Between-subject variability in asymmetry analysis of macular thickness
| Autor: | Victor E. Malinovsky, William H. Swanson, Muhammed S. Alluwimi |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Adult
Male medicine.medical_specialty Materials science genetic structures Nerve fiber layer Glaucoma Foveola Retina Article chemistry.chemical_compound Young Adult Optical coherence tomography Ophthalmology medicine Humans Ganglion cell layer Aged Aged 80 and over medicine.diagnostic_test Retinal Anatomy Organ Size Middle Aged medicine.disease eye diseases medicine.anatomical_structure chemistry Female sense organs Tomography Optical Coherence Optometry Optic disc |
| Zdroj: | Optometry and vision science : official publication of the American Academy of Optometry. 91(5) |
| ISSN: | 1538-9235 |
| Popis: | Structural changes in patients with glaucoma have a crucial role in clinical diagnosis and management. Optical Coherence Tomography (OCT) has been widely used to image structural features of glaucoma with a variety of imaging options. Retinal Nerve Fiber Layer (RNFL) thickness has been extensively investigated using OCT, but RNFL measurements have limitations that introduce substantial challenges in clinical decision-making. In this study we investigated a method intended to overcome some of these limitations using macular thickness measurements. RNFL thickness has high between-individual variability1–3 and can be affected by magnification factors such as axial length4–6 and corneal curvature.7 Optic disc and rim area measurements also exhibit high between-subject variability among control subjects.8–10 Moreover, blood vessels can contribute to measured average RNFL thickness,11 as can glial cells,12 with substantial variability among individuals. In histological studies of human eyes, between-subject variability in the total number of ganglion cells and their axons showed a two-fold range.13–15 The lowest between-subject variability in ganglion cell density was observed within 0.5 to 1 mm eccentricity from the foveal center13, 14 which may be related to active control processes during embryological development. The number of ganglion cells is substantially reduced during development, and is a source of variability among individuals.16, 17 Recently, OCT has been used to measure retinal thickness of the macula in patients with glaucoma.18–22 Although OCT can provide precise retinal thickness measurements, there are limitations such as the low reflectivity of the ganglion cell layer. Moreover, differences in magnification factors such as axial length and refractive error among individuals can influence the accuracy of retinal thickness measurements.18, 23–25 These factors can contribute to between-subject variability. It has been estimated that around 50% of ganglion cells are found within ±8.0° eccentricity from the foveola,13 therefore, between-subject variation in ganglion cell density in this region may be an important factor in analysis of macular thickness. Posterior Pole Asymmetry Analysis has been recently introduced with Spectralis OCT (Heidelberg Engineering, V 5.4, Heidelberg, Germany), to compare macular thickness within and between eyes of an individual.26 The within-eye Asymmetry Analysis calculates the difference in retinal thickness between superior and inferior cells in 64-cell square grid superimposed on a 24°×24° retinal region centered on the foveola. In this new protocol, a gray scale has been used to indicate asymmetries in retinal thickness within and between eyes. On this scale, white is used to represent no asymmetry in retinal thickness, light gray to dark gray represent asymmetries from approximately 5 to 25 microns, and black represents greater asymmetries of more than 25 microns. However, black cells in the Asymmetry Analysis may not be uncommon in subjects free of eye disease.27 Therefore more investigation is warranted to better understand the gray scale for the Asymmetry Analysis grid. In this study, we assessed Asymmetry Analysis as a method for reducing between-subject variability. |
| Databáze: | OpenAIRE |
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