neovascular age - related macular degeneration ( namd ) is the leading cause of visual loss among the elderly population in developed countries [ 1 , 2 ] . before the introduction of intravitreal antivascular endothelial growth factor therapy for namd , only prevention for visual loss might have been achieved in a limited number of patients with different treatment options like laser photocoagulation and photodynamic therapy [ 37 ] . the introduction of bevacizumab ( full length antibody against vegf - a ) and ranibizumab ( fab part of antibody against vegf - a ) has led the vast majority of the patients to prevent the baseline visual acuity [ 816 ] . the pivotal multicenter studies with ranibizumab , like marina , anchor , pronto , excite , and catt , showed that ranibizumab is effective to prevent baseline visual acuity in up to 95% of the patients and is effective to make an improvement in visual acuity in up to 40% of the patients [ 913 ] . monthly ranibizumab treatment for namd was found to be effective in marina and anchor studies ; however , an attempt then aroused to decrease the injection numbers . therefore , studies like pronto and fusion were designed to evaluate the effectiveness of as - needed treatment regimens , and ranibizumab was found to be effective in the treatment of namd on as - needed treatment regimens [ 11 , 14 ] . catt study was designed to compare the outcomes of monthly and as - needed treatment regimens for both bevacizumab and ranibizumab . this study revealed that the visual acuity outcomes were similar for monthly bevacizumab versus monthly ranibizumab , monthly bevacizumab versus as - needed bevacizumab , and monthly ranibizumab versus as - needed ranibizumab . only monthly ranibizumab was found to be more effective than as - needed bevacizumab . optical coherence tomography ( oct ) is a noninvasive diagnostic device that provides cross - sectional images of the retina like ultrasound [ 17 , 18 ] . time - domain oct systems have a scan rate of 400  a - scans per second which allow an axial resolution of 810 microns , and spectral - domain oct systems have a scan rate of 20.00065.000  a - scans per second which allow an axial resolution of 37 microns and provide a three - dimensional view of the retina . although fluorescence angiography is the gold standard for the diagnosis and followup of retinal vascular diseases and namd for several decades , it was largely replaced by oct after the introduction of oct - guided , flexible treatment regimens for namd with anti - vegf agents [ 17 , 18 ] . in this study , we aimed to evaluate the activity of choroidal neovascularization with sd - oct in the namd patients who were on an as - needed treatment regimen with ranibizumab and were diagnosed to have an inactive choroidal neovascularization with td - oct and clinical examination one month after intravitreal ranibizumab injection . this prospective , comparative , cross - sectional study included 49 eyes of 49 consecutive namd patients who were on an as - needed treatment regimen with intravitreal ranibizumab ( ivr ) . the patients underwent ivr injections at beyoglu eye training and research hospital between march 2012 and april 2012 . approval for data collection and analysis was obtained from the ethics committee of the hospital , and written informed consent was provided from all patients . the methodology of the study was designed in accordance with the tenets of the helsinki declaration . the treatment regimen was as follows : for the first three months of treatment , all patients received monthly doses of ranibizumab 0.5  mg/0.05  ml . the patients were then examined monthly and were retreated if they met any of the following criteria : visual loss of 1 or more lines , new perimacular hemorrhage , evidence of cnv enlargement on examination or fluorescein angiography , any amount of persistent subretinal , intraretinal , or subretinal pigment epithelial ( subrpe ) fluid one month after an injection.the patients who had a diagnosis of namd , were currently on an as - needed treatment regimen with ivr , underwent an ivr injection a month ago , did not experience visual loss since the last visit , did not show any activity of cnv on fundus examination , and did not show any amount of subretinal , intraretinal , or subretinal pigment epithelium ( subrpe ) fluid on td - oct were included in the study . the patients were not included in the study if the quality of the oct scans were not sufficient with any of the td - oct or sd - oct devices . visual loss of 1 or more lines , new perimacular hemorrhage ,   evidence of cnv enlargement on examination or fluorescein angiography , any amount of persistent subretinal , intraretinal , or subretinal pigment epithelial ( subrpe ) fluid one month after an injection . data collected from the patients ' records included age , gender , central retinal thickness defined by td - oct and sd - oct , the fluid type revealed by sd - oct , and the vitreoretinal surface abnormalities revealed by td - oct and sd - oct . all patients underwent a standardized examination including measurement of bcva via the early treatment diabetic retinopathy study ( etdrs ) chart at 4 meters , slit - lamp biomicroscopy and fundus examination , and measurement of intraocular pressure ( iop ) via applanation tonometry . fundus photography , and optical coherence tomography ( oct ) imaging with td - oct ( stratus oct tm ; carl zeiss meditec inc . , dublin , ca , usa ) and sd - oct ( spectralis ; heidelberg engineering , heidelberg , germany ) were performed . time - domain oct imaging was performed via stratus oct 3000 ( carl zeiss , meditec inc . , dublin , ca , usa ) . fast macular thickness map ( fastmac ) protocol was used to obtain the retinal scans , within a scan time of 1.9 seconds , which acquires six evenly spaced 6-millimeter ( mm ) radial lines , each consisting of 128  a scans per line , intersecting at the fovea ( total of 768 sampled points ) . the crt was defined as the distance between the internal limiting membrane ( ilm ) and the photoreceptor junction of the inner and outer segments via the automatic analysis package of stratus oct . spectral - domain oct imaging was performed via spectralis oct ( heidelberg engineering , heidelberg , germany ) . fast macula protocol was used to obtain the retinal scan , with a automatic real time ( art ) mean value of 9 , which acquires 25 horizontal lines ( 6  6  mm area ) , each consisting of 1024  a scans per line . the crt was defined as the distance between the ilm to the outer border of the retinal pigment epithelium via the automatic segmentation algorithms of the spectralis software . the main outcome measure of the study was the rate of the patients who had any amount of subretinal , intraretinal , or subrpe fluid on sd - oct and who were diagnosed as inactive after clinical examination and td - oct imaging . the secondary outcome measures were the crt values defined via the two devices and the ability of detecting vitreoretinal surface disorders via the two devices . for the statistical analyses , the mean ( sd ) of the differences was calculated . independent sample t - test was used to compare continuous parameters between the two devices , and chi - square test was used for nominal parameters . statistical analyses were made using commercially available software spss version 16.0 ( spss inc . , chicago , il ) . 29 patients ( 59.2% ) were female and 20 patients ( 40.8% ) were male . mean crt of the patients via td - oct was 218.1  51.3 microns ( range 139418 microns ) , and the mean crt via sd - oct was 325.7  78.8 ( range 222508 microns ) . the mean ratio between the mean crt measured with sd - oct and crt measured with td - oct was 1.51  0.09 .   as the patients who did not show any amount of subretinal , intraretinal , or subrpe fluid in td - oct were the subjects of this study , any kind of retinal fluid was not detected in td - oct . however , 16 of the 49 patients ( 32.6% ) showed subretinal , and/or intraretinal , and/or subrpe fluid on sd - oct . in detail , 8 patients showed ( 16.3% ) subretinal fluid , 10 patients ( 20.4% ) showed intraretinal fluid , and 3 patients ( 6.1% ) showed subrpe fluid ( table 1 ) ( figure 1 ) . the ability of the two devices in detecting vitreoretinal surface abnormalities was summarized in table 2 . since the introduction of the sd - oct , the resolution of retinal scans and parallelly our diagnostic ability increased . many studies compared the td - oct and sd - oct systems in regard to the fluid detection , and retinal thickness measurements [ 1723 ] . in previous studies the , oct devices were usually compared in patients having had namd , diabetic macular edema , and retinal vein occlusion [ 1723 ] . however , these studies mostly evaluated the ability of these devices in detecting subretinal , intraretinal , or subrpe fluid and compared the crt measurements between them [ 1721 ] . in this study we delineated the namd patients who were diagnosed to have an inactive cnv via the td - oct and clinical examination , and then we evaluated them with the sd - oct in order to detect the additional sensitivity provided via the latter device . the additional sensitivity of the sd - oct was 32.6% in regard to cnv activity . in a study by kakinoki et al . , the macular thickness in diabetic macular edema measured with td - oct and sd - oct were compared . the macular thickness values were well correlated ; however , the mean macular thickness detected with the sd - oct was reported to be 45 microns thicker than the td - oct . compared two different sd - oct devices with td - oct in patients with macular edema secondary to diabetic retinopathy and retinal vein occlusion . the macular thickness values detected with both sd - oct devices were also found to be higher than the values detected with td - oct . eriksson et al . showed that sd - oct increased the repeatability and decreased variability in namd patients , and demonstrated a significant advantage of sd - oct over td - oct . krebs et al . mentioned the difference of crt values detected with the td - oct and the sd - oct devices and attributed this variability to the different posterior reference lines of the devices . they advised avoiding using different devices during an ongoing study and suggested a formula for comparing the values defined by the two devices . in a case , sd - oct was found to be superior to td - oct in regard to fluid and cyst detection . querques et al . compared the ability of the 2 sd - oct and td - oct devices in detecting the disease activity in the namd patients . cirrus sd - oct ( cirrus hd - oct , carl zeiss - meditec , inc . , dublin , ca ) and spectralis sd - oct were found to be superior to td - oct especially in detecting srf and ped . they also reported that the correcting factor should be 1.48 to extrapolate the crt measurements from stratus td - oct to spectralis sd - oct , which was comparable with our value of 1.51 . cukras et al . reported that cirrus sd - oct was able to detect the presence of the exudative activity ( subretinal or intraretinal fluid ) in 48% of the namd patients who were defined as inactive with stratus td - oct . compared 4 different sd - oct devices with stratus td - oct in regard to disease activity in the namd patients after intravitreal ranibizumab treatment . they reported that all 4 sd - oct devices were superior to td - oct in detecting subretinal fluid in three - dimensional cube mode . however , in linear b - scan mode , only the spectralis sd - oct was reported to be superior to the stratus td - oct in detecting subretinal fluid , and the oct-1000 was reported to be superior in detecting sub - rpe fluid . in addition , the presence of subretinal fluid , intraretinal cysts , and subrpe fluid on the spectralis sd - oct was reported to be 16% , 11% , and 13% , respectively , when td - oct did not show any sign of disease activity . only the rate of the sub - rpe fluid detection of our study was lower than that of sayanagi et al . the va loss during the as - needed treatment regimens for the namd which is usually attributed to the treatment delays , the low injection numbers , the presence of ped at the baseline , and the crt fluctuations during the treatment is usually irreversible [ 2529 ] . except one , three of these factors , treatment delays , crt fluctuations , and low injection numbers are closely related with our ability to detect disease activity . therefore , in the era of the sd - oct devices , the td - oct seems inaccurate and insufficient in deciding whether or not retreatment is necessary at the monthly visits of the namd patients . on the other hand , while the crt is an important prognostic factor for the diabetic macular edema and retinal vein occlusion patients , and td - oct is comparable with the sd - oct devices in this group of patients , td - oct may still have a role in our retreatment decisions .   limitations of this study include the relatively small number of patients and the one - sided assessment between the two devices ( we did not evaluate the nonactive patients via the sd - oct with td - oct ) . strengths of this study were the prospective design and the homogeneity of the patients . in conclusion , the previous studies and the present study suggest that sd - oct is essential in the followup of the namd patients who are under an as - needed treatment regimen . using td - oct may result in worse visual outcomes due to the treatment delays and inadequate treatment .
purpose . to evaluate the ability of spectral - domain optical coherence tomography to detect subtle amounts of retinal fluid when the choroidal neovascularization is detected as inactive via time - domain optical coherence tomography and clinical examination in neovascular age - related macular degeneration ( namd ) patients 
 . methods . 
 forty - nine eyes of 49 patients with namd after ranibizumab treatment were included in this cross - sectional , prospective study . 
 all patients were imaged with td - oct and sd - oct at the same visit one month after a ranibizumab injection . 
 the presence of subretinal , intraretinal , and subretinal pigment epithelium fluid ( subrpe ) in sd - oct was evaluated ; also mean central retinal thickness ( crt ) and the rate of vitreoretinal surface disorders detected via the two devices were evaluated . 
 results . 
 the mean crt via td - oct and sd - oct was 218.1  51.3 and 325.7  78.8 microns . 
 sixteen patients ( 32.6% ) showed any kind of retinal fluid via sd - oct . in detail , 8 patients ( 16.3% ) showed subretinal fluid , 10 patients ( 20.4% ) showed intraretinal fluid , and 3 patients ( 6.1% ) showed subrpe fluid . 
 the ability of detecting vitreoretinal surface disorders was comparable between the two devices , except vitreomacular traction . 
 conclusion . 
 sd - oct is essential for the namd patients who are on an as - needed treatment regimen with ranibizumab . 
 only td - oct and clinical examination may cause insufficient treatment in this group of patients .