![]() ![]() Participants were defined based on the following criteria: (1) age 15 years or older, (2) negative family history of glaucoma, (3) intraocular pressure ≤21 mmHg, (4) no evidence of glaucomatous damage at the optic nerve head (notching of neural rim, RNFL defect, cup disc ratio asymmetry ≥0.3, generalized thinning of the neural rim), and (5) two normal and reliable Humphrey 24-2 SITA tests. Each participant received a detailed ophthalmologic examination including measurement of best-corrected visual acuity, slit-lamp biomicroscopy, Goldmann applanation tonometry, dilated biomicroscopic and indirect fundus examinations, Humphrey 24-2 standard automated perimetry using the Swedish Interactive Test Algorithm (SITA) strategy (Carl Zeiss Meditec, Dublin, CA, USA), and color and red-free fundus photography with a digital system (Canon UVi-60, EyeQ System Tokyo, Japan). In all, 20 eyes of 20 white participants were studied. All participants gave written informed consent before entering into the study. The study protocol adhered to the tenets of the Declaration of Helsinki and was approved by the local Institutional Review Board. This prospective, cross-sectional study was performed at the Diagnostic Division of the Hospital de Olhos de Araraquara, Brazil. We also compared these measurements to those obtained at correspondent locations in our previous histologic study. To better understand and interpret the RNFL measurements provided by the OCT, we obtained measurements of the RNFL thickness at eight fixed distances from the optic disc margin instead of the optic disc centre, in four radial sections of normal subjects. 21 However, as the peripapillary RNFL thickness is inversely related to the distance from optic disc margin, 22 measurements obtained using a circle of fixed diameter do not account for a possible influence of the optic disc size on the RNFL thickness. 17, 18, 19, 20 Recently, a normative database for RNFL thickness has been incorporated to the software of the third-generation OCT system using the 3.4-mm-diameter circle. Good intra- and intersession reproducibility of the RNFL measurements obtained with OCT have already been established, especially using a circle of 3.4-mm fixed diameter. 10, 11, 12, 13 Some previous reports that have suggested that structural damages precede functional deficits in glaucomatous eyes 14, 15, 16 emphasizes the importance of developing an accurate RNFL and optic disc analyser. 5, 6, 7, 8, 9 Additionally, this new tool has demonstrated increasing potential for analysing and, particularly, detecting early pathological alterations of the RNFL that occur in glaucomatous eyes. Since the last decade, the OCT has demonstrated its usefulness in assisting the diagnosis and management of a multitude of ophthalmologic diseases, such as choroidal neovascularization, diabetic macular oedema, central serous chorioretinopathy, among others. 1, 2 Briefly, cross-sectional images of the retina obtained by a scanning interferometer allow accurate measurement of ocular tissue thickness, such as that of retinal nerve fibre layer (RNFL) and neural retina, based on different reflectivities of retinal layers. Its elementary fundamentals of image acquisition and interpretation in ophthalmology have been previously described. Optical coherence tomography (OCT) is a relatively new noncontact imaging technique that has been developed to assess tissue thickness with micrometer scale sensitivity. RNFL measurements assessed by OCT 3 were significantly thinner close to the optic disc margin. Conclusionsįour normal OCT RNFL profiles were established and compared with histological data obtained from the same area. The measurements automatically generated by the OCT built-in software were thinner ( P<0.001) than histologic ones close to the disc margin. The RNFL thickness decreased ( P<0.001) as the distance from the disc margin increased for all sections. ![]() Quadrant location and distance from disc margin interaction in RNFL thickness was statistically significant ( P<0.001). Additionally, two radial scans orientated at 45 and 135° crossing the optic disc centre were performed in six of 20 eyes, and RNFL thickness was measured at disc margin. Four different radial sections (superotemporal, superonasal, inferonasal, and inferotemporal) were studied to establish RNFL thickness OCT profiles. A circular scan was adjusted to the size of the optic disc and three scans were performed with this radius and every 200 μm thereafter, up to a distance of 1400 μm. MethodsĪ total of 20 normal eyes were studied. To establish four normal retinal nerve fibre layer (RNFL) thickness radial profiles based on third-generation optical coherence tomography (OCT) and to compare them with previously reported histologic measurements. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |