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Ophtha > Refractive Errors > Flashcards

Refractive Errors Flashcards

1
Q

Refractive power of eyeball

A

+60(58.6)

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2
Q

What is near reflex or accommodation triad?

A
  1. Convergence of eyeballs by medial rectus
  2. Miosis by sphincter pupillae
  3. Accomodation by ciliary muscles-increase in Anterior curvature of lens.
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3
Q

Types of Myopia

A
  1. Axial-Path,Buphth,post staph
  2. Index-nuclear cataract
  3. Positional-ant dislocation/subluxation nd Weil march
  4. Curvatural-corneal or lens
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4
Q

Symptoms of myopia

A
  1. Defective far vision/near sightedness

2. Floaters(muscae volitantes)

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5
Q

Signs of eye in myopia

A
  1. Large eyeball-blue thin sclera
  2. Cornea-large
  3. AC-deep
  4. Exophoria
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6
Q

What is fundus?

A

View of all structures in the post segment 1.vitreous nd retina transparent 2.Choroid(red)

*viewed with ophthalmoscope.

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7
Q

Fundus signs in myopia

A
  1. Myopic temporal crescent around optic disc
  2. Optic disc tilted
  3. Lacquer cracks
  4. Foster fuch’s spots
  5. Posterior staphyloma
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8
Q

Overall appearance of fundus in myopia

A

Tessellated or Tigroid appearance d/t diffuse alterations in RPE

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9
Q

Other retinal findings in myopia

A
  1. Lattice degeneration
  2. Rhegmatogenous RD
  3. Retinal tears
  4. Vitreous deatchment - Seen as WEISS rings
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10
Q

Complications of path myopia

A
  1. RD
  2. Complicated cataract-post subcapsular
  3. Vitreous hmg nd choroid also hmg
  4. PAOG- more like an association
  5. Strabismus fixes convergence
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11
Q

Fundus signs nd complications are absent in?

A

Simple or developmental myopia

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12
Q

What are the zones of chorioretinal atrophy

A

2 zones:

  1. Alpha-always seen in glaucoma
  2. Beta-TMC
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13
Q

Laser surgeries in myopia

A
  • Corneal based
    1. Radial keratotomy
    2. PRK with excimer laser
    3. LASIK with excimer or femto(upto -8₹
    4. Smile(upto -10D)
  • Lens based
    1. Clear lens extraction-Fucala sx (for >-12D)
    2. ICL
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14
Q

Types of Hypermetropia

A
  1. Axial-Newborn,micro,nano
  2. Index-cortical sclerosis
  3. Positional-post dislocation
  4. Curvatural-cornea plana
  5. Aphakia
  6. Overcorrected Myopia in refractive Sx or Undercorrected IOL in cataract Sx
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15
Q

Symptoms of Hmt

A
  1. Defective near vision

2. Asthenopic symptoms(over active near reflex)

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16
Q

Signs of Hmt

A
  1. Small eyeball
  2. AC shallow
  3. ESOTROPIA
17
Q

Fundus signs in Hmt

A
  1. Pseudopapillitis

2. Shot silk fundus

18
Q

Complications of Hmt

A
  1. Recurrent styles,chalazia
  2. Accomodation convergent squint
  3. Amblyopia
  4. PACG- prevent mydriatic use in elderly hypermetropes
19
Q

Management of Hmt

A
  1. Convex(+) sphere spectacles
  2. Contact lens-U/L Hmt
  3. Surgery-1.Cond keratoplasty-radiofreq,upto 3D
    2. Thermal keratoplasty=THC-YAG laser
    3. Hyperopic laser-upto +4D
  4. Lens based-1.ICL upto +4D
    2. Refractive lens exchange-mainly in presbyopes
20
Q

What is astigmatism?

A

A cylindrical refractive error in which both the horizontal nd vertical meridians have different refractory power.

21
Q

Types of regular astigmatism?

A
  1. Simple myopic
  2. Simple Hypermetropic
  3. Compound myopic
  4. Compound Hypermetropic
  5. Mixed
  6. With the rule
  7. Against the rule
  8. Oblique
22
Q

Causes of astigmatism?

A
  1. Corneal
  2. Lenticular
  3. Retinal/Macular
23
Q

Symptoms nd signs nd investigationsof regular astigmatism

A
  1. Asthenopia
  2. Elongation of objects
  3. Reading close to eyes
  4. Half closure of lids
  5. Head tilt

Ix

  1. Retinoscopy-2 diff refr powers in 2diff axes
  2. Keratometry-diff corneal curvatures in 2 principal meridians
  3. Astigmatic fan test
  4. Jackson cylinder test
24
Q

Management of regular astigmatism

A
  1. Spectacles cylinder convex/concave
  2. Contact lens-rigid/soft/Toric
  3. Surgical-1.Astigmatic keratectomy(AK)
    2. Limbal relaxing incisions(LRI)-upto +2D
    3. Corneal “ “ (CRI)- “
    4. PARK-photoastigmatic refractive keratotomy
    5. Astigmatic LASIK-upto +5D
    6. smile
25
Q

Lens used in astigmatism

A

Convex-plus-steep axis

Concave= - =flat axis

27
Q

Mx of post keratoplasty astigmatism

A
  1. Selective removal of sutures in steep meridians-1st performed
  2. Arcuate relaxing incisions along steep meridians-upto 4-6D
  3. Relaxing incisions comb with compression - upto 10D
  4. Corneal wedge resection with suture closure of wound in flat meridian.
    - > 10D
  5. LASIK
28
Q

Symptoms nd signs of irregular astigmatism

A
  1. Defective vision
  2. Distortion of objects
  3. Polyopia
  4. Retinoscopy-irregular pupillary reflex
  5. Slit lamp-corneal irregularity
  6. Placido’s disc test-distorted circles(pg522)
  7. CCT-irregular corneal curvature
  8. Contact lens
  9. PTK with excimer laser
  10. Sx-Penetrating keratoplasty or DALK
29
Q

Purkunje images

A

4 in normal eye

2 in aphakic eye

30
Q

What is anisometropia?

How much diff causes diplopia?

A

Diff refractory power btw2 eyes
>2.5D nd >5% diff magnification causes diplopia.

*1D=2% magnification

Spectacles upto 4D
Contact lens for higher
IOL in aphakia, Refractive corneal Sx,PRL nd RLE(very high)

Early t/t to prevent amblyopia

31
Q

What is aniseikonia?
Etiology?
Types?

A

Images projected to the visual cortex from 2 retinae are in unequal in size nd or shape

*Upto 5% well tolerated

Etio-Optical,Retinal,Cortical

2 types-1.Symmetrical= Spherical,Cylindrical
2.Asymmetrical =Prismatic-inc in 1 direction
Pin cushion-inc in 2 directions(high plus correction)
Barrel- decr in 2 directions(high minus correction)
Oblique distortion

32
Q

What is presbyopia?

A

Condition of failing near vision d/t age related decrease in amplitude of Accomodation or Increase in punctuation proximum.

Near point 7@10 yrs
25@40 yrs
33@45yrs

33
Q

Causes of presbyopia?

A

Age related-1.Changes in lens- decrease elasticity or increase sclerosis
2.Decreased ciliary muscle power

Premature causes-1.Uncorrected Hmt

                                 2. Premature sclerosis
                                 3. Chronic simple glaucoma
34
Q

Presbyopic glasses guide

A

45 yrs=+1 to +1.25
50 yrs=+1.5
55 yrs=+2
60 yrs=+2. 5

35
Q

Disadvantages of spectacles in aphakia

A
  1. High magnification-diplopia
  2. Spherical aberration-Pin cushion effect
  3. Prismatic aberration-Roving ring scotoma/Jack in box phenomenon
36
Q

What is cycloplegia?

Causes?

A

Paralysis of Accomodation

  1. Drug ind-Atropine,HA
  2. Paralytic internal ophthalmoplegia
  3. Complete 3rd nerve paralysis
  4. Blurring of near vision
  5. Photophobia(glare)
  6. Decrease in near Point
37
Q

Spasm of Accomodation?

A

Excess Accomodation

  1. Drug ind-strong miotics
  2. spont

Relaxed by atropine

Ophtha (4 decks)

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