1. “Anatomy” Module Objectives
In this three-part learning module we will review parts of basic ocular anatomy and histology
We will emphasize retinal landmarks and other points important for Indirect Ophthalmoscopy in the patient with HIV/AIDS
We will discuss concepts that link anatomy to what you see when you examine the patient
We will not discuss many features of anatomy that have little relevance to clinical work with the patient suffering from HIV/AIDS

2. Anatomy of the Eye: I general overview
Learning Module

3. The eye has 3 basic layers, or “coats”
1. Outer fibrous coat (the walls and window)
Sclera & cornea
2. Middle vascular coat
iris, ciliary body & choroid
3. Inner neural coat (essentially part of the brain)
retina
DH: Great description and analogy

4. A microscopic cross section thru the back of the eye showing the three separate “coats” or layers of the eye (don’t be confused by the 10 different layers of the retina) * * *

5. retina
choroid
sclera

6. Conjunctiva
The conjunctiva is a thin, transparent mucous membrane covering the sclera and inner side of the eyelids.
Like other mucous membranes, such as the lining the nasopharynx, it is a frequent site of minor infections and trauma.
Tears, made by the lacrimal gland and other numerous small glands of the conjunctiva, constantly bathe the conjunctiva and cornea, removing dust and dirt, as well as killing bacteria.

7. Basic Eye Anatomy
Cornea: The cornea transmits and focuses light into the eye.
Cornea

8. Basic Eye Anatomy
Cornea: The cornea transmits and focuses light into the eye.
Iris: the colored part of the eye. The iris is a muscle that helps regulate the amount of light that enters the eye through the pupil.
Iris
Cornea

9. Basic Eye Anatomy
Cornea: The cornea transmits and focuses light into the eye.
Iris: the colored part of the eye. The iris is a muscle that helps regulate the amount of light that enters the eye through the pupil.
Lens: the transparent structure inside the eye that focuses light rays onto the retina.
Iris
Lens
Cornea

10. Basic Eye Anatomy
Vitreous: the clear, jelly-like substance that fills the middle of the eye.
Vitreous
Iris
Lens
Cornea

11. Basic Eye Anatomy
Vitreous: the clear, jelly-like substance that fills the middle of the eye.
Retina: the nerve layer that lines the back of the eye. The retina senses light and creates impulses that are sent through the optic nerve to the brain.
Vitreous
Iris
Retina
Lens
Cornea

12. Basic Eye Anatomy
Vitreous: the clear, jelly-like substance that fills the middle of the eye.
Retina: the nerve layer that lines the back of the eye. The retina senses light and creates impulses that are sent through the optic nerve to the brain.
Optic Nerve: the nerve that connects the eye to the brain. The optic nerve carries the impulses formed by the retina to the brain, which interprets them as images.
Vitreous
Iris
Retina
Lens
Cornea
Optic nerve

13. Sclera
The “white of the eye” - the acellular fibrous external coat of the eye
At the front of the eye, the sclera forms a transparent window, the cornea, and in the back of the eye it extends to the optic nerve
Attached to the sclera are six exterior muscles, which enable us to look left, right, up and down.
The sclera is pierced by vortex veins, ciliary arteries and nerves

14. Lens
The lens is responsible for focusing, or refracting light to form a clear image on the retina.
The lens is located behind the iris
Any loss of clarity of the lens is a “cataract”.

15. Ciliary body
The lining of the ciliary body secretes aqueous humour, the fluid which fills the front of the eye. The cells behave similar to parts of the kidney
Fibers (zonule) attached to the ciliary processes hold the lens in place behind the iris
The ciliary muscle causes the lens to change shape.

17. What has happened to the lens?

18. Normal Fundus
The optic disc (optic nerve) is round or oval . A “Disc Diameter” or “DD” is a common measuring stick for describing retinal lesions.
Optic disk

19. Normal Fundus
The fovea is in the center that is slightly darker than the background retina. It is temporal to optic disk by DD, and the center of the fovea is slightly inferior to the center of the optic nerved.
All fine vision or reading vision is from this area, less than 1% of the entire retinal surface.
“Visual acuity” on the eye chart tests only this 1% of the retinal surface!
Fovea
Optic disk

20. Normal Fundus
The superior and inferior temporal arcade of vessels start at the optic disc and travel above and below the macula.
Superior arcade
Fovea
Optic disk
Inferior arcade

21. Retina The retina is the innermost, neural coat
Receives light and converts to neural impulses that are sent to the cerebral cortex
It is derived from and is a part of the CNS, and it is the preferred site for “neurotropic” infectious agents such as the herpesvirus family (HSV, VZV, CMV), syphilis, toxoplasmosis

22. Optic Nerve
Optic disc- oval pale pink -1.5mm – with a central excavation (the cup) with pink neuro-retinal rim, and a clearly defined outer border
Made up of the 1 million fibers of the nerve fiber layer, that come together like an electrical cord to form the optic nerve and connect to the brain
Retinal vessels emerge from the disc and divide dichotomously, with veins and wider than arteries, in a ration of V:A = 3:2
The neural tissue is the pink tissue closest to the outer border. If the optic nerve is damaged and nerve fibers lost, (i.e after severe cryptococcal meningitis) the normal pink color is absent.

23. Normal Optic Nerve or Optic Disc
Sharply defined margin
of the optic nerve
Normal pink neuro-retinal
rim, made up of the collection
of nerve fibers
“cup” of the optic
nerve
Vein (darker and wider)
Artery
(brighter and narrower)

24. Choroid
Below the retina is the highly vascular choroid, layers of vascular channels, ribbon shaped and that freely anastomose
Provides blood supply for the outer half of the retina
It has the highest blood flow/unit volume of any tissue in the body.
It acts as the “radiator” of the eye, diffusing the heat created by the light that is focused on the retina by the cornea and the lens.
It is the preferred site for any infectious agent that is blood borne, such as disseminated TB, fungal sepsis, etc.

25. Note the normal choroidal markings: the “ribbon-like” freely connecting pattern of lines behind the retinal vessels
These are the choroidal vessels, seen thru the translucent retina

26. the “red reflex”

27. Red Reflex
Represents the reflection of light off of the retina – easiest seen with the pupil dilated
Is the same as the “red eye” with a camera flash.
A good “red reflex” means that the cornea, lens and vitreous are optically clear (Stated another way: the“view in” is clear)

28. Abnormal red reflex means…
1. you can’t see the retina
2. if you can see the retina, the retina is NOT NORMAL
(the reverse is not invariably true… sometimes the red reflex will be normal, but the retina will have disease)

29. Red Reflex
Abnormal
Red reflex
Normal red reflex

30. Poor or absent red reflex may be caused by:
Corneal scar or opacity
Cataract
Vitreous opacity (hemmorhage or inflammatory cells)
Disease of the retina (such as CMV retinitis)

31. Corneal Scar
No red reflex because of corneal scar (secondary to trachoma)

32. How can you tell the cornea is clear?
– and with advanced
Good “red reflex” which means
that the lens and vitreous are also
clear
Fine iris details visible thru the cornea,
which means that the cornea has to be clear

33. Note area of corneal scar with loss of ability to see the iris details where the scar blocks the view

34. Absent red reflex from cataract
iris details are visible,
so the cornea is clear.

35. 1. Name the 3 things that can interfere with the red reflex or “view in.”

36. 1. Name the 3 things that can interfere with the red reflex or “view in.”
Corneal scar
Cataract
Debris in the Vitreous

37. What is preventing a good red reflex in this patient?
Corneal Opacity
Cataract
Debris in the Vitreous
Same as the last slide

38. What is preventing a good red reflex in this patient?
Corneal Opacity
Cataract
Debris in the Vitreous
Note the absence of iris detail.

39. Explain what happened to the lens, and point out how this image demonstrates that a cataract can interfere with the red reflex

40. Blind from Cataract. Over half of the world’s blindness is caused by cataract, a treatable disease

41. Review

43. TEST 2. 3. 1. 4. 5.
This is a great slide, perhaps repeating the answers afterwards? 7. 8. 6.