Soft contact lenses past, present and future

(D) 1990.
The correct answer is C. The first commercially available disposable lenses were introduced in 1987.

2What was the percentage market share in volume of silicone hydrogel lenses in the UK in 2003? (A) 5 per cent; (B) 1.1 per cent; (C) 8.4 per cent; (D) 0.8 per cent.
The correct answer is B. Silicone hydrogels represented just 1.1 per cent of volume and 8.4 per cent in terms of value.

3 What benefit may be ascribed to changing from quarterly to monthly replacement of high water hydrogel soft lenses? (A) Decreased front surface wetting; (B) Increased deposition; (C) Decreased performance; (D) Decreased deposition.
The correct answer is D. Reducing the amount of wear will obviously have the benefit of reducing deposition on the lens.

4In the UK in 2003, what percentage of new fits were with daily disposable lenses? (A) 30 per cent; (B) 5 per cent; (C) 34 per cent; (D) 13 per cent.
The correct answer is C. Daily disposables accounted for around one in three new fits in the UK in 2003. This is a very high proportion of the market compared with other countries.

5Which of the following cannot be claimed as an advantage of current frequent replacement/disposable soft contact lenses? (A) Comfort; (B) Convenience; (C) Minimal hypoxic effects; (D) Affordability.
The correct answer is C. Although reducing wear time will always have benefits in reducing potential hypoxic insult, conventional hydrogels will always present potential for reduced oxygen supply.

6 What is the minimum oxygen transmissibility based on the work of Holden and Mertz needed to avoid corneal oedema during open-eye daily wear when edge corrected values are used (in 10-9 Fatt units)? (A) 24; (B) 87; (C) 21.8; (D) 35.
The correct answer is C.

7 What value has more recently been quoted for the transmissibility needed to avoid corneal anoxia in open-eye conditions (in barrers/mm)? (A) 24; (B) 87; (C) 21.8; (D) 35.
The correct answer is D. Recently, a transmissibility of 125x109 barrers per millimetre has been reported as a requirement for avoiding stromal anoxia in closed-eye conditions with 35 established for open-eye conditions.

8Which of the following statements about corneal swelling with daily wear lenses is true? (A) No swelling has ever been detected; (B) Some swelling of the central cornea is detectable; (C) Some swelling of theperipheral cornea is detectable; (D) Swelling is greater with daily wear than extended wear.
The correct answer is C. Researchers from Poland reported a small but detectable level of peripheral corneal swelling with daily-wear lenses.

9 Which of the following possible complications is unlikely with silicone hydrogel lens wear? (A) Contact lens peripheral ulcers; (B) Corneal neovascularisation; (C) Contact lens acute red eye; (D) Infiltrative keratitis.
The correct answer is B. The high oxygen transmission properties of the material mean that neovascularisation is unlikely.

10 Which of the following complications may be a result of the high stiffness modulus of current silicone hydrogel lenses? (A) Contact lens peripheral ulcers; (B) Corneal neovascularisation; (C) Contact lens acute red eye; (D) Superior epithelial arcuate lesions.
The correct answer is D. SEALs appear to be a result of mechanical action.

11 Which of the following statements about mucin balls is correct?(A) They present a significant cause of infection; (B) They restrict lens movement; (C) They cause epithelial defects; (D) Apparent staining is due to pooling of fluorescein in the depressions left by the balls.
The correct answer is D. Mucin balls cause an indentation of the corneal surface into which fluorescein pools, sometimes then being mistaken as epithelial staining.

12 Which of the following is the most likely reason for current silicone hydrogel wearers to discontinue wear? (A) Excessive cost; (B) Handling difficulties; (C) Discomfort; (D) Poor or variable vision.
The correct answer is C. There is significant evidence that discomfort is the main factor leading to a patient discontinuing silicone hydrogel lens wear.