Depth perception issues

[Guest Brandon]

<<removed>>

[Guest Guppyguy]

Had my FC1 saturday and all went well except I failed the OVT test but passed the Voerhoff(sp?). I understand that I now need to get further evaluation. Here are my questions:

Can I go to a civilian ophthalmologist for the follow up?

Would wearing a patch over my dominant eye for awhile help?

If I pass the follow up evaluation is it an automatic waiver?

I knew one of my eyes is dominant but was pretty flustered when I couldn't pick out all of those dots.

Thanks for any help!

Guppyguy

[Guest laurendenise28]

Hi Guppyguy,

I failed the depth perception test twice and passed it the third time, so don't lose hope! One of my eyes is dominant as well. I do not know what the test was called, but it had the black circles against a white background and I had to pick out the circle that was jumping out at me...although none really stood out too well to me...anyway, the first time I could not see any circles jumping out at me. After some vision exercises and wearing glasses instead of contacts for months, when I retook some of the circles stood out, but not all of them so I failed again. A few days later I retook with a different pair of glasses and although it was a struggle, I passed it! I can fill you in on what vision exercises I did if you would like. During my first physical I was told that you can train your eyes for depth perception and I believe it. Don't lose hope. If you want to drop me an e-mail I will help in any way I can. laurendenise28@hotmail.com

[Guest jmmp97]

Flight Doc, if you're still out there somewhere, I'm really going to need your help keeping this straight.

Told my recruiter about my trip to MEPS today. He's basically told me that failing the depth perception is a problem, and that while he'll work for a waiver he wants me to look at non-rated positions. Here's the deal -

I've been in the ANG for seven years now. I called my unit and got the results for the last two physicals that I have on file - my entrance physical in 1996 and a follow on physical in 2001. In 1996, I passed the depth perception to Block D, and in 2001 I passed it to Block E. On the MEPS test today, I couldn't get one single line right! What gives?

Given everything above, what do I do? My recruiter is telling me that even if I retake and pass that he will have to put in for a waiver that I will probably not get - if I passed the depth perception in a few weeks during an IFC1, wouldn't that suffice for the OTS Board?

I guess I'm a little confused as to what needs to be done. The cutoff date for the application is September 2nd, so any advice is welcome, and I'd love to hear from Flight Doc!

Thanks, all!

[Jkarl]

Jmp:

First thing -- your recruiter does not seem very helpful and I would look for another one.

Second.

Here is what the Manual says about failing a depth test for FC1:

A7.11. Depth Perception/Stereopsis.

A7.11.2. Flying Class I, IA, II-Flight Surgeon Applicant and III-Inflight Refueler Applicants and individuals required to perform scanner duties. Failure of the Vision Test Apparatus (VTA-DP) or its newer replacement, the Optec Vision Tester (OVT), screening depth perception test with uncorrected refractive errors should be retested with refraction correction in place, regardless of level of unaided visual acuity.

Failure even with correction is disqualifying, but may be considered for waiver consideration by higher waiver authorities, only after completion of a full evaluation by an ophthalmologist or optometrist, to include all of the following: ductions, versions, cover test and alternate cover test in primary and 6 cardinal positions of gaze, AO Vectograph Stereopsis Test at 6 meters (4 line version), AO Suppression Test at 6 meters, Randot or Titmus Stereopsis Test, Red Lens Test, and 4 Diopter Base out Prism Test at 6 meters. These tests are designed to identify and characterize motility/alignment disorders, especially microtropias and monofixation syndrome. The results of these tests done locally are considered to be preliminary, but will be used by waiver authorities to determine whether a candidate should be permanently disqualified

without any waiver consideration, to identify if there are potentially correctable causes, and to determine whether further evaluation is required.

So you will need a waiver (and can only get one if you pass the above mentioned tests). When you get it, This is what is needed for a waiver:

AFPAM-48-132

Updated-6/99

By ACS

CONDITION: SUBSTANDARD DEPTH PERCEPTION

I. Overview: The visual perception of depth or the third dimension is derived from the interpretation and integration of a number of monocular and binocular cues. As such, defects or acquired abnormalities in any portion of the visual axis may adversely affect some aspect of the perception of depth. Monocular depth perception relies on learned cues such as physical appearance of an object or the size relationship of objects. Examples of monocular cues include motion parallax and perspective. Although monocular cues to depth and distance are the primary cues utilized beyond 200m, they are subject to visual illusion. The precision of monocular depth perception is highly variable, depending on stimulus, lighting and motion of the object, but is generally accepted to be inferior to binocular depth perception (stereopsis).

True binocular stereoscopic vision (stereopsis) represents the finest level of depth determination and refers to the interpretation of depth by detection and interpretation of retinal disparity. The ability to discern depth accurately seems to develop at about 3 months of age in normal infants. However, this ability is dependent on accurate depiction of an image upon the retina of both eyes simultaneously, and upon the correct interpretation of that stimulus. Any disruption of accurate retinal imaging will adversely affect depth perception. A subset of individuals are unable to accurately perceive depth secondary to developmental abnormalities of the neuro-retinal pathway. The most common example of such a defect is childhood amblyopia (also called “lazy” eye), which includes strabismic amblyopia (a misalignment of the optic axis), anisometropic amblyopia (due to retinal image size or clarity differences from differential refraction between the two eyes) and deprivation amblyopia (from opacities or blockage of the optical media such as cataract, ptosis or uniocular retinal disorder). A subset of these individuals may have transient misalignments of the visual axis sufficient to cause strabismic suppression of one of the misaligned images across such a small portion of the visual axis as to be undetectable by the individual, and detectable only with specific testing. Similarly, however, acquired disorders, such as imperfect refraction or uniocular visual disruption from ocular conditions, such as a cataract, can adversely affect the depth perception in a previously normal individual. Sources of depth perception defects commonly seen among aviators and aviator applicants include defective ocular muscle balance, uncorrected refractive errors, microtropia, anisometropia and monofixation syndrome.

Although some defects in stereoscopic vision may be corrected with correction of the visual abnormality, individuals with corrected childhood amblyopia exhibit a high prevalence of reduced contrast perception, and even the vast majority of children who undergo correction at an early age do not ever achieve normal stereopsis.

The USAF utilizes the VTA-DP, or its newer replacement, the Optec 2300 (OVT-DP), for assessment of depth perception in aviators. Passing this test requires the ability to discern depth based on a disparity of at least 25 seconds of arc (line D), although the test is capable of testing as low as 15 seconds of arc. “Normal” stereo vision is considered to be 30-40 seconds of arc, although a few people have stereoacuity that is better than 15 seconds of arc. The limit of human stereopsis is probably around 5 seconds of arc. Verhoeff and Howard-Dolman tests are no longer used in routine screening, but they are utilized by the ACS in determining potential waiverability of substandard stereopsis cases.

II. Aeromedical Considerations. Stereopsis is generally not considered to be a factor in the perception of depth beyond 200m. Beyond those ranges, monocular cues prevail to facilitate perception of depth. In aviation, accurate perception of spacing or depth within this distance is critical in a number of situations, such as aerial refueling, formation flying, holding hover rescue type operations, taxiing, and parking. Stereopsis also facilitates closure maneuvers and rejoins. The majority of aviator tasks, dependent on the perception of depth, occur beyond 20 feet. As close proximity flying situations rarely arise in civil aviation, the FAA does not require depth perception testing for general or commercial aviation. However, military formation flying requires constant monitoring and requires normal stereoscopic/depth perception.

III. Information Required for Waiver Submission. The most common cause of an acquired depth perception defect is uncorrected refractive error. Depth perception testing should not be attempted until optimal correction has been achieved.

A. Evaluation Required for Waiver Consideration :

1. Local evaluation by an optometrist or ophthalmologist is required prior to consideration of further waiver processing to rule out correctable causes and those conditions that would preclude further consideration. The local work-up format includes at a minimum:

a) Complete direct and indirect ophthalmoscopy

B) Optimal refraction with further testing, including repeat VTA-DP or OVT-DP, to be accomplished with optical correction of any refractive errors, regardless of unaided visual acuity

c) AO vectograph

d) Red Lens test

e) Four-diopter base-out prism test

Results from these tests will be used by higher waiver authorities to determine if further processing is appropriate.

2. Aeromedical Consultation Service (ACS) evaluation is required for waiver recommendation after correction of any reversible or correctable deficits. Initial applicants may be evaluated if their defect is suggestive of microtropia or monofixation syndrome per published research protocols.

IV. Waiver Considerations . One hundred fifty two aviators with defective depth perception are recorded in the USAF WAVR database. Most were identified retrospectively. Among Class I and II aviators, all but four received waivers for substandard depth perception (most due to monofixation or microtropias), and the four who were disqualified were not primarily disqualified due to depth perception. Of 19 Class III aviators listed in the database, seven were disqualified, all primarily due to defective depth perception. Many of these were boom operators in whom accurate depth perception is also considered critical. Many of the waivered aviators, who received waivers, enjoyed highly successful military aviation careers despite subtle defects in depth perception not detected until late in their careers. However, it is not known how many student aviators may have washed out as a direct consequence of undetected depth perception problems. It is presumed that a subset of mildly defective microtopes may perform adequately in the cockpit. Therefore, a subset of initial applicants who have subtle defects in stereopsis due to microtropia or monofixation syndrome have been issued waivers as part of a prospective EFS-M research protocol. Prerequisites for inclusion in these studies have been outlined elsewhere, and requests must be coordinated through the appropriate MAJCOM.

A large body of data exists regarding the effects of night vision goggles and depth perception. Even dual tube goggles may not provide accurate depth assessment capabilities for a number of reasons including off axis adjustments, poor focussing, and poor tube performance. Depth perception in the aviation environment may be compromised after the use of cycloplegic agents.

Waiver, therefore, is possible for aviators with mildly defective depth perception in the absence of other retinal or uncorrectable ocular pathology. Individuals in aviation specialties which rely on stereoscopic depth perception for performance of assigned duties (boom operators) and aircrew with more significant deficits are less likely to receive favorable consideration. Each aircrew member is considered on a case by case basis.

V. References.

1997 Aeromedical Reference and Waiver Guide, US Navy.

Aerospace Ophthalmology VII. AMP HO 342. Ophthalmology Branch, Clinical Sciences Division, USAFSAM Brooks AFB TX.

Effects of the Chemical Defense Antidote Atropine Sulfate on Helicopter Pilot Performance: An In-Flight Study. Army Aeromedical Research Lab, Ft. Rucker AL. 1991.

Howard IP and Rogers BJ. Binocular Vision and Stereopsis. Oxford University Press, New York NY. 1995.

Patterson R and Pullman WL. Human Stereopsis. Human Factors 1992;34 (6):669-92.

Hope it helps

[ 13 August 2003, 17:18: Message edited by: Jkarl ]

[Guest laurendenise28]

I failed the depth perception twice (once for a general physical at MEPS and the second time for my Class 1A) and the third time taking it, I passed. They let me retake it for the 1A with a different set of glasses. The first time, not one circle stood out to me. The time I passed I made it through E... I don't understand why they said you cannot take it again? The people at MEPS said I could, and at the base where I took the 1A they said the same...I don't know alot about what you can and cannot retake, but I know a few people who have been able to redo the depth test. From what I hear from the vision therapists and optomestrists, you can improve your depth perception. You may have a dominant eye, for instance, and you can work on teaming exercises to get your eyes to work together. If you want to drop me an e-mail, I can try to help. I would try to retake if someone lets you instead of going for a waiver for it... I would imagine the final physical is the only one they sign off on. Good luck and let me know if I can help.

-Lauren

[Guest Siscojoe]

I have a situation and I was hoping someone could help me out. If I get a slot I will have to get that class 1 physical. One problem: my depth perception could use some help. I have 20/15 vision, but I am having some difficulty with the depth side of things. How extensive is the class 1 at Brooks? Are they going be critical on the test? What can I do to get my depth where it needs to be?

[Guest OldGuy]

It depends on what your depth perception problem is. If you have tropias - eyes not lining up properly - you're probably not going to be flying for the military. If you can't pass the test done at your flight physical, but can get an opthamologist to certify that you have depth perception, then you've got a shot.

If it's just a matter of you having a hard time with the test, most people do. Some recommend trying the See Clearly Method. Also if you practice looking at those Stereogram 3d images it helps.

They're going to be very critical on the depth perception portion. The saying is "there's a waiver for everything." But I've never heard of a new applicant getting a waiver for a depth perception problem (if someone has, let me know - I need one myself!). It's just not something they mess around with. I understand that some rated pilots can get waivers if their dp deteriorates, but that's it.

If you already know you have trouble with this, I'd recommend seeing an eye doc or a vision therapist to see what can be done.

Good luck.

Also, you might look in the medical forum for info on this subject.

[Guest Luke]

ok, here is the deal with the depth perception. DO NOT STARE AT THE CIRCLES!!! You have to glance at them quickly, blink your eyes, look side to side. Stuff like this will make the circle pop out. I had problems with this also. If you look to the side and blink, it will usually pop out. Also, it CANT be the circle on either side. For the circle to pop out, there must be a circle on both sides of it for the 3d effect. So the answer is never 1 or 5 only 2,3 or 4. It is a hard test, but a passable one. If you are in the military, see if you can go to the med squadron and practice on the machine. That is what I did. Without the pressure, you can practice and find out what you are looking for, and what works for you. Hope this helps

Lucky

[Guest M&M]

I'm one of the few that actually have a waiver for depth perception...so it is possible. I was late-rated, and we used to have two tests to take, and you had to pass one. I passed the second one before I started UPT. I never could, nor still can, get that damn circle test. Even when I know the answer, I can't see it. (I can't see those damn computer generated 3-D pictures either.) But, while I was at UPT (1997) I went to the eye-doc and got a full depth perception test (8 or so tests in total) because they stopped using that second test. I passed the full blown tests without a problem. I've had the waiver ever since. I'd make an appointment with an opthomologist and see how you do on one of those test to see if you have a chance. Good luck.

[Guest fosterbeer]

Ahh... I think the depth perception question comes up once every two or three months. Hopefully this will shed some light on it.

I have now taken two IFC1 physicals. At both of these, I failed the intial depth perception test, called the VTA-DP. This is the one that has the boxes with the rows of five circles in them that supposedly stick out. At my first IFC1, I was told I needed to take another series of tests for further examination. The further examination basically was the same exact eye exam that a civilian optometrist would give you, sans a color vision test. The only addition to the new exam was a depth perception test called the OVT. With this test, you put on a set of glass and look at a booklet. On one page there is a set of figures and you have to pick which circle stands out. This test is MUCH easier than the VTA-DP test. The circles clearly jump out at you. Despite having passed the second test, when I left flight medicine, I was told I still needed a depth perception waiver. This worried me a bit, until three months later when I found out my physical had been approved.

I was selected for pilot at OTS during the recent 0403 board, but my recruiter said I needed a new IFC1 because it had been over a year since my last one (the validity of that is still in question - I was told at my 2nd IFC1 that I really didn't need a new one). My recruiter gave me a copy of my first IFC1 from Patrick AFB and I noticed that nowhere on my physical did it say anything about needing a waiver for depth perception. Perhaps there was just some confusion at flight medicine and the tech did not know that the eye doc passed me on the second set of tests.

At my second IFC1, which I took just this last week at MacDill AFB, I expected to fail the VTA-DP again, but I was not worried about it. Try as might, even knowing the tips, I could still not pass the VTA-DP. I shifted my head left to right, focused behind the row of circles, etc., and nothing seemed to work - the circles would just not jump out at me. So, later in the day, before the Cyclogyl drops were put in my eyes, I was given the same OVT test I took at my first IFC1. I easily passed the OVT again.

Both eye docs at each of my IFC1s said a lot of people fail the VTA-DP test but have normal depth perception. In fact, the eye doc at my last physical said he wished the USAF would just get rid of the VTA-DP. I explained what happened at my first IFC1 at Patrick AFB, and asked if I needed a waiver to replace the VTA-DP with the OVT test and he said no.

I have no clue what happens at Brooks. I've heard of people who failed the VTA-DP and passed the OVT who didn't take any depth tests at Brooks, and I've also heard of people who passed the challenging VTA-DP who still had to take depth tests at Brooks. I haven't heard of anyone being DQ'd at Brooks for depth perception, however. I wouldn't worry about Brooks though.

My advice to anyone who fails the VTA-DP is to ask to take the OVT to replace it.

Sisco, if you are still concerned about your depth, goto a civilian optometrist and ask to take a depth perception test, or better yet, ask to take the OVT. You'll recognize the OVT as you need to put on special glasses, and the blue booklet that opens up will have a drawing of a house fly on the right page.

These have just been my personal experiences at the Flight Medicine facilities at Patrick AFB and MacDill AFB in Florida, but I hopes this helps out for anyone with depth perception questions/worries.

Feel free to email me for any questions or clarifications - fosterbeer@aol.com

word

[ 27 February 2004, 19:10: Message edited by: Dan Foster ]

[Guest fosterbeer]

Update to my above post:

Just got a call from MacDill today. It seems that since I failed the Flight Medicine DP test, but passed the Optometry Clinic's DP test, I still need to have a "complete eye workup."

So scratch was I said about using the OVT as a direct substitute for the VTA-DP. If you don't pass the VTA-DP test, no matter what, you will still have to have a full eye exam.

Now, I have no idea what a "full eye exam" is, and it seems to me that I had every eye test in the book thrown at me during my initial eye exam, so next Tuesday after 1pm, I'll let you know what it is.

keep it real

[Whitman]

I was told that for the Initial Flying Class I you had to pass all the way through F and after the initial it went to D. Tech's told me they were pretty certain of this....just trying to make sure. Also, by saying you must pass to "D", does that mean no misses you have to get all 12 right through D? Thanks

[Guest F16PilotMD]

You have to get through D to pass. "A" is for practice and explanation. You get two shots at "B". If you miss the first attempt at "B", they should go back to "A", re-explain the test and let you try again on "B". Read below from AFI-48-133.

5.7.4.3. Depth Perception Test. The "simulated" depth employed in this test can make this examination

very difficult to see. Therefore, the depth perception test is probably the most difficult to

explain and administer to the examinee. Consequently, complete failure on this test, unless supported

by other evidence, is not necessarily indicative of poor depth perception. To reduce the

number of "false failures", do not hurry through the demonstration and practice periods that precede

the actual test.

5.7.4.3.1. In explaining the test, show the examinee the demonstration device consisting of a

transparent piece of plastic with four black circles on the rear surface and one on the front.

Explain the test using similar words to these, "The slide used to test depth perception consists

of a number of horizontal rows of circles, five circles in each row, one of which should appear

slightly nearer to you than the other four. You will be asked to identify the circle in each row

which appears closer to you. Identify the closest circle by counting the circles from left to

right. In this example, the closest circle is number 3." After the demonstration model has been

AFPAM48-133 1 JUNE 2000 33

shown, tell the examinee to look into the OVT and focus on Group A, the three rows of circles

in the upper left corner of the square.

5.7.4.3.2. The first group will be used to further explain the test and allow time for depth perception

to adjust. The top row of five circles in group A demonstrates a relatively large difference

in depth, the middle row a moderate difference, and the bottom row a small difference.

Some examinees may not see any depth for the first minute or so. In such cases, do not hurry

through the practice test.

5.7.4.3.3. You may tell the examinee the correct answers to the three rows of group A and

instruct them to look at each circle in turn until they can see that one of the five circles in each

row is nearer than the others. When you are satisfied that the examinee actually sees depth in

at least the top row, proceed to the actual test. This will be given without any help or hints.

5.7.4.3.4. Ask the examinee to indicate, by number, which circle is nearer in the top, the middle

and the bottom row of group B. If all three answers are correct, the same questions will be

asked for group C, group D, etc. The test will be discontinued when the examinee gives one

incorrect answer in any one group beyond group B.

5.7.4.3.5. If any incorrect answer is given in group B, repeat the explanation with group A.

Then, if correct answers are given in group B, have the examinee try group C, followed by

group D, etc. If they still cannot correctly identify the answers for group B, discontinue the

test.

5.7.4.3.6. Record "PASSES" with the letter of the last group successfully completed D, E, or

F in the appropriate corrected or uncorrected box. If the examinee successfully completes (no

errors) groups B, C, D, E, and F then the correct entry would be: Passes (F).

5.7.4.3.7. The test is failed if the examinee makes a mistake in group B on the second attempt

or groups C or D on the first attempt. Record "FAILS" in the appropriate corrected or uncorrected

box.

[Guest pilotkppsg]

K, I took an initial flying class one physical today at Scott AFB in IL, I passed everything and was within tolerances for all the visual tests, except the damn depth perception. They tested me on the OVT machine (the one with the 5 circles) and the Random Dot tablet (the 3D glasses thing) of which I failed both miserably. I went to the base opthamologist and he gave me a few more test and he wrote down that I was able to appreciate only 140 seconds of arc. The flight surgeon said that I could apply for a waiver after I saw a civilian opthamologist and had a complete work up done with more tests and stuff. Anyway, my question is has anyone you know or have anybody on this board seen or been waived for substandard depth perception? What I don't get is why I can't pass that machine, yet I can still land planes, parallel park and do other things that would normally require depth perception. Sorry the post is so long, thanks for whatever input.

[Guest 130Nav]

If your flight surgeon says that it is waiverable then definitely look into that. My unit sent me to FTU without that waiver and it almost got me sent home.

I saw a civilian opthm and was able to pass enough of their tests that the unit decided that was good enough for them. My FTU flight surgeon did not agree tho and I had to redo my whole physical and start the whole process again.

Just be careful and make sure you have everything you need.

Good luck.

[Flare]

If this was your first time to take the test, I'd try to go in and see if you can try again. I had my yearly exam a couple of weeks ago, and when the girl set up the depth perception test, I couldn not pick out a single one! I had never had a problem on this test before, so I was kinda worried to say the least. I told the gal that I thought she set up the test wrong, because I just couldn't see anything. She was skeptical, but recycled the machine 3 more times, and still nothing! Finally, after a 4th try, she finally set up the maching right and I of course did fine. However, if this had been the first time I had taken the test, how would I have known that it was the machine that was wrong instead of just thinking that I had no depth perception! That's that's just something to think about from my experience.

[Guest pilotkppsg]

Alright, so I went to a civilian optometrist and I couldn't get better than 120 seconds of arc; I just couldn't see the circles, I tried tilting my head and all, but no dice. The doc said my brain just won't recognize it, stemming from the amblyopia. Do any of ya'll know how many seconds of arc they'll waive? I don't know, but I don't think the Air Force will waive me on that one; which is pretty gay because i've been teaching aerobatics in an Extra and been flying for more than 7 years, so i've learned to use other "visual cues" I guess to make up for my lack of depth percetion, even though I tested at 20/17 UNCORRRECTED at Scott AFB for the IFC1. You think they might look at my case an see that? I don't think so either, but I did try at least. Oh well, I just wish I could've flown for the Air Force.

[Guest JoeMama]

If I were you, and the flight surgeon said to get a civilian ophthalmology exam, I'd go ahead and get one. (Hell, I'd go to 3 different ophthalmologists before giving up...3 different tests may yield 3 different results, and one of them may let you slip through the cracks). Your waiver hasn't been denied yet! Good Luck!

Here's a copy of the Brooks Aeromedical Waiver Guide section on substandard depth perception. Bring a copy to your ophthalmologist. It'll help him/her figure out what the AF needs for your waiver:

https://www.brooks.af.mil/web/consult_servi...0Perception.htm

AFPAM-48-132

Updated-6/99

By ACS

CONDITION: SUBSTANDARD DEPTH PERCEPTION

I. Overview: The visual perception of depth or the third dimension is derived from the interpretation and integration of a number of monocular and binocular cues. As such, defects or acquired abnormalities in any portion of the visual axis may adversely affect some aspect of the perception of depth. Monocular depth perception relies on learned cues such as physical appearance of an object or the size relationship of objects. Examples of monocular cues include motion parallax and perspective. Although monocular cues to depth and distance are the primary cues utilized beyond 200m, they are subject to visual illusion. The precision of monocular depth perception is highly variable, depending on stimulus, lighting and motion of the object, but is generally accepted to be inferior to binocular depth perception (stereopsis).

True binocular stereoscopic vision (stereopsis) represents the finest level of depth determination and refers to the interpretation of depth by detection and interpretation of retinal disparity. The ability to discern depth accurately seems to develop at about 3 months of age in normal infants. However, this ability is dependent on accurate depiction of an image upon the retina of both eyes simultaneously, and upon the correct interpretation of that stimulus. Any disruption of accurate retinal imaging will adversely affect depth perception. A subset of individuals are unable to accurately perceive depth secondary to developmental abnormalities of the neuro-retinal pathway. The most common example of such a defect is childhood amblyopia (also called “lazy” eye), which includes strabismic amblyopia (a misalignment of the optic axis), anisometropic amblyopia (due to retinal image size or clarity differences from differential refraction between the two eyes) and deprivation amblyopia (from opacities or blockage of the optical media such as cataract, ptosis or uniocular retinal disorder). A subset of these individuals may have transient misalignments of the visual axis sufficient to cause strabismic suppression of one of the misaligned images across such a small portion of the visual axis as to be undetectable by the individual, and detectable only with specific testing. Similarly, however, acquired disorders, such as imperfect refraction or uniocular visual disruption from ocular conditions, such as a cataract, can adversely affect the depth perception in a previously normal individual. Sources of depth perception defects commonly seen among aviators and aviator applicants include defective ocular muscle balance, uncorrected refractive errors, microtropia, anisometropia and monofixation syndrome.

Although some defects in stereoscopic vision may be corrected with correction of the visual abnormality, individuals with corrected childhood amblyopia exhibit a high prevalence of reduced contrast perception, and even the vast majority of children who undergo correction at an early age do not ever achieve normal stereopsis.

The USAF utilizes the VTA-DP, or its newer replacement, the Optec 2300 (OVT-DP), for assessment of depth perception in aviators. Passing this test requires the ability to discern depth based on a disparity of at least 25 seconds of arc (line D), although the test is capable of testing as low as 15 seconds of arc. “Normal” stereo vision is considered to be 30-40 seconds of arc, although a few people have stereoacuity that is better than 15 seconds of arc. The limit of human stereopsis is probably around 5 seconds of arc. Verhoeff and Howard-Dolman tests are no longer used in routine screening, but they are utilized by the ACS in determining potential waiverability of substandard stereopsis cases.

II. Aeromedical Considerations. Stereopsis is generally not considered to be a factor in the perception of depth beyond 200m. Beyond those ranges, monocular cues prevail to facilitate perception of depth. In aviation, accurate perception of spacing or depth within this distance is critical in a number of situations, such as aerial refueling, formation flying, holding hover rescue type operations, taxiing, and parking. Stereopsis also facilitates closure maneuvers and rejoins. The majority of aviator tasks, dependent on the perception of depth, occur beyond 20 feet. As close proximity flying situations rarely arise in civil aviation, the FAA does not require depth perception testing for general or commercial aviation. However, military formation flying requires constant monitoring and requires normal stereoscopic/depth perception.

III. Information Required for Waiver Submission. The most common cause of an acquired depth perception defect is uncorrected refractive error. Depth perception testing should not be attempted until optimal correction has been achieved.

A. Evaluation Required for Waiver Consideration:

1. Local evaluation by an optometrist or ophthalmologist is required prior to consideration of further waiver processing to rule out correctable causes and those conditions that would preclude further consideration. The local work-up format includes at a minimum:

a) Complete direct and indirect ophthalmoscopy

B) Optimal refraction with further testing, including repeat VTA-DP or OVT-DP, to be accomplished with optical correction of any refractive errors, regardless of unaided visual acuity

c) AO vectograph

d) Red Lens test

e) Four-diopter base-out prism test

Results from these tests will be used by higher waiver authorities to determine if further processing is appropriate.

2. Aeromedical Consultation Service (ACS) evaluation is required for waiver recommendation after correction of any reversible or correctable deficits. Initial applicants may be evaluated if their defect is suggestive of microtropia or monofixation syndrome per published research protocols.

IV. Waiver Considerations. One hundred fifty two aviators with defective depth perception are recorded in the USAF WAVR database. Most were identified retrospectively. Among Class I and II aviators, all but four received waivers for substandard depth perception (most due to monofixation or microtropias), and the four who were disqualified were not primarily disqualified due to depth perception. Of 19 Class III aviators listed in the database, seven were disqualified, all primarily due to defective depth perception. Many of these were boom operators in whom accurate depth perception is also considered critical. Many of the waivered aviators, who received waivers, enjoyed highly successful military aviation careers despite subtle defects in depth perception not detected until late in their careers. However, it is not known how many student aviators may have washed out as a direct consequence of undetected depth perception problems. It is presumed that a subset of mildly defective microtopes may perform adequately in the cockpit. Therefore, a subset of initial applicants who have subtle defects in stereopsis due to microtropia or monofixation syndrome have been issued waivers as part of a prospective EFS-M research protocol. Prerequisites for inclusion in these studies have been outlined elsewhere, and requests must be coordinated through the appropriate MAJCOM.

A large body of data exists regarding the effects of night vision goggles and depth perception. Even dual tube goggles may not provide accurate depth assessment capabilities for a number of reasons including off axis adjustments, poor focussing, and poor tube performance. Depth perception in the aviation environment may be compromised after the use of cycloplegic agents.

Waiver, therefore, is possible for aviators with mildly defective depth perception in the absence of other retinal or uncorrectable ocular pathology. Individuals in aviation specialties which rely on stereoscopic depth perception for performance of assigned duties (boom operators) and aircrew with more significant deficits are less likely to receive favorable consideration. Each aircrew member is considered on a case by case basis.

V. References.

1997 Aeromedical Reference and Waiver Guide, US Navy.

Aerospace Ophthalmology VII. AMP HO 342. Ophthalmology Branch, Clinical Sciences Division, USAFSAM Brooks AFB TX.

Effects of the Chemical Defense Antidote Atropine Sulfate on Helicopter Pilot Performance: An In-Flight Study. Army Aeromedical Research Lab, Ft. Rucker AL. 1991.

Howard IP and Rogers BJ. Binocular Vision and Stereopsis. Oxford University Press, New York NY. 1995.

Patterson R and Pullman WL. Human Stereopsis. Human Factors 1992;34 (6):669-92.

[Guest Greg Dierenfield]

Just a little heads up for those inbound for Brooks. The red lense test is the one that will red flag you for depth perception. Don't let them rush you, they will try. I had a bad experience there this last week, and now am flighting to see if I can fly. I would recommend going to a civilian doctor and having all the tests done that they will be dong at Brooks.

[JS]

Originally posted by Tom Ace:

Just a little heads up for those inbound for Brooks. The red lense test is the one that will red flag you for depth perception. Don't let them rush you, they will try. I had a bad experience there this last week, and now am flighting to see if I can fly. I would recommend going to a civilian doctor and having all the tests done that they will be dong at Brooks.

Also beware of the color vision tests at Brooks. They give you like 5 tests, and 4 of them you will have never seen before and can catch you by surprise. I know of a few people who passed CV on the FC1 and are now flying a desk somewhere due to failing the battery of different CV tests at Brooks. Email me if anyone has any questions or if you might be weak at CV.

jseeber66@yahoo.com

[Champ Kind]

Anyone know if one would be allowed to go to the clinic on base and practice the depth perception test by looking into the scope they have there?

I've heard that just doing it (sts) is a huge way to improve your test results. I'm heading to Brooks in about two weeks, and I'm a little nervous (even though I've pretty much settled with the notion that if its "meant to be", it will work out.)

I'm concerned because, during my FC1 about this time last year, I failed the depth perception test the first time around, because I just honestly couldn't see which ring was standing out when I looked into the scope. But, when they did that 7 or 8 -part test on me, I passed no problem.

In short, I just want to get good at passing using the "normal" method so that I don't have any flags raised up when they test me, and make it easier on everyone.

Thanks a lot!

[Guest Dirt Beater]

This might sound dumb, but you might want to try looking up "3D images" or something like that on google...you know, the funky images where the image all of a sudden "pops out." Correct me if I'm wrong, but I think the little machine they use (the one with the 5 circles) basically tests your stereo vision. These 3D pics are stereo images, so if you can practice getting the image to pop out at you, you're probably doing yourself some good. My two cents.

[Gravedigger]

I used the "Magic Eye Method" and it worked for me on the Navy version of the test. Now, I have to go try it for the AF again. Good Luck!

[Guest JL]

Something to remember with this test. You only have to pass up to D..... this means you DO NOT have to pass all of it. I was pulled off flight status for this reason, luckily theres a flight doc on this site that knows his stuff....

Also, ive been told that only the center three circles are correct answers. (Meaning if you think 1 or 5 is the answer your better off guessing between 2,3,4) - cant verify that though... i plan to when they let me leave the desert.