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31 Cards in this Set
- Front
- Back
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Components of Accommodation:
what is Reflex Accommodation |
1. automatic focusing of the eye in order to obtain clear retinal image
2. occurs in response to retinal blur 3. **Largest most important component in accommodation under monocular and binocular conditions** |
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Components of Accommodation
what is Vergence Accommodation |
1. Accommodation that is induced by the vergence system
2. gives rise to the CA/A Ratio 3. **Second Major Component in Accommodation** |
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Components of Accommodation
what is Proximal Accommodation |
1. accommodation caused by the knowledge of nearness of obj
2. can be induced by obj within a distance of 3m 3. contributes to 4-10% of the total accommodative response, under normal binocular viewing conditions 4. stimulate by perceptual cues 5. no retinal feedback components |
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Components of Accommodation
what is Tonic Accommodation |
1. accommodation present by virtue of just being alive
2. NO STIMULUS 3. baseline neural innervation from midbrain 4. measured in complete darkness with nothing to stimulate proximal accommodation 5. ~1.00D in adults (range: 0-2D) |
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what can be said about a patient that FAILS TO CLEAR MINUS in BAF
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1. problem STIMULATING accommodative system (AI)
2. minus causes an increase in ESOPHORIA which requires even more NRV to keep the target single (CE) |
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what can be said about a patient that FAILS TO CLEAR PLUS in BAF
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1. problem RELAXING accommodative system (AE)
2. plus causes an increase in EXOPHORIA which requires even more PRF to keep the target single (CI) |
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what is the formula for expected values of accommodation
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Minimum= 15 - (1/4)(AGE)
Average= 18- (1/3)(AGE) |
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what can cause accommodative fatigue? (3)
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1. uncorrected hyperopia or astigmatism
2. anisometropia 3. myopes who read with their Rx crucial to consider the pts refractive status when examining the accommodative system |
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how do you test amplitudes of accommodation?
how do they compare with each other in terms of estimation |
must have the patient fully corrected (false values)
Push Up: - overestimates amp by 2D Pull Away: - PREFERRED METHOD - better certainty of obtaining first sustained blur - measure target at spectacle plane Minus Lens to Blur -lower values than PULL AWAY |
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what is the preferred method of determining the ACCOMMODATIVE POSTURE on a NON PRESBYOPE, especially in kids
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1. MEM
2. Objective testing |
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at what distance is MEM performed at?
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- Harmon Distance
- elbow to middle knuckle |
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how long should you hold a lens in front of a patients eye when doing MEM
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1. Quickly place lens over the eye you are examining to see neutrality
2. just long enough to see the REFLEX 3. holding the lens for too long will start to affect the patients accommodative system |
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what conditions correlate with a LAG of accommodation?
LEAD?? |
LAG (plus value):
1. Accommodative Insufficiency 2. Convergence Excess LEAD (minus value): 1. Accommodative Excess 2. Convergence Insufficiency |
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what is the norm for MEM
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+0.25 to +0.75
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what is the difference between AI and presbyopia
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Presbyopia has...
1. age 40+ years old 2. amp is not sufficient to sustain clear/comfortable vision at near 3. AMP IS NORMAL FOR AGE |
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how can AI manifest as ESO or EXO
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manifest ESO:
1. at near if convergence is overestimated to encourage accommodation manifest EXO: 1. at near if accommodation does not stimulate convergence enough |
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Accommodative Insufficiency:
1. amps 2. MAF or BAF 3. MEM or BCC 4. PRA |
1. amplitudes less than 2D than expected in age
2. MAF/BAF fails through MINUS 3. MEM/BCC high LAG 4. reduced PRA |
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how can you detected ILL SUSTAINED ACCOMMODATION
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AMPLITUDES MUST BE REPEATED
- fatigue with after 5-10 times - prequel to AI - same measurements as AI |
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what is accommodative infacility?
what test COULD be abnormal |
1. accommodation slow in making change from distance to near
could be abnormal: 1. reduced MAF/BAF 2. reduced NRA/PRA 3. low BO/BI findings at NEAR |
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what are the findings of accommodative excess:
1. MAF/BAF 2. MEM/BCC 3. NRA |
1. fails through PLUS on MAF/BAF
2. LEAD on MEM/BCC 3. LOW NRA |
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how does AE manifest EXO or ESO
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EXO:
- stimulation of accommodation (CA/A link) at near to overcome EXO POSTURE if the primary problem is the exo posture at near ESO: - with accommodation the #1 problem, over accommodation (AC/A link) leads to an overall ESO posture at near |
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what are some signs that a patient will accept PLUS LENS
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1. NRA higher than PRA by +0.50 or more
2. MEM greater than +0.75 |
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are are some exam values that suggest the need for plus at near
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1. LOW AMPS
2. ESO at near 3. LOW PRA 4. HIGH LAG on MEM 5. asymmetry in NRA/PRA (greater NRA relative to PRA) 6. new myopic Rx showing ESOPHORIA |
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it terms of emphasis what should you consider in accommodative VT
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amplitudes BEFORE speed of response
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what is the objective of lens sorting therapy
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1. monocular
2. develops awareness of stimulating and relaxing accommodation 3. teaches voluntary control over accommodation 4. can demonstrate to patient size and distance changes with the lenses |
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what is the FINAL STEP of lenses sorting (monocular)
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to have the patient sort the lenses from what makes them feel more relaxed, to what make them feel more strained
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what are the MONOCULAR tests you can do in VT for ACCOMMODATION
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1. develop rapport
2. lens sorting 3. N/F hart chart 4. MAR *amplitudes before reaction time *emphasize the feeling of stimulation then relaxation |
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what are the BIOCULAR tests you can do in VT for ACCOMMODATION
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1. red/red rock: starts with +/- 1.00 combo
2. biocular loose lens rock this step may be skipped depending on level of suppression |
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what are the BINOCULAR tests you can do in VT for ACCOMMODATION
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1. binocular accommodative rock
2. binocular N/F hart chart |
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what is pathological diplopia
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1. diplopia of a fixated target
2. occurs in strabismic patients that have little or no suppression 3. image of the non-fixating eye falls on non macular point |
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what is physiological diplopia
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1. occurs in normal binocular vision
2. non fixated objects stimulating non corresponding points are diplopic 3, suppression of diplopic objects are psychological |
