Every few decades there is a tsunami in vision care technology. In the seventies it was the intraocular implantable lenses, which freed patients who underwent cataract surgery from wearing thick glasses with various shortcomings. In the nineties we saw the advent of Lasik eye surgery which has become a household name. Now the first new wave of technology for the twenty first century has started.
The goal of this book is to help you ride this wave successfully. There is so much at stake when vision is concerned. A lot of information is available on the internet, as well as misinformation. The incorrect information creeps in as people to try to mislead Google’s algorithms. Initially, non-medical personnel and then the software starting to generate content that led to a plethora of confusing articles. It is not possible for an average person to sift through the truth from the marketing tactics. We learned that misinformation about Lasik eye surgery increased the fear of the consumers affecting overall acceptability of the procedure.
The thought of any surgical intervention induces a fear in people, particularly eye surgery. The goal of this book is to decrease the fear by simply worded explanations, which can be read and reflected upon with a peace of mind. This is more effective than a five to ten-minute medically laced jargon discussion in the doctor’s office, which is barely retained after leaving the office. This book may also inspire young surgeons to obtain the necessary knowledge needed as they themselves begin the journey to master the art and skill of PIE.
The author brings three decades of experience of interacting with patients, performing surgeries and, most importantly, listening to patients’ concerns, desires, and feedback after the procedure. This forms the basis of this easy to understand, scientific, educational tool so that readers may make an informed and rational decision regarding their eyes.
This book on PIE, or Presbyopia Implants in Eye, is directed at people above 45 years of age, who desire to decrease or eliminate their dependency on glasses and contact lenses. Many people aspiring to have Lasik eye surgery may not know that there is a better procedure available, known as PIE. This book explains the advantage of PIE over Lasik. PIE is also helpful for people who are currently suffering from cataracts.
It will explain the superiority of PIE over cataract eye surgery. The book will benefit younger people who are not candidates for Lasik eye surgery or have developed early onset cataracts. Furthermore, it will be a useful guide even if one has had Lasik, Radial Keratotomy (RK), or any other eye surgery.
Most importantly, this book will explain the different classes of PIE, guide you through the process of selecting the best PI for your eye and choosing a professional PIE surgeon. Finally, the book will discuss the risks and how to prevent complications by steps taken before, during and after the procedure. This book will also introduce and delve extensively into the concept of Neuroadaptation, which will help you get the best out of your PIE procedure.
This book can serve as a dependable, truthful and reputed source of important information on the functioning of the eye, vision and the PIE procedure. It is our hope that we can facilitate the spread of quality vision through the aid of this book.
Chapter 1. Understanding vision and its deterioration in aging eyes
Our eyes are our main connection to nature, on earth and beyond. They allow us to bond with a beautiful world full of various colors, shapes, and sizes. Lack of vision affects the endocrine and neurological systems, even our mental wellbeing.
What is vision?
Many people often wonder how we are able to visualize the world. All light in our solar system originates from the sun. The light carries information from the sun. As it hits objects and animals the information gets changed. Decoding this modified information allows us to create an image of the world. The eye and brain work in tandem to unravel this information. The role of the eye is to focus the incoming light on a specialized area, which is connected to the brain. The brain interprets the signal and utilizing stored information or memories reconstructs the world in three dimensions.
Engineers and physicists inform us that though signals have information about the surrounding world they also have unwanted aberrations. The eye must concentrate these incoming signals so that an optimum electrical signal can be generated and transmitted to the brain. The role of eyes is obvious. It does not actually see, instead it assimilates and conveys signals to the brain. The brain is the final decision maker to differentiate relevant data from trivial data that needs to be ignored.
Figure 1.1 Normal eye shows object, image on retina and recreation in the brain
A normal eye is designed such that the converging power and the length of the eye match a mathematical formula. This miracle of evolution, or design, whichever you believe in, is astounding. Let us see the intricate construction of the eye.
Evolution of Vision
The world is an artist’s canvas. Everywhere we turn, we see a brilliance of colors and shapes. Have you ever stopped for a moment and thought how this came about? I am not referring to the creation of the universe. I am asking you to introspect on the observation and interpretation mechanism. How did the eyes and visual cortex in the brain evolve? How are they able to develop with such precision?
This fascinating development is the key to understanding how vision works and why eyes age. Once we understand the root problem, it becomes easier to tackle it. A one celled organism troubled by light decided to move away. That may have been the first interaction between light and future eyes. Gradually, as creatures became multicellular, a specialized area developed to interact with light.
If we were to look at this from a philosophical point of view, we would ask when and which organism decided that light may not be an enemy but a friend. It may not always be a be a benefit to run away from the light. There is crucial information in the incoming light, which is advantageous to survive in the predatory world. This is a topic best left for evolutionary biology. We can jump ahead to humans.
In ancient times when humans were mainly hunters, people with vision abnormalities, like nearsightedness or farsightedness, would have been the weakest link when searching for prey and also escaping predators. Predators eliminated these visually abnormal inpiduals preventing them from procreating and passing on their less than perfect genes. Hunters then settled down to start farming which made life easier for people with eye abnormalities. Even if the grain appeared blurry it would not pounce on you. Tending to a farm could still be achieved with less than perfect vision.
This status quo persisted for many centuries. It was disrupted when a visionary discovered that curved glass can help in focusing images. Curved glasses are called prisms. Prisms stacked together generate glasses. You all are aware of the benefits of glasses.
The next leap in the evolution of vision correction had to wait till the turn of the millennium. Lasik was invented to counteract the nearsighted explosive boom. Lasik can reshape the cornea and correct myopia, hyperopia and even astigmatism. Now we are on the cusp of the next revolution – to reverse the aging of the eye.
The Structure of the Eye
The eye can be compared to an onion in that both objects are composed of layers. There are three layers of the eye which are
sclera, choroid and retina. Each has a unique function.
Figure 1.2 Structure of the human eye.
The outermost white layer is called the sclera. The function of the sclera is protection. The front part of the sclera is specialized, to form the clear see-through cornea. The next layer is the pigmented choroid. The dark color of this layer blocks light. This converts the eye into a darkroom where the images can be processed.
The front part of this layer is called the iris and it is what gives color to the eye. The iris is behind the clear cornea. The innermost and most delicate layer is the neurosensory retina. In fact, this layer is an extension of the brain. The retina converts the light energy into electrical signals, which are then transmitted to the occipital lobe or back of the brain.
The light beam from the sun is the ultimate power source of all. The photons from the sun traverse millions of miles, are reflected off objects, and then ultimately enter our eyes. The photons stimulate receptors, which are like computer chips, generating electric signals. The maximum number of receptors are located in the area of the retina known as the macula. The center of the macula is called the fovea.
Figure 1.3 Errors of refraction
Errors of Refraction
If the information carrying photons converge to a point in
front of the retina, then the patient is nearsighted. If the light comes to focus at a single spot in front of the retina, this is termed as myopia or near sightedness. The person will be able to see things at a close distance but unable to see far.
On the other hand, if the photons are not brought to focus at all by the time the light crosses the retina, it is defined as farsightedness or hypermetropia. This person has trouble seeing near and middle distances and even far. In astigmatism, the photons are brought to focus at different points in the eye.
In more complicated cases, some light beams may come to focus in front of retina and others behind the retina. In each of these cases some amount of information is lost. The brain than constructs a defective view of the world. A person will see blurry at all distances and may need to squint in an effort to improve vision. This can give rise to eye pain and headaches.
These errors of refraction are different from Presbyopia. Presbyopia is defined as thickening and loss of elasticity of the lens, preventing the lens from changing shape. This manifests as the inability to see near with the natural aging process. These anomalies of refraction are physical limitations, whereas presbyopia is a physiological defect. In other words, these three errors occur because of a mismatch between the shape or power of the cornea and the length of the eye.
Presbyopia is due to the weak action of internal eye muscles. With increasing age, presbyopia can occur with myopia, or with hypermetropia and astigmatism. The function of refractive surgery is to ensure that the maximum number of photons of solar energy are brought to the receptors without a loss of the encoded information.
The optic nerve and its pathways carry the signals from the retina to a super specialized area of the brain called occipital lobe. If we were to draw a perpendicular line through the optic nerve, the fibers towards the ear are the temporal fibers, whereas the fibers towards the nose are termed as nasal fibers. On the way, half the fibers from each eye cross over to the other side. It results in the nasal half of the fibers from the right eye reaching the left occipital lobe.
The temporal fibers proceed without crossing. So, the left occipital lobe gets information from the left or temporal half of left eye and nasal half of right eye. Nasal half fibers actually receive information from the temporal half of the visual field. When the electrical signals reach the occipital lobe, they are converted into images which are interpreted by the higher centers of the brain.
The neuroelectric pathway from the retinal receptors to the occipital lobe need to be functioning properly for us to enjoy the sensation of vision and perceive the world. Glaucoma, which affects optic nerve, can lead to defects in vision. Strokes or tumors in the region of the optic pathways can cause blindness in half the field of vision. If the occipital lobe has a decreased blood supply or bleeding, it results in cortical blindness.
The eye is an engineering marvel; it is dynamically assembled and must modulate its converging power to see things at different distances. The eye can be compared to a highly sophisticated camera, because of the similarity between the lens system of a camera and the human lens of the eye. The camera film or computer chip is similar to the macula of the retina. In turn, the beams of light must be brought to a focus onto photographic film or a chip, which can be compared to the retina of the eye.
Basic optics tells us that objects at different distances will be brought to focus at different points. Some of these may be in front of the retina, some on the surface of the retina, and others behind the retina.
We can only see the image, which falls onto the retina, and is in fact an extension of the brain. It then becomes imperative, that to enjoy the natural world, we need to have a mechanism to adjust the focal length of the eye.
Unfortunately, it is not possible to adjust the actual length of the eye, however there is the option of modulating the focusing power of the lens used. This is achieved by a dynamic change in the curvature of the lens, which results in a corresponding change in the power of the eye. The lens is formed in the eye while one is still in their mother’s womb. After birth, the lens continues adding new material for the rest of one’s life.
Physically, the human eye lens is a clear oval biconvex shape (like a magnifying glass), which can change curvature as needed. In youth, the lens changes its curvature to adjust its power and retains the image on the retina. Age begets an older thicker lens. Curvature adjustment becomes a progressively difficult chore and begins failing by sixty years of age.