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OPTICAL INSTRUMENTS

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by

Grace Adam

on 15 October 2015

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Transcript of OPTICAL INSTRUMENTS

Accommodation of The Eyes
EMMETROPIA
(Normal-Sightedness)
MYOPIA (shortsightedness)
EXERCISE
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Hypermetropia (farsightedness)
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The ability of the eye lens to thicken is not good anymore
because the eye muscles get weak so they cannot thicken the eye lens perfectly.
TYPES OF THE
What's An Eye?
Presbyopia (Old Eyes)
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OPTICAL INSTRUMENTS :
The punctum proximum (near point) of a hypermetropic eyes more than the normal reading distance ( PP > 25 cm )

The eye defect can be helped by using
convex lens
glasses.
AGNES.DIAN.GLENDA.GRACE
Usually a person who is more than 40 years old may suffer from
presbyopia.

Cause : The poor adjustment to the thickness of the eye lens.

Resolution : Double lens glasses ( Concave in upper part and convex in lower part).

Eye is an organ in the head through which people and animal see.
Parts of The Eye
a.
Cornea
= to receive rays from the light source.
b.
Pupil
= controls light intensity which enters the eye
c.
Iris
= adjust the width of the pupil & give the color to the eyes
d.
Lens
=
- Receives rays that enter from the pupil & pass them to the retina
- Focus the light so that it falls exactly on the yellow spot of retina
e.
Retina
= capture the rays from the eye lens & transmitted it to the brain through the eye nerves.
The features of the image formed by the eye at the retina are always
real
,
inverted
, and
diminished
.
Accommodation
is the ability of the eye lens to get thicken or flatten to ensure that the image on the retina is clear.
This mean that the eyes has perfect accommodation.

It has around 25 cm punctum proximum (near point) and very distant or infinite punctum remotum (distant point).
The ability of the eyes lens to flatten is not good anymore.

Cause : The eye lens is often used to see a nearby object for a long period of time.

This activity forces the eye lens to thicken as powerful as possible.


Has less than infinity punctum remotum (distant point) (PR< ~). This eye defect can be helped using concave lens glasses.
Bob cannot see an object farther than 40 cm clearly. Determine the type & power of the lens he should wear to see normally.
ANSWER IT!!! HUAHAHHAHAHA BOB ATTACK!
How to Count The Power of Lens
The result in
concave
lens will be
negative

(-)
, while in
convex
lens will be
positive (+)
EXERCISE!!
Grandfather cannot read a newspaper clearly at the distance of no more than 50 cm.

If he wants read the newspaper at the normal distance (25 cm), determine the type and power of the lens he should use.

GRAMPY CHAN ATTACCCK!! SOLVE IT!!!
CYLINDER (Astigmatism)
Astigmatism eye abnormality, eye ellipse or oval, like a rugby ball, so that light entering the eye will not meet in one point of the retina.

Resolution : Cylinder lens
THANK YOU!!
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