Glaucoma is the leading cause of irreversible blindness in the world. Clinically measured elevated intraocular pressure (IOP) is used for glaucoma screening/diagnosis. In contrast to single-point measurements in clinics, IOP-time profiles contain information related to the aqueous humour dynamics of the eye. Patients with normal-tension glaucoma (NTG) often remain hidden due to their normal IOP levels (<21mmHg). Aqueous humour dynamics of glaucomatous eyes are different from healthy eyes due to their impaired aqueous outflow facility. Contact lens sensors (CLS) offer solutions to measure JOP-time profiles. The technology may allow diagnosis of NTG eyes by aqueous humour dynamics assessment.

Contact lens sensors with numerous technologies are reported in the literature. The intermittent measurements of clinical-ready CLSs hamper the ability to assess aqueous humour dynamics. Sensors based on parallel inductor-capacitor resonators offer steady wireless measurements with a high data rate while having compact, flexible, and safe designs. However, ocular permittivity variations...[ Read more ]

Glaucoma is the leading cause of irreversible blindness in the world. Clinically measured elevated intraocular pressure (IOP) is used for glaucoma screening/diagnosis. In contrast to single-point measurements in clinics, IOP-time profiles contain information related to the aqueous humour dynamics of the eye. Patients with normal-tension glaucoma (NTG) often remain hidden due to their normal IOP levels (<21mmHg). Aqueous humour dynamics of glaucomatous eyes are different from healthy eyes due to their impaired aqueous outflow facility. Contact lens sensors (CLS) offer solutions to measure JOP-time profiles. The technology may allow diagnosis of NTG eyes by aqueous humour dynamics assessment.

Contact lens sensors with numerous technologies are reported in the literature. The intermittent measurements of clinical-ready CLSs hamper the ability to assess aqueous humour dynamics. Sensors based on parallel inductor-capacitor resonators offer steady wireless measurements with a high data rate while having compact, flexible, and safe designs. However, ocular permittivity variations and low sensitivity cause unacceptable errors. The novel dualresonator CLS design offers measurements with errors less than ±3mmHg in varying permittivity on a silicone model eye. The conceptual design was optimized for human applications by adopting concentric resonators with increased IOP sensitivity (30kHz/mmHg), a high measurement rate of 1-2Hz, and excellent linearity (R²>0.99). The functionality of the device was validated on porcine eyes and human eyes.

A clinical study assessed the diagnostic utility of the system. The study involved sixty-five eyes comprising healthy (n=40), primary open-angle glaucoma (POAG) (n=16), and NTG (n=9). CLS data, which was collected during body postural changes, was fitted with a mathematical model to characterize the rates and magnitudes of the transients. CLS parameters along with the tonometer measurements were used to train machine learning algorithms. Results showed that the combination of CLS parameters and tonometer measurements offered greater sensitivity compared to using only tonometer measurements. POAG classification sensitivity increased from 62.5% to 75.0%. Models that used combined features classified NTG eyes with 77.8% sensitivity, where none of the NTG eyes was identified using only tonometer measurements. The methodology and results shed light on a novel dynamic method for screening NTG subjects from healthy ones.