Manuscript Review

Practitioner guidelines for continuous wear with high Dk silicone hydrogel contact lens

Sweeney DF, Keay L, Carnt N, Holden BA Clin Exp Optom. 2002, 85:161-167

Clinical studies have shown that high Dk silicone hydrogel lenses have eliminated physiological changes due to hypoxia,^1-10. The introduction of high Dk silicone hydrogel contact lenses into clinical practice has renewed the interest in continuous wear and presented practitioners with a new dimension of contact lens practice. Since these materials are unique and the concept of fitting lenses which may be worn for up to 30 nights continuously is novel, practitioners need to fit the lenses and manage patients in a manner which is different to the usual contact lens fitting routine. To assist practitioners in this transition, Sweeney and colleagues¹¹ have published "Practitioner guidelines for continuous wear with high Dk silicone hydrogel contact lenses" and this is a review of that paper.

The paper provides guidelines for practitioners to successfully manage continuous wear with high Dk silicone hydrogen contact lenses which includes patient selection, fitting assessment, after-care and patient education.


Patient Selection

Correct patient selection is crucial to achieve success with extended wear. Detailed medical and ocular history must be taken prior to lens fitting to rule out potential problematic patients such as those who have systemic disease or are using systemic medications which potentially compromise immunity and slow the healing response, and those who have a history of infiltrative reactions with contact lens wear. Although the high Dk hydrogel lenses cause less reported symptoms of dryness and discomfort than low Dk lens when worn on an extended wear basis, patients who have a history of discomfort and dryness could still be problematic. A routine biomicroscopic assessment of the whole anterior eye and tear layer is also essential. Any significant degree of corneal staining or infiltration must be resolved before lens wear commences. Patients who have poor hygiene and non-compliance with the wearing schedule and maintenance procedures are at increased risk of microbial contamination. Thus, it is necessary to continuously educate patients on the importance of lens hygiene so that they will correctly follow the instructions on after-care. The documentation kit recommended by Brennan and colleagues¹², which includes an information brochure, practitioner-patient agreement, instruction sheet, question and answer sheet, informed consent and emergency documentation, is useful to outline what the patient should expect from continuous wear with high Dk lenses.

As high Dk hydrogel lenses currently are only available in the spherical form, authors suggest that patients with astigmatism of one diopter or more may not be suitable candidates for these lenses.


Lens fitting and wear schedule

Fluting" of on ill-fitting Silicone Hydrogel Lens -Enlarge-

An ideal fit with silicone hydrogel lenses should achieve maximum movement and also provide optimum comfort. Trial lens fitting should always be undertaken before the commencement of continuous wear. Lens fit assessment includes evaluation of centration, corneal coverage and movement, and should be performed after 10-20 minutes of insertion. Lens fluting, a buckling of the lens edge, is the primary reason of ill-fitting silicone hydrogel lenses and will cause discomfort.

With regard to wear schedule, the authors recommended that starting with a daily wear adaptation period followed by a one-week extended wear is necessary for new lens-wearers. That is to allow the patient to become accustomed to lens wear and the practitioner to assess the response of the eye to the lens. Flexibility in wearing schedule should be encouraged. Patients can remove and clean their lenses as often as is thought necessary, but the authors have stressed that the lens must be rinsed and cleaned or disinfected prior to every reinsertion or be replaced with a new lens.


After care

Rinsing the eye with unit dose saline.

The guidelines suggested that the initial visit for continuous wear after-care should be scheduled after the first overnight wear. Subsequently, the patients should be seen after first week, first month, at three months and every three months thereafter. At each after care visit, record the history of lens wear health and symptoms, visual acuity, subjective ratings (i.e. comfort and vision), a thorough biomicroscopic examination of the anterior eye, corneal and lids (including palpebral conjunctiva), and the fit and appearance of lens surface should be conducted. It is important to evaluate the anterior eye carefully to detect any possible adverse events. It has been shown to be beneficial for patients to rinse their eyes each morning and night using single dose saline. Generally, there is no treatment needed for lipid deposition and mucin balls, which are observed more often with high Dk hydrogel lenses, unless they affect patient's comfort and vision.


Patient education

It is necessary to reiterate the importance of patient compliance at each visit. Patients should be advised to check every morning and night to ensure the well-being of their eyes. If there are any concerns, they should immediately remove their lenses and contact a practitioner. The instruction on lens care should be followed in the event of scheduled and unscheduled removal. Patients should be also advised never to sleep with uncomfortable lenses or if they feel physically unwell. Finally, patients should be advised that lens care solution is needed and a pair of up-to-date glasses should always be available as adverse responses can occur at any time.

Sweeney et al's guidelines¹¹ provide practitioners with useful information on how to conduct successful practice of continuous wear with silicone hydrogel lenses.

References

1. Holden BA. Extended wear: Past, present and future. Contact Lens Spectrum 2002;17(1):32-37

2. Fonn D, du Toit R et al. Sympathetic swelling response of the control eye to soft lenses in the other eye. Invest Ophthalmol Vis Sci. 1999; 40(3):3116-21

3. Sweeney D, Keay L et al. Clinical performance of silicone hydrogel lenses. In: Sweeney DF, ed. Silicone hydrogels: The rebirth of continuous wear contact lenses. Oxford: Butterworth-Heinemann; 2000:90-149

4. Dumbleton K, Chalmers RL et al. Vascular response to extended wear of hydrogel lenses with high and low oxygen permeability (2001) Optom Vis Sci 2001;78(3):147-51

5. Nilsson SEG. Seven-day extended wear and 30-day continuous wear of high oxygen transmissibility soft silicone hydrogel contact lenses: a randomized 1-year study of 504 patients. CLAO. 2001; 27(3):125-36

6. Levy B, Comstock T et al. Randomized controlled clinical trial of silicone hydrogel contact lens for 30 days of continuous wear. Invest Ophthalmol Vis Sci. 2000;41(4):s74

7. Covey M, Sweeney D et al. Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible OVS 2001;78(2):95-9

8. Keay L, Sweeney D et al. Microcyst response to high Dk/t silicone hydrogel contact lenses. Optom Vis Sci. 2000;77(11):582-5

9. Papas E, Vajdic C et al. High oxygen-tansimissibility soft contact lenses do not induce limbal hyperaemia. Current Eye Research 1997; 16(9):942-8;

10. McNally J, McKenney C. A clinical look at a silicone hydrogel extended wear lens. Contact Lens Spectrum 2002;17(1):38-41

11. Sweeney D, Keay L et al. Practitioner guidelines for continuous wear with high Dk silicone hydrogel contact lenses. Clin Exp Optom 2002 85(3):161-7

12. Brennan NA, Coles M-L C. Where do silicone hydrogels fit into everyday practice? In: Sweeney DF, ed. Silicone hydrogels: The rebirth of continuous wear contact lenses. Oxford: Butterworth-Heinemann; 2000:235-70