Pupillary dilation a must for OCT

High quality optical coherence tomography (OCT) images cannot be obtained in a large percentage of glaucoma patients without pupillary dilation, according to a report published in the December issue of the British Journal of Ophthalmology.

Michael Smith from Torbay Hospital, Devon, UK and colleagues from the Peninsula Medical School and the University of Plymouth, Devon conducted an observational study of 38 patients attending a glaucoma clinic in order to examine the effect of pupillary dilation on the reliability of retinal nerve fibre layer (RNFL) and optic nerve head (ONH) assessments using the Stratus OCT (Carl Zeiss). The "fast optic disc" and "fast RNFL thickness" programmes on the Stratus were used to measure the RNFL thickness and ONH cup-to-disc ratio (CDR). Two scans were performed prior to dilation and two following dilation with tropicamide 1% drops.

In nine patients (23.7%) no images were obtained prior to dilation however, following dilation, examination was possible in all patients. Inability to obtain an undilated scan was associated with smaller pupil size and increasing cataract. The scan quality, as determined by the signal strength score, was higher when pupils were dilated for both RNFL thickness (p=0.011) and ONH CDR (p=0.007).

The authors of this study believe that attaining high quality OCT images is not possible without pupillary dilation, in about 25% of patients.