Biooptics Concept Lesson Notes

Biooptics Concept Biooptics consists of the words bio and optics. Bio is defined as living creatures/living substances or certain parts of living creatures, while optics is the part of physics that is related to light or rays. The main focus in biooptics is related to the human sense of sight, namely the eyes. The eye is the most important optical instrument in humans or living creatures. 1. Eye Anatomy The eye functions as a visual organ that receives stimulation in the form of light and is transmitted to the brain by sensory nerves to produce visual information. The eyes are shaped like balls, and the front of the eyes is where light enters. The outer part of the eye has a white, stiff, hard layer called the sclera. In the bulge area of the eye there is a transparent layer through which light passes, called the cornea. The eyes are located in fat pads that can absorb shock. The diameter of the human eyeball is ± 2.5 cm. The eyes can work effectively to receive light with a very wide intensity range of around 10 billion light.. a. Eyelid is part of the eyeball protection. The eyelids function as a protector by spreading tears in the conjunctiva and cornea so that the eyes do not dry out. The eyelids have hairs that grow around the edges of the eyelids to keep out dust and insects. The eyelids also have thinner skin than the skin on other parts of the body. The eyelids consist of fibrous tissue and the orbicularis oculi muscle, which is innervated by the sympathetic nerve. b. Conjunctiva The outermost part of the eyeball with blood vessels. The mucous membrane that lines the eyelids and protects the outer eyeball. The conjunctiva is divided into two (two). Namely the palpebral conjunctiva (covers the eyelids) and the bulbous conjunctiva (covers the anterior part of the eyeball). The conjunctiva acts as a protector for the sclera and moisturizes the eyeball c. Cornea It is the clear membrane of the eye, if it becomes cloudy it will be very disturbing vision. A clear window that protects the delicate structures behind it and helps focus images on the retina. The cornea is ± 0.5 mm thick and does not contain blood vessels d. Sclera It is a strong white connective tissue under the conjunctiva and is part of the relatively stiff consistency around the eyeball. The sclera is formed from interconnected collagen fibers of varying widths, located above the ground substance and maintained by fibroblasts. The thickness of the sclera varies, 1 mm around the optic nerve papilla and 0.3 mm just posterior to the muscle insertion. e. Retina The retina is the nerve for vision. The retina contains the endings of the optic nerve. When an image is captured (caught by the eye), the light rays of the object being seen penetrate the cornea, aqueus humor, lens and vitreous body to stimulate the nerve endings in the retina. Stimuli received by the retina travel through the visual tract to the visual areas of the brain for interpretation. f. Uvea It is a layer of blood vessels in the eyeball, which consists of three parts: the iris, ciliary body, and choroid. The iris forms the central pupil and controls the amount of light entering the eye. The ciliary body produces fluid that fills the eye chamber, while the choroid is a layer that contains many blood vessels to provide nutrition for the eye g. Pupil The pupil is the coordinator of the light requirements needed. The size is adjusted to the movement of the iris. The black circle in the center is the pupil. In dark places, the iris contracts and the pupil dilates (mydriasis). Conversely, with strong light, the iris relaxes and the pupil contracts (miosis), so that the incoming light is less influenced by the parasympathetic nerves. h. Eye lens The lens is a central focusing organ, which refracts light rays reflected from the object being observed into a clear image on the retina. 2. Viewing Process Mechanism The visual process begins with light reflected from objects. If no light is reflected from an object, the eye cannot see it. The process of seeing through an object is as follows: 1) Light reflected from an object is captured by cornea, and penetrates the pupil. 2) The light intensity regulated by the pupil is directed through the crystal lens of the eye. 3) The accommodation power of the eye lens adjusts the light so that it hits the yellow point precisely. 4) At the yellow point, light is received by pyramidal cells and rod cells and then transmitted to the brain. 5) Light entering the brain is translated by the brain so that we can know what we are seeing The mechanical process of seeing begins when objects reflect light entering the eye and being received by the cornea, pupil, lens, and focused on the retina. In the retina, light is converted into electrical charges which are sent to the brain for processing through visual nerve fibers. So the brain's work results in people being able to see the objects they see. Images are captured by the eye, light rays of the object being seen penetrate the cornea, ukeus humor, lens, and vitreous body to stimulate the nerve endings in the retina. The stimuli received go to the visual area in the brain to be processed to produce the paintings and shapes that one sees. 3. Eye Disorders a. Myopia Myopia (farsightedness) is when the eye shape is too oval so that objects that are infinitely far away will be depicted sharply in front of the retina. Myopia sufferers are advised to use glasses with negative lenses. b. Hyperopia Hypermetropia (farsightedness) is a visual deviation where the eyeballs are slightly flatter than normal. In such an eye without accommodation the infinite image would lie behind the retina. Hypermetropic sufferers are advised to use glasses with positive lenses. c. Presbyopia Farsightedness and nearsightedness, also known as presbyopia or farsightedness, is a condition in which the lens loses its elasticity with age. As a result, the accommodation power of the eye lens is reduced. This eye disorder usually affects people who are old or over 45 years old. Presbyopia sufferers are unable to see objects that are too far or too close. d. Astigmatism (astigmatism) Astigmatism is a lens error caused by a point on an object forming a large angle with the axis so that there are two images formed, namely primary and secondary. Astigmatia is caused by a cornea that is not spherical in shape. e. Cataract This cataract condition occurs when there are spots or stains resembling fog that cover part of the lens of the eye, so that the eye cannot see clearly. The only solution to cure cataract sufferers is through action cataract surgery