Abstract
Purpose: :
The ssOCT instrument combined with air-puff system enables to measure cornea deformation and lens displacement introduced by air stream. We investigated the correlation between the deformation and diurnal variations of IOP and CCT.
Methods: :
For this study a commercial swept source laser working at 50 kHz with a 100 nm optical bandwidth is used. The axial resolution of the system is 9 um in air and the eye is illuminated with average 2.5 mW optical power. The sample arm of the system is merged with air puff chamber. The imaging beam exits chamber through the 3mm pipe. The pipe delivers air puff that deforms the cornea. System of air stream generation is synchronized with acquisition and scanners. It is possible to use 2D (preview mode) and 3D scanning protocols - images are then distorted by shadow cast by exit pipe. During main measuring protocol a M-scan is recorder. The displacement of anterior and posterior cornea surfaces and also anterior lens surface is visible. Automatic segmentation procedure detects surfaces positions during deformation. The relative displacement of anterior corneal surface, posterior corneal surface and anterior lens surface during the ~20 ms applanation/recovery process can be plotted.
Results: :
Studies are performed on 5 healthy subjects (10 eyes) during the day (between 8am and 8pm) in 100 minutes steps. For each step corneal deformation is measured with the air-puff ssOCT. Additionally IOP and blood pressure are measured with commercially available instruments. The data obtained with ssOCT system is then processed prior to achieve information about corneal and lens surface deformations as well as the corneal thickness and anterior chamber depth changes during applanation/recovery process.
Conclusions: :
A diurnal fluctuations of induced anterior segment deformations are presented. Correlation between the IOP fluctuations during the day and anterior segment changes (cornea surfaces relative displacement, displacement of anterior surface of the lens, central corneal thickness and anterior segment depth) is presented.
Keywords: imaging/image analysis: non-clinical • anterior segment • intraocular pressure