Anatomy of the Eye and Visual Pathways Flashcards
Describe the shape of the bony orbit and the bones that make it up
Frontal, zygomatic, maxilla, lacrimal, palatine, sphenoid, ethmoid, pyramidal structure
What are the angles of the medial and lateral walls?
The medial wall is parallel to the midsagittal plane while the lateral wall is at 45 degrees to it.
What is the difference between the anatomical axis and the visual axis?
The visual axis is the line of sight while the anatomical axis is an imaginary plane that goes through the centre of the bony orbit, cutting it into a symmetrical left and right
What angle is the anatomical axis at to the midsagittal plane?
It is at 22.5
When are the visual and anatomical axes in the same plane?
When the eye is abducted by 22.5 degrees, the axes coincide.
Describe the outer layer of the eye
It is known as the fibrous tunic/coating and is a tough and collagen rich tissue. It is composed of the sclera (white) and the cornea (transparent). It is continuous with the dural sheath posteriorly.
Describe the middle layer of the eye
It is known as the vascular coating/tunic and is composed of the choroid, ciliary body and iris.
Describe the choroid
It is found in the vascular layer and is pigmented as it contains melanin. The melanin allows it to absorb light and so limits reflection.
Describe the inner layer of the eye
This is known as the neural layer and is composed of the retina. The retina is made of photoreceptors and multiple other cells arranged in layers. At the centre of the retina, there is the macula lutea where you have the sharp clear vision. There is also the macula lutea which is at the centre of the retina and where you get the sharp and detailed clear vision. At the centre of this, there is a depression called the fovea centralis which is where you get the highest visual acuity.
What is the optic disc? Where is it in relation to the macula lutea.
It is the physiological blind spot. It is a pale area and is where the optic nerve exits. It is also where the central retinal artery and vein branch out. It is medial to the macula lutea.
How do the features of the eye layers appear on a fundus photograph scan of the eye incl arteries, veins, optic disc, macula lutea, fovea centralis,
The veins are darker and wider while the arteries are lighter. The optic disc is brighter and more medial while the macula lutea and fovea centralis are lateral to the optic disc and darker.
Describe how the lens is adapted to change for far/near vision
The lens is connected to suspensory ligaments known as zonule fibres, these are attached to the ciliary muscle which is a ring like muscle. In far vision, the ciliary muscle is relaxed and the ligaments are taut meaning the lens is flat. In close vision, the ciliary muscle is contracted so the suspensory ligaments are relaxed making the lens thick.
What are the two segments of the eye?
There is an anterior segment and posterior. They are divided by the iris.
Describe the structure of the anterior segment of the eye and how fluid flows in it
It is sub-divided into two further chambers - anterior and posterior. The posterior chamber contains the ciliary body which produces aqueous humour. This fluid flows into the anterior chamber -> canal of schlemm.
Name the muscles of the eye and their CN supply
Extraocular muscles - sup, inf, med, lat rectus muscles and inf, sup oblique muscles. CN III (OM) - sup, inf, med rectus and inferior oblique. CN IV (Trochlear) - superior oblique. CN VI (Abducens) - lateral rectus.
Remember LR6 SO4
