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central serous chorioretinopathy ( csc ) is a disease characterized by an idiopathic serous neurosensory retinal detachment secondary to leakage from the retinal pigment epithelium ( rpe ) . from eighty to ninty percent of csc regresses
spontaneously over several months , but recurrence is observed in 33% to 50% of eyes [ 1 , 2 ] . in spite of the many studies of csc , there is continued controversy in the literature on the need , time , and method of treatment .    due to rapid developments in modern imaging methods , it is possible to better understand changes in the retina and their influence on functional results after resolution of subretinal fluid in csc .
spectral optical coherence tomography ( sd - oct ) enables a highly detailed in vivo evaluation of the individual retina layers , especially the external limiting membrane ( elm ) and the junction of inner and outer segments of photoreceptors [ 3 , 4 ] .
the development of sd - oct technology in recent years has resulted in various authors noting that persistent leaks and subretinal fluid may cause rpe alterations and photoreceptor changes , which may correlate with worse visual acuity [ 57 ] .   
the aim of the current study is to analyze the microstructural changes in the elm and photoreceptor layer before and after early and late conventional laser treatment for csc .
  a retrospective observational study included group a , 19 patients ( 19 eyes ) with symptomatic acute csc ( duration < 6 months ) and group b , 16 patients ( 16 eyes ) with symptomatic chronic csc ( duration  6 months ) .   
treatment was carried out with a slit - lamp - mounted green light laser ( iris gl medical , iridex corp .
, mountain view , ca , usa ) using a fundus noncontact lens volk 78 .
the parameters were spot size : 100200  m , time : 0.1  s , and mean power used : 110  mw ( 70140  mw ) minimal grey retinal discoloration . the power to deliver burn in the leakage side was determined by test spots in the superotemporal quadrant .
exclusion criteria were leakage side in the avascular zone < 500  m from the fovea , previous laser treatment , pdt , ttt or anti - vegf injection , any ocular diseases ( vascular diseases , diabetic retinopathy , retinal detachment , ocular inflammation , etc . ) , or use of corticosteroids .   
all patients were interviewed and underwent ophthalmologic examinations prior to treatment and 1 , 2 , and 12 months after laser treatment .
examinations included : bcva using standard snellen eye charts , intraocular pressure , anterior segment and fundus examination with volk 78d and 90d lenses ( volk optical inc . ,
mentor , oh , usa ) , and sd - oct analysis ( spectralis ; heidelberg engineering , heidelberg , germany ) with 3.9  m axial resolution and transverse resolution of 14  m . in each patient , we performed horizontal line scan through the fovea and made 19 b - scans on an area of 4.5  6  mm . in the experiment , we derived a medium value from three measurements performed for each patient .
we compared the manual measurement performed by 2 ophthalmologists , and the results did not differ more than 5  m and were repeatable .
additionally , fluorescein angiography was performed before laser treatment and 12 months after laser treatment .  
photoreceptor length was measured as the distance between the external limiting membrane ( elm ) and the most protruding outer segment of photoreceptors .
retinal thickness was measured as the distance between internal limiting membrane ( ilm ) and the most protruding outer segment of photoreceptors .
the value of subretinal fluid in the centre of the fovea was also recorded . in sd - oct , the fovea is recognized as the characteristic foveal depression where there is a lack of the following retinal layers : nerve fiber layer , ganglion cell layer , inner nuclear layer , and inner plexiform layer .  
statistical analyses were carried out using pearson product - moment correlation coefficient , friedman 's analysis of variance , cochran 's q test , fisher 's exact test , wilcoxon rank - sum test , and mixed - effects generalized linear models ( glms ) . all analyses were conducted using stata 12.1 special edition ( statacorp lp , college station , texas usa ) .
  in group a , the mean age of the 19 patients was 36.7  5.5 years .
the mean age of the 16 patients in group b was 48.8  8.0 years .
the mean visual acuity before laser treatment was 0.77  0.16 in group a and 0.51  0.20 in group b ( p = 0.0007 wilcoxon rank - sum test shows a statistically significant difference in visual acuity prior to treatment between group a and group b ) .
the visual acuity was correlated significantly with the subretinal fluid , upon its resolution , in group a only ( r = 0.50 , p = 0.0287 pearson product - moment correlation coefficient ) ; in group b , the respective correlation was not substantial ( r = 0.14 , p = 0.6062 ) .   
descriptive statistics on the following variables : length of the photoreceptors ( the distance between external limiting membrane ( elm ) and the most protruding outer segment of photoreceptors ) , retinal thickness ( the distance between internal limiting membrane ( ilm ) and the most protruding outer segment of photoreceptors ) , and subretinal fluid in the centre of the fovea ( measured before laser treatment 1 month and 12 months after laser treatment ) are shown in table 1 .
hyperreflective subretinal deposits in 3 eyes in group a and in 14 eyes in group b demonstrated a noticeable bulge in the rpe before treatment ( p < 0.0001 fisher 's exact test ) .   during the first follow - up examination , one month after laser treatment , 16/19 eyes in group a showed complete absorption of subretinal fluid whereas 11/16 eyes in group b showed residual subretinal fluid ( p = 0.004 fisher 's exact test ) .
two months after laser treatment , all eyes in group a ( 19/19 eyes ) showed complete absorption of subretinal fluid , whereas 2 eyes in group b showed residual fluid ( p = 0.19 fisher 's exact test ) .   
one month after laser treatment , hyper - reflective subretinal deposits in 3 eyes in group a demonstrated a noticeable bulge in the rpe .
however , after 12 months , the rpe was flat in all eyes ( figure 1 ) . in group
b , hyper - reflective subretinal deposits demonstrated a noticeable bulge in the rpe in 14 eyes at 1 month after laser treatment which still persisted in all of those eyes after 12 months ( p < 0.0001 fisher 's exact test ) ( figure 2 ) .   
twelve months after laser treatment , no patients in group a had noticeable photoreceptor and elm defects ( figure 1 ) , but 15 eyes in group b presented photoreceptor and elm defects ( p < 0.0001 fisher 's exact test ) ( figure 2 ) .   
twelve months after laser treatment , no patients in group a had noticeable subretinal fluid , but 2 eyes in group b showed residual fluid ( p = 0.19 fisher 's exact test ) .
the subretinal fluid absorption varied significantly over time ( before laser treatment and one month and 12 months after laser treatment ) in both investigated groups ( p < 0.0001 in group a , and p = 0.0001 in group b , cochran 's q test ) .
however , the laser treatment was to be more effective , in the context of subretinal fluid absorption , in group a in comparison to group b ( p = 0.0010 mixed - effects glm ) .
no recurrence was found in either group a or b. no complications were detected in group a. however , 12 months after laser treatment , cnv developed in 1 eye in group b. changes in the length of the photoreceptors and subretinal fluid took place in a very similar pace and direction , both in group a and in group b ( table 1 ) , except for the retinal thickness , where fluctuations were more distinct in group a compared to group b ( p = 0.0132 mixed - effects glm ) , and the visual acuity  a larger improvement was observed also in group a versus group b ( p < 0.0001 mixed - effects glm ) .   at the final follow - up visit , 12 months after laser treatment , the mean visual acuity in group
a was 0.94  0.09 and 0.71  0.17 in group b ( p < 0.0001 wilcoxon rank - sum test ) .
there was a fitted model in which the visual acuity played the role of dependent variable , and repeated measures ( before laser treatment and one month and 12 months after laser treatment ) , group a versus group b along with the length of the photoreceptors , subretinal fluid , and retinal thickness were set as the independent variables .
apart from the above - mentioned noticeable changes over a 12-month follow - up and between - group differences , the improvement of visual acuity was determined in both examined groups by appropriate retinal thickness ( p = 0.0101 mixed - effects glm ) and observed diminution of the length of the photoreceptors ( p = 0.0266 mixed - effects glm ) .
  analyzing and comparing the results from both groups of patients ( acute and chronic csc ) prior to laser therapy did not reveal significant differences in the thickness of the retina , elevation of neurosensory retina , or microstructural changes of the retina .    during the 12 months of observation after laser treatment , subretinal fluid
when analyzing the photoreceptor layer in detail , defects were noted after laser treatment in 93% of eyes with chronic csc but not noted in any case with acute csc at the final examination .
defects in the photoreceptor layer conditioned visual acuity , which was statistically better after laser treatment in the group with acute csc in comparison to the chronic csc .
analysis of these results supports other authors , according to whom if subfoveal fluid persisted more than 4 months foveal atrophy may occur anytime , and degenerative changes often develop in the macula in csc cases lasting longer than 6 months ; these changes correlate with visual acuity .
we also observed that retinal thickness and subretinal fluid correlated significantly with visual acuity 12 months after treatment only with chronic csc .   analyzing the length of the outer layer of photoreceptors before laser treatment in the acute and chronic csc groups ( no significant differences existed between these groups ) showed its elongation in relation to healthy eyes , as previously reported by matsumoto et al . .   
damage to the photoreceptor layer in patients with chronic csc was found only after laser treatment and absorption of subretinal fluid .
it was not possible to evaluate any irreversible changes that had already occurred in the photoreceptor layer during active csc .
elongation of the outer segments of photoreceptors may be due to a lack of photoreceptor phagocytosis by the rpe , while the duration of the elongation of this layer may affect the simultaneous initiation of photoreceptor apoptosis .
spaide hypothesized that increased autofluorescence may represent an photoreceptor outer segments phagocytized by the rpe .
one month after laser treatment , only 3/18 eyes in the acute csc group had hyper - reflective subretinal deposits ( which were no longer present at the 12-month followup ) .
therefore , photoreceptor outer segment phagocytosis by rpe does not seem prevalent at the onset of csc .
however , subretinal precipitates , indicating phagocytosis , were found in 13/15 eyes in chronic csc one month after laser treatment ( and were still present at the 12-month followup ) .
furthermore , photoreceptor defects were found after laser treatment in 93% of eyes with chronic csc indicating photoreceptor apoptosis .
these facts suggest that both findings develop after the patients have had csc for some time .
thus , a benefit of laser therapy for acute csc may be that it limits the process of outer segment photoreceptor phagocytosis and apoptosis , which correlates with better visual acuity in the acute csc patient group ( p < 0.0001 ) .
  in summary , microstructural changes of the retina shown in sd - oct during active csc show no statistically significant correlation to the duration of the disease .
however , after laser treatment subretinal fluid absorption takes less time in patients with acute csc .
photoreceptor and elm defects were found in most patients with chronic csc ( p < 0.0001 ) .
damage of the photoreceptor layer and elm in patients with chronic csc was found only after laser treatment and the absorption of subretinal fluid .
an effect of these factors is that early laser treatment for csc results in better visual acuity than late laser treatment ( p < 0.0001 ) .
early laser treatment may cause early resolution of csc , which may prevent situations in which about 10%20% of eyes did not heal spontaneously [ 1 , 2 ] .
purpose . to analyze microstructural changes in the external limiting membrane ( elm ) and photoreceptor layer before and after early and late conventional laser treatment in central serous chorioretinopathy ( csc ) in 12 months follow - up study 
 . methods . 
 a retrospective observational study included group a : 19 patients ( 19 eyes ) with symptomatic acute csc and group b : 16 patients ( 16 eyes ) with symptomatic chronic csc . 
 retinal microstructural changes were analyzed with sd - oct paying a particular role in examining the photoreceptor layer and elm . results . 
 the length of the photoreceptors , prior to treatment , was approximately 84  m in group a and 82,5  m in group b. twelve months after laser treatment , photoreceptor length was approximately 49  m in group a and 43  m ( range 2055  m ) in group b. no patients in group a had noticeable photoreceptor defects nor elm defects , but in 15 eyes in group b photoreceptor and elm defects were detected ( p < 0.0001 ) . 
 conclusions . 
 when analyzing the photoreceptor layer and elm during active csc , it is not possible to evaluate any irreversible changes which have already occurred in this layer . 
 damage to the photoreceptor layer and elm in patients with chronic csc was only found after laser treatment and the absorption of subretinal fluid .