This video lecture covers ocular motility, specifically the difference between tropias and phorias. This is a simplified approach to detecting strabismus and documenting your findings. I’ve created an animatronic set of eyes out of cardboard to simulate these findings!
Misalignment that is always there, even when both eyes are open and attempting
to work together. Large angle deviations are obvious. If small angle, you can
detect it with the Cover-Uncover test.
Misalignment that only occurs some of the time, such as when the synchronization
between the eyes is broken by covering one eye. You can “break fusion” using
the Cross-Cover test.
Exotropia is when an eye turns outwards.
Esotropia is when an eye turns inwards.
Hypertropia is when an eye turns upwards.
Hypotropia is when the eyeball turns downwards.
Explaining the skull structure between horses and humans, and how this affects
the cardinal directions.
It helps to understand the ocular anatomy if you’re going to understand cardinal
directions of eye movement.
There are several ways to document large eye deviations. This is my preferred
method for large angle ductions.
This is another method to document eye tropias. On this scale, "0"
is normal, while "-4" is no movement.
The cover-uncover test is used to pick up small-angle tropias.
The cross-cover test (also known as the alternate cover test) is used to tease
out phorias. This works because you break fusion between the eyes.
Wow! Great explanation and animations!
Comment by Tom — November 8, 2010
Comment by granny — December 18, 2010
Great explanation and we enjoyed your lecture! Thank You
Comment by Dr. P class at ACC Anaheim — February 11, 2011
it is more than great video.you simplified many obstacles.thank you very much.
Comment by siso — March 13, 2011
well i am just 14 years old and i dont get the explnation so lets hope next time
Comment by zach — April 17, 2011
Thank you very much for your nice videos
Comment by dr,zainab — August 7, 2011
thank you for you intrsting lecture but we need more lecture to cover all point about squint
simplified the basics of squint.can u add some more lectures about squint.
Comment by sonykjose — August 17, 2011
thank you very much for your excellent video
Comment by benny — October 15, 2011
Wow great video! Thanks
Comment by Derek — January 24, 2012
I would like to point out that a you defined a tropia as a misalignment that is always there. A trope can be also be intermittent, and therefore not always there.
Comment by Aaron — February 16, 2012
Thanks for the feedback. I purposefully kept the definition of tropia as simple as possible. You are correct, in that you can also have an “intermittent tropia.” You can also have an alternating tropia, convergence-related tropia, and many other “types” of tropia/phoria depending upon how you like to name things.
When I put this presentation together, I felt it safer to avoid these nuances. I feared that discussing the intermittent nature of phorias/tropias would muddy the waters for the beginner and make the primary difference (between phoria and tropia) that much harder to grasp.
Thus, the definition I used is simplified … but still useful and valid for a beginner. Perhaps I’ll go into further detail in a future lecture. Thanks!
Comment by Tim Root — February 16, 2012
Great lecture, very easy to follow. however i am a little confused as to what you meant by a ‘right esophoria’ (mentioned towards the end of the lecture). Ive always understood phorias being a bilateral misalignment of the visual axis, however you could have an esophoria which breaks down to alternating esotrpia…then breaking down further to maybe a right esotropia as the eyes fatigued with time.
Comment by NB — August 20, 2012
thank u so mch sir ..ur lectures r so marvellous
.They should be a part of the curriculum..
Comment by Tulika Gupta — September 14, 2012
what are the yoke muscles involved in dextroelevation?? please give some explanation as well
Comment by kushal — July 30, 2013
its a very nice video& lecture that i appreciate………
Comment by tibebu kassie — November 19, 2013
Comment by samra — June 10, 2014
fantastic videos lot of conceps cleared thnks
Comment by dr. pawan — September 30, 2014
I’m a optometies in china,I love your thinking,it help me know something more easy.I try to translate your lectur. I think it will be very helpful.I hope that you can give me some advice。
Comment by Hevia — November 14, 2014
Thank you root for the lecture and video simplified
Comment by nsowah,Optometrist Ghana — January 15, 2015
hi may I ask how does our eyes synchronize and how does a cross-cover test break the fusion?
Comment by Rachel — March 13, 2016
Thanks for giving us such an difficult topic in a simple and easy way, otherwise it was not clarified to me since last two years in ophthalmic classes
Comment by Sakina Masud — April 9, 2016
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