line test

[RFC1873]

I had my first medical a couple of days ago and one of the vision tests that I had to do was I held a little device (it almost looked like a small magnifying glass and the opening was red) up to my eye while keeping the other open and I had to turn the dial until the line I saw was covering the light the doctor was holding. I was just wondering what this tests.

Thanks

[Weekendwarrior]

I believe it is to test your depth perception.

[My Flight Surgeon]

This is the Maddox rod test. This test is used to uncover latent squints (phorias). A phoria is a latent deviation. This means that the deviation is not apparent unless fusion is broken. For the phoric patient, the natural resting position of the eye muscle system is not ortho (straight). When the patient is visually active (i.e. awake and alert) the power of fusion keeps the eyes straight. If fusion is broken by dissimilar visual targets, (e.g. the Maddox Rod test), then the eyes move to their natural resting positions.
The Maddox rod is a disc of red glass in which are molded grooves. When a distant spot of light is viewed with the disc in front of one eye, a red line will be seen by the eye covered with the lens, whilst a spot of light will be seen with the other eye. The line will be at right angles to the grooves to that when these are horizontal the line will appear vertical. A candidate with no latent deviation will see the coloured line pass through the spot of light (orthophoria), whereas a candidate with latent squint will see the light source to one side of the line.
The Maddox rod with rotating prism is held in front of the right eye and the candidate is asked to look at a point source of light 6m (20 ft.) away in a darkened room. Both eyes must be open and squinting should be avoided. The candidate is asked which side of the line the dot is seen. If it is to his right, esophoria is present and if to the left, exophoria. The candidate is then asked to “put the line on the light” by adjusting the rotating prism. The examiner reads off the degree of phoria from the scale on the device.
The test is repeated with the disc turned to the vertical position. The light will now be seen either above or below the line and may be adjusted by the candidate in the same way. If the red line is above the light there is left hyperphoria, if below the light, right hyperphoria.

We only do the test for phorias on Class 1 and 2 exams. It is not required for Class 3.

[My Flight Surgeon]

My wife (Dana) tells me I need to do this in English

Phorias are conditions when you look at a target, one eye is dominant and looks directly at the target while the other eye will look slightly to the left or right of the target. The Maddox rod test helps identify this condition. One then places a prism (or several prisms) in front of the eye to bring the objects together so they are one. This prism measured in diopters is the way we report the phoria. Many AME's use a vision testing machine with this function built into the machine. The FAA has no hard standards for the values but they want to know that with 6 diopters or more there is no evidence of diplopia or serious eye pathology and all other aspects of the examination are favorable.

[RFC1873]

Thanks for the translation

[CaptChris]

Originally Posted by My Flight Surgeon

We only do the test for phorias on Class 1 and 2 exams. It is not required for Class 3.

I've ALWAYS had a problem with phoria tests. One AME made me go to an eye doctor and get a special form filled out. I guess it was within limits because he issued me my 1st class. Should I maybe bring the eye evaluation form to all of my 1st class medicals (filled out by my optomotrist)? Would that get me "out of the test?"

[My Flight Surgeon]

The FAA wants the value 6 or less. If it is more than 6, they just want to know you do not see double.

If you go to an AME who is not satisfied with the initial evaluation and gives you the run around, then yes, take the 8500-7 from the eye doctor to the flight physical.