• abnormal protrusion of globe 
• may be caused by retrobulbar lesions or less frequently shallow orbit
• direction can determine etiology

• mass pushing eyeball (tumors)
• systemic disease (thyroid disease)
• trauma (can cause enophthalmos as well)
• infections (esp. kids & young adults)
• other (cavernous sinus syndrome)

Acute dacryocystitis

(inflammation of nasolacrimal sac)

severe bilateral epiphora

(overflow of tears; excessive tear production)

(a) Left facial palsy and severe ectropion

(b) lagophthalmos

• Ambient light
• Level of retinal adaptation
• Level of arousal
• Excitement/startle dilates pupil
• Age of patient
• Older patients = smaller pupils
• Dilated pupils with high IOP / seizures

1. superior colliculus
2. pretectal nucleus
3. lateral geniculate body
4. edinger-westphal nucleus
5. sphincter pupillae
6. ciliary ganglioin
7. 3rd nerve

• normal eye stimulated: both pupils constrict
• when light swung to diseased eye: both pupils dilate instead of constricting

• 0.4 mm difference or more
• 20% of normal population
• difference less than 1.0 mm
• more apparent in dim light (than bright)

• ipsilateral ptosis, miosis, & anhydrosis
• dilation lag when light turned off abruptly
• light & near rxns intact
• apparent enophthalmos
• congenital Horner's patients demonstrate heterochromia

1. image quality
2. resolution
3. focusing error

• Most common & useful test for assessment of visual function
• Measure of resolving pwr of foveal area (or surrounding retina)
• Assessment of mpact of different conditions on visual function

VA

• normal VA ≠ normal vision
• VA = smallest black letter on white background that can be read @ 20 ft

• need for standards/conditions = test, distance, optotype (letters used)
• clinical practice = reliable & reproducible 

1. Minimum visible/detectable acuity (can you detect it?)
2. Minimum misalignment (can you locate its position?)
3. Minimum separable/resolvable (is there 1 or 2?)
4. Recognition acuity (can you identify/recognize it?)*******

• smallest detectable object
• ability to detect presence of objects w/o naming or resolving
• i.e. star in sky, telephone wire in sky
• as fine as 1 sec of arc (1/60 min; 1/3600 deg)
• rarely used or measured clinically

• smallest difference in position
• abilitiy to discriminate/localize small displacement of one part of obj w/ respect to other parts
• as fine as 3 sec of arc (1/20 min; 1/1200 deg)
• rarely used/measured clinically; hyperacuity

• smallest difference in position 
• Vernier acuity-discrimination of lateral misalignment in frontal plane that provides basis for measurements; keratometers & lensometers
• also stereo acuity

• smallest resolvable separation 
• ability to resolve 2 or more spatially separated targets
• threshold = 30 CPD; used clinically
• gratings (eq. spaced b&w lines) or landolt C are examples

• smallest recognizable letter or object
• aka minimum legible 
• requires resolving obj, letter, #, form details
• threshold = 30 sec to 1 minute arc
• most common clinical test

• snellen chart
• landolt C
• tumbling E

• Standard Optotypes
• Scaling
• Spacing
• Same number of optotypes/row
• Background luminance
• Ambient luminance
• Optotype contrast

• Use of Sloan letters (C D K H N Z R S V O)
• Specification of acuity: MAR/logMAR
• Horizontal spacing: Eq. to optotype size
• Vertical spacing: Eq. to size of preceding line & Steps of 0.1 log Units
• # of optotypes: same number / row
• Contrast: > 85% Background
• Luminance: From 100 to 300 cd/m²

• letter height of 20/20 letter
• tanθ = h/distance --> h = distance(tanθ)

h = (tan 1’) 6 m

= (tan 0.01667) 6

= 6 (0.000291)

= 0.001745 m

= 1.745 mm gap or stroke width

Letter height = 5 x 1.745 = 8.73 mm

• when it subtended 5 minutes of arc
• test distance / distance @ which smallest letter read subtends 5 min arc

MAR = angular size of the gap of the smallest letters that pt can identify 

(the letter detail; 1/5 of letter height)

• dif. # of optotypes per row
• irregular progression in letter size
• dif. in optotypes --> recognition difficulty
• dif. in background luminance related to dif. chart manufacturers

• constant # letters per row (5 letters/line)
• constant logarithmic change in letter size
• space b/n letters = letter width
• scoring typically by letter

• low vision chart
• #s @ bottom of pgs refer to letter size in ft
• # represents distance @ which particular letter would subtend 5 min from top 2 bottom
• testing distance (ft) / # of letter that patient can just make out

• used for measurement of reading acuity, not single letter acuity
• used for functional assessment w/ trial frame after subjective refraction

What are other common optotypes to test VA?

• early treatment of diabetic retinoscopy study
• Allen pictures
• LEA symbols
• tumbling E
• landolt C

• luminance = [illuminance x reflection factor (usually 0.8)]
• minimum luminance = 10 ft-lamberts
• illuminance = (luminance flux incident on surface/unit area)
• minimum luminance = 12-20 ft-candles

• luminance & illuminance
• contrast of chart (letter contrast ≥ 0.85; little effect b/n 20-100%; not a clinical factor; most wall/projectors meet specifications)
• optical properties of the eye (RE or state of Rx; optical aberrations; clarity of media)

• eccentricity (retinal location)
• pupil size
• accommodation
• age
• Stiles-Crawford effect of the 1st kind
• binocularity
• fixation
• tear film/anterior ocular health

• VA is higest @ fovea - dec w/ increasing eccentricity
• 10 deg. from fovea = 20/100
• 20 deg. from fovea = 20/200
• due to neural connectivity retinal summation areas & # of rods or cones/ganglion cells

• dec. pupil size --> dec. retinal illumination, inc. depth of focus, & dec. diameter of blur circles
• as pupil size dec., VA increases (to a limit)
• <2.5 mm = VA dec due to diffraction
• >5 mm = VA dec due to spherical abberation

• poor/inappropriate accommodation --> defocus decreases VA
• infants develop 20/20 by 6 months & dec w/ inc age
• inc light scatter, dec ocular transmission, inc pupil rigidity & miosis, dec accommodation, dec # of cones

• Light rays striking the PR at oblique angles are not as efficient as those parallel to the PR axis (entering through pupil center > peripheral)
• directional sensitivity of the receptors

• binocular VA: 5-10% better than monocular (summation)
• fixation: slow drifts, high-freq tremors, saccadic re-fixations
• tear film/anterior ocular health: can dec VA

• past experience/memory/learning effects (blur interpretation)
• expectations (call letter for # @ end of line)
• motivation (refuse to guess, embarrassed)

• inc. illumination --> dec pupil --> falsely high VA
• decreases chart contrast w/ inc light

1. walk patient toward chart or bring chart to patient
2. count fingers/hand motion
3. light perception with projection (LP c proj)
4. light perception w/o projection (LP s proj)
5. No light perception (NLP)

• when VA is 20/30 or worse at distance AND near
• PH testing is conducted at distance only

• VA inc. w/ PH: uncorrected RE, corneal or lenticular abnormalities (dystrophies, irregular astigmatism)
• VA inc. but < normal: high RE and/or amblyopia
• VA stays same/dec w/ PH: not RE; organic or pathological problem

• PH nullifies small amts of RE by inc. DOF by dec. diameter of blur circles on retina
• dec. light scatter --> dec. aberrations
• most effective PH diameter = 1.32 mm

• illumination (target, retinal, & room)
• spectacle correction 
• distance b/n PH & cornea (moving PH closer inc. retinal illumination & inc. FOV)

• magnifier (presbyope hold target near)
• optical irregularities (PH held @ anterior focal point, irregularities seen as shadows cast on retina)
• gross refraction (ametropia; move PH away & dist obj smaller = myopic; move PH away & obj larger = hyperopic)
• check for final correction (fully corrected if PH placed over final Rx & no change/reduction of VA)
• therapeutic device (PH CLs)

VA measurement pearls: What condition would you suspect for the following situations?

1. pt missing several letters on each line
2. pt trouble localizing; isolated line/full chart
3. pt difficulty w/ first few letters
4. pt difficulty advancing to next letter on next line (skips line)

1. suspect uncorrected astigmastism or amblyopia
2. suspect amblyopia
3. suspect left hemianopia
4. suspect right hemianopia

What are other options besides Snellen letters to test VA in the following situations?

1. pt doesn't read letters
2. preschooler/illiterate pt
3. additional options to obtain VA

1. snellen numbers
2. tumbling E, picture optotypes. HOTV
3. FPL, OKN drum, Visual Evoked response

Predicting RE from VA: For the following distance VAs, give the spherical myopic error:

1. 20/15
2. 20/20
3. 20/25
4. 20/30
5. 20/40
6. 20/50 ....
7. 20/100
8. 20/200

1. 20/15 = plano sph
2. 20/20 = -0.12 sph
3. 20/25 = -0.25 sph
4. 20/30 = -0.50 sph
5. 20/40 = -0.75 sph
6. 20/50  = -1.00 sph
7. 20/100 = -2.00 sph
8. 20/200 = -2.50 sph

• when patient's best corrected VA in their better eye is 20/200 or worse
• maximum diameter of VF in the eye w/ larger field does not exceed 20 degrees

Vs OD 20/20  V’s OD 20/20

     OS 20/20        OS 20/20

Refractive Error possibilities?

OD: ___________ OS: __________

If you know your patient has glasses that they wear for reading only, your best refractive error estimate would be?

Vs OD 20/20  V’s OD 20/20

     OS 20/20        OS 20/20

Refractive Error possibilities?

OD: E or mild H OS: E or mild H

(able to accommodate through low RE)

If you know your patient has glasses that they wear for reading only, your best refractive error estimate would be? hyperopia; need + lenses, esp. @ near

Vs OD 20/40  V’s OD 20/20

     OS 20/25        OS 20/25

Refractive Error possibilities?

OD: ___________ OS: __________

Vs OD 20/40  V’s OD 20/20

     OS 20/25        OS 20/25

Refractive Error possibilities?

OD: -0.75 myope OS: astigmatism

Vs OD 5/400 PH 20/25

OS 20/400 PH 20/25

V's OD 20/200 @ 20 cm

OS 20/200

Refractive Error possibilities?

OD: ___________ OS: __________

Refractive Error possibilities?

OD: > -2.50 M OS: > -2.50 M

high myopia --> still can't see 20/20 @ 40 cm so need to move closer; e.g. 5D myope

Vs OD 20/40  V’s OD 20/30

     OS 20/25        OS 20/20

Refractive Error possibilities?

OD: ___________ OS: __________

Refractive Error possibilities?

OD: Astigmatism OS: -0.25 M

Astigmatism b/c VA improved but still not 20/20; probably some myopia too; 20/25 = -0.25

manifest eye turn = ?

latent eye turn = ?

manifest eye turn = tropia

latent eye turn = phoria

Name the tropias:

1. eye turned in
2. eye turned out
3. eye turned down
4. eye turned up
5. eye turned rotational 

1. ESOtropia
2. EXOtropia
3. HYPERtropia
4. HYPOtropia
5. CYCLOtropia

• four rect: medial, lateral, superior, inferior
• two obl: superior & inferior

What cranial nerves supply the following EOMs?

1. MR, SR, IR, & IO
2. LR
3. SO

1. CN III
2. CN VI
3. CN IV

What ocular movements are each EOM responsible for?

1. MR
2. LR
3. SR
4. IR
5. SO
6. IO

1. MR = Adduction; move eye towards nose
2. LR = Abduction; move eye away from nose
3. SR = elevation
4. IR = depression
5. SO = intorsion; move top of eye towards nose
6. IO = extorsion; move top of eye away from nose

• Duction = movements of one eye
• all EOM movements can be ductions (adduction, abduction, elevation, depression, intorsion, extorsion)

• Versions = movement of both eyes together
• conjugate movements that can be corretional movements for head tilts (1 eye intorts, other extorts)
• dextro, levo, dextro-elevation, dextro-depression, levo-elevation, levo-depression

• Vergence = both eyes; disjugate movements
• convergence = both eyes move towards nose
• divergence = both eyes move away from nose

1. support high resolution of foveal vision 
2. prevent neural blur of images due to retinal image motion

1. Visual fixation (VF)
2. Vestibulo-ocular reflec (VOR)
3. optokinetic nystagmus (ON)
4. saccades (S)
5. pursuits (P)
6. vergences (V)

Center of rotation of the eye is about 13mm behind the cornea (antr vitreous)

slight inaccuracies in measuring eye movements due to center of rotation location

• fixation axis perpendicular to plane of face
• eye is in primary gaze
• all other gazes are eccentric

• fastest movement = saccades
• 700 degrees per second
• saccades move objects to fovea by sudden shift in direction of gaze

• conjugate eye movement
• rotate eyes equally & in same direction
• can be reflexive

• smooth pursuit movements
• conjugate; relatively slow moving targets are kept on retina (40 deg/sec)
• smooth rotations of eye, rather than sudden movements
• partly attentive; partly reflexive

• Vergence eye movements
• disjugate; convergence or divergence
• lower peak velocity (70 deg/sec) compared to saccades
• shift off-foveal images to fovea by suddenly changing the distance of gaze

• Vestibular movements stimulated by head motion & its effect on the inner ear vestibular apparatus
• purely reflexive movements
• has very short latency (16 milliseconds)

• movement that supports stable retinal imagery
• smooth & slow motion in direction of motion of target
• fast saccade-like motion in the opposite side

• equal innervation to yoke muscles
• one motor command split & sent to both eyes
• hering proposed that vergences are also yoked w/ respect to innervation
• e.g. right lateral rectus & left medial rectus 

1. tonic
2. proximal
3. accomodative
4. fusional 

accommodative convergence to accomodation ratio

(how many prisms of convergence for every diopter of accommodation?)

• tonic innervation provides the physiological resting position of the eyes
• varies with drugs, age, alcohol, stress, environment
• lost upon death; eyes diverge at that time (also lost with anesthesia)

• induced by awareness of near
• convergence innervation when a near object is viewed

• convergence, accommodation, & constriction of pupil 
• very important measure in certain cases of strabismus 
• must measure accommodative component of eye turns

• the flexible & powerful component of convergence that alters vergence of the eyes to achieve fusion
• adds convergence when other 3 components do not provide enough
• can also help diverge if other 3 overact
• measure "break" with prisms

• NPC - is target single?
• accommodation - is target clear?

• tests ability to converge & keep images fused
• move accommodative target close to pt until diplopia is reported or one eye loses fixation (eye turn)
• record breakage & recovery

• anyone can get eye turns (strabismus)
• eso common in kids (newborn - 5yrs); kids w/ eye turn need referral to opt. bc chance for amblyopia (lazy eye)
• exo more common in adults; sudden onset strabismus needs referral to neuro (in case of diabetic CN III palsy)

• both eyes open; pt fixates penlight
• compare the position of corneal reflex in both eyes
• reflex should be @ same position OU
• in strabismus: one eye will show a dif. position for corneal reflex
• 1.0 mm = 22 prism diopter deviation (loose prisms used to compensate for deviation)

• amount of loose prism required to bring both corneal reflexes @ same spot
• both Hirschberg & Krimsky less accurate than cover test but useful in kids/adults who can't do cover test

1. unilateral performed first - heterophoria/tropia
2. alternating - magnitude & direction

both performed @ D & N using fixation targets

• magnitude & direction that the visual axes of the eyes drift --> when fusion is disrupted (dissociated)
• magnitude reveals amt of fusional vergence needed to secure single binocular vision

• potential for amblyopia
• cosmesis
• poor binocular fxn
• asthenopia/HA
• dec stereopsis (depth perception)

1. to determine tendency of eyes to deviate from point of fixation & whether or not manifestation of possible muscle imbalance
2. lenses/prisms prescribed to achieve visual comfort for pt w/ limited vergence compensation

• diplopia
• amblyopia: lazy eye
• suppression: active cortical dampening of images from one eye

• reduction in best corrected VA (not organic etiology)
• strabismus eye turn 
• suppresion (refractive amblyopia)

• not a true part of cover test
• pt sees obj move in same direction as paddle = EXO
• pt sees obj move opp direction as paddle = ESO

• esotropes have uncrossed diplopia (OD image on right, OS on left; diplopic image occurs on same side as deviating eye)
• exotropes have crossed diplopia (OD image on left, OS on right; diplopic image occurs on side opp of deviating eye)

1. suppression
2. anomalous retinal correspondence

perception of depth produced by binocular retinal disparity; fundamental test of binocularity

• 1st deg: simultaneous perception
• 2nd deg: flat fusion (2D)
• 3rd deg: stereopsis (highest level)

monocular

• interposition/overlap
• relative size
• light & shade

binocular

• stimulation of corresponding foveal points
• retinal disparity

global

-requires bifoveation

-no monocular cues

-not present w/ constant strabismus

-ex: random dot shapes/forms

local

-includes monocular cues

-up to 70 sec arc even w/ constant strabismus

-ex: Wirt circles, lea symbols, & stereofly

• blur
• uncorrected RE
• reduced contrast
• strabismus
• aniseikonia
• suppression

• force of blood against walls of vessel
• saves lives, may be the only doctor pt sees

• HTN is elevated BP over time; most common primary diagnosis in U.S. (35 million off. visit)
• risk to body: hrt dz, kidney dz, stroke, congestive hrt failure, atherosclerosis (hardening of arteries), coronary & carotid artery disease
• risk to eye: hypertensive retinopathy, choroidopathy, optic neuropathy, blindness

Systolic BP & Diastolic BP values for the following BP classifications:

1. normal
2. prehypertension
3. stage 1 hypertension
4. stage 2 hypertension

1. SBP= <120; DBP = <80
2. SBP = 120-139; DBP = 80-89
3. SBP = 140-159; DBP = 90-99
4. SBP= ≥160; DBP = ≥100

• hypertension = <140/90
• DM/kidney dz=<130/80

• refractive = keratometer uses reflective properties of cornea to measure its radius of curvature
• reflexive = K acts as highly convex spherical mirror

• radius of curvature in each principal meridian found by measuring size of reflected mires
• measures only 2 small areas on cornea surface

• Helmholtz invented modern keratometer (1854)
• Javal & Schiotz developed clinical instrument (1881)

• mires are not distorted & principal meridians are perpendicular
• with the rule (more pwr in vertical; greatest curvature; vertical b/n 60-120); against the rule (more pwr in horizontal b/n 30-150); & oblique (prin. meridians lie b/n 30-60 or 120-150)

• distorted mires or principal meridians not perpendicular

1. keratometry - corneal curvature/astigmatism
2. retinoscopy - spherical ametropia/astigmatism

• only samples central 3 mm
• does not quantify irregular astigmatism
• adjustment errors not uncommo 
• error of about ± 0.25 to 0.92 D

horizontal = primary

vertical = secondary

Corneas flatter than 42.00generally indicate _________________.

Corneas steeper than 44.00 generally indicate _________________.

flatter than 42.00 = hyperopia

steeper than 44.00 = myopia

1. screening 
2. qualitative/diagnostic
3. quantitative

screening can be automated or confrontation fields; performed on all pts w/o expectation of particular field defect

• suprathreshold automated perimeter
• suspect "problem" & do quick test to rule out problem

• suspect a defect in pt
• determine characteristics of VF defect such as location, borders, shape, size, whether its homonymous
• lesion can be localized/cause identified
• often tests several points on VF & needs quantification 
• screenings can be diagnostic

• quantify a known or suspected field defect in order to get baseline data as well as follow-up the defect over time
• used to identify subtle defects
• expensive for pt
• GLC most commonly followed/diagnosed w/ quantitative perimetry

• test stimulus placed in area where it is not seen (outside VF or inside blind spot) then move stimulus until just seen
• stimulus moved in all directions

• stimulus presented at chosen location; threshold or suprathreshold
• determine sensitivity of one location

1. finger count
2. field-limits
3. color confrontations (red-cap)

all done at 1 m distance

1. accommodation
2. convergence
3. pupil constriction

• Causes blur and eye strain with near work
• Usually reported between ages 40-45
• Onset from 38-48 years of age

• Lens changes in shape, therefore changes in power
• Objects at various distances can now be focused on the retina
• Some animals have different mechanisms of accommodation

1. blur sensory input
2. inc freq. of firing of neurons that supply ciliary muscle
3. ciliary muscle constricts
4. lens zonule relaxes
5. lens becomes more spherical
6. overall lens pwr inc.

• Reflex accommodation
• Vergence accommodation
• Proximal accommodation
• Tonic accommodation

• Automatic adjustment of refractive state to maintain a sharp focused image in response to blur or decrease in contrast
• Usually occurs for small amounts of blur, up to TWO DIOPTERS
• Largest component of accommodation in monocular and binocular viewing

• Accommodation induced by neurological linking and action of fusional (disparity) vergence
• Gives the CA/C ratio, which is 0.40D per meter angle in young adults
• Second major component of accommodation

• Accommodation due to the knowledge of perceived nearness of an object
• Stimulated by targets closer than 3meters

• Revealed in the absence of blur/ proximity/vergence cues
• Represents baseline innervation from midbrain and is thus a stable input

• Ranges between 3-5 Diopters in children around age 6 years
• 4-7 diopters in age 12 years
• Follows adult ranges after 12 years of age

Push-up method; Donder's Amplitude of accommodation

• Measures diopters pt’s ability to change focus of lens in response to accommodative target
• while wearing distant Rx pt must keep target clear & report 1st sustained blur

Expected Mean amplitude =

18.5 D – [0.30D x (age in years)]

• Enhance visual capability
• Improved speed and accuracy (esp. in low contrast situations)
• Binocular visual field is larger (2000); Monocular 60 up, 60 medial, 70 down, 100 temporal

binocular parallax & elicits convergence

also fine vs. coarse stereo (fine is foveal; coarse is off-foveal)

• Random dot stereograms
• Visual system performs significant interocular image fusion

• Foveal stereo threshold can be as low as 2 seconds of an arc
• hyperacuity = when observer performs better than expected based on foveal cone diameter

• refractive (strong eye)
• axial (long eye)
• parallel light focuses in front of retina

• refractive (weak eye)
• axial (short eye)
• parallel light focuses behind retina

• hereditary, environmental (near work), premature birth
• distance blur, asthenopia/blur at near
• squinting, push specs up nose
• corrected w/ minus lens 

symptoms

-asthenopia w/ near work

-child who is disinterested in school

-eye rubbing, red eyes

signs

-reduced amplitude accom, esp. for young ppl

-higher H > inc. need for accom., ET 

• fully correct: if pt is ET or vocational needs (near point demands)
• partially correct: younger pts, vocational needs (mainly distnace work), pt is exo