Objective To compare the optical coherence tomography (OCT) features of acute central serous chorioretinopathy (CSC) versus neovascular age-related macular degeneration (AMD), and to determine if OCT features can distinguish between these two entities.
Methods A retrospective, observational study of 50 eyes with CSC and 50 eyes with neovascular AMD. Stratus OCT line scans (5 mm) were reviewed for presence of subretinal/intraretinal fluid and retinal pigment epithelium detachment. The height of the fluid and detachments were measured using the OCT manual callipers, and the morphology of the highly reflective line was described.
Results Intraretinal fluid (IRF), pigment epithelial detachment (PED), irregularities, thickening and attenuation of the highly reflective line were more often associated with AMD. When present, the PED was significantly greater in AMD than CSC. Patients with CSC were more likely to have subretinal fluid (SRF), and when present, the SRF height was significantly greater in CSC. Patients CSC also had more hypertrophic outer retinal changes on OCT compared with AMD.
Conclusion Neovascular AMD and acute CSC have distinguishing features on OCT that may help clinicians to differentiate accurately between the two conditions primarily using OCT.
- neovascular AMD
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Although central serous chorioretinopathy (CSC) typically occurs in young healthy patients,1 this condition can be seen in older age groups.2 3 When the neurosensory retinal detachment typically seen in CSC occurs in older patients, this condition can be mistaken for neovascular age-related macular degeneration (AMD). It may be difficult to distinguish CSC clinically, especially from the occult form of neovascular AMD, since occult choroidal neovascularision (CNV) may have a similar angiographic appearance to CSC.4 A clinician may opt to wait for spontaneous resolution in such a case, which would point to the diagnosis of CSC; however, given the potential for treatment with anti-vascular endothelial growth factor (VEGF) therapies, prompt diagnostic decision-making becomes imperative. In the present study, we investigated whether optical coherence tomography (OCT) features can help us distinguish between neovascular AMD and CSC. To our knowledge, there has not been a head-to-head comparison of OCT features in these two diseases.
A retrospective, observational study was conducted using 50 eyes of 46 patients with neovascular AMD and 50 eyes of 47 patients with CSC seen between June 2004 and November 2006 at a private retinal consultant practice in New York City. Patients were initially screened consecutively based on diagnostic codes that indicated CSC and neovascular AMD. The charts were reviewed and only those that fulfilled our criteria for acute CSC and neovascular AMD were selected for the study. Acute CSC and neovascular AMD patients were defined as ones with typical slit lamp biomicroscopy and fluorescein angiography (FA) findings who presented with symptoms of less than 2 months' duration. The diagnosis of CSC was based on focal serous neurosensory detachment (NSD) or retinal pigment epithelium (RPE) detachment with leakage at the level of the RPE seen in FA that resolved spontaneously. Both classic and occult variants of neovascular AMD patients were included in the study. Patients with other chorioretinal disorders that can cause CNV or macular oedema, and those with chronic and recurrent CSC or prior treatment for CNV, were excluded.
Demographic information was collected including age, sex, past medical history and past ocular history. All patients underwent comprehensive ophthalmological examination, including best corrected Snellen visual acuity (VA), slit lamp biomicroscopy, colour fundus photography and FA. The Snellen VA measurements were converted to logarithm of the minimal angle of resolution (logMAR) for statistical analysis. Vertical and horizontal line scans (5 mm) of the affected macular region were performed with OCT (Zeiss Stratus OCT model 3000; Humphrey-Zeiss Systems, Dublin, California, USA) by experienced technicians. The OCT scans were evaluated by a trained investigator masked to the clinical diagnoses. Foveal thickness, subretinal and intraretinal fluid height, and RPE detachment height were measured using manual callipers after reconfiguring the scans with the retinal thickness analysis. Two-tailed Z test and Fisher's exact test were used to evaluate the significance of differences between the two conditions. In all statistical analysis, p<0.05 was defined as statistically significant.
The AMD patients were older than CSC patients (mean age±SD, 77±8 (range 60–93) vs 44±11 (range 25–69) years, respectively, p<0.0001). There was a predominance of men in the CSC group, but not in the AMD group (80% in CSC vs 49% in AMD, p<0.0017). Best corrected VA was significantly lower in AMD than CSC group (20/160 vs 20/50, respectively, p<0.0001).
The differences in the OCT findings are summarised in table 1. Intraretinal fluid (IRF) and retinal pigment epithelium detachment (PED) were significantly more common in AMD (figure 1). IRF was present in 92% of AMD patients versus 0% of acute CSC patients (p<0.0001). The mean IRF height was 282±35 μm. PED was present in 35% of AMD patients versus 10% of acute CSC patients (p<0.0038). When present, the PED height was significantly greater in AMD than CSC (354±35 μm in AMD vs 187±39 μm in CSC, p<0.002). On the other hand, patients with acute CSC were more likely to have subretinal fluid (SRF) (96%) than AMD patients (57%; p<0.0001), and when present, the SRF height was significantly greater in CSC (206±18 vs 161±19 μm; p<0.04). Foveal thickness was similar in both populations: 359±223 μm in AMD versus 373±149 μm in CSC, p<0.71.
There were several significant differences in the morphology of the highly reflective line. In the neovascular AMD patients, the highly reflective line was consistently and significantly irregular (71% in AMD vs 2% in CSC, p<0.0001), thickened (41% in AMD vs 0% in CSC, p<0.0001) and attenuated (31% in AMD vs 0% in CSC, p<0.0001) (figure 1). A visible splitting of the reflective line occurred in eyes with NSD in both AMD (33%) and CSC (46%, p<0.23)(figure 2). Although not significant, CSC patients tended to have more of what we called ‘hypertrophic outer retinal changes’ (HORC), which represent small bulges or bumps on either side of the optically empty space corresponding to NSD (12% in CSC vs 2% in AMD, p<0.06) (figure 3).
Neovascular AMD and acute CSC have distinguishing features on OCT that may help clinicians to differentiate accurately between the two conditions primarily using OCT. Compared with acute CSC, the presence of intraretinal fluid, large PEDs and alterations of the highly reflective line characterised by irregularity, thickening and attenuation was significantly more common in neovascular AMD. On the other hand, acute CSC was notable for having significantly more and larger subretinal fluid and hypertrophic outer retinal changes, but the highly reflective line remained regular in thickness and morphology.
In our study, intraretinal fluid was notably absent in the OCTs of acute CSC patients. Intraretinal cystic changes have been reported in eyes with CSC but only in chronic cases.5 It is not known why CSC patients rarely develop intraretinal fluid. In this study, PED was significantly more common in neovascular AMD compared with CSC. However, a recent study by a group in Japan found 63% prevalence rate of PED in acute CSC eyes, more common than previously reported.6 In our study, we suspect that small PEDs may have been missed by the two line scans in some CSC patients.
Patients with neovascular AMD demonstrated significant distortions of the highly reflective lines in their OCTs. Neovascular membrane complex in neovascular AMD at the level of RPE/choriocapillaris probably leads to changes observed in the highly reflective line. Thickening at this level, therefore, points to the presence of the fibrovascular membrane, and the disruption in the integrity of the retinal layers caused by the CNV leads to significant irregularity and attenuation of this line.7 8
The highly reflective line in OCT scans is believed to be composed of two lines, representing the photoreceptor inner and outer segments (IS/OS) junction and the RPE/Bruch's membrane/choriocapillaris complex.9 10 The ‘splitting’ of the reflective lines seen in patients with NSD further supports this anatomical interpretation. Fragments of the highly reflective line were easily traceable in our CSC patients (34% of the eyes with CSC, data not shown) compared with AMD eyes where the characteristic irregularity of the line blurred this delineation. The upper line, that is, the photoreceptor IS/OS junction, has been shown to reappear after its initial splitting and re-establish its proximity to the RPE layer with the resolution of the NSD, which may explain the good visual recovery in CSC patients.10 11
Findings similar to HORC seen in our CSC patients have been described previously. The bulges in the RPE layer may be associated with leakage points in active CSC.6 12 13 The bumps in the IS/OS junction layer may represent the shed disc membranes of the photoreceptor outer segments that occur with prolonged duration of detachment.9 11 14 15 These theories suggest that HORC may actually be a sign of chronic nature of the disease. Patient-reported history is often unreliable, and those who presented with acute symptoms of CSC may have had past episodes of CSC that resolved unnoticed due to its extrafoveal location. HORC may be a unique feature seen in OCT that is a hallmark for chronic SRF due to CSC, AMD or other causes.
Our study attempted to examine OCT features that can help to distinguish CSC from neovascular AMD. We have encountered numerous patients in an intermediate age range (55–70 years) with accumulations of submacular fluid and without frank haemorrhage that are difficult to diagnose with certainty. FA is typically not diagnostic in these circumstances. The OCT characteristics, especially the lack of disruption at the highly reflective line (CSC), presence of intraretinal fluid (AMD) and greater height of subretinal fluid (CSC) are distinguishing features that appear to be highly reliable.
Competing interests None declared.
Ethics approval This study was conducted with the approval of the Institutional Review Board within the research department of the Retina Associates of New York. The study complies with the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.