ophthal refractive error and cataract

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  • 1. REFRECTIVE ERROR AND CATARACT
    Ng Boon Keat, MohdHanafi, AnandKumar

2. PART 1: REFRECTIVE ERROR
3. EMMETROPIA
The state of refraction of the eye in which parallel rays, when the eye is at rest, are focused exactly on the retina.
Stedmans Medical Dictionary, 2005
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4. EMMETROPIA
Eye with no refractive error
Parellel light = light from infinity (light from far far away)
Images are focused with relaxed lens and cornea
Without the need for accommodation
ABC of Eyes, 2004
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5. MYOPIA
That optic condition in which parallel light rays are brought by the ocular media to focus in front of the retina.
Synonym:
Shortsightedness
nearsightedness.
Stedmans Medical Dictionary, 2005
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6. MYOPIA
Pathophysiology
globe too long relative to refractive mechanisms, or refractive mechanisms too strong
light rays from distant object focus in front of retina blurring of distant vision
Toronto notes: Ophthalmology, 2006
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7. MYOPIA
Clinical features:
usually presents in 1st or 2nd decade, stabilizes in 2nd and 3rd decade; rarely begins after 25 years except in diabetes or cataracts
blurring of distance vision; near vision usually unaffected
Complications:
retinal tear/detachment, macular hole, open angle glaucoma.
Toronto notes: Ophthalmology, 2006
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8. CORRECTIONS

  • ABC of Eyes, 2004

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9. HYPERMETROPIA
An ocular condition in which only convergent rays can be brought to focus on the retina.
Synonym:
Hyperopia
Farsightedness
Stedmans Medical Dictionary, 2005
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10. HYPERMETROPIA
Pathophysiology:
globe too short relative to refractive mechanisms, or refractive mechanisms too weak
light rays from distant object focus behind retina blurring of near +/-distant vision
Toronto notes: Ophthalmology, 2006
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11. HYPERMETROPIA
Clinical features:
youth: usually do not require glasses (still have sufficient accommodative ability to focus image on retina)
30s-40s: blurring of near vision due to decreased accommodation, may need reading glasses
>50s: blurring of distance vision due to severely decreased accommodation
Complications:
angle-closure glaucoma, particularly later in life as lens enlarges
Toronto notes: Ophthalmology, 2006
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12. CORRECTIONS:

  • ABC of Eyes, 2004

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13. PRESBYOPIA
The physiologic loss of accommodation in the eyes in advancing age.
Stedmans Medical Dictionary, 2005
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14. PRESBYOPIA
Pathophysiology
hardening/reduced deformability of the lens results in decreased accommodative ability
near images cannot be focused onto retina (focus is behind retina as in hyperopia)
Normal aging process (especially over 40 years)
Toronto notes: Ophthalmology, 2006
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15. PRESBYOPIA
Clinical Features:
if initially emmetropic, person begins to hold reading material further away, but distance vision remains unaffected
if initially myopic, person begins removing distance glasses to read
if initially hyperopic, symptoms of presbyopia occur earlier
Corrections:
Usually as same as treatment of hypermetropia
Toronto notes: Ophthalmology, 2006
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16. APHAKIA
Absence of the lens of the eye.
Stedmans Medical Dictionary, 2005
A state of having no lens (eg removed because of cataract surgery)
Oxford Handbook of Clinical Specialties, 2009
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17. APHAKIA
Clinical features:
Removal of lens will result hypermetropic refractory error
Corrections:
Glasses
Contact lens
Secondary intraocular lens implant
ABC of Eyes, 2004
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18. INTRAOCULAR LENS IMPLANTS

  • ABC of Eyes, 2004

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19. CATARACT GLASSES

  • ABC of Eyes, 2004

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20. ACCOMMODATION

  • ABC of Eyes, 2004

Component of accommodation:
Pupil Constriction
Ciliary muscle contraction and globular changes of the lens
Convergence of the eyes
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21. PART 2: CATARACT

  • Anatomical site

22. Cortical 23. Nuclear 24. Subcapsular 25. Anterior Subcapsular 26. Posterior Subcapsular

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