Subjective Refraction

Question 1

What is the purpose of subjective refraction?

Answer 1

To determine the refractive state of the eye subjectively by combining lenses to place the far point of the eye at infinity, with accommodation relaxed

Question 2

Why do we fog?

Answer 2

To ensure that accommodation is relaxed

Question 3

How do we fog?

Answer 3

Create an artificially myopic eye by placing plus lenses in front and ensuring the image formed is in front of the retina

Question 4

What is a stimulus for accommodation?

Answer 4

Blur

Question 5

2 consequences if fogging is not done

Answer 5

Subjective refraction results in insufficient plus or excessive minus power
Asthenopia with extended near work

Question 6

Asthenopia

Answer 6

Eye strain

Question 7

End point criterion

Answer 7

Maximum plus power for maximum acuity

Question 8

Circle of least confusion

Answer 8

Center of the conoid of Sturm located at the dioptric midpoint between the horizontal and vertical focal lines

Question 9

When/why do you use astigmatic charts

Answer 9

To determine cylindrical component of refractive error when 20/25 or better cannot be achieved with net retinoscopic findings, another subjective test under monocular conditions

Question 10

What are the two types of astigmatic chart?

Answer 10

Fixed and rotating

Question 11

What kind of chart is the clock dial?

Answer 11

Fixed

Question 12

What kind of chart is the paraboline chart?

Answer 12

Rotating

Question 13

What is the rule of 30?

Answer 13

The smaller of the two clock hours reported by the patient is multiplied by 30 to determine the cylinder axis

Question 14

How would WTR astigmatism respond to clock dial test?

Answer 14

12 and 6 o’clock would be sharpest

Question 15

How do you find the power of cyl using clock dial?

Answer 15

Collapse the conoid of Sturm which makes the opposite spokes become clearer

Question 16

What is the end point goal of clock dial?

Answer 16

When the patient reports that all of the spokes are equally distinct

Question 17

What are the 3 reasons to do JCC?

Answer 17

Refine axis and cyl subjectively
Refine objectively determined astigmatic corrections from keratometry/ret
Refine subjectively determined astigmatic corrections from charts

Question 18

What is the JCC lens?

Answer 18

Minus cyl on one side and plus cyl on the other with axes 90 degrees apart in powers of +-0.25

Question 19

What must be done prior to JCC testing?

Answer 19

The spherical lens power that gives the best VA is placed in front of the eye and remains there throughout

Question 20

True or False: JCC can be tested under fogged conditions

Answer 20

False, never (lol)

Question 21

What are the 4 functions of JCC?

Answer 21

Analysis, diagnosis, treatment, prognosis

Question 22

9 factors that influence subjective refraction

Answer 22

Case history
Intelligence
Discrimination
Accommodative status
Personality
Health
Age
Past experience
Interaction with doctor

Question 23

Purpose of monocular subjective refraction

Answer 23

To determine monocular best sphere and to refine axis and cylinder

Question 24

Three basic steps of monocular subjective refraction

Answer 24

Sphere check (MPMA)
JCC
Second sphere check

Question 25

Which dots are the minus cylinder part of the JCC?

Answer 25

Red

Question 26

Two basic steps of binocular subjective refraction

Answer 26

Balance the accommodative stimulus and finalize the sphere power binocularly

Question 27

When is prism dissociated blur balance not performed?

Answer 27

When the patient is presbyopic

Question 28

In which eye do you add +0.25D to during the prism dissociated blur balance test?

Answer 28

The eye they report to be least blurry

Question 29

What is the purpose for the prism blur balance test?

Answer 29

To prevent unequal or excessive accommodative effort between the eye’s to prevent asthenopia

Question 30

What is the end point of the prism blur balance test?

Answer 30

Equally blurry lines