A three dimensional finite element model of the human eye is developed to evaluate the force which will be applied over the surface of cornea during tonometry and gonioscopy tests. The standard tonometers and gonioscopy experiences deformation from 0.5mm to 3mm of the cornea is adopted during both point contact and boundary contact on the surface of the cornea. The results demonstrate the maximum force experienced by the tonometer with point contact at the center of the cornea for the maximum possible deformation of the cornea during tonometry. The study also analyzes for the force experienced by the tonometer or goniolens with boundary layer contact for the defined deformation of the cornea along the direction from cornea towards the retina.

Purpose Discover the associations of force of applanation on the eye with the plunging depth of the cornea and quantify them. The results will be utilized as the feedback parameter in the new prototype development of eye care instruments as additional force may damage the internal structure of the eye or may result in erroneous output. Method A finite element-based eye model is designed utilizing the actual dimensions of the human eye. A standardized tonometer is designed and the simulation is carried out at predetermined deformation of the cornea to find the force of applanation on the cornea during tonometry. Adding on, the influence of IOP during tonometry is analyzed for a range of plunging depths of the cornea. Results The graphical results inferred the linear relation between the force of applanation with the deformation of the cornea and the results are quantified. The resulting deformation and stress plot of FEM based simulation approach is analyzed and observations regarding deformations and stress are made. Conclusion The human eye is successfully developed and also computed force on the cornea during tonometry is validated. The inference drawn from the deformation plot and stress plot is that the junction of cornea–sclera along with cornea-tonometer periphery undergo maximum deformation and experiences the highest stress compared to other areas of the eye while during tonometry.

Tonometry, a procedure of glaucoma investigation is carried out effectively in all eye care clinics. The other testing method namely gonioscopy requires professional expertise and experience due to which optometrists/ophthalmologists avoid this test. Hence the proposed technology would let these two important glaucoma testing procedures be performed simultaneously with a common instrument "Tonogoniometry" and making detection easier, time-saving, and lowering uneasiness to the patient. Tonometry is implemented by embedding a vibration sensor on the 3-mirror goniolens. The experiment is performed on goat eyes and the data collected is statistically analyzed. The relation between the Intraocular pressure (IOP) of the eye and the sensor output is derived and is implemented in LabVIEW. During tonometry, the sensor output captured by the NI data acquisition card is fed to the LabVIEW platform which will display the evaluated IOP of the eye on the computer screen. Meanwhile, there is no obstruction to the light path through the goniolens to visualize the anterior chamber angle to perform gonioscopy. The experimental results epitomized that the rise in IOP of the eye will increase the intensity of vibration of the sensor and the sensor output will have a higher magnitude.INDEX TERMS anterior chamber angle, glaucoma, gonioscopy, IOP, LabVIEW, NI data acquisition card, tonometer, vibration sensor.

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