20 - Ocular Toxicity Flashcards Preview

Year 4 - Toxicology > 20 - Ocular Toxicity > Flashcards

Flashcards in 20 - Ocular Toxicity Deck (37)
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1
Q

What are the 2 separate vascular systems of the eye?

A
  • Uveal blood vessels

- Retinal vessels

2
Q

Purpose of cornea

A
  • Transparent protective membrane (must remain transparent, allows light rays to reach the retina)
  • Avascular (corneal epithelium, stroma, and endothelium)
3
Q

Purpose of lens

A
  • Avascular and transparent

- Focus, accommodation

4
Q

What effect can chlorpromazine have on the eye?

A
  • Pigmentation ranging from white to yellow to tan (5 stages)
    • Begins on anterior surface of the lens
    • Cornea is involved when lenticular pigmentation reaches grade 3
5
Q

What determines the effect of chlorpromazine on the eye?

A
  • Dependent on cumulative dose
    • Unlikely to show if total dose < 500g
    • 90% of px w/ total cumulative dose > 2500g show ocular changes
  • Px on high doses or on long-term low-dose regimens w/ chlorpromazine should have eyes checked annually
6
Q

What effect can corticosteroids have on the eye?

A
  • Systemic, topical, nasal, inhaled steroids cause posterior subcapsular cataracts (PSC)
  • MOA –> altered lens epithelium electrolyte balance and binding to protein of lens
  • Generally reversible
7
Q

What determines the effect of corticosteroids on the eye?

A
  • Unlikely in px who receive < 10 mg prednisone (or treated for < 1 year)
  • Px on long-term oral steroid therapy should have eyes examined q6months
8
Q

What effect can quetiapine have on the eye?

A
  • Manufacturer recommends eye exam at baseline and q6months throughout therapy
  • Cataract development observed in dog model
  • Some px have developed lens changes but no cataracts
9
Q

Aqueous humour is equivalent to ____

A

CSF

10
Q

Where is the aqueous humour found?

A

Flows between posterior surface of iris and anterior lens surface

11
Q

Normal intraocular pressure?

A

10-22 mmHg

12
Q

What can intraocular pressure > 28-30 mmHg cause?

A

Ischemic damage of the optic nerve causing glaucoma

13
Q

Sx of open-angle glaucoma

A
  • Absence of pain
  • Slow loss of peripheral visual field
  • Often unnoticed by pt
14
Q

Causes of closed-angle glaucoma

A
  • Happens to individuals that are genetically susceptible
  • Narrow anterior chamber angle
  • Caused by anything that dilates the pupil
15
Q

Which drugs affect intraocular pressure?

A
  • Corticosteroids
  • Phenothiazines (chlorpromazine)
  • TCAs
16
Q

Affect of corticosteroids on IOP?

A
  • Increased resistance to aqueous humour outflow
  • Topical ophthalmic agents more likely than oral agents to increase IOP
  • Prolonged continuous use (1600 mg beclomethasone or budesonide/day for 3 months or longer)
17
Q

Which drugs increase tear production?

A
  • Cholinergics (pilocarpine)

- Adrenergic agonist (ephedrine)

18
Q

Which drugs are excreted in tears?

A

Oral erythromycin and rifampin (orange coloured tears)

19
Q

What is the uvea?

A

Iris, ciliary body, and choroid

20
Q

Sx of anterior uveitis

A
  • Eye pain
  • Conjunctival redness
  • Photophobia and blurred vision
  • Pupil small and responds sluggishly to light
21
Q

Which drugs are associated w/ anterior uveitis?

A
  • Rifabutin

- Bisphosphonates

22
Q

Chloroquine and hydroxychloroquine effect on retina

A
  • Accumulation in the choroid, RPE (retina pigment epithelium), ciliary body and iris
  • Irreversible retinopathy
  • Doses < 400 mg/day of hydroxychloroquine appear safe even after prolonged therapy
23
Q

Digoxin and digitoxin effect on retina

A
  • Visual sx -> dyschromatopsia, flickering or flashes of light, coloured spots surrounded by coronas, snowy vision, hazy or blurred vision, glare sensitivity
  • Vision disturbances can also occur at therapeutic doses of digoxin
  • Inhibition of Na+K+ATPase (cone receptor function)
  • Reversible w/in few weeks after dose reduction or discontinuation
24
Q

Which drugs affect the retina?

A
  • Chloroquine and hydroxychloroquine
  • Digoxin
  • Indomethacin
  • Tamoxifen
  • Retinoids
  • Quinine
25
Q

Indomethacin effect on retina

A
  • Chronic administration of 50-200 mg/day for 1-2 years produces corneal opacities, paramacular depigmentation, decreased visual acuity, altered visual fields, blue-yellow colour deficits, and increased threshold for dark adaptation
  • MOA of retinotoxicity unknown
  • Colour disturbances return to normal after d/c
26
Q

Tamoxifen effect on retina

A
  • Chronic high-dose therapy (180-240 mg/day for 3 years) = axonal degeneration in the macular and perimacular areas
  • Permanent decrease in visual acuity and abnormal visual fields
  • Crystallizes in the retina
27
Q

Retinoids effect on retina

A
  • Poor night vision
  • Glare sensitivity
  • Problems w/ colour detection
28
Q

Quinine effect on retina

A
  • Neurotoxic injury to retinal ganglion cells (permanent loss) and optic nerve
  • Retinal vasoconstriction
  • Blurred vision, central and peripheral scotomata, and complete blindness
  • Sudden visual loss can occur as late as 14 h after OD
29
Q

Purpose of optic nerve

A

Carries visual info from retina to several distinct areas of the CNS

30
Q

Ethambutol effect on optic nerve

A
  • Decreased contrast sensitivity and colour vision
  • Dose-related alterations = blue-yellow and green-red dyschromatopsia
  • Optical neuropathy (central scotoma, visual field loss, decreased visual acuity)
  • 10% of px receiving 25-50 mg/kg/day show loss of vision between 1-7 months; reversible upon discontinuation
31
Q

What is a normal pupil size?

A
  • 3-4 mm

- Equal to each other

32
Q

What causes pupil constriction (miosis)?

A
  • Cholinergic agents
  • Opiates
  • Phenothiazines
  • Sedative hypnotics
33
Q

What causes pupil dilation (mydriasis)?

A
  • Anticholinergics
  • Anti-depressants
  • Sympathomimetics
34
Q

Which drug causes jerk nystagmus?

A

Phenytoin

35
Q

What is the most common nystagmus?

A

Jerk nystagmus

36
Q

Which drugs can cause vertical nystagmus?

A
  • Ketamine
  • Dextromethorphan
  • Phencyclidine
37
Q

What are some ocular complications of drug abuse?

A
  • Quinine amblyopia (IV use of quinine-containing heroin)
  • Talc retinopathy
  • Infectious complications -> fungal & bacterial endophthalmitis
  • HIV-related retinitis
  • Cocaine -> diffuse vasospasm = retinal ischemia and blindness
  • “Crack eye” (corneal defects)