accommodation and indirect fusional

Relative accommodation

the total amount of accommodation which the eyes can exert, both relax and stimulate, relative to the vergence system.

Negative relative accommodation (NRA)

the patient's ability to relax accommodation relative to the vergence system

plus, relaxation, PFVBO

During NRA, (plus or minus) lenses are used and (stimulation or relaxation) of accommodation is required to make the target clear. Additionally, (PFVBO or NFVBI) is required to keep the target single.

Positive relative accommodation (PRA)

the patient's ability to stimulate accommodation relative to the vergence system

minus, stimulation, NFVBI

During PRA, (plus or minus) lenses are used and (stimulation or relaxation) of accommodation is required to make the target clear. Additionally, (PFVBO or NFVBI) is required to keep the target single.

blur

indicates the end of fusional reserves and the recruitment of accommodation (relaxation or stimulation) to keep the object single

double

indicates the end of both fusional reserves and accommodation

NRA

should you start with NRA or PRA first to avoid inducing accommodative spasm?

accommodation is limiting

At the end of NRA/PRA, if you occlude one eye and the image remains blurry what does this mean?

vergence is limiting

At the end of NRA/PRA, if you occlude one eye and the image clears what does this mean?

2.50 D

what is the expected value for NRA?

45% of the accommodative amp

what is the test distance for accommodative facility?

30% of the accommodative amp

what is the flipper value for accommodative facility?

32 cm

If a patient has an accommodative amp of 7D, what is the test distance to perform accommodative facility?

+/- 1

If a patient has an accommodative amp of 7D, what is the flipper that should be used to perform accommodative facility?

subjective

what is one disadvantage to accommodative facility testing?

accommodation

While performing accommodative facility testing, if the patient struggles even monocularly, what system is limiting?

vergence

While performing accommodative facility testing, if the patient improves monocularly, what system is limiting?

10-13 cpm

what is the normative value for BAF?

12-17 cpm

what is the normative value for MAF?

AC/A ratio

the amount of accommodative convergence (in prism diopters) evoked by 1 diopter of accommodation. A fundamental aspect of an individual's oculomotor system.

Calculated AC/A

method of finding AC/A ratio by measuring the change in vergence related to the change in accommodation when fixation is altered from one distance to another

Gradient AC/A

method of finding AC/A ratio by measuring the change in vergence related to the change in accommodation by holding the distance of the target constant, but change the lenses in from of the eyes to change the magnitude of accommodation.

4-6 prism diopters

what is the normative value for AC/A ratio?

presbyopic

AC/A ratio has little value for patients who are...

larger

Because calculated AC/A takes into account proximal convergence, it estimates a (smaller or larger) AC/A

smaller

Because modified gradient AC/A takes into account lag of accommodation, it estimates a (smaller or larger) AC/A

high

A high or low AC/A results in MORE ESO AT NEAR

low

A high or low AC/A results in LESS ESO AT NEAR

Accommodation

The process by which the optical system of the eye varies its focal length in response to visual stimuli by changing the dioptric power of the crystalline lens.

ciliary muscle contracts

ciliary rings moves forward and inward

posterior zonules contract

anterior zolunes relax

lens becomes more spherical increasing in plus power

five steps of accommodation

blur

the initial stimulus for accommodation

retinal cones

during accommodation, defocus stimulates these cells

LGN and visual cortex

during accommodation, after retinal cones are stimulated by blur the signal travels to...

sensory blur signals

during accommodation, after blur reaches the LGN and visual cortex, cortical cells generate...

cerebellum and parietotemporal areas

sensory blur signals generated by cortical cells are transmitted to these areas for processing

midbrain and EW nucleus

after being process in the cerebellum and parietotemporal areas, sensory blur is transmitted to these areas for the formation of motor commands

ciliary muscle via CN 3, ciliary ganglion, short ciliary nerve

name the three sequential destinations of motor commands comming from the midbrain and EW nucleus to cause ciliary muscle contraction

traumatic brain injury

Because accommodation is highly depended on cortical processing, it is often affected by

Tonic accommodation

residual accommodation present in the absence of a blur stimulus. Reflects baseline innervation from the midbrain to the ciliary muscle. Only measurable using special devics in a totally dark room. A typical amount of 1-2 D that reduces with age.

Reflex accommodation

automatic adjustment of accommodation in response to small amounts of blur input (less than 2 D). The largest and most important component of accommodation.

Vergence accommodation

accommodation induced by the neurological linking to fusional vergence. Give rise to the convergence accommodation/convergence ratio The second most important component of accommodation.

Proximal accommodation

accommodation triggered by the influence or knowledge of a near object within 3 m.

Amplitude of accommodation

the full range of accommodation from the far point (minimum accommodation) to the near point (maximum accommodation). If the far point is at infinity (emmetrope or fully corrected ametrope), this value is each to the dioptric value of the near point.

3 months

amplitude of accommodation increases rapidly in the first ____ of life.

6 months

at what age does accommodation become adult like?

55-60 years

around what age does amplitude of accommodation reach zero?

Depth of field

the extent to which an object can be moved toward or away from the patient and still remain in focus

smaller

Depth of field is increased in patients with(smaller or larger) pupils, increasing the amplitude of accommodation

medication use

Pupil size is commonly affected by

monocularly

Accommodation is tested _____ to negate the stimulus of convergent eye movements.

put the far point at infinity

why must habitual rx be worn by the patient during amplitude of accommodation testing?

9.50 D (do not forget to add working distance 40 cm, 2.50 D)

Starting lens: +0.75

After minus lens build up: -6.25

What is the amplitude of accommodation?

high

Uncorrected myope will have an artificially (high or low) amplitude of accommodation

low

Uncorrected hyperope will have an artificially (high or low) amplitude of accommodation

over

Push up method (over or under) under amplitude of accommodation because the target gets larger and easier to see as it gets closer to the patient

under

Minus lens build up method (over or under) estimates amplitude of accommodation because minus lenses minify the target making it more difficult to see

pull away

what is the best method of choice for measuring amplitude of accommodation?

15-0.25(age)

what is the equation for minimum amplitude of accommodation?

18.5-0.3(age)

what is the equation for the average amplitude of accommodation?

25-0.40(age)

what is the equation for the maximum amplitude of accommodation?

double

In order for a patient to focus compfortable up close, the amplitude of accommodation should be ______ the accommodative demand.

Accommodative accuracy

the behavior of the patient's accommodative system when an actual near task is being carried out

Lag

less accommodation than what is needed is being employed initially. It is normal for there to be a lack of accommodative response of about 0.50 D

Lead

more accommodation than what is needed is being employed initially

lead (due to pupil constriction and increased depth of focus)

very dim lighting during FCC is important to avoid measuring an artificial...

plus, lag

During FCC, what lens is needed if the horizontal lines appear clearer first? Does this represent a lag or a lead?

minus, lead

During FCC, what lens is needed if the vertical lines appear clearer first? Does this represent a lag or a lead?

harmon distance

distance from middle knuckle to elbow. Used for determining working distance when performing MEM on children.

plano to +0.50 lag

what is the normative value for FCC?

plano to +0.75

what is the normative value for MEM retinoscopy?

accommodative insufficiency

low muscle tone of ciliary body

presbyopia

high ESO with little NFV

a large lag of accommodation can indicate these four conditions

accommodative spasm

accommodative excess

large EXO with little PFV

A large lead of accommodation can indicate these three conditions