OTM II Midterm - Subjective Refraction, Binoc Bal, Add Determination

refractive error

If visual acuity is down at distance OR near then it is most likely due to refractive errorIf visual acuity is down at distance OR near then it is most likely due to...

pathology

If visual acuity is down at both distance AND near then refractive error is possible, but could also be ________. Pinhole!

0.25

in simple myopia, each line missed during VA measurements is roughly how many diopters of minus sphere?

sph + .5cyl

Calculation for spherical equivalent

-3.50

what is the spherical equivalent for this rx? -3.00-1.00x180

no (too complicated due to their ability to accommodate at distance)

is it possible to estimate refractive error for a hyperope based off of VA measurements?

0.25-0.50

about how many diopters is each line missed at near for a presbyope?

WTR

Astigmatism type impact on VA from least to greatest. Oblique, WTR, and ATR

Lens effectivity

change in vergence of light occurring at different points along a path. Ie) moving a lens further or closer to the eye varies the power incident on the cornea

minus

does moving glasses closer to the eye introduce more plus or more minus power?

plus

does moving glasses further from the eye introduce more plus or more minus power?

Just noticeable difference

amount of optical change at which a difference in clarity or blur should be appreciated.

2 lines larger than BVA

what is the target of axis and power refinement during monocular subjective refraction?

15, 5

During axis refinement for a patient with >2 D cyl, you begin by turning the knob _____ degrees at a time. When the patient begins to move in the opposite direction, move ____ degrees at a time.

5, 1

During axis refinement for a patient with 2+ D cyl, you begin by turning the knob _____ degrees at a time. When the patient begins to move in the opposite direction, move ____ degrees at a time.

reach an axis already tested

patient replies same

two end points for axis refinement

red

when refining the axis, do we chase the red or white dot?

red

which dot when aligned with the P on the JCC indicates to add 0.25 D minus cyl?

add +0.25 sphere

what must you do when you add -0.50 cyl during power refinement?

add -0.25 sphere

what must you do when you take away -0.50 cyl during power refinement?

interval of sturm

region between the horizontal and vertical line foci in an astigmatic system.

Circle of least confusion

the dioptric midpoint between the horizontal and vertical line foci in the center of the interval of Sturm. The closest thing to a point image on the retina for an astigmatic eye.

in front

Fogging an astigmatic patient will move the interval of Sturm in (front or behind?) the retina. Which line foci appears clearer for the patient will depend on the type of astigmatism that patient has.

vertical lines

do vertical or horizontal lines appear clearer for a patient with WTR astigmatism?

horizontal lines

do vertical or horizontal lines appear clearer for a patient with ATR astigmatism?

put circle of least confusion on the retina

in terms of interval of sturm and CLC, what is the goal of sphere refinement?

more myopic

During cylinder axis refinement the red dot is oriented more closely with the principal meridian that is more (myopic or hyperopic?). This position minimizes the circle of least confusion to improve VA.

collapse the interval of sterm on the retina

in terms of interval of sturm and CLC, what is the goal of cylinder power refinement?

Binocular balance

a test performed because sometimes accommodation can become unequal between the two eyes during refraction. More common for hyperopes. Perform when 1 or less line difference between the two eyes BVA. Less useful for presbyopes because they do not accommodate.

2 lines larger than BVA

what is the target for prism dissociation method of binocular balance?

3 BD OD, 3 BU OS

what is the prism set up for prism dissociation method of binocular balance?

alternate occlusion

If during prism dissociation method of binocular balance the patient cannot see double, this test can be performed to achieve binocular balance.

red

during duochrome binocular balance, if the patient does not respond "same" you should always leave them one click in the (red or green). This indicates that they are slightly underminused, otherwise you will overminus them.

2 lines larger than BVA with red green filter

what is the target for monocular duochrome?

3 BD OD, 3 BU OS

what is the prism set up for binocular duochrome?

whole chart with red green filter

what is the target for binocular duochrome?

Donders-Duane-Fincham Theory

muscle based theory of presbyopia. States that age related loss of accommodation is due to the ciliary muscle changes, not the condition of the lens. Accounts loss of accommodation to progressive weakening of ciliary muscle contraction.

Presbyopia

reduction in maximal accommodation amplitude sufficient to cause symptoms of blur and ocular discomfort at the near working distance that occurs naturally with age. Is irreversible. Occurs around 40-45 years of age.

Helmholtz-Hess-Gullstrand Theory

lens based theory of presbyopia. States that age related loss of accommodation is due to changes in the condition of the lens, not the ciliary muscle.

decreased elasticity of lens capsule

decreased elasticity of lens substance

lens gets larger

three lens changes during presbyopia

anteriorly

Lens shifts (anteriorly or posteriorly?) with growth. This reduces the capability of the zonular fibers to effectively pull on the lens

lower

Number of zonular fibers becomes (higher or lower?) and they become more fragmented

Accommodation

process by which the optical system of the eye varies its focal length in response to visual stimuli. Changes in dioptric power of the crystalline lens to focus an object on the retina.

contract, relax

During accommodation, the posterior zonules _____

anterior zonules _____. (answer with contract or relax)

Amplitude of accommodation

maximal accommodative level, closest near focusing response, that can be produced with maximal voluntary effort in the fully correct eye.

2

Patients should be able to accommodate how many times their accommodative demand to function without symptoms?

3, 2.50, 5, yes

If a patient is blurred at 33 cm, the amplitude of accommodation available is _____ D.

At 40 cm, accommodative demand is ___ D. Therefor, the amplitude of accommodation needed for the patient to feel comfortable is ____ D. Will the patient have symptoms at 40 cm?

+0.75 D

What is the age expected norm tentative add for a patient who is 40?

+1.00

What is the age expected norm tentative add for a patient who is 45?

+1.50

What is the age expected norm tentative add for a patient who is 50?

+2.00

What is the age expected norm tentative add for a patient who is 55?

+2.25

What is the age expected norm tentative add for a patient who is 60?

age expected norm

tentative add determination method used for patients 60 years or younger with a working distance of 40 cm.

plus build up

tentative add determination method that is a subjective measure of the least amount of plus needed for clear and comfortable near vision. Focus on near card with distance rx. Slowly add +0.25 OU at a time (WITH IMPROVEMENT) until the patient can see 20/20. Do not overplus, because this will shorten their working distance. Can be done monocularly when accommodation is unequal between the two eyes due to organic issues (IOL only in one eye).

amplitude of accommodation

tentative add determination method useful for patients below 55 years of age. Not typically used clinically, usually used for research.

fused cross cylinder

What does FCC stand for? Method sometimes used for tentative add determination.

NRA PRA

Procedure used to refine the tentative add. Achieved by measuring the amount of plus (NRA) or minus (PRA) needed to blur or double a near target.

(NRA + PRA/2) + tentative add

equation of final add given NRA, PRA, and tentative add

+1.50 D

if the tentative add is +1, NRA is measured to be +2 and PRA is measure to be -1. What is the final add?

range of clarity

procedure used to refine the tentative add done by measuring the furthest and nearest blurry point for the patient. Adding +/- 0.25 D will equal the range from 16 in on both sides.

add -0.25 D (to shorten the working distance)

During range of clarity if the near distance is further from 16 in, what do you do before repeating the procedure?

add +0.25 D (to lengthen the working distance)

During range of clarity if the far distance is further from 16 in, what do you do before repeating the procedure?

take VAs with near rx

trial frame near rx

educate the patient

three steps to finalizing an add after it is measured

out

Spectacle corrected hyperopes have reduced accommodative amplitudes due to base (in or out) prism effect of plus glasses. Therefore, they will show symptoms of presbyopia sooner than spectacle corrected myopes.

Small pupil size

Minimal near demand

Antimetropia

three reasons why a patients may not experience clinicial presbyopia.

incipient presbyopia

early stage of presbyopia at a normal age

Functional presbyopia

presbyopia that is symptomatic

absolute presbyopia

stage of presbyopia where there is no accommodative ability remaining at all

premature presbyopia

early presbyopia. Usually hyperopic patients. Drug related, disease related, environmental, etc.

nocturnal presbyopia

decrease in accommodative ability in dim lighting due to an increase in pupil size and decrease depth of focus.