What is meant by the pars plana?
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The pars plana is the flat part of the ciliary body in the eye, located between the iris and the choroid.
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What is meant by the pars plana?
The pars plana is the flat part of the ciliary body in the eye, located between the iris and the choroid.
What is the practical value of the pars plana?
The pars plana is often used as a site for surgical entry into the eye because it is relatively avascular and provides access to the vitreous body and retina.
What are the components of the orbital margin?
Frontal, Zygomatic, Maxillary.
What are the four walls of the orbital cavity?
Roof, Floor, Medial wall, Lateral wall.
What happens to the ocular axes when the eyes are directed from a distant object to a near object?
The medial recti bring about convergence of the ocular axes.
How does the lens change when focusing on a near object?
The lens thickens to increase the refractive power by contraction of the ciliary muscle.
What is the eyelid margin?
The edge of the eyelid where the eyelashes are located and where the eyelid meets the surface of the eye.
What is presbyopia?
Age-related loss in accommodative ability by about 50 years of age.
What happens to the pupils when focusing on a near object?
The pupils constrict to limit the light waves to the thickest central part of the lens.
Where is the anterior chamber located?
Between the cornea and the iris.
What structures are found at the eyelid margin?
Eyelashes, meibomian glands, and the openings of the lacrimal ducts.
At what age does presbyopia typically result in a complete loss of accommodation?
By about age 50.8 years.
What is the anterior chamber angle?
The angle formed between the cornea and the iris at the periphery of the anterior chamber.
What is the function of the meibomian glands located at the eyelid margin?
They secrete oils that help to keep the tear film stable and prevent evaporation of the eye's tear film.
What is the appearance of a normal optic disc?
The normal optic disc appears as a round or slightly oval structure with a distinct margin.
What is hypermetropia?
Long-sightedness.
What is the rate of decline in accommodative ability associated with presbyopia?
A linear decline of 2.3 diopters per decade.
What is the aqueous humor?
A clear fluid that fills the anterior and posterior chambers of the eye.
Why is the eyelid margin important for eye health?
It plays a crucial role in protecting the eye, maintaining tear film stability, and facilitating the drainage of tears.
What is the typical color of a normal optic disc?
The normal optic disc is typically a pinkish-orange color.
What is the palpebral fissure?
The opening between the upper and lower eyelids.
What are the two main causes of hypermetropia?
Axial length too short or converging power of the lens/cornea is too weak.
How is presbyopia treated?
With convex lenses such as reading glasses, bifocals, or trifocal lenses.
What are para-nasal sinuses?
Para-nasal sinuses are air-filled spaces located within the bones of the skull and face, connected to the nasal cavity.
What is the function of the ciliary body?
It produces aqueous humor and contains the ciliary muscle, which controls the shape of the lens.
What is another term for myopia?
Short-sightedness.
What is meant by the limbus and what is the practical value of this area?
The limbus is the border area between the cornea and the sclera. It is important for surgical procedures and for the drainage of aqueous humor.
What is astigmatism?
A condition where the corneal curvature in one meridian varies from the meridian at 90º, preventing light from coming to a single focus on the retina.
What is the function of photoreceptor cells in the retina?
They change light impulses into a nerve impulse.
What role do eyelashes play at the eyelid margin?
Eyelashes help to protect the eye from debris, dust, and other foreign particles.
What is the central depression in the optic disc called?
The central depression in the optic disc is called the optic cup.
What is the canthus?
The angle at either end of the eyelid aperture (medial and lateral canthus).
How does hypermetropia affect vision?
Distant objects are seen clearly, but near vision is blurred.
What is the primary function of the eyelids?
To protect the eyes from foreign particles and excessive light, and to help spread tears over the surface of the eye.
Which bones contain the para-nasal sinuses?
The frontal, maxillary, ethmoid, and sphenoid bones.
What is the Canal of Schlemm?
A circular channel in the eye that drains aqueous humor from the anterior chamber into the bloodstream.
What are the two main causes of myopia?
Axial length too long or converging power of the lens too strong.
Where is the cornea located?
The cornea is located at the front of the eye, covering the iris, pupil, and anterior chamber.
What visual difficulties are associated with astigmatism?
Difficulty in seeing both near and far objects.
Through which structures is the nerve impulse transmitted from the retina to the brain?
Via the optic nerve, optic tract, and optic radiations to the visual cortex of the brain.
What is the normal cup-to-disc ratio in a healthy optic disc?
The normal cup-to-disc ratio is usually less than 0.5.
What is the caruncle?
A small fleshy, epidermoid structure attached to the inner portion of the plica semilunaris.
What type of lenses are used to treat hypermetropia in spectacles?
Convex positive lenses.
What is the anatomical term for the edge of the eyelid where the eyelashes are located?
The eyelid margin.
How does the brain create a single mental picture from two images of the eyes?
Through a process called fusion.
What is the primary function of the para-nasal sinuses?
They help to lighten the weight of the skull, produce mucus, and contribute to voice resonance.
How does myopia affect vision?
People with myopia can see near objects clearly but distant objects are blurred.
Where is the posterior chamber located?
Between the iris and the lens.
Where is the conjunctiva located?
The conjunctiva is a thin, transparent tissue that covers the white part of the eye (sclera) and lines the inside of the eyelids.
What are the common methods to correct astigmatism?
Cylindrical lenses, hard contact lenses, and astigmatic keratotomy.
What type of image falls on the retina?
An inverted image.
What is the significance of the optic disc in the eye?
The optic disc is the point of exit for retinal nerve fibers and the entry point for the central retinal artery and vein.
What is the optic disc also known as?
Optic nerve head.
What is the plica semilunaris?
A soft, movable fold of the conjunctiva located at the medial canthus of the eye.
Besides spectacles, what are two other treatments for hypermetropia?
Contact lenses and surgery.
Which muscle is primarily responsible for closing the eyelids?
The orbicularis oculi muscle.
What is necessary for stereoscopic (3D) vision?
A small difference in the size of the two images.
How are the para-nasal sinuses connected to the nasal cavity?
They are connected through small openings called ostia.
What type of lenses are used to treat myopia in spectacles?
Concave or negative lenses.
What structures pass through the optic canal?
Optic nerve, meninges, ophthalmic artery, and sympathetic plexus.
What are the structures of the uvea?
The structures of the uvea are the iris, ciliary body, and choroid.
How does the brain process the inverted image that falls on the retina?
The brain instantly converts it so that it is seen the right way up.
What is another name for the macula?
Yellow spot.
What are puncta?
Openings of the tear ducts, easily seen on the medial aspect of the upper and lower lid margins when the eyelid is everted.
What is the role of the Meibomian glands in the eyelids?
They secrete an oily substance that prevents the evaporation of the eye's tear film.
What factors influence the refraction of light in the eye?
Smooth anterior curvature of the cornea, length of the eyeball, function of the lens, zonules, ciliary muscle, and transparency of the media.
What is the role of mucus produced by the para-nasal sinuses?
The mucus helps to trap and remove dust, pathogens, and other particles from the air we breathe.
Besides spectacles, what are two other treatments for myopia?
Contact lenses and refractive surgery.
What are the three layers that surround the optic nerve?
Dura mater, pia mater, and arachnoid.
Which nerves pass through the superior orbital fissure?
Lacrimal nerve, frontal nerve, trochlear nerve, oculomotor nerve, nasociliary nerve, and abducent nerve.
Where is the iris located?
The iris is located in the front part of the eye, surrounding the pupil and controlling its size.
What is the central part of the macula called?
Fovea centralis.
What is the name of the thin, transparent membrane that lines the inside of the eyelids and covers the white part of the eyeball?
The conjunctiva.
What role does the smooth anterior curvature of the cornea play in vision?
It influences the refraction of light.
Where is the optic nerve situated?
At the back of the eyeball and connected to the brain.
What veins pass through the superior orbital fissure?
Superior and inferior ophthalmic veins.
Where is the ciliary body located?
The ciliary body is located behind the iris and is responsible for the production of aqueous humor and accommodation of the lens.
What structures are responsible for blood supply in the retina?
Retinal arteries and veins.
What condition is characterized by inflammation of the eyelid margins?
Blepharitis.
How does the length of the eyeball affect vision?
It influences the refraction of light.
What is the lamina cribosa?
The area where the eyeball is penetrated by the optic nerve.
What structures pass through the inferior orbital fissure?
Infraorbital nerve, artery, vein, and zygomatic nerve.
Where is the choroid located?
The choroid is the vascular middle coat of the eye, situated between the outer sclera and the inner retina.
What is the clear gel that fills the space between the lens and the retina?
Vitreous humour.
What is the function of the levator palpebrae superioris muscle?
To elevate the upper eyelid.
What components are involved in the function of the lens in vision?
The lens, zonules, and ciliary muscle.
What is another term for the optic nerve head?
Optic disc.
What structures pass through the anterior and posterior ethmoidal foraminae?
Anterior ethmoidal nerve and artery, posterior ethmoidal nerve and artery.
Why is the transparency of the media important for vision?
It influences the refraction of light.
What are the zygomatico-facial and zygomatico-temporal foraminae?
They are openings in the orbit for the passage of nerves and vessels.
What is the transparent front part of the eye that covers the iris, pupil, and anterior chamber?
Cornea
What is the white, opaque, fibrous outer layer of the eye?
Sclera
What is the thin, transparent tissue that covers the outer surface of the eye and lines the inside of the eyelids?
Conjunctiva
What is the border area where the cornea meets the sclera?
Limbus
What part of the eye controls the amount of light that enters by adjusting the size of the pupil?
Iris
What is the transparent, biconvex structure in the eye that helps to refract light to be focused on the retina?
Lens
What are the fibers that connect the lens to the ciliary body, helping to hold the lens in place?
Zonules
What is the clear gel that fills the space between the lens and the retina in the eyeball?
Vitreous
What is the light-sensitive layer of tissue at the back of the inner eye that converts light images into nerve signals?
Retina
What is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera?
Choroid
