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

Identification of Postoperative Foveal Displacement after Macular Surgery for Idiopathic Epiretinal Membrane

Introduction: To analyze foveal displacement after macular surgery for idiopathic epiretinal membrane (iERM). Methods: Twenty-eight patients who underwent macular surgery for symptomatic iERM in one eye by one physician were included in this retrospective study. Spectral domain optical coherence tomography (SD-OCT) volume scans were acquired with a Spectralis OCT device (Heidelberg Spectralis). Using the follow-up view mode, the displacement of the fovea was classified and measured according to its postoperative location in the horizontal and/or vertical plane. Results: One day after surgery, 86% of eyes (24/28) showed foveal displacement. Vertical displacement occurred in a superior direction in 50% eyes, and in an inferior direction in 36% of the eyes. The postoperative mean foveal displacement on the vertical plane was 99 ± 82 μm (range, 0-300). Horizontal displacement occurred in a nasal direction in 21%, and temporally in 21%. The postoperative mean foveal displacement on the horizontal plane was 35 ± 45 μm (range, 0-123). One year after the macular surgery 69% of the eyes showed still a foveal dislocation. Discussion: Most of the eyes with iERM showed a foveal dislocation after the macular surgery. Our findings emphasize the necessity to carefully study of the OCT images in such eyes after the surgery as the manually determined postoperative foveal position may be in a different vertical or horizontal plane than the machine-generated pre- and postoperative overlay for the foveal position. Our findings may thus be helpful for surgeons to avoid misinterpretation when evaluating OCT images pre- and postoperatively.

Repeatability of ganglion cell-inner plexiform layer thickness measurements using spectral-domain OCT in branch retinal vein occlusion

PURPOSE

To analyze the repeatability of thickness measurements of the central macula, ganglion cell-inner plexiform layer (GC-IPL), and retinal nerve fiber layer (RNFL) using spectral-domain optical coherence tomography (SD-OCT) before and after treatment of macular edema in branch retinal vein occlusion (BRVO).

METHODS

We analyzed patients with BRVO who visited our retinal clinic. The repeatability of the thickness measurements were compared using the intraclass correlation coefficient (ICC) and coefficient of variation (COV) of affected versus normal fellow eyes.

RESULTS

The average thicknesses of the central macula, RNFL, and GC-IPL were 371.28 μm, 105.60 μm, and 61.88 μm, respectively, in affected eyes with macular edema before treatment, and the ICCs were 0.978, 0.919, and 0.705, respectively. The average thicknesses were 244.98 μm, 96.70 μm, and 82.70 μm, respectively, in affected eyes without macular edema after treatment, and the ICCs were 0.999, 0.975, and 0.928, respectively. After resolution of macular edema, the average thickness of the GC-IPL increased, whereas that of the central macula and RNFL significantly decreased (P < 0.05); all of the ICCs increased compared to pretreatment values. In normal fellow eyes, the average thicknesses were 250.98 μm, 93.50 μm, and 83.84 μm, respectively, and the ICCs were 0.996, 0.995, and 0.994, respectively.

CONCLUSIONS

After treatment of macular edema, the repeatability and thickness of the GC-IPL increased, along with reduction in the central macular thickness. This resulted from auto-segmentation errors following macular contour changes and unstable gazes of the patients due to decreased visual acuities in BRVO with macular edema.