Refractive errors are common eye disorders where the eye fails to properly focus light on the retina, leading to blurred vision. The main types include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, each caused by different factors such as the shape of the eyeball or curvature of the lens. Treatment options involve corrective lenses or surgical procedures, depending on the severity and type of refractive error.

1. ERRORS OF
REFRACTION

2. INTRODUCTION
⚫Refractive disorders are abnormalities of
refraction that occur in the eye. Refraction
results in the focusing of image on the retina
of the eye, permitting vision. In refractive
errors, vision is impaired because a
shortened or elongated eyeball prevents light
rays from focusing sharply on the retina.
Blurred vision from refractive errors can be
correctly with eyeglasses or contact lenses.

3. DEFINITION
⚫A refractive error is a very common eye
disorder. It occurs when the eye cannot clearly
focus the image from the outside world. The
result of refractive error is blurred vision
which is sometimes so severe that it causes
visual impairment.
⚫Refractive error also known as refraction error
is a problem with focusing light accurately on
the retina due to the shape of eye.

4. EMMETROPIA
⚫Emmetropia ( optically normal eye) can
be defined as a state of refraction, when
the parallel rays of light coming from
infinity are focusing at the sensitive layer
of retina with the accommodation being
at rest.

5. AMETROPIA
⚫Ametropia ( a condition of refractive
error), is defined as a state of refraction,
when the parallel rays of light coming
from infinity, (with accommodation at
rest), are focussed either in front or
behind the sensitive layer of retina.

6. TYPES OF
REFRACTIVE
ERROR
The types of refractive errors are:
• Myopia
• Hyperopia
• Astigmatism

7. MYOPIA
⚫It is near sightedness also known as short
sightedness.
⚫It is a type of refractive error in which parallel rays of
light coming from infinity are focussed in front of the
retina when accommodation is at rest.
⚫Myopia is a condition of the eye where light focuses
in front of the retina instead of on the retina this
causes distant objects to be blurred while close
objects appear normal.

8. Normal vision Myopia

9. ETIOLOGY OF MYOPIA
⚫Axial myopia results from increase in the antero-
posterior length of the eyeball.
⚫Curvatural myopia occurs due to increased
curvature of the cornea, lens or both.
⚫Index myopia results from increase in the
refractive index of the crystalline lens associated
with nuclear sclerosis.

10. PATHOPHYSIOLOGY
Due to etiology factor
degenerative changes causes by gradual loss of
elasticity of lens
Which leads to decreased ability to accommodate
Then lead to refractive error

11. TYPES OF MYOPIA
Congenital Myopia
Degenerative
Myopia
Simple Myopia

12. CONGENITAL MYOPIA
⚫Congenital myopia is present since birth. Usually the
error is of about -8 to -10 diopters, which mostly
remains constant . It may be associated with other
ocular congenital anomalies. Ex: cataract,
megalocornea, aniridia and microphthalmos.

13. SIMPLE MYOPIA
⚫It is the commonest variety, which results from
normal is starts biological variation in the
development of eye. Simple myopia starts at school
age and very slowly progresses till adult age. Usually
the error does not exceed -6 to -8 diopters.

14. DEGENERATIVE MYOPIA
⚫Pathological myopia or degenerative myopia is a
rapidly progressive error resulting in high myopia of
-20 D or more. It is strongly linked with heredity.

15. CLINICAL MANIFESTATION
⚫ There is reduced visual acuity for the distance of but near
objects are seen clearly. Usually there is no headache.
⚫ In pathological myopia, the patient may complain of seeing
black spots floating in front of the eye, due to vitreous
opacities.
⚫ Ophthalmoscopically, the typical changes seen in the high
myopia are: myopic crescent either on the temporal side of
the optic disc or surrounding the disc and chorio-retinal
myopic degeneration or atrophy at the periphery.
⚫ In vary high myopia the eye are prominent (pseudoproptosis),
the pupils are large and vision may be very poor even with
optical correction.

16. MANAGEMENT
⚫Concave lenses in the form of glasses or contact
lenses.

17. SURGICAL MANAGEMENT
⚫Radial keratotomy: Multiple radial incisions are
given in the periphery of cornea in order to flatten
the curvature of cornea.

18. • Lasik laser: Laser assisted in situ the
preferred surgical technique for correcting
myopia of up to -12 D. The midstromal tissue
is ablated with excimer laser after raising a
130-160 micron thick flap of anterior corneal
tissue.
• Removal of clear crystalline lens: Removal
of lens extra capsular cataract extraction
(phacoemulsification) with IOL implantation
of appropriate power is being
recommended.

19. HYPEROPIA
⚫Hypermetropia (hyperopia) or long sightedness is
the refractive state of the eye where in parallel rays
of light coming from infinity are focussed behind the
retina with accommodation being at rest. Thus the
posterior focal point is behind the retina, which
therefore receives a blurred image.

20. ETIOLOGY
⚫Axial hyoermretropia is by far the commenest
form. It occurs due to short axial length of the eyeball.
⚫Curvatural hypermetropia occurs due to
comparatively flatter curvature of the cornea or lens or
both.
⚫Index hypermetropia results due to change in the
refractive index of the lens.
⚫Absence of the lens (aphakia) either congenital or
acquired (following surgical removal of the lens) leads
to high hypermetropia.

21. CLINICAL FEATURES
⚫Tiredness of eyes
⚫Frontal or frontotemporal headache
⚫Watering
⚫Mild photophobia

22. MANAGEMENT
⚫Appropriate convex lenses in the form of spectacles
or contact lenses.

23. SURGICAL MANAGEMENT
⚫Refractive corneal surgery

24. ASTIGMATISM
⚫Astigmatism is a type of refractive error where in the
refraction varies in the different meridia of the eye
consequently, the ray of light entering in the eye
cannot converge to a point focus but form focal lines.

25. ETIOLOGY
⚫Usually occurs due to unequal curvature of cornea.
⚫Rarely it may occur due to subluxation abnormalities
of the curvature of the lens.

26. SIGN AND SYMPTOMS
⚫Blurred vision
⚫Eye strain and eye fatigue
⚫Headache
⚫Dizziness
⚫Vomiting

27. TYPES OF ASTIGMATISM
REGULAR
ASTIGMATISM
IRREGULAR
ASTIGMATISM

28. MANAGEMENT
⚫Cylindrical lenses in the form of spectacles or contact
lenses.

29. PRESBYOPIA
⚫Presbyopia (eyesight of old age ) is not an error of
refraction, but a condition of physiological
insufficiency of accommodation, leading to failing
vision for near.
⚫It is usually occurs after 40 years of age.

30. ETIOLOGY
⚫ Decrease in the accommodation power of crystalline lens
with increasing age, leading to presbyopia occur due to:
⚫ Decrease in the elasticity and plasticity of the crystalline
lenses.
⚫ Age related decrease in the power of ciliary muscle.
⮚ Causes of premature presbyopia:-
• Hypermetropia
• Primary open- angle glaucoma
• Premature sclerosis of the lens
• Excessive close work

31. SIGN AND SYMPTOMS
⚫A tendency to hold reading material farther away to
make the letter clearer.
⚫Blurred vision at normal reading distance.
⚫Eye strain or headache after reading or doing close
up work .

32. MANAGEMENT
⚫Convex glasses of an appropriate power :
▪At the age of 40 years – reading correction is + 1D.
▪At the age of 45 years - reading correction is +1.5D.
▪ At the age of 50 years - reading correction is +2D.
▪At the age of 55 years - reading correction is +2.5 D.

33. DIAGNOSTIC EVALUTION
• History collection
• Physical examination
• Snellens
chart
• ophthalmoscopy

34. • retinoscopy • autorefractometry

35. SUMMERY
⚫Refractive error are disorders, not disease.
⚫A refractive error means that the shape of eye
doesn’t bend light correctly, resulting in a blurred
image.
⚫Types of refractive error are:
1. Myopia : near sightedness
2. Hyperopia :far sightedness
3. Astigmatism :Irregularly shaped cornea, causing
blurred vision.