• 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

    • Record VA as the smallest line in which not more than 2 letters 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 Snellen VA

    • 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) 2^nd order neurons leave spinal cord ascending close to the apex of lung synapses at superior cervical ganglion 3^rd 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 3^rd 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 3^rd 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

  • Saccades

    • Rapid abrupt conjugate movement; stimulated by alternately fixating objects

    • Can be voluntary or reflex

  • Pursuits (Versions)

    • Slower smooth conjugate movements; stimulated by target movements

    • Used to test binocular, conjugate movements of the eyes allowing the lines of sight (LOS) to move in a parallel direction (or fixed angle)

  • EOM

    • Innervation

      • CN VI (abducens): LR

      • CN IV (trochlear): SO

      • CN III (oculomotor): MR, SR, IR, IO

    • Planes of action

      • LR and MR: horizontal plane

      • SR and IR: vertical plane, 23-25° temporal

      • SO and IO: vertical plane, 51-53° nasal

      • Muscle paresis is most obvious when the LOS is directed to move the eye in the direction of its primary action within its plane of action

    • Synergistic muscles: muscles in same eye that assist in an action

    • Antagonistic muscles: muscles in same eye that have opposite actions

    • Yoked muscles: neurologically paired in opposite eyes

      • Hering’s Law of Equal Innervation

  • Procedure

    • Remove spectacles and use high illumination

    • Fixation target held ~40 cm from patient’s eyes

    • Instruct patient to follow light as its moved in “H” pattern

      • Make sure you test to the extreme field of gaze (limit of the EOM)

    • Note any overactions (+) or underactions (-); perform ductions

    • Ductions are monocular eye movements into the 6 cardinal positions of gaze

      • Identifies the faulty muscle(s)

      • Can test each muscle in its field/plane of action

    • Parks 3-step used for hyper deviations to determine faulty muscle

    • Record EOM: full and smooth (F and S)

      • FROM: full range of motion

      • SAFE: smooth accurate full extent

** Also record if ductions=versions, etc**