The term "ciliary adjustment" refers to the process by which the ciliary muscles in the eye adjust the shape of the lens to focus on objects at varying distances. In terms of pronunciation, "ciliary" is typically pronounced /ˈsɪliəri/, with the stress on the second syllable, while "adjustment" is pronounced /əˈdʒʌstmənt/, with the stress on the third syllable. The spelling of the word is, therefore, fairly straightforward, with each of the component words being spelled as they are pronounced.
Ciliary adjustment refers to the mechanism by which the ciliary muscles in the eye contract or relax to modify the shape of the lens, thus allowing for both near and distant vision. It is a dynamic process involved in the accommodation of the eye.
The ciliary muscle is a ring of smooth muscle fibers that encircles the lens of the eye. When the eye focuses on a near object, the ciliary muscles contract, causing the suspensory ligaments attached to the lens to loosen. This allows the lens to become thicker and more curved, resulting in an increased refractive power to focus light onto the retina. This adjustment enables clear vision for objects that are closer.
Conversely, when the eye needs to focus on a distant object, the ciliary muscles relax. This causes the suspensory ligaments to tighten, making the lens thinner and flatter. Consequently, the refractive power decreases as light is now focused directly onto the retina for clear vision of objects that are far away.
Ciliary adjustment is controlled by the autonomic nervous system, specifically the parasympathetic branch. The signals from the brain to the ciliary muscles are mediated by the oculomotor nerve. Dysfunction in the ciliary adjustment mechanism can lead to various vision problems, such as presbyopia (the inability to see nearby objects clearly), myopia (nearsightedness), or hyperopia (farsightedness).
Overall, ciliary adjustment plays a crucial role in the eye's ability to focus on objects at varying distances, ensuring that clear and sharp images are formed on the retina for visual perception.
(1) The ciliary muscle and ciliary processes taken together; (2) the dentate nucleus.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "ciliary" originates from the Latin word "cilia", which means "eyelashes". It refers to the thin, hair-like structures present on the edge of eyelids. "Adjustment" comes from the Latin word "adiustare", which means "to arrange" or "to adapt". In the context of "ciliary adjustment", it refers to the ability of the ciliary muscles, which are responsible for adjusting the shape of the lens in the eye, to adapt and focus on near or far objects.