MYOPIA ASTIGMATISM ANISOMETROPIA ANISEIKONIA

1
MYOPIA
2
(No Transcript)
3
MYOPIA

• Short sightedness
• Myopia is a greek word meaning close the eye
• Refractive error I
• Parallel rays of light coming from infinity are
  focused in front of the retina.
• Accommodation is at rest

4

• Mechanism of production
• Axial
• Curvatural
• Positional
• Index
• Myopia due to excessive accommodation

5

• Optics of myopia
• Far point is finite (In front of the eye)
• Emmetropic eye it is at infinity
• Higher the myopia the shorter the distance
• Far point is 1mt from the eye ,there is 1D of
  myopia
• Nodal point is further away from retina

• Accommodation need not develop normally resulting
  in
• Convergence insufficiency
• Exophoria

6
TYPES OF CLASSIFICATION

• Clinical Classification
• Degree of Myopia
• Age of Onset

7
Clinical Classification

• Congenital Myopia
• Simple Myopia
• Degenerative Myopia
• Nocturnal Myopia
• Pseudo Myopia
• Induced Myopia

8
Degree of Myopia

• Low Myopia(lt3D)
• Medium Myopia(3-6D)
• High Myopia(gt6D)

9
AGE OF ONSET

• Congenital Myopia
• Youth-Onset Myopia(lt20 yrs of age)
• Early Adult-Onset Myopia(20-40 yrs of age)
• Late Adult-Onset Myopia(gt40 yrs of age)

10

• Congenital myopia
• Frequently seen in
• Premature babies
• Marfans syndrome
• Homocystinuria
• Increase in axial length
• Increase inOverall globe size
• Since birth, diagnosed at age 2-3 years
• If unilateral, as anisometropia, may develop
  amblyopia, strabismus
• Usually 8-10 D, remain constant
• Bilateral- difficulty in distant vision, hold
  things very close

11

• Associated conditions
• Convergent squint
• Cataract
• Microphthalmos
• Aniridia
• Megalocornea
• Congenital Separation of retina
• Management
• Early Correction is desirable
• Retinoscopy under full cycloplegia
• Early full correction desirable
• Poor prognosis

12

• Simple / developmental myopia
• Physiological error not associated with any
  disease of the eye
• Etiology
• Normal biological variation in development of eye
• Inheritence

13

• Associated factors
• Role of diet
• Theory of excessive near work

14

• Clinical picture
• Rarely present at birth
• Rather born hypermetropic, become myopic
• Begins at 7-10 years, stabilizing around mid
  teens
• Usually around 5D, never exceeds 8D

15

• Symptoms
• Poor vision for distance
• Asthenopic symptoms develop due to dissociation
  between accommodation and convergence
• Convergence weakness, exophoria, suppression
• Excessive accommodation inducing ciliary spasm
  and artificially increasing the amount of myopia
• Psychological outlook

16

• Signs
• Large and prominent
• Deep AC
• Large, sluggishly reacting pupils
• Normal fundus, rarely crescent
• Usually doesn't exceed 6-8D
• Retinoscopy under full cycloplegia

17

• Pathological / degenerative / progressive myopia
• Rapidly progressive associated with degenerative
  changes in the eye
• Etiology
• Rapid axial growth of the eyeball outside the
  normal biological variations of development
• Role of heredity
• Role of general growth process

18

• Genetic factors General growth
  process
• More growth of retina
• Stretching of sclera
• Increased axial length
• Degeneration of choroid
• Degeneration of retina
• Degeneration of vitreous

19

• Symptoms
• Defective vision
• Muscae volitantes / floating black opacities

20

• Signs
• EYE Large, prominent eyes simulating exophthalmos
• CORNEA large
• ANTERIOR CHAMBER deep
• LENS show opacities at the posterior pole due to
  aberration of lenticular metabolism and due to
  overstretching anterior dislocation may also occur

21

• VITEROUS degeneration,viterous liquefication,vitre
  ous detachment present as WEISS REFLEX
• SCLERA thinning resulting in formation of
  STAPHYLOMA
• VISUAL FIELD DEFECTS show Contraction and in some
  ring scotomas present

22

• DISC
• Large in size
• Myopic Crescent on the temporal side of the disc
• Choroidal Crescent
• Supertraction of the retina
• Inverse myopia Myopic crescent situated nasally
  and supertraction of the retina temporally
• called as INVERSE CRESCENT
• Peripapillary Atrophy

23

• MACULA
• Foster-Fuchs fleck
• RETINAL DETACHMENT
• POSTERIOR STAPHYLOMA
• RETINAL HOLES
• TESSELATED FUNDUS

24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27

• Treatment
• Optical treatment
• Appropriate concave lenses
• Minimum acceptance providing maximum vision

28
Guidelines

• LOW DEGREES OF MYOPIA (Up to -6D)
• IN YOUNG SUBJECTS
• Defect should never be overcorrected and
  advised for constant use to avoid squinting and
  develop a normal ACCOMMODATION-CONVERGENCE reflex
• IN ADULTS
• Receiving spectacle for the first time,have
  the ciliary muscle that are unaccostomed to
  accommodate efficiently so that lens of slightly
  lower power(1 or 2 D) may be prescribed for
  reading,especially if engaged in to any greater
  extent.Above the age of 40 years,when
  accommodation fails physiologically, a weaker
  glass for near work is essential

29

• HIGH DEGREES OF MYOPIA
• Full correction rarely be tolerated so we attempt
  to reduce the correction as little as is
  compatible with comfort for binocular vision. We
  prescribe the lens with which the greatest visual
  acuity is obtained without distress

30
(No Transcript)
31

• ADVANTAGES OF SPECTACLES
• Economical
• Allow incorporation of prism,bifocals,pal which
  can be used for the management of esophoria or
  any accommodative disorders accompanying myopia
• Spectacles require less accommodation than
  contact lens for myopia that likelihood of
  accommodative asthenopia or near point blur in
  patients approaching presbyopia may be less

32

• DISPENSING SPECTACLES IN HIGH MYOPIA
• High index lens materials
• Lighter lens materials
• Reduced eyesize of selected frames
• Minus lenticular lens designs

33

• ADVANTAGES OF CONTACT LENS
• Contact lens provides cosmosis
• Large retinal image size and slightly better
  visual acuity in severe myopia

34
SURGICAL TREATMENT
Phakic IOLS
RK

• Epikeratophakia
• RK
• PRK
• ISCR
• Phakic IOLS
• LASIK

PRK
LASIK
ISCR
35
Photorefractive Keratectomy (PRK)

• Involves direct laser ablation of corneal stroma
  after removal of corneal epithelium mechanically
  or using a laser beam.
• Done using Excimer laser
• MUNNERLYN EQN depth of ablation
  (micrometer)diameter of optical zone(mm)²
  1/3power(Diopter)
• For myopic a large amount of ablation is done in
  central cornea than in the periphery.
• Give good results for -2D to -6D of myopia

36
LASIKLaser Assisted In situ Keratomileusis

• MethodAnterior flap of cornea is lifted with a
  keratome and excimer laser is used to sculpt the
  stromal bed to change the refractive error of eye
  
• Corrects 0.5 to 12D of myopia and upto 8D of
  astigmatism
• GuidelinesAge more than 18yrs
• BCVA better than 6/12
• Stable refraction for last
  1yr
• Absence of corneal disease
  ectasia
• Note
• (1) In no case the residual bed thickness after
  the ablation should measure 250microns so as to
  avoid central corneal ectasia
• (2) Ideally the ablation should be done within
  30sec of the preparation of flap

37
LASEKLaser subepithelial Keratomileusis

• Indications
• Low myopia
• Irregular astigmatism
• LASIK complications in contralateral eye
• Thin corneal pachymetry
• Predisposition to trauma
• Glaucoma suspect

38

• Method
• Simple inexpensive procedure that involves
  creation of epithelial flap after exposure to 18
  alcohol for 25sec subsequent replacement of
  flap after laser ablation

39
RKRadial Keratotomy

• It refers to making deep corneal
  incisions(initially 16,now down to 4) in the
  peripheral part of cornea leaving about 4mm
  central optical zone
• The incisions are made almost down to the level
  of Descemets Membrane
• These incisions on healing flatten the central
  cornea thereby reducing its refractive power
• For low to moderate degree of myopia(-1.5 to
  -6D of myopia)

40
Epikeratophakia

• For high degree of myopia (upto 20D)
• Method
• The epithelium is removed then a pocket is
  fashioned under the edge of the remaining
  epithelium into this is inserted the cryolathed
  donor homograft
• Preserved material can also be used

41
NON CORNEAL INTERVENTIONS

• (A) REMOVAL OF CLEAR LENS
• We know that an aphakic eye is strongly
  hypermetropic
• If an eye with an axial myopia of -24D is
  deprived of its lens it will become emmetropic
  without any correcting lens
• Note
• Whenever surgery on clear lens is contemplated
  the eye is examined thoroughly for abnormalties
  like Raised IOP,Vitreous retinal degeneration
  etc

42

• (b)Phakic intraocular lenses
• An IOL of appropriate power is implanted inside
  the eye without touching normal crystalline lens
  thus without disturbing accomodation
• Method can be used to correct both myopia
  hypermetropia
• Phakic IOL types
• PC IOL
• Angle supported IOL
• Iris claw lens

43
INTRA CORNEAL RING(ICR) IMPLANTATION

• ICR implantation into the peripheral cornea
  approx.upto 2/3rd of stromal depth can also be
  considered for correction of myopia
• It results in a vaulting effect that flattens the
  central cornea decreasing the myopia
• The procedure has the advantage of being
  reversible

44

• For Further Queries Contact
• Ms. Priyanka Singh
• Head Optometry Service
• Email optometry_at_venueyeinstitute.org

45
Thank you