Trans 002 Basic Science Of Ophthalmology . Flashcards
❛ Anatomically, the eyeball can be divided into three parts: ❜
— Page 1
❛ fibrous, vascular, and inner layers. ❜
— Page 1
❛ Outermost layer
• Consists of sclera and cornea, directly continuous with each other ❜
— Page 1
❛ Its main functions are to provide shape to the eye and support the deepest structures ❜
— Page 1
Fibrous layer of eyeball
❛ comprises the majority of the fibrous layer, approximately 85% and, provides attachment to the extraocular muscles (EOM), responsible for the movement of the eye. ❜
— Page 1
❛ Sclera ❜
— Page 1
❛ Lies underneath the fibrous layer.
• It consists of three continuous parts: choroid, ciliary body, and iris. ❜
— Page 2
What layer of eyeball
Vascular
❛ is a layer of connective tissue and blood vessels. It provides nourishment to the outer layers of the retina ❜
— Page 2
Choroid
❛ attach the lens to the ciliary body via zonular fibers (white arrow) which collectively formed the suspensory ligament of the lens. ❜
— Page 2
Ciliary processes
❛ consist of collection of smooth muscle fibers arranged in three orientations: longitudinal, circular, and radial. ❜
— Page 2
Ciliary muscles
Ciliary muscles plus ciliary process
Ciliary body
Explain the process of accommodation
❛ When ciliary muscle contracts the circular ciliary body reduces in size. When this happens, the zonular fibers, therefore, slacken, reducing the tension applied to the outside of the lens allowing the lens to return to a more rounded shape, this process is known an accommodation and adjusts the lens for near vision. ❜
— Page 2
❛ Conversely, when the ciliary body is relaxed the diameter of the ciliary body is greater which means the zonular fibers are held tight, pulling the lens flat. This optimizes the lens for long distance vision. In addition to adjusting the lens shape, the ciliary body also contributes to the formation of aqueous humor. ❜
— Page 3
❛ is a circular structure with an aperture in the center called the pupil ❜
— Page 3
❛ the component of the eye which gives you your eye color ❜
— Page 3
Iris
Circular versus radial fibers of Iris
❛ • The circular fibers make up the sphincter pupillae eye muscle which innervated by the parasympathetic nervous system. Activation of this system causes constriction of the pupil which thereby limits the amount of light that can enter the eye
• The radial fibers make up the dilator pupillae eye muscle which innervated by sympathetic nervous system and caused dilatation of the pupil thereby increasing the amount of light that can enter the eye ❜
— Page 3
❛ • Light detecting part of the eye
• Comprised of two cellular layers, the neural layer and the pigmented layer ❜
— Page 3
Retina
Neural layer versus pigmented layer of perina
❛ • The neural layer (light blue box consists of photoreceptors, the light detecting cells of the retina. It is located posteriorly and laterally in the eye.
- The pigmented layer (light green box) lies underneath the neural layer and is attached to the choroid layer. It acts to support the neural layer and continues around the whole inner surface of the eye.
- Anteriorly, the pigmented layer continues but the neural layer does not, this part is known non-visual retina
• Posteriorly and laterally both layers of the retina are present, this is the optic part. ❜
— Page 3
Macula lutea vs fovea centralis
❛ The center of the retina is marked by an area known as the macula lutea, it is yellowish in color and highly pigmented. It contains a depression called the fovea centralis which has a high concentration cones which are the light-sensitive receptor cells which function best in brightly lit conditions and are responsible for high acuity color vision. ❜
— Page 4
Optic disk
❛ The area that the optic nerve enters the retina is known as the optic disc, it contains no light detecting cells and is therefore referred as the blind spot of the retina. ❜
— Page 4
Locates between the Correa and Iris
❛ The anterior chamber (yellow-shaded part) is located between the cornea and the iris. ❜
— Page 4
❛ is a small chamber located behind iris and anterior to the lens and suspensory ligaments ❜
— Page 4
❛ Posterior chamber ❜
— Page 4
The chambers are filled with _ which is a clear plasma like fluid that nourishes and projects the eye
Aqueous humor
Trace the flow of the aqueous humor
❛ The aqueous humor (follow the trace of yellow arrow) is secreted first into the posterior chamber and flows into the anterior chamber via the pupil and then absorbed into the canal of Schlemm, aka the sclera venous sinus, this channel encircles the eye lying at the point between the cornea and the iris ❜
— Page 4
❛ separates these two chambers form the vitreous chamber which fills the eyeball with a transparent gel-like substance known as vitreous humor or vitreous body ❜
— Page 5
Lens
❛ the fibrous outer protective coating of the eye, consisting almost entirely of collagen. ❜
— Page 5
Sclera
❛ contains numerous blood vessels that nourish the sclera. ❜
— Page 5
Episclera
❛ The brown pigment layer on the inner surface of the sclera is the ❜
— Page 5
❛ which forms the outer layer of the suprachoroidal space ❜
— Page 5
❛ lamina fusca ❜
— Page 5
How thick is the sclera?
❛ At the insertion of the rectus muscles, the sclera is about
0.3mm thick; elsewhere it is about 0.6mm thick ❜
— Page 5
Nerve a arterial supply of the sclera
Ciliary nerves; relatively avascular
❛ The reason for the transparency of the cornea and the opacity if the sclera is the ❜
— Page 5
❛ relative deturgescence of the cornea. ❜
— Page 5
Conjunctiva grows into the cornea
Pterygium
❛ blood in the anterior chamber ❜
— Page 5
❛ pus in the anterior chamber ❜
— Page 5
❛ hyphema ❜
— Page 5
❛ hypopyon ❜
— Page 5
True of false ❛ When the iris constricts, you have ciliary muscles relaxation. And when it dilates, you have ciliary muscles constrictions ❜
— Page 5
True
What consist of the uveal tract
❛ Uveal tract: iris, ciliary body, and choroid. ❜
— Page 5
What consist of the Uveal tissue
❛ represented by choroid, choriocapillaris and retina layers ❜
— Page 6
❛ It supplies anterior inner 2/3 of the eye and posterior 2/3 of retina is supplied by ❜
— Page 6
Ant, central retinal artery
Post: choriocapillaris
5 distinct layers of cornea
❛ five distinct layers: the epithelium, Bowman’s layer, the stroma, Descemet’s membrane, and the endothelium. ❜
— Page 6
❛ Sources of nutrition for the cornea: ❜
— Page 6
❛ vessels of the limbus, the aqueous, and the tears. ❜
— Page 6
❛ The sensory nerves of the cornea are supplied by the ❜
— Page 6
❛ first (ophthalmic) division of the fifth (trigeminal) nerve. ❜
— Page 6
❛ Dividing the anterior chamber from the posterior chamber, each of which contains aqueous humor. ❜
— Page 7
Iris ❛ The blood supply: major circle of the iris
• Iris capillaries have a non-fenestrated endothelium and hence do not normally leak intravenously injected fluorescein.
• Sensory nerve supply: fibers in the ciliary nerves ❜
— Page 7
❛ consists of a corrugated anterior zone, the pars plicata, and a flattened posterior zone, the pars plana. ❜
— Page 7
❛ CILIARY BODY ❜
— Page 7
❛ responsible for the formation of aqueous. ❜
— Page 7
❛ The ciliary processes and their covering ciliary epithelium ❜
— Page 7
❛ posterior segment of the uveal tract, between the retina and the sclera ❜
— Page 7
❛ bounded internally by Bruch’s membrane and externally by the sclera.
• Serves to nourish the outer portion of the underlying retina ❜
— Page 7
❛ CHOROID ❜
— Page 7
❛ internal portion of the choroid vessels is known as the ❜
— Page 7
❛ choriocapillaris ❜
— Page 7
❛ is a biconvex, avascular, colorless, and almost completely transparent structure, about 4mm thick and 9mm in diameter. ❜
— Page 7
❛ t is suspended behind the iris by the zonule, which connects it with the ciliary body. ❜
— Page 7
Lens
❛ is a thin, semitransparent, multilayered sheet of neural tissue that lines the inner aspect of the posterior twothirds of the wall of the globe. ❜
— Page 7
Retina
❛ The layers of the retina, starting from its inner aspect, are as follows: ❜
— Page 7
❛ (1) internal limiting membrane o (2) nerve fiber layer, containing the ganglion axons passing to the optic nerve o (3) ganglion cell layer o (4) inner plexiform layer, containing the connections of the ganglion cells with the amacrine and bipolar cells o (5) inner nuclear layer of bipolar, amacrine, and horizontal cell bodies o (6) outer plexiform layer, containing the connections of the bipolar and horizontal cells with the photoreceptors o (7) outer nuclear layer of photoreceptor cell nuclei o (8) external limiting membrane o (9) photoreceptor layer of rod and cone inner and outer segments o (10) retinal pigment epithelium ❜
— Page 7
❛ is supplied entirely by the choriocapillaris and is susceptible to irreparable damage when the retina is detached. ❜
— Page 8
Fovea
❛ Clear, avascular, gelatinous body that comprises two thirds of the volume and weight of the eye ❜
— Page 8
❛ • 99% water.
• The remaining 1% includes two components, collagen and hyaluronic acid ❜
— Page 8
❛ VITREOUS ❜
— Page 8
❛ is the anterior termination of the retina. It is continuous with the pars plana ❜
— Page 11
❛ Ora serrata ❜
— Page 11
❛ which is the target for cyclodestructive procedures in the treatment of intractable glaucoma, occupies the 2-3 mm directly posterior to the limbus. ❜
— Page 11
❛ pars plicata ❜
— Page 11
❛ longest intracranial course, and it is also the only nerve to originate on the dorsal surface of the brain stem ❜
— Page 12
Trochlear nerve
❛ The first (ophthalmic) of the three divisions passes through the lateral wall of the cavernous sinus and divides into the ❜
— Page 12
❛ lacrimal, frontal, and nasociliary nerves. ❜
— Page 12
