Myopia

1. MYOPIA
PRESENTER – DR. OM PATEL
MODERATOR – DR. SURYAKANT JHA

2. MYOPIA
 SHORT SIGHTEDNESS
 Condition in which incident parallel rays come to a
focus anterior to the light sensitive layer of retina
with accomodation at rest.

3. OPTICS OF MYOPIA
 The optical system is too powerful for its axial
length
 Image of distant object on retina is made up of
circle of diffusion formed by divergent beam since
the parallel rays of light coming from the infinity
are focused in front of the retina

4. Far point is finite point in front of eye

5. OPTICS OF MYOPIA
 Accommodation in uncorrected myopes is not
developed normally
May suffer from convergence insufficiency
and exophoria
 Early presbyopia

6. ETIOLOGICAL CLASSIFICATION
 Axial : most commonest
 1mm = 3D
 Curvatural :
 Increased corneal or lens curvature
 1mm = 6D

7. ETIOLOGICAL CLASSIFICATION
 Positional :
 Dislocation of lens
Myopia due to excessive accommodation :
 Spasm of accommodation,
 Suspensory lig. Rupture

8. ETIOLOGICAL CLASSIFICATION
 Index myopia :
 Change in the R.I. of the crystalline lens
eg : Nuclear Sclerosis,
Incipient Cataract,
Diabetes.

9. DEGREE OF MYOPIA
Low Myopia(<3D)
Medium Myopia(3-6D)
High Myopia(>6D)

10. CLINICAL VARIETIES
 Congenital myopia
 Simple or developmental myopia
 Pathological or degenerative myopia

11. CONGENITAL MYOPIA
 Frequently associated with
 Premature babies
 Marfan’s syndrome
 Homocystinuria
 Since birth,Diagnosed by 2-3 years
 Increased axial length, overall globe size
 If unilateral may produce amblyopia, strabismus
 Bilateral – difficulty in distant vision, holds things closer
 Usually error is 8-10 D, remains constant

12. CONGENITAL MYOPIA
Associated wi th
 Cataract
 Micropthalmos
 Aniridia
 Megalocornea
 Congenital separation of retina
Management
 Early full correction
 Retinoscopy under full di latation

13. SIMPLE MYOPIA
 Developmental myopia- commonest variety
 School myopia (school going age 8-12 years)
 Physiological, not associated with any eye disease
 Normal biological variation in development
 Rarely present from birth, rather hypermetropia
followed by myopia

14. CLINICAL PICTURE
Symptoms
 Poor vision for distance(short sightedness)
 Asthenopic symptoms
 Half shutting of eyes

15. Signs
 Prominent eyeballs
 Anterior chamber - deeper than normal
 Pupils- Large, sluggishly reacting
 Fundus- normal; rarely temporal myopic crescent may be
seen
 Magnitude of refractive error
 Increasing at rate -0.5 +- 0.30/ year.
 Does not exceed -6 to -8 D
Diagnosis
Confirmed by performing retinoscopy

16. PATHOLOGICAL MYOPIA
 Degenerative/ progressive myopia
 Rapidly progressive myopia associated with
degenerative changes
 Starts in childhood at 5-10 years of age

17. ETIO-PATHOGENESIS
Genetic factors (play major role)
General growth process(minor)
More growth of retina
Stretching of sclera
Increase axial length
Degeneration of choroid
Degeneration of retina
Degeneration of vitreous

18.  Defective vision
 Muscae volitantes
SYMPTOMS
 Floating black opacities in front of eyes
 Degenerated liquified vitreous

19.  Prominent eye balls
SIGNS
 Elongation of eye ball mainly affects posterior pole
and surrounding area
 Cornea-large
 Anterior chamber –deep
 Pupils-slightly large,react sluggishly to light
 Lens
 Opacities at the posterior pole due to aberration of
lenticular metabolism
 Anterior dislocation due to overstretching

20. Fundus examination:
Optic disc
 Large and pale
 Temporal edge presents a characteristic MYOPIC CRESCENT
 SUPER TRACTION CRESCENT may be present on nasal side
(retina pulled over disc margin)
 Peripapillary crescent encircling the disc may be present, where
choroid and retina is distracted away from disc margin

23. Degenerative changes in retina and choroid
 White atrophic patches at macula with a little
heaping of pigment around them

24. • FOSTER-FUCH’S
SPOT:
• Dark red circular
patch due to sub-retinal
neo
vascularization
and choroidal
haemorrhage
• Present at macula
• CYSTOID
DEGENERATION
– at periphery

26.  Posterior staphyloma
 Due to ectasia of sclera at posterior pole
 It may be apparent as an excavation with vessels
bending backward over margins

27.  Degenerative changes in vitreous
 Liquefaction
 Vitreous opacities
 Posterior vitreous detachment(PVD)- Weiss’ reflex

28.  Visual fields
 Contraction
 Ring scotoma may be seen
 ERG reveals subnormal electroretinogram due to
chorioretinal atrophy

29. COMPLICATIONS
 Retinal detachment
 Complicated cataract
 Vitreous haemorrhage
 Choroidal haemorrhage
 Strabismus fixus convergence

30. TREATMENT OF MYOPIA
Optical treatment of myopia
 Concave lenses
 Basic rule – minimum acceptance providing maximum
vision
 Modes of prescribing concave lens-
1. Spectacles
2. Contact lens

31.  Contact lenses are used in case of high myopia as they
avoid peripheral distortion and minification produced
by strong concave spectacle lens

32. SURGICAL TREATMENT OF
 Radial keratotomy
 Photo-Refractive keratectomy (PRK)
 LASIK
 Fucala’s lens extraction
 ICL (Implantable Collamer Lens) or Phakic IOL
 ICR ( Intra Corneal Ring implantation)
 Orthokeratology
MYOPIA

33. SURGICAL TREATMENT OF
MYOPIA
 Radial keratotomy
 Obsolete now a days
 Making deep radial incisions in peripheral part of
cornea leaving the central a 4mm optical zone
 These incisions on healing ; flatten the central
cornea thereby reducing its refractive power
 Correct low to moderate myopia(2-6D)
DISADVANTAGES:
 Cornea is weakened – globe rupture in sports persons
 Uneven healing – irregular astigmatism
 Patient may feel glare at night

35. Photo refractive
keratectomy (PRK)
 A central optical zone
of anterior corneal
stroma is photoablated
using excimer laser
(193nm uv flash) to
cause flattening of
central cornea
 Correction for -2 to -
6D of myopia

36. Disadvantages:
• Post operative recovery is slow
• Pain and discomfort
• Residual corneal haze in centre affecting vision
• Expensive

37. LASER ASSISTED IN-SITU
KERATOMILEUSIS(LASIK)
 Refractory surgery of choice for myopia of upto -12D

38. Flap of 130-160 micron thickness of
anterior corneal tissue is raised
Midstromal tissue is ablated
directly with an excimer laser beam
ultimately flattening the cornea

40. PATIENT SELECTION
CRITERIA
1. Patients >20 years
2. Stable refraction for at least 12 months
3. Absence of corneal pathology
 Absolute contraindication for LASIK
 Corneal thickness <450 micrometers
 Presence of ectasia

41. ADVANCES IN LASIK
 Customised(C)-LASIK:
 Based on wave front
technology
 Corrects spherical,
cylindrical and other
aberations present in eye
 Gives vision beyond 6/6
i.e.,6/5 or 6/4

42.  Epi-(E) LASIK:
 Only epithelial sheet is
separated with Epiedge
Epikeratome
 Devoid of complications
related to corneal
stromal flap

44. ADVANTAGES OF LASIK
 Minimal or no postoperative pain
 Recovery of vision is very early as compared to PRK
 No risk of perforation during surgery and rupture of
globe due to trauma like RK
 No residual haze unlike PRK where subepithelial
scarring may occur
 LASIK is effective in correcting myopia of -12D

45. DISADVANTAGES
 Expensive
 Requires greater surgical skill than RK and PRK
 Flap related complications
 Intraoperative flap amputation
 Wrinkling of flap on repositioning
 Postoperative flap dislocation/subluxation
 Epithelization of flap – bed interface
 Irregular astigmatism

46. EXTRACTION OF CLEAR
CRYSTALLINE LENS
 Fucala’s operation
 Myopia of -16D to -18D in unilateral cases
 Clear lens extraction with intraocular lens implantation
of appropriate power is the refractive surgery for
myopia of >-12D

47. PHAKIC INTRAOCULAR LENS
(ICL)
 Intraocular contact lens implantation for correction of
myopia of >-12D
 Special type of IOL is implanted in anterior chamber
or posterior chamber anterior to natural crystalline
lens

48. INTRACORNEAL RING (ICR)
IMPLANTATION
 Into the peripheral cornea at approximately 2/3rd
stromal depth
 Flattening of central cornea, decreasing myopia
 Advantage: reversible procedure

49. ORTHOKERATOLOGY
 A non-surgical reversible method of moulding the
cornea with overnight wear unique rigid gas permeable
contact lenses
 Myopia correction upto -5D
 Used in patients below 18 years of age