Fundus Autofluorescence in Central Serous Chorioretinopathy
Carsten Framme
Central serous chorioretinopathy (CSC) is a common retinal disease characterized by an idiopathic flat retinal detachment within the macula (1,2). It typically affects young and middle-aged adults between 20 to 50 years of age and often reveals a shallow, round, and serous detachment of the neurosensory retina; however, small detachments of the retinal pigment epithelium (RPE) may also occur (2). Primarily male patients (male:female ratio about 10:1) are affected and typically a type-A behavior in these patients can be observed. Moreover, emotional stress frequently accompanies the visual disturbances. CSC has also been associated with vasoconstrictive agents, endogenous hypercortisolism, and systemic corticosteroid use (3).
When the serous detachment involves the foveal region, patients become symptomatic and usually complain about blurred vision, scotoma, micropsia, or metamorphopsia. This can easily be detected by Amsler Grid testing. Decreased visual acuity can be improved by the addition of small hyperopic correction, focusing the light bundles to the detached central region. Of interest, visual acuity remains largely preserved despite the prolonged separation of the neurosensory layer from the RPE. The long-term visual prognosis for most patients is excellent and improvement can usually be achieved without specific treatment. However, about 20% to 30% of patients will have one or more recurrences, and a small percentage (about 5%) will develop choroidal neovascularization or chronic detachment with cystoid macular edema from this condition (4,5). Chronic forms of CSC are characterized by multiple sites of prolonged and recurrent serous retinal detachments in one or both eyes, and are particularly seen in Latin and Oriental people (5). Such patients may be asymptomatic for a prolonged time if the localized areas of retinal detachment are outside the foveal area. On biomicroscopy, multiple areas of RPE atrophic tracts, particularly in the inferior site of the macula and in the peripapillary regions, are observed (6,7). Angiography then reveals multiple sites of staining that correspond to the areas of RPE atrophy; however, no significant leakage is observable in these areas. Even though in these patients the macula is usually attached, the photoreceptors are chronically damaged due to previous long-term dysfunction. Thus, these patients usually suffer from significant loss of vision and paracentral visual field defects. In the case of chronic detachment, lipid exudates and cystoid macular edema may occur, complicating the disease (5). Whereas focal laser photocoagulation is recommended in acute CSC if no resolution of exudates appears after 4-6 weeks, in the atrophic stages of the disease no treatment can be offered. However, in chronic recurrences with prolonged or repetitive serous retinal detachments, laser photocoagulation can improve the visual course. A faster resolution of the edema and a faster rehabilitation of visual acuity are then observable; however, there is often no substantial benefit with regard to visual acuity following laser photocoagulation. Usually laser treatment is directed to the site of leakage. Laser therapy induces damage of the RPE layer with migration and proliferation of neighboring RPE cells to cover the
defect, resulting in a restoration of the outer blood-retina barrier (8, 9, 10). As a result of this biologic tissue reaction from the laser photocoagulation, the neurosensory retinal detachment disappears and the visual acuity recovers.
defect, resulting in a restoration of the outer blood-retina barrier (8, 9, 10). As a result of this biologic tissue reaction from the laser photocoagulation, the neurosensory retinal detachment disappears and the visual acuity recovers.
PATHOLOGY OF CSC
In contrast to the well-defined clinical appearance of CSC, a clear understanding of the exact pathogenesis of accumulation of subretinal fluid is lacking. It is widely accepted that the origin of the subretinal fluid is the choroid. Because of a defect in the RPE layer, choroidal fluid enters the subretinal space and leads to the detachment of the neurosensory layer (1). CSC was induced in monkeys by repeated injections of epinephrine (11). Histologic examination of the monkeys’ eyes revealed focal RPE degeneration and endothelial cell destruction in the underlying choriocapillary layer (12). This supports the gen erally adopted opinion that the RPE plays a crucial role in the development of CSC. Measurements of the metabolic activity of RPE cells also revealed significant changes in CSC (13). The cause of the focal leak is unclear. It was initially proposed that a simple breakdown of the RPE layer is responsible for the leak (14). Later, the theory of pathologically hypersecreting RPE was proposed (15); however, this did not explain the observation of widespread hyperpermeability in the areas of neurosensory detachment seen with indocyanine green (ICG) angiography (16,17). In fact, ICG suggested impaired choroidal circulation as a cause of CSC by showing delayed choroidal capillary filling in areas of hyperpermeability (18). It was proposed that localized capillary and venous congestion in distinct areas leads to ischemia, increased choroidal exudation, and a focally hyperpermeable choroid. Because of this excessive choroidal fluid extravasation, the RPE detaches and after further accumulation of fluid, breaks within the RPE appear, allowing the fluid to create a neurosensory retinal detachment (19). However, earlier but limited histopathologic examinations in humans showed no abnormalities in the choriocapillaris underlying the RPE detachment (20). On the other hand, it was noted that the gray-white exudates contained fibrin, which was taken as evidence that serum proteins escaped from the choriocapillaris. This supports the hypothesis that a focal increase in the permeability of the choriocapillaris is the primary cause of damage to the overlying RPE leading to distinct breaks and subsequent neurosensory detachment (2,5).
IMAGING TECHNIQUES IN THE DIAGNOSIS OF CENTRAL SEROUS CHORIORETINOPATHY
Biomicroscopy
The diagnosis of CSC is primarily clinical and usually confirmed by angiography. Biomicroscopically, and best seen with a narrow light beam from the slit-lamp, a well-defined round or oval area of shallow elevation of the retina, which usually presents a slightly darker color than the surrounding normal retina (5), can be observed. The detached retina is usually transparent and of normal thickness, and the subretinal fluid is also usually clear; however, sometimes gray-white serofibrinous exudates can be seen. Because of the retinal detachment, the visibility of the xanthophyll pigment within the center of the fovea may be enhanced, presenting as a central yellow spot. Also, through gravity, the subretinal fluid often pools inferiorly within the area of retinal detachment (5). Sometimes small dot-like deposits on the inner side of the retina
or on the RPE surface within the detached area can be seen, most likely representing protein precipitates (2).
or on the RPE surface within the detached area can be seen, most likely representing protein precipitates (2).
Fluorescein Angiography
Fluorescein angiography (FA) plays an important role in the evaluation of CSC. It is used to detect the distinct site of one or more RPE breaks and to determine the amount of leakage, which can be very heterogeneous. Thus, some patients reveal only small detachments and less angiographic leakage, whereas others present with large detachments and heavy leakage. In FA, usually the dye from the choroid leaks through the focal RPE defect and pools in the subretinal space. In more than 95% of patients with CSC, at least one leaking point can be seen. Typically, the dye spreads symmetrically in the subretinal space but does not extend outside the borders of the detachment. Sometimes the classic “smokestack phenomenon” can be observed showing the dye percolating upward in the subretinal space with subsequently pooling into the whole space. This pattern, first described in 1971 (21), is thought to result from an osmotic pressure gradient generated by differences between the protein concentration of the subretinal fluid under the detachment and the fluorescein dye entering the detachment (13).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
