Intraocular Anatomy Flashcards
Name the three tunics of the ocular globe
Nervous. Vascular, Fibrous
What are the three parts of the fibrous tunic
Cornea, Sclera, Limbus
Describe features of the cornea
Anterior 1/4 of globe Optically clear Avascular Highly innervated
Cornea
Describe features of the sclera
Posterior 3/4 of globe White dense connective tissue Opaque Vessels penetrate sclera to supply deeper tunics
Describe the limbus
Junction of the cornea and sclera Attachment site of bulbar conjunctiva
What is the vasculature for the fibrous tunic
Conjunctival vessels
scleral vessels
List the three components of the vascular tunic
Choroid (posterior part)
Ciliary body and Iris (anterior part)
What is another name for the vascular tunic
Uvea or Uveal tract
Describe the choroid
Superficial to visual retina
Pigmented
Contains tapetum lucidum
Highly vascular - vascular supply to the retina
Describe the ciliary body
Anterior to choroid
Superficial to non visual retina
Has radially oriented processes
Has ciliary process and ciliaris muscle
Describe the iris
Anterior to ciliary body
Superficial to non visual retina
Forms the pupil
Describe the tapetum lucidum
Specialized reflective layer
Increases light reaching retina
Allows for night vision
Absent in pigs and humans
Describe the ciliary process
Radially oriented extensions of the ciliary body Site of attachment of zonule fibers
Describe the ciliaris muscle
Muscle deep within ciliary body
Contraction draws ciliary body centrally
Lowers tension on zonule fibers - causes lens to become convex (look at nerby objects)
Parasympathetic innervation- CN III
Describe the iris
Forms the pupil
The pupil controls the amount of light that reaches the retina
Choroid
iris muscles controls pupil size: iris dilator and constrictor
Describe the iris dilator m
Radial muscle fibers Contraction increases pupil size “Mydriasis”- large pupil size Sympathetic innervation
Describe the iris contrictor m
Circular muscle
Contraction decreases pupil size
“Miosis”- small pupil size
Parasympathetic innervation- CNIII
What are the boundaries of the anterior chamber
From the cornea to the iris
What are the boundaries of the posterior chamber
Iris to lens
What structure holds the anterior chamber open so as not to disrupt flow of aqueous humor
Pectinate lig
Describe the arrangement of the iris contrictor muscle fibers in the cat
Sine wave
What are iridic granules
Normal vascular structures on superior aspect or iris margin of horses and bovine
Purpose to to absorb extra light/protect
Note: on both superior and inferior for camelids
What is another name for the nervous tunic and what are the three components of it
The retina
Pars optica retinae, pars ciliaris retinae, pars iridica retinae
Describe the pars optica retinae
Lines deep aspect of the choroid
The ‘Visual Retina’
Contains light sensing cell layers
Describe the pars ciliaris retinae
Lines deep aspect of the ciliary body - ciliary epithelium
Part of the ‘Non-visual Retina’
No light sensing cell layers
Produces aqueous humor
Describe the pars iridica retinae
Lines posterior aspect of the iris
Part of the ‘Non-visual Retina’
What are the two basic layers of the nervous tunic
Pigmented retinal epithelium (PRE)
Nervous layer
describe the pigmented retinal epithelium
Present in pars optica retina, pars ciliaris retina, pars iridica retina
Adjacent to choroid, ciliary body, and iris
UNPIGMENTED where it lines tapetum lucidum! - allows light to reach “mirror like”
Describe the nervous layer
Layers of neuronal cells and photoreceptors
Present in pars optica retina only- the visual retina
Deep to the pigmented retinal epithelium (PRE)
light receptor layer is thick over choroid and then dramatically thins anteriorly
Describe which structures the optic cup develops into embyrologically
Outer layer of optic cup –> Pigmented layer of the retina (1 layer)
Inner layer of optic cup –> Neural layer (layers 2-10)
Where does detachment of the retina occur?
Between pigmented layer (PRE) and nervous layer (layers 2-10)
What is the ora serrata
junction where retina becomes thinner and visual/nonvisual retina connect
the serrated junction between the retina and the ciliary body. This junction marks the transition from the simple non-photosensitive area of the retina to the complex, multi-layered photosensitive region.
describe the lens
Located posterior to iris and pupil
Biconvex with an elastic capsule
Suspended by zonule fibers
Optically clear
Refracts light
What are lens fibers
Arranged concentrically in layers
Extend from anterior pole to posterior pole Join at poles in Y shape- “Y Sutures”
What is accomodation and how does it occur
Change in lens shape for visual focus
distance vision - Sympathetic stimulation, Ciliary m relaxed
near vision - Parasympathetic stimulation, Ciliary m contracted
What are the boundaries of the vitreous chamber and what is inside
lens and the retina
filled by vitreous body
What are the two segments of the ocular globe and what defines their boundaries
Anterior Segment: All the parts of the globe from the cornea to the lens
Posterior Segment: All the parts of the globe posterior to the lens
What is aqueous humor and what are its characteristics
Fluid present in the anterior and posterior chambers
A clear colorless fluid similar to CSF
Low protein content
Functions to maintain intraocular pressure and nourish cornea and lens
Aqueous humor production is constant - therefore to maintain intraocular pressure drainage must be constant
Describe the flow of aqueous humor
Produced by the pars ciliaris retina (“ciliary body epithelium”)
Flows into posterior chamber
Flows through pupil into anterior chamber
Drains at iridocorneal angle through a meshwork formed by the pectinate ligaments
Fluid is absorbed into the scleral venous sinuses and plexus
Describe the vitreous body and clin sig
Gel-like mass Maintains shape of globe Holds retina against choroid Constant in volume
if lost can lead to retinal detachment, why lens capsule (which is connected to the VB) is left if surgery is performed the remove the lens
What is the fundus and what structures are present in it
The posterior globe as seen through an ophthalmoscope
Structures of the Fundus:
Optic disc Visual retina Retinal vessels Tapetum lucidum
