Classification of Findings Flashcards
Size and shape
2.1mm2 and 2.8mm2 with a range The average vertical disc diameter is 1.8mm with a horizontal disc diameter of 1.7mm.
Caucasians - Smaller
Mexicans < Asians < Africans
CDR is normally less than 0.60, relative to the size of the disc so that smaller cupping - small-sized disc and larger cupping - large discs
tends to enlarge in the vertical meridian in glaucoma
Size, How to classify
(could use bloodvessels as broad guide)
optic disc size as small (vertical diameter <1.5mm),
average or large (vertical diameter >2.2mm)
Use slit beam height to match vert - Using 90D
correction factor will be 1.0x for a 60 D lens, 1.1x for a 78 D and 1.3x for a 90 D lens.
Larger with Biomicroscope
ISN’T rule
Neural rim tissue THICKEST
Inferior of the disc, then the Superior and Nasal, being thinnest in the Temporal region
normal neural rim tissue
LAMINA CRIBROSA
It is a sieve-like structure of largely connective and glial tissue that is continuous,
although embryologically distinct, with the scleral coat
OPTIC NERVE DRUSEN
Bilateral
pseudopapilloedema. They are golden, autofluorescent, glowing, calcific globular deposits that sit in front of the lamina cribrosa
can shear blood vessels and/or nerve fibres, leading to haemorrhages (2-10%) and visual field loss (~75%),
Myelinated nerve fibres
Myelin sheathing of the optic nerve fibres that extends beyond the lamina cribrosa and presents a superficial, white, feathery opacification which hides any underlying retinal blood vessels.
Classification of Glaucoma
Normal
- Good rims
- Good IOP
- No Family Hx
- No Trauma related incidents that can increase risk
- No medications that can increase IOP
( Topical and Systemic Steroids / TOPAMAX (Weightloss / seizures / migraines)
Nerve fibre layer striations
brightest at the superior and inferior poles, where the nerve fibre layer is thickest and are best seen in young patients, particularly those with heavily pigmented fundi (Figure 9). The striations are caused by the tubes of astrocytes that surround the retinal ganglion cell axon
Peripapillary atrophy (PPA)
The RPE and choriocapillaris are lost and all that is visible are the large choroidal vessels and sclera
15% of normal eyes bordering the disc BETA zone
More prevelent in glaucoma
Tilted discs & optic disc malinsertion
the disc or discs are commonly tilted inferior nasally with a nasal staphyloma (bulging of the sclera) and situs inversus, where the temporal blood vessels first course towards the nasal retina before sharply changing course
staphyloma can produce a temporal visual field defect
Optic disc basic Examination
C x 3
VEINS &ARTERIES
CUP
CONTOUR
COLOUR
Veins - Darker
Arteries Lighter lumen
COLOUR of optic disc
Orange - Pink
What Causes Palor?
NIGHT TIC
- Neuritis
- Ischaemic
- Granulomatous
- Hereditory
- Traumatic
- Toxic
- Irradiation
- Compression
Goldman Perimetry
Advantages
Goldmann Perimetry
• Advantages
◦Can use both kinetic and static targets
◦Can test both central and peripheral fields
◦Can change both target luminance and size
◦A specific area of the field may be quickly isolated and tested
• Used mostly in low vision and neuro-ophthalm to map fields•
Goldman Perimetry
Disadvantages
Disadvantages
◦Testing the full field is time consuming and tedious
◦The exposure time, speed of movement, and point location are NOT set by the machine, so
there can be variability between users
Automated Fields
• HVF 3 - Has a liquid lens, just enter the Rx
Automated Perimeters
• HVF Analyzer 2
• Octopus
• Oculus Zeiss
Different Types of Stimulus Presentations
- Projection (ie: Humphrey)
- Movable LED (ie: Octopus 1-2-3)
Automated Perimetry
Advantages
• Advantages
◦Testing conditions are reproducible
◦Accurate
◦Numerical results (Not X or sqaures)
◦Most testing can be done by techs
◦Insurance carriers reimburse
Automated Peimetry
Disadvantages
• Disadvantages
◦Interpretation of results can be difficult
◦Variability between different manufacturers —> hard to compare
◦Length of time for threshold testing
◦Initial cost of instrument
Automated VF Luminace terminolegy
Apsotilb (Asb)
Decibels (Db)
and the comparison
• Apostilb(asb.)
◦Unit of light intensity
◦Apostilb = candela/pi m = lumens m
- *• Decibels (dB)**
- *target size** NOT considered or background illumination
◦0.1 log units = 1 dB
‣ 0 dB corresponds to brightest stimulus on a machine
‣ > 0 on a printout means pt cannot see the brightest stimulus
‣ 50 dB corresponds dim stimulus on a given machine
‣ highest you see is about 40 dB
Automated Perimetry
Background
For all automated perimeters, the background is in the mesopic range (between 1-100 asb)
◦This range stimulates both rods and cones
◦Humphrey: 31.5 asb
◦Regular Octopus: 4 asb
Octopus 1-2-3: 31.5 asb
Threshold vs. Sensitivity
• Automated machines are threshold tests
◦Higher dB = dimmer stimulus = the better vision = more sensitive
• ie: a threshold value of 10 dB has a lower sensitivity than a threshold value of 20 dB
◦10 dB is brighter than 20 dB, which means person is less sensitive if this is their threshold
How size of target influence Db and how calculated
Sizes:
◦Humphrey III target is 0.43 deg diameter, 4.00 mm
◦Humphrey V target is 1.72 deg diameter, 64.00 mm
◦Log(4) = 0.6 (6 dB), so going from a III to V would increase the dB by about 12 dB
◦Ie: Test patient in one location with III size and get 20 dB, if you repeat with V size you would
get about 32 dB
Gray Scale
◦Visual representation using varying shades of gray to represent sensitivity
◦Darker gray = greater reduction in sensitivity
◦NOT a substitute for numerical chart —> can be misleading at times
◦Skewed to recognize defects
◦Good tool for patient education
◦Gray scale is a simple representation (not an interpretation)
Fixation Monitoring
Fixation Monitoring
• Heijl-Krakau Fixation Quotient
◦A blind spot is mapped
◦A stimulus is placed at the center of the already mapped blind spot to ensure the pt is not
tracking the stimulus and to check for alignment changes ◦Expressed as a ratio
‣ Numerator = # times the pt lost fixation
‣ Denominator = # of trials
◦Greater than 0.20-0.25 is usually considered invalid or unreliable
Optical monitoring
• Optical monitoring
◦Humphrey system projects infrared light onto the cornea
◦Enables perimeter to calculate the eye rotation from the distance the corneal reflex moves
compared to a baseline measurement taken before VF begins ◦“Gaze tracking”
3 Ways to varify Fixation losses
Tech Tips
how to pause test by holding button
Run demo
Pause every 5mins for break - avoid fatigue artifact
• Monitor pt fixation manually through entire test especially if 10 degree
Fixation Losses
◦Blind spot check is easily fooled
‣ Slight tilting of head or anatomical variation
‣ Catch trials are skewed - more in the first few minutes and less as attention decreases
◦Gaze track can lose its lock
‣ Not all patients pass gaze track initialization
‣ Thrown off by head movement and dry eye
‣ Fair accuracy, 1-2 degrees
‣ Interpretation is subjective (no standards!)
◦Gaze track and fixation loss (FL) catch trials often disagree
◦Direct observation by tech is probably best - final arbitration of reliable fixation
Rx needed for visual Fields?
• Humphrey bowl is 30cm deep
◦Peripheral field —> No Rx needed , the ring of the lens will interfere with the test
◦Central field (30 deg) —> Rx is needed
• metal rimmed trail lenses
• Patient is dilated with anti-cholinergic (tropicamide) to wipe out accommodation, a +3.25 Add should be used
◦Phenylephrine is a sympathetic agonist,
tropicamide is a parasympathetic antagonist
• For Rx’s with 0.75 cyl or below, the spherical equivalent can be used
• For 1.50 cyl, you must use it in perimetry
How to read A Humphries test
+
Considerations.
How to read Humphrey Visual Field Printout
(1). Type of test
◦Threshold or screening?
(2). Name of Patient
◦Always enter the name the same way
(3). Strategy
◦Full Threshold, Fast Pac, SITA Standard, or SITA Fast or SITA Faster
(4). Rx used
(5). Pupil Diameter
◦If pupil is less than 2-3mm, pupil should be dilated
(6). Fixation Losses
◦Predicts validity or reliability, if greater than 20% need to repeat unless there are reasons
(7). False Positives
(8). False Negatives
◦If pt is thresholded at one stimulus, then a stimulus that is 9 dB brighter will be presented at the same point
‣ Ie: 20dB threshold, 9 dB brighter would be 11 dB
◦If the pt does not see this point, it is a false negative
◦May indicate that the pt is tired or no longer attentive to the test
Patient and Perimetrist factors to consider
Human Factors to Consider
• Fatigue
• Learning
• Fixation
• Distractions
• Anxiety
• Medical problems (ie: arthritis)
• Droopy lids
• Pupil size
• Long-term fluctuation
• Short-term fluctiation (indicator of pt reliability)
Perimetrist Factors to Consider
• Correct pt instructions
• Correct type of path
• Correct Rx
• Correct alignment of the patient
• Encouragement of pt
• Rx must be metal rimmed lens
• Lens holder must be close to the eye
• Lid must be held open or taped
• Perimetrist should be sensitive to the individual needs of the pt
Do not create Pseudo defects
• You lose 1 dB per diopter that you’re out of focus
- Dirty trial lens
- lenses instead of - lenses
- Not taking away the lens holder when testing periphery
- Using wrong cyl axis
- Noisy testing room
- Using plastic rims instead of metal
Evaluating a Field
WANDER
◦What was done?
◦Was the field accurate?
◦Was the field normal?
◦What defects are present?
◦Evaluation of visual defect?
◦Re-revaluation of visual field
Visual fields (How many points And location)
24-2
30-2
10-2
24-2C
Usually grid for glaucoma is (24) 54 pts or (30) 76 pts
Macula 10-2 tests 68 points in the central 10 deg
24-2C (new) takes all points of a 24-2 and adds 10 points from 10-2 for a total of 64 points
Full field test goes out to 60 deg —> very useful, but takes too long to threshold
How FULL threshold is determined
The threshold at any given point is determined by a staircase method
◦A 4-2-2 staircase with the last seen value taken as the pt’s threshold
◦Once it has crossed the line from seeing to non-seeing or vice versa, it goes in 2 dB steps
◦At each threshold location, a dB number is assigned
◦Can detect very shallow defects
◦Can take up to 18 mins per eye on some pts
FASTPAC 3-3
Threshold Strategy: FASTPAC 3-3
• Start with 4 seed points at 25 dB, then uses the FASTPAC strategy to get threshold
• FASTPAC then starts thresholding half the points 1 dB brighter and the other half 2 dB dimmer
• It only makes one transition from seeing to non-seeing or vice versa
SITA
SITA FAST
SITA FASTER
SITA (Swedish Interactive Threshold Algorithm)
theoretically better startingpoint
• Data constantly updates as more info is gathered during the test
• Uses frequency of seeing curves
• At the end of exam, threshold values are recomputed using all stimulus luminance with a 50%
probability fo being seen
• It does NOT directly test false positives - uses response time to estimate the false positive response
• It speeds up the rate of stimulus presentation in accordance to how quickly the pt can respond
• Response time is set by the patient
• The machine theoretically calculates when to stop testing points that are fluctuating a lot
• Other algorithms re-threshold if 7 dB off, but this algorithm only retests if 12 dB off 24dB seen
Threshold is 24 dB
SITA Fast
• SITA Faster —> no false negatives and no blindspot checks
◦Rationale: more fields are important and we need to do them quicker
SITA FASTER
◦Rather than using starting point of 25 dB for the 4 primary points, it uses a faster age- corrected normal value
SITA Faster uses only one staircase test reversal
◦The SITA tests use real time determination to stop testing based on full threshold program norms. SITA Faster uses norms from SITA Fast to stop testing a given point
◦Does not re-test absolute blind spots (ie: not seen at 0 dB), while older strategies do
◦Does not test for false negatives
◦Uses gaze tracker for monitoring fixation (does not place a point in the blind spot)
◦Eliminates delay after non-seen stimuli
‣ Older SITA programs had an extra 300ms delay after non-seen stimuli at the end of the response time window before a new stimulus was presented
SWAP
SWAP (Short Wavelength Automated Perimetry)
- Blue target, yellow background
- Do less of this now
- Hard to do with cataracts, hard to interpret the threshold testing
Interpreting Visual field testing
• Very deep defects are easily spotted
- lose a decibel a decade after age 20.
Hill of vision changes roughly 3 dB every
10 degrees throughout the field
Mirror Imaging and Defect Depth (Hirsch)
• If point is 9 dB less than its neighbours, it’s a defect
• If point is 6 dB less than its neighbours, it’s possibly a defect
• If 2 or more points are 6 dB less than neighbouring points, they are probably defects
• Often a collection of points will have a reduced sensitivity (ie: an arcuate or quadrant defect)
◦Comparing the values in different locations on the graph will help identify problems ◦Compare dB values in the same coordinates between eyes
MEAN Deviation
◦Mean elevation or depression of the pt’s overall field compared to normal reference field
◦Takes all points, averages them, compares to your age
◦Peripheral points do not weigh as much, central is more important (weighted average)
◦P<2 means less than 2% of the normal population shows an MD larger than the value found in this test
Total Deviation and
Patern Deviation
• Total Deviation
◦Point-by-point representation of the difference in dB between pt’s test and age-corrected normals
◦Translates into gray scale symbols
◦ie: 33 is what you should score, but you scored 29 —> -3
• Pattern Deviation
◦Similar to total deviation, except results are adjusted for the overall changes in height of PX’s
measured hill of vision
◦If the pt has overall depression, this is filtered out
PSD
◦Pattern standard deviation is a measure of the degree to which the shape of the pt’s measured field departs from the normal age-corrected reference field
◦Low PSD = smooth hill - follows the shape
◦High PSD = irregular hill - all over the place
◦PSD < 3 is abnormal
Visual Field Index
VFI
“what % of the field is normal?”
An enhanced MD designed to be less affected by cataract, and more sensitive to changes near the center of the VF to correlate better with ganglion cell loss
Center >> periphery
Reduces cataract contribution to the measurement of VF loss
VFI plotted against age
◦Facilitates estimates of disability risk
Glaucoma Hemifield Test
GHT
• In glaucoma, inferior rim of the optic nerve is attacked first
• Glaucoma is known to affect one 1/2 of the field to a greater extent before involving the other half
• Compares one half of pt’s VF to mirror image of the other half
◦Looks for asymmetry
◦Can be fooled by symmetrical loss
• Pattern deviation scores in each of 5 zones in the upper hemifield are compared to findings in mirror-image zones in the inferior visual field
• Scoring differences between mirror image zones are compared to normative significance limits specific to each zone pair
• GHT findings are divided in the following categories:
◦Outside normal limits - whenever at least one zone pair differs by an amount found in fewer than 1% of normal subjects
◦Borderline - whenever at least one zone pair differs by an amount found in fewer than 3% but more than 1% of normal subjects
◦General depression or Abnormally high sensitivity - whenever even the best test point locations are either so low or so high as to be at levels seen in fewer than 0.5% of normal subjects
◦Within normal limits - whenever none of the above conditions are met
Which test to do for Gaucoma suspect
• Most doctors do a 24-2 (54 points, 6 deg apart)
• Some do a 30-2 (76 points, 6 deg apart)
• Newest theories on glaucoma: do a 24-2 and a 10-2 (76 points, 2 deg apart)
◦Idea of the 24-2C —> now have 64 points, and the 10 points in the central 10 deg are the ones thought to be the most commonly flagged if glaucoma develops
Which Test Strategy?
• SITA STANDARD vs. SITA Fast vs. SITA FASTER
◦Standard may be more accurate, but not clinically significant
◦Fatigue artifact wins over theoretical
◦SITA FASTER doesn’t do false negatives and doesn’t check fixation (just checks activity at
the bottom)
◦Hanley: SITA Standard >> Fast
‣ Fast misses defects but the data seems to point to not much difference
Which Test to Run: 30 vs. 24 vs. 10?
• For glaucoma, either 24 or 30 is effective, but 24 is faster and lessens fatigue artifacts
◦Eliminates edge points of limited value
◦not involved in early diagnosis, too variable
◦Lessening of fatigue artifact outweighs any theoretical advantage of 30
• For neuro: use 30 with SITA standard or SITA Fast
• For decrease vision and/or endstage glaucoma
◦Always use 10-2 for evaluation of decreased vision ◦2 degree spacing vs. 6 degree
◦24/30 suboptimal for testing decreased vision ◦Potential for detecting early glaucoma with 10-2
Evaluating Threshold Fields Over Time
VFI plotted against age (projected loss)
- ◦Healthy —> lose about 1 dB a decade
- ◦Glaucoma —> lose about 1 dB a year
Guided Progression Analysis (GPA)
• 2 baseline visual fields and compares the new field
• Possible progression - 3 or more points show deterioration in at least 2 consecutive fields (4 min fields)
• Likely progression - 3 or more points show deterioration on 3 consecutive fields (Min 5 fields)
• A simple linear projection is shown as a dashed line
• A regression line is drawn through the best fit to the VFI data
◦Projected out 5 years to help the pt and doctor understand the anticipated impact of glaucoma progression if things continue along the current course
• Cons of VFI:
◦Estimates are more optimistic than those of experts
◦Rates of change over time with both indices were closely related, but the reliance of the VFI
on pattern deviation probability maps have caused a ceiling effect that may have reduced its sensitivity to change in eyes with early damage
‣ In this group of pts, there’s no evidence to suggest that the VFI is either superior or inferior to the MD as a summary measure of visual field damage
• Pts get cataracts over time, so may have to create new base VFs
How many fields are needed to determine progression?
GPA
◦Minimum 5 years with annual testing using linear regression ◦Clinically, minimum of 2, or 3 if major therapeutic intervention planned
◦Suggest 2 in first 6 months, third 4-6 months later
Screening Modes/Tests on Humphries
- Two-zone strategy
- Three-zone strategy
- Quantify defects
• 2 different approaches
(1) Four primary points, one in each quadrant are thresholded
Second most sensitive value used to calculate the expected height of the hill of vision
(2) From the age-related norms, the machine will set the hill
Age related is the one most commonly used
Two-zone Strategy
Two-zone Strategy
- From expected height, theoretical hill of vision is calculated
- Targets then presented 6 dB brighter than theoretical hill
- If seen at 6 dB brighter, then it is tested a 2nd time
- Points missed twice at the 6 dB brighter level are recorded as defects, and a SOLID BLOCK is recorded
3 ZONE Strategy
Three-zone Strategy
• Begins same as threshold-related strategy
◦4 primary points, one in each quad, thresholded
◦Second most sensitive value used to calculate the expected height of the hill
◦From expected height, theoretical hill is calculated
◦Targets 6 dB brighter than the theoretical hill
• Points missed twice at the 6 dB level are retested with the brightest stimulus for the machine
• If see at brightest, an X is recorded
• If not seen at brightest level, a solid block is recorded
• Very useful strategy for patients who have had strokes
Qauntify Defects
• Begins same as two-zone strategy
◦Targets are presented 6 dB brighter than the theoretical hill
◦ If missed twice, the area is then thresholded
◦The number expressed is the depth of the defect from theoretical threshold, NOT THE
ACTUAL THRESHOLD
◦Ie: expect 33 dB point, but pt misses it twice. Thresholded to 10 dB, so 33 - 10 = 23 dB
‣ 23 dB is shown on the quantify defect graph
Quantify Defects
The higher the number, the deeper (worse) the defect
Do not confuse this with the numbers on the full thresholding tests where higher dB is better
If only one isolated point is missed and the defect depth is less than or equal to 8 dB, it probably
does not represent a defect if it is beyond 20 deg
If one point is missed and the defect depth is greater than 8 dB, it probably represents a defect
If two adjacent points are missed with a defect depth of 6 dB or higher, they probably represent a defect
FDP
• Frequency Doubling Perimetry (FDP)
◦Stimulus is a grating of low spatial frequency that is flickered at a high temporal frequency
◦Minimum contrast for each stimulus to be detected is used to determine threshold
◦At a certain frequency, the total number of bars appears to be double
◦When a low spatial frequency undergoes a high temporal frequency, the stimulus display appears to have twice as many light and dark bars than are actually present
• Frequency doubling is controlled by the magnocellular pathway
• The M cells are responsible for low-contrast, high temporal frequency (or motion) stimulus
detection
• They make up only 15% of the total number of axons in the eye
• There is a small subset of M cells called My cells that actually respond to frequency doubling
• My cells are thought to be affected in early glaucoma
• The My cells contribute about 5% of total axons in the eye
Anterior Causes of
Visual Field Defects
• Lids - ptosis
◦Superior defect secondary to location of nodal point
• Cornea
◦Dense scars can create VF defects
◦Corneal dystrophy —> MD decreased, total deviation decreased, pattern deviation looks normal, PSD normal
◦Fields are not usually done for corneal problems, however your glaucoma pt may also have a corneal dystrophy
• Cataracts
◦Usually associated with generalized overall depression, especially nuclear opacities
◦Can be associated with scotomas or localized depression depending on locaiton and density
4 Main terretories for defects after the Nodal point
• Territory I - retinal rods and cones
‣ Macular degeneration, retinal detachments, retinitis pigmentosa
• Territory II - retinal ganglion cells and axons, nerve fibre layer, optic nerve
‣ Nerve fibre pattern on the retina: papillomacular bundle, inferior arcuate fibres, superior arcuate fibres, horizontal raphe, nasal radial bundles
• Territory III - optic chiasm, usually caused by pituitary adenomas
• Territory IV - optic tract, LGN, optic radiations, visual cortex
Visual Field Loss with Glaucoma
• Paracentral scotomas (usually in Bjerrum’s Area 5-20 deg from fixation)
• Central and peripheral nasal steps
◦Inferior macula vulnerability zone
Progression of focal depths
◦Increase in depth (ie: one point goes from 20 dB to 15 dB)
◦Increase in size (ie: 2-3 points affected before, now 4-5 points affected)
◦New scotomas
- *◦Isolated paracentral scotomas merge to form arcuates**
- *• In end stage glaucoma, usually all that’s left is nasal rim**
- *• The last thing to go is 20/20 vision**
Terretory 2 Visual field Defects
• Most common is glaucoma
◦Paracentral —> 70%
◦Nasal step —> 5%
◦Both paracentral and nasal step (upon 1st exam) —>10% ◦Temporal wedge —> 5%
due to changes in rim tissue
• Myelinated nerve fibres
• Drusen on ONH
• Papilledema
• Optic neuritis
• Ischemic optic neuropathy
Direct Opthalmoscopy
General
• The dioptral power of the wheel should be the sum of your Rx (if you are uncorrected) and the pt’s Rx to get the retina in focus
◦Ie: you are a -2 D myope without correction on, your patient is a -4 D myope. The wheel on your oscope should be -6
◦Ie: you are + 4 D without correction on, your patient is pl. Wheel on your oscope is +4
• Angle your head at a 15 degree angle to view the optic nerve, move temporally to see nasal retina
Components to disc Diagraming
• Media - does the disc look clear or hazy
◦Anything along the visual pathway can fog up your view
• Look at disc margins - are they distinct or indistinct
• Crescents - around the disc margins
• Evaluating size of disc
• Evaluating each rim
• Evaluate the size of the cup compared to the disc
• Evaluate the cup rims sloping, undermined, indistinct, etc.
• Proper symbols to be used when drawing an optic nerve
Disc Edema
Ask yourself is it unilateral or bilateral?
• Is the vision decreased?
◦Did it come on quickly or gradually?
• Are there any other symptoms / headache, vomiting, electrical impulses, etc?
What causes indistinct Margins?
• Increased intracranial pressure - papilledema
• Papillitis - infiltration or inflammation of the optic nerve
• Ischemic optic neuropathy
• Pseudo disc edema
congenital tilted nerves in high myopic astigmatic
- *SIGNS**
- *• Hemorrhages**
- *• Dilated, twisted veins**
- *• Tilted discs**
- *• Glial veils** (do not make margins indistinct, because they hover above the retina at the disc)
- *• Crescents**
CRESENTS:
- *• Scleral crescents** - white semilunar patch of sclera adjacent to the optic disc due to the fact that the choroid and RPE do not extend to the optic disc
- *• Choroidal crescents** - occur because the RPE is not abutted to the optic nerve
- *• Pigment crescents** - in almost all eyes, the RPE shows some histological irregularities close to the tip of Bruch’s membrane at the border of the optic disc
- *• Peripapillary atrophy (PPA)** - thinning of the retina and RPE in the region immediately surrounding the optic nerve head
CD RATIO
- Average cup to disc is about 0.35-0.4
- Ilarge discs should have large physiological cups, and pts with smaller discs should have small C/D ratios
- above 0.6 C/D ratio should get VF done
How to evaluate disc size…
• mid-size oscope light target, that’s about equivalent to average disc size
• If you use a 90, 78, 60 DD lens,
◦Correcting factor:
60 is 1.0x
78 is 1.1x
90 is 1.3x
WHICH EYE
- If the vessels are not central, if anything, they move nasally
- Margins - usually the optic nerve slopes temporally
- Fovea will be temporally
- Straight vessels tend to go nasally
- Vessels arch going toward the fovea
Glaucoma Deffinition
New and Old
- Chronic neurodegenerative disease characterized by loss or retinal ganglion cells resulting in distinctive changes in the optic nerve head and retinal and nerve fiber layer
• Optic neuropathy that is consistent with remodeling of connective tissue elements of the optic nerve head and with loss of neural tissue associated with eventual development of distinctive patterns of visual dysfunction
Chronic Open Angle Glaucoma
POAG
- Bilateral with one eye preceding the other
- IOP was greater than or equal to 21 mm Hg and the filtration angle (trabecular meshwork) was open by gonioscopy
- Glaucoma is the leading cause of irreversible blindness in the US. and 2.7 million who are over 40 have POAG
- OAG most common form and affects 95% of individuals with glaucoma. It is more common in African Americans and Hispanics than other ethnic groups. OAG is up to 3-4x more common in African Americans than Caucasians and tends to occur at an earlier age
2 Types of Glaucoma:
- Open Angle Glaucoma – the aqueous appears to have open access to the trabecular meshwork. The iris does not appear to be blocking the trabeculum. Initially this condition has no symptoms. At some point, side (peripheral) vision is lost and without treatment, an individual can become totally blind.
2. Closed Angle Glaucoma – the trabeculum is blocked by the iris and aqueous cannot drain from the eye causing the IOP to rise
RISK Factors
POAG
Primary Open Angle Glaucoma
- Age
- African or Latino ethnicity
- Family history
- Increased IOP
- Myopia
- Decreased corneal thickness
- Diurnal intraocular pressure variation
- Long-term intraocular pressure variation
- Sleep apnea
- Migraine sufferers
Risk Factors
Angle closure Glaucoma
Angle Closure Glaucoma
- Age
- Female gender
- Asian ethnicity
- Shallow anterior chamber
- Short axial length
- Small corneal diameter
- Steep corneal curvature
- Shallow limbal chamber depth
- Thick or anteriorly positioned lens
Genetics - Inherited Glaucoma
Genetic loci linked to POAG
underlying genes Myocilin (MYOC),MYOC appears to affect protein unfolding in the trabecular meshwork Optineurin (OPTN) and WD repeat Domain 36, (WDR36) is well established
Glaucoma Prevelance based on RACE
POAG vs Angle Closure
Open angle glaucoma VS Narrow angle glaucoma dt race:
- Whites 11:1
- African American 150:1 (More OAG)
- Chinese 1:3 (More angle closure)
Prevalence of POAG Glaucoma based on race
European descent is about 2.5% for patients over 40
5.6% of African Americans have open angle glaucoma
Filipinos >>> Caucasions to normal tension glaucoma and POAG
Inuit’s over 40, 2-3% have angle closure glaucoma (opposite)
• Asians in general have more normal tension glaucoma and more angle closure (Highest) risk as a large amount of the population have narrow angles
Age as a risk factor
Increased risk of glaucoma as you get older. Age serves as a marker for metabolic and degenerative changes of the tissue.
Prevalence is about 0.25% at age 20 and doubles every 10 years.
Gender as a Risk Factor in Glaucoma
Gender – no significant difference for primary open angle glaucoma.
Females are more prone to angle closure glaucoma, the reason is
unknown. More women have open angle glaucoma mostly because women tend to outlive men
Sample set is larger.
Juvenile Glaucoma
Primary Pediatric Glaucomas are classified as follows:
- Congenital glaucoma (congenital open angle glaucoma)
- Juvenile open angle glaucoma
- Glaucoma associated with systemic disease
- Glaucoma associated with other ocular anomalies
Causes and Variations of Juvenile Glaucoma
Primary congenital glaucoma – about 20-40% of the cases are caused by increased IOP during life in the womb and the baby has ocular enlargement of the eye (buphthalmos).
Features include: enlarged corneas, Steamy corneas, elevated IOP, Haab striae may present at birth or prior to 1 month (newborn)
- Infantile PCG presents within the first 2 years
- Late diagnosed PCG may present after the age of 2
Congenital Glaucoma
Congenital Glaucoma is present at birth and bilateral in 2/ 3 of cases.
Males >> than females except in Japanese individuals. It is thought to be due to a developmental defect where the iris inserts more anteriorly than in normal eyes which prevents fluid from draining causing an increase in IOP. The prevalence is higher in cultures with consanguinity, particularly those with a high carrier rate of CYP1B1 gene (GLC3A locus on chromosome 2p21) and LTBP2 within GLC3C locus
Congenital/ infantile glaucoma presents with marked elevated IOP causing the sclera to enlarge and become thinner. The eye looks bluer than normal because the choroid is more easily visualized through the thinned sclera.
The common clinical triad is epiphora, blepharospasm and photophobia.
The cornea appears cloudy due to edema from the increased IOP, horizontal breaks in Descemet’s membrane occur called Haab striae and the scleral canal increases in size. The normal cornea of an infant is 10mm (adult is 11.8mm), > 13mm corneal diameter is suspect before the age of 1 and >14mm is typical of advanced buphthalmos.
Normal versus Abnormal angle presentation in an infant
The normal anterior chamber of an infant compared to an adult
- Less pigmented TM
- Less prominent Schwalbe line
- Less distinct junction between scleral spur and CBB
• In PCG (primary congenital glaucoma)
- There is high iris insertion
- The angle recess is absent
- The iris root appears as a scalloped line of glistening tissue. This glistening membrane is what is referred to as Barkan’s membrane and likely represents thickened and compacted trabecular meshwork.
Juvenile Glaucoma
- The disease becomes manifest after 2 years, but before 16 years of age.
- Most cases of juvenile appear be autosomal dominant with only minor sporadic cases occurring.
- These cases are linked to TIGR (trabecular meshwork inducible glucocorticoid response) / MYOC (myocillin ) gene locus GLC1A
Name 2 systemic diseases causing Juvenile Glaucoma
Axenfeld Riegers Syndrome
Sturge Weber syndrome.
Sturge Weber Syndrome
Congenital, It is characterized by a facial birthmark and neurological abnormalities.
Ocular manifestation is high IOP in eye with port wine stain. Glaucoma 70% , when birth mark close to eye / the hemangioma is
on the upper lid.
Patients can also have CNS angiomas which can produce seizures.
GLAUCOMA caused due to an isolated trabeculodysgenesis.
As the child ages, elevated IOP is due to elevated episcleral venous pressure that occurs as a result of arterioveonous shunts through the episcleral hemangiomas.
Patient have a marked increase in pigment in one eye and more pigment in TM about 10% have elevated IOP in the hyper pigmented eye.
Nevus of ota
Nevus of Ota presents as a blue or gray patch on the face, which is congenital, with onset at birth or around puberty and is within the distribution of the ophthalmic and maxillary branches of the trigeminal nerve. The nevus can be unilateral or bilateral, and, in addition to skin, it may involve ocular and oral mucosal surfaces
Types of field loss in Glaucoma
Focal loss
Increase in short term fluctuation on threshold fields
Paracentral scotomas (usually in Bjerrum’s Area 5-20 degrees
from fixation)
Central and peripheral nasal steps
Progression of focal depths
o Increase in depth (one point goes from 20 db to 15 db)
o Increase in size (2-3 points affected now 4-5 points affected
o New scotomas
o Isolated paracentral scotomas merge to form arcuates
Early glaucoma changes, predict field loss
Superior nasal
Paracentral scotoma
Predict the fisual field loss in moderate Glaucoma
Superior Arcuate Scotoma
Bjerrum’s Area 5-20 degrees
& Nasal Step
Predict the field loss in this Moderate advanced glaucoma Px
Superior arcuate scotoma
Inferior Paracentral scotoma, general depression
Predict the visual field defect in Advanced Glaucoma
Temporal island OD
Visual field defects in Glaucoma
Progression of visual field defects
Progression of glaucoma field defects
3 Phases of Glaucomatous field loss:
I / T / M
- Initial Phase - IOP is causing damage to the optic nerve head but the field is normal
- Threshold Phase - patient shows an increase influctuationand visualfields are inconsistent andvariable
- Manifest Phase - positively reproducible visual field loss
Causes of a generalized depression MISTAKEN for Glaucoma
Decreased MD / Also with Glaucoma
o Wrong Rx
o Cataracts
o Miosis
o Aging and other ocular conditions
Criteria for Minimal Abnormality in Glaucoma
Three or more adjacent points in an expected location of the central 24 field* that have P < 5% on the pattern deviation plot, one of which must have P < 1 % on at least 2 consecutive fields
OR
Glaucoma hemifield test“outside normal limits“ on at least 2 fields ‘(Upper and lower differ from each other by P<1% or 2 corresponding zones are both depressed relative to normal at a P< 0.5% level
OR
Corrected pattern standard deviation with PSD flagged at 5% on two consecutive fields
* Must be nonedge points in central 300 field
GRADING of defects in Glaucoma
EARLY DEFECT
Lower IOP 20-30%
T-Target
Mean deviation > -6 dB
or
On pattern deviation plot, depressed below the 5% level and fewer than 15% of
points depressed below 1% level
or
No point within central 5 below 15dB
Visual field defect GRADING
Moderate defect:
Mean deviation worse than -6 dB but not less than 12dB
or
On pattern deviation plot, < 50% of points
depressed below the 5% level and fewer than 25% of
points depressed below 1% level
or
No point within central 5 below 10dB
or
Only 1 hemifield containing a point less than 15 dB within 5 of fixation
Visual field defect GRADING
SEVERE Defect
40 - 50% IOP lowering
Mean deviation worse than -12dB
or
On pattern deviation plot, > 50% of points
depressed below the 5% level and more than 25% of
points depressed below 1% level
or
No point within central 5 less than or Eqaul to 0dB
or
Only 1 hemifield containing a point less than 15 dB within 5 of fixation
CAPRIIOLI’s Criteria for Abnormality
- Three contiguous points same side of horizontal
- One points p<1% or worse on Pattern Deviation Plot and two other points p<5 or worse
What causes Changes to the Optic nerve
with POAG
ISCHEMIC THEORY
The blood supply from the short
posterior ciliary artery and surface of nerve supplied
by retinal arterioles of the CRA
Increased IOP → decreased perfusion → lamina crushes axons → cupping
Perfusion pressure is insufficient to support adequate blood
flow through the nerve
Glaucoma patients do not have good autoregulatory control when their IOP goes up
Causes for Changes of Optic Nerve in
POAG
Lamina Distortion Theory
IOP causes compression of the lamina sheets →
mechanical compression of the axons and also
compresses the arteries cupping →
NFL drop out and death of the axons.
- Mean of 550 pores in lamina smaller temporally + nasally and bigger Superior and Inferior
Bigger Pores = Easier to crush
Causes for the change of ONH glaucoma
Interruption of Axoplasmic flow
Axonal transport at the level of lamina and organelles
within the NFL is stopped due to elevated IOP
long enough time, NFL death will occur
o 5 dB loss probably corresponds to a 20 % loss of axons
Y Axoplasmic flow also stops with ocular hypotony ( 4mmHg)
pressure difference across the ONH regardless of high or low IOP, causes
mechanical compression of the axonal bundles
Causes for the change of ONH glaucoma
NFL Death
Neurotrophin deprivation and Glutamate toxicity
- Neurtotrophin are peptides - development and maintenance retinal ganglion cells.
glaucoma there is an obstruction of neurotrophin
transport to the ONH which results in RCG apoptosis
neurotrophic deprivation
dt loss of neurons in the lateral geniculate nucleus
Y Glutamate is a normal neurotransmitter may accumulate to toxic levels secondary to release from apoptosis
Causes for the change of ONH glaucoma
Brain disease
CONCLUSIONS:
Y These results suggest that patients with glaucoma undergo widespread and complex changes in cortical brain structure and that the extent of these changes correlates with disease severity.
Y Considered together, these data suggest that patients with glaucoma may have volumetric gains in some structures early in disease, but that brain volumes decrease toward and in some cases below control volumes as the disease progresses
Y Also OCT seem to show Ganglion loss with Glaucoma but also
with Alzheimer Disease
Spontaneous venous Pulsation
In glaucoma
lack of SVP may be also more important when
we consider POAG
Y Possibly be due to the fact that Px’s
glaucoma have significantly lower CSF pressure than
patients without glaucoma
Optic nerve changes in
GLAUCOMA
- Generalized Enlargment of the cup
- Barring of Circumlinear Vessels
- Bean Potting
- Vertical Elongation ( 0.2 more than Hor cupping)
- Notching
- Drance Hemhorages (dt notch, inferior disc. Splinter hem dt stretching that it ruptures)
- Asymmetry of CD Ratio between eyes (Diff of 0.2 and more)
- Distorted Lamina Dots
- Aquired Optic pit
- PPA (Peripapillary Atrophy) BETA ZONE
- NFL Dropout
- Nasal cup - extendes past BV / Nasal shift of BV
Classification of Glaucoma
Ocular Hypertension
IOP >22 mm Hg
Optic nerve head is normal
Visual field is normal
4-10% of patients over 40 are ocular
hypertensive
IOP 24 to 32 in one eye and at
least 21 in the other eye
30-2 q(6) months and stereo
photos every year
Classification of Glaucoma
PACHYMETRY consideration
Basically thin corneas are considered to be a risk for glaucoma
but one should not convert all IOPs with the chart is what we
do now
Classification of Glaucoma
Ocular Hypertension study
Summary
A 20% reduction in IOP resulted in a 50% reduction in the
development of primary open angle glaucoma in a 5 year
span.
o 4.4% progressed to glaucoma in treated group
o 9.5% progressed to glaucoma in untreated group
>90% of OHTS patients when left untreated did not progress
in 5 years
CCT should be measured
Glaucoma RISK calculator
5 inputs
The estimated risk of development of glaucoma in 5 years
- Age
- IOP 20-32 x3
- Central Corneal thickness (475-650) x3 could change DT LASIK SX
- Pattern standard deviation x2
- Vertical cup disc by contour
- *Low < 5%** Observe and monitor
- *Moderate 5-15%** Consider treatment
- *High >15%** treatment
Phase 2 Of Ocular Hypertension study
Summary
This showed that early IOP-lowering intervention reduces the
cumulative burden of disease,
The absolute effect was greatest in patients with the highest
risk as determined by a prediction model that was developed
and validated using OHTS data. It incorporates age, IOP,
central corneal thickness, cup–to-disc ratio and field pattern
standard deviation as significant risk factors.
POAG Glaucoma Suspect
Px classification
2 sibling with POAG
large cupping with normal visual fields and IOP
larger than usual diurnal variation on IOP
asymmetric c/d
large c/d but normal fields
AAO Def: following findings in at least 1 eye:
- Optic nerve or nerve fiber layer defect suggestive of glaucoma ( enlarged cup–disc ratio, asymmetric cup–disc ratio, notching or narrowing of the neuroretinal rim, a disc hemorrhage, or suspicious alteration in the nerve fiber layer)
- a visual field abnormality consistent with glaucoma
- an elevated IOP greater than 21 mm Hg
- Naturally the gonioscopy angle is normal and open
- An individual with a suspicious nerve or NFL appearance in the absence of a visual field loss
- A visual field defect suggestive of glaucoma in the absence of a corresponding glaucomatous optic nerve abnormality
POA Glaucoma Suspect
Open-angle glaucoma suspects
(based on the number of risk factors: family history, race,
elevated IOP, optic disc appearance and thin central corneal
thickness):
Open-angle suspect, low risk (one or two risk factors)
Open-angle suspect, high risk (three or more risk factors)
Classification Of Glaucoma
POAG
Primary open angle glaucoma
- Gonioscopy shows an open angle
- IOP is > 21 on at least one occasion
- Not associated with known ocular or systemic disorders that cause increased resistance to aqueous outflow or damage to the optic nerve(i.e. patient does not have PXE or steroid induced glaucoma)
- The optic nerve shows a characteristic optic neuropathy that is consistent with
- excavation and undermining of neural and connective elements of the optic disc and eventual
- development of distinctive patterns of visual dysfunction.
POAG
RISK FACTORS
- ISNT Rule
- Rim notching
- NFL dropout
- High IOP
- Distorted Lamina
- Drance Hemorrhages
- C/D asymmetry
- Greater than .6 cupping
- Thin corneas
- Abnormal gonioscopy
- Abnormal OCT of optic nerve
- Hx of hyphema
- Hx of ocular trauma
- Family Hx of glaucoma esp sibs
- Hx of PXE or PDS
- Migraine/Raynaud’s
- Race - African American
Goal of Treatment POAG
- To preserve visual function by lowering IOP to a level that is likely to prevent further optic nerve damage
- Therapy with the fewest adverse affects
- Least amount of disruption to patient’s life
- Cost consideration
Can only treat currently by lowering IOP
SX and Laser:
selective laser trabeculoplasty (SLT) in some patients may be a
first line
Injections / MGIS / ALT
Treatment Considerations
POAG
Principal factors:
Life expectancy
Stage of Disease
Rate of Progression
History
IOP since and multiple readings
Optic nerve evaluation
Visual fields
Pachymetry
Imaging OCT
Gonio (always do gonio before you treat glaucoma)
Classification of Glaucoma
MILD / MODERATE / SEVERE
Mild:
Definite optic disc, RNFL, or macular imaging
abnormalities consistent with glaucoma and a normal visual
field
Moderate:
- *Definite** optic disc, RNFL, or macular imaging
- *abnormalities** consistent with glaucoma
visual field abnormalities in one hemifield that are not within 5 degrees of fixation
Severe:
visual field abnormalities in both hemifields and/or loss
within 5 degrees of fixation in at least one hemifield
Guidelines for Glaucoma
- Establish baseline IOP 3x
- Obtain an OCT
- Classify amount of glaucoma damage as mild, moderate, severe
- Use the highest IOP (Tmax) and set target pressure based on the severity of the glaucoma
- Consider lowering target pressure an additional 10% if patient is
* *younger than 50 years, African American, monocular , or has a sibling with advanced glaucoma**
T-max
T- Target
Tmax
Highest the IOP ever been recorded in the eye
Importance of this number as the calculation of the
target pressure is based off of Tmax, not the IOP at the time of
diagnosis or starting treatment
T-Target
Classification of Glaucoma
severity of the glaucoma
IOP from baseline (Tmax) by different amounts
o Mild Severity – 20-30% IOP lowering
o Moderate Severity – 30-40% IOP lowering
o Severe Severity – 40-50% IOP lowering
o Though new guidelines from AAO recommend starting with a
minimal of 25% reduction
Ocular hypertension
o Lower the IOP by 20%-30%, or to 20 mm Hg or less.
Structure Vs Function evaluation
Glaucoma
Theoretically remember 20% loss of NFL(Structure) to get 5dB field loss(Function)
OCTs to monitoring structural
consistent with glaucoma however
Y Once the damage is significant,
- *visual fields** are probably best
- *to monitor progression**
- Stereoscopic viewing of the optic nerve still the way to diagnose glaucoma
- OCT have a lot of false positives and false negatives.