# Ocular Phantom-Based Feasibility Study of an Early Diagnosis Device for Glaucoma

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{sol}= 1/σ

_{sol}

_{i}| is the absolute value of the charging of an ion;

- C
_{i}is the concentration of this ion (i) in mol/m^{3}; - U
_{i}is the ion (i) mobility in m²/s.V; - F is 1 faraday or 96,500 C/mole;
- σ is conductivity in S.m
^{−1}and ρ is resistivity in Ω.m.

- R is resistance (Ω);
- l is the height of the schematic column containing the solution (m);
- S is the surface of the schematic column containing the solution (m²);
- ρ is the resistivity of the liquid inside the column (Ω.m).

_{inf}(obtained to a theoretical infinite frequency).

_{∞}to model electrical data and characterise the eyes in the study.

- -
- C (xc, yc) (centre of the Cole–Cole circle, r: radius of the Cole–Cole circle);
- -
- Rc, Xc and Fc characteristic data of the curve bend (characteristic resistance, characteristic reactance and characteristic frequency);
- -
- Ri (modelled resistance of the intracellular area in ohms);$${R}_{i}=\frac{{R}_{e}{R}_{\infty}}{{R}_{e}-{R}_{\infty}}{R}_{i}=\frac{{R}_{e}{R}_{\infty}}{{R}_{e}-{R}_{\infty}}$$
- -
- Alpha α (phase angle in degrees at the characteristic frequency);$$\alpha =atan\left(\frac{Xc}{Rc}\right)\xb7\frac{180}{pi}=atan\left(\frac{yc+r}{xc}\right)\xb7\frac{180}{pi}\alpha =atan\left(\frac{Xc}{Rc}\right)\ast \frac{180}{pi}=atan\left(\frac{yc+r}{xc}\right)\xb7\frac{180}{pi}$$
- -
- Tau τ (ionic relaxation time in µs);$$\tau =\left(Re+Ri\right)\ast Cm\tau =\left(Re+Ri\right)\ast Cm$$$$Cm=\frac{1}{2\pi Xc}=\frac{1}{2\pi \left(yc+r\right)}Cm=\frac{1}{2\pi Xc}=\frac{1}{2\pi \left(yc+r\right)}$$

## 2. Materials and Methods

#### 2.1. Phantoms

_{glaucoma}less than that of a healthy eye, or about ρ

_{glaucoma}= 0.465 Ω.m.

- n: number of moles in mole;
- m: sample mass in g;
- M: molar mass in g.mol
^{−1}(i.e., 58.5 g.mol^{−1}for NaCl).

#### 2.2. Materials

#### 2.3. Final Prototype Description

- An electronic part composed of a battery, Bluetooth Low Energy;
- An electronic part composed of two types of sensors: a PPG (Photo Plethysmo Graph) sensor for SpO2 (oxygen saturation of the blood microcirculation of the ophthalmic artery based on optical analysis, based on three LEDs (536, 660 and 940 nm) and two photodiodes, sample rate 100 Hz, pulse width 115.2 ms) and a bioimpedance sensor analysing both chambers of the eye (anterior and posterior);
- An electrode (lens) allowing the bioimpedance of the anterior chamber when used with the bioimpedance sensors in part 2;
- A system allowing the temporal electrodes to be positioned;
- A user interface, under development, to be finalised with the clinical data.

#### 2.4. The Algorithms

^{2}π

^{2}/3, inducing s = 1.

## 3. Results

#### 3.1. Repeatability of the Phantom Measuring Chain

#### 3.2. Inter-Lens Variability

#### 3.3. Raw Data

#### 3.4. Detection of the Presence of Glaucoma by the System

## 4. Discussion

## 5. Conclusions

## 6. Patents

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Goniogram 3D inner eye aqueous circuitry.

**A**ciliary process production.

**B**trabecular meshwork resorption impaired in hypertensive glaucoma patients and normal in normal intraocular pressure (IOP) glaucoma patients. 0 to IV: filtration corneoscleral angle degrees.

**Figure 2.**Sensitivity in deep layers according to the distance and the dimensions of the electrodes [10].

**Figure 4.**Picture of one of the phantoms representing a healthy eye (

**a**) and the associated lens (

**b**).

**Figure 5.**Diagram of an Impedance Eye Recording (IER) Lens injected in Styrene-Methyl Methacrylate (SMMA) with thin gold layer electrodes.

**Table 1.**Characteristics of the resistivities of the different components of the eye [1].

ρHealthy (Ω.m) | |
---|---|

Saline Solution (NaCl 9g.l^{−1}) | 0.625 |

Aqueous Humour | 0.60–0.67 |

Glass Humour | 0.63–0.66 |

Cornea | 0.39–0.48 |

Healthy Eye (Yellow Eye) | Glaucomatous Eye (Red Eye) | |
---|---|---|

Composition | 4 g/L Agarose 1l Demineralised Water 9 g/L NaCl | 4 g/L Agarose 1l Demineralised Water 10 g/L NaCl |

“Glaucoma Phantom” | G1 | G2 | G3 | G4 | G5 | G6 | G7 | G8 |

Zr (ohm) | 149.51 | 177.70 | 147.58 | 162.25 | 150.09 | 158.42 | 162.58 | 181.54 |

Total Eye Water (mL) | 3.01 | 3.46 | 3.04 | 2.98 | 3.00 | 2.96 | 2.91 | 2.65 |

“Healthy Phantom” | S1 | S2 | S3 | S4 | S5 | S6 | S7 | S8 |

Zr (ohm) | 196.53 | 223.31 | 169.16 | 222.63 | 217.71 | 245.11 | 230.84 | 183.20 |

Total Eye Water (mL) | 2.52 | 2.30 | 2.81 | 2.37 | 2.46 | 2.24 | 2.30 | 2.68 |

Healthy Phantoms | Glaucoma Phantoms | Mann–Whitney Tests | |
---|---|---|---|

Average Zr ± SD (Ohms) | 211.9 ± 36.9 | 160.9 ± 24.3 | p < 0.01 |

Average Difference ± SD (Ohms, %) | 51.0 − 24.1% (**) | ||

Average Vt ± SD (ml) | 2.45 ± 0.28 | 3.02 ± 0.35 | p < 0.001 |

Average Difference ± SD (ml, %) | 0.57 − 22.9 (***) |

Phantom | Glaucoma Risk Score % |
---|---|

G1 | 78.8 |

G2 | 83.4 |

G7 | 96 |

G8 | 100 |

S2 | 26.5 |

S3 | 0 |

S7 | 0 |

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**MDPI and ACS Style**

Moreno, M.-V.; Houriet, C.; Grounauer, P.-A. Ocular Phantom-Based Feasibility Study of an Early Diagnosis Device for Glaucoma. *Sensors* **2021**, *21*, 579.
https://doi.org/10.3390/s21020579

**AMA Style**

Moreno M-V, Houriet C, Grounauer P-A. Ocular Phantom-Based Feasibility Study of an Early Diagnosis Device for Glaucoma. *Sensors*. 2021; 21(2):579.
https://doi.org/10.3390/s21020579

**Chicago/Turabian Style**

Moreno, Marie-Valérie, Cloé Houriet, and Pierre-Alain Grounauer. 2021. "Ocular Phantom-Based Feasibility Study of an Early Diagnosis Device for Glaucoma" *Sensors* 21, no. 2: 579.
https://doi.org/10.3390/s21020579