Our laboratory is the only one to have developed engineering tools to map the deformations of the sclera and lamina cribrosa (induced by intraocular pressure or IOP) in the living human eye. Briefly, a 3D tracking algorithm was developed to extract 3D tissue displacements from OCT volumes captured under different loading conditions. This algorithm has a high accuracy and is robust to OCT speckle noise (the noise inherent to OCT) proven with artificial deformations (Figure A-B). Using such algorithm, we have mapped for the first time the 3D displacements and strains (a measure of deformation) of patients’ optic nerve heads (ONHs) following changes in IOP in vivo (Figure C-D).
We are hoping to use such techniques for the diagnosis of glaucoma. This is a project in collaboration with Dr Nicholas Strouthidis from Moorfields Eye Hospital.
Figure Caption. (A) An artificially-deformed volume was created from a baseline OCT volume of a patient's ONH (referred to as undeformed) with added speckle noise. (B) 3D displacements extracted using our 3D tracking algorithm (in red) were in excellent agreement with the applied displacements (in blue). A zoomed view was included to show that only subtle differences existed. (C) In vivo 3D deformation mapping of the ONH in one patient following lowering of the intraocular pressure (IOP) by glaucoma surgery. Cross-sectional contours of the ONH pre- and post-surgery are shown in black and white, respectively. (D) Axial strain in the ONH tissues of a patient's eye following a decrease in IOP from 23 to 17 mmHg. Strain values are represented where red indicates thickening of the tissues with IOP lowering. This means that in that patient compression was relieved after lowering of IOP (by up to 10% as indicated by the red region).
Compensation techniques are used to improve the detection of the lamina cribrosa.