Eyes

EXTERNAL STRUCTURES OF THE EYE The eyelids (upper and lower) are two movable structures composed of skin and two types of muscle: striated and sm

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Subject Overview

Structure and Function

The eye transmits visual stimuli to the brain for interpretation and, in doing so, functions as the organ of vision. The eyeball is located in the eye orbit, a round, bony hollow formed by several different bones of the skull. In the orbit, the eye is surrounded by a cushion of fat. The bony orbit and fat cushion protect the eyeball. To perform a thorough assessment of the eye, you need a good understanding of the external structures of the eye, the internal structures of the eye, the visual fields and pathways, and the visual reflexes.

EXTERNAL STRUCTURES OF THE EYE

The eyelids (upper and lower) are two movable structures composed of skin and two types of muscle: striated and smooth. Their purpose is to protect the eye from foreign bodies and limit the amount of light entering the eye. In addition, they serve to distribute tears that lubricate the surface of the eye (Fig. 15-1). The upper eyelid is larger, more mobile, and contains tarsal plates made up of connective tissue. These plates contain the meibomian glands, which secrete an oily substance that lubricates the eyelid. The eyelids join at two points: the lateral (outer) canthus and medial (inner) canthus. The medial canthus contains the puncta, two small openings that allow drainage of tears into the lacrimal system, and the caruncle, a small, fleshy mass that contains sebaceous glands. The white space between open eyelids is called the palpebral fissure. When closed, the eyelids should touch. When open, the upper lid position should be between the upper margin of the iris and the upper margin of the pupil. The lower lid should rest on the lower border of the iris. No sclera should be seen above or below the limbus (the point where the sclera meets the cornea). Eyelashes are projections of stiff hair curving outward along the margins of the eyelids that filter dust and dirt from air entering the eye.

The conjunctiva is a thin, transparent, continuous membrane that is divided into two portions: a palpebral and a bulbar portion. The palpebral conjunctiva lines the inside of the eyelids, and the bulbar conjunctiva covers most of the anterior eye, merging with the cornea at the limbus. The point at which the palpebral and bulbar conjunctivae meet creates a folded recess that allows movement of the eyeball. This transparent membrane allows for inspection of underlying tissue and serves to protect the eye from foreign bodies. The lacrimal apparatus consists of glands and ducts that serve to lubricate the eye (Fig. 15-2). The lacrimal gland, located in the upper outer corner of the orbital cavity just above the eye, produces tears. As the lid blinks, tears wash across the eye then drain into the puncta, which are visible on the upper and lower lids at the inner canthus. Tears empty into the lacrimal canals and are then channeled into the nasolacrimal sac through the nasolacrimal duct. They drain into the nasal meatus. The extraocular muscles are the six muscles attached to the outer surface of each eyeball (Fig. 15-3). These muscles control six different directions of eye movement. Four rectus muscles are responsible for straight movement, and two oblique muscles are responsible for diagonal movement. Each muscle coordinates with a muscle in the opposite eye. This allows for parallel movement of the eyes and thus the binocular vision characteristic of humans. Innervation for these muscles is supplied by three cranial nerves: the oculomotor (III) trochlear (IV), and abducens (VI).

 

What are the requirements?

  • Early Childhood Education, Elementary Education, Secondary Education, Special Education, Career & Technical Education (CTE) and Library Media Specialist • Hold a Level 1 Utah Educator License and teach for three academic years • Complete a professional portfolio • Receive two professional evaluations per year for three years in a Utah public, charter or accredited private school with a satisfactory final evaluation • Achieve a score of 160 or better on ONE of the four Praxis II PLT tests at the appropriate level of educational preparation; 0621 (5621), 0622 (5622), 0623 (5623), or 0624 (5624) • Work with a trained mentor for three years • Complete any additional Local Education Agency (LEA) requirements • Have a cleared background/fingerprint check within one calendar year; www.utah.gov/teachers • Receive a LEA recommendation for upgrade to Level 2 • Achieve NCLB HQ status in at least one licensure area, if qualified in any NCLB subject area • CTE may require additional coursework; contact CTE department at 801-538-7662 for information • Complete the Ethics Review at www.utah.gov/teachers • Complete a 2-hour, LEA-sponsored Suicide Prevention course

What am I going to get from this subject?

  • Universal Eye Health links to the Global Goal on Health. The Global Goal on Health aims to 'Ensure healthy lives and promote well-being for all at all ages

What is the target audience?

  • Target Audience EYE is focused on Audiences and helping brands and agencies better target their defined audience. We are members of and participating in the GeoPath Digital Location Based Measurement Pilot which will bring industry standard measurement to location-based media. Additionally, we work with mobile companies to utilize location data to understand audiences who are near our media placements. This enables EYE to help brands and agencies plan the best locations for their out-of-home media campaign and then to retarget that customer when they are in the right place at the right time.

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Subject Curriculum

eye

  • Structure and Function
     
  • What is the scientific term for the "white of the eye", the part surrounding the
     
  • PROMOTE HEALTH
     

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