Yong Yeon Kim

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.

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.

Retinal vessel diameter, retinal nerve fiber layer thickness, and intraocular pressure in Korean patients with normal-tension glaucoma

PURPOSE To investigate the retinal vessel diameter and evaluate the relationship of the retinal nerve fiber layer (RNFL) thickness with retinal vessel diameter and intraocular pressure (IOP) in patients with normal-tension glaucoma (NTG). DESIGN A prospective, cross-sectional study. METHODS This study included 60 previously untreated patients with NTG (60 eyes) and 45 age- and sex-matched healthy controls (45 eyes) that had no history of systemic vascular disease at a single institution. The diameters of the central retinal arteries and veins were measured on retinal photographs. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were calculated using the revised Parr-Hubbard formula. The RNFL thickness was measured using Stratus optical coherence tomography. RESULTS The mean central retinal arteriolar (P = .000) and venular (P = .000) diameters were significantly smaller in the eyes with NTG than in the normal eyes. Multivariate linear regression analysis demonstrated a significant positive correlation between the RNFL thickness and CRAE (P = .014), and a negative correlation between the RNFL thickness and IOP (P = .005) in the eyes with NTG. However, there was no significant correlation between the RNFL thickness and the independent variables in the control group (P = .112). CONCLUSION The patients with NTG had smaller diameters of the central retinal vessels than the normal subjects. Both IOP and CRAE were significantly associated with RNFL thickness in the patients with NTG. Our results suggest that narrower retinal vessels and higher IOP may be related to the thinning of the RNFL in patients with NTG.

Effects of Different Sleeping Postures on Intraocular Pressure and Ocular Perfusion Pressure in Healthy Young Subjects

OBJECTIVE To investigate the effects of different sleeping positions of head and body on intraocular pressure (IOP) and ocular perfusion pressure (OPP) in healthy, young subjects. DESIGN Prospective, comparative case series. PARTICIPANTS Twenty healthy young Korean subjects. METHODS We measured IOP and blood pressure (BP) with the subjects seated and recumbent, including supine, right lateral decubitus, left lateral decubitus, prone with right head turn, and prone with left head turn positions. We measured IOP using an Icare tonometer in both eyes 5 minutes after assuming each position in a randomized sequence. We calculated the OPP using the formulas based on the mean BP adjusted for the height of the eye over the heart. The eye on the lower side in the lateral decubitus or prone with head turn position was termed the dependent eye. MAIN OUTCOME MEASURES Difference in IOP and OPP of the dependent and nondependent eyes during changes of sleeping positions of body and head. RESULTS Mean IOP of right and left eyes while sitting was significantly lower than that measured in each recumbent position (all P<0.001). The OPPs in both eyes were significantly higher in all recumbent positions than in a sitting position (all P<0.001). Mean IOP of the dependent eyes was higher than that of the nondependent eyes in the lateral decubitus positions and in the prone positions with head turns (all P<0.001). No significant intereye difference in OPP was found for any position. Among IOPs measured in the recumbent positions, mean IOP of the dependent eye in the lateral decubitus position or in the prone position with head turn was significantly higher than that of the ipsilateral eye in the supine position (all P<0.0001). CONCLUSIONS All sleeping positions of head and body resulted in an elevation of IOP and an increase in the calculated OPP compared with the sitting position in healthy, young subjects. The postural change from supine to lateral decubitus or prone with head turn position increased the IOP of the dependent eyes without significant alteration in OPP in healthy awake subjects. Further research is needed under nocturnal conditions in a sleep laboratory. FINANCIAL DISCLOSURES The authors have no proprietary or commercial interest in any of the materials discussed in this article.

An Investigation of Lateral Geniculate Nucleus Volume in Patients With Primary Open-Angle Glaucoma Using 7 Tesla Magnetic Resonance Imaging

PURPOSE To investigate lateral geniculate nucleus (LGN) volume of primary open-angle glaucoma (POAG) patients compared with age- and sex-matched controls using ultra-high field 7.0-T magnetic resonance imaging (MRI). METHODS The study included 18 patients with POAG and 18 age- and sex-matched healthy volunteers. All subjects underwent imaging on a high-resolution 7.0-T MRI system. Bilateral LGNs were identified and manually delineated, and LGN volumes were compared. Peripapillary retinal nerve fiber layer (pRNFL) thickness, optic nerve head parameters (including optic disc size, rim area, and cup-to-disc ratio), and combined thickness of the ganglion cell layer and inner plexus layer (GC-IPL) were measured by Cirrus high-definition optical coherence tomography (OCT). Correlations between OCT parameters and LGN volume were investigated. RESULTS Mean LGN volumes were significantly smaller in the POAG group than in the control group (right, glaucoma 83.97 mm(3) [SD ± 26.65] versus control 106.12 mm(3) [SD ± 24.32]; left, glaucoma 65.12 mm(3) [SD ± 29.41] versus control 92.70 mm(3) [SD ± 24.42], both P < 0.05). In the POAG group, average GC-IPL thickness was correlated with contralateral LGN volume (right LGN: r = 0.605, P = 0.008; left LGN: r = 0.471, P = 0.049). The correlation for right LGN volume remained significant after correction for multiple comparisons. However, there was no correlation between LGN volume and average pRNFL thickness or optic disc parameters in the POAG group. CONCLUSIONS On high-resolution 7.0-T MRI, LGN volumes in POAG patients are significantly smaller than those of healthy subjects. Furthermore, in patients, LGN volume was found to be significantly correlated with GC-IPL thickness of the contralateral eye.

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.

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.