The effect of center point shift on the measurement of macular thickness: a spectral domain-optical coherence
Kyoung Nam Kim1, Il Hwan Shin1, Jae Yun Sung1
1Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea.
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.
