student research day - Case Western Reserve University School of ...

SALIM-TAMUZ ABBOUD
Reproducibility of Serial Optical Coherence Tomography
Without Pharmacologic Pupillary Dilatation
Background:
Salim Abboud
Department of Neurology, The Cleveland Clinic, Mellen Center
Optical Coherence Tomography (OCT) is a technique proposed for longitudinal monitoring of multiple sclerosis,
and as an outcome measure in clinical trials. However, little is known about the precision of serial
measurements when implemented without the use of pharmacologic pupillary dilatation (PPD). Quantification of
the variability of serial measurements is necessary for sample size calculations in planning clinical trials.
Methods:
Peripapillary retinal nerve fiber layer thickness (RNFLT) and macular volume (MV) were serially measured in ten
consecutive healthy volunteers (20 eyes) using the Zeiss Stratus OCT system by ―Fast RNFL‖ and ―Fast macular
thickness‖ scan protocols without PPD. In each subject, two serial measurements were obtained at least one
week apart by a single operator. A third set of measurements was acquired using the ―repeat‖ scan registration
function to evaluate its reproducibility compared to serial independent measurements. Only signal strengths of
6 and above were accepted for each scan. The relationship between signal strength and reproducibility was
evaluated.
Results:
Mean RNFLT in the group was 96.65uM. Mean macular volume was 6.81mm3. Coefficients of variation (COV) for
independent serial measures was 2.86% for RNFLT and 1.90% for MV. COV for RNFLT and MV using the repeat
function were 3.14% and 1.16%, respectively. Median signal strength for RNFLT was 8 (range 6.5-10), and for
MV was 9 (range 6.5-10). The correlation between OCT signal strength and individual COV for serial
independent measure of RNFL approached significance (r=-.41, p=0.07).
Conclusions:
Serial measurements of RNFL and MV are sufficiently precise to employ as outcome measures in clinical trials
when implemented without PPD. Despite a trend for higher signal strengths to provide more precise data, signal
strengths greater than 6 are easily achievable and highly precise. Reproducibility may be lower in patients with
MS who potentially have impairment of visual acuity and ocular motility.
Supported by the Crile Fellowship
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