Effects of Measurement Center Shift on Ganglion Cell-inner Plexiform Layer Thickness Measurements.

SIGNIFICANCE: Our authors studied the effects of measurement center shift on ganglion cell-inner plexiform layer (GCIPL) thickness measurements in Cirrus spectral-domain optical coherence tomography (SD-OCT). The measurement center shift affects the GCIPL thickness measurement depending on the distance of shift. PURPOSE: The purpose of this study was to explore changes in macular GCIPL thicknesses measurements after manual shifting of the measurement center using SD-OCT. METHODS: A prospective study was conducted. A total of 30 normal eyes of 30 subjects were included in the study. An experienced examiner obtained two consecutive measurements of GCIPL thickness using SD-OCT. Coefficients of repeatability were calculated for the average, minimum, and sectoral (superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal) thicknesses. Next, the measurement center was manually shifted from the foveal center. Three measurement centers were horizontally placed at 59-µm intervals from the foveal center, and two further centers were placed 176 µm apart. Also, three measurement centers were vertically placed at 47-µm intervals from the foveal center, and two further centers were placed 142 µm apart. The thickness of GCIPL was measured again at each shift point, and the changes of thickness before and after movement were analyzed. RESULTS: When the measurement centers were shifted to positions 59 µm horizontally or 47 µm vertically from the fovea, no significant changes in GCIPL thicknesses were evident. However, upon more pronounced shifting, the average GCIPL thickness of the direction of the shift region was significantly lower than baseline, whereas the GCIPL of the diametrically opposite sector was thicker than baseline. CONCLUSIONS: The impact of changes associated with shifting of the measurement center should be taken into consideration when measuring GCIPL thickness in patients with retinal diseases, glaucoma, or neuro-ophthalmological conditions.

THICKNESS OF THE MACULA, RETINAL NERVE FIBER LAYER, AND GANGLION CELL-INNER PLEXIFORM LAYER IN THE AGE-RELATED MACULAR DEGENERATION: The Repeatability Study of Spectral Domain Optical Coherence Tomography.

PURPOSE: To determine the repeatability of measuring the thickness of the central macula, retinal nerve fiber layer, and ganglion cell-inner plexiform layer (GC-IPL) using spectral domain optical coherence tomography (Cirrus HD-OCT) in eyes with age-related macular degeneration. METHODS: One hundred and thirty-four eyes were included. The measurement repeatability was assessed by an experienced examiner who performed two consecutive measurements using a 512 × 128 macular cube scan and a 200 × 200 optic disk cube scan. To assess changes in macular morphology in patients with age-related macular degeneration, the patients were divided into the following three groups according to the central macular thickness (CMT): A group, CMT < 200 µm; B group, 200 µm ≤ CMT < 300 µm; and C group, CMT > 300 µm. RESULTS: Measurement repeatability was assessed using test-retest variability, a coefficient of variation, and an intraclass correlation coefficient. The mean measurement repeatability for the central macular, retinal nerve fiber layer, and GC-IPL thickness was high in the B group. The mean measurement repeatability for both the central macula and retinal nerve fiber layer thickness was high in the A and C groups, but was lower for the GC-IPL thickness. The measurement repeatability for GC-IPL thickness was high in the B group, but low in the A group and in the C group. CONCLUSION: The automated measurement repeatability for GC-IPL thickness was significantly lower in patients with age-related macular degeneration with out of normal CMT range. The effect of changes in macular morphology should be considered when analyzing GC-IPL thicknesses in a variety of ocular diseases.

The effect of center point shift on the measurement of macular thickness: a spectral domain-optical coherence tomography study.

PURPOSE: To evaluate the effect of spectral domain-optical coherence tomography (SD-OCT) measurement center shift on the measurement of macular thickness. METHODS: This was a prospective observational case series. A total of 60 normal eyes of 60 subjects included in the study. SD-OCT macular scanning (macular cube 512 × 128 scan) was performed twice by an experienced examiner. The average retinal thicknesses of the nine macular sectors as defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) were recorded. Each coefficient of repeatability was calculated for the macular thickness measurements of the ETDRS subfields. Thereafter, the measurement center was manually decentered to a seven scan point, each from the central fovea in steps of 58.7 µm horizontally and 47.2 µm vertically. At each shift point, the change in the macular thickness was compared. RESULTS: When the displacement distance between the measurement center point and the foveal center was within 117.4 µm horizontally and 141.6 µm vertically, the macular thickness measurements did not show any significant differences. However, if the offset of the EDTRS grid center from the anatomic fovea exceeded, we noted that the thickness at the fovea increased and the opposite-direction region at the inner circle was significantly thinner than the displaced point. CONCLUSIONS: The effect of measurement center shift needs to be considered when analyzing the macular thickness measurements in various ophthalmologic diseases.

Longitudinal Changes in Retinal Nerve Fiber Layer Thickness after Intravitreal Anti-vascular Endothelial Growth Factor Therapy.

PURPOSE: To determine the effects of intravitreal anti-vascular endothelial growth factor (VEGF) on thickness of the retinal nerve fiber layer (RNFL) in patients with age-related macular degeneration. METHODS: Twenty eyes of 20 patients diagnosed with age-related macular degeneration who underwent intravitreal anti-VEGF injection were studied. Postinjection RNFL thickness was measured using optical coherence tomography. Average thickness, four-quadrant RNFL thicknesses, and intraocular pressure (IOP) in affected eyes were measured before and 6 and 12 months after anti-VEGF injection for comparison. RNFL thickness and IOP in affected and normal fellow eyes were also compared. Given that macular lesions can affect RNFL thickness, the changes in thickness were evaluated by dividing the 12 clock-hour RNFL into the pathologic areas adjacent to the lesion and the non-pathologic area. RESULTS: The mean clock-hour segment in the pathologic area was 4.8 hours. A significantly thicker RNFL was exhibited in temporal quadrants and pathologic areas (p = 0.043 and 0.048, respectively) in affected eyes before injection compared to the baseline RNFL thickness in normal eyes. No significant differences were found in RNFL thickness or IOP between affected and normal eyes after injection. The changes over time in the temporal and pathologic areas were statistically significant at 6 and 12 months after injection compared to baseline data (p < 0.05). No significant differences were displayed in RNFL thickness in the other three quadrants or in non-pathologic areas in either affected or normal eyes. Sequential changes in RNFL thickness in affected eyes were not significant. CONCLUSIONS: Repeat intravitreal anti-VEGF treatment did not have a significant effect on RNFL thickness. RNFL thickness significantly decreased with time in the pathologic areas and in the temporal segment adjacent to exudative macular lesions. The reduction in RNFL thickness was most likely associated with changes in the macular lesion rather than with anti-VEGF injection.

Effects of Refractive Power on Macular Thickness Measurement Using Spectral-Domain Optical Coherence Tomography.

PURPOSE: To investigate the effects of refractive power on macular thickness measurements by spectral-domain optical coherence tomography (SD-OCT). SUBJECTS AND METHODS: For this prospective cohort study, a total of 50 eyes from 50 normal subjects with no systemic or ocular disease and no history of ocular surgery were studied from February 2014 to May 2014. We used soft contact lenses with a wide range of diopters to change the refractive power. The macular thickness of uncorrected eyes without contact lenses was measured by SD-OCT, and we compared the findings with the results of subsequent investigations in which macular thickness was measured in the presence of soft contact lenses of different diopters (-8, -4, 0, +4, and +8). We divided the patients into three groups according to the axial length (AL) and analyzed the effect of induced refraction change. The main outcome measure was macular thickness measured by OCT. RESULTS: The average age of the subjects was 28.0 ± 3.4 years (mean ± SD), and included 17 eyes with normal AL, 18 eyes with mid-range AL, and 15 eyes with long AL. The central macular thickness was 254.5 ± 17.5 µm for eyes without contact lenses, which was not significantly different from the measurements in the presence of plano contact lenses (254.2 ± 18.1 µm). Even with soft contact lenses of four different diopters (-8, -4, +4, and +8), central macular thickness (254.4 ± 16.2, 253.7 ± 17.3, 257.3 ± 17.9, and 256.9 ± 17.9 µm, respectively) was not significantly different from that of naked eyes in each group. CONCLUSION: These results suggest that central macular thickness measured by SD-OCT is unaffected by refractive power.