Accomodation Flashcards
What is the accommodative system?
Focusing of the eye
What is the oculomotor system?
How the two eyes work together
What is functional evaluation?
Evaluation of the accommodative and oculomotor systems
What is accommodation?
The adjustment of the dioptric power of the eye beyond its static resting power brought about by a change in the shape of the crystalline lens
What is the stimulus to accommodation?
An out of focus retinal image or blur
What is the near triad?
Accomodation increase
Miosis
Convergence
What is tonic accommodation?
Resting or passive state in the absence of accommodative stimulus
When is the eye in tonic accommodation?
In complete darkness or looking at a bright empty field
What does an emmetropic eye become in tonic accommodation?
Myopic
What causes accommodation to a more distant stimulus from resting state?
Sympathetic response to blur
What causes accommodation to a more near stimulus from resting state?
Parasympathetic response to blur
How can you stimulate accommodation?
By placing the object at a distance closer than infinity
By using minus lenses
By using a combination of distance and lenses
With an object at 40 cm from the spectacle plane, what is the stimulus to accommodation?
2.50D
What is a haploscope?
Instrument that measure accommodative response
How is the accommodative response described clinically?
With regard to the dioptric accommodative stimulus
Amplitude of accommodation
Maximum amount of accommodative power an eye can exert measured in diopters
Facility of accommodation
Ability of the eye to quickly and aaccurately shift the accommodative posture
Lag of accommodation
The distance in diopters between the object of regard and the actual current position of accommodation
What is the considered norm of lag of accommodation?
The accommodative response to be less than the accommodative stimulus (demand)
Range of accommodation
Linear distance in cm over which one’s accommodative power allows maintenance of clear vision, from the near point to the far point
T/F Range of accommodation is alwasy real
False, uncorrected hyperope will have a partially virtual range
Presbyopia
Refractive condition in which the accommodative ability of the eye becomes insufficient for satisfactory near vision without the use of corrective plus lenses
When is accommodative testing not done?
On presbyopes or when the refractive error is not maximally corrected
What are the 4 tests for evaluating amplitude of accommodation?
Hoffstetter’s formulas
Donder’s age referenced table
The push-up test
Minus lens to blur test
Hoffstetter’s formulas
Minimum: 15-0.25xage
Average: 18.5-0.30xage
Maximum:25-0.40xage
What is the gold standard for evaluating amplitude of accommodation?
The push-up test
How much greater are the binocular amplitudes compared to the monocular amplitudes on average for the push up test?
0.50D
What is the near point of accommodation?
A linear measurment from the stoppedd position of the push-up stick to the patients spectacle plane
When do you stop moving the push-up stick closer?
When the letters become and remain blurry
What is the minification factor?
The letters for the minus lens to blur test get smaller due to the increase in minus lenses and a stationary target
What is the difference in amplitde of accommodation between the push-up test and the minus lens to blur test?
2D less for the minus lens test
What is the endpoint for the minus lens to blur test?
First sustained blur when the target cannot be cleared
What is the total amplitude of accommodation from the minus blur test?
Amount of minus lenses added plus the accommodative demand for the near point card (2.50D)
What are the two methods for evaluating the facility of accommodation?
The lens flipper test
The near-far test
What is the gold standard test for facility of accommodation testing?
The lens flipper test
What is the normal expected result from the lens flipper test?
6 cycles in 30 seconds or less
Why is the near-far test not the gold standard?
Because most rooms are not long enough to completely facilitate relaxed accommodation
What is the normal expected result from the near-far test?
10 cycles in 30 seconds or less
What is the most common way to evaluate lag of accommodation?
Dynamic retinoscopy testing
What are the three tests for evaluating lag of accommodation?
Nott retinoscopy
Monocular estimation method retinoscopy
Bell retinoscopy
What is the expected normal finding for lag of accommodation?
+0.50 and symmetric
What do findings greater than +0.50D of lag indicate?
Lazy accommodative demand or high lag
What do findings of less than +0.50D of lag indicate?
Low, zero, or negative lag or a tight accommodative response
What do asymmetric lag findings indicate?
Refractive or healh etiology
How do you record positive lag of accommodation for Nott retinoscopy?
With motion is initially noticed, move back until neutral and measure dioptric distance with near point rod
How do you record “no” lag of accommodation for Nott retinoscopy?
Neurality is initially noticed inidicating that the accommodative response is equal to the accommodative demand
How do you record minus lag of accommodation for Nott retinoscopy?
Against motion is initially noticed, move forward until neutral, do not record magnitude because any minus lag needs to be remedied
What is the retinoscopic test of choice for behind the phoropter?
Nott retinoscopy
What is the retinoscopic test of schoice for outside of the phoropter?
MEM retinoscopy
What makes depth of focus greater?
Smaller pupil or larger object
How can the patient see the target clearly when the accommodative response does not equal the accommodative demand?
Depth of focus can make up for the lag of accommodation
What is the difference btween depth of focus and depth of field?
Fous is for the retina and field is for object space
What are the two methods for evaluating the sustaining ability of accommodation?
Amplitude of accommodation decay test and facility of accommodation decay test
