Manifest Refraction

Clinical Pearls

This is how we determine a patient's glasses Rx and also see how much we can improve their vision in general
If a person will not pinhole past a certain number, it is very unlikely you will be able to refract someone better than what they pinholed at
Autorefraction can be very accurate in a healthy eye, but likely will need some adjustments if they have cataracts
Be sure to check the lenses as mascara can smudge them and blur the patient's vision. Check for this if you put in the proper Rx into the phoropter, but the patient states it is blurry
This video is great at the concepts, but it does some things that we will not do here

Refracting The HEA Way

First, make sure the patient is in a comfortable position
Input the last refraction into the phoropter (if we don't have this, use the AR or glasses Rx. Use the AR if the glasses are old)
Unlock the arm on the tower and bring it to the patient's face. Keep one hand on the phoropter so it won't jump up from the spring tension, and then lock it in place
Make sure their pupils are in the center of each lens opening & adjust the pupillary distance if needed
Go behind the patient and from their viewpoint, make sure the phoropter is in line with the Snellen chart
Occlude OS, and open OD (remember, refract one eye at a time!)
Shut the room lights, but make sure the tower light is on

Tips

Make sure your head is not in the way of the phoropter and the Snellen chart!
If a person is not sure of a lens making vision better or worse, do not make any changes!
Only make a change if they are definitely sure that one lens is better than the other!
Try to change between the lenses quickly. If you do it slowly, it is more difficult for the patient to tell the difference between them
Remind them to keep blinking normally as some people have a tendency to keep their eyes open. This will dry out the cornea and makes things more blurry

Pro Tip

"Counting Clicks" is a useful trick and is similar to counting money (a quarter is 25 cents). Every click on the phoropter is .25 diopters. if you start on +3.25 diopters and go down 3 clicks, how many diopters do you have now??????

Go to the Snellen line that the patient could read clearly and instruct the patient to focus on one particular letter
Tell the patient that you are going to change some lenses now and try to make the letter more clear for them
Using the weak sphere dial, call the lens you started on as #1 and go up by +.25 diopters and then call the lens you changed it to as #2
If # 2 was more clear, go up by another +.25 diopters and see if this is also better.
If #2 was more blurry, go back to #1. Now try going down -.25 diopters and see if going myopic is better for the patient
Try not to correct more than +/- .75 diopters now as we don't want to overcorrect

The following is is the most difficult concept with regards to refraction. It usually takes a few times to understand this!
The JCC is nothing more than a guide that tells you what corrections to make to the cylinder axis & power!
Notice there are two As and two Ps on the cylinder and they are in a straight line (older models sometimes don't have As on them, but just be aware they are located below the disc where you flip the lens back and forth)
When the As are in line with the arrows on the axis knob, the JCC is configured to correct the cylinder axis (A= Axis)
When the Ps are in line with the arrows, the JCC is configured to adjust the cylinder power (P=Power)
You should feel them click in place when changing between A and P
Pay attention to the red dots on the JCC; these are essential to correcting the cylinder!!

Put the Jackson Cross Cylinder (JCC) in front of the patient's eye
Make sure the As are in line with the arrows on the axis knob
Tell the patient you are going to change a different lens, and as before, give each lens a number the patient can pick as to which is clearer
The end point here is when they can't tell a difference between lens #1 or #2 (or minimal difference)
The farther away you are from the patient's actual axis, the bigger difference between the lenses they will see (1 lens will be very blurry, and 1 will be very clear)
When it gets difficult for a person to tell the difference or it is minimal, you are very close!

Here is where you CHASE THE RED!

Based on what the patient prefers, you turn the axis knob in the direction the red dot is relative to the As
Make your starting lens #1, and the next lens #2
If the patient prefers the lens where the red dot is on the left of the A, turn the axis knob to the left by 5-10 degrees
If they prefer the lens where the red is to the right of the As, turn the knob to the right 5-10 degrees

Note

We are done when the patient can't tell a difference (or barely) between #1 and #2 (remind the patient of this)
If you overshoot in a direction, make smaller corrections the opposite direction

Now turn the JCC so the Ps are in line with the arrows on the axis knob
As before, assign lenses #1/#2 to the patient
When the red dot lands on the P (pt says this is more clear): ADD -.25 diopters of cyl power
When the white dot lands on the P (pt says this is more clear): SUBTRACT -.25 diopters of power

Note

We are done when the patient goes back and forth between 2 lenses constantly (most likely).
or a patient can't tell much further of a difference
In either case, go with the lower value

Now that we have corrected the astigmatism, make one last correction to the spherical power as things will be more clear now
Remove the JCC
Go up or down +.25/-.25 diopters and see if this helps, but do not correct past this
Recheck vision on the Snellen chart and record BCVA for OD now with the new correction
Also input the final refraction into NextGen before you check NV

Now occlude OD, and follow the same procedure for OS!

Turn the room lights back on
Insert the near vision rod and tighten it to the phoropter
Make sure you are on the Snellen with the big E at the top
Put the card at 16" distance
Converge the optics for NV
Shine the tower light on the card to aid the patient
Add +2.50 to both eyes together by turning the strong cylindrical knobs inward (adding +3.00 diopters) and then take away .50, which will put you at +2.50 for each eye (+2.50 is a good starting Add power for older people)
Ask the patient if they can read the bottom line. If it is nice and clear, then stop
If not, then do the same #1/#2 process as before with the NV, but change both eyes together
Record the final add power and you are all done with the refraction!

Have the candidate walk you though all parts of the phoropter and what they do

Test if candidate can bring phoropter to a patient's face, line up properly, and lock it in place
Pupillary distance knob
Leveling knob
Convergence levers
Open / Occluded knob
Forehead distance adjuster
Weak sphere dial (+.25/-.25 diopters)
Strong sphere dial (+3.0/-3.0 diopters)
Cylinder Axis knob & scale
Cylinder power knob * scale
Jackson Cross cylinder unit (axis & power)
Reading rod, card, & holder

What do we do if the patient prefers

What do we do if the patient prefers

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