Disorders of Vision, Ocular Movement and Hearing

Dr. Gerrard Uy

Vision

• Errors of refraction:– Myopia – globe is too long, light rays come to a

focal point in front of the retina – Hyperopia - the globe is too short, and hence a

converging lens is used to supplement the refractive power of the eye

– Astigmatism - corneal surface is not perfectly spherical, necessitating a cylindrical corrective lens

– LASIK (laser assisted in situ keratomileusis)-alter the curvature of the cornea

Vision

• presbyopia develops as the lens within the eye becomes unable to increase its refractive power to accommodate upon near objects– In middle age – older age– Emmetropic patient must use reading glasses– Hyperopic patient needs bifocals– Myopic patient only need to remove glasses

Transient or Sudden Visual Loss• Amaurosis Fugax– transient ischemic attack of the retina – transient monocular blindness– occurs from an embolus that becomes stuck within a

retinal arteriole• Optic Neuritis– inflammatory disease of the optic nerve– Sudden blurred or foggy vision– Pain when moving the eye– Most common cause is MS– all patients experience a gradual recovery of vision after a

single episode

Chronic Visual Loss

• Cataract– clouding of the lens sufficient to reduce vision– Most develop slowly as a result of aging– occurs more rapidly in patients with a history of

ocular trauma, uveitis, or diabetes mellitus– detected by noting an impaired red reflex when

viewing light reflected from the fundus – only treatment is surgical extraction

Chronic Visual Loss

• Glaucoma– slowly progressive, insidious optic neuropathy,

usually associated with chronic elevation of intraocular pressure; usually painless

– The mechanism whereby raised intraocular pressure injures the optic nerve is not understood

– acute angle-closure glaucoma, the eye is red and painful due to abrupt, severe elevation of intraocular pressure

Ocular Movement

• Oculomotor Nerve (CN III)– medial, inferior, and superior recti; inferior

oblique; levator palpebrae superioris; and the iris sphincter

– ptosis, a dilated pupil, and leaves the eye "down and out"

Ocular Movement

• Trochlear Nerve (CN IV)– Innervate contralateral Superior Oblique– hypertropia and excyclotorsion– vertical diplopia is also exacerbated by tilting the

head toward the side with the muscle palsy, and alleviated by tilting it away

Ocular Movement

• Abducens Nerve (CN VI)– Lateral rectus muscle– horizontal diplopia, worse on gaze to the side of

the lesion

Disorders of Hearing

• conductive hearing losses– lesions in the auricle, external auditory canal, or

middle ear,

• sensorineural hearing losses– lesions in the inner ear or eighth nerve

Conductive Hearing Loss

• obstruction of the external auditory canal by cerumen, debris, and foreign bodies

• Otitis externa/interna• swelling of the lining of the canal • atresia or neoplasms of the canal• perforations of the tympanic membrane• disruption of the ossicular chain• Otosclerosis• fluid, scarring, or neoplasms in the middle ear

Conductive Hearing loss

• Cholesteatoma– stratified squamous epithelium in the middle ear

or mastoid– slowly growing lesion that destroys bone and

normal ear tissue– Maybe congenital or acquired– Symptoms: ear discharge or hearing loss

Conductive Hearing loss

• Cholesteatoma– perforation of the tympanic membrane filled with

cheesy white squamous debris– Surgery is required to remove this destructive

process– 55 – 75% may recur

Cholesteatoma

Conductive Hearing Loss

• Otosclerosis– Fixation of the stapes– inherited as an autosomal dominant trait– hearing aid or a simple outpatient surgical

procedure (stapedectomy)

Sensorineural Hearing Loss

• Damage to the hair cells of the organ of Corti may be caused by:– intense noise– viral infections– ototoxic drugs– fractures of the temporal bone– meningitis– cochlear otosclerosis – Ménière's disease,– aging

• If age-related abnormality in VISUAL ACUITY is PRESBYOPIA, what is age-associated hearing loss?

Sensorineural Hearing Loss

• Presbycusis –– Age-associated hearing loss– most common cause of sensorineural hearing loss

in adults– Starts as loss of high frequency sounds– Associated with loss in clarity– Hearing aids– Cochlear implants

Sensorineural Hearing Loss

• Ménière's disease– characterized by episodic vertigo, fluctuating

sensorineural hearing loss, tinnitus, and aural fullness

– distention of the endolymphatic system (endolymphatic hydrops) leading to degeneration of vestibular and cochlear hair cells

– low-salt diet, diuretics, GC