refractive error.ppt definition. Introduction. Etiology

Refractive error explanation

1. Refractive Error

2. Refractive error means that the shape of your eye does not
bend light correctly, resulting in a blurred image. The main
types of refractive errors are myopia (nearsightedness),
hyperopia (farsightedness), presbyopia (loss of near vision
with age), and astigmatism.

Emmetropia Myopia Hyperopia Astigmatism

Normal Near-Sighted Far-Sighted Irregular Vision

3. on Means

Refraction is the bending of light as it passes through
one object to another. Vision occurs when light rays are
bent (refracted) as they pass through the cornea and the
lens. The light is then focused on the retina.

The retina converts the light-rays into messages that
are sent through the optic nerve to the brain. The brain
interprets these messages into the images we see.

|

Light
waves

4. e Blurred vision

e

e

e

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» Eye strain

Signs and Symptoms——

Double vision

Haziness (uncleared)

Glare or halos around bright lights
Squinting

Headaches

5. == =
Risk factor / Etiology

Genetics
e Marfan syndrome
e X-linked disorders
Environmental
e Reading has also been found to be a predictor of
myopia in children.
e Socioeconomic status and higher levels of education
have also been reported to be a risk factor for
myopia.

6. Types

7. a Myopia (nearsighte ness

It is a condition where objects up close appear clearly,
while objects far away appear blurry. For treatment use
concave lens

8. People with hyperopia can usually see distant objects well,
but have trouble focusing on nearby objects. For treatment
use convex lens

9. _—_ —
stigmatism

e It is a condition in which the eye does not focus light
evenly onto the retina, the light-sensitive tissue at the
back of the eye.

+ This can cause images to appear blurry and stretched out.

° Cylindrical error occurs when the incoming light rays are
unable to reach a common focus within the eye.

+ Astigmatism distorts or blurs vision for both near and far
objects.

10. Normal

[a - sphere sha, a
‚ornea phere shape SK vision

One focal
~ point

Cornea - oval shape x N Astigmatism

Multiple
- focal points

11. Presby

° It is an age-related condition in which the ability to focus
up close becomes more difficult.

e As the eye ages, the lens can no longer change shape
enough to allow the eye to focus close objects clearly.
When the flexibility of the lens declines, typically due to
age.

° The individual would experience difficulty in near vision,
often relieved by reading glasses, bifocal, or progressive
lenses

12. Presbyopia

Image behind
the retina
Lens hardened with age
and unable to change shape
Presbyopia corrected
Image on

the retina

13. ~ Diagnostic

Dilating Eye Drops

14. Retinoscopy
A hand held instrument called a retinoscope projects a
beam of light into the eye. When the light is moved
vertically and horizontally across the eye, the examiner
observes the movement of the reflected light from the
back of the eye.

15. + This reflection is called red reflex. The examiner then
introduces lenses in front of the eye and as the power
of the lenses changes, there is a corresponding change
in the direction and pattern of the reflection.

e The examiner keeps changing the lenses until reaching
a lens power that indicates the refractive error of the
patient.

16. Sen >
anagemen

» Refractive errors can be corrected with eyeglasses,
contact lenses, or surgery

» Eyeglasses are the simplest and safest way to correct
refractive errors.

17. e In many cases, contact lenses provide clearer vision, a
wider field of vision, and greater comfort. They are a safe
and effective option if fitted and used properly.

e It is very important to wash your hands and clean your
lenses as instructed in order to reduce the risk of infection.

18. The eye is anesthetized with An excimer laser is used to
topical eye drops. reshape the cornea.

The surgeon Creates a corneal The Corneal flap is replaced like
flap on the outer layer of the eye. closing the cover of a book.
It is cut and flipped open like

a cover of a book.