Effect of pupillary dilatation on glaucoma assessments using optical coherence tomography

Abstract

Aims: To examine the effect of pupillary dilatation 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 of 38 patients attending a glaucoma clinic. The ''fast optic disc'' and ''fast RNFL thickness'' programs on Stratus OCT were used to measure the RNFL thickness and ONH cup to disc ratio (CDR). Two scans were done before dilatation and two after dilatation with tropicamide 1% drops. The mean values and reproducibility before and after dilatation were compared, along with the quality of scans as indicated by the ''signal strength'' score. Results: In nine patients (23.7%) no images were obtained undilated but after dilatation 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). Reproducibility was higher with dilated scans for RNFL thickness but not for ONH CDR. There were significant differences between the dilated and undilated examinations for three of the five RNFL thickness variables and two of the three ONH CDR categories. Conclusions: Acquisition of high quality OCT images was not possible without pupillary dilatation in about 25% of the patients. The dilated scans were more reproducible and of higher quality than the undilated scans. The two methods of examination do not appear to be interchangeable, suggesting that in follow up examinations the pupil should be in the same condition as at baseline. Pupillary dilatation is recommended before glaucoma assessments using Stratus OCT.

Effect of pupil dilation on retinal nerve fibre layer thickness measurements and their repeatability with Cirrus HD-OCT

“…In a study involving 38 glaucoma patients with a mean age similar to that in our own sample, Smith et al 28 reported that in almost a quarter of cases (23.7%) it was not possible to acquire high-quality OCT images without pupil dilation and that dilated scans were more reproducible and gave different RNFL thickness mean values. A significant effect of pupil dilation was found also by Paunescu et al 29 In a previous study on a group of patients undergoing cataract surgery, our group reported that pupil dilation slightly affected RNFL thickness measurements by Stratus OCT, as RNFL thickness values were statistically higher in the 3601 average measurement and in the nasal quadrant and some differences were found in the other quadrants as well, although statistical difference was not reached.…”

“…[18][19][20][21][22] Recently, mydriasis was also induced using Stratus OCT. 20,[23][24][25] Some controversy, in fact, still exists regarding the effect of pupil dilation on RNFL thickness measurements by Stratus OCT: whereas some articles reported that the difference is little or even not statistically significant, 26,27 other studies found that measurements before and after dilation are not interchangeable. 28,29 Being able to acquire OCT scans without mydriasis would allow the operator to save time in a busy practice, would eliminate the risk of angle closure in predisposed eyes, and would not cause annoying visual disturbances in patients undergoing the examination. Moreover, it should be considered that during the follow-up it may occur that the same eye is examined sometimes with and without mydriasis.…”

Influence of pupil dilation on retinal nerve fibre layer measurements with spectral domain OCT

“…14-18 Although SD-OCT has shown better reproducibility than TD-OCT, 18,19 glaucoma discrimination has been found to be similar for TD-OCT and SD-OCT. 20 Several studies have investigated the influence of pupil dilation on RNFL measurements obtained with TD-OCT. [11][12][13]21,22 Smith et al 11 suggested that the TD-OCT requires pupil dilatation to perform the examination, as the quality of scans and the reproducibility of RNFL measurements is not satisfactory in 25% of undilated AT, average thickness; IT, inferior thickness; NT, nasal thickness; ST, superior thickness; SD-standard deviation; TT, temporal thickness; Q, quality score; H1T to H12T, thickness at 0100, 0200, 0300, 0400, 0500, 0600, 0700, 0800, 0900, 1000, 1100, and 1200 hours sectors. a Comparison between non-dilated glaucoma group vs non-dilated healthy individuals.…”

“…[8][9][10] Recently, advances in technology allowed the development of spectral-domain OCT (SD-OCT), which provides faster acquisition, better resolution, and improved visualization of retinal morphology. 8 By using the advanced technology of SD-OCT, the Cirrus HD-OCT acquires data about 70 times faster (27 000 vs 400 A-scans per second) and with better resolution (5 vs B10 mm of axial resolution in tissue) when compared to the first generation of OCT. 9,11 Furthermore, some studies have indicated that time-domain OCT requires pupil dilation for the acquisition of good quality images of the retina and RNFL. [11][12][13] Although the manufacturer of the Cirrus HD-OCT indicates that the images can be obtained without pupil dilation, there is no study in the literature investigating the effects of pupil dilation on the measurements obtained with this instrument.…”

“…8 By using the advanced technology of SD-OCT, the Cirrus HD-OCT acquires data about 70 times faster (27 000 vs 400 A-scans per second) and with better resolution (5 vs B10 mm of axial resolution in tissue) when compared to the first generation of OCT. 9,11 Furthermore, some studies have indicated that time-domain OCT requires pupil dilation for the acquisition of good quality images of the retina and RNFL. [11][12][13] Although the manufacturer of the Cirrus HD-OCT indicates that the images can be obtained without pupil dilation, there is no study in the literature investigating the effects of pupil dilation on the measurements obtained with this instrument. Even though there is evidence of the benefits of SD-OCT, factors affecting the variability of measurements should be determined before using it in clinical practice.…”