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1. The period of time between the application of a stimulus and the resulting reaction. 2. The early period following bacterial inoculation into a culture medium, characterized by slow growth. SYN: lag phase; latent period. 3. The period between the application for some form of official recognition and approval or rejection by a regulatory agency.

lagophthalmos, lagophthalmus

(lăg″ŏf-thăl′mōs, -mŭs) [Gr. lagos, hare, + ophthalmos, eye] An incomplete closure of the palpebral fissure when an attempt is made to shut the eyelids. This results in evaporation of the tear film with exposure of the bulbar conjunctiva and cornea to drying, injury, and/or inflammation. This condition is caused by contraction of a scar of the eyelid, facial nerve injury, atony of the orbicularis palpebrarum, or exophthalmos.

 TREATMENT: Artificial tears or other ocular lubricants are needed to prevent corneal ulceration.

nocturnal l. Failure of the eyelids to remain closed during sleep, which may be due to chronic keratitis.

lag time to benefit

The gap between the employment of an intervention (such as a new treatment or screening test) and the beginning of its measurable impact on health. When the lag time exceeds a patient’s life expectancy, the intervention may even be harmful.


(lā′ĭ-tē) [Gr. laos, the people] Individuals who are not members of a particular profession such as law, dentistry, medicine, or the ministry.


live attenuated influenza vaccine.


[L. lacus] 1. A small cavity of fluid. SEE: lacus. 2. The appearance of plasma after blood cells in it have broken down, releasing their hemoglobin pigment.

lacrimal l. The small pouch formed by the junction of the conjunctiva at the medial canthus of the eye. Tears collect in this area before they drain through the lacrimal canaliculi into the nasolacrimal duct. The lacrimal lake can hold a normal amount of tears, but when excess tears are secreted, e.g., during crying, the tears overflow the lipid-coated edge of the lower lids and spill onto the cheeks. SYN: lacus lacrimalis.

venous l. 1. A small subcutaneous bleb filled with blood. It may be present on the lips, mouth, or ears. 2. A lateral pouch or diverticulum of the superior sagittal sinus of the brain into which protrude arachnoid villi that return cerebrospinal fluid to the venous circulation.


(lākd) A term used to describe the blood in hemolysis or disintegration of the red blood cells, freeing the hemoglobin into the blood plasma.


limulus amebocyte lysate.

La Leche League International

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