20 - Ocular Toxicity Flashcards
What are the 2 separate vascular systems of the eye?
- Uveal blood vessels
- Retinal vessels
Purpose of cornea
- Transparent protective membrane (must remain transparent, allows light rays to reach the retina)
- Avascular (corneal epithelium, stroma, and endothelium)
Purpose of lens
- Avascular and transparent
- Focus, accommodation
What effect can chlorpromazine have on the eye?
- 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
What determines the effect of chlorpromazine on the eye?
- 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
What effect can corticosteroids have on the eye?
- Systemic, topical, nasal, inhaled steroids cause posterior subcapsular cataracts (PSC)
- MOA –> altered lens epithelium electrolyte balance and binding to protein of lens
- Generally reversible
What determines the effect of corticosteroids on the eye?
- 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
What effect can quetiapine have on the eye?
- 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
Aqueous humour is equivalent to ____
CSF
Where is the aqueous humour found?
Flows between posterior surface of iris and anterior lens surface
Normal intraocular pressure?
10-22 mmHg
What can intraocular pressure > 28-30 mmHg cause?
Ischemic damage of the optic nerve causing glaucoma
Sx of open-angle glaucoma
- Absence of pain
- Slow loss of peripheral visual field
- Often unnoticed by pt
Causes of closed-angle glaucoma
- Happens to individuals that are genetically susceptible
- Narrow anterior chamber angle
- Caused by anything that dilates the pupil
Which drugs affect intraocular pressure?
- Corticosteroids
- Phenothiazines (chlorpromazine)
- TCAs
Affect of corticosteroids on IOP?
- 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)
Which drugs increase tear production?
- Cholinergics (pilocarpine)
- Adrenergic agonist (ephedrine)
Which drugs are excreted in tears?
Oral erythromycin and rifampin (orange coloured tears)
What is the uvea?
Iris, ciliary body, and choroid
Sx of anterior uveitis
- Eye pain
- Conjunctival redness
- Photophobia and blurred vision
- Pupil small and responds sluggishly to light
Which drugs are associated w/ anterior uveitis?
- Rifabutin
- Bisphosphonates
Chloroquine and hydroxychloroquine effect on retina
- 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
Digoxin and digitoxin effect on retina
- 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
Which drugs affect the retina?
- Chloroquine and hydroxychloroquine
- Digoxin
- Indomethacin
- Tamoxifen
- Retinoids
- Quinine
