Thomas H. Williamson’s research while affiliated with University of St. Thomas - Minnesota and other places

The surgeon should carefully consider certain principles when creating an incision. Wounds can be created in relatively stiff tissues or in relatively soft and malleable tissues: different principles may apply.

Complex machinery is used in ophthalmic surgery. The commonest machines in use are for phaco-emulsification and pars plana vitrectomy. They consist of a computer, pumps and instrument devices in the body of the machine and foot pedals to control the functions. In the case of phaco-emulsification the devices include an ultrasonic transducer, and piezo electric crystals that turn electronic signals into mechanical energy. In vitrectomy the devices include guillotine cutters driven by electronic motors or by compressed gas (Fig. 6.1).

Ophthalmologists deal with solid tissues such as cornea, sclera, retina, choroid, iris, crystalline lens, nerve, muscle, fat and bone and also with fluids such as aqueous humour, and blood. Solid and liquid materials have inherent physical properties related to their components like elasticity, viscosity and density. Such properties determine the materials’ interaction and behaviour. Computation of the extent of displacement, deformation and strain caused by shear, compressive, or tensile forces on materials of inherent properties and simple dimensions like squares or circles can be achieved through simple mathematical computations. The computation, however, becomes complicated when the dimensions as well as the properties of the material are more complex. Therefore for complex problems, the science of finite element analysis is used. Finite element analysis exploits material properties and dimensions to solve complex problems in the universe using mathematical approaches [1]. Finite element analysis divides complex dimensions into smaller squares, triangles or hexagons to build finite element models that could be analysed using numerical methods. Finite element analysis also allows detailed visualisation of where the structure bends or twists, and indicates the distribution of stresses and displacements. In ophthalmology, this science has helped in the provision of mathematical solutions to surgical and biological problems and to predict the optimum surgical manoeuvres to achieve certain goals [2]. In this section we will describe the basics of finite element method and its applications in ophthalmology.

When considering the eye for surgical purposes it is useful to divide the eye into surgical compartments, for example a membrane made up of the lens zonules, the lens and the lens capsule effectively divides the eye into an anterior and posterior compartments. This compartmentalization affects how to the eye will respond during operations. A common situation is an anterior wound and surgical manipulation in the anterior segment. Insertion of fluid into the anterior chamber causes egress of fluid from the wound or posterior movement of the lens diaphragm. If the flow of fluid is balanced inflow and outflow, the posterior segment remains unaffected and stable. Indentation of the wall of the anterior chamber is compensated by flow of fluid out of the wound and the posterior segment is unaffected. In contrast, pressure on the posterior segment by indentation may cause movement of the membrane towards the anterior segment, if a wound exists in the anterior segment, and then both compartments are affected (Figs. 5.1, 5.2, 5.3, 5.4 and 5.5).

This book instructs postgraduate trainees in ophthalmology on the basic methodology required to perform intraocular surgery. The text is written clearly and concisely, investigating basic surgical skills for the eye to facilitate the training process. The subject material of each chapter has been carefully chosen to explain separate conceptual areas in surgery to allow easy understanding and rapid attainment of knowledge. The concepts can be transferred from one surgical method to another, giving the reader the flexibility to adapt to new methods quickly. Intraocular Surgery - A Basic Surgical Guide provides various insights to allow the development of a thoughtful and considered approach to surgery. It encourages the reader to more intelligently scrutinize which surgical methods to apply, and to utilize the most effective procedures in clinical practice. After reading this book, the reader will be well-equipped to perform the simple steps of surgery, improving the overall quality of surgery.