The effect of laser-assisted in situ keratomileusis on retinal nerve fiber layer measurements obtained with scanning laser polarimetry.
OBJECTIVE
Scanning laser polarimetry provides indirect measurements of retinal nerve fiber layer thickness by measuring the retardation of polarized laser light as it passes through the retinal nerve fiber layer. Laser-assisted in situ keratomileusis is a refractive technique by which corneal stromal photoablation is achieved by the structural and refractive changes induced by the excimer laser. Both techniques are becoming widely performed and there is some evidence that scanning laser polarimetry measurements are significantly changed after laser-assisted in situ keratomileusis. The authors performed a larger study to determine whether laser-assisted in situ keratomileusis induces predictable and consistent alterations in the measurement of retinal nerve fiber layer thickness.


METHODS
Retinal nerve fiber layer thickness measurements using scanning laser polarimetry were performed 1 week before and 1 week after laser-assisted in situ keratomileusis in 30 consecutive eyes (16 patients) undergoing the procedure at The Eye Institute.


RESULTS
Mean +/- SD preoperative spherical equivalent refraction was -4.66 +/- 2.40 D, mean ablation depth was 73.0 +/- 36.23 microm, and mean patient age was 40.6 +/- 8.7 years. Six of 12 retinal nerve fiber layer thickness measurements showed significant change (P < 0.05) after laser-assisted in situ keratomileusis. There was no correlation with corneal ablation depth (P > 0.05) for all parameters.


CONCLUSIONS
Laser-assisted in situ keratomileusis significantly affects retinal nerve fiber layer thickness measurements obtained by scanning laser polarimetry. Sequential images should be interpreted with caution and new postoperative baseline images should be obtained.
The Eye Institute, Sydney, Australia. troberts@theeyeinstitute.com.au
Tim V
TV
Roberts
Michael A
MA
Lawless
Christopher M
CM
Rogers
Gerard L
GL
Sutton
Yuval
Y
Domniz
D000328:Adult; D001718:Birefringence; D003315:Cornea / Q000601:surgery; D006801:Humans; D007429:Intraocular Pressure; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D007834:Lasers; D009216:Myopia / Q000601:surgery; D009412:Nerve Fibers / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis* / Q000209:etiology; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D014792:Visual Acuity; D058609:Visual Field Tests / Q000379:methods