Young Hoon Hwang

Myopic optic disc tilt and the characteristics of peripapillary retinal nerve fiber layer thickness measured by spectral-domain optical coherence tomography.

PurposeTo investigate the correlation between myopic optic disc tilt and the characteristics of peripapillary retinal nerve fiber layer (RNFL) thickness measured by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, CA). MethodsA total of 255 eyes of 255 healthy young male participants with various degrees of refractive errors (mean spherical equivalent, −3.17±2.40 D; range, −11.00 to 0.00 D) underwent ophthalmic examinations, including refractive error, axial length, and optic disc area measurement. The degree of horizontal/vertical optic disc tilt was evaluated by cross-sectional images obtained by the Cirrus HD OCT. The average, superior, nasal, inferior, and temporal quadrant thickness and superior/inferior peak locations of the peripapillary RNFL were also measured with the Cirrus HD OCT. ResultsOn the univariate analysis, eyes with more temporally tilted optic discs (horizontal tilt) had higher myopia, greater axial length, a thinner average, superior, nasal, and inferior RNFL, thicker temporal RNFL, and more temporally positioned superior/inferior peak locations (all P values <0.001). The degree of inferior optic disc tilt (vertical tilt) was associated with high myopia and a more temporally positioned inferior peak location (all P values <0.05). On multivariate analysis, eyes with more temporally tilted optic discs had a thicker temporal RNFL and more temporally positioned superior/inferior peak locations. ConclusionsThe characteristics of the peripapillary RNFL thickness were associated with the degree of myopic optic disc tilt, especially in the temporal area. The degree of myopic optic disc tilt should be considered when interpreting the RNFL thickness measured by the Cirrus HD OCT.

Characteristics of peripapillary retinal nerve fiber layer thickness in eyes with myopic optic disc tilt and rotation.

Purpose: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). Methods: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. Results: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). Conclusions: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.

The effect of lateral decubitus position on intraocular pressure in healthy young subjects

Purpose:  To investigate the effect of change of body posture from supine to lateral decubitus position (LDP) on intraocular pressure (IOP) in healthy young subjects.

The effect of head tilt on the measurements of retinal nerve fibre layer and macular thickness by spectral-domain optical coherence tomography

Background/aims To evaluate the effect of head tilt on retinal nerve fibre layer (RNFL) and macular thickness measured by the Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT). Methods A total of 30 right eyes from 30 healthy young subjects underwent RNFL and macular thickness measurements with the Cirrus HD OCT. The measurements were performed at a baseline head position and at right and left head tilt positions. The differences in RNFL and macular thickness between the baseline head position and the positions with head tilt were analysed. Results The right and left head tilt induced counter-clockwise (mean 8.27°) and clockwise (mean 8.47°) rotation of the optic disc. The right head tilt caused superior-temporal RNFL thickening, inferior-temporal RNFL thinning, superior outer macular thickening and inferior outer macular thinning (all p values <0.05). The left head tilt induced superior-temporal RNFL thinning, inferior-temporal RNFL thickening, superior outer macular thinning, nasal outer macular thickening and inferior outer macular thickening (all p values <0.05). Conclusions RNFL and macular thickness measured with the Cirrus HD OCT was affected by head tilt. Artefacts caused by head tilt should be considered in the analysis of the Cirrus HD OCT measurements.

Macular Ganglion Cell Analysis for Early Detection of Glaucoma

PURPOSE To investigate the ability of Cirrus high-definition optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) macular ganglion cell analysis (GCA) sector, deviation, and thickness maps to detect early glaucoma. DESIGN Cross-sectional study. PARTICIPANTS We enrolled 131 eyes with early glaucoma (mean deviation >-6.0 dB) and 132 age- and refractive error-matched healthy eyes. METHODS Macular GCA maps were obtained using Cirrus HD-OCT. The location, angular distance, and width of circumpapillary retinal nerve fiber layer (RNFL) defects were investigated by using red-free fundus photographs. The presence of a structural abnormality in the GCA map was defined as (1) yellow/red color codes in the sector map, (2) yellow/red pixels (>10) in the deviation map, and (3) blue areas in the thickness map. MAIN OUTCOME MEASURES The prevalence of and factors associated with the presence or absence of abnormal GCA findings were assessed. RESULTS Among the 131 glaucomatous eyes, 105 (80.2%), 115 (87.8%), and 104 (79.4%) showed structural abnormalities in the GCA sector, deviation, and thickness maps, respectively. The absence of abnormal findings in the GCA maps of glaucomatous eyes was associated with the presence of RNFL defects in the superior hemisphere, a greater angular distance between the fovea and the RNFL defect, a narrower width of the RNFL defect, less severe visual field defects, or an isolated peripheral nasal step (outside 10 degrees of fixation) (P<0.05). A greater angular distance of the RNFL defect remained significant in multivariate analyses (P<0.05). Among the 132 healthy eyes, 28 (21.2%), 37 (28.0%), and 20 (15.2%) had abnormal findings in the GCA sector, deviation, and thickness maps, respectively. The presence of abnormal GCA findings in healthy eyes was associated with a higher degree of myopic refractive error (P<0.05). CONCLUSIONS Cirrus HD-OCT GCA maps showed a good ability to detect early glaucoma. However, GCA maps did not show abnormal findings in glaucomatous eyes when the angular distance between fovea and RNFL defect was great. These findings should be considered when diagnosing early glaucoma using GCA maps.

Ability of cirrus high-definition spectral-domain optical coherence tomography clock-hour, deviation, and thickness maps in detecting photographic retinal nerve fiber layer abnormalities

PURPOSE To investigate the ability of clock-hour, deviation, and thickness maps of Cirrus high-definition spectral-domain optical coherence tomography (HD-OCT) in detecting retinal nerve fiber layer (RNFL) defects identified in red-free fundus photographs in eyes with early glaucoma (mean deviation >-6.0 dB). DESIGN Cross-sectional study. PARTICIPANTS Two hundred ninety-five eyes with glaucomatous RNFL defects with clear margins observed in red-free fundus photographs and 200 age-, sex-, and refractive error-matched healthy eyes were enrolled. METHODS The width and location of RNFL defects were evaluated by using the red-free fundus photograph. When a RNFL defect detected by red-free fundus photograph did not present as (1) yellow/red codes in the clock-hour map, (2) yellow/red pixels in the deviation map, or (3) blue/black areas in the thickness map, the event was classified as a misidentification of a photographic RNFL defect by Cirrus HD-OCT. In healthy eyes, the presence of false-positive RNFL color codes of Cirrus HD-OCT maps was investigated. MAIN OUTCOME MEASURES The prevalence of and factors associated with the (1) misidentification of photographic RNFL defects by Cirrus HD-OCT in eyes with glaucoma and (2) false-positive RNFL color codes of Cirrus HD-OCT maps in healthy eyes were assessed. RESULTS Among the 295 red-free fundus photographic RNFL defects from 295 eyes with glaucoma, 83 (28.1%), 27 (9.2%), and 0 (0%) defects were misidentified in the clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively. Fifty-six defects (19.0%) were misidentified only in the clock-hour map and 27 (9.2%) in both the clock-hour and deviation maps. The misidentification of photographic RNFL defects by Cirrus HD-OCT was associated with a narrower width and a temporal location of RNFL defects (P<0.05). Among the 200 healthy eyes, 25 (12.5%), 30 (15.0%), and 12 (6.0%) eyes had false-positive RNFL color codes in clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively. CONCLUSIONS Among the clock-hour, deviation, and thickness maps obtained with Cirrus HD-OCT, the thickness map showed the best diagnostic ability in detecting photographic RNFL defects. The RNFL thickness map may be a useful tool for the detection of RNFL defects in eyes with early glaucoma.

Glaucoma diagnostic ability of quadrant and clock-hour neuroretinal rim assessment using cirrus HD optical coherence tomography.

PURPOSE The aim of this study was to investigate the glaucoma diagnostic ability of quadrant and clock-hour neuroretinal rim assessment by Cirrus HD spectral-domain optical coherence tomography (OCT). METHODS Eighty eyes of 80 glaucoma patients and 80 eyes of 80 healthy subjects were enrolled. Peripapillary retinal nerve fiber layer (RNFL) thickness was measured by Cirrus HD-OCT. Quadrant and clock-hour rim areas and thicknesses were obtained from optic nerve head images and 360° circumferential rim thickness curve of Cirrus HD-OCT, respectively. Area under receiver operating characteristic curves (AUCs) and sensitivities of RNFL thicknesses, rim areas, and rim thicknesses at a 90% specificity level were calculated. RESULTS Quadrant and clock-hour rim area and thickness showed good diagnostic ability for glaucoma in all areas (AUCs, 0.877-0.969; sensitivities, 67.5%-96.3%). When the AUCs of RNFL thicknesses, rim areas, and rim thicknesses were compared, no significant difference was found in global area and superior and inferior quadrants (P > 0.05). However, in nasal and temporal quadrants, rim area and thickness had greater AUCs (AUCs, 0.919-0.945; sensitivities, 82.5%-86.3%) than RNFL thickness (AUCs, 0.749-0.776; sensitivities, 12.5%-33.8%; P < 0.001). Eyes with moderate to advanced glaucoma (mean deviation < -6 dB) had thinner RNFL than mild glaucoma (mean deviation ≥ -6 dB) in global area, superior, inferior, and temporal quadrants (P < 0.003); rim area and thickness showed no significant difference in all areas (P > 0.003). CONCLUSIONS Neuroretinal rim assessment in nasal and temporal areas by Cirrus HD-OCT may enhance glaucoma diagnostic ability. RNFL and rim changes measured by Cirrus HD-OCT may be different according to the stages of glaucomatous damage.

Errors in neuroretinal rim measurement by Cirrus high-definition optical coherence tomography in myopic eyes

Background/aims To investigate the prevalence of, and factors associated with, errors in neuroretinal rim measurement by Cirrus high-definition (HD) spectral-domain optical coherence tomography (OCT) in myopic eyes. Methods Neuroretinal rim thicknesses of 255 myopic eyes were measured by Cirrus HD-OCT. The prevalence of, and factors associated with, optic disc margin detection error and cup margin detection error were assessed by analysing 72 cross-sectional optic nerve head (ONH) images obtained at 5° intervals for each eye. Results Among the 255 eyes, 45 (17.6%) had neuroretinal rim measurement errors; 29 (11.4%) had optic disc margin detection errors at the temporal (16 eyes), superior (11 eyes), and inferior (2 eyes) quadrants; 19 (7.5%) showed cup margin detection errors at the nasal (17 eyes) and temporal (2 eyes) quadrants; and 3 (1.2%) had both disc and cup margin detection errors. Errors in detection of temporal optic disc margin were associated with presence of parapapillary atrophy (PPA), higher myopia, and greater axial length (AL) (p<0.001). Cup margin detection errors were associated with vitreous opacities attached to the ONH surface or acute cup slope angles (p<0.001). Conclusions Errors in neuroretinal rim measurement by Cirrus HD-OCT were found in myopic eyes, especially in eyes with PPA, higher myopia, greater AL, vitreous opacity or acute cup slope angle. These findings should be considered when interpreting neuroretinal rim thickness measured by Cirrus HD-OCT.

Central Corneal Thickness in a Korean Population: The Namil Study

PURPOSE We investigated the distribution of central corneal thickness (CCT), and its association with age, sex, intraocular pressure (IOP), anterior chamber depth (ACD), axial length (AL), and the presence of systemic hypertension and diabetes in a Korean population. METHODS Our study is a population-based glaucoma prevalence study of residents aged ≥40 years in Namil-meon area, located in central South Korea. All subjects underwent a complete ophthalmic examination that included CCT measurement with an ultrasonic pachymeter, ACD and AL measurements by optical biometry, and Goldmann applanation tonometry. The right eye of all subjects was analyzed. RESULTS The mean (SD) CCT of the 1259 right eyes was 530.9 (31.5) μm. In univariate analysis, a thicker CCT was associated with a higher IOP (P < 0.001), a longer AL (P = 0.003), and a younger age (P < 0.001). ACD was not correlated significantly with CCT (P = 0.087). Men had a 5.7 μm higher CCT than women (age adjusted, P = 0.001). Subjects with hypertension had a 4.1 μm lower CCT than those without hypertension (age, sex-adjusted, P = 0.027), and the presence of diabetes was not associated significantly with CCT (age, sex-adjusted, P = 0.892). In multivariate analysis, a higher CCT was associated with a higher IOP (P < 0.001), younger age (P = 0.001), male sex (P = 0.005), and the absence of hypertension (P = 0.018). CONCLUSIONS The mean CCT of a Korean population was 530.9 μm. CCT was associated with IOP, age, sex, and hypertension.

Astigmatism and optical coherence tomography measurements

BackgroundTo evaluate the effect of astigmatism change on measurement of retinal nerve fiber layer (RNFL) and macular thickness by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, CA, USA).MethodsA total of 30 right eyes from 30 healthy young subjects underwent RNFL and macular thickness measurements using Cirrus HD OCT. Measurements were performed at the baseline state and induced with-the-rule (WTR) and against-the-rule (ATR) astigmatism states by wearing toric soft contact lenses (+1.50 −3.25 diopter × 90° and +1.50 −3.25 diopter × 180° respectively). Dfferences in RNFL and macular thickness between the baseline state and induced astigmatism states were analyzed.ResultsWearing toric soft contact lenses induced a mean 2.92 diopter WTR and 3.18 diopter ATR astigmatism respectively. After signal strength change adjustment, RNFL thicknesses of average, superior quadrant, 12 and 6 o’clock hour sectors decreased after induction of a WTR astigmatism (mean difference range, 1.58 to 6.88 μm); RNFL thicknesses of average, nasal, temporal quadrants, 2, 3, and 9 o’clock hour sectors decreased after induction of an ATR astigmatism (mean difference range, 0.75 to 5.11 μm) (all P values <0.05). Macular thickness was not significantly affected by astigmatism changes (all P values ≥ 0.250).ConclusionAlthough the amount of change was not substantial, RNFL thickness measured by Cirrus HD OCT was affected by astigmatism changes induced by contact lenses. It may be warranted to consider the effect of astigmatism on RNFL thickness measured by OCT in eyes with higher degrees of astigmatism.