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Abstract
Purpose
To investigate peripapillary retinal nerve fiber layer (RNFL) thickness profiles associated with myopia.
Methods
One hundred and twenty-seven normal eyes of 67 Korean adults were divided into three groups by spherical equivalent. All subjects were tested with fast RNFL scans of Stratus optical coherence tomography. The angular locations of superior and inferior maximal thickness points in relationship to a reference line drawn horizontally though the center of the scan circle were calculated from the raw data of scanned images (angle α, angle β). Differences of angle α and angle β were compared among the three groups.
References
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Figure 1.
From the thickness chart of Stratus OCT, we located superior and inferior maximal thickness points in all subjects. And the data was converted into angular location. Angular location of superior and inferior maximal thickness points were presented on red-free photography. A circle was placed around the optic nerve head and reference line (R) was drawn horizontally through the center of the circle. And the temporal meeting point of the line with the circle was set at 0°. Finally, we applied changed data based on line R (A). Line A was drawn from the optic disc center to superior maximal thickness point of peripapillary RNFL. Angle α was defined as directional angles of line R and line A. With the same method, line B was drawn from the optic disc center to inferior maximal thickness point. Angle β was defined as opposite directional angles of line R and line B (B).
Figure 2.
RNFL profiles and clock hour RNFL thickness of the group A (emmetropia to low myopia), group B (moderate myopia) and group C (high myopia). It shows a double-hump pattern, with peaks over the superotemporal (11 o'clock) and inferotemporal (7 o'clock) sectors. * Not significant differences.
Figure 3.
Scatterplot shows the relationship between spherical equivalent and angles. As myopia became more severe, angle α, angle β and angle α+angle β were decreased (r2=0.234, p<0.001; r2=0.282, p<0.001; r2=0.338, p<0.001 respectively). But, there was no significant difference between spherical equivalent and tilt ratio (r2=0.001, p=0.286).
Table 1.
Characteristics of study groups
| Group A (n=39) | Group B (n=50) | Group C (n=38) | p-value∏ | |
|---|---|---|---|---|
| Age (years) (mean± SD*) | 31.33±9.98 | 25.36±3.86 | 26.03±3.96 | <0.001 |
| SE† (D‡) (mean± SD) | −1.24±1.25 | −4.37±0.77 | −8.86±2.09 | <0.001 |
| Angle α (°) (mean± SD) | 73.08±8.16 | 63.02±11.87 | 57.72±10.84 | <0.001 |
| Angle β (°) (mean± SD) | 71.52±11.95 | 61.71±9.04 | 55.71±7.31 | <0.001 |
| Angle α+Angle β (°) | 144.53±16.93 | 124.73±17.00 | 113.43±15.41 | <0.001 |
| (mean± SD) | ||||
| Tilt ratio (mean± SD) | 0.90±0.06 | 0.87±0.06 | 0.86±0.09 | 0.065 |
| Mean RNFL§ thickness (μm) | 107.79±8.92 | 103.46±11.88 | 95.94±11.24 | <0.001 |
Table 2.
Characteristics of study groups excluding subjects with severe disc tilt
| Group A (n=30) | Group B (n=35) | Group C (n=23) | p-value∏ | |
|---|---|---|---|---|
| SE* (D†) (mean± SD‡) | −0.90±1.10 | −4.42±0.83 | −9.41±2.48 | <0.001 |
| Angle α (°) (mean± SD) | 74.01±8.51 | 65.92±10.53 | 58.25±11.56 | <0.001 |
| Angle β (°) (mean± SD) | 72.35±9.36 | 62.24±8.84 | 53.65±7.51 | <0.001 |
| Angle α+Angle β (°) | 146.27±15.10 | 128.17±16.48 | 111.90±17.27 | <0.001 |
| (mean± SD) | ||||
| Tilt ratio (mean± SD) | 0.93±0.03 | 0.91±0.03 | 0.92±0.03 | 0.102 |
| Mean RNFL§ thickness (μm) | 107.16±8.59 | 103.45±8.81 | 97.52±10.56 | 0.001 |
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