Opthamology Flashcards
Pupil basics
Is a hole in the middle of the iris and is made up of the circular muscles and radial muscles
- circular = pupillary sphincter
- radial = pupillary dilator
What controls the circular and radial muscle contractions?
Circular (constriction of pupil)
- parasympathetic response
- occurs in bright light
- occurs when calm/relaxed
- occurs when high on opioids
Radial (dilation of pupil)
- sympathetic response
- occurs in dim light
- occurs when afraid
- occurs when high on cocaine/ amphetamines
What is anisocoria
Unequal pupils
in bright light:
- the larger pupil = loss of parasympathetics ipsilaterally
In dim light:
- the smaller pupil = loss of sympathetics ipsilaterally
What tumor is most common in causing horners syndrome?
Pancoast tumors
Anatomy of the sympathetics for the eyes
First order = hypothalamus
- runs down the brainstem and into spinal cord where it synapses at C8-T2
Second order = exits out C8-T2 and goes to the inferior cervical ganglion
- ruins over the apex of the lung around the subclavian artery and synapses on the superior cervical ganglion
Third order = exits off superior cervical ganglion and ascends along the carotid artery
- runs through cavernous sinus and innervates muscles via CN3 tract
Most common causes of ipsilateral Horner syndrome in ophthalmology
Brainstem stroke (usually medullary syndrome)
Cord hemisection (brown-sequard syndrome)
Pancoast tumors at apex of lung
Carotid artery dissections
Damage at the cavernous sinus
Anatomy of parasympatheticsof the eye
Afferent:
- Light signals are received through CN 2 and travels along the nerve
- Hemi-decussates at optic chiasm
- Synapses onto E-W nuclei bilaterally in the rostral midbrain near the superior colliculi
Efferent:
- travels along CN 3 from E-W nucleus
- synapses in the ciliary ganglion and runs along short ciliary nerves to innervate the iris sphincter
What is the most sinister etiology for a blown pupil?
3rd nerve palsy
- caused by aneurysm of the circle of wills or herniation of the uncus impinging on the CN 3
Classic clinical signs are
- ptosis
- mydriasis
- eye is down and out
Relative afferent pupillary defect (RAPD)
Results from a lesion in the CN2 nerve or some sort of damage.
- the pupils are always the same size but respond differently to light
(I.e shining light in the left eye = 100% constriction in both. Shining light in the right eye = 50% constriction in both)
Common causes are optic neuritis, MS, retinal artery occlusions
can cause red color dislocation (where red looks like orange)
What is a quick and easy way to differentiate 3rd nerve palsy from chemical mydriasis?
Use 1% pilocarpine eye drops on the dilated pupil.
- if it DOES NOT constrict = NOT 3rd nerve palsy
- if it DOES constrict = 3rd nerve palsy
What does a blurred optic disc signify?
A blockage of the axoplasmic flow from the optic nerve
Causes:
- ischemia to the nerve
- high cranium pressure
- optic neuritis
- metabolic dysfunctions (toxic ODs, hereditary mitochondrial diseases
what is OD vs OS abbreviations mean?
OD = right eye
OS = left eye
Papilledema
Swelling of the optic nerve at the retina which causes a swollen blurry optic disc which is CAUSED BY INCREASED INTRACRANIAL PRESSURE
if it is not caused by increased intracranial pressure, it is an “optic nerve disease” not papilledema
Idiopathic intracranial hypertension (IIH)
also known as Pseudotumor cerebri
Classic risk factors:
- use of tetracyclines
- over use of vitamin A
- obesity (especially rapid and recently)
Classic signs:
- transient visual obscurations
- pulsation tinnitus
- occasional horizontal diplopia
Diagnosis:
- increased CSF pressure > 25mmHg
- NO ABNORMALITIES IN CSF counts
What is a classic MRI sign for MS?
Bright finger-like projections of brain tissue that are just superior to the corpus callosum in the sagittal view.
Optic neuritis
More common in ages 20-40s
Very common with MS patients
Classic signs:
- pain in the eye that is losing vision
- eye movement causes pain in the eye
- red colors are less saturation (dissociation)
- requires brain and orbit MRI/CT to confirm*
When should your never LP a patient with papilledema or blurred optic disc?
If you have not ruled out a tumor yet.
if a tumor is present, LP will cause herniation of brain tissue to the medulla and impinge on it, causing respiratory and cardiac failure
Bitemporal hemianopia
Caused by lesion to the optic chiasm in sagittal fashion
- knocks out the lateral aspects of both eyes
common in pituitary tumors
Where does the fibers of the optic tract travel to?
The lateral geniculate ganglion (LGG) of the thalamus
- from here it becomes optic radiations and splits into an upper (parietal) and lower (temporal) pathways
The radiations travel directly to the visual cortex in the occipital lobe
Upper quadrantanopia
Damage to the lower (temporal part) of the optic radiations
Causes upper 1/4 visual blindness in either the right side of both eyes (left optic radiations) or the left side of both eyes (right optic radiations)
Lower quadrantanopia
Damage to the upper (parietal part) of the optic radiations
Causes lower 1/4 visual blindness in either the right side of both eyes (left optic radiations) or the left side of both eyes (right optic radiations)
What does damage tot he occipital lobe itself cause?
Causes similar defects to optic tract lesions
- mild subtly different though, but not important to know now
What is the general rule for visual fields?
Everything is flipped
Dorsal stream dysfunction
The “where” stream
Causes the following:
- stimultanagnosia: cant pay attention to more than one object at a time
- astereognosis: inability to perceive the depth perception of objects
- akinetopsia: inability to detect motion
Ventral stream dysfunction
The “what” stream
Causes the following:
- achromatopsia: cant see colors
- caused by bilateral lesions of the fusiform and lingual gyri
- prosopagnosia: cant recognize faces
- caused by bilateral/ right sided fusiform and anterior temporal lobe lesions
- topographagnosia: cant orient oneself to there surroundings
- caused by parahippocampal lesion
What is the inner layer of endothelium in the cornea responsible for?
Keep a dehydrated state of the cornea (keeps it clear)
- will turn opaque and cloudy if knocked out
What are the steps of a basic eye exam?
1) measure and record visual acuity
- if the vision is blurry naturally, use pinhole glasses
2) examine the pupillary responses
- afferent pupillary defect
- assess pupil shape/size and symmetry
3) examine ocular motility (pressure)
- range and symmetry of 9 cardinal positions of gaze
- assess the corneal light reflex or the cover/uncover technique
4) assess visual fields
5) assess palpation of the orbit globe (if not a trauma)
6) examine the important structures of the anterior segment of the eye with a penlight
7) examine the fundus with either a direct ophthalmoscope or fundus photography
Retinal detachments
Signs/symptoms
- often preceded by flashing lights/floaters in vision
- presents commonly as a “curtain encroaching towards central vision”
- typically sudden onset
- commonly occurs via trauma of posterior vitreous detachments
- many times does not show other clinical findings
*this is urgent and needs to be referred to dilated eye exam
What are the three main retinal vascular events?
Retinal arterial occlusion
- “cherry red macula”
Retinal vein occlusion
Amaurosis fugax
Amaurosis fugax
Signs and symptoms:
- very Broad often includes migraine, dry eyes, TIA, MS and elevated intraocular pressure
- there are not ocular findings during exams
- “curtain coming over my vision”
- this is worry some since it can cause a stroke
- monocular vision loss = carotid artery issues
- binocular vision loss = vertebral/basilar artery issues
What are common risk factors for cataracts?
Diabetes
Smoking
Elderly
When should you refer a red painful eye out to an ophthalmologist (be worried)?
STOP
Sudden visual loss/change
Trauma
Other signs/symptoms in conjunction
Pain (deep pain only)
- if not one of these 4 categories, is usually non-urgent*
Preseptal cellulitis
Urgent issue
Symptoms:
- red painful eye
- pain is increased with eye movement
- decreased overall vision
- fever and chills are present
treatment:
- gram positive antibiotics topical or oral
Corneal abrasion
Urgent issue
Symptoms:
- red painful eye
- often caused by trauma
- no foreign body present
Treatment:
- topical antibiotics
- DONT USE STEROIDS
What bacteria must always be considered in contact lens patients that present with red and painful eye?
Pseudomonas
What are the three main types of eye trauma?
Blunt
Penetrating
Perforating
- type 6 most common ocular trauma causes*
1) corneal abrasions
2) corneal foreign bodies
3) corneal or scleral lacerations
4) ruptured globe
5) hyphema
6) chemical injury
Difference between alkaline and acid chemical injuries to the eye
Acid:
- more painful
- less chance of penetrating
Basic:
- less painful
- more chance of penetrating
- both need to start with irrigating the eye and getting within optimal pH range*
What is the classic triad of symptoms for congenital glaucoma?
Photophobia
Epiphora (over production fo tears when not crying)
Blepharospasm (eyelid spasms)
