Name the parts.

Refractive errors



Try it first, check back on the lesson answers second!


17. If the focus is behind the retina the eye has too power, so we put power in the glasses lens to bring the image into focus on the retina.

    When the focus is behind the retina we say the eye is . A characteristic of lenses is that they are used to correct for .

18. If the focus is in front of the retina the eye has too power, so we put power in the glasses lens to bring the image into focus on the retina.

    When the focus is in front of the retina we say the eye is . A characteristic of lenses is that they are used to correct for .

19. If the refracting surfaces (cornea and lens) have the power that is considered normal, but the eye globe is too long or to short, we say that the condition is .

    If the eye globe is 24mm, but the refracting surfaces (cornea or lens) have too much or to little power, we say that the condition is .

Not fair, was that?

20. The two possible causes of myopia are:
    
21. The two possible causes of hyperopia are:
    
22. The usual cause of astigmatism is :
    

Tell me what kind of refractive error the following Rx's will correct for. (First figure out what the major meridian powers are, then name the refractive error.)

23. +2.75 -1.75 x123


24. +2.75


25. -2.75 -1.75 x123


26. +2.75 -2.75 x123


27. -1.75


28. +1.75 -2.75 x123


29. -2.75 +1.75 x123


30. -2.75 +2.75 x123


31. pl -1.75 x123