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G. Hollo, A. Katsanos, P. Kothy, A. Kerek, I. Suveges; Avoidance of LASIK-induced Virtual Thinning in Polarimetric Measurement of the Retinal Nerve Fibre Layer (RNFL) by using Individualised Corneal Polarisation Compensation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3352.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate whether the use of individualised corneal polarisation compensation in scanning laser polarimetry (SLP-I) can avoid the LASIK-induced, virtual changes of the polarimetric RNFLT values observed with the fixed angle compensation (SLP-F). Methods: Both SLP-F and SLP-I (GDx-Access, software version 5.0) were performed on 15 consecutive healthy subjects with no eye disease who underwent LASIK for ametropia correction. RNFLT values for one randomly selected eye per subject measured before the surgery, then on day 1 and day 6 after LASIK were analysed. Results: Superior maximum, inferior maximum, normalised superior area and normalised inferior area (SLP parameters representing the RNFLT at the superior and inferior poles of the optic nerve head) remained unchanged with SLP-I (ANOVA, p>0.05) but decreased (superior maximum, normalised superior area, Scheffe test, p<0.05) or tended to decrease (inferior maximum) after LASIK, when measured using SLP-F. In contrast certain other parameters, namely superior ratio and inferior ratio (representing the ratios between the superior or the inferior sector and the temporal sector), maximal modulation, and ellipse modulation decreased with SLP-I (Scheffe test, p<0.05), but remained stable with SLP-F (ANOVA, p>0.05) after LASIK. Superior to nasal ratio, symmetry of the superior and inferior RNFLT as well as "The Number" remained unchanged with both types of corneal compensation (ANOVA, p>0.05). With SLP-I the parameter ellipse average thickness increased after LASIK (Scheffe test, p = 0.021). No value altered between day 1 and day 6 after LASIK, for either method. Conclusions: The results suggest that the use of individualised corneal polarisation compensation avoids the virtual decrease of the polarimetric RNFLT. However the post-LASIK decrease of the ratios using the temporal RNFLT in the denominator in SLP-I needs further investigation.
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