Characterization of Retinal Nerve Fiber Layer in Nonglaucomatous Eyes With Tilted Discs
Archives of ophthalmology (Impact Factor: 4.4). 01/2010; 128(1):141-2. DOI: 10.1001/archophthalmol.2009.340
Article: Tilted Optic Disks[Show abstract] [Hide abstract]
ABSTRACT: Tilted optic disks are a common finding in the general population. An expression of anomalous human development, the tilted disk appears rotated and tilted along its axes. Visual sequelae described with tilted optic disks include myopia, astigmatism, visual field loss, deficient color vision, and retinal abnormalities. Although the natural course of tilted optic disks is nonprogressive, the anomaly can be mistaken for tumors of the anterior visual pathway, edema of the optic nerve head, or glaucoma. A thorough examination of patients with tilted disk includes refraction, dilated fundus examination, and visual field testing. At times, neuroimaging may be necessary to arrive at the correct diagnosis. Until normative data are validated for tilted disks, the role of new imaging technologies for the optic nerve head is limited. Familiarity with the spectrum of ophthalmoscopic appearance and the clinical manifestations of tilted disks may be the most critical factors in avoiding misdiagnosis.
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ABSTRACT: PURPOSE. Retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) can be unreliable in the presence of a myopic tilted disc. The purpose of this study was to investigate the influence of the calculation circle location of spectral domain (SD)-OCT when measuring RNFL thickness in healthy subjects with myopic tilted disc. METHODS. Sixty-nine eyes with myopic tilted disc and no other ocular abnormalities were analyzed. In all eyes, RNFL thickness was measured twice: first, along a calculation circle determined by a built-in algorithm (referred to as circle 1) and then along a manually positioned calculation circle based on the contours of the neural canal opening (NCO) (referred to as circle 2). The mean number of clock hours below normal at the 5% level and the proportion of eyes with abnormally thin clock hours at the 5% level were compared between the two methods: RESULTS. The mean number of clock hours below normal at the 5% level was significantly lower in circle 2 (0.84 ± 1.31) than in circle 1 (1.42 ± 1.43; P < 0.05). The proportion of eyes with abnormally thin clock hours at the 5% level was significantly lower (P < 0.001) in circle 2 (42%) than in circle 1 (69.9%). CONCLUSIONS. In subjects with myopic tilted disc, RNFL thickness measurements along the calculation circle based on the contours of the NCO seem to be more comparable to the normative database of the SD-OCT than does the automatically determined scan position.
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ABSTRACT: The purpose of the study was to investigate the effects of myopic optic disc tilt and rotation on peripapillary retinal nerve fiber layer (RNFL) thickness characteristics measured by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT). A total of 93 right eyes from 93 healthy young male individuals with myopia underwent ophthalmic examinations, including refractive error, axial length, and optic disc area measurements. The superior/inferior peak locations, RNFL thickness, and horizontal/vertical optic disc tilt were evaluated using the Cirrus HD OCT. The optic disc rotation was assessed by the angle between the long axis of the optic disc and the vertical meridian. The patients were divided into the tilted group and the non-tilted group; the tilted group was further divided into the rotated group and the nonrotated group. The eyes in the tilted group (n=47) had a greater axial length and thicker temporal RNFL and more temporally positioned superior/inferior peak locations than the non-tilted group (n=46) (all P <0.05). Among the eyes in the tilted group, the eyes in the rotated group (n=23) had a thicker temporal RNFL and a more temporally positioned superior peak location than the eyes in the nonrotated group (n=24) (all P <0.05). The eyes with a myopic temporal optic disc tilt and counterclockwise rotation had a thicker temporal RNFL and more temporally positioned superior peak location. The characteristics of the RNFL thickness in eyes with myopic optic disc tilt and rotation should be considered when interpreting the RNFL thickness measured by the Cirrus HD OCT.
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