Choroidal Findings in Systemic Disorders

Pregnancy

Pregnancy induces various ocular changes, including visual changes, ocular blood flow, fall in intraocular pressure, and an increase in curvature and central cornea thickness. During pregnancy, there may be an increase of pregnancy-related fluid retention in the choroid, causing increased choroidal thickness in normal pregnant women than in normal nonpregnant women, particularly in the second trimester.

Preeclampsia

Preeclampsia is an obstetrical complication affecting multiple systems, characterized by placental ischemia, systemic inflammation and vascular changes that causes widespread vasoconstriction, new onset systemic hypertension and proteinuria. Complications of severe preeclampsia are cerebral or visual disturbances, impaired liver function, pulmonary edema, and thrombocytopenia. Subjective visual disturbances are reported in 40% of women with preeclampsia.

The systemically increased vasospasm in preeclampsia causes choroidal vascular spasm, resulting in decreased choroidal thickness in preeclampsia as compared to normal pregnant women. The choroidal thickness in women with preeclampsia may be comparable to that of normal nonpregnant women.

Diabetes Mellitus

Diabetes mellitus is primarily a vascular disease, and its complications can be divided into macrovascular and microvascular abnormities. In diabetes, other than changes in retinal blood flow, the changes in choroidal vasculature may play a vital role in the pathogenesis of diabetic eye disease. Various choroidal abnormalities have been reported in studies on diabetics, including choroidal neovascularization, choroidal vascular degeneration, obstruction of the choriocapillaris, choroidal aneurysms, and increased tortuosity and narrowing of the choroidal vessels.

Many studies have been done with regards to choroidal thickness in diabetes, but results have been varied. One study did not find any significant difference in the mean choroidal thickness between their controls and diabetic patients. Another study reported similar choroidal thickness between their controls and nonproliferative diabetic retinopathy. Meanwhile, two studies showed that patients with diabetes mellitus had significantly thinner choroid than nondiabetics regardless of their diabetic retinopathy status. In contrast, another study showed that early diabetic retinopathy patients had thinner choroid compared to nondiabetics, but it progressively thickened with increasing severity of diabetic retinopathy. In the Beijing Eye Study, choroidal thickness was measured in 246 subjects with diabetes mellitus. The study found that there is increased choroidal thickness in subjects with diabetes, and no association between the presence and severity of diabetic retinopathy and the change in subfoveal choroidal thickness. Due to controversial reports, the effect of diabetes on choroid is still not clear; other ocular parameters may be explored to understand the pathophysiology of diabetes mellitus in the choroid.

Hypercholesterolemia

Atherosclerotic changes may occur in the choroid due to its high blood flow. These changes occur in presence of hypercholesterolemia. A single study showed that there was significantly higher subfoveal choroidal thickness in subjects with hypercholesterolemia than in controls. Further studies need to be conducted to confirm this association and determine the possible mechanisms involved. It might be important to consider hypercholesterolemia while analyzing choroidal thickness.

Hypertension

Hypertension causes disease in vascular systems in the brain, heart, kidneys, and eyes. In the eyes, it can cause retinal hemorrhages, cotton wool spots, vessel closure in the retinal capillaries and choriocapillaris, and intraretinal lipid accumulation. Retinal and choroidal changes occur with hypertension; however, the pathophysiology behind choroidal changes remains unknown. A single study demonstrated a significant increase in subfoveal choroid thickness in patients with hypertensive retinopathy. This could be due to accumulation of interstitial fluid in the choroid because of choroid permeability changes. Hypertension is a possible determinant of choroidal thickness; however, further studies are required to confirm this finding.