Brief about myopia

1. Jyoti shah
SCEH, Lahan
Optometrist

2. Myopia
 Short sightedness
 myopia is a greek word meaning ‘’ close the eye”.
 Myopia is refractive defect of eye where parallel rays of
light coming from infinity are focused in front of retina
with accommodation is at rest.

3. Etiological classification
1. Axial myopia
➢ Commonest form
➢ Increase in anterior posterior length of the eyeball.
➢ If antero-posterior diameter of the eye is more than the
normal then it causes myopia (Normal axial length is
24mm).
➢ 1mm increasing will cause -3D myopia

4. 2. Curvatural myopia
 Increased curvature of cornea ,lens or both.
 1mm change lead to -6D refractive change.
 Increase corneal curvature give rise to Astigmatism.

5. 3.Index myopia
 Increased in refractive index of crystalline lens.
e.g. Nuclear Sclerosis,
Diabetes

6. 4.Positional myopia
 Produced by anterior placement of crystalline lens in the
eye.(dislocation of lens)
5. myopia due to excessive accommodation :occurs in
patients with spasm of accommodation.

7. Degree of myopia
 Low myopia (<-3D)
 Medium myopia (-3D to -6D)
 High myopia(>-6D)

8. TYPES OF MYOPIA CONTD…
Clinically,
 congenital myopia.
 simple or developmental myopia.
 pathological or degenerative myopia.
 acquired myopia.

9. Congenital myopia
➢ Since birth, Diagnosed by 2-3 years
➢ Increased axial length, overall globe size
➢ If unilateral as anisometropia may develop amblyopia,
strabismus
➢ Bilateral – difficulty in distant vision, holds things closer
➢ Usually error is 8-10 D, remains constant
➢ Frequently associated with Premature babies ,Marfan’s
syndrome

10.  May sometimes be associated with other congenital
anomalies such as cataract, microphthalmos, aniridia,
megalocornea.
 Management
Early full correction is desirable
Retinoscopy under full cycloplegia

11. Simple /developmental myopia
 Physiological, not associated with any eye disease
 Etiology
1. Normal biological variation in development
2. Inheritance
 Rarely present from birth
 Rather born hypermetropic become myopia
 Usually occurs at 5-10 years of age and keeps on
increasing till about 18-20 years of age
 Usually around -5D never exceed -6D to -8D

12. Symptoms
▪ Poor vision for distance(short sightedness)
▪ Asthenopic symptoms
▪ Half shutting of eyes
Signs
▪ large and prominent eyeballs
▪ Deep Anterior chamber
▪ Pupils- Large, sluggishly reacting
▪ Normal fundus ,rarely myopic crescent
▪ Usually does not exceed -6 to -8 D
Diagnosis
Confirmed by performing retinoscopy under full cycloplegia.

13. Pathological myopia
 Degenerative/ progressive myopia
 Rapidly progressive myopia associated with degenerative
changes
 Etiology
1. Rapid axial growth of the eyeball
2. Role of heredity
3. Role of general growth process

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

15. Symptoms
 Defective vision
 Muscae volitantes / Floating black opacities in front of
eyes
 Night blindness

16. Signs
 Eyes are prominent, large, and even stimulating an
exophthalmos.
 Cornea is large and anterior chamber is deep.
 Pupils are larger
 Refractive error:
increase by as much as 4.00D yearly
stabilizes at about the age of 20
but occasionally may progress until mid 30s`` frequently
result in myopia of 10-20D

17. ▪ Optic disc:
large disc with mild pallor
temporal crescent
▪ Macula: Dull, Foster-Fuchs spot
▪ Viterous degeneration, viterous liquefication , posterior
vitreous detachment present as WEISS Reflex.
▪ Scleral thinning resulting in formation of posterior
Staphyloma
▪ Visual field defect show Contraction and in some cases
ring scotomas present

18.  Posterior viterous
detachement

19. Fuch's spot Posterior staphyloma

20. Treatment
Optical treatment of myopia
Concave lenses( - lens)
Basic rule – minimum acceptance providing
maximum vision
Modes of prescribing concave lens
1. Spectacles
2. Contact lens(soft ,Rigid gas permeable)

23. Surgical treatment
➢ Radial keratotomy(RK)
➢ Photo refractive keratoplasty (PRK)
➢ Laser assisted stromal in situ keratomileusis(LASIK)
➢ Intra corneal ring (ICR)
➢ Fukala’s operation
➢ Minus phakic IOL
Low vision aids
➢ Indicated in patients of progressive myopia with
advanced degenerative changes where useful vision
cannot be obtained with spectacles and contact lenses.