Changes in temperature inside an optomechanical model of the human eye during emulated transscleral cyclophotocoagulation

Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry

The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye model includes an artificial cornea, an intraocular lens or other lens to simulate the crystalline lens, an aperture as the pupil, and a posterior retinal surface, which may be connected to a light sensor. The interior of the eye model may be filled with a fluid to better emulate physiological conditions. The main focus of this review is the materials and physical characteristics used and the dimensional aspects of the main components including lenses, apertures, chambers, imaging sensors and filling medium. Various devices are described with their applications and technical details, which are systematically tabulated highlighting their main characteristics and applications. The models presented are detailed and discussed individually, and the features of different models are compared when applicable, highlighting strengths and limitations. In the end there is a brief discussion about the potential use of artificial eye models for industrial applications.

Computational Modeling of Ophthalmic Procedures: Computational Modeling of Ophthalmic Procedures

PURPOSE

To explore how finite-element calculations can continue to contribute to diverse problems in ophthalmology and vision science, we describe our recent work on modeling the force on the peripheral retina in intravitreal injections and how that force increases with shorter, smaller gauge needles. We also present a calculation that determines the location and stress on a retinal pigment epithelial detachment during an intravitreal injection, the possibility that stress induced by the injection can lead to a tear of the retinal pigment epithelium.

BACKGROUND

Advanced computational models can provide a critical insight into the underlying physics in many surgical procedures, which may not be intuitive.

METHODS

The simulations were implemented using COMSOL Multiphysics. We compared the monkey retinal adhesive force of 18 Pa with the results of this study to quantify the maximum retinal stress that occurs during intravitreal injections.

CONCLUSIONS

Currently used 30-gauge needles produce stress on the retina during intravitreal injections that is only slightly below the limit that can create retinal tears. As retina specialists attempt to use smaller needles, the risk of complications may increase. In addition, we find that during an intravitreal injection, the stress on the retina in a pigment epithelial detachment occurs at the edge of the detachment (found clinically), and the stress is sufficient to tear the retina. These findings may guide physicians in future clinical research. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Changes After a Month Following Micropulse Cyclophotocoagulation in Normal Porcine Eyes

Purpose

To analyze the effects on the uvea, including the pars plicata and ciliary muscle, and retina in normal porcine eyes after performing micropulse transslceral cyclophotocoagulation (MP-TSCPC) with the different energy levels, and conventional continuous wave transslceral cyclophotocoagulation.

Methods

MP-TSCPC was performed in a total of 15 eyes at the different energy levels of 60 J, 120 J, 180 J, 240 J, and 300 J, respectively. Continuous wave transslceral cyclophotocoagulation was performed in three eyes and the other three eyes were controls. The eyes were enucleated after a month following the laser treatment and the uvea and retina were analyzed using hematoxylin and eosin staining and immunohistochemistry staining.

Results

After MP-TSCPC 60 J, the expression of α-smooth muscle actin (α-SMA) and glial fibrillary acidic protein in the ciliary muscle was increased, although there was no structural change in pars plicata. After MP-TSCPC 120 J, partial destruction of the ciliary epithelium was observed in pars plicata, and the retinal thickness was increased. After MP-TSCPC 240 J and 300 J, the structural destruction of the pars plicata and ciliary muscle was observed, and the expression of α-SMA and glial fibrillary acidic protein in pars plicata and the expression of α-SMA in ciliary muscle were increased.

Conclusions

Histologic changes in the uvea and peripheral retina were different based on the energy levels of MP-TSCPC. In particular, MP-TSCPC with low energy levels mainly affected the ciliary muscle, while MP-TSCPC with high energy levels affected both the ciliary muscle and pars plicata. Our results may imply a possibility of intraocular damage with MP-TSCPC in humans.

Translational Relevance

Based on our research, it is possible to infer the possibility of intraocular damage in humans according to the different levels of energy in the clinic.

Biomimetic models of the human eye, and their applications

Replicating the functionality of the human eye has been a challenge for more than a century, creating a great wealth of biomimetic and bioinspired devices, and providing ever improving models of the eye for myriad research purposes. As improvements in microelectronics have proceeded, individual components of the eye have been replicated, and models of the optical behaviour of the eye have improved. This review explores both work developed for improving medical components, with an ultimate aim of a fully functioning prosthetic eye, and work looking at improving existing devices through biomimetic means. It is hoped that this holistic approach to the subject will aid in the cross pollination of ideas between the two research foci. The review starts by summarising the reported measurements of optical parameters of various components of the eye. It then charts the development of individual bionic components. Particular focus is put on the development of bionic and biomimetic forms of the two main adaptive components of the eye, namely the lens and the iris, and the challenges faced in modelling the light sensitive retina. Work on each of these components is thoroughly reviewed, including an overview of the principles behind the many different approaches used to mimic the functionality, and discussion of the pros and cons of each approach. This is concluded by an overview of several reported models of the complete or semi-complete eye, including details of the components used and a summary of the models' functionality. Finally, some consideration is given to the direction of travel of this field of research, and which existing approaches are likely to bring us closer to the long term goal of a fully functional analogue of the eye.