**7. 3D Models for training and surgery**

#### **7.1. Glaucoma**

device as thin as a contact lens is inserted into the cornea to reshape the front surface of the eye in order to improve vision. Corneal inlays are used to improve near vision and reduce the need for reading glasses. This device can be combined with LASIK for nearsightedness,

This procedure is less invasive than phakic IOL (intraocular lenses placed deeper in the eye). So, with the corneal inlays for vision correction, eye surgeons may sometimes be able to avoid complications associated with procedures, such as LASIK and PRK, because no corneal tissue is removed. The Kamra Corneal Inlay, previously called ACI 7000, for presbyopia is now in clinical trials. The device in inserted in a thin flap in the center of the cornea. The flap is then

Its innovation holds a promise to replace reading glasses with good near vision in the near future. The characteristics of Kamra are described as follows: 3.8 millimeters in diameter, 10 microns thick, made of an opaque biocompatible polymer (Kynar), and a thermoplastic

Corneal inlays and onlays are also called keratophakia. They are implants placed in the corneal stroma for the correction of presbyopia. The procedure is done under topical anesthesia and the implant is done monocularly in the non-dominant eye as a stromal pocket or under the

Other innovations for these techniques have been developed for researchers in Mexico, who are working on Raindrop near Vision Inlay (ReVision Optics) with some variation on diame‐

This inlay is placed in the cornea under a LASIK-style flap. When in position, the inlay changes the curvature of the cornea so the front of the eye acts much like a multifocal contact lens. The other alternative is the Flexivue Microlens (Presbia Cooperatief U.A., Amsterdam), which uses a laser and creates a tiny pocket just below the eye's surface. Currently, it requires developing the instrument to insert the microlens in the pocket that is sealed to hold the lens, and a hydrophilic polymer is irrigated during surgery with a highly moisturizing substance. The synthetic intraocular lens replaces the natural lens during cataract surgery. Its characteristics

are as follows: 3 mm in diameter and 20 microns thick at the edges [11].

replaced over the inlay to hold it in place in a process of 15 minutes [10].

flaps created by the microkeratome or by the femtosecond laser. See Figure 6.

material that softens in heat and hardens in cooler conditions.

farsightedness, and/or astigmatism.

10 Advances in Eye Surgery

**Figure 6.** Position of the corneal onlay implants.

ters, thickness, and biomaterials.

Some helpful preoperative aids recently included for prior surgery are the 3D models. These must be used to investigate the pressure drop on the localization of the main resistance to aqueous egress during iridectomy or trabeculectomy surgery. Some of these are the modeling of the eye drainage using the computational fluid dynamics (CFD) and the eye drainage system devices (GDD). To provide a 3D CFD prototype of the eye, the basis is the anatomy of a real human eye. Some models are based on stacks of microphotographs from human eye slides from which digital processing of the images of the eye structure and 3D reconstruction of the model are performed. The simulations of the distribution of pressure and the flow velocity in the model of a healthy eye bring results comparable to physiology references. Mimicking glaucoma conditions, most likely the real eye, led to an increase of the IOP from normal range, which went down to lower values after a filtering procedure. With this, a computer assisted design (CAD) model of the device is inserted in the 3D eye through the DC and the trabecular meshwork of the anterior chamber angle, parallel to the plane of the iris [12].

#### **7.2. Cataract surgery**

A simulation, very similar to the real environment, has been implemented, so the training for the surgeon is more secure. It is also in real-time as a virtual simulator with a control position tracking in a stereoscopic display mounted on a head, with a video, audio, and haptic interface in virtual reality. A real environment has been simulated that is created electronically in a controlled and protected environment where the surgeon can learn, practice, and improve their skills for surgery in a safe environment [13].

SensAble Phantom Omni T.M is equipped with a device that controls virtual surgical instru‐ ments and feeds the skills of the surgeon, allowing six degrees of freedom tracking, three of which are important in human-machine interface for simulation. A haptic interface is designed to identify the types of surgical operations, such as cutting, grasping, pushing, emulsion, and calculated reaction force, and allows modeling the deformation of the mesh fabric, such as an eye model. The cyanoacrylate polymerizes as soon as it touches something like water and aqueous or saline solution. Fibrin glue is also another sealant that is also used for pterygium with conjunctival auto-grafts and secures amniotic membrane tissue in pterygium surgery. Sealants made of polyethylene glycol hydrogel are used for sealing corneal incisions and implantation in the IOL [14].
