OPTOM 345B

Question 1

Cornea Structure

Answer 1

Fat-Water-Fat

Question 2

Forms that drugs exist in

Answer 2

Non-ionised, Fat and water soluble, Water insoluble and ionised, and fat insoluble

Question 3

How do drugs enter through the cornea

Answer 3

Fat soluble form penetrates epithelium, penetrates stroma in ionised form, fatsoluble form goes through endothelium and then re-equilibriates as both forms. Then ionised form diffuses through AH to the tissues

Question 4

When to use cycloplegics

Answer 4

Strabismic px, High plus, accommodative esotropia, Low AoA, Impaired BV and children under 3

Question 5

What to check for before cycloplegia

Answer 5

Px sensitivity to drugs, general health and family hx of glaucoma.

Also do full refraction before cycloplega

Question 6

Why check glaucoma history with cycloplegics

Answer 6

Cycloplegics are mydriatics so should check if anterior chamber angle is open or not

Question 7

How to cycloplegics work

Answer 7

Competitive antagonists of PSNS so it blocks mach in ciliary body and sphincter pupillae smooth muscle

Question 8

What are the main muscarinic receptor types in human ciliary muscles

Answer 8

Mostly M3 and M2

Question 9

Name all the cycloplegic drugs

Answer 9

Cyclopentolate + Tropicamide + Atropine sulphate + Hyoscine + Homatropine

Question 10

Cyclopentolate

Answer 10

Fast onset in minutes w 24H recovery for cycloplegia. Mydriatic effect last up to several days

1% on children and 0.5% if over 16

Question 11

What affects onset and recovery rates for cyclopentolate

Answer 11

Iris pigment density

Question 12

What works better with darker irises

Answer 12

Combination of 1% cyclopentolate and tropicamide

Question 13

Toxic reactions to cyclopentolate

Answer 13

Stings but reduced w anaesthetic. Lacrimaution and mucous discharge seen. Toxic reactions depend on dose and CNS side effects

Early signs of toxicity is ataxia, incoherent speech and drowsiness

Question 14

Tropicamide

Answer 14

Onset within minutes with cyclo recovery in 3H and mydriasis recovery in 6-8H.

No adverse reactions

Question 15

When to use tropicamide

Answer 15

Children over 12 years of age

Question 16

Atropine sulphate

Answer 16

Use 3 days prior in infants. Recovery ( 2 weeks ) for cyclo and mydriasis.

Question 17

When else to use atropine sulphate

Answer 17

Adult has anterior chamber inflammation, amblyopia and for myopia control

Question 18

Hyoscine

Answer 18

Potent and long lasting cycloplegia w similar side effects to atropine.

Derived from Belladonna or Jimsonweed

Question 19

What is Hyoscine also used for

Answer 19

Motion sickness, prevents posterior synechiae in inflammatory disease.

But produces retrograde amnesia

Question 20

Homatropine

Answer 20

10% potency of atropine. It is less of a cycloplegic than cyclopentolate but has prolonged mydriatic effect

Has toxic reactions like atropine

Question 21

What is Homatropine also used for

Answer 21

Inflammatory disease to prevent posterior synechiae and relieve painful spasms of ciliary muscle

Question 22

Precautions with cycloplegics

Answer 22

Use minimum dose and occlude the punch. Caution with blonde chilren and prepare for ADRs. Dont use if past allergies and use in cool room temperatures.

Question 23

Cycloplegic refraction procedure

Answer 23

Measure AoA 20-30 mins post drug check drug effect. Observe reflex with ret and use distance fixation with tropicamide.

Can use autorefraction with cycloplegia. Pupil size is not an indication of level of cycloplegia

Question 24

Refracting Children Methods

Answer 24

1. Spray administration of cycloplegia ( 0.5% cyclypentolate and tropicamide w 2.5% phenylephrine )
2. Photorefraction ( Need cycloplegia for accuracy in high Rx error )
3. Mohindra’s near retinoscopy technique which is useful but inaccurate on young high hyperopes and squinters