, which makes cranial nerves III, IV, and VI vulnerable to injury. Oculomotor nerve is involved the most commonly, resulting in a unilateral dilated pupil, ptosis, with inferiorly and laterally deviated globe

Cranial nerve IV is also involved resulting in vertical diplopia. The sixth cranial nerve is least commonly involved, perhaps because of its sheltered position in the cavernous sinus. Its involvement produces horizontal diplopia. Horner syndrome may develop from damage to the sympathetic fibers.

DIC

Is an acquired syndrome characterized by the systemic intravascular activation of coagulation There are several obstetric causes of DIC during pregnancy and postpartum.

 The choroid is the most common intraocular structure involved. Occlusion of the choriocapillaris by a thrombus lead to disruption of the overlying retinal pigment epithelium causing serous retinal detachment (SRD).