Ki Bang Uhm

Reduction in intraocular pressure after laser in situ keratomileusis.

Purpose: To investigate whether intraocular pressure (IOP) measured on the nasal side is affected after laser in situ keratomileusis (LASIK). Setting: The Glaucoma Service, Dr. Hongs Eye Clinic, Seoul, Korea. Methods: In 83 patients, IOP was prospectively measured with the Goldmann tonometer at the central (Tcenter) and nasal (Tnasal) areas of the cornea before and after LASIK. The Tcenter and Tnasal IOP between baseline and 1, 3, and 6 months postoperatively was compared. The correlation between ablation depth, amount of treatment, refractive change, and change in central corneal thickness and Tcenter change was evaluated. Results: Six months after LASIK, Tcenter IOP decreased 3.9 mm Hg (25.2%) and Tnasal IOP decreased 2.0 mm Hg (12.7%) (P < .001, P = .02, respectively). The Tnasal measurement was 1.8 mm Hg higher than the Tcenter measurement (P < .001). Significant correlation between each corneal parameter and the Tcenter reduction at 1 month did not continue to 6 months (P gt; .05). Conclusion: At each follow‐up, Tnasal IOP was statistically lower than at baseline, although the reduction was not as great as that of Tcenter IOP. A 2 to 3 mm Hg drop in Tnasal up to 6 months after LASIK should be expected. An alternative would be to measure IOP with the Tono‐Pen® on the nasal side to fit the tip to the relatively unchanged nasal side of the cornea.

A Case of Optic Nerve Atrophy with Severe Disc Cupping after Methanol Poisoning

We report a rare case of optic nerve atrophy with severe disc cupping resulting from methanol poisoning. A 30-year-old man presented to the hospital complaining of decreased visual acuity in both eyes a day after drinking alcohol containing methanol. His initial visual acuity allowed for only visualizing hand motion and not corrected in either eye. Initial intraocular pressure was within normal limits in both eyes. Initial fundus examination showed optic disc swelling in both eyes. Four years later, he visited our hospital for an eye evaluation. Visual acuity in both eyes still only allowed for visualizing hand motion. No nystagmus was observed in either eye during the optokinetic nystagmus test, and no waves were found in a visual evoked potential test. No specific change was noted on brain magnetic resonance imaging. On fundus examination, there was disc pallor in both eyes and disc cupping with a high cup/disc (C/D) ratio above 0.9 in the left eye. C/D ratio of the right eye was 0.5. Methanol poisoning may induce glaucomatous disc cupping in the late stage as well as optic atrophy. One possible mechanism of disc cupping is ganglion cell loss due to acute demyelination of the retrobulbar optic nerve. This report is the first photographic evidence of methanol induced optic disc cupping in Korea.

Optic Disc Pit with Peripapillary Retinoschisis Presenting as a Localized Retinal Nerve Fiber Layer Defect

A 59-year-old woman was referred to our clinic for a glaucoma evaluation. The visual acuity and intraocular pressure were normal in both eyes. However, red-free fundus photography in the left eye showed a superotemporal wedge-shaped retinal nerve fiber layer defect, and visual field testing showed a corresponding partial arcuate scotoma. In an optical coherence tomography examination, the macula was flat, but an arcuate-shaped peripapillary retinoschisis was found. Further, the retinoschisis seemed to be connected with a superotemporal optic pit shown in a disc photograph. After 3 months of a topical prostaglandin analogue medication, the intraocular pressure in the retinoschisis eye was lowered from 14 to 10 mmHg and the peripapillary retinoschisis was almost resolved. We report a rare case of an optic disc pit with peripapillary retinoschisis presenting as a localized retinal nerve fiber layer defect.

Retinal Nerve Fiber Layer Thickness Measurement Repeatability for Cirrus HD-OCT Retinal Tracking System During Eye Movement.

Purpose:To investigate the repeatability of peripapillary retinal nerve fiber layer (RNFL) thickness measurements obtained using Cirrus high-definition optical coherence tomographic (Cirrus HD-OCT) retinal tracking system during various types of eye movements. Materials and Methods:We included 20 healthy eyes, 40 glaucomatous eyes of elderly patients, and 17 eyes with pathologic nystagmus. For healthy eyes, RNFL thickness measurements were obtained under 3 conditions: (1) without eye movement, fixated on the device’s internal target, (2) with horizontal eye movement, and (3) with vertical eye movement during scan acquisition. Each session was performed 3 times with and without the use of the retinal tracking system. The repeatability of RNFL thickness measurements obtained with and without the retinal tracking was compared within each session and among the sessions. Results:In healthy eyes, measurements obtained without the use of a retinal tracking system showed lower repeatability when measurements were obtained with eye movements than without (P<0.05). However, when retinal tracking system was used, measurement repeatability under conditions with eye movements was similar to that achieved without eye movement (P>0.05) and higher than that obtained without the use of a retinal tracking system (P<0.05). In elderly glaucomatous patients, the retinal tacking system did not significantly improve measurement repeatability during fixation (P>0.05). In eyes with pathologic nystagmus, the tracking system did not follow eye movement and scan acquisition was not processed. Conclusions:Cirrus HD-OCT retinal tracking system may enhance RNFL thickness measurement repeatability under certain, but not all, eye movement conditions.

Retinal nerve fiber layer volume measurements in healthy subjects using spectral domain optical coherence tomography.

Purpose:To report retinal nerve fiber layer (RNFL) volume measurement using spectral domain optical coherence tomography (SD-OCT). We determined the characteristics and effecting factors of the RNFL volume in healthy eyes. Methods:Eighty-six eyes from 86 healthy volunteers were included. All participants underwent 3D-disc scanning using SD-OCT. We developed a computer program using Matlab software to extract RNFL thickness values from colored topographic RNFL thickness map. Total average, quadrant, and clock-hour RNFL volume were automatically calculated between 2.5 and 5 mm diameter circles using the length, width, and height of each pixel derived from the RNFL thickness map. Results:The mean total RNFL volume was 1.478±0.124 mm3 and RNFL volume profiles showed double-hump patterns. RNFL volumes of superior and inferior quadrants were significantly greater than those of temporal and nasal quadrants (all P<0.001). A strong correlation existed between RNFL volume and conventional circumpapillary RNFL thickness measured by built-in software (R=0.895 to 0.972). Image quality and age were associated with RNFL volume measurement. Conclusions:RNFL volume measurement from RNFL thickness map analysis provides an alternative approach to characterizing and evaluating RNFL. RNFL volume measurement may be valuable for the objective and quantitative evaluation of 3-dimensional RFNL changes.

Peripapillary Microvascular Improvement and Lamina Cribrosa Depth Reduction After Trabeculectomy in Primary Open-Angle Glaucoma

Purpose To evaluate peripapillary microvascular changes in patients with primary open-angle glaucoma (POAG) after trabeculectomy using optical coherence tomography (OCT) angiography, and to determine the influence of lamina cribrosa (LC) displacement on changes in peripapillary microvasculature. Methods The peripapillary retinal microvasculature and LC were imaged using OCT angiography and OCT-enhanced depth imaging, respectively. The microvasculature and LC depth (LCD) were measured before, and 1 week, 1 month, and 3 months after trabeculectomy. The microvascular improvement was arbitrarily defined as a reduction >30% of the area of vascular dropout (blue/black areas with <20% vessel density on the color-coded vessel density map). LCD was determined as the mean of vertical distance between the anterior LC surface and a reference plane of Bruchs membrane. Results Thirty-one eyes of 31 POAG patients were included. At 3 months postoperatively, intraocular pressure (IOP) and LCD were significantly decreased from 26.3 ± 11.8 mm Hg to 12.5 ± 3.6 mm Hg, and 501.1 ± 130.2 μm to 455.8 ± 112.7 μm, respectively (all P < 0.001), compared with baseline. The microvascular improvement was observed in 19 eyes (61.3%) at 3 months after trabeculectomy. The maximal reductions in IOP and LCD were significantly greater in eyes with improved microvasculature compared to eyes without improvement (P = 0.020 and P = 0.005). The microvascular improvement was significantly associated with maximal reduction in LCD (odds ratio, 1.062; P = 0.026). Conclusions Trabeculectomy can improve peripapillary retinal microcirculation in patients with POAG. This finding suggests that the reduction of LCD induced by lowering IOP may affect peripapillary microvascular improvement in eyes with POAG.

Quantitative analysis of localized retinal nerve fiber layer defects using spectral domain optical coherence tomography.

Purpose:To compare the topographic features of localized retinal nerve fiber layer (RNFL) defects presented in red-free RNFL photography and spectral domain optical coherence tomography (SD-OCT), and to evaluate the correlation with structural and functional parameters. Methods:Sixty eyes with localized RNFL defects in red-free RNFL photographs were included. RNFL thickness map and significance map were obtained by SD-OCT. The angular location, angular width, and area of localized RNFL defects were measured and compared among RNFL thickness map, significance map (red, <1% level; yellow, <5% level), and RNFL photograph. The RNFL defect areas were analyzed by their correlations with structural and functional parameters. Results:The RNFL defect area of RNFL thickness map was significantly greater than those of red significance map, and smaller than those of RNFL photograph and yellow significance map (all P<0.001). RNFL thickness map showed a significantly narrower angular width than RNFL photograph and yellow significance map (all P<0.001). The area, angular width, and angular location of localized RNFL defects in RNFL photographs strongly correlated with those of RNFL thickness maps and significance maps (all r≥0.741, P<0.001). The relationship between RNFL defect area and structural-functional parameters was also significant. Conclusions:The high topographic correlations in RNFL defects between RNFL photography and SD-OCT RNFL maps suggest the validity of SD-OCT RNFL imaging for detecting localized glaucomatous RNFL damage. In addition, structural and functional parameters are closely related to RNFL defect areas. Quantitative measurements of RNFL defects might be valuable for glaucoma diagnosis.

The Effect of Optic Disc Center Displacement on Retinal Nerve Fiber Layer Measurement Determined by Spectral Domain Optical Coherence Tomography

Purpose To investigate the effect of optic disc center displacement on retinal nerve fiber layer (RNFL) measurement determined by spectral domain optical coherence tomography (SD-OCT). Methods The optic disc center was manipulated at 1-pixel intervals in horizontal, vertical, and diagonal directions. According to the manipulated optic disc center location, the RNFL thickness data were resampled: (1) at a 3.46-mm diameter circle; and (2) between a 2.5-mm diameter circle and 5.4-mm square. Error was calculated between the original and resampled RNFL measurements. The tolerable error threshold of the optic disc center displacement was determined by considering test-retest variability of SD-OCT. The unreliable zone was defined as an area with 10% or more variability. Results The maximum tolerable error thresholds of optic disc center displacement on the RNFL thickness map were distributed from 0.042 to 0.09 mm in 8 directions. The threshold shape was vertically elongated. Clinically important unreliable zones were located: (1) at superior and inferior region in the vertical displacement; (2) at inferotemporal region in the horizontal displacement, and (3) at superotemporal or inferotemporal region in the diagonal displacement. The unreliable zone pattern and threshold limit varied according to the direction of optic disc displacement. Conclusions Optic disc center displacement had a considerable impact on whole RNFL thickness measurements. Understanding the effect of optic disc center displacement could contribute to reliable RNFL measurements.

Diagnostic Ability of Retinal Nerve Fiber Layer Thickness Deviation Map for Localized and Diffuse Retinal Nerve Fiber Layer Defects

Purpose. To evaluate the diagnostic ability of the retinal nerve fiber layer (RNFL) deviation map for glaucoma with localized or diffuse RNFL defects. Methods. Eyes of 139 glaucoma patients and 165 healthy subjects were enrolled. All participants were imaged with Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA, USA). A RNFL defect was defined as at least 10 contiguous red (<1% level) superpixels in RNFL deviation map. The area, location, and angular width of RNFL defects were automatically measured. We compared sensitivities, specificities, and area under the receiver operating characteristic curves (AUCs) of RNFL deviation map and circumpapillary RNFL thickness for localized and diffuse RNFL defects. Subgroup analysis was performed according to the severity of glaucoma. Results. For localized defects, the area of RNFL defects (AUC, 0.991; sensitivity, 97%; specificity, 90%) in deviation map showed a higher diagnostic performance (p = 0.002) than the best circumpapillary RNFL parameter (inferior RNFL thickness; AUC, 0.914; sensitivity, 79%; specificity, 92%). For diffuse defects, there was no significant difference between the RNFL deviation map and circumpapillary RNFL parameters. In mild glaucoma with localized defect, RNFL deviation map showed a better diagnostic performance than circumpapillary RNFL measurement. Conclusions. RNFL deviation map is a useful tool for evaluating glaucoma regardless of localized or diffuse defect type and has advantages over circumpapillary RNFL measurement for detecting localized RNFL defects.