Week 3 Questions

Question 1

applanation tonometry (the most widely accepted method used to measure IOP and is considered the gold standard tonometer)

Answer 1

fluorescein

Question 2

RGP contact lens fitting (corrects astigmatism)

Answer 2

fluorescein

Question 3

diagnosis/monitoring of ocular surface damage in dry eye

Answer 3

double supravital staining (fluorescein + rose bengal/lissamine green)

Question 4

nasolacrimal duct patency

Answer 4

fluorescein

Question 5

tear clearance

Answer 5

fluorescein

Question 6

assessment of tear film stability, TBUT

Answer 6

fluorescein

Question 7

extent of corneal epithelial damage

Answer 7

fluorescein

Question 8

extent of conjunctival and lid margin damage

Answer 8

lissamine green

Question 9

differential diagnosis of epithelial defect vs. herpes simplex dendrite vs. psudodendrite

Answer 9

rose bengal/fluorescein (use both)
- rose bengal and lissamine green can inhibit PCR detection of HSV DNA
- Scrapings for PCR diagnostic testing should be taken before instillation of rose bengal or lissamine green

Question 10

seidel test (used to identify full-thickness defects in the cornea or sclera by revealing leakage of aqueous humor)

Answer 10

fluorescein

Question 11

your patient is scared about cataract surgery, what to tell them?

Answer 11

Assure patient that this is a very common procedure that is performed as cataract is prevalent in the population. The patient would likely receive topical anaesthetic and sedation (sub-tenon) during the procedure, which is the safest and most efficient method. They would be awake and able to follow instructions but will remain calm.

Question 12

which anaesthetic is the best for pregnancy? (should be avoided regardless)

Answer 12

lignocaine

Question 13

anaesthetics: px is contact lens wearer.
what to tell them before and after using topical anaesthetic to perform contact tonometry?

Answer 13

Recall side effects of topical anaesthetics, including reduced corneal epithelial defect healing, loss of corneal epithelium, reduced blinking, and chronic non-healing epithelial defect. Contact lenses should be removed prior to application of local anaesthetic anyway as it may absorb the anaesthetic. The patient should also be advised not to wear contact lenses until the next day due to increased loss of corneal epithelial cells. Want to reduce irritation to the ocular surface. Contact lenses must be removed and only re-inserted after anaesthetic effects ceased and no epithelial defects remain. (2-6hrs later)

Question 14

anaesthetics: px has recurrent corneal epithelial erosion. would like to take anaesthetic eye drops at home. what to tell them?

Answer 14

Side effects of topical anaesthetic use include loss of corneal epithelium, inhibiting the healing of epithelial defects, tear film instability, decreased blink rate and chronic non-healing epithelial defect. Corneal erosion is related to affected ocular surface epithelium to start with, thus the use of topical anaesthetics will likely impede recovery and exacerbate the condition. Better advice for patient is to reduce eye rubbing, and the use of oral systemic pain relief and lubricants.

Question 15

good practices to prevent infection?

Answer 15

1. disinfect equipment (chin rest, tonometer, gonio lenses, trial frame, PD ruler) that will touch eye/skin the best you can without destroying them (70% alcohol swabs)
2. clean work surfaces daily (e.g. 1% sodium hypochlorite)
3. autoclave metal instruments that touch the eye (e.g. forceps, FB spud, scleral indenter/depressor)
4. autoclave contact trial lenses, or NaOH soak, preferably use disposable CLs, NCT tonometer methods, single use tonometer covers.
5. wash hands often, cover all cuts.
6. wear gloves when dealing with high-risk patients
7. touch patients’ skin the least possible
8. don’t work if unwell (e.g. COVID symptoms)

Question 16

what does the onset and duration information mean for clinical practice? (anaesthetic)
1. wait time between instilling anaesthetic eye drops and doing a test?
2. time available to conduct tests that contact the eye?

Answer 16

Anaesthetic eye drops, especially esters (oxybuprocaine, proxymetacaine, amethocaine), have very fast onset of action (20 seconds) and lasts for 20 minutes maximum. Lignocaine, an amide, slightly slower (but still fast) onset of action (2-5 minutes) and lasts 20-30 minutes. When doing tests with local anaesthetics, it is imperative to have everything prepared prior to instilling eyedrops as the onset is rapid. Optometrists should also limit local anaesthetics to 2 drops to reduce ocular surface damage.

Question 17

which is the preferred topical anaesthetic by optometrists?

Answer 17

oxybuprocaine

Question 18

why would one use lignocaine? (instead of oxybuprocaine/proxymetacaine)

Answer 18

consider allergic reactions to esters, as amide rarely have cross allergic reactions. it is also preferred for contact tonometry and comes with fluorescein. least damage for epithelial damage.

Question 19

which anaesthetics are the safest with least local/systemic toxic effects?

Answer 19

oxybuprocaine and proxymetacaine

Question 20

which anaesthetic is the least comfortable?

Answer 20

amethocaine. greatest slothing of epithelial cells.

Question 21

which anaesthetic is the most comfortable?

Answer 21

proxymetacaine. but has BAK preservative.

Question 22

anaesthetics: what will you do, tell patients, and see patients for review?

Answer 22

Although rare, there are side effects that come with local anaesthetics. Consider pre-testing and post-testing procedures. Ask patient about previous experience with anaesthetics (e.g. Allergies, have they had the anaesthetics before?) and inform them of stinging. Before instilling drops, observe ocular surface and also after. If much slothing of cells, prescribe lubricants. Even minor epithelial defects will affect vision greatly, so inform patients of this, although not common. This will improve by the next day (cell turnover 24 hours).
If this occurs, review the patient the next day to ensure recovery is underway, once again assuring the patient this is very rare. Slothing is greater in older patients and will continue to lose cells for some time.