![]() The repeatability of the method has been assessed previously. Aggregate loss was defined as the sum of deviations from the background sensitivity of values measured at test points within the area of the EZ break. Aggregate sensitivity loss was calculated as described earlier, 3 briefly: the mean of retinal sensitivity values within the grid at test points outside the area of the EZ break was calculated and considered the background sensitivity. ‘En face’ SD-OCT images and retinal sensitivity data were superimposed over infrared images of the fundus and adjusted to attain exact correspondence based mainly on vascular landmarks. Since technical factors (including directionality of the incident light) may affect the intensity of the signal, an attenuated but discernible EZ signal was interpreted in this context as still present, an EZ break was defined as an area where the EZ stratification was no longer discernible. OCT volume data was used in its original form with no enhancements or normalisation of individual B-scans with lower signal to noise ratio, instead information from these was evaluated in conjunction with information from adjacent higher quality B-scans. Lesion delineation was performed through an initial thresholding followed by a manual correction of lesion edges as necessary, based on a close inspection of corresponding OCT volume data in B-scans and reconstituted scans perpendicular to B-scans (along the Y axis), in FEI Amira. ![]() EZ break boundary delineation and area measurements were performed in Adobe Photoshop. 11 Briefly, a slab from the mid-line of the EZ, one pixel in thickness was selected, orthogonal topographic maps (‘en face’ images) of this slab was created in Amira and exported into Adobe Photoshop CS6 (Adobe Systems Incorporated, San Jose, CA, USA). OCT volume scans from both machines were imported into a dedicated 3D image analysis software (Visage Imaging Amira version 5.3, FEI Visualization Sciences Group, Hillsboro, Oregon, USA) and segmentation of the EZ layer was performed manually, as described earlier. In the current analyses our aim was to investigate further the characteristics and interrelationship of these structural and functional disease markers both by calculating aggregate loss as described previously and by a new, simple and fast assessment method, from data collected using Carl Zeiss Meditec HD-OCT4000 or Heidelberg Spectralis OCT devices and CenterVue Maia microperimeters in a phase one clinical trial of ciliary neurotrophic factor (CNTF) in MacTel. 3, 4 These calculations are relatively labor-intensive and require an accurate alignment of OCT ‘en face’ and microperimetric data. In our previous studies, retinal sensitivity changes were assessed by calculating aggregate sensitivity loss. ![]() ![]() The CenterVue Maia microperimeter has a wider dynamic range (32dB) and uses an infrared scanning laser ophthalmoscope for capturing the reference fundus image. Misalignments between test data and reference image are not infrequent. The Nidek MP1 has a limited dynamic range (20dB) and uses flash photography for acquiring a reference color fundus image. 3, 4 The axial and lateral resolutions of the Topcon 3DOCT-1000 are limited and only a single raster scan pattern of 128 B-scans in an area of 20°×20° is available. In our previous studies we analyzed OCT volume scans acquired using Topcon 3DOCT-1000 devices and retinal sensitivity measurements using Nidek MP1 microperimeters. 3– 9īoth EZ break area and focal retinal sensitivity loss, as reflected by mesopic microperimetry have been proposed as potential outcome measures in MacTel. One characteristic neurodegenerative sign apparent in optical coherence tomographic (OCT) images is a disruption (or ‘break’) in the line attributed to the junctions between photoreceptor inner and outer segments, IS/OS junction line more recently, this signal was attributed to the inner segment ellipsoids, ‘ellipsoid zone’ (EZ), This sign was found to be associated with a loss of retinal sensitivity. Although many therapies have been tested in MacTel, none have been shown to be effective to-date. 1 Its clinical phenotype is characterized by both vascular and neurodegenerative changes. Macular Telangiectasia Type 2 (MacTel) is a bilateral, slowly progressive, potentially blinding retinal disease in the juxtafoveal region of unknown cause.
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