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What are the 4 components of accommodation?
- 1. Proximity
- 2. Retinal Blur
- 3. Vergence
- 4. Tonic
- Bonus - chromatic abberation is another stimulus.
Describe the proximity component of accommodation?
Its a psychophysical phenomenon that is just the apparent nearness of the target.
What part contributes most to accommodation?
Retinal blur. Its also known as the reflex accommodation.
What is CA/C?
Convergence accommodation to convergence ratio. Its used to determine the change in accommodation that occurs when the patient converges or relaxes convergence a given amount. Its complicated to measure, thus we dont do it in clinic?
What is dark focus?
This is also known as tonic accommodation. It is the amount of accommodation always present even at resting state. Known to be 0.50-1.00D.
What are the 3 critical tests for assesing the accommodation system?
- 1. Amplitude of Accommodation (Sheard's, Donders)
- 2. Facility of accommodation (Flippers)
- 3. Accommodative response (MEM)
What are the advantages and disadvantages to Donders push up method?
- Advantages - Easy to perform
- Disadvantages - Tends to overestimate AoA. Why? The 20/20 is at 40cm..but when moved to 20cm, it now looks like 20/40...This is RDM!!! Kids will also get confused on the definition of blur!
Explain Sheards method
- This is the most reliable method in clinic.
- We do it behind the phoropter with pxs best corrected distance Rx. We do not use the little snellen chart, but the 20/25 or 20/30 line. Remember this MONOCULAR! Start with OD by adding minus lenses until the patient reports blurry (by reading it out loud). Go to OS and do the same thing. Go back and forth until OU completely blurred. Dont forget to take 2.50D out at end for working distance.
Disadvantage - minification of line may confuse patient..thats why you must have them read it out loud..When they cant anymore, take that as your last lens!
What are Donder's expecteds?
What are the Hofstetter's Formulas?
- Maximum Expected = 25-(0.4)(age)
- Average Expected = 18-(0.3)(age)
- Minimum Expected = 15-(0.25)(age) USE THIS ONE!
Define Accommodative facility
This is how efficient can the patient stimulate and relax accommodation.
We test it by +2.00/-2.00D flippers moncular and binocular!
What are the monocular flippers for and what are the expecteds?
Monocular flippers check for accommodative anomolies.
- 6 yrs 5.5 +/- 2.5cpm
- 7 yrs 6.5 +/- 2.5cpm
- 8-12 yrs 7 +/- 2.5cpm
- 13-30 yrs 11 +/- 5cpm Dont do past 30 due to pre presbyopia!
What are the binocular flippers for and what are the expecteds?
Binocular flippers check for binocular/vergence anomolies
- 6 yrs 3 +/- 2.5cpm
- 7 yrs 3.5 +/- 2.5cpm
- 8-12 yrs 5 +/- 5cpm
- 13-30 yrs 8 +/- 5 cpm
- 30-40 yrs 9 +/- 5cpm
What is MEM measuring?
MEM is measuring the accuracy of exerted accommodation measured to a specific point in space (usually 40cm for clinic)
How is MEM performed?
This is performed at the pxs WD (Harmon distance) OUTSIDE the phoropter in FULL illumination. Place the best corrected distance Rx on patient. Place the special card on your retinoscope and use the loose lenses (+0.25, +0.50) and have them read out loud the words/letters on that card. Dip the lens in front of the OD and only hold it for half a second and SCOPE QUICKLY! Find neutrality and do OS.
- Expected is +0.50 +/- 0.50D Lag
- Lead is measured with minus lenses
What are the factors that influence the accommodative response?
- 1. Depth of focus
- 2. AC/A
- 3. Pupil Size
- 4. Target color
Binocular crossed cylinder AKA?
BCC, FCC, X-cyl
T/F? You place a tentative ADD for a presbyope when performing BCC
We leave the best corrected distance Rx in the phoropter, becuase it will be overestimated if we use an ADD.
Why is NRA/PRA relative?
It is a binocular accomodative test! You are also not changing the working distance (the target is stationary), while stimulating and relaxing the accomodative system.
What is NRA?
Negative relative accommodation.
Its tested with plus lenses until the first sustained blur. It will relax the px's accommodation, thus relaxing vergence. The patient will need to keep the image single, so they will induce Positive fusional vergences.
What is PRA?
Positive relative accommodation.
Its tested with minus lenses until the first sustained blur. It will stimulate the px's accommodation, and thus convergence. The patient will need to keep the image single, so they will induce negative fusional vergences.
What are the NRA/PRA expecteds?
- NRA = +2.00 +/- 0.50D
- PRA = -2.37 +/- 1.00D
- If you overplus, the NRA will be low and PRA will be high
- If you overminus, the NRA will be high and PRA will be low
In terms of accomodative anomolies, what does functional mean?
Functional problems are those where the patient has poor motor task skills or developmental anomolies.
Opposite to that would be pathological...etc.
What are some general symptoms of accommodative problems?
- Variable VA at D/N
- Tired when reading
- Fall asleep when reading
- Eyestrain and fatigue when reading
- Headaches around eyes WITHOUT sinusitis
- Miscalling words while reading
- Increased sensitivity to light at near work
- Tendency to hold reading material closer or futher away
What are some general signs of accommodative problems?
- Variable acuity while doing refraction (not a malingerer)
- Pupil variation while taking VAs
- Inconsistance with entering VAs and findings
- Fluctuating pupils while performing retinoscopy
- Inability to obtain reliable and accurate final Rx
What are the 3 most common accommodative anomolies?
- 1. Accommodative insufficency - 84%
- 2. Accommodative infacility - 12%
- 3. Ill-sustained accommodation - 1%
What are the symptoms of accommodative insufficiency?
- Blurred vision when seeing from D and switching to N (classic)
- Difficulty copying from board and then to the note book
What are signs of acommmodative insufficiency?
- The AoA is 2D below the minimum expected (HOFSTETTERS)
- The px will tend to reject minus lenses at near and accept plus
- There will be a high NRA in comparison to PRA
- BCC/MEM will be higher lag
- Flippers will show difficulty with minus and lower cpm
What are the phorias expected in accommodative insufficiency?
- Ortho, EP, XP...can be anything!
- Most commonly is Exo
What are some organic causes to accommodative insufficiency?
- Toxicity by poisoning
- Cranial surgical trauma - whiplash
- Post cranial surgical trauma
- Viral infections
- Dental cavities
What is the treatment for accommodative insufficiency?
Visual therapy (which is the best) which is geared towards stimulating accomodation by emphasizing negative lenses.
As a secondary target, you want the dynamics (facility) of the target to be more efficient.
What is the management for accommodative insufficiency?
This is not a cure, just a compensation for the problem.
We can place a near point ADD on a FT design. For computer users, try a PAL.
For a child with constant wear, give 2 Rxs. One for distance Rx to horse around and another with the bifocal for school work.
What are the symptoms of accommodative infacility?
The classic one is where the patient has difficulty looking from D to N and also N to D.
Explain accommodative infacility
This is problem of the facility and dynamics of accommodation. The px cannot relax or stimulate accmmodation effectively.
What are the signs of accommodative infacility?
- AoA, BCC, MEM are normal! If AoA is low, then its a combo diagnosis with Accommodative insufficiency.
- Low NRA and PRA (equally low)
- Flippers will show monocular difficulty with plus and minus (be sure to note that the time it takes to clear is equal from the start of the test)
What are some organic causes of accommodative infacility?
- Grave's disease
- Cerebral palsy
- Drugs affecting the CNS (as a rebound effect)
T/F Near point ADDs are a great way to manage accomodative infacility
Remember your patient cannot accept plus or minus at this moment, so bifocal wont do squat (in terms of management or treatment)
What is the treatment for accommodative infacility?
- Visual therapy with emphasis on plus and minus lenses. We want to stimulate and relax accommodation. We also want to create the accurate jump from stimulation to relaxation.
- The second phase is to perform the jump as fast as possible so the patient can be efficient.
What is Ill-sustained accommodation?
This is a problem of stamina. The patient cannot hold accommodation at that point, where they will tire out quickly.
What are the symptoms in Ill-sustained accommodation?
The classic one is intermittent symptoms when reading..It gets blurry and clear at near!
What are the signs of Ill-sustained accommodation?
- Normal AoA - however if you repeat a suspect, it will get progressively lower
- BCC, NRA/PRA, MEM usually normal
- Flippers are most important. Will start out normal with plus and minus, but will get progressively worse over time (more with minus)
What is the best management for Ill-sustained accommodation?
There is none! Bifocals will not help!
What is the best treatment for Ill-sustained accommodation?
Visual therapy! We have to emphasize both plus and minus lenses to help stimulate and relax accommodation. However when doing minus lenses, have the patient hold the lens longer than the plus to encourage holding accommodation longer.
What is Accommodative excess?
The patients accommodative response is greater than required (like 1D is needed, but px responds with 3D instead)
This is not when a patient has more amplitude according to Hofstetters. This is actually a good thing!
What is an Accommodative spasm?
This is basically same thing as accommodative excess. But in terms of definition, it is spastic for an amount of time. They cannot physically relax the accommodation, so they hold the blur for 5-10 minutes, 1 hour...etc.
What are the symptoms for accommodative excess?
The classic one is when the patient has difficulty with distance vision after reading.
What are the signs in accommodative excess?
- AoA is normal
- BCC, NRA, MEM (towards lead) are low.
- PRA can be high and go over 2.50 in relation to NRA
- Flippers has difficulty with plus under monocular, but can carry over to binocular conditions
Remember the patient has difficulty with plus at near!
What are non functional causes of accommodative excess?
- Drug Tx with cholinergics
Functional problems are very infrequent!
T/F Visual therapy wont help the accommodative excess patient
It will help as management cant do anything for the patient. VT is the best option!
Why wont bifocals help accommodative excess patients?
Remember plus lenses make things worse for this patient. You never want to give a near point ADD. Best option is to go into VT.
Explain VT for accommodative excess
VT will be emphasized with plus lenses to "stimulate" the relaxation of the patient.
T/F Cycloplegic refraction is key with accomodative problems
Standard of care states that you cycloplege kids with hyperopia and myopia. Especially if you see myopia, you can suspect accommodative excess.
What is psuedomyopia?
Psuedomyopia is the phenomenon where the patient has accommodative excess. If the patient is exerting too much accommodation, he is increasing the plus in the system so much that he induces myopia. Since its not "real" its dubbed psuedo. Your refraction may find myopia, but on cycloplegia, you find hyperopia. This is key for the accommodative excess patients!
What can cause a spasm of near reflex (SNR)?
- Psychological conditions
- Cerebral palsy
- Head trauma
What is in the triad of spasm of near reflex?
- 1. Pupillary miosis
- 2. Psuedomyopia
- 3. Esotropia
What is the definition of unequal accommodation?
When there is a difference of more than 1D between the eyes (from Sheards method)
T/F If you see 2.50D difference in accommodation between the eyes, I dont have to repeat the sheards test.
Unequal accommodation is where there is more than 1D difference between the eyes. It is VERY RARE and almost no one has unequal accommodation. Recheck your sheards and refraction with biocular balance!
What do you do if there is puillary involvement with unequal accommodation?
This is a neurological problem, so send out for a neuro consult ASAP!
What are causes of unequal accommodation?
- Head trauma
- Blunt trauma to the eye
- Unilateral amyblopia
- Pharmacological agents - cholinergics and adrenergics
What is a paralysis of accommodation?
This is no accommodative response in the effected eye with a mydriatic pupil and EOM involvement.
What causes paralysis of accommodation?
- Dengue seasons in PR
Whats the difference between unilateral and bilateral paralysis of accommodation?
- Unilateral - The lesion is peripheral
- Bilateral - The lesion is nuclear
What is amplitude scaled facility?
This is accomodative facility testing that takes into account the px AoA.
- The test distance is 45% amplitude.
- = 1/(amplitude*0.45), rounded to nearest 0.5cm
Lens power range = 30% amplitude and divided by 2, rounded to the nearest 0.25D
- Example: Px amplitude = 10D
- Distance = 1/(10x0.45) = .222m or 22cm
- Lens range = 10x0.3 = 3D, thus use +/-1.50D
What are some good starting points in accomodation VT?
- - Always determine the best distance Rx and give the most plus the patient accepts (dont want them to overacommodate at any moment)
- - Emphasize the lens that causes difficulty
How long does accomodation VT take?
Usually 10-12 sessions
What is the first phase of accomodation VT?
- Ocular motilities - start monocular and then binocular
- Saccades and pursuits for 4-5 sessions
- This is done first because its easy and builds rappore with Dr.
- At the 4th session, start integrating training
Describe the monocular phase of acommodation VT
- 1st - increase amplitude - We want a px to do a jump from +2D to -6D (8D jump!) without time
- -starting point is the px NRA and PRA values. NRA never goes above +2.00D
- 2nd - Dynamic training - you want the patient to do the 8D jump in 20cpm by using the metronome at 40bpm. .
- - this is highly unlikely, but shoot for the best
Whats bi-ocular mean?
Seldom used techique in VT
This is where there is a stimulus in both eyes, but there is no sensory fusion. Only one eye sees the actual target.
Whats the goal in binocular accommodation VT?
A jump from -2.00 to +2.00D at 15cpm. This is difficult!
What are the vergence phases in accommodation VT?
This the phase that trains convergence and divergence responses.
The last phase is vergence/accomodation flexibility. This allows a clear and single image for both systems. It is done by using plus and minus lenses with vergence training. This will allow more flexibility between both systems.