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Corneal Confocal Microscopy: A Novel Non-invasive Technique to Quantify Small Fibre Pathology in Peripheral Neuropathies
Published on: January 3, 2011
The effect of pupil dilation on scanning laser polarimetry with variable corneal compensation
Amjad Horani1, Shahar Frenkel, Eytan Z Blumenthal
1Department of Ophthalmology, Hebrew University-Hadassah Medical Center, Jerusalem, Israel.
Background And Objective:
The feasibility and reproducibility of scanning laser polarimetry performed through dilated pupils rather than through non-dilated pupils was tested.
Patients And Methods:
One eye each of 36 subjects (12 normal, 12 suspected glaucoma, and 12 glaucoma) was scanned using a single GDx unit with variable corneal compensator (GDx-VCC; Laser Diagnostic Technologies, Inc., San Diego, CA). Two scans prior to and two scans after dilation were performed on each study eye, resetting the cornea compensation prior to each scan. The dilated eye was viewed off-center, such that the whitish focusing patch was projected on the 9-o'clock peripheral iris. After adequate anteroposterior focus, the pupil was centered and a scan was acquired. Each of 5 GDx parameters was evaluated comparing the pre-dilation and post-dilation scans.
Results:
No statistically significant difference was found between pre-dilation and post-dilation measurements. There was a high pre-dilation to post-dilation correlation of 98%, 98%, 98%, 93%, and 95% for nerve fiber indicator, TSNIT average, TSNIT standard deviation, superior average, and inferior average, respectively. Less than 5% of the measurement variability was attributed to changes in pupil size (R2 ranging from 0.024 to 0.047). Stratifying the data by diagnostic groups yielded similar results.
Conclusions:
Pharmacologic mydriasis was not found to influence the retinal nerve fiber layer measurements acquired using the GDx-VCC. Results were comparable to scans achieved in the same eyes prior to dilation.
