Myopia clinical features and treatment Topic 17
= short-sightedness , focusing is before retina due to refracting error
Causes
- 1. Axial myopia → increase in anteroposterior length of eyeball
- 2. Curvatural → cornea/lens more cure than normal
- 3. Positional→ anterior placement of lens (convergence occurs before it should)
- 4. Index → Increase in refractive index due to nuclear sclerosis
- 5. Excessive accommodation → in patients with spasms
Clinical classification
- a. Congenital → since birth /congenital anomalies ,usually unilateral (anisometropia)
- b. Simple/developmental→most common , physiological error
Symptoms : poor vision for distance , asthenopic symptoms ,half shutting of eye
Signs: prominent &larger eyeballs , anterior chamber is slightly deeper, pupils are larger
Fundus is normal and confirmed by retinoscopy
c. Pathological → rapidly progressive error because of rapid growth of the eyeball ; which could be hereditary =stretching of sclera which due to excess growth of retina, this leads to increase in axial length but also degen. of choroid,retina&vitreous
Symptoms→ defective vision + floating black opacities complaint (dege.viterous) night blindness if degenerative changed are large
Signs: prominent eye, cornea large, anterior chamber deep, pupil larger.
Fundus examination shows :
Optic disk changes: temporal myopic crescent , degen. changes in retina &choroid characterised by Foster-Fuchs’s sport = dark red circular patch due to sub-retinal neovascularisation +choroidal haemorrhage) + macular degeneration
Posterior Staphyloma due to ectasis of sclera
Degen.changes of vitreous= liquefaction, opacities, detachment
Visual field contraction +scotoma possible
Complications: retinal detachment, complicated cataract, vitreous/ choroidal haem.
Treatment of Myopia→ the same procedures and techniques as in hypermetropia but with concave lenses