L12.3 When things go wrong with our vision

Question 1

Optic factors affecting vision

Answer 1

• Things impeding on light into our eye
• Pupil
• Clarity of optical media
  
  • Cataracts, corneal opacities
• Refractive errors (long/short sighted)

Question 2

Refraction of light

Answer 2

• 60% occurs when light hits the corneal surface
  
  • Refractive index b/w air and cornea is greater than b/w aqueous and lens
• Lens refract remaining 40%

Question 3

Myopia (short-sighted)

Answer 3

• Eyeball too long for power of eye → causes focus to be too short and in front of retina
  
  • 1/3mm ↑ in length → ~1D myopia
  • Corrected with minus lenses → diverge light path

Question 4

Hypermetropia (long-sighted_

Answer 4

Opposite of myopia

Question 5

Astigmatism

Answer 5

• Eyeball normally steeper in one meridian or axis than the other
• Astigmatism → some light focus properly, some does not
• Need cylindrical lens

Question 6

Keratoconus

Answer 6

• Thinning of central cornea → Cornea is cone shaped
• Marked irregular astigmatism

Question 7

Age related macular degeneration (AMD): Dry

Answer 7

• Loss of cells forming the retina
• Causes gradual vision loss

Question 8

AMD: Wet

Answer 8

• More serious (10% of patients)
• BV grow out of control into fovea → into retina → destroys it
• Quick onset and damage

Question 9

Pathogenesis of AMD

Answer 9

• Environment: Age, smoking (x4 risk), diet, Light
• Genetic: Immune system genes/lipid transport

Question 10

Treatment

Answer 10

• Requires monthly injection into the eye
• But is able to be treated

Question 11

Structure changes in early AMD

Answer 11

• Retinal pigment epithelium
• Bruch’s membrane
  
  • Potential treatment/target for early AMD

Question 12

Nanolaser

Answer 12

• Target the blobs at the back of eye in early AMD
  
  • Reduces thickness of Bruch’s membrane (b/w retina and choroid) → retina able to get nutrients easier
• Under clinical trial to see if it stops progression of AMD