dry eyes

structure of eye (4)

1. eyelid

• 2 thin moveable folds infront of eye

• protect eye from injury by closing

• spread tear over ocular surface

2. lacrimal apparatus

• lacrimal gland & excretory ducts: secrete & convey tears to eye surface

• lacrimal duct, sac & nasolacrimal duct: convey fluid into nose cavity

3. conjunctiva

• transparent mucous mem lining inner surface of eyelids & outer surface of eye

• secretes oil & mucus to lubricate & moisten eye

4. extrinsic muscle of eye

tear layer

• complex multilayer film

• 3 layers

• 1-2uL/min of tears prod

• tear vol is 7-10uL

• reflex tearing —> dur ocular irritation, inc tear prod by more than 300% of non stimulated rate

functions

1. keep ocular surface lubricated

2. maintain health of cornea by supplying nutrients & flush away waste prods

tear layers (3)

1. outer lipid layer

• secreted by meibomian glands

• red evaporation

• maintain eye optical properties

2. middle aq layer

• secreted my lacrimal gland

• responsible for wetting purpose of tear film

3. inner mucous layer

• secreted by conjunctiva

• all aq & lipid layer to maintain constant adhesion across cornea & conjunctiva

• spread tears evenly on eye surface

causes of dry eyes (6)

1. aging

2. lid. corneal defects

3. collagen diseases —> rheumatoid arthritis

4. systemic meds —> antihistamines

5. environmental conditions —> dry/ dusty/ heating & air conditioning

6. inadequate tear prod

symptoms of dry eyes (4)

1. mildly red eyes

2. sandy, gritty feeling

3. foreign body sensation

4. blur vision

complication of dry eyes (1)

1. fail to properly diagnose & treat = severe damage to eye tissue, esp corneal surface

treatment goals (3)

1. alleviate and control dryness of ocular surface

2. relieve symptoms of irritation

3. prevent possible tissue and corneal damage

non pharma therapy (5)

1. avoid environments which inc evaporation of tear fluid

2. use humidifiers

3. reposition workstations away from heating/ air conditioning cents

4. avoid prolonged viewing of computer screens

5. avoid windy outdoor environments without eye protection

pharma therapy

• use ocular lubricants

  • less viscous = mild case

  • more viscous = more severe case

  • ointment preparations = severe case & use @ bedtime

• types of ocular lubricants

1. artificial tear sol (single/ multi dose)

2. nonmedicated ophthalmic ointments

artificial tear sol components

1. demulcents

• form protective layer over mucous mem to red inflammation and irritation

• hydroxymethylcellulose, carboxymethylcellulose

  • hydrophilic polymers which coat and protect the eye by crosslinking with the ocular surface to inc tear clearance times

• polyvinyl alcohol

2. emollients

• oily fat based agents that protect and soften tissues by sealing in moisture

• mineral oil, lanolin, paraffin, petrolatum

3. preservatives

• inorganic electrolytes

• maintain tonicity and pH

4. others

• ingredients to inc viscosity = inc retention time

• hp guar

adverse effects

• preservatives can be toxic to ocular tissues

• can have hypersensitivity to preservatives

—> sensitivity to preservatives, severe dry eyes, use drops 4-6 times a day

—> avoid using eyedrops with benzalkonium chloride as it increases the eye surface irritation & disease,, and it also cannot be used w soft lenses

no preservative option —> carboxymethylcellulose 0.5/1%, polyvinyl

moa (5)

1. form a hydrophilic layer over the corneal surface to mimic the natural conjunctiva mucin

2. stabilize the tear film to retard evaporation and inc retention

3. inc viscosity

4. promote wetting of ocular surface

5. create a ocular shield for epithelial repair

nonmedicated ophthalmic ointment types (3)

1. white petrolatum —> lubrication and act as base

2. mineral oil —> help melt at body temp

3. lanolin —> incorporate water sol meds, prevent evaporation

moa (7)

1. inc retention time

2. inc integrity of eye film

3. form hydrophilic layer over corneal surface to mimic conjunctiva mucin

4. stabilize tear prod to retard evaporation and inc retention

5. promote wetting of ocular surface

6. inc viscosity

7. create ocular shield for epithelial repair

adverse effects (3)

• blurred vision

• hypersensitivity to preservatives

• preservatives can be toxic to ocular tissues

administration guidelines (3)

1. multidrop therapy

• wait 5mins bfr instilling next drop

• eye can only hold 7-10uL of liquid each time

• if dont wait, 2nd drop will j overflow out of eye

2. using suspension

• use suspension last

• suspension have solid particles

• if use an eyedrop after suspension, it will dilute the suspension

3. both drop and ointment therapy indicated

• wait 10mins aft eyedrop to do ointment therapy

• ointment may interact w eyedrop and affect absorbency of meds