1. Essentials of Pathophysiology
Chapter 38 Disorders of Special Sensory Function: Vision, Hearing, and Vestibular Function

2. Pre lecture quiz (true/false)
Conjunctivitis, or inflammation of the conjunctiva, can be caused only by viral organisms.
The eustachian tube is lined with a mucous membrane that is continuous with the nasopharynx, and provides a passageway for pathogens to enter the middle ear.
Ringing of the ears is known as tinnitus.
Many drugs are labeled as ototoxic, or damaging to inner ear structures.
Hearing impairment may have a detrimental effect on language development in children. F T

3. Pre lecture quiz
_____________, a group of conditions that feature an optic neuropathy, is usually associated with an increase in intraocular pressure.
______________ is a disorder of refraction that allows an individual to see objects at close distances without problems, but distant objects are blurred.
A lens opacity that interferes with the transmission of light to the retina is known as _______________.
______________ media refers to inflammation of the middle ear, usually associated with an acute infection or an accumulation of fluid.
An illusion of motion, often described as a sensation of spinning or tumbling, is a disorder of vestibular function known as ________________.
Cataracts
Glaucoma
Myopia
Otitis
vertigo

4. Eye Anatomy Discussion
List the structures light must pass through on its way from the outside to the retina
What part does each structure play in vision?

5. Disorders Affecting the Anterior Chamber
Conjunctivitis
Corneal abrasion
Corneal edema
Keratitis
Glaucoma
Open-angle
Angle-closure

6. Scenario
B. is a 13-year-old girl who is involved in youth recreation programs at the community center where you volunteer
She complains of eye irritation
The left eye is reddened and watery, with some crusting on the eyelashes
Question:
What possible disorders will you consider?

7. Aqueous Humor Aqueous humor is formed by the ciliary body
It then flows between the iris and the lens to enter the anterior chamber
In the anterior chamber, it delivers food and oxygen to the lens and cornea
Then it drains into tubules of the trabecular meshwork
They empty into the canal of Schlemm

8. The area where the iris meets the cornea It contains the:
Iridocorneal Angle
The area where the iris meets the cornea
It contains the:
Trabecular meshwork
Canal of Schlemm

9. Angle-closure Glaucoma
The iris is displaced forward
Usually due to iris thickening caused by pupil dilation
The angle is closed so aqueous humor cannot flow in to the trabecular meshwork
Rapid buildup of aqueous humor in the anterior chamber

10. Open-angle Glaucoma The iridocorneal angle remains open
Trabecular meshwork abnormality decreases the rate of aqueous humor reabsorption
Gradual buildup of aqueous humor

11. Question
Tell whether the following statement is true or false. Angle-closure glaucoma results in gradual buildup of aqueous humor in the anterior chamber.

12. Answer
False Rationale: Open-angle glaucoma results in gradual buildup of aqueous humor in the anterior chamber (because the iridocorneal angle stays open). In angle-closure glaucoma, the iridocorneal angle is closed, so the aqueous humor accumulates quickly.

13. Lens Disorders
Disorders of refraction
Hyperopia
Myopia
Astigmatism
Disorders of accommodation
Presbyopia
Cataracts

14. Retinal Blood Supply
Retinal artery enters the eye through the center of the optic nerve
Retinal vein leaves the eye through the same nerve
The retina has a second blood supply from the choroid blood vessels directly behind it

15. Normal Appearance of the Retina
Optic nerve enters at the optic disk
Retinal arteries and veins can be seen at the center of the optic disk
Retinal blood vessels are smooth with relatively straight paths

16. Question
What vessel(s) supply blood to the retina?
Retinal artery
Choroid vessels
Optic artery
All of the above
a and b

17. Answer
a and b
Rationale: The retina receives blood from the retinal artery (mainly), and secondarily from the choroid vessels that are posterior/dorsal to it.

18. Papilledema or Choked Disk
Increased intracranial pressure affects the optic nerve
Optic disk protrudes into eye, with blurred margins
Blood vessels in its center are not distinct; the pressure has made them collapse

19. Damage to small retinal blood vessels
Retinopathy
Damage to small retinal blood vessels
Microhemorrhages
“Cotton-wool” exudate
Microaneurysms

20. Retinopathy (cont.) Neovascularization New vessels are more fragile
New vessels attach too tightly to the vitreous, fusing it to the retina

21. Retinal Detachment
Retina is separated from the choroid blood vessels behind it
Retinal cells lack oxygen
Cannot make enough ATP
Stop functioning
Painless loss of vision in the part of the retina that is detached

22. Macular Degeneration Dry Degeneration of retinal cells Wet
Neovascularization of the choroid
Blood vessels leak
Fluid buildup pushes retina away from choroid

23. Question
Which retinal disorder is caused by ischemia of the retina?
Papilledema
Retinopathy
Retinal detachment
Macular degeneration

24. Answer
Retinal detachment
Rationale: In this disorder, the retina becomes detached/removed from the blood vessels behind it (choroid vessels). Because the blood supply is diminished, less oxygen travels to retinal cells. Oxygen and glucose are needed to make ATP (energy); without oxygen, ATP can’t be produced, and the cells die.

25. What are the possible explanations for this client’s visual problems?
Scenario
Mrs. X is 47 years old and has been having trouble with her eyes; she says that she has trouble focusing and has had to get reading glasses
A few weeks ago she had an episode of “sparkling” in her left eye, and now there seems to be a shadow in her vision from that eye
Question:
What are the possible explanations for this client’s visual problems?

26. Scenario (cont.)
She did not have a detached retina but has returned to her doctor because the episode recurred and this time has not gone away
When the doctor tests her vision, she has identical defects in the right superior visual field of both eyes
Question:
What might be going wrong?

27. Discussion
Arrange the structures of the optic neural pathways in the correct order.
Optic nerve
Lateral geniculate nucleus
Optic radiation
Optic chiasm
Eye
Optic tract
Visual cortex 2 5 6 3 1 4 7

28. Discussion Eye Optic nerve Optic chiasm Optic tract
Lateral geniculate nucleus
Optic radiation
Visual cortex

29. Discussion
List the structures a sound wave goes through as it enters the ear.
Which structures:
Direct the sound wave?
Transmit the sound wave?
Create a nerve impulse in response to the sound wave?

30. Middle Ear Conducts sound from eardrum to inner ear
Eustachian tube lets air in and out to maintain equal pressure on both sides of eardrum

31. Middle Ear infection
If the Eustachian tube becomes blocked, fluid builds up in the middle ear. This creates a haven for bacteria and viruses, which can cause infection. Doctors can detect fluid in the middle ear with a pneumatic otoscope. This device blows a small amount of air at the eardrum, making the eardrum vibrate. If fluid is present, the eardrum will not move as much as it should.

32. Ear tubes, or tympanostomy tubes
If your child has recurrent ear infections or fluid that just won’t go away, hearing loss and a delay in speech may be a real concern. One solution is for your doctor to insert small tubes through the eardrum. Ear tubes let fluid drain out of the middle ear and prevent fluid from building back up. This can decrease pressure and pain, while restoring hearing. The tubes are usually left in for 8 to 18 months until they fall out on their own.

33. Middle Ear Disorders Problems with pressure in the middle ear
Patent eustachian tube, eustachian tube obstruction, acute otitis media
Problems with adhesions between the ossicles
Adhesive otitis media, otosclerosis
Problems with erosion of the tissues
Cholesteatoma, mastoiditis

34. Conductive Hearing Loss
Ossicles do not conduct sound from eardrum to inner ear
Sounds that enter through the ear sound faint
Sounds that are conducted through other bones of the head sound louder
Chewing
Own voice

35. Inner Ear: Cochlea and Labyrinth

36. Disorders of the Inner Ear and Auditory Pathways
Increased nerve firing
Tinnitus
Focal seizures
Decreased nerve firing
Sensorineural deafness
Presbycusis

37. Question
Which auditory disorder is characterized by increased firing of the otic nerve, causing “ringing” in the ears?
Otosclerosis
Conductive hearing loss
Tinnitus
Sensorineural deafness

38. Answer
Tinnitus
Rationale: Increased firing of neurons of the inner ear results in the classic symptom of “ringing” in the ears. Sensorineural deafness is caused by less frequent firing of neurons in the inner ear; otosclerosis is caused by adhesions between the ossicles in the middle ear; conductive hearing loss is the result of the ossicles’ inability to conduct sound from the eardrum to the inner ear.

39. Vertigo Motion sickness Meniere disease
Benign paroxysmal positional vertigo
Central vestibular disorders
Sudden dizziness when positioning head to certain position