Purpose-To map ganglion cell complex thickness with high-speed Fourier-domain optical coherence tomography (FD-OCT) and compute novel macular parameters for glaucoma diagnosis.Design-Observational, cross-sectional study.Participants-One hundred seventy-eight participants in the Advanced Imaging for Glaucoma Study, divided into three groups: 65 persons in the normal group (N), 78 in the perimetric glaucoma group (PG), and 52 in the pre-perimetric glaucoma group (PPG). Methods-TheRTVue FD-OCT system was used to map the macula over a 7×6 mm region. The macular OCT images were exported for automatic segmentation using software we developed. The program measured macular retinal (MR) thickness and ganglion cell complex (GCC) thickness. The GCC was defined as the combination of nerve fiber, ganglion cell, and inner plexiform layers. Pattern analysis was applied to the GCC map and the diagnostic power of pattern-based diagnostic parameters were investigated. Results were compared to time-domain (TD) Stratus OCT measurements of MR and circumpapillary nerve fiber layer (NFL) thickness.Main Outcome Measures-Repeatability was assessed by intraclass correlation (ICC), pooled standard deviation, and coefficient of variation. Diagnostic power was assessed by the area under the receiver operator characteristic (AROC) curve. Measurements in the PG group were the primary measures of performance.Results-The FD-OCT measurements of MR and GCC averages had significantly better repeatability than TD-OCT measurements of MR and NFL averages. The FD-OCT GCC average had significantly (P=0.02) higher diagnostic power (AROC = 0.90) than MR (AROC = 0.85 for both FD-OCT & TD-OCT) in differentiating between PG and N. One GCC pattern parameter, global loss volume, had significantly higher AROC (0.92) than the overall average (P=0.01). The diagnostic powers of the best GCC parameters were statistically equal to TD-OCT NFL average. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.This article contains online-only material. The following should appear online-only: table 3, figures 3 and figure 6. NIH Public Access Author ManuscriptOphthalmology. Author manuscript; available in PMC 2010 December 1. Published in final edited form as:Ophthalmology. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptConclusions-The higher speed and resolution of FD-OCT improved the repeatability of macular imaging compared to standard TD-OCT. Ganglion cell mapping and pattern analysis improved diagnostic power. The improved diagnostic power of macular GCC imaging is on par with, and complementary to...
Objective To detect abnormal corneal thinning in keratoconus using pachymetry maps measured by high-speed anterior segment optical coherence tomography (OCT). Design Cross-sectional observational study. Participants Thirty-seven keratoconic eyes from 21 subjects and 36 eyes from 18 normal subjects. Methods The OCT system operated at a 1.3 μm wavelength with a scan rate of 2000 axial scans per second. A pachymetry scan pattern (8 radials, 128 axial scans each; 10 mm diameter) centered at the corneal vertex was used to map the corneal thickness. The pachymetry map was divided into zones by octants and annular rings. Five pachymetric parameters were calculated from the region inside the 5 mm diameter: minimum, minimum–median, inferior–superior (I-S), inferotemporal–superonasal (IT-SN), and the vertical location of the thinnest cornea. The 1-percentile value of the normal group was used to define the diagnostic cutoff. Placido-ring–based corneal topography was obtained for comparison. Main Outcome Measures The OCT pachymetric parameters and a quantitative topographic keratoconus index (keratometry, I-S, astigmatism, and skew percentage [KISA%]) were used for keratoconus diagnosis. Diagnostic performance was assessed by the area under the receiver operating characteristic (AROC) curve. Results Keratoconic corneas were thinner. The pachymetric minimum averaged 452.6±60.9 μm in keratoconic eyes versus 546±23.7 μm in normal eyes. The 1-percentile cutoff was 491.6 μm. The thinnest location was inferiorly displaced in keratoconus (−805±749 μm vs −118±260 μm ; cutoff, −716 μm). The thinning was focal (minimum–median: −95.2±41.1 μm vs −45±7.7 μm ; cutoff, −62.6 μm). Keratoconic maps were more asymmetric (I-S, −44.8±28.7 μm vs −9.9±9.3 μm ; cutoff, −31.3 μm ; and IT-SN, −63±35.7 μm vs −22±11.4 μm ; cutoff, −48.2 μm). Keratoconic eyes had a higher KISA% index (2641±5024 vs 21±19). All differences were statistically significant (t test, P<0.0001). Applying the diagnostic criteria of any 1 OCT pachymetric parameter below the keratoconus cutoff yielded an AROC of 0.99, which was marginally better (P= .09) than the KISA% topographic index (AROC, 0.91). Conclusions Optical coherence tomography pachymetry maps accurately detected the characteristic abnormal corneal thinning in keratoconic eyes. This method was at least as sensitive and specific as the topographic KISA. Financial Disclosure(s) Proprietary or commercial disclosure may be found after the references.
Aim-To measure total retinal blood flow in normal human eyes using Doppler Fourier-domain optical coherence tomography (FD-OCT).Methods-10 normal people aged 35 to 69 years were measured for the right eye using Doppler FD-OCT. Double circular scans around the optic nerve heads were used. Four pairs of circular scans that transected all retinal branch vessels were completed in 2 s. Total retinal blood flow was obtained by summing the flows in the branch veins. Measurements from the eight scans were averaged. Veins with diameters >33 μm were taken into account.Results-Total retinal blood flow could be measured in eight of 10 subjects: mean (SD) = 45.6 (3.8) μl/min (range 40.8 to 52.9 μl/min). The coefficient of variation for repeated measurements was 10.5%. Measured vein diameters ranged from 33.3 to 155.4 μm. The averaged flow speed was 19.3 (2.9) mm/s, which did not correlate with vessel diameter. There was no significant difference between flows in the superior and inferior retinal hemispheres.Conclusions-Double circular scanning using Doppler FD-OCT is a rapid and reproducible method to measure total retinal blood flow. These flow values are within the range previously established by laser Doppler flowmetry.Many of the leading causes of blindness are related to abnormalities in retinal blood flow, such as diabetic retinopathy and age-related macular degeneration. 1 2 Central and branch retinal vein occlusions are also common retinal diseases that are characterised by decreased retinal blood flow. In glaucoma, poor circulation in the retina and optic nerve is thought to be a risk factor for disease progression. 3 4 A practical and accurate method for retinal blood-flow measurement may be useful in the diagnosis and management of these diseases.Optical coherence tomography (OCT) 5 provides high-resolution cross-sectional imaging and is commonly used in the diagnosis and management of retinal diseases. 6 7 In addition to obtaining morphological images, OCT can also detect the Doppler shift of reflected light, which provides information on blood flow. 8 9 For Doppler Fourier-domain optical coherence tomography (FD-OCT), 10 11 light reflected by moving blood induces a Doppler frequency shift that is proportional to the velocity component parallel to the axis of the probe beam. This MATERIALS AND METHODS Study populationThe research protocol was approved by the institutional review board of the University of Southern California (USC), in accordance with the tenets of the Declaration of Helsinki. Ten healthy human subjects (four male, six female) between the ages of 35 and 69 years (average 57.4 years) participated in the study at the USC Doheny Eye Institute. Written informed consent was obtained from each subject. The right eyes were measured. The following inclusion criteria were met for these normal subjects: (a) no history or evidence of retinal pathology or glaucoma; (b) no history of keratorefractive surgery; (c) normal Humphrey SITA 24-2 visual field: a mean deviation (MD) and pattern standard deviat...
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