**9. Development on visual implants**

The LIS-CEA laboratory in France has been studying retinal implants from nanomaterials and nanodiamonds. By means of the implementation of memristors and digital technolo‐ gy, electronic devices that respond to Moore's Law (processing speed, memory capacity, and number of pixels) inspired the creation of cardiac pacemakers and created an intelli‐ gent flash. This concept was introduced by Leon O. Chua and was developed as a model of neural networks, the biomimetic model of the retina, where they expected to even send 3D signals. [17].

A project was undertaken wherein other technologies using silicon microchips as a "wafer" to create a biological and electronic device in the form of functional circuits that interact with live cells and shows a promise for the present and future cells. The construction of the small threedimensional models of the human organs can be used to treat and replace costly and timeconsuming animal studies that currently hamper the development of drugs. Furthermore, these micro-electromechanical systems (MEMS) allow testing in cell cultures without using a full tissue. A lab-on-a-chip enables the replication of tissue samples [18].

FDA approved a project of more than 15 years which comprised an interdisciplinary group of researchers. The retinal prosthesis was created: Second Sight Argus II, with funding from the National Eye Institute. It consists of a camera that captures images via implanted electrodes that stimulate cells in the retina, producing a light on the patient's visual field. This camera mounted on a pair of eyeglasses wirelessly (with 60 electrodes and hoping to increase it to 1500), has an array of microelectrodes and is mounted on a miniature camera on a pair of glasses that act as a sensitive photodiode light. The camcorder captures a portion of the visual field and transmits the information to the VPU. The device is already being used in patients with retinitis pigmentosa [19].

Traditionally, the aesthetics of the manufacturing and fitting of ocular prostheses are accept‐ able and responds efficiently in improving the patient's confidence and physical and psycho‐ logical well-being, therefore, helps to improve their social acceptance and quality of life. Recently, the introduction of visual implants is a different alternative designed to transmit electronical signals from the retina to the brain. According to the surgical technique and position, they are inserted or transplanted into the body and tend to be used as a therapeutic instrument for visual rehabilitation. The artificial stimulation to the visual pathway allows the brain to recognize the electric signal as light. New electronical materials useful for the fabrication of these devices have been developed in the recent years. An ocular prosthesis helps the patient psychologically and improves confidence, but doesn't have a visual function. Different techniques are available to fabricate a custom ocular prosthesis. In contrast, visual implants are currently being developed as an innovation to restore nerve impulses between the eyeball and the cerebral cortex, linking transdisciplinary efforts, electronic engineers, and ophthalmologists worldwide working to develop the bionic eye. The researchers are focused to allow and improve the perception of spots of light and high contrast edges by means of the devices´ stimulator as electrodes or optogenetics transducers.

See Figure 6 [20].

liver, kidney, replacement hip bones, and maxillofacial trachea has become an alternative in association with research on stem cells to regenerate tissue. Eye level attempts have been cast for 3D modeling and future impressions of the eyeball for cosmetic purposes in people requiring ocular prostheses turned what was previously artisanal towards a more precise subsequent enucleation process. This improves the aesthetic value and lowers the probability of infection that occurs in these tissues due to poor hygiene because there is no need to

This process consists of the printing, layer by layer, on a 3D printer using stable biological materials applied in tissue engineering. Very few materials, which fulfill the requirements for bioprinting as well as provide adequate properties for cell encapsulation during and after the printing process, are available. Some of the materials that are similar to the contact lens hydrogel composite or include alginate and gelatin precursors were tuned with different concentrations of hydroxyapatite (HA) and were characterized in terms of rheology, which is the swelling behavior and mechanical properties used to assess the versatility of the system

The LIS-CEA laboratory in France has been studying retinal implants from nanomaterials and nanodiamonds. By means of the implementation of memristors and digital technolo‐ gy, electronic devices that respond to Moore's Law (processing speed, memory capacity, and number of pixels) inspired the creation of cardiac pacemakers and created an intelli‐ gent flash. This concept was introduced by Leon O. Chua and was developed as a model of neural networks, the biomimetic model of the retina, where they expected to even send

A project was undertaken wherein other technologies using silicon microchips as a "wafer" to create a biological and electronic device in the form of functional circuits that interact with live cells and shows a promise for the present and future cells. The construction of the small threedimensional models of the human organs can be used to treat and replace costly and timeconsuming animal studies that currently hamper the development of drugs. Furthermore, these micro-electromechanical systems (MEMS) allow testing in cell cultures without using a

FDA approved a project of more than 15 years which comprised an interdisciplinary group of researchers. The retinal prosthesis was created: Second Sight Argus II, with funding from the National Eye Institute. It consists of a camera that captures images via implanted electrodes that stimulate cells in the retina, producing a light on the patient's visual field. This camera mounted on a pair of eyeglasses wirelessly (with 60 electrodes and hoping to increase it to 1500), has an array of microelectrodes and is mounted on a miniature camera on a pair of glasses that act as a sensitive photodiode light. The camcorder captures a portion of the visual field and transmits the information to the VPU. The device is already being used in patients

full tissue. A lab-on-a-chip enables the replication of tissue samples [18].

frequently remove it for cleaning purposes [15].

**9. Development on visual implants**

properties [16].

12 Advances in Eye Surgery

3D signals. [17].

with retinitis pigmentosa [19].

**Figure 7.** Classification of Ocular implants. Durán, P. Diaz, M, Plaza, J. Journal of ocular diseases and therapeutics. 2 N. 1, 2014.

Ocular prostheses were made and are still fabricated in inhert and non-integrable materials, such as polymethylmetacrylate (PMMA) and cryolite glass. But these days, integrable materials for anophthalmic cavities, such as a gel from cellulose produced by Zoogloea sp. porous polyethylene dental biomaterial composites and graphene among others, are imple‐ mented as materials for the heart, eye and other organs implants due to their characteristics in improving biological compatibility to be more resistant, to reduce allergies, and improve durability. The future development of the ocular prostheses is focused on the impression of digital measurements, 3D modeling software, and the digital impression of the iris [21].

Many implants are being studied around the world. Some patents and other humans have been implanted to help in visual rehabilitation. Some of these examples are divided into two categories according to design or operations principles, some use an external camera and image processing drive implanted electrodes. Another example is the use of 1500 small units in microphotodiode arrays (MPA by Retina Implant AG) and Stanford retinal prosthesis. Some required external energy to drive the stimulators, while others are wireless. The Stanford array projects a high intensity infrared image on the implanted photocells and generates a sufficient current to excite the secondary neurons. In addition, the classification must be made according to the implant site e.g., in the inner retinal (epiretinal) or outer (subretinal) retinal surface; if the implant is inserted below the choroid plexus (suprachoroidal) or if the implantation take place outside the sclera (episcleral) [22, 23, 24].

Before the production of visual implants, many studies should be performed to verify the noise pattern, the extraction processing of the temporal space, monitoring to check the quality of the image, the spatial resolution, the circuit architecture, and advanced intelligent functions.

The future smart 3D image sensor architectures will most probably consist of a sensor layer at the top and various processing layers below. Each layer will be organized into locally con‐ nected cellular arrays with additional global communication/operation mechanisms. Layers will be vertically interconnected using bi-directional parallel channels implemented by through-silicon-vias (TSVs). Images at different scales and abstract information about salient points and features will be transmitted top-down across the stack, while commands will be transmitted bottom-up to support adaptation.
