Focal choroidal excavation (FCE) is an uncommon structural anomaly in the back of the eye, representing a specific type of indentation in one of its deeper layers. The identification of FCE is often incidental, discovered during routine examinations for other issues, as it frequently does not cause symptoms on its own.
Defining Focal Choroidal Excavation
To understand focal choroidal excavation, it helps to visualize the back of the eye. The retina is the innermost layer, responsible for capturing light. Beneath the retina lies the choroid, a network of blood vessels that nourishes the outer retinal layers. These layers normally lie flat, forming a smooth, curved surface.
A focal choroidal excavation is a localized depression or “divot” within the choroidal layer. Imagine a perfectly smooth layer of sand; an FCE would be like a small, isolated scoop taken out of it. This concavity occurs without any outward bulging of the sclera, the eye’s tough, white outer wall. The finding is most often seen in the macula, the central part of the retina responsible for sharp, detailed vision.
Ophthalmologists classify FCE into two primary types. In a “conforming” FCE, the retinal layers dip down to match the contour of the choroidal depression, with photoreceptor cells remaining attached to the retinal pigment epithelium (RPE). In a “non-conforming” FCE, a separation exists between the photoreceptors and the RPE, creating a small, fluid-filled space. This distinction helps in characterizing the feature and monitoring for changes.
Diagnosis and Imaging Techniques
The definitive diagnosis of focal choroidal excavation is made using Optical Coherence Tomography (OCT). An OCT scan is a non-invasive tool that uses light waves to capture high-resolution, cross-sectional images of the retina and choroid. This process provides a detailed, layered view of the tissues at the back of the eye.
The scan allows an ophthalmologist to see the distinct concave dip of the FCE in the choroid. With these images, a doctor can confirm the excavation’s presence, measure its dimensions, and classify it as conforming or non-conforming. This classification is done by assessing the relationship between the photoreceptor layer and the RPE.
While an FCE might be suspected during a routine dilated fundus examination, its subtle nature makes it difficult to confirm without this advanced imaging. Other techniques like fluorescein angiography can provide supplemental information, but OCT is the primary tool for diagnosis and monitoring.
Potential Causes and Associated Theories
The exact cause of focal choroidal excavation is not fully understood, but researchers have proposed several theories. The two main categories for its origin are congenital and acquired.
The congenital theory suggests that FCE is a developmental anomaly present from birth. This proposes the excavation forms from a localized malformation during the development of the choroid and RPE in the womb. This would explain why many FCEs are discovered in healthy eyes and remain stable for years.
The acquired theory proposes that FCE can develop later in life. One potential cause is localized inflammation (choroiditis) that leads to tissue atrophy and scarring. Another is traction from the vitreous, the gel-like substance filling the eye, pulling on the retina and choroid. FCE is also linked to the pachychoroid disease spectrum, a group of conditions involving an abnormally thick choroid.
Associated Conditions and Vision Impact
Many individuals with a focal choroidal excavation have normal vision and no symptoms. However, an FCE can be associated with other conditions that affect sight. Any visual disturbances are caused by these secondary complications, not the FCE itself.
One significant associated condition is choroidal neovascularization (CNV), the growth of new, abnormal blood vessels from the choroid. These fragile vessels can leak fluid or blood, damaging the macula. Symptoms of CNV include distorted vision (metamorphopsia), where straight lines appear wavy, or a sudden dark spot in the central vision.
Another condition is central serous chorioretinopathy (CSCR), which occurs when fluid leaks from the choroid and accumulates under the retina. This causes a small detachment and disrupts vision. Symptoms can include blurred or dim vision, a blind spot, or objects appearing smaller or farther away.
Management and Monitoring Approaches
For an asymptomatic FCE without complications, the standard approach is observation. Treatment is not directed at the FCE itself, but at monitoring for changes that could signal a vision-threatening complication.
Monitoring involves regular follow-up appointments with an ophthalmologist. During these visits, OCT scans are performed to assess the stability of the FCE and detect early signs of problems like CNV or CSCR. Comparing images over time allows the doctor to identify any changes, such as new fluid or abnormal blood vessels.
Patients are also encouraged to monitor their vision at home using an Amsler grid. This grid of straight lines helps a person detect new wavy lines or blind spots, which should prompt an immediate call to their eye doctor. If a complication like CNV arises, treatments such as anti-VEGF injections can be administered to manage it.