Anatomy & Refractive States of the Eye
Glossary

Myopia (nearsightedness): A refractive error in which the eyeball is too long in relation to its focusing power; thus the point of focus for rays of light from distant objects is in front of the retina.

Oculus Dexter (O.D.): The right eye.

Oculus Sinister (O.S.): The left eye.

Oculus Uterque (O.U.): Each eye.

Optic Nerve: The special nerve of the sense of sight that carries impulses from the retina to the brain.

Phoria: A root word denoting a latent deviation in which the eyes have a constant tendency to turn from the normal position for binocular vision; used with a prefix to indicate the direction of such deviation (for example, hyperphoria, esophoria, exophoria).

Presbyopia: A gradual lessening of the power of accommodation due to a physiologic change that becomes noticeable about the age of 40 years.

Ptosis Crutch: A small spring wire attached nasally to a spectacle frame to lift a drooping lid.

Pupil: The central opening of the iris through which light is permitted to enter the eye.

Regular Astigmatism: A refractive condition in which rays of light come to two focal points and is correctable by cylinders.

Retina: Innermost coat of the eye, formed of sensitive nerve elements and connected with the optic nerve.

Rods and Cones: Two different kinds of cells that form a layer of the retina and act as light-receiving media. Cones are concerned with visual acuity and color discrimination; whereas rods are employed for motion and vision at low degrees of illumination (night vision).

Sclera: The white part of the eye. A tough covering which, with the cornea, forms the external protective coat of the eye.

Scotoma: A blind area of reduced vision in the visual field.

Simple hyperopic astigmatism: The refractive condition where one point of focus falls on the retina and the other point of focus falls behind the retina.

Simple myopic astigmatism: The refractive condition where one point of focus falls on the retina and the other point of focus falls in front of the retina.

Strabismus: Failure of the two eyes to simultaneously direct their gaze at the same object because of muscle imbalance. Also known as squint.

Suspensory Ligaments: The suspensory apparatus of the lens. Numerous fine tissue strands that stretch from the ciliary processes to the lens equator and support the lens in place.

Tropia: A root word denoting an obvious deviation from normal of the axis of the eyes; used with a prefix to denote the type of strabismus (for example, hypertropia, esotropia, exotropia).

Vitreous Humor: The transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens.

 

 

Answers to the practice exercises on pages 14 & 16

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