Changes After a Month Following Micropulse Cyclophotocoagulation in Normal Porcine Eyes

Abstract Purpose To assess corneal stiffening of standard (S-CXL) and accelerated (A-CXL) cross-linking protocols by dynamic corneal response parameters and corneal bending stiffness (Kc[mean/linear]) derived from Corvis (CVS) Scheimpflug-based tonometry. These investigations were validated by corneal tensile stiffness (K[ts]), derived from stress-strain extensometry in ex vivo porcine eyes. Methods Seventy-two fresh-enucleated and de-epithelized porcine eyes were soaked in 0.1% riboflavin solution including 10% dextran for 10 min. The eyes were separated into four groups: controls (n = 18), S-CXL (intensity in mW/cm2*time in min; 3*30) (n = 18), A-CXL (9*10) (n = 18), and A-CXL (18*5) (n = 18), respectively. CXL was performed using CCL Vario. CVS measurements were performed on all eyes. Subsequently, corneal strips were extracted by a double-bladed scalpel and used for stress-strain measurements. K[ts] was calculated from a force-displacement curve. Mean corneal stiffness (Kc[mean]) and constant corneal stiffness (Kc[linear]) were calculated from raw CVS data. Results In CVS, biomechanical effects of cross-linking were shown to have a significantly decreased deflection amplitude as well as integrated radius, an increased IOP, and SP A1 (P < 0.05). Kc[mean]/Kc[linear] were significantly increased after CXL (P < 0.05). In the range from 2 to 6% strain, K[ts] was significantly higher in S-CXL (3*30) compared to A-CXL (9*10), A-CXL (18*5), and controls (P < 0.05). At 8% to 10% strain, all protocols induced a higher stiffness than controls (P < 0.05). Conclusion Several CVS parameters and Kc[mean] as well as Kc[linear] verify corneal stiffening effect after CXL on porcine eyes. S-CXL seems to have a higher tendency of stiffening than A-CXL protocols have, which was demonstrated by Scheimpflug-based tonometry and stress-strain extensometry.

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Impact of freeze-thaw cytoablation on aqueous outflow patterns in ex vivo anterior chamber perfusion cultures and whole eyes

F1000Research ◽

10.12688/f1000research.53572.1 ◽

2021 ◽

Vol 10 ◽

pp. 525

Author(s):

Raoul Verma-Fuehring ◽

Mohamad Dakroub ◽

Alicja Strzalkowska ◽

Piotr Strzalkowski ◽

Hong Han ◽

...

Keyword(s):

Trabecular Meshwork ◽

Structural Changes ◽

Ex Vivo ◽

Anterior Segment ◽

Large Change ◽

Invasive Technique ◽

Freeze Thaw ◽

Before And After ◽

Human Eyes ◽

Porcine Eyes

Background: Porcine eyes have been widely used as ex vivo models in glaucoma research, as they share similar features with human eyes. Freeze-thawing is a non-invasive technique that has been used to obliterate living cells in anterior segment ex vivo cultures, to prepare them for further research such as cellular repopulation. This technique has previously been shown to reduce the intraocular pressure (IOP) in porcine eyes. The aim of this study was to investigate whether freeze-thaw cytoablation causes corresponding canalogram outflow changes in perfused anterior segment cultures (AFT) and whole porcine eyes (WFT). We hypothesized that the known IOP drop in AFT after trabecular meshwork ablation by freeze-thaw would be accompanied by a similarly large change in the distal outflow pattern. Methods: Two-dye (fluorescein and Texas red) reperfusion canalograms were used to compare the outflow time before and after two -80°C cycles of freeze-thaw. We assigned 28 freshly enucleated porcine eyes to four groups: perfused anterior segment dye controls (ACO, n = 6), perfused whole eye dye controls (WCO, n = 6), freeze-thaw treated anterior segment cultures (AFT, n = 10), and freeze-thaw treated whole eyes (WFT, n = 6). Results: In control groups ACO and WCO, the two different dyes had similar filling times. In AFT, the outflow pattern and filling times were unchanged. In WFT, the temporal superior quadrant filled more slowly (p = 0.042) while all others remained unchanged. The qualitative appearance of distal outflow spaces was altered only in some eyes. Conclusions: Freeze-thaw cytoablation caused neither loss nor leakage of distal outflow structures. Surprisingly, the loss of an intact trabecular meshwork over the entire circumference did not result in a general acceleration of quadrant outflow times. The results validate freeze-thawing as a method to generate an extracellular matrix without major structural changes.

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Intraocular Pressure Estimation Method Based on Vibration Propagation Characteristics According to Structure Contact

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-3144 ◽

2021 ◽

Vol 263 (1) ◽

pp. 5552-5554

Author(s):

Kim Deukha ◽

Seongwook Jeon ◽

Won June Lee ◽

Junhong Park

Keyword(s):

Intraocular Pressure ◽

Short Term Memory ◽

Learning Algorithm ◽

Ex Vivo ◽

Estimation Method ◽

Biological Tissues ◽

Response To Treatment ◽

Deep Learning Algorithm ◽

Cross Correlation Analysis ◽

Porcine Eyes

Intraocular pressure (IOP) measurement is one of the basic tests performed in ophthalmology and is known to be an important risk factor for the development and progression of glaucoma. Measurement of IOP is important for assessing response to treatment and monitoring the progression of the disease in glaucoma. In this study, we investigate a method for measuring IOP using the characteristics of vibration propagation generated when the structure is in contact with the eyeball. The response was measured using an accelerometer and a force sensitive resistor to determine the correlation between the IOP. Experiment was performed using ex-vivo porcine eyes. To control the IOP, a needle of the infusion line connected with the water bottle was inserted into the porcine eyes through the limbus. A cross correlation analysis between the accelerometer and the force sensitive resistor was performed to derive a vibration factor that indicate the change in IOP. In order to analyze the degree of influence of biological tissues such as the eyelid, silicon was placed between the structure and the eyeball. The Long Short-Term Memory (LSTM) deep learning algorithm was used to predict IOP based on the vibration factor.

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