Aims: To examine the effect of pupillary dilation on the reliability of retinal nerve fibre layer (RNFL) and optic nerve head (ONH) assessments using Stratus OCT in a glaucoma clinic.
Methods: Observational study involving 38 patients who attended a glaucoma clinic. The 'fast optic disc' and 'fast RNFL thickness' programmes on Stratus OCT were used to measure the RNFL thickness and ONH cup to disc ratio (CDR). Two scans were performed before dilation and 2 after dilation with tropicamide 1% drops. The mean values and reproducibility before and after dilation were compared, as was the quality of scans as indicated by the 'signal strength' score.
Results: In 9 patients (23.7%) no images were obtained undilated but after 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 judged by the signal strength score, was higher dilated than undilated for both RNFL thickness (p=0.011) and ONH CDR (p=0.007). The reproducibility was higher with dilated scans for RNFL thickness but we found no difference for ONH CDR. There were significant differences between the dilated and undilated examinations for 3 of the 5 RNFL thickness variables and 2 of the 3 ONH CDR categories.
Conclusions: In almost a quarter of patients, acquiring high quality OCT images was not possible without pupillary dilation. The dilated scans were more reproducible and of higher quality than the undilated scans. In addition the two methods of examination do not appear to be interchangeable, suggesting that follow up examinations should be performed with the pupil in the same condition as baseline. In view of these findings we recommend pupillary dilation prior to glaucoma assessments using Stratus OCT.
- ocular hypertension
- optical coherence tomography