OPTOMETRY

1. MYOPIA
OPTOM.ASKAR.PK

2. Refractive Errors

3. Refractive status of the eye
 The ocular refractive status refers to the locus
within the eye conjugate with optical infinity
during minimal accommodation.* Under these
conditions:
 In an emmetropic eye, incident parallel rays of
light are brought to a focus upon the retina.
 In a hyperopic (or hypermetropic) eye, incident
parallel rays of light are brought to a focus behind
the retina.
 In a myopic eye, incident parallel rays of light are
brought to a focus in front ofthe retina.

4. Refractive status of the eye
 Ametropia, or the absence of emmetropia,
may be produced by variations in:
1. The relative location of the optical elements of
the eye with respect to the retina.
2. The relative refractive power of the optical
elements with respect to the location of the
retina

5. Refractive errors
Ametropia: a refractive error is present
• Myopia: Near sightedness
• Hyperopia(Hypermetropia): Far sightedness
• Astigmatism: the curvature of the cornea and/or lens is not sphericaland
 therefore causes image blur on the retina

6. Refractive errors
• Anisometropia: a refractive power difference between
the 2 eyes (> 2D)
• Aniseikonia: a difference of image size between the 2
eyes as perceived by the patient
• Aphakia: (Phakos=lens), aphakia is no lens
• Pseudophakia: artificial lens in the eye

7. Myopia

8. Myopia

9. Myopia
 Results from an eye having excessive
refractive power for its axial length.
 This may be due either to the eye having
a relatively long axial length or to
increased dioptric power of one or more
of the refractive elements.

10. Myopia
 Term myopia was derived by Galen from the
words myein ("to close") and ops ("eye").
 Galen observed that nearsighted people partially
closed their eyes to see better.

11. Optics Of Myopia
 In myopia the eyeball is usually deformed ; the
deformation occurs at the posterior part of the
globe only ,the anterior part is normal. The eyeball
is usually large and looks prominent. When
adducted the equator can be seen.

12. Optics Of Myopia

13. Classifications
 Rate of myopic progression
 Anatomical features of myopia
 Degree of myopia
 Physiological and pathological myopia
 Hereditary and environmentally induced myopia
 theory of myopic development
 Age of myopia onset

14. Rate of myopic progression- Donders
Three categories of myopia:
 Stationary: Stationary myopia is generally of low degree (-1.50
to -2.00 D) and arises "in the years of development. remains
stationary during adulthood
 Temporarily :early teens and progresses until the late 20s.
After this age, the rate of myopia progression approaches
zero.
 Permanently progressive:. Permanently progressive myopia
ascends rapidly until around 25 to 35 years of age, and
thereafter advances more slowly.

15. Based on Anatomical features
 Axial: increased Axial length of eyeball
 Refractive:refractive system is too powerful for
the axial length of the eye.
Boris further divided in to Ref.Myopia into:
1. Curvatural- reduced radius of curvature of one
or more refractive surfaces produces increased
dioptric power.
2. Index-one or more ofthe refractive indices
ofthe media are anomalous.increased
refractive index of lens withnuclear sclerosis
3. Anterior chamber myopia:deeper in anterior
chamber depth increases the refractive power
of the eye

16. Degree of myopia
 Low (<3D)
 Medium –(3-6D)
 High – (>6D)

17. Physiological and Pathological
Myopia
 Physiological myopia: in which each component of
refraction lies within the normal distribution for that
population.
 Physiological/school myopia
 Commonest type
 Results due to normal biological variations in developmentof eye
 Age of onset- 7-10yrs
 Moderate severity-<5D,neverexceeds8D
 No degenerativechanges

18. Pathological myopia
 Refractive anomalies determined by the presence in the
optical system of the eye of an element which lies outside
the limits of the normal biological variations.
 Malignant or degenerative myopia - degenerative
changes, particularly in the posterior segment of the
globe.
 Most frequently found in high (>6 D) degrees of myopia
 Age of onset-early adultlife
 Progressive in nature

19. Pathological myopia
 Also called degenerative/ progressive myopia
 Related to heredity
 Increased axial length, degenerative changes in
retina, choroid, vitreous changes

20. Classification Based on Age of
Onset
 myopia on the basis of the subjects' age at the time of
reported myopia onset.
1. Congenital myopia-Myopia is present at birth and persists
through infancy
2. Youth-onset myopia -The onset of myopia occurs between 6
years of age and the early teens.
3. Early adult-onset myopia -The onset of myopia occurs
between 20 and 40 years of age.
4. Late adult-onset myopia -Myopia onset occurs after 40 years
of age.

21. Congenital myopia
 Common in premature babies or with birth
defects
 Stationary(8-10D)
 Associated with
 Increase in axiallength
Esotropia
Other congenital anomalies of eye
 Early and full correction under
cycloplegia Poor prognosis in unilateral
cases with severe
 myopia and anisometropia

22. Other types myopia
 Night myopia: increased myopia under low
iluminance conditions was first reported in 1789.
produced by an increased accommodative
response (typically on the order of 0.50 to 1.00 D)
under degraded stimulus conditions.
 Pseudo myopia: results from a spasm of the ciliary
muscle

23. Pathological changes in
myopia
 Optic disc appear large and pale
 Degenerative changes in retina & choroid
 Vitreous degeneration
 Posterior staphyloma

24. Myopic Crescent

25. Lacquer Cracks
Breaks in Bruch’s membrane

26. Foster – Fuchs's spots

27. Sub retinal neovascularization

28. Sub retinal hemorrhage

29. Posterior staphyloma

30. Complications
Macular hemorrhage
Retinal tears, detachment
Vitreous hemorrhage
Choroidal hemorrhage
Complicated cataract
Nuclear sclerosis
Primary open angle glaucoma

31. Clinicalfeatures-Symptoms
Distant blurred vision
Half shutting of eyes
Asthenopic symptoms
Floating black opacities infront of the
eye
Night blindness
Divergent squint

32. Signs
Prominent eyeballs
Large cornea
Anterior chamberis deep
Large &sluggishly reacting pupil
Fundus examination-changes seen only in
pathological myopia

33. Opticaltreatment
Concave lenses
Children
Adults
Contact lenses

34. Optical treatment
Minimum acceptance providing maximum vision
Low myopia(<6D):
 Young children : glasses required only if
Isometropia
<2years ≥ -4.0D
2-3years ≥ -3.0D
Anisometropia:
≥ -2.5D
Give full correction under cycloplegia
Avoid overcorrection

35. Adults:
 <30years-full correction
 >30years-less than full correction with which patient
is
comfortable for nearvision.
HIGH MYOPIA
 under correction is done to avoid
near vision problem
minification of images
contact lenses are better(to avoid image minification)

36. Surgicaltreatment
Radial keratotomy
Lamellar corneal refractiveprocedures
Laser based procedures
PRK
LASIK
LASEK
C-LASIK
E-LASIK

37. Miscellaneous corneal refractiveprocedures
Orthokeratology
Intracorneal contact leses
Intra stromal corneal ring segments
Gel injectable adjustable keratoplasty
Intraocular refractiveprocedures
Phakic refractive lenses
Refractive lense exchange

38. Thank you