Choroidal Thickness After Dexamethasone Implant in RVO
Choroidal Thickness After Dexamethasone Implant in RVO
This prospective study was conducted on patients who required intravitreal dexamethasone implant (Ozurdex; Allergan, Irvine, California, USA) injections for the treatment of MO associated with RVO at Seoul National University Hospital during the period from February 2012 to February 2013. Informed consent was obtained from each patient prior to enrolment in the study and the Institutional Review Board of Seoul National University Hospital approved the study protocol. This study was conducted in accordance with the tenets of the Declaration of Helsinki.
The diagnosis of RVO was made by the physician via indirect ophthalmoscopic fundus evaluation and fluorescein angiography. MO was defined as a central subfield retinal thickness (central macular thickness, CMT) ≥300 μm using the 512×128 macular cube mode on the OCT (Cirrus high-definition (HD) OCT, Model 4000; Carl Zeiss Ophthalmic Instruments, Dublin, California, USA; 128 lines, 512 A-scans per line, scan area of 6×6 mm). The major study exclusion criteria were as follows: bilateral RVO; diabetic retinopathy; conditions that could affect choroidal thickness (eg, high myopia (spherical equivalent ≥−6.0 dioptres or axial length (AL) ≥26 mm), uveitis and a previous history of central serous chorioretinopathy or photodynamic therapy); media opacities that prevented assessment of the fovea (eg, cataract of more than Emery–Little classification grade III, vitreous haemorrhage and corneal opacity); previous intravitreal injections of triamcinolone acetonide or bevacizumab (Avastin; Genentech, South San Francisco, California, USA) ≤3 months prior to enrolment; and any history of intraocular surgery.
A complete ocular examination, including measurement of BCVA on a Snellen chart, tonometry, AL (Axis II PR; Quantel Medical, Bozeman, Montana, USA) measurement, slit-lamp biomicroscopy, dilated fundus examination, fundus photography (Vx-10; Kowa Optimed, Tokyo, Japan), fluorescein angiography (Vx-10; Kowa Optimed) and OCT imaging, was conducted on each patient. After the Ozurdex injection, measurement of BCVA, tonometry, slit-lamp biomicroscopy, dilated fundus examination and OCT were repeated at each follow-up visit. The first follow-up visit was scheduled at 1 month after the injection and all subsequent visits were scheduled every other month thereafter. Measurements for BCVA were converted to logarithm of the minimum angle of resolution (logMAR) units for statistical analyses.
Choroidal thickness was measured by enhanced depth imaging-OCT using a Cirrus HD-OCT. The scan pattern selected was the 5-line raster, which is a 6 mm line consisting of 20 480 A-scans with an imaging speed of 27 000 A-scans per second, for an average of 20 frames (B-scans). The location of the fovea within each volume scan was identified automatically with the built-in Fovea Finder algorithm of the Cirrus, resulting in good reproducibility. The resultant images were viewed and measured using the built-in software (V.6.0.2.81; Carl Zeiss Ophthalmic Instruments). The choroid was measured from the outer edge of the retinal pigment epithelium (RPE) to the inner edge of the suprachoroidal space below the fovea. Measurements of SFCT were obtained at the subfoveal region via manual measurement using callipers provided by the instrument's software. The retinal specialist who was masked to the clinical data performed the analysis. Comparisons between the eyes were made using the measurements for both eyes in the corresponding visit.
A paired t test was used to compare CMT and SFCT in eyes with RVO and normal contralateral eyes. Serial comparisons of the mean CMT and SFCT were conducted using Wilcoxon signed-rank test. Comparisons of the mean CMT and SFCT between the two subgroups—BRVO and CRVO—were analysed using the Mann–Whitney U test. The correlations between the CMT and SFCT and between the change in visual acuity and changes in CMT or SFCT were analysed using the Pearson's test. The statistical significance level was set as p<0.05. All statistical analyses were performed using SPSS V.21.0 for Windows (SPSS, Chicago, Illinois, USA).
Materials and Methods
Subjects
This prospective study was conducted on patients who required intravitreal dexamethasone implant (Ozurdex; Allergan, Irvine, California, USA) injections for the treatment of MO associated with RVO at Seoul National University Hospital during the period from February 2012 to February 2013. Informed consent was obtained from each patient prior to enrolment in the study and the Institutional Review Board of Seoul National University Hospital approved the study protocol. This study was conducted in accordance with the tenets of the Declaration of Helsinki.
The diagnosis of RVO was made by the physician via indirect ophthalmoscopic fundus evaluation and fluorescein angiography. MO was defined as a central subfield retinal thickness (central macular thickness, CMT) ≥300 μm using the 512×128 macular cube mode on the OCT (Cirrus high-definition (HD) OCT, Model 4000; Carl Zeiss Ophthalmic Instruments, Dublin, California, USA; 128 lines, 512 A-scans per line, scan area of 6×6 mm). The major study exclusion criteria were as follows: bilateral RVO; diabetic retinopathy; conditions that could affect choroidal thickness (eg, high myopia (spherical equivalent ≥−6.0 dioptres or axial length (AL) ≥26 mm), uveitis and a previous history of central serous chorioretinopathy or photodynamic therapy); media opacities that prevented assessment of the fovea (eg, cataract of more than Emery–Little classification grade III, vitreous haemorrhage and corneal opacity); previous intravitreal injections of triamcinolone acetonide or bevacizumab (Avastin; Genentech, South San Francisco, California, USA) ≤3 months prior to enrolment; and any history of intraocular surgery.
Examinations and Data Collection
A complete ocular examination, including measurement of BCVA on a Snellen chart, tonometry, AL (Axis II PR; Quantel Medical, Bozeman, Montana, USA) measurement, slit-lamp biomicroscopy, dilated fundus examination, fundus photography (Vx-10; Kowa Optimed, Tokyo, Japan), fluorescein angiography (Vx-10; Kowa Optimed) and OCT imaging, was conducted on each patient. After the Ozurdex injection, measurement of BCVA, tonometry, slit-lamp biomicroscopy, dilated fundus examination and OCT were repeated at each follow-up visit. The first follow-up visit was scheduled at 1 month after the injection and all subsequent visits were scheduled every other month thereafter. Measurements for BCVA were converted to logarithm of the minimum angle of resolution (logMAR) units for statistical analyses.
Choroidal thickness was measured by enhanced depth imaging-OCT using a Cirrus HD-OCT. The scan pattern selected was the 5-line raster, which is a 6 mm line consisting of 20 480 A-scans with an imaging speed of 27 000 A-scans per second, for an average of 20 frames (B-scans). The location of the fovea within each volume scan was identified automatically with the built-in Fovea Finder algorithm of the Cirrus, resulting in good reproducibility. The resultant images were viewed and measured using the built-in software (V.6.0.2.81; Carl Zeiss Ophthalmic Instruments). The choroid was measured from the outer edge of the retinal pigment epithelium (RPE) to the inner edge of the suprachoroidal space below the fovea. Measurements of SFCT were obtained at the subfoveal region via manual measurement using callipers provided by the instrument's software. The retinal specialist who was masked to the clinical data performed the analysis. Comparisons between the eyes were made using the measurements for both eyes in the corresponding visit.
Statistical Analysis
A paired t test was used to compare CMT and SFCT in eyes with RVO and normal contralateral eyes. Serial comparisons of the mean CMT and SFCT were conducted using Wilcoxon signed-rank test. Comparisons of the mean CMT and SFCT between the two subgroups—BRVO and CRVO—were analysed using the Mann–Whitney U test. The correlations between the CMT and SFCT and between the change in visual acuity and changes in CMT or SFCT were analysed using the Pearson's test. The statistical significance level was set as p<0.05. All statistical analyses were performed using SPSS V.21.0 for Windows (SPSS, Chicago, Illinois, USA).