Clinical: Astigmatic Clock

Question 1

Astigmatic clock purpose

Answer 1

To determine the axis and power of the cyl component of the refractive error by a subjective technique

Question 2

Astigmatic clock steps:

Answer 2

-occlude eye
-remove any cyl that may have been in phoropter and fog eye
-show pt clock chart
-ask pt to identify darkest, sharpest line
-use rule of 30 to determine cyl axis

Question 3

Rule of 30:

Answer 3

Take the smallest number of the line and multiply it by 30, that will be the cyl axis

Question 4

After axis is set, begin adding cyl power -0.25 at a time until…

Answer 4

All lines look the same

Question 5

Once pt reports that all lines are equally sharp and then you then…

Answer 5

Reduce the fog and perform MPMVA

Question 6

Do you have to maintain spherical equivalent during astigmatic clock?

Answer 6

No! Because they are fogged

Question 7

As you increase the minus cyl power, the first line image moves ________ the retina and the second line image _________________

Answer 7

Toward the retina, stays in place

Question 8

If you add too much cyl power on clock dial test, your will get…

Answer 8

A reversal in response because the horizontal line is now closest to the retina