Distressed! Difficulty with Stereopsis on the Slit Lamp?

[tobacc0dust]

I'm currently an intern and am starting my ophtho residency next July. I'm doing an ophtho elective and I noticed when using the slit lamp and the indirect that I have difficulty with fusion of the image.

On the slit lamp, I adjust the PD so that if I close my right eye I see the image and I close the left eye I see the same image. However, when I open both eyes, I see double and it's very difficult for me to fuse the image if I can at all. So I often just narrow the PD more and I end up seeing one image but it's mostly just out of the right eyepiece because when I open my left eye I don't really see anything. Obviously, I can't see stereo through this.

Also, with the indirect, I adjust the PD so that I see my thumb in the middle while closing one eye, but when I open my eye, I see 2 light circles (am I supposed to see that?), so I just narrow the PD again so that I only see one light circle but my thumb is not centered but rather more in my nasal visual field with both eyes.

I passed the random dot stereopsis test and when I look through the stereoviewer? I can see things like the optic nerve in stereo, but for some reason I can't seem to adjust the PD on the slit lamp correctly so that I can see out of both eyes while fusing the image into one.

I didn't get much experience as a med student using the slit lamp or indirect and I thought I would just "figure it out" later and I knew I had stereopsis with the formal stereo tests I did for my ophtho interviews, but now I am starting to get worried! Is there something I am doing wrong? I wonder if I need to see a peds ophthalmologist or get prisms? I'm really worried because I know how difficult it is for surgery and for a lot of the diagnosis without stereo! Any help would be GREATLY appreciated! 🙁

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[DKofLV]

I'm currently an intern and am starting my ophtho residency next July. I'm doing an ophtho elective and I noticed when using the slit lamp and the indirect that I have difficulty with fusion of the image.

On the slit lamp, I adjust the PD so that if I close my right eye I see the image and I close the left eye I see the same image. However, when I open both eyes, I see double and it's very difficult for me to fuse the image if I can at all. So I often just narrow the PD more and I end up seeing one image but it's mostly just out of the right eyepiece because when I open my left eye I don't really see anything. Obviously, I can't see stereo through this.

Also, with the indirect, I adjust the PD so that I see my thumb in the middle while closing one eye, but when I open my eye, I see 2 light circles (am I supposed to see that?), so I just narrow the PD again so that I only see one light circle but my thumb is not centered but rather more in my nasal visual field with both eyes.

I passed the random dot stereopsis test and when I look through the stereoviewer? I can see things like the optic nerve in stereo, but for some reason I can't seem to adjust the PD on the slit lamp correctly so that I can see out of both eyes while fusing the image into one.

I didn't get much experience as a med student using the slit lamp or indirect and I thought I would just "figure it out" later and I knew I had stereopsis with the formal stereo tests I did for my ophtho interviews, but now I am starting to get worried! Is there something I am doing wrong? I wonder if I need to see a peds ophthalmologist or get prisms? I'm really worried because I know how difficult it is for surgery and for a lot of the diagnosis without stereo! Any help would be GREATLY appreciated! 🙁

First things first, is everything aligned correctly on the slit lamp? If the beam is off to one side this may cause one eye to be blocked.

it almost may simply be an issue of focusing correctly on their retina...practice makes perfect

most people do just fine once the etiology of their difficulty is teased out

 

[CastroViejo]

I noticed I was having a similar problem during my med school rotation, but then when looking through the scope, I kinda try to go cross-eyed a little (as if you were trying to look at one of those Magic Eye 3d puzzles...do you remember those), and then a stereoscopic view would suddenly appear. This problem really freaked me out at first, and not sure why I had this difficulty because I also have good stereo vision as defined by the ophtho tests. However now Ive gotten used to it and can adjust my eyes pretty easily, and it even seems to work if the oculars are not adjusted to my pupillary distance. Perhaps this will not work as a permanent solution and I guess I might need a prism later so I don't have to actively compensate, but give this a try and see if it works for you too. I literally had the exact same distress a few months ago.

 

[KHE]

I noticed I was having a similar problem during my med school rotation, but then when looking through the scope, I kinda try to go cross-eyed a little (as if you were trying to look at one of those Magic Eye 3d puzzles...do you remember those), and then a stereoscopic view would suddenly appear. This problem really freaked me out at first, and not sure why I had this difficulty because I also have good stereo vision as defined by the ophtho tests. However now Ive gotten used to it and can adjust my eyes pretty easily, and it even seems to work if the oculars are not adjusted to my pupillary distance. Perhaps this will not work as a permanent solution and I guess I might need a prism later so I don't have to actively compensate, but give this a try and see if it works for you too. I literally had the exact same distress a few months ago.

A prism is unlikely to help in these situations. The real solution is to see an optometrist or ophthalmologist who does vision therapy and get some fusional vergence exercises and/or accommodative exercises.

I had this exact problem myself before I entered optometry school. I could never use any binocular microscopes, binoculars, could never do any of the magic eye pictures etc. etc. Turns out I had convergence excess. A few weeks of VT and everything was fine.

 

[thackl]

For a few weeks, i didn't even realize I wasn't seeing stereo, then I struggled for a little while with what you're describing and now all is fine. Just stick with it. Your concern is not uncommon and for most it resolves with practice/strengthening. One of my attendings talked about convergence insuff. when he started that resolved with some type of exercises/practice.

 

[bucknut101]

I too had this problem in the beginning as well. Like with the other posters it eventually resolved as well. Just keep sticking with it.

 

[Meibomian SxN]

I'm currently an intern and am starting my ophtho residency next July. I'm doing an ophtho elective and I noticed when using the slit lamp and the indirect that I have difficulty with fusion of the image.

Any help would be GREATLY appreciated! 🙁

Sounds like you have a vision problem as opposed to sight. You should make an appointment to see an Optometrist who does vision therapy...

 

[jefguth]

very very common to have this type of trouble - just be glad you're not suppressing an eye because that would be significantly harder to deal with.

Not a bad idea as mentioned to have some sort of binocular vision exam.

 

[PBEA]

I'm currently an intern and am starting my ophtho residency next July. I'm doing an ophtho elective and I noticed when using the slit lamp and the indirect that I have difficulty with fusion of the image.

On the slit lamp, I adjust the PD so that if I close my right eye I see the image and I close the left eye I see the same image. However, when I open both eyes, I see double and it's very difficult for me to fuse the image if I can at all. So I often just narrow the PD more and I end up seeing one image but it's mostly just out of the right eyepiece because when I open my left eye I don't really see anything. Obviously, I can't see stereo through this.

Also, with the indirect, I adjust the PD so that I see my thumb in the middle while closing one eye, but when I open my eye, I see 2 light circles (am I supposed to see that?), so I just narrow the PD again so that I only see one light circle but my thumb is not centered but rather more in my nasal visual field with both eyes.

I passed the random dot stereopsis test and when I look through the stereoviewer? I can see things like the optic nerve in stereo, but for some reason I can't seem to adjust the PD on the slit lamp correctly so that I can see out of both eyes while fusing the image into one.

I didn't get much experience as a med student using the slit lamp or indirect and I thought I would just "figure it out" later and I knew I had stereopsis with the formal stereo tests I did for my ophtho interviews, but now I am starting to get worried! Is there something I am doing wrong? I wonder if I need to see a peds ophthalmologist or get prisms? I'm really worried because I know how difficult it is for surgery and for a lot of the diagnosis without stereo! Any help would be GREATLY appreciated! 🙁

in addition to the PD you must also dial in the diopter of the oculars. If the power is considerably different then wht you require, it can induce diplopia. BIO sometimes have optional lens inserts that you can remove.

 

[orbitsurgMD]

in addition to the PD you must also dial in the diopter of the oculars. If the power is considerably different then wht you require, it can induce diplopia. BIO sometimes have optional lens inserts that you can remove.

Are you wearing glasses at the slit lamp or not? If yes, check whether you need to reset the eyepiece eyecups. Roll them up if they are adjustable. You want the proper eye relief at the eyepiece. An check that the diopter adjustment is not turned out of the setting you want for your correction.

You haven't said what kind of microscope that you are using. Some are a little easier to get used to if you are new. Greenough-design is easier than Galilean. The older-design Haag-Streit 900 and BM900-units and their copies (Topcon, Mentor, Marco, Burton, etc.) have convergent microscope design that has convergent tubes throughout. The Galilean designs (Zeiss and copies) may have a convergent or parallel binocular, but the selectable objectives are parallel, and some people complain of more difficulty with fusing with them. Also, as another said, make sure the lamp mirror/prism is out of the way of the microscope. if you are using side illumination.

Most slit lamps are robust and don't mis-align with abuse even. Some though are kind of crappy and can have loose parts even when new and with little use.

 

[tobacc0dust]

So I got it checked out and it seems like I have convergence excess only when using these binocular systems and only on certain slit lamps. For example, on the Marco and Topcon I see single but on the Haag-Streit I see double and it's difficult for me to fuse. Once in a blue moon if I'm just staring aimlessly at something for about 1 minute it will magically come together, but usually it won't. It's strange because I have no difficulty reading at many different focal lengths. Also, with the BIO I actually don't see double..I think I was just doing something wrong with the PD.

Anyways, when I put a base out prism in front of a slit lamp, the two images converge into one easily. What I was told was that for convergence excess there's not many exercise I can do and I just need to use prisms? However, I need to use a pretty high diopter prism (sometimes 10D sometimes 6D) to fuse the image on some slit lamps. Sometimes I require less but it just depends and it seems like after I fuse with the 10D prism and I switch to lower power prisms I can still maintain the image as fused almost down to 2-diopters meaning that I just need some kind of stimulus to bring it together.

Would you recommend getting just plano prism glasses with 5D in each eye for the slit lamp with contacts underneath? I'm worried that using such a high diopter prism may change my vision in some way because I feel kind of dizzy right now. 🙁 Also I feel like it will be different with every slit lamp, so I may not need as much for some or may not need any prism for others...

 

[KHE]

So I got it checked out and it seems like I have convergence excess only when using these binocular systems and only on certain slit lamps. For example, on the Marco and Topcon I see single but on the Haag-Streit I see double and it's difficult for me to fuse. Once in a blue moon if I'm just staring aimlessly at something for about 1 minute it will magically come together, but usually it won't. It's strange because I have no difficulty reading at many different focal lengths and my NPA is normal. Also, with the BIO I actually don't see double..I think I was just doing something wrong with the PD.

Anyways, when I put a base out prism in front of a slit lamp, the two images converge into one easily. What I was told was that for convergence excess there's not many exercise I can do and I just need to use prisms? However, I need to use a pretty high diopter prism (sometimes 10D sometimes 6D) to fuse the image on some slit lamps. Sometimes I require less but it just depends and it seems like after I fuse with the 10D prism and I switch to lower power prisms I can still maintain the image as fused almost down to 2-diopters meaning that I just need some kind of stimulus to bring it together.

Would you recommend getting just plano prism glasses with 5D in each eye for the slit lamp with contacts underneath? I'm worried that using such a high diopter prism may change my vision in some way because I feel kind of dizzy right now. 🙁 Also I feel like it will be different with every slit lamp, so I may not need as much for some or may not need any prism for others...

Trust me...I had the exact same issues. A few weeks with a Brock string and some stereo vectograms and some mild accommodative training will take care of this. Don't bother with prism. You're just going to adapt to it and you'll need it for every binocular instrument you use. Why mask the symptoms? Cure the problem.

 

[Colliculus1]

I also have a hard time fusing, but only with the Zeiss, no problems with the Haag Streit. I have found that if I focus on the wall behind the patient, then quickly look through the slit lamp, i can get it fused. The more you train to fuse, the easier it will be for your eyes to "get it"
It'll happen, take it from a 1st year resident