Two-Color-Strobe-Technology(TCST)for obtaining IOP and cornea properties simultaneously

Abstract

 

Purpose

 

Two-color-strobe-technology(TCST) to record and to extract the IOP and cornea information from the cornea deformation by an air pulse is successfully demonstrated. TCST can be used as an easy-to-use home monitoring of IOP. TCST can extend beyond the in-home tonometry in the following three areas that will benefit from this research effort. 1. Obtaining True IOP without interference of the physical properties of cornea 2. Extending the cares to keratoconus and corneal ectasia 3. Obtaining dynamic corneal topography for cornea procedures

 

Methods

 

A train of light strobes, Fig 1, record the corneal deformation caused by an air puff onto a single frame of a CMOS camera. To differentiate the cornea concaving and rebounding, two colors of the light are used, blue(460nm) for recording the concaving and red(625nm)for recording the rebounding. An eye model that is made of a plastic container of BSS with a transparent silicone dome that imitates the cornea with its curvature and thickness emulating the normal eyes. Two different thickness(0.6mm and 1mm) of this silicone cornea will be used for the tests. Different tensile strength were used. Intra-chamber pressures were obtained by raising the BSS bag to specified heights above the level of the chamber. A calibrated manometer was assembled to give an absolute pressure reading.

 

Results

 

Fig2 shows the basic of TCST data and analysis. The detailed results are summarized in terms: 1.Modulus of elasticity, 2. The depth of indentation vs the IOP 3.Comparison to Goldmann tonometer(GNT)

 

Conclusions

 

We demonstrated an accuracy of ±1mm Hg and a repeatability of TCST measurement similar to the repeatability of GNT in all the pressure ranges. Our study also demonstrated the feasibility of TCST to measure IOP at an accuracy of ±1mm Hg.

 

 

Fig1 The schematics of the main components and organization of the TCST

 

 

Fig2(top) TCST dynamic cornea images obtained with an artificial cornea an eye model with four different IOP’s. The air puff came from the right with a duration of 10 msec. Fig2(bottom) illustrates an algorithm of analyzing the TCST images. The apex of the cornea was on the right side of Fig2(A) and the left side of Fig2(B). The two horizontal yellow lines in the middle of Fig2(A) were used to derive the cornea positions in Fig.2B. The x-axis is the pixel counting with conversion factor 3.3µm/pixel.

 

Keywords: 568 intraocular pressure • 479 cornea: clinical science • 680 refractive surgery: complications