In retinal medicine, there are big diseases and there are not-so-big diseases. The big ones are like superstar athletes: even people who aren’t fans of their sport have heard of them.
While it goes without saying that nobody is a fan of these (or any) diseases, they are nonetheless familiar to just about everybody. They are the Michael Jordan and Muhammad Ali of retina conditions, who most people familiar with ophthalmology have at least heard of, even if their work or experience have nothing to do with the macula, the retina, or any other part of the fundus.
The most widespread of retina conditions is the heavyweight champ, age-related macular degeneration, or AMD. It is rare to open (or click on) a magazine for ophthalmologists or attend a conference in the field without several different takes on the topic. Age-related macular degeneration is famous because it afflicts a lot of people, and a tremendous amount of hard work is done to treat those who suffer from it.
The next most famous is another name you’ve probably heard quite a few times, and in print and media is another superstar. You may have already guessed the second most common condition: diabetic retinopathy. Nearly as famous as AMD, diabetic retinopathy afflicts thousands of people each year, and is just about as widely known.
A bit further down the line, however, and the familiarity of retina conditions starts to taper off sharply. After diabetic retinopathy, the most common condition of the fundus is branch retinal vein occlusion, which probably isn’t on the tip of anybody’s tongue, unless they’re a retina specialist or they know somebody who suffers from it.
Just as uncommonly known, but nonetheless incredibly dangerous and important, is number four on the list: central serous retinopathy, or more specifically, central serous chorioretinopathy (CSC or CSCR). Though the condition is rare, and not entirely understood, it is nonetheless one that could do with more research and a wider sense of understanding.
Much of the time, when people are familiar with CSC, it is in connection with serous retinal detachment. While these two conditions can be related, they are in fact entirely separate, and can each occur entirely independent of one another.
To explore the correlation between these two conditions, it’s necessary to examine the characteristics of each, and explore how they can form a dangerous comorbid situation.
What is Central Serous Chorioretinopathy?
Although CSC is the fourth most common retina disease, it is nonetheless quite uncommon. It has an incidence of 9.9 per 100.000 in men and 1,7 per 100.000 in women. CSC is a form of macular edema, which is to say, it is a collection of fluid under the retina, specifically its center, the macula.
This accumulation of subretinal fluid occurs due to leakage from the choroid, the subfoveal layer of tissue located underneath the retina. The choroid tissue performs a number of different tasks within the eye: it contributes vascular supply to the outer retina, regulates the eye’s temperature, and modulates vascularization and growth of the sclera.
Due to its various supply and regulation functions, the choroid is typically rich with fluids. Between it and the retina is a membrane layer of cells, called the retinal pigment epithelium (RPE). It is due to a dysfunction in the RPE that central serous retinopathy occurs. When the RPE fails to contain the serous fluid within the choroidal vessels, the result is exudative flow of fluid into the retina by capillary action, often accumulating in the macula and in its very center, the fovea, where the highest concentration of neural receptors is located.
Typically the condition occurs only once and in one eye alone. Acute central serous chorioretinopathy is by far the most common form of the disease. However, chronic central serous chorioretinopathy does sometimes occur, particularly among individuals with compounding risk factors. Under these uncommon circumstances, an individual may subsequently develop CSC in the fellow eye as well as the original.
The pathogenesis of CSC is complex, and not well understood. For this reason it is sometimes known as idiopathic central serous chorioretinopathy. Correlations have been observed between the condition and other symptoms and comorbidities, but no causality has been definitively identified.
Patients with CSC frequently exhibit increased choroidal thickness, and this is often accompanied by choroidal neovascularization (CNV). High levels of the protein fibrin are often observed in the eyes of patients with CSC. While some have posited a connection between helicobacter infection and CSC, no link has been established between the two.
The use of corticosteroids is thought to be related to the development of CSC, and steroid use in any capacity—even common ones present in skin creams and nasal sprays—is considered to be a risk factor for the disease. This may be due to the increased level of cortisol in the bloodstream brought on by steroids, which can result in hyperpermeability of the choroid’s blood vessels, known as choriocapillaris.
Other varieties of vasculopathy have been linked to CSC as well. Hypertension, and even increased emotional stress are also believed to be risk factors. For this reason, it is believed that having a Type A personality can potentially be related to the pathophysiology of this condition.
At the onset of CSC, a patient typically notices a number of symptoms affecting their visual acuity, brought on by pressure upon the neurosensory retina. Patients often experience darkened or blurred central vision, or perhaps even scotoma, or blind spots in that vision. Straight lines can appear bent, nearby objects can appear far away, and colors can be changed or distorted. In extreme cases, partial or total vision loss may also occur.
Retinal Detachment and Central Serous Chorioretinopathy
CSC can cause the retina to detach from the fundus, in what is known as exudative retinal detachment. As pressure within the edema builds between the retina and the choroid, the retina can be dislodged from its position.
While the choroid and the retina are attached, they are only held together with a relatively fragile bond connecting to the retinal pigment epithelium. The position of the retina is maintained largely by the ocular pressure of the vitreous gel upon the limiting membrane that separates it from the retina.
When CSC occurs, there is the potential for a retinal tear or hole to develop as a result of the pressure. This constitutes a wholly separate problem with a number of treatment options, most commonly laser treatment to repair the tear.
When there is no breach in the retina’s structure, the pressure can sometimes continue to build, resulting in pigment epitheliopathy, or damage to the retina’s lower layer. This can eventually lead to severing of the bonds between the retina and the choroid.
When pigment epithelial detachment (PED) occurs in a situation where the vitreous is not of sufficient pressure to hold the retina in place, or the pressure of the edema caused by CSC is greater than that of the internal limiting membrane, the retina can become detached. Without rapid treatment, this can cause the retina to atrophy, and lead to permanent vision loss.
Divergence of Central Serous Chorioretinopathy and Retinal Detachment
Though CSC and retinal detachment can occur together, each is treated separately, in the same manner as if they had occurred independently of one another.
CSC is not the only cause of retinal detachment. In fact, exudative retinal detachment isn’t even the most common variety of retinal detachment.
Rhegmatogenous detachments are by far the most common kind, and are caused by a hole or tear in the retina that allows fluid to pass through and collect underneath the retina, pulling the retina away from underlying tissues. A third type, tractional retinal detachment, happens as a result of the tension placed on the retina by the formation of an epiretinal membrane.
In addition, CSC does not always result in retinal detachment. As previously mentioned, when the edema created by the condition results in a tear in the retina, the pressure that would otherwise cause CSC may be relieved, thus potentially alleviating the risk of a detached retina, though the retinal tear remains a serious issue.
Furthermore, CSC is not always so serious a condition. In fact, most of the time, it is a self-limiting condition, and the abnormalities in vision it causes simply go away of their own accord. Most patients experience a return to full visual acuity in a few months, and sometimes only in a matter of weeks.
Diagnosis and Treatment of Central Serous Chorioretinopathy
When CSC is severe enough that it requires treatment, or it does not go away on its own, ophthalmologists have a number of treatment options available at their disposal.
To begin, a number of diagnostic procedures common to all retinal conditions are used to identify the problem. Following the usual Amsler grid test, which measures a patient’s visual acuity, an ophthalmologist will typically perform spectral domain optical coherence tomography (SD-OCT) scan in order to achieve depth imaging of the subretinal space.
In addition, three other tests which make use of dyes in imaging are frequently performed in diagnosing retinal conditions. The stains left by these dyes can result in hyperfluorescence that makes irregularities easier to identify.
Fundus autofluorescence can sometimes be used to determine the advancement of retinal diseases by highlighting the presence of lipofuscin, a pigment which increases with retinal dysfunction.
Fluorescein angiography is another test that makes use of a dye, one which causes blood vessels in the retina to stand out under a special light. This can help identify damage to choroidal vessels and choroidal neovascularization.
The third such test, of particular use in diagnosing central serous chorioretinopathy, is indocyanine green angiography. This test uses a dye that lights up when exposed to infrared light. It produces images that show retinal blood vessels and the deeper, harder-to-see blood vessels behind the retina in the choroid.
Upon diagnosing CSC, doctors have a number of treatment options available, depending upon the severity of the condition. These include thermal laser treatments, oral medications and eye injections. Where retinal detachment has occurred, laser treatments can often be administered simultaneously to treat both conditions.
Numerous steroid hormone antagonist drugs have been tested for treatment of CSC, but with results that are mixed at best. Drugs such as eplerenone have shown positive effects in some cases, while in other case reports they have demonstrated no improvement when compared to placebo. Similar inconsistencies have been reported in anti-VEGF therapy trials.
One therapy whose application is growing more and more widespread in the treatment of CSC is photodynamic therapy (PDT). In this treatment, a drug called verteporfin is injected into the patient’s arm, where it travels through the bloodstream and into the eye. It is then activated by a low intensity laser, and it serves to repair damage to the blood vessels. Trials have shown verteporfin to be highly effective, even when administered at only a half dose.
Other laser therapies, including laser photocoagulation and micropulse lasers are used in other situations to repair damage to the retina caused by CSC. Again, these lasers can also be used to reattach a detached retina in a minimally invasive manner.
Recovery and Follow-Up
Though the better known retinal conditions — those superstars of the field, AMD and diabetic retinopathy — have no final cure, it is a relief to know that CSC is treatable, and sometimes does not even require treatment. While retinal detachment definitely requires treatment, it too is highly treatable, often without significant loss of vision.
Often, after being treated for either or both of these conditions, patients report a full recovery during follow-up visits to their ophthalmologist. And the news of a patient’s recovery is always better than the condition making the news.