Bracketing for Trial Frame Refraction

What is the purpose of bracketing in trial-frame refractions?

To include or exclude possible endpoints and establish boundaries for lens choices.

What does JND stand for in the context of trial-frame refractions?

Just Noticeable Difference.

How is JND expressed?

As power (D).

What happens when choices are less than the JND?

The patient will likely say the options are 'the same'.

What does it mean when a patient says 'same' during a refraction?

It indicates that the two choices presented are equidistant from the endpoint and the patient cannot detect a difference.

What is the significance of the denominator of VA taken at 20 ft?

It is divided by 100 to estimate JND.

What is the expected change in power during initial sphere adjustments?

Expected change is typically around 2 times the JND.

What is the initial sphere adjustment for a 78-year-old patient with 20/200 vision?

The sphere power must be changed either positively or negatively based on visual acuity.

What is the role of cylinder power in initial sphere adjustments?

Cylinder change needs sphere power to 'double click' for effective adjustments.

What is the definition of bracketing in optometry?

Bracketing involves establishing boundaries with choices greater than JND to ensure proper lens selection.

What intervals are recommended for initial sphere adjustments?

Intervals should be ≥ 0.75 DS to avoid sacrificing accuracy.

What is the effect of small intervals during refraction?

Small intervals do not effectively bracket and can lead to inaccurate adjustments.

What should be done if the starting point is -5.00 DS and the patient chooses -0.50 DS?

The sphere must be changed to -5.50 D.

What is the placebo effect in the context of lens comparisons?

Patients may perceive a change as better when comparing one lens to no lens, leading to biased results.

How can the placebo effect be avoided during refraction?

By combining +0.50 DS and -0.50 DS to create a no power comparison.

What does 'same' mean for an absolute presbyope during initial sphere adjustments?

It indicates that the midpoint of the lens choices is perceived as equivalent.

What is the significance of visual acuity (VA) in determining JND?

JND depends on the patient's visual acuity and may decrease if their VA improves during refraction.

What is the expected change in power for absolute presbyopes?

Expected change is typically around 1.00 D, especially when considering JND.

What is the impact of accommodation on lens choices for young patients?

Young patients may experience changes in accommodation that keep the image on the retina, affecting their lens choice.

What does JND stand for in optometry?

Just Noticeable Difference

What is the formula for JND?

JND = 0.50 D

What is the standard interval used in refraction?

1 D

What does 'Habitual' refer to in the context of refraction?

-1.00 DS

What is the endpoint for a refraction with a +0.25D adjustment?

+0.25D

What is the significance of 'same power chosen twice' in refraction?

It indicates that the power was consistent and helps establish a midpoint.

What is the recommended starting point for a young patient with lots of accommodation?

Plano DS

What does 'straddle midpoint of bracket' mean?

It refers to choosing a power that is equidistant from the midpoint in a bracketing process.

What is the purpose of using a bracket in refraction?

To find the limits of the patient's visual acuity and refine the prescription.

What does it mean if a patient has a 'poor first presentation'?

It indicates that the initial power choice may not be optimal for the patient's vision.

What is the significance of the term 'critical thinking' in the context of refraction?

It is necessary for determining appropriate adjustments and understanding patient responses.

What does VA stand for in optometry?

Visual Acuity

What is the effect of choosing a power that is too strong for a young patient?

They may end up over-minused by 0.25 D.

What does 'bracketing axis' refer to?

The process of adjusting the axis of a cylindrical lens to refine the prescription.

What should be done if the axis is placed at a midpoint of 32°?

You cannot add minus power if it is necessary to improve visual acuity.

What is the maximum deviation of the axis in a bracketing process?

The most that the axis is off is 1°.

What is the purpose of the final sphere in refraction?

To remove any over-minus and maintain best-corrected visual acuity.

What is the importance of practicing refractions?

To master the concepts of optics, JND, and bracketing.

What does 'courtesy click' refer to in refraction?

An intentional act to over-minus the prescription.

What is the significance of using smaller intervals in refraction?

It allows for more precise adjustments and can specify endpoints.

What does it mean if a patient responds 'same' during a JCC test?

It indicates they perceive no difference in visual clarity at the tested axes.

What is the recommended action if a patient has 20/20 VA with a 2 DC?

Change the axis by 15°.

What does it mean if the axis must be greater than 15°?

It indicates that the axis change should not include 15°.

What is the relationship between axis changes and visual acuity?

Changes in axis should correlate with the patient's visual acuity and cylinder magnitude.

What is the importance of analyzing incoming information quickly during refraction?

It helps in making timely adjustments to the prescription based on patient feedback.