Preliminary Testing

Visual Acuity

Purposes:
To establish a baseline
Legal reasons (driver’s licenses, insurance claim, pension, and disability based on legal blindness)
Legal blindness: 20/200 or worse in better eye OR less than 30 of visual field in the widest meridian of the better eye
Monitor progression or improvement of eye disease
Guide for the rest of the exam (prediction of refractive error, correlation of data, determines additional testing)
Always the first test performed after history
Exception: chemical burn/spill; irrigate first, then check VA
Definition: the resolving power of the eye, or the ability to see two objects as separate
“Normal” resolving power is defined as the ability to detect a gap with a width of 1 min of arc
VA is highest at the fovea and decreases with increasing retinal eccentricity
VA best if pupil is 2-5 mm
Types
Minimum Detectable Resolution (minimum visible): the ability to distinguish an object from its background
Minimum Separable Resolution (minimum resolvable): the ability to resolve two or more spatially separated targets
Gratings, bars, Vernier acuity, preferential looking
Recognition Resolution (minimum legible): the ability to recognize letters, numbers, and geometric forms
Snellen, Landolt C, Tumbling E
Snellen acuity chart is the universal method of measuring VA
Snellen optotypes: width of each stroke is equal to the width of a gap on that line
“Best” letter is E (3 strokes and 2 gaps)
“Not as good” letters are T and L ( no gaps)
At 20 feet, a 20 foot optotype subtends 5 min of arc
Its details each subtend 1 min of arc
20/20 letter is defined as a letter that has a height (x) such that it subtends 5’ arc at 20 ft
Letter height can be altered with test distance
Details (gaps and strokes) each subtend 1’ arc at 20 ft
Utilizes a “folded” room/operatory system
Projector with letters, 2 mirrors and a screen
Test distance= patient to mirror + mirror to screen
MAR (minimum angle of resolution) in minutes of arc is equal to the reciprocal of the decimal acuity value or the Snellen fraction
Snellen fraction = 1/MAR
20 ft (6m) is considered optical infinity, which is defined as the distance at which no accommodation is being used
Snellen fraction = testing distance

distance at which the smallest letter read subtends an angle of 5’ of arc

Also described as the distance at which a “normal” eye can see the smallest letter read by this patient

Snellen equivalent is used when VA is taken at a distance other than 20 ft or when other nomenclature is used
It is better to report the actual acuity, not the equivalent
Limitations:
Number of letters tested per line changes as you move down
Letter sizes between lines do not change by a constant ratio
Between row and between letter spacing is not proportional to the letter size
Legibility for optotypes often varies
Standard Chart Specifications
Chart luminance: at least 10 foot lamberts
Chart contrast: at least 90%
Subdued room illumination to enhance chart contrast
Uncorrected refractive error is more likely to impact VA when pupils are slightly dilated
Distance VA should be performed during ALL patient encounters
Procedure
Seat patient comfortably and dim lighting
VAs taken without correction(sc) and then with correction(cc)
Minimizes chance of patient memorizing
Clean occluder with alcohol swab
Begin with full chart open and ask “Which of these is the smallest line of letters that you can read?”
Isolate smallest LOL that the patient can read; continue to scroll down to the next LOL and have patient read it; stop when the patient is unable to read the entire LOL
Find the patient’s threshold
OBSERVE the patient (no squinting, cheating, leaning forward, etc)
Observe the speed and degree of difficulty
RecordVA as the smallest line in which not more than 2letters were missed for OD, OS, OU
The number at the end of each line signifies the level of acuity
Some use several 20/20 lines to minimize memorization
“normal” best-corrected VA is 20/20
Corrected visual acuity (best corrected VA) is measured with the best refractive correction in place
Habitual visual acuity is measured with patient’s own spectacles/CLs
Near VA performed during full/comprehensive exam and if they have a near vision complaint
Procedure
Use full illumination: stand lamp on recording card
Done without, then with near correction
Measure the distance from the patient’s spectacle plane to the reading card in cm
Cover OS and instruct to “Read the smallest paragraph that you are able to”, switch to cover OD, and then remove to read with both eyes open
Re-measure the working distance with their correction
Record working distance (in meters!) over the smallest print read for OD, OS, OU
M system: a 1M letter subtends 5’ of arc at 1 meter
Allows patient to hold card at their desired reading distance
Reduced Snellen system: gives the appearance of expressing the distance VA that is equivalent to the near VA
Should NOT be used for near VA (not appropriate to use a term that suggests a test at 20 ft when that distance is not relevant to near vision)
Jaeger system: indicates the size of the print by the letter J followed by a number
Poor system because there is no standardization of the Jaeger sizes and there is no intrinsic meaning to the “J” number
Pinhole testing: a measure of potential visual acuity
Nullifies small amounts of refractive error by 1) increasing the depth of focus and 2) decreasing the size of the blur circles
Most effective diameter is 1.32 mm
If VA improves with pinhole, suggests that refractive error is probably the cause of the reduced VA
Done when entering acuities are 20/40 or worse (based on better VA)
Record PH followed by VA obtained
If no improvement, record PHNI
Super Pinhole, PAM (potential acuity measure) and laser interferometer are commonly used to determine potential VA before cataract surgery
Brightness Acuity Test (BAT): used when you suspect acuity would be worse in a glare situation
VA with BAT is worse than without BAT for patients who have glare problems
Alternative distance VA charts
OKN drum: cortical function only; objective test
Teller acuity cards: infants, non-responsive patients
Tumbling E: preschool, illiterate or non-verbal patients
LEA chart: children
Allen figures: children
Landolt C:
HOTV chart: amblyopes
Each letter is surrounded by crowding bars
Amblyopia: decreased VA (not correctable to 20/20) NOT due to pathology
Snellen chart produces contour interactions (slow responses, some correct responses over a wide range of letter sizes, correct end-letter responses, out of order responses, perform better with isolated lines or letters)
Feinbloom chart: patients unable to see the 20/400 E on Snellen
Full illumination and test distance of 5 or 7 ft
Record test distance over smallest number size seen
Alternative near VA charts (used during low vision)
Bailey-Love Chart: patients unable to see large print on other cards
Space between the letters is equal to the letter width (prevents crowding effect)
5 letters on each line
Between row spacing is equal to the height of the letters in the smaller row
Lighthouse cards
Other measures of VA
Light perception (performed at ~ 1 ft)
LPP: light perception with projection
LPO: light perception only
NLP: no light perception
Hand motion (used as last ditch effort when Feinbloom efforts exhausted)
Count Fingers
“Fix and follow”: unresponsive patients
MUST ALWAYS ATTEMPT TAKING VISUAL ACUITIES
Correlation of VA and refractive error
General rule: each 0.25DS of uncorrected refractive error accounts for ~ 1 line of SnellenVA
For cylinder, take spherical equivalent (sphere + ½ cyl)
For oblique axis, add a line for the axis
Patient must have NO accommodation or be cyclopleged

Pupil Testing

Pupil performs 3 primary functions
Controls entering light
Modifies depth of focus (inverse relationship)
Smaller pupil increases depth of focus
Varies optical aberrations (smaller has less aberrations)
Should be performed during ANY patient encounter regarding eye health
Important because it is a neurological test that can detect optic nerve disease, brain mass and aneurysm
Gross examination can detect iris abnormalities, media opacities, and leukocoria
Shape
Pupils should round and centered within the iris on optic axis
Irides should be of the same color
Abnormalities
Corectopia: displaced or misshapen pupil
Ectopic pupil: significantly decentered
Polycoria: more than one pupil
Heterochromia: iris color different between eyes or between different areas in one eye
Aniridia: absence of iris, therefore non-existent pupil
Size
Average of 3.5 mm in adults under normal illumination
Become smaller after adolescence due to senile miosis
Should equal one another within 1 mm
Anisocoria: unequal pupil size
20 % have physiologic anisocoria
Controlled by the autonomic nervous system
Iris dilator muscle dilates; sympathetic innervation
Iris sphincter muscle constricts; parasympathetic innervation
Pupillary pathways
Afferent
Light enters pupil impulse in retina (PR and ganglion cells) optic nerve optic chiasm: ½ cross, ½ ipsilateraloptic tracts to superior colliculi pretectal nuclei of hypothalamus crossed and uncrossed fibers to EW synapse with efferent fibers
Parasympathetic efferent
From EW nucleus travels with CN III (inferior division) cavernous sinus pierces globe deviates from CN III and synapses at ciliary ganglion postganglionic fibers reach iris sphincter via short ciliary nerves
97 % of the fibers control accommodation (ciliary body)
Only 3 % innervate the sphincter
Sympathetic efferent
Hypothalamus synapses at ciliospinal center of Budge (C8-T4) 2nd order neurons leave spinal cord ascending close to the apex of lung synapses at superior cervical ganglion 3rd order neurons follow the ICA’s to the globe iris dilator via the long ciliary nerves
Sympathetic innervation reaches Muller’s muscle in upper lids
Response to light
Miosis (=constriction) occurs via parasympathetic innervation
Some latency in initial constriction is normal (depends on brightness and age)
Direct response: response that occurs in one eye while the light is shone in that eye
Consensual response: response that occurs in one eye while the light is shone in the other eye
Pupillary escape: gradual and partial re-dilation without change in light intensity
Pupillary unrest or hippus: small oscillations in pupillary diameter that occur during maintained stimulation
Due to normal fluctuation in sym/parasym equilibrium
Response to near
Independent of retinal illumination
Near reflex is ALWAYS present when direct light reflex is intact
Near triad: pupil constriction, convergence, accommodation
Swinging flashlight test
Compares the strength of the direct pupillary response with that of the consensual response
Detects afferent pupillary defect due to retinal abnormalities or optic nerve pathway anterior to LGN (APD or RAPD)
Procedure
Remove spectacles and examiner positioned off to one side
Use a distant, non-accommodative target (2-3 lines above VA)
Measure pupil size under normal lighting conditions
Expected findings: should equal one another
Size in bright: 2-4mm Size in dark: 4-8mm
If pupils are unequal, measure size in both dark and bright light
To visualize dark irides, use:
Burton lamp: hold ~25 cm (10in) from the patients and below the patient’s line of sight
Ophthalmoscope: use as a dim flashlight to illuminate both eyes simultaneously (“light from below”)
Judge the roundness of each pupil and describe any abnormalities
Observe pupil’s response to light in dim illumination
Note the magnitude of change (quantity) using scale 0-3
Note the rapidity of reaction (quality) using slow (-) or fast (+)
Expected findings
Direct response of OD should equal direct response of OS
Consensual response of OD should equal consensual response of OS
Direct response of OD should equal consensual response of OD
Perform the swinging flashlight test
Expected findings
Rate and amount of constriction should be the same for both pupils
Direct should equal consensual for both eyes
If it is not the case for either eye: afferent pupillary defect in the eye with less constriction
Record using PERRLA (-) APD if all reflexes are normal
PE: pupils equal
R: round
RL: reactive to light (direct and consensual)
A: responsive to accommodation
(-) APD: no APD
Afferent pupil anomalies result in an APD
Severe retinal disease, optic nerve diseases or compromise, mass/lesion behind eye compressing optic nerve or chiasm
NOT with disorders of ocular media
Afferent pupillary defect (RAPD) indicates unilateral or asymmetric damage to the anterior visual pathways
When the consensual response is greater than the direct response of one eye
If present, pupils of both eyes will constrict less when the light is directed into the affected eye
Both eyes will constrict when light beam directed into unaffected eye
When light beam is directed in affected eye, causes less constriction in
Affected eye: reduced direct reflex
Unaffected eye: reduced consensual reflex
Graded from trace to 4+
3-4+APD: immediate dilation of the pupil, instead of initial/equal constriction
1-2+APD: no change in pupil size immediately, followed by dilation
Trace APD: initial constriction, but greater escape to a larger intermediate size than when light is swung back to normal eye
Amaurotic Pupil: severe or 4+APD
Patients have an eye with “NLP”
Light beam directed into affected eye no direct response in affected eye and no consensual response in unaffected
Light beam directed into unaffected eye direct response in unaffected eye and consensual response in affected eye
Near reflexes will be intact
Reverse (indirect) APD
Performed when one pupil is fixed, dilated, or constricted
ONLY observe the reactive pupil
If APD in eye with reactive pupil, that pupil will constrict more with consensual stimulation than with direct
If APD in eye with fixed pupil, the reactive pupil will constrict more with direct stimulation than with consensual
Note reverse APD (implies you used a reverse technique)
Efferent pupil anomalies: unilateral defects/lesions will often generate anisocoria
Anisocoria: usually 2-4 mm difference in dark and light
If same degree of anisocoria in light and dark: physiologic
Big pupil problems: anisocoria greater under bright conditions due to a defect/lesion of the parasympathetic
Adie’s tonic pupil
Relatively common; primarily in females 20-40
Presentation
Unilateral semi-dilated pupil
Pupil with minimal and slow reaction to light
Pupil with reduced direct, consensual (poor constriction of sphincter) and near responses to light
May present with a reduced near vision complaint
Vermiform motion of iris: quivering motion of iris at pupillary border due to segmental palsy of sphincter
10-20% eventually affecting other eye
Reduced direct response to light bilaterally
Decreased near VA
Prolonged pupil cycle time
Etiology
Lesion of the parasympathetic pathway (ciliary ganglion) on the side of the pupil problem
Viral
Diagnosis
0.125% pilocarpine (wait 10-15 min)
Constriction: Adie’s confirmed
No constriction: either pharmacologic or 3rd nerve
Management
Rule other orbital and ocular conditions
Cosmesis
Accommodation
Near add, sometimes unequal adds
Equalize accommodation during refraction and other near or binocular testing
Accommodation generally returns within 2 yrs
Cranial Nerve Palsy
Presentation
EOM paresis—exotropia and hypertropia (“down and out”) of eye affected
Ptosis
Fixed and dilated pupil, or non-reactive pupil
Etiology
Pupil fibers are on the outside of CN III; they are involved early in a compressive lesion and are rarely involved in an ischemic infarction
Lesions that involve the pupil: tumor and aneurysm
Lesions that spare the pupil: vascular disease causing ischemia (diabetes, hypertension)
Diagnosis
0.125% pilocarpine—will NOT constrict
1% pilocarpine—WILL constrict
Management
Presentation of acute 3rd nerve palsy with pupil involvement considered a medical emergency!
Manage diplopia and systemic cause of palsy
Pharmacologic anisocoria: dilation of one eye
Presentation
Usually unilateral, fixed and dilated pupil
Anticholinergic substances block the action of acetylcholine on the ciliary muscle and cause mydriasis
Etiology
Scopolamine
Jimsonweed
Antihistamine drops
Atropine, homatropine, cyclopentalate
Diagnosis
0.125% pilocarpine—Will NOT constrict
1% pilocarpine—Will NOT constrict
Management
Reassurance and patient education
Little pupil problems: anisocoria is greater in dim conditions due to a defect/lesion to the sympathetic nervous system
Horner’s syndrome
Presentation
Miosis (can be mild: less than 1 mm of anisocoria)
Ptosis
Anhydrosis

***All on the same side as the lesion***

Etiology
Interruption of the sympathetic system anywhere in its path
Congenital Horner’s: idiopathic or trauma at birth
Heterochromia and anhydrosis
Central lesions: stroke, MS, spinal cord cancer, neck trauma
Preganglionic lesions: pancoast tumor, trauma, thyroid enlargement or lesion
Postganglionic lesions: extracranial or intracranial cause (Raeder’s, ICA dissection, complicated otitis media)
Diagnosis
Look at old photographs
History of trauma, endardectomy, thyroidectomy?
Dilation lag test
Take picture immediately after turning off lights and take another picture 15 seconds
Horner’s pupil has a dilation lag in the dark of ~15 sec
0.5% Apraclonidine (Iopidine) (wait 15-30 min)
Dilates: confirms diagnosis of Horner’s
10% Cocaine drop in affected pupil (wait 15 min)
Does NOT dilate: confirms diagnosis of Horner’s
Management
Important to determine before or after the bifurcation of the carotid artery
Differentiate by testing for anhydrosis (prism bar test and corn starch under heat lamp)
Postganglionic lesions generally do not cause anhydrosis
1 % hydroxyamphetamine (done 48 hrs after cocaine test)
Dilation: central or preganglionic lesion
No dilation: postganglionic (“fail safe” affected pupil fails to dilate)

Argyll-Robertson pupil
Presentation
Bilaterally miotic, irregular pupils
Difficult to dilate
Direct and consensual responses absent or sluggish in affected eye(s)
DOES react to near (there is light-near dissociation)
Etiology
Midbrain lesion
Neurosyphilis or neuropathy from diabetes, alcoholism
Pharmacologic anisocoria: constriction of one eye
Cholinergic agents: pilocarpine (glaucoma drop) and physostigmine

Near-Light Dissociation: pupils fail to respond to light, but near response intact
Afferent pathways interrupted, efferent pathways intact
Examples of conditions that manifest near-light dissociation
Neurosyphilis: Argyll-Robertson pupil
APD or amaurotic pupil
Aberrant regenerations
Pupil Irregularities
Aniridia: congenital absence of the iris (usually bilateral)
Iris coloboma (“keyhole” pupil)
Usually involves the inferior nasal portion of the iris
Wider at the pupillary margin than at the iris root
Corectopia: displaced pupil (frequently bilateral)
May be displaced in any direction
Iridectomy: surgically created sector cut of the iris
Iris atrophy
From age, inflammation, ischemia, trauma
Iris holes may form creating polycoria
May be sectoral (herpes zoster) or widespread
Iris cysts/tumors
If extensive enough, may distort pupillary margins
Laser iridotomy: hole created in iris usually located superiorly at 10:00 or 12:00
Shape of the pupil usually not affected
Persistent pupillary membrane (PPM): persistent embryolic structure
Rarely affects pupillary movement
Trauma
Tears of pupillary margin and sphincter
Traumatic mydriasis and abnormal pupil light reflexes permanent
Iridodialysis
Tear at the iris root; D-shaped pupil
Monocular diplopia may occur
Posterior synechia: attachment of iris to anterior lens surface from active or history of anterior uveitis or intraocular inflammation
Iridonesis: quivering of the iris
Pupillary margins are irregular and reactivity will be reduced
Seen in aphakic patients
Pharmacologic dilation (bilateral)
Anticholinergics
Antihistamines
CNS depressants
Sympathomimetis and CNS stimulants (bind with alpha receptors on dilator muscle to cause mydriasis)
Epinephrine, Cocaine, amphetamines
Pharmacologic constriction (bilateral)
Barbituates
Opioids
Levodopa
Marijuana
Vitamin A

EOM Testing