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Blwyddyn 1; Tymor 3 > 130; Eye Week > Flashcards

130; Eye Week Flashcards

1
Q

What assessments are involved in a 6(7) point eye examination?

A
  1. Visual acuity
  2. Eye movements
  3. Pupils
  4. Visual fields
  5. External inspection / anterior segment
  6. Fundoscopy
  7. (intraocular pressure- if equipment available)
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2
Q

List potential causes of ocular neuropathy.

A
  • Compression
  • Infection
  • Ischaemia
  • Inflammatory
  • Congenital
  • Hereditary
    *
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3
Q

What is Leber’s hereditary optic neuropathy?

A

Mitochondrially inherited degeneration of the retinal ganglion cells.

It causes sequential painless loss of vision in late teens - 20s

males > females

*Only transmitted through the mother; only the oocyte contributes mitochondrial DNA to the embryo (different to nuclear DNA)

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4
Q

Why does this mitochondrial defect affect the retina?

A

Mitochondrial disease affects tissues with high energy turnover; the retina is the most metabolically active tissue in the body

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5
Q

What are the main cell layers of the retina? (from the choroid inwards)

A
  • RPE
  • Photosensory cells (rods & cones)
  • Bipolar cells
  • Ganglion cells
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6
Q

List, in detail, the layers of the neurosensory retina.

A
  • RPE
  • Photoreceptors (rods & cones)
  • Outer limiting membrane; Inner horizontal branches of Muller cells
  • Outer nuclear layer; Cell bodies of Rods & Cones
  • Outer plexiform layer; synapse of R&C with Bipolar cells
  • Inner nuclear layer; Cell bodies of Bipolar cells
  • Inner plexiform layer; Synapse of Bipolar and Ganglion cells
  • Ganglion cell layer; Cell bodies of ganglion cells
  • Nerve fibre layer; axons to optic nerve
  • Inner limiting membrane; inner border of Muller cells
    • Basement mambrane
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7
Q

Describe the distribution of Rods and Cones at the retina.

A

Generally there are far greater Rods in the retina

*Fovea has v.high density of Cones*

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8
Q

What are the differences between Rods and Cones?

A

Rods

  • 3 types of photosensitive pigments
  • Colour vision
  • Req higher light intensity
  • Dense at fovea
  • Visual acuity
  • Highly metabolic

Cones

  • 1 photosensitive pigment; not distinguish colour
  • Active at lower light intensity
  • Peripheral vision
  • Night vision
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9
Q

What happens to the photoreceptor when stimulated by light?

A
  • At rest it is depolarised
  • When stimulated it becomes hyperpolarised
    • Reduction in glutamate release
  • Bipolar cells regulate the signal from photoreceptors and transmit to Ganglion cells
  • Ganglion cells transmit this to retinal nerve fibres –> optic nerve
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10
Q

Where does the neural processing of vision occur?

A

At the retina

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11
Q

What are the 3 different types of cone cells?

A

Defined by their specific opsins which have peaked sensitivity at particular wavelengths

  • Blue
    • Lower wavelength detection
    • 450 nm
  • Green
    • 550nm
  • Red
    • 600nm
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12
Q

What is the most common colour vision defect, and who is predominately affected?

A

Red-green colour blindness; 99%

Males > Females

It is an X-linked defect

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13
Q

What are the 2 sub-types of red-green colourblindness?

A

Protanopia- Red weakenss

Deuteranopia- Green weakness

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14
Q

What is the cause of Blue colourblindness?

A

Tritanopia; caused by chromosome 7 defect

Autosomal dominant disease; Males = Females

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15
Q

Name the different types of Photoreceptors.

A
  • Rods
  • Cones
  • Photosensitive retinal Ganglion cells
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16
Q

What photosensory pigment does the photosensory retinal ganglion cell contain?

A

Melanopsin

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17
Q

What is the role of photosensory RGCs?

A

Non-image-formatting cells

Provide info on ambient light intensity; control pupil size

Role in Circadian rhythms; Regulate melatonin production

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18
Q

What tract do photosensory RGCs project information?

A

Retinothalamic tract

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19
Q

Where is melatonin produced and what is its role?

A

Produced in the pineal gland

and skin, retina, GIT

A hormone thet regulates circadian rhythms

Alos an antioxidant that protects DNA

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20
Q

What is miosis?

A

Pupil constriction

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21
Q

Describe the Afferent route of pupillary reflex fibres.

A

Light hits retina…

  • Optic nerve
  • Optic chiasm
  • Optic tract
  • Fibresdiverge to pretectal nucleus
  • Bilateral projections to occulomotor n. nucleus
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22
Q

Describe the Efferent route of pupillary reflex fibres

A
  • Occulomotor nerve nuclei
  • Occulomotor nerve
  • Ciliary ganglion
  • Short ciliary nerves
  • Sphincter pupillae
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23
Q

What is the direct and consensual pupillary response?

A

Direct; Pupil constriction in eye that sensed the light

Consensual response; Pupil constriction in contralateral eye

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24
Q

What is the swinging light test?

A

Light moved from one eye to the other and pupil reaction and size noted.

Abnormality indicates relative afferent pupilary defect.

**Lesion anterior to chiasm**

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25
What is the pupillary near response?
aka **Accommodation** reflex It is a combination of _vergence_, _lense shape_ and _pupil size_
26
What is the Afferent route of the pupillary near response?
CN II route to the occipital lobe
27
What is the efferent route of the pupillary near response?
Occipital projections to _**frontal** eye field_ Bilateral projections to _main_ and _accessory **occulomotor** nuclei_ * Occulomotor nerve to extraocular muscles * Occularmotor --\> Short ciliary nerve to pupil
28
What are the signs and symptoms of dorsal midbrain syndrome.
* Light-near dissociation * No reaction to light; Pupil constriction to near response * Failure of upgaze * Nystagmus
29
What can cause Dorsal midbrain syndrome?
Pineal tumour
30
What is the Lateral Ganiculate Nucleus?
It is a part of the **thalamus** between the optic tract and optic radiation. Primary relay center for visual information.
31
What are the different parts of the optic radiation?
* Meyer's loop * Superior part
32
Which part of the visual field does Meyer's loop process?
Superior part
33
Which part of the visual field does the Superior part of the optic radiation process?
The inferior visual field
34
Where is orientation information processed?
Cortical neurones
35
List some factors that provide anti-microbial protection to the eye.
Tears * Lactoferrin * Complement * Lysozyme * IgA IgG * Leukocytes Conjunctiva * Lymph tissue
36
What is Mydriasis
Dilation of the pupil
37
What is hyphaema?
Blood in the anterior chamber of the eye
38
Disease to which areas of the visual system can cause sudden visual loss?
* Cornea * Anterior chamber * Lens * Vitreous humour * Retina * Optic nerve * Higher pathways
39
What is Uveitis?
Acute intraocular inflammation
40
What may cause people to see flashing lights?
Retinal detachment Migranes (flashing usually bilatereal here)
41
How can you test weather the visual pathways up to the optic chiasm are functional?
Pupillary reflex
42
What is phenylepherine
A **sympath**omimetic drug â1 adrenergic receptor agonist * Pupil Dilation (Mydriasis)
43
What are the side effects of Phenylepherine?
Photophobia Blurred vision Stinging Acute glaucoma Arrhythmias & hypertension \*Not as effective in DM, dark iris or elderly\*
44
Give some examples of Antimuscarinics
Atropine Cyclopentolate **Tropicamide**
45
How do antimuscarinics work?
Muscarinic Ach receptor antagonists * Cause Mydriasis= pupil dilation
46
What is Tropicamide used for in practice?
Mydriasis in eye exams
47
What is Cyclopentolate used for in practice?
**Uveitis**- relaxes the ciliary muscle
48
Wat are the side effects of antimuscarinics?
* Photophobia & Blurred vision * Stinging and raised IOP * Dry mouth * Confusion * Flushing
49
What are the symproms for acute angle-closure glaucoma?
* Blurred vision * Headache * Red, painful eye * Nausea & vomiting
50
Name a parasympathomimetic drug
Pilocarpine
51
How do Parasympathomimetics work?
Muscarinic Ach receptor agonists Cause Miosis, pupil constriction Open up drainage channels in trabecular meshwork **Treatment for Glaucoma**
52
What are the side effects of Pilocarpine?
Headache / browache Stinging on application Myopia (short sighted) Retinal detachment
53
Name a ß blocker used in ocular pharmacology
**Timolol**
54
What are the uses of Timolol
It is a ß blocker; prevents the production of aqueous humour (aqu. in the anterior compartment) Treat **Glaucoma**
55
Name carbonic anhydrase inhibitors used in ocular pharmacology
* Acetazolamide; oral/IV * Dorzolamide; topical Used to treat Glaucoma
56
Give one example of artificial tears
**Hypromellose**
57
Name a staining agent for the eye
**Fluorescin** Shows up damage to conjunctiva or cornea
58
Give an example of an anaesthetic agent for the eye
**Lidocaine**
59
Name an agent used to treat superficial eye infections
**Chloramphenicol** (antibiotic)
60
Here are examples of systemic drugs causing ocular side effects:
* Digoxin toxicity – disturbance in colour vision * Amiodarone – halos, especially affecting night-time driving, optic neuropathy * Anti-psychotics – blurred vision, corneal deposits * Ethambutol – optic neuritis causing loss of visual acuity and macular degeneration * Rifampicin – orange staining of tears * Tricyclic antidepressants – anticholinergic effects (blurred vision, disturbance of accommodation, increased IOP) * Opioids – miosis * Ipratropium – anticholinergic – care with nebulisation * Anti-malarials – various effects * Corticosteroids – cataracts in long-term use, increased IOP * Antihistamines – blurred vision, reduction in tears
61
What are the 3 stages involved in Phototransduction?
1. Light activates visual pigments (rhodopsin) 2. Activated molecules stimulate cGMPphosphodiesterase * This enzyme reduces [cGMP] 3. cGMP reduction closes cGMP-gated channels; hyperpolarising the cell
62
What os the visual pigment in Rod cells?
Rhodopsin ## Footnote **Opsin** is the protein protion, embedded in the disk membrane **Retinal** is the light-absorbing portion; a derivative of VitA
63
What is the non-activated and activated form of Rhodopsin?
Non-activated --\> 11-Cis Activated --\> all-Trans
64
What neurotransmitter is releasd by Rod cells?
**Glutamate** An inhibitory neurotransmitter; In dark Rods are depolarised, releasing glutamate to bipolar cells. Following hyperpolarisation (LIGHT) glycine release ceases and the bipolar cells no longer inhibited.
65

Blwyddyn 1; Tymor 3 (13 decks)

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