Abstract
Purpose: :
To evaluate the influence of wearing refractive contact lenses (CL) on retinal fiber layer thickness (RNFL) measurements in low and moderate myopia using SD-OCT.
Methods: :
The peripapillary RNFL of 23 normal myopic eyes (myopia range -0.5 to -10.25 dpt) was imaged with a SD-OCT (Spectralis, Heidelberg Engineering). RNFL thickness was measured with undilated pupils, at the optic disc with 16 automatically averaged consecutive concentric circular B-scans (3.4 mm diameter, 768 A-scans). Examinations were performed to have one baseline (BL) measurement without CL and two follow up (FU) units, one with CL compensating for myopia and one without CL within 24 hours. Both FUs were performed with an online tracking system to find automatically the same position of the scan circle as used at BL. RNFL thickness was averaged to 32 sectors (11.25° each) and 4 quadrants respectively.
Results: :
Mean RNFL thickness in the study population was 91.8 ±12 µm at BL, 91.8±11 at FU with CL and 92.7 ±11 at FU without CL.The Difference in RNFL between BL and FU with CL and BL and FU without CL differ in the 4 quadrants. Difference in RNFL was highest in the inferior quadrant (135.5±27.4µm), followed by the superior quadrant (103.6±29.4µm), the temporal (67.7±14.3µm) and nasal (64.8±21.1µm) quadrant. The difference between inferior/ superior and temporal/ nasal quadrants was statistically significant (p<0.001). Differences between BL and FU with CL measurements tended to be higher (4.2 ±6) than differences between BL and FU measurements without CL (3.2 ±5) and showed a trend to increase in myopia higher than -5 diopters without any statistical significance (p>0.05). RNFL thickness was not significantly correlated with the degree of myopia.
Conclusions: :
Although the use of refractive CL had no significant effect on RNFL measurements in our study group, the higher variability in higher myopia indicate that RNFL measurements might be affected by CL in these eyes. Wearing CL in low myopia seems to have little influence on RNFL measurements. Considering that the normative database for diagnostic purposes does not include values corrected for refractive error or contact lenses, measurements with SD-OCT should be performed without contact lenses.
Keywords: nerve fiber layer • myopia • contact lens