1. In the name of ALLAH, most gracious, most merciful

2. MYOPIA
BY: SUMAYYA NASEEM
Internee Optometrist

3. AIMS & OBJECTIVES OF TODAY’S LECTURE
• Myopia and its etiology
• Mechanisms of production
• Clinical types
• Signs & symptoms
• Complications
• Diagnosis
• Correction
• Prevention

4. HUMAN EYE:OPTICAL CONDITIONS
Emmetropia Ametropia
Index
Axial
Presbyopia
Curvature
Myopia Hyperopia Astigmatism
Parallel incident light is Parallel incident light is We get 2 focal points
focused in front of the retina focused behind the retina

5. • EMMETROPIA
Parallel incident rays come to a focus on
the retina when the accomodation is fully
relaxed so far point is at infinity.

6. OPTICS OF EMMETROPIA

7. •
AMMETROPIA
Parallel incident rays do not come to a focus
on the retina when the accomodation is fully
relaxed so far point is not at infinity.

8. MYOPIA
(short sightedness, hypometropia)
A type of refractive error in which Parallel
incident light is brought to a focus in
front of the retina when eye is at rest. So
far point is at finite distance.

11. AETIOLOGY
• Hereditary (Genetic Factor)
• Role of diet
• Theory of excessive near work
• Reading posture
• Racial (Chinese and Japanese highest)
• Environmental Factors

12. MECHANISMS OF PRODUCTION
1. Axial myopia
• Increased length of eyeball
• 1mm=3D
2. Curvature myopia
• Increased curve of cornea e.g. conical cornea
• Increased curve of lens e.g. lenticonus
• 1mm=6D

13. 3. Positional myopia
• Anterior displacement of lens e.g. trauma
4. Index myopia
• Increase in ref index of lens e.g. nuclear sclerosis in
diabetes
• Increase in ref index of aqueous humor
• Decrease in ref index of vitreous humor e.g. vitreous
liquefication
5. Myopia due to excessive accomodation
• Patients with excessive accomodation

14. MYOPIA: REFRACTIVE vs AXIAL
Refractive Myopia Axial Myopia
(Eye too long)
(Optics of the eye too strong)

15. Image of distant object & near object

16. CLINICAL VARIETIES OF MYOPIA
1. Congenital myopia
2. Simple or developmental myopia
3. Pathological or degenerative myopia
4. Acquired myopia

17. CLINICAL VARIETIES OF MYOPIA
1. Congenital myopia
• Present since birth
• Diagnosed at 2-3 years
• Common in children born with Marfan’s syndrome
• Mostly unilateral and anisometropic
• Rarely bilateral
• Usually 8-10 D and constant
• May be associated with aniridia, megalocornea and
congenital separation of retina

18. 2. Simple myopia
• Commonest
• Not associated with any eye disease
• Error usually does not exceed 6D
• Usually begins at age of 7 to 10 years
• Stabilizes around midteens

19. CLINICAL PICTURE
Symptoms
• Poor vision for distance

20. • Asthenopic symptoms
(due to dissociation b/w accomodation and
convergence)
• Change in physiological outlook of
children

21. SIGNS
• Myopic eyes are large
• Anterior chamber is deeper than normal
• Pupil is dilated and sluggish
• Fundus is normal
• Does not exceed 6D
• Normal near vision
• Defective distant vision

22. 3. PATHOLOGICAL MYOPIA
• Rapidly progressing error
• Associated with degenerative changes in posterior
segment
• Rapid axial growth of eyeball
• Usually Hereditary in nature
• Can exceed till 30 D
• Ref error increases 4D yearly
• Also known as degenerative myopia.

23. CLINICAL PICTURE
Symptoms
• Defective distant vision
• Defective near vision if degeneration starts
• Muscae volitantes (Flying Flies)
• Night blindness

24. MUSCAE VOLITANTES

25. SIGNS
• Prominent eyes
• Proptosis if error exceeds 20D
• Cornea large
• a/c deep
• Pupil large and sluggish
• Sclera is thin

26. Posterior
Subcapsular Cataract
Open-Angle Glaucoma
Idiopathic Retinal
Detachment
Chorioretinal
Degeneration

27. OPHTHALMOSCOPICALLY
Changes in vitreous
• Liquefication
• Floaters
• Vitreous detachment

28. POSTERIOR VITREOUS DETACHMENT

29. VITREOUS DETACHMENT

30. CHOROIDAL AND RETINAL CHANGES
• Degeneration of choroid
• Choroidal hemorrhage
• White atrophic patches
• Tilted disc
• Posterior staphyloma
• Myopic crescent (temporally)
• Forster-Fuchs flecks (subretinal neovascularisation &
pigmented lesion at or near the fovea)

31. POSTERIOR STAPHYLOMA

32. TILTED DISC

33. CHOROIDAL AND RETINAL DEGENERATIONS

34. MYOPIC CRESCENT

35. HIGHLY MYOPIC FUNDUS

36. COMPLICATIONS
• Retinal tears
• Retinal detachment
• Hemorrhages
• Complicated cataract
• Vitreous hemorrhage
• Primary open angle glaucoma
• Visual field shows contraction
• Scotoma can be seen

37. RETINAL DETACHMENT

38. RETINAL DETACHMENT

39. VISUAL FIELD LOSS

40. 4. ACQUIRED MYOPIA
Some causes are as follows:
1. Index myopia (diabetic, nuclear sclerosis)
2. Curvature myopia (conical cornea & corneal ectasias)
3. Positional myopia (ant. Subluxation of lens)
4. Consecutive myopia (surgical overcorrection)

41. 5. Night myopia (as pupil dilates)
6. Drug induced myopia
(pilocarpine, steroids)
7. Pseudo myopia (excessive & spasm of accomodation)

42. REFRACTION PROCEDURE
• VA with and without correction monocularly
• Pinhole VA
• Cover test with and without correction
• Quick ophthalmoscopy
• Retinoscopy
Subjective verification:
• Duochrome test
• Muscle balance- Maddox rod for distance

43. DISTANCE VA CHART
University of Waterloo
Bailey-Lovie Chart distance VA chart

45. RETINOSCOPIC FINDINGS
During retinoscopy of a
myopic patient, ‘against’
movement of reflex is seen as
compared to retinoscopic
light or streak.
Against movement is
neutralized by negative or
concave lenses.

46. Reflex motion seen during retinoscopy
“ w ith ” “ n e u tr a lity ” “ a g a in s t”

47. Retinoscopy Reflex

48. RETINOSCOPY: SET-UP

49. DUOCHROME TEST
Letters Circles

50. COVER/UNCOVER TEST

51. MADDOX ROD

52. PHOROPTER (MANUAL REFRACTOR)

53. VISUAL FUNCTIONS ASSESSMENT

54. OPTICAL CORRECTION OF MYOPIA
Options are as follows:
• Spectacles and LVD’s
• Contact lenses
• Refractive surgeries
• Laser
Others:
• Visual hygiene
• Prophylaxis
• General measures

55. SPECTACLES
• Minus lenses (CONCAVE) are used to correct myopia
• In high numbers glasses are not cosmetically attractive
and minify actual pt eye size for others
• Myopes are usually kept under corrected so that there
accomodation is not stimulated. Otherwise, they will
complain of Asthenopic symptoms

56. EXTREME MYOPIA

57. CONTACT LENS

58. Contact lens is a better option for correction of high
myopia both optically and cosmetically..

59. C/L INSERTION & REMOVAL

60. A SOFT C/L

61. LOW VISION DEVICES (LVD’s)
READING GLASSES

62. HAND MAGNIFIERS & STAND MAGNIFIERS

63. DOME/PAPERWEIGHT MAGNIFIER

64. FILTERS

65. TELESCOPES

66. ORTHOKERATOLOGY
• Orthokeratology is defined as, the reduction,
modification, or elimination of visual defect by
the programmed application of contact lenses

67. • Orthokeratology uses hard Contact Lenses to
remould the Cornea, to reduce or correct Myopic
(short-sighted) and Astigmatic (irregular surface)
errors of the eye.
• In some ways this is similar to the use of dental
braces by an Orthodontist to straighten crooked
teeth.
• The main difference is that if a tooth position is
corrected for some months it will stay in the new
position. However the Cornea is highly elastic, and
always returns to its original shape.
• For this reason the lenses are worn nightly or on
alternate nights after the ideal Corneal shape has
been achieved and removed in the morning giving
perfect vision without the need for spectacles or
contact lenses.

68. • Once the desired level of V.A has been
achieved a of retainer lens wear is initiated
until cornea reaches the level of stability new
shape cornea. Lens wear is then gradually
reduced to the minimum, required to attain
good functional vision through out the day.
• The amount of ametropia that can be
corrected using orthokeratology is: –1 to –6 D
myopia with 1.5 D of WTR astigmatism and
0.75 D of ATR astigmatism.

69. ORTHOKERATOLOGY CONTACT LENS

70. SURGERY
Clear lens extraction:
• For myopia of greater than 15-20 D, cataract
surgical procedure is applied and non-
cataractous lens is removed and intra ocular
lens of calculated power is inserted.
Phakic IOL:
• IOL is also placed in A/C or P/C of phakic
eyes to correct the refractive error.

71. CATARACT SURGICAL PROCEDURE

72. LASER AND SURGERIES

73. Photorefractive keratectomy PRK:
• Uses Excimer laser to change ant. curvature of
cornea.
• Tissue is ablated centrally 3.5-4mm and surface
curvature is reduced.
• After scarring, haloes, glare and reduction of best VA
are the complaints of patient.

74. PHOTOREFRACTIVE KERATECTOMY PRK

75. LASER ASSISTED IN SITU KERATOMILEUSIS
LASIK
• A mechanical keratotome is used to dissect through
the superficial corneal stroma and fashion a lamellar
circular flap of uniform thickness.
• The bared corneal stroma is reshaped using Excimer
laser and hinged flap is replaced.
• Better than PRK because of little scarring and better
correction predictability.

76. LASER ASSISTED IN SITU KERATOMILEUSIS
LASIK
Flap creation Laser intervention Flap repositioning

77. CORRECTION WITH LASIK & PRK
Myopia
• -1D to -6D --------- PRK
• -6D to -12D -------- LASIK
(better to wait till the patient reaches the age of 21 years)

78. EXCIMER SYSTEM

79. LASIK

80. EPIKERATOPHAKIA
• This uncommon surgical technique creates a
new corneal surface with a different surface
curvature by attaching a lenticule of pre-
shaped donor corneal stroma to the surface of
host cornea.
• The eye is not entered and procedure is easily
reversed by removal of lenticule.

81. EPIKERATOPHAKIA

82. KERATOMILEUSIS
• It is the use of microkeratotome to remove
lamella of ant. corneal stroma which is then
reshaped on a cryolathe before being
replaced.
• High degrees of myopia till 15D can be
corrected in this way.
• Keratophakia is developed as a modification
of keratomileusis and is used for aphakia.

83. KERATOMILEUSIS

84. PREVENTION & CONTROL OF MYOPIA
• Many people believe that too much close work, such
as reading or sitting too close to the television, causes
nearsightedness. But there was little evidence to
support this belief. However, one study suggested
that people in professions that involve extensive
reading have higher degrees of nearsightedness.
• With regular instillation, topical 0.05% atropine is an
effective agent for controlling myopia progression in
a majority of school aged children.

85. • Nutritional Factors
• Since the eye has a collagenous structure, it seems
likely that the same nutrients which strengthen
collagen might also be helpful in keeping the eye from
becoming elongated. Calcium, magnesium, boron,
silica, selenium, manganese and vitamin D all come
to mind, as well as vitamin C. A strong ocular
structure would likely be less prone to becoming
elongated, as occurs in myopia. Low levels of calcium,
fluoride and selenium were found to be related to
increased risk of progressive myopia in an
exploratory study.
• Vitamin E, can slow the progression of myopia in
children. Myopia in children was also significantly
related to lower consumption of protein, fat,
vitamins B1, B2 and C, phosphorus, iron, and
cholesterol.

86. VISUAL HYGEINE
• We should insist that our children use good lighting
and good posture when reading, take frequent eye
rest breaks during long study periods, and encourage
them to be physically active.
• Environmental visual stress may be lessened by
taking these precautions while reading: frequently
stretching and moving the eyes and looking away
from the reading material at distant objects,
removing distance eyewear(-) or using reading
glasses for near tasks.
• As it is usually hereditary in nature, so family
marriages should be avoided.

87. REFERENCES
• Theory and practice of optics and refraction
by A K Khurana
• Duke Elder's Practice of refraction (Tenth
edition)
• Clinical Optics by Elkington, Frank and
Greaney (Third edition)
• www.visionlaser.com
• www.orthokeratology.com
and many other websites.