External1,2,8 Flashcards
در موارد recurrent corneal erosion درمان با naclرا تا چه مدت باید ادامه داد؟
6_12 months
خصوصیات BCLمورد استفاده در recurrent corneal erosion؟
high DK
flat BC
Megalocornea
nonprogressive
13 mm or greater
usually bilateral, congenital usually X linked
90%male
Association with X linked megalocornea
Iris transilluminationm
Deep AC
Late changes seen in X linked megalocornea
corneal mosaic degeneration (shagreen), arcus juvenilis, presenile cataracts, and
glaucoma. Treatment includes lubrication if patients have exposure keratopathy
Cilia are replaced every 3–5 months; they usually regrow in 2 weeks when cut and within 2 months if pulled out
Holocrine sebaceous glands and eccrine sweat glands are present in the eyelid skin.
Near the eyelid margin are the apocrine sweat glands (the glands of Moll) and numerous sebaceous glands (the glands of Zeis)
Smooth-muscle fibers from the levator muscle maintain the superior fornix, and fibrous slips extend from the horizontal rectus tendons into the temporal conjunctiva and plica to form cul-de-sacs during horizontal gaze
The cell morphology of the conjunctival epithelium
varies from stratified cuboidal over the tarsus to
columnar in the fornices to squamous on the globe
چند درصد سلولهای بازال اپیتلیوم کونژ را سلولهای گابلت تشکیل می دهند؟
۱۰ درصد
most numerous in the tarsal conjunctiva and the inferonasal bulbar conjunctiva
Conjunctiva-associated lymphoid tissue (CALT)?
consists of lymphocytes and other leukocytes, is present, especially in the fornices
Blood supply of the conj?
The palpebral conjunctiva shares its blood supply
with the eyelids. The bulbar conjunctiva is supplied by
the anterior ciliary arteries branching off the ophthalmic
artery. These capillaries are fenestrated and leak
fluorescein just as the choriocapillaris does.
Lacrimal Functional Unit components?
LFU
Lacrimal glands
ocular surface (cornea, conjunctiva, and meibomian glands)
eyelids
sensory and motor nerves
نقش LFU؟
regulation, production, and health of the precorneal tear film.
How LFU works?
The afferent component of the LFU is mediated through nociceptors found in the cornea and ocular surface and passing through the trigeminal nerve (cranial nerve V). These nociceptors synapse in the brainstem with autonomic and motor (efferent) nerves. The autonomic
nerve fibers innervate the meibomian glands, conjunctival goblet cells, and lacrimal glands. The
motor nerve fibers innervate the orbicularis muscle to initiate blinking, with the blink rate in adults
being about 15 times per minute. During blinking, the meibomian glands express lipid, and the tears
are replenished from the inferior tear meniscus and spread across the cornea while excess tears are
directed into the lacrimal puncta.
What is the most important refractive interface of the eye and is primarily responsible for maintaining a smooth optical surface between blinks?
The tear film
RI of the cornea?
1.376
Diameter of the cornea?
11–12 mm horizontally and 10–11 mm vertically
What is the corneal cap?
The cornea is aspheric, although its radius of curvature is often recorded as a spherocylindrical convex mirror
representing the central anterior corneal surface, also
called the corneal cap
What is The average radius of curvature of the central cornea?
7.8 mm
What is the dioptric power of a normal human eye?
The cornea contributes 74%, or 43.25
diopters (D), of the total 58.60 dioptric power of a
normal human eye
What is the major source of astigmatism in the optical system?cornea or lens?
The cornea
nutrition of the cornea?
glucose diffusing from the aqueous humor and oxygen diffusing through the tear film. In addition, the peripheral cornea is supplied with oxygen from the limbal circulation.
حساسیت قرنیه چند برابر کونژ است؟
the sensitivity of the cornea is 100 times that of the conjunctiva.
What is the sensory nerve of the cornea?
Sensory nerve fibers extend from the long ciliary nerves and form a subepithelial plexus
What is the Neurotransmitters in the cornea?
acetylcholine, catecholamines, substance P, calcitonin
gene–related peptide, neuropeptide Y, intestinal peptide,
galanin, and methionine-enkephalin.