Yong Un Shin

Choroidal Thickness and Volume Mapping by a Six Radial Scan Protocol on Spectral-Domain Optical Coherence Tomography

PURPOSE To report a 6 radial scan protocol, which simply generates a topographic map of choroidal thickness and volume on a commercial spectral-domain optical coherence tomography (SD-OCT) device. We analyzed the features of the resulting choroidal maps in healthy eyes. DESIGN Prospective, noncomparative case series. PARTICIPANTS Eighty eyes from 40 healthy volunteers who visited the healthcare clinic of Hanyang University Hospital from December 2010 to February 2011. METHODS All participants underwent a 6 radial scanning protocol using an SD-OCT device. In a single session, the device produces 6 high-resolution averaging B-scan images. For segmentation of the choroid layer, the reference lines of the retinal boundary (internal limiting membrane-retinal pigment epithelium) were adjusted to the choroidal boundary (retinal pigment epithelium-choroid/sclera junction) in each of the 6 radial B-scans. A topographic map of choroidal thickness and volume was automatically generated by built-in software according to the Early Treatment Diabetic Retinopathy Study (ETDRS) layout. A statistical analysis was conducted to compare the choroidal thickness and volume measurements for each ETDRS subfield. MAIN OUTCOME MEASURES An ETDRS-style topographic map of choroidal thickness and volume. RESULTS The mean time required for segmentation adjustment was 167.4±15.8 seconds. The mean choroidal thickness of all ETDRS subfields was 285.9±53.0 μm, and the mean total choroidal volume of the entire ETDRS area was 7.72±1.2 mm(3). The nasal outer macula area was significantly smaller than any other ETDRS subfield (P<0.05) except for the adjacent superior and inferior outer macula subfields. Refractive error was correlated with choroidal thickness in all ETDRS subfields. Age was also correlated with choroidal thickness for almost all of the ETDRS subfields except for the temporal inner, nasal outer, and temporal outer macula areas. The total choroidal volume was correlated with the refractive error and age. CONCLUSIONS A 6 radial scan protocol, using a commercial SD-OCT device, enables the production of reliable choroidal thickness and volume maps with an ETDRS layout. By using this protocol, more comprehensive choroidal evaluation is possible in clinical practice or research.

Time-Periodic Characteristics in the Morphology of Idiopathic Central Serous Chorioretinopathy Evaluated by Volume Scan Using Spectral-Domain Optical Coherence Tomography

PURPOSE To investigate the time-period characteristics associated with morphologic changes in idiopathic central serous chorioretinopathy (CSC) using volume scans acquired by spectral-domain optical coherence tomography (SD-OCT). DESIGN Retrospective, observational, cross-sectional case series. METHODS Patients underwent visual acuity measurements, fundus examinations, fluorescein angiography, indocyanine green angiography, and SD-OCT volume scans. Patients were classified into 5 categories-acute CSC, early chronic (EC) CSC, late chronic (LC) CSC, sequelae of CSC, or recurrent CSC-according to the chronicity and the recurrence. We investigated the relationship between our classification and the detailed morphologic changes of the retinal pigment epithelium and outer retina that were observed in the SD-OCT images. RESULTS A total of 76 eyes from 75 patients were included in this study. Serous retinal detachment was relatively higher in acute CSC. Low to flat pigment epithelial detachments (PEDs) were most commonly observed in all stages of CSC, especially in LC CSC, but some semicircular PEDs were occasionally observed in eyes with acute or EC CSC. Retinal dragging with fibrin was most frequently observed in eyes that were in the early stage of acute CSC. A thickened posterior surface of the detached retina was most commonly observed in eyes with acute CSC, whereas a thinned posterior surface of the detached retina was observed in eyes with LC CSC. Hyperreflective dots and subretinal exudates were more commonly observed in eyes with EC and LC CSC than in eyes with acute CSC. In eyes with recurrent CSC, 2 different patterns of SD-OCT findings were observed; these patterns resembled those that were found in either acute CSC or LC CSC. CONCLUSIONS SD-OCT finding patterns in CSC eyes differ according to the chronicity and the recurrence of the disease. Detailed investigation of the retinal pigment epithelium and outer retina using SD-OCT could be useful for estimating the duration of CSC.

Measurement of Choroidal Thickness in Normal Eyes Using 3D OCT-1000 Spectral Domain Optical Coherence Tomography

Purpose To study choroidal thickness and its topographic profile in normal eyes using 3D OCT-1000 spectral domain optical coherence tomography and the correlation with age and refractive error. Methods Fifty-seven eyes (45 individuals) with no visual complaints or ocular disease underwent horizontal and vertical line scanning using 3D OCT-1000. The definition of choroidal thickness was the vertical distance between the posterior edge of the hyper-reflective retinal pigment epithelium and the choroid/sclera junction. Choroidal thickness was measured in the subfoveal area at 500 µm intervals from the fovea to 2,500 µm in the nasal, temporal, superior, and inferior regions. The spherical equivalent refractive error was measured by autorefractometry. Statistical analysis was used to confirm the correlations of choroidal thickness with age and refraction error. Results The mean age of the 45 participants (57 eyes) was 45.28 years. Detailed visualization of the choroid for measuring its thickness was possible in 63.3% of eyes. The mean subfoveal choroidal thickness was found to be 270.8 µm (standard deviation [SD], ±51 µm), in horizontal scanning and 275.0 µm (SD, ±49 µm) in vertical scanning. The temporal choroidal thickness was greater than any 500 µm interval in corresponding locations, and there was no significant difference between the superior and inferior choroid as far as 2,000 µm from the fovea. Age and refractive error were associated with subfoveal choroidal thickness in terms of regression (p < 0.05). Conclusions Choroidal thickness in normal Korean eyes can be measured using 3D OCT-1000 with high resolution line scanning. The topographical profile of choroidal thickness varies depending on its location. Age and refractive error are essential factors for interpretation of choroidal thickness.

Retro-mode Imaging for Retinal Pigment Epithelium Alterations in Central Serous Chorioretinopathy

PURPOSE To propose a simple, noninvasive retro-mode imaging technique employing confocal scanning laser ophthalmoscopy (cSLO) as a novel imaging modality for the detection of alterations in retinal pigment epithelium (RPE) in central serous chorioretinopathy (CSCR). DESIGN Retrospective observational case series. METHODS A total of 48 eyes from 45 patients at various phases of CSCR were included. All patients underwent spectral-domain optical coherence tomography (SD-OCT) using a volume scan protocol, fluorescein angiography (FA), indocyanine green angiography (IA), and retro-mode imaging by cSLO. We investigated retro-mode images to evaluate RPE status by comparing the results with those of SD-OCT, FA, and IA. RESULTS Patients had various phases of CSCR: acute (23 eyes), chronic (17 eyes), and resolved (8 eyes). Retro-mode imaging detected subtle alterations in subretinal fluid (SRF) and RPE, which were undetectable with FA or IA. The correspondence between SD-OCT scanning the entire macula and retro-mode imaging differed according to the chronicity of the disease. In cases with acute CSCR, the correspondence with SD-OCT reached 44.44% in eyes with semicircular pigment epithelial detachment (PED), 33.33% in eyes with low to flat PED, and 35.71% in eyes with RPE protrusion. In cases with chronic CSCR, the correspondence with SD-OCT reached 83.33%, 57.14%, and 85.71% in eyes with semicircular PED, low to flat PED, and RPE protrusion, respectively. Correspondence in cases with resolved CSCR was 100% in eyes with either semicircular or low to flat PED and 83.33% in eyes with RPE protrusion. CONCLUSIONS Simple and noninvasive retro-mode imaging by cSLO provides improved comprehensive topographic information of RPE alterations in CSCR. Our detailed interpretation may be useful for future research of retro-mode imaging in various macular disorders.

A Novel Noninvasive Detection Method for Retinal Nonperfusion Using Confocal Red-free Imaging

PURPOSE To report confocal red-free blue reflectance imaging as a novel, noninvasive imaging modality for the detection of retinal nonperfusion and to compare its effectiveness with that of fluorescein angiography (FA) in diabetic retinopathy (DR) and retinal vein occlusion (RVO). DESIGN Evaluation of diagnostic technology, retrospective observational case series. PARTICIPANTS We enrolled 54 eyes of 44 patients with DR or RVO that had definite retinal nonperfusion on FA. METHODS All patients underwent red-free blue reflectance imaging and FA using a confocal scanning laser ophthalmoscope. For all patients, macular and midperipheral retinal nonperfusion were identified on both confocal red-free and corresponding FA images, and were delineated by 2 independent readers. We evaluated the correspondence of the 2 imaging methods by comparing the sizes of the delineated areas and obtaining the overlapping ratio after image processing. MAIN OUTCOME MEASURES Comparison of size and overlapping correspondence between delineated area of retinal nonperfusion obtained by FA and confocal red-free imaging. RESULTS Image analysis showed a high correlation (r>0.9) in the mean size of retinal nonperfusion between confocal red-free and corresponding FA images with DR or RVO. Reliable agreement between the 2 methods was confirmed by size comparisons (P = 0.563) and overlapping correspondence (overlapping ratio, 0.76) of the delineated area. CONCLUSIONS Our findings suggest that confocal red-free imaging is a simple, reliable, safe, and noninvasive method for effectively plotting retinal nonperfusion. This procedure, first reported herein, has the potential to be used for the noninvasive detection and quantification of retinal nonperfusion in screening, initial evaluation, treatment, and follow-up of progressive ischemic retinopathy such as DR and RVO.

Outer photoreceptor layer thickness mapping in normal eyes and eyes with various macular diseases using spectral domain optical coherence tomography: A pilot study

BackgroundTo obtain a de novo map of outer photoreceptor layer (OPRL) thickness using a semiautomatic segmentation method for commercial spectral-domain optical coherence tomography (SD-OCT) and analyze the features of the resulting OPRL map in normal eyes and eyes with various inactive macular diseases.MethodsForty normal eyes and 50 eyes with various inactive macular diseases such as resolved central serous chorioretinopathy (20 eyes), surgically-repaired macular hole (10 eyes), epiretinal membrane (10 eyes), and reattached rhegmatogenous retinal detachment (10 eyes) were screened. All subjects underwent a 12 radial scan protocol in SD-OCT. The segmentation lines defining the OPRL were modified using built-in software. The diseased eyes were subdivided into two groups (good vision, or intermediate to poor vision) based on a visual acuity better or worse than 20/40. The map of the OPRL thickness was obtained automatically by the embedded software and was presented as the Early Treatment Diabetic Retinopathy Study (ETDRS) style.ResultsThe mean OPRL thickness in normal eyes in all subfields was 40.37 ± 4.35 μm. The central subfield area showed the greatest mean OPRL thickness in normal eyes. The mean OPRL thickness of diseased eyes with good vision in the central subfield was greater than that of eyes with intermediate to poor vision. The OPRL thickness map showed various patterns according to the type of macular diseases.ConclusionsWe suggest that our semiautomated segmentation method using a 12 radial scan protocol is simple, fast, and suitable for producing a reliable OPRL map with ETDRS. This quantitative data could be useful in clinical practice or research of various macular diseases.

Retromode imaging: Review and perspectives

Retromode imaging with infrared lasers is a novel imaging method which has been made possible by the newly introduced confocal scanning laser ophthalmoscope. Retromode imaging uses a laterally deviated confocal aperture with a central stop, which creates a shadow and allows deep retinal and retinal pigment epithelium changes to be visualized as pseudo-3-dimensional images. Its clinical value coupled with its simple, rapid, and noninvasive nature is increasingly appreciated. The combination of retromode imaging with conventional imaging methods such as fundus photography, fluorescein angiography, and optical coherence tomography can help to precisely and comprehensively evaluate pathophysiologic features of retinal disorders. This review summarizes basic principles of imaging and retromode findings in various retinal disorders and is expected to guide future investigations of retromode imaging.