LASIK flap measurements

This study compares the use of spectral domain and time domain OCT in measuring flap thickness after LASIK laser eye surgery. The spectral domain OCT appears more consistent and accurate.  This is what we have chosen to use at Bowen Eye Clinic.

Laser in situ keratomileusis (LASIK) flap measurements: Comparison between observers and between spectral-domain and time-domain anterior segment optical coherence tomography.

Journal Cataract & Refractive Surgery. March 2011, Volume 37, Number 3, Page 544-51. 

Reece C Hall FRANZCO, et al.

PURPOSE:

To evaluate the between-observer (interobserver) and between-instrument (intraobserver) variability in flap thickness measurements after laser in situ keratomileusis (LASIK) using spectral-domain and time-domain anterior segment optical coherence tomography (AS-OCT).

DESIGN:

Evaluation of diagnostic test or technology.

METHODS:

Two independent masked observers measured flap thickness 1 month after LASIK using spectral-domain (RTVue) or time-domain (Visante) AS-OCT. The measurements were taken at central (0.0 mm), -1.5 mm, and +1.5 mm locations. Measurements were repeated to assess between-instrument variability.

RESULTS:

There was no statistically significant difference in mean flap thickness between the 2 observers at -1.5 mm, 0.0 mm, and +1.5 mm on spectral-domain AS-OCT and at -1.5 mm and +1.5 mm on time-domain AS-OCT (P < .01). There was a statistically significant difference between the 2 observers in the central (0.0 mm) values on time-domain AS-OCT (P=.0008). There was stronger interobserver correlation for spectral-domain AS-OCT at -1.5 mm (r = 0.82), 0.0 mm (r = 0.88), and +1.5 mm (r = 0.88) than for time-domain AS-OCT (r = 0.73, r = 0.62, and r = 0.79, respectively). There was no statistically significant difference in between-instrument measurements. There was stronger between-instrument correlation with spectral-domain AS-OCT than with time-domain AS-OCT at all locations. The mean standard deviation (measure of instrument repeatability) for spectral-domain AS-OCT was 4.19 μm.

CONCLUSION:

Spectral-domain AS-OCT had closer agreement in between-observer and between-instrument measurements than time-domain AS-OCT and provided more consistent measurements of post-LASIK flap thickness.

Research paper presented at European Society of Cataract and Refractive Surgeons meeting Barcelona Sept 2009.

Journal Cataract & Refractive Surgery