Trans 002 Basic Science Of Ophthalmology . Flashcards
❛ Anatomically, the eyeball can be divided into three parts: ❜
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❛ fibrous, vascular, and inner layers. ❜
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❛ Outermost layer
• Consists of sclera and cornea, directly continuous with each other ❜
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❛ Its main functions are to provide shape to the eye and support the deepest structures ❜
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Fibrous layer of eyeball
❛ comprises the majority of the fibrous layer, approximately 85% and, provides attachment to the extraocular muscles (EOM), responsible for the movement of the eye. ❜
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❛ Sclera ❜
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❛ Lies underneath the fibrous layer.
• It consists of three continuous parts: choroid, ciliary body, and iris. ❜
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What layer of eyeball
Vascular
❛ is a layer of connective tissue and blood vessels. It provides nourishment to the outer layers of the retina ❜
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Choroid
❛ attach the lens to the ciliary body via zonular fibers (white arrow) which collectively formed the suspensory ligament of the lens. ❜
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Ciliary processes
❛ consist of collection of smooth muscle fibers arranged in three orientations: longitudinal, circular, and radial. ❜
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Ciliary muscles
Ciliary muscles plus ciliary process
Ciliary body
Explain the process of accommodation
❛ When ciliary muscle contracts the circular ciliary body reduces in size. When this happens, the zonular fibers, therefore, slacken, reducing the tension applied to the outside of the lens allowing the lens to return to a more rounded shape, this process is known an accommodation and adjusts the lens for near vision. ❜
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❛ Conversely, when the ciliary body is relaxed the diameter of the ciliary body is greater which means the zonular fibers are held tight, pulling the lens flat. This optimizes the lens for long distance vision. In addition to adjusting the lens shape, the ciliary body also contributes to the formation of aqueous humor. ❜
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❛ is a circular structure with an aperture in the center called the pupil ❜
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❛ the component of the eye which gives you your eye color ❜
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Iris
Circular versus radial fibers of Iris
❛ • The circular fibers make up the sphincter pupillae eye muscle which innervated by the parasympathetic nervous system. Activation of this system causes constriction of the pupil which thereby limits the amount of light that can enter the eye
• The radial fibers make up the dilator pupillae eye muscle which innervated by sympathetic nervous system and caused dilatation of the pupil thereby increasing the amount of light that can enter the eye ❜
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❛ • Light detecting part of the eye
• Comprised of two cellular layers, the neural layer and the pigmented layer ❜
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Retina
Neural layer versus pigmented layer of perina
❛ • The neural layer (light blue box consists of photoreceptors, the light detecting cells of the retina. It is located posteriorly and laterally in the eye.
- The pigmented layer (light green box) lies underneath the neural layer and is attached to the choroid layer. It acts to support the neural layer and continues around the whole inner surface of the eye.
- Anteriorly, the pigmented layer continues but the neural layer does not, this part is known non-visual retina
• Posteriorly and laterally both layers of the retina are present, this is the optic part. ❜
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Macula lutea vs fovea centralis
❛ The center of the retina is marked by an area known as the macula lutea, it is yellowish in color and highly pigmented. It contains a depression called the fovea centralis which has a high concentration cones which are the light-sensitive receptor cells which function best in brightly lit conditions and are responsible for high acuity color vision. ❜
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Optic disk
❛ The area that the optic nerve enters the retina is known as the optic disc, it contains no light detecting cells and is therefore referred as the blind spot of the retina. ❜
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Locates between the Correa and Iris
❛ The anterior chamber (yellow-shaded part) is located between the cornea and the iris. ❜
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❛ is a small chamber located behind iris and anterior to the lens and suspensory ligaments ❜
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❛ Posterior chamber ❜
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The chambers are filled with _ which is a clear plasma like fluid that nourishes and projects the eye
Aqueous humor
Trace the flow of the aqueous humor
❛ The aqueous humor (follow the trace of yellow arrow) is secreted first into the posterior chamber and flows into the anterior chamber via the pupil and then absorbed into the canal of Schlemm, aka the sclera venous sinus, this channel encircles the eye lying at the point between the cornea and the iris ❜
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