What is the function of this chart ? What eye defect you may suffer if you see the distant object...
Transcript of What is the function of this chart ? What eye defect you may suffer if you see the distant object...
What is What is the the
function function of this of this chart ?chart ?
What eye What eye defect you defect you may suffer may suffer if you see if you see the distant the distant object like object like
this? this?
Eye DefectsEye Defects& Their Corrections& Their Corrections
Short Sight
Long Sight
Colour Blindness
Short SightShort Sight
Light rays fromDISTANTDISTANT object
Definition: The image of DISTANTDISTANT object falls IN FRONT OFIN FRONT OF the retina.
Causes of Short Sight:
Corrections:
1. The lens is too CONVEXCONVEX.2. The eye ball is too LONGLONG.
Wearing CONCAVECONCAVE (diverging) lens→ divergediverge the light rays from the distant object onto the retina.
Corrections of Short SightCorrections of Short Sight
Light rays fromDISTANTDISTANT object
Concave lensConcave lens Light rays areLight rays aredivergeddiverged
Sharp imageSharp image
Long SightLong Sight
Light rays fromNEARNEAR object
Definition: The image of NEARNEAR object falls BEHINDBEHIND the retina.
Causes of Long Sight:
Corrections:
1. The lens is too THINTHIN.2. The eye ball is too SHORTSHORT.
Wearing CONVEXCONVEX (converging) lens→ convergeconverge the light rays from the near object onto the retina.
Corrections of Long SightCorrections of Long Sight
Light rays fromNEARNEAR object
Convex lensConvex lensLight rays areLight rays areconvergedconverged
Sharp imageSharp image
Colour-blindnessColour-blindnessWrite down what you see in each of the following chart!!
a.
b.
c.
d.
ChartChart
VisionVision a. b. c. d.NormalNormal
29 45 26Red-green colouRed-green colour-blindnessr-blindness
70 5 2 or 6Total colour-blindTotal colour-blindnessness
Are you suffering from colour-blindness?
Causes of Colour blindness:
Types of Colour blindness:
1. It is due to the absence of certain kind of cone cells.
2. It is a hereditaryhereditary defect. So, it cannot be corrected by wearing glasses.
1. RedRed-greengreen colour blindness.2. Total colour blindness.