Effect of pupil dilation on retinal nerve fibre layer thickness measurements and their repeatability with Cirrus HD-OCT.
OBJECTIVE
To assess whether pupil dilation influences retinal nerve fibre layer (RNFL) thickness measurements provided by spectral-domain optical coherence tomography (SD-OCT) in healthy individuals.


METHODS
In this observational case series, carried out in a private clinical practice, 32 eyes of 32 participants were investigated. Using Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA, USA) three individual 200 × 200 cube optic disc scans were obtained before and after pupil dilation. The RNFL thickness was the outcome measure. Coefficient of variation (COV) and test-retest variability were calculated.


RESULTS
Pupil size did not influence RNFL thickness measurements: mean values did not change in any sector (except the 9 o'clock hour) after dilation. Excellent repeatability was achieved both before and after mydriasis. In the former condition, COV ranged between 1.37% (for average RNFL) and 4.46% (for clock hour 2 RNFL) and test-retest variability between 2.17 (for temporal quadrant RNFL) and 9.18 microm (for clock hour 6 RNFL). In the latter condition, COV ranged between 1.36% (for average RNFL) and 4.48% (for clock hour 2 RNFL) and test-retest variability between 2.41 (for average RNFL) and 9.29 microm (for clock hour 6 RNFL). The repeatability was higher than that previously reported for time-domain OCT.


CONCLUSIONS
In eyes with clear media highly repeatable measurements of the RNFL thickness can be obtained by SD-OCT both before and after mydriasis.
Savini
G
G
GB Bietti Eye Foundation - IRCCS, Rome, Italy. giacomo.savini@alice.it
Carbonelli
M
M
Parisi
V
V
Barboni
P
P
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009184:Mydriatics / Q000008:administration & dosage; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*
D009184:Mydriatics