This video covers the basic optics you need to know to understand basic glasses prescriptions.
length: 24:00 minutes
When I began my ophthalmology residency, I had no idea how to read or write a glasses prescription. In this video, I try to explain the basic topics I wish I had known. This includes lens theory, basic spherical problems (near and far-sightedness), astigmatism, cylinder conversion, and presbyopia (bifocals). While this lecture is “basic” and assumes you have no prior glasses experience … this is still important stuff. I hope you find this useful!
Screen Captures from this Video:
The goal of this video is to completely understand what a glasses prescription
entails.
A lens can be thought of as two prisms … that either converge or diverge light.
A lens rack. The red lenses are "minus" while the black lenses are
"plus"
Lenses are marked with diopter power.
Definition of a diopter is demonstrated, along with lens stacking to create
more powerful convergence.
The eye has an overall power of approximately 60 diopters.
Children tend to be slightly hyperopic as they have small eyes.
Astigmatism is when the corneal surface is more "round like a football"
and less like a basketball.
Children have "with the rule" astigmatism, while elderly tend to have
"against the rule"
The three measurements we check when using the phoropter to "manifest"
a patient
Converting a prescription to minus cylinder
Accomodation of the lens inside the eye
Presbyopia makes it hard to see near objects.
Bifocal power. We rarely prescribe greater than 3 diopters as few people read
much closer than 1/3rd of a meter (33 centimeters).
I’m in my last year of med school and still learned a lot from your video. It’s amazing how you can make these topics so simple to understand. I really wish I had more professors like you! Thank you for your time!
thank you very much. i love this site and have learnt alot from here. i want to be ophthalmology surgeon. i’m so happy.
thank you again.
Comment by mohamed Haibeh — April 7, 2011 @ 1:56 pm
Dear Dr.
I truly appreciate your time and diligence making such an informative video for students such as ourselves. It was clear concise and an addendum to our school lectures. I would be interested in discussing with you about making future educational videos for students. Please contact me at your earliest convenience.
thank you Dr.Thimothy, this video & other staff in brilliant website are treasure for ophthlmic residents.. I wish i found this site when i was in my 1st yr.. anyway im not too late, im 2nd yr now;)
Comment by Dr.Omar Khudruj — November 10, 2011 @ 10:10 am
thank you sir its really amazing its my first time to understand correction in this fascinating way
Comment by night walker — December 14, 2011 @ 4:07 pm
