Assessment of corneal dynamics with high-speed swept source Optical Coherence Tomography combined with an air puff system

Karol Karnowski,Bartlomiej J Kaluzny,Andrzej Kowalczyk,David Alonso-Caneiro,Maciej Wojtkowski

doi:10.1364/oe.19.014188

Abstract

We present a novel method and instrument for in vivo imaging and measurement of the human corneal dynamics during an air puff. The instrument is based on high-speed swept source optical coherence tomography (ssOCT) combined with a custom adapted air puff chamber from a non-contact tonometer, which uses an air stream to deform the cornea in a non-invasive manner. During the short period of time that the deformation takes place, the ssOCT acquires multiple A-scans in time (M-scan) at the center of the air puff, allowing observation of the dynamics of the anterior and posterior corneal surfaces as well as the anterior lens surface. The dynamics of the measurement are driven by the biomechanical properties of the human eye as well as its intraocular pressure. Thus, the analysis of the M-scan may provide useful information about the biomechanical behavior of the anterior segment during the applanation caused by the air puff. An initial set of controlled clinical experiments are shown to comprehend the performance of the instrument and its potential applicability to further understand the eye biomechanics and intraocular pressure measurements. Limitations and possibilities of the new apparatus are discussed.

Highlights

Accurate value of intraocular pressure (IOP) is a crucial clinical parameter for the screening, diagnosis and management of glaucoma, which is a blinding condition associated with elevated IOP [1, 2]
In this study we have presented a swept source optical coherence tomography (OCT) combined with an air puff system from a non-contact tonometer
The dynamics of the anterior segment is related to the applied force, the eye intraocular pressure (IOP) and the corneal biomechanics in the eye

Summary

Introduction

Accurate value of intraocular pressure (IOP) is a crucial clinical parameter for the screening, diagnosis and management of glaucoma, which is a blinding condition associated with elevated IOP [1, 2]. A range of different tonometers are widely used in clinical ophthalmic practice to measure the IOP [2]. One of the commonly used tonometry modalities is non-contact tonometry [2], which uses an air puff to applanate the cornea. In standard non-contact tonometers, a beam of light is projected onto the corneal apex and its reflectivity is measured by a photodiode. The two points of maximum reflection (during the inward/outward movement) indicate when the cornea is flat (i.e. applanated) and can be used to calculate parameters which describe corneal biomechanical properties, such as corneal hysteresis [1] and corneal resistance factor [3]

Methods

Results

Discussion

Conclusion