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Tropias and Phorias (Video)

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!

length: 17:23 minutes

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TropiaVsPhoria.m4v (139 MB)


Screen Captures and Notes

Tropia Definition:
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.

Phoria Definition:
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.

horse eye
Explaining the skull structure between horses and humans, and how this affects
the cardinal directions.

Eye anatomy
It helps to understand the ocular anatomy if you’re going to understand cardinal
directions of eye movement.

cardinal directions
There are several ways to document large eye deviations. This is my preferred
method for large angle ductions.

cardinal eye muscles
This is another method to document eye tropias. On this scale, "0"
is normal, while "-4" is no movement.

Cover Uncover Testing
The cover-uncover test is used to pick up small-angle tropias.

Cross-Cover Test
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.



Thank you Dr.Root
Your presentation is very helpful and simple as you usually do..
keep good work up and thanks again.

Comment by zen — November 10, 2010

Thanks, Dr. Root.

Comment by I Am Name — November 14, 2010

Thank you Dr Root for your good and scholar presentation

Comment by mortezashamsizadeh — December 14, 2010

good job

Comment by feras mohdor — December 18, 2010

Dr.root a salute to u.wat an amazing job you have done.sir please continue to do this noble work by giving out these great informative and intereting lectures.thank you.hope to meet you some time in the future.thank you again

Comment by DR.root fan — January 5, 2011


Comment by sulay — June 21, 2011

This was a great works and did a a tremendous help in teaching our student to understand this topic.

Comment by Wahyu Raharja — June 29, 2011

Hi Dr.Root
In the frist I want say thank you for your lectures
I have a question when we do the glasses to the patient we but prism in front of the natural eye or in front of the eye in which have tropia
Thank you

Comment by Anas — July 30, 2011

superb!!!! Simply the best

Comment by anshuman — August 13, 2011

Thank you so much.This’s very usefull for my study.

Comment by magnagiled — August 16, 2011

u r great sir. all dr teachers should like u. thank u very much

Comment by lovely — August 24, 2011

Thanks so much! Great video for distinguishing between phoris and tropias.

Comment by Jen — September 15, 2011

I learnt retinoscopy prety well with the help of your video and now the difference between Tropias and Phorias. Your explanations are simply simple. Thank you so much.
Sir, I wish to see a animated/live demo of usage of JCC (Jackson’s cross cylinder).
Thanking you once again.

Comment by Anant — October 11, 2011

Thanks a lot .

Comment by yasmine — March 23, 2012

Thank you!! I am a medical student and i now can totally understand tropis and phoria. hope i can make a Mandarin version in the future. Love your work~~!!

Comment by nichin — April 1, 2012

You spoke about double vision that comes from they eyes not being in alignment with each other… I have episodes of that too, but the thing that sets me apart is I have double vision in my left eye and sometimes triple vision in my right. I’m talking about when one or the other eye is completely closed and still each eye has multiple images, a primary and then some secondary one or ones… Can that really be from cataract like I was told by my eye doctor? I have been diagnosed with Ehlers Danlos type 3 and am afraid to get surgery til I feel confidant my eye doctor knows what’s going on. My eyesight gets worse then better then worse and it’s worrysome to say the least. Annoying as all get out too. I wish I could find more info on caratact surgery for Ehlers Danlos patients and am afraid of getting macular degeneration after the surgery so I’m just scared!

Comment by Mona — June 25, 2012

i will like to know the difference betweent phorias and tropias.thank u.

Comment by ndzi elvice — July 12, 2012

superb sir. amazingly simple presentation.

Comment by vinod — August 27, 2012

Thanks alot Dr Root.
You really equiped me with ellaborate informations.
Keep it up.

Comment by langat christopher — September 21, 2012

great presentations,you have fans in morocco

Comment by alesi — October 2, 2012

you are the best sir…always checking this site…please keep adding more…we tuely love your efforts

Comment by Rahul Navani — October 7, 2012

thank you so much DR ROOT &thanks GOD you are there for me am so greatful for your effort to make ophthalmology easier for us.

Comment by SAJA — October 8, 2012

Amazing! Thank you sooooooooooooooooooooooooooo much!

Comment by Sadaf Shah — December 18, 2012

hi im 21 years old male from morocco i have an “hypotropia“ probleme , anyway i ask if there is a treatment , and im ready for being a research project , thank you.

Comment by yassin — January 5, 2013

Por favor… que sea en español!

Comment by Soledad — January 30, 2013

Excellent simple tutorial

Comment by MDM — May 5, 2013


Comment by PRASAD — June 5, 2013

Thanks alot Dr Root . Iam medical student from egypt and I love your videos alot

Comment by Amany — June 27, 2013

keep it up dr root

Comment by chidinma ogu — July 8, 2013

A special thank you Doc & two thumbs up … YOU ARE GREAT.

Comment by Michael Ragaee — October 1, 2013

thank you for the care and Great work Doc we appreaciate your concern keep Posting them

Comment by Sandeep Rohatgi and Dr V.S. Rohatgi — April 6, 2014

I have just returned to COA after 15 years away. Your videos have been a lifesaver!!! Thanks so much for posting these, I’ve watched every single one!

Comment by Melissa Tucker — June 25, 2014

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