Our study sought to reveal the amount of functional and morphological damage present after long-standing CSCR. Thus far, the medical literature on the subject concentrates predominantly on discussing the effects of treatment of CSCR. [15,16,17,18,19] Previous authors have suggested varying amounts of reduction of retinal edema and improvement in BCVA; however, the final results usually include cases with insufficient responses to SMPLT—that is, patients with persisting SRF—as well. Moreover, final CRT and BCVA values were not referred to the measurements in healthy individuals. Our study analyzed patients after complete resolution of their CCSCR and correlated its findings with the characteristics of healthy individuals. In this manner, our study provides a clear picture of visual acuity deficit and retinal thinning after CCSCR.
The exclusion of a large group of patients with completely resorbed SRF after CCSCR might be a problem. This disease has a long course with remissions and recurrences, so it is difficult to find a point at which reliable measurements can be performed. In our study, we chose a group that responded well to SMPLT. As patients were followed up with every two months, it was possible to identify any points of remission and to obtain BCVA and OCT measurements.
Other studies that have employed SMPLT in the treatment of CSR usually have concentrated on an improvement in BCVA and the reduction of CRT. [15,17,18,19, 20,21,22] Final BCVA is usually given as an average value of the whole cohort of patients, which is composed of both responders and nonresponders.
Koss et al. reported a final BCVA of 51.6 ± seven letters on the ETDRS grid (equivalent to 0.7 logMAR), [23] while Malik et al. reported a final BCVA of 45.5 ± 12 letters (0.8 logMAR), [19] Scholz et al. reported a final BCVA of 0.3 ± 0.25 logMAR,[16] and Kim et al. reported a final BCVA of 0.04 ± 0.06 logMAR. [18] However, we have to remember that these scores might be downplayed, as they include nonresponders with poorer BCVA values.
In our study, final BCVA after chronic CSCR was significantly reduced to 0.23 ± 0.18 logMAR (0.6 Snellen), which signals a loss of approximately four lines of Snellen visual acuity. This visual defect, if unilateral, can be compared with moderate anisometropic amblyopia. Affected patients may have peripheral stereopsis, which enables normal everyday activity; however, more demanding visual tasks have to be conducted with the use of the unaffected eye.
BCVA in the study group improved by 0,11logMAR only and this outcome remains in consent with the results of other studies. [16, 18, 19, 23] Scholz et al. in their meta-analysis of results of SMPLT in CCSCR from 14 studies (216 patients) report similar mean BCVA improvement of 6.34 ETDRS letters (range –15 to 20).[24] Relatively poor rate of visual improvement in CCSCR is also noted with other treatment modalities. BCVA gain in the treatment of chronic CSCR with photodynamic therapy (PDT) is similar to SMPLT, usually at the level of a few ETDRS letters or 1 Snellen line. [25, 26, 27] Few studies however, show larger amount of BCVA improvement after PDT. [28,29] Those inconsistences may be a consequence of different characteristics of the study groups, especially in regard to the duration of the disease and baseline visual acuity. Studies directly comparing SMPLT and PDT in the treatment of chronic CSCR generally do not favor any of these therapies and reveal moderate BCVA improvement (a few ETDRS letters) similar in both groups [30, 31, 32]. Only large PLACE trial shows significantly better morphological results with PDT treatment and moderately better visual outcome compared to SMPLT ( + 6.78 ETDRS letters versus +4.48 ETDRS letters at 7 months). Vision related quality of life, however was the same in both groups. [33]
Therapy with mineralocorticoid inhibitors (eplerenone) if effective at all, brings similar functional benefits as SMPLT and PDT. Meta-analysis of 5 randomized control trials evaluating efficacy of eplerenone treatment in CCSCR revealed just 0.1logMAR difference in BCVA between patients treated and receiving placebo at two months. [34].Most of the studies of that subject show moderate BCVA improvement, usually by less or about 0,1logMAR. [35,36,37]
Laser photocoagulation is of limited use in chronic CSCR as it requires the leakage point to be located outside the fovea. In CCSCR usually we approach a variety and multiplicity of symptoms that include subretinal fluid, pigment epithelial detachment and alterations of the retinal pigment epithelium, often without well demarcated leakage points. In performed clinical trials, laser photocoagulation in CSCR did not influence visual outcome in the long term. [38] Moderate BCVA improvement can be achieved in selected cases with navigated laser photocoagulation. [39]
Most of the studies report mean retinal thickness values after SMPLT that include also patients with retinal edema, so the numbers are potentially higher and do not reflect actual retinal thinning.
We found that the central retina in the study group measured 225.19 ± 33.8 µm in the foveal part, which was on average 39.32 µm thinner than the same areas in the controls. Retinal thinning in the fovea after resorption of SRF is less if the retina is generally thicker in the macular area prior to treatment (i.e., if the patient has higher CRTA and CV values); in other words, there exists a positive correlation. Retinal thinning in chronic CSCR has been confirmed by other studies; for example, Breukink et al. reported progressive retinal thinning of 15.1 µm per year in patients with chronic presence of SRF. However, these authors did not present final CRT values. [40]
Interestingly, in our study, parts of the central retina outside the fovea were not that significantly affected. Average thickness and volume values of the central part of the retina did not vary significantly from the measurements taken in healthy individuals. Probably, the presence of SRF affects mainly the thinnest and very central part of the retina, which has only one source of blood supply: the choroid. As we already know, it is the choroid that is the primary location of the lesion that underlies the pathogenesis of serous chorioretinopathy. Disturbance of choroidal perfusion in this area affects also the outer retina and photoreceptors, at which point, loss of the RPE and photoreceptors subsequently occurs, which explains the functional damage.
Our OCTA findings seem to confirm our hypothesis. Our patients showed impaired choroidal perfusion at the level of the choriocapillaries after long-term chorioretinopathy despite remission of the disease.
The existing medical literature confirms choroidal flow disturbances in active CSCR. Rochepeau et al. and Cakir et al. analyzed choroidal perfusion in CSCR and revealed the existence of decreased blood flow at the level of chioriocapillaries in the active stage of the disease. [41,42] Perfusion improved with the resorption of SRF. Matet et al. presented similar results [43]; disturbances of choroidal perfusion in their study increased with patient age, duration of CSCR, and disease severity. The choriocapillaries showed thinning and larger choroidal vessel dilation at the affected sites. Decreased density of the choriocapillaries in CSCR was also noted by Cardillo et al. [44]
An analysis of our findings proves that chronic cases of CSCR present with choroidal flow disturbances even after the absolute cessation of symptoms. All of the resolved cases of chronic CSCR in our study showed an impairment of the flow signal at the level of the choriocapillaries. Focusing on the resolved cases is a novel protocol in comparison with in other studies, which largely covered defects of choroidal flow in OCTA of patients with the active form of the disease. [45]
Choroidal vasculature alterations are rarely reported in the literature after other treatments in CCSCR. Toto et al. did not find any changes in retinal capillary plexuses or choroidal vasculature after eplerenone treatment of CSCR. [46] Fujita et al. presented a small series of 6 patients in whom OCTA revealed choriocapillaries recovery after half-dose PDT treatment (improvement of flow signal). [47] Similar effect was observed by Xu et al. [48] Definitely more research is needed to more precisely assess vascular changes in the course of treatment of CSCR. That will certainly happen with development of OCTA angiography technique and software.
The present study did not find any correlation between patient age, duration of symptoms, or baseline retinal morphology and final visual acuity after remission of symptoms. Also, final central retinal thickness, a morphological parameter that was significantly affected by the disease (retinal thinning), did not correlate with the duration of the disease.