Overnight contact lens wear remains a major risk factor for developing microbial keratitis

This prospective, 12-month, population-based study was undertaken to establish the absolute risk of contact lens-related microbial keratitis. Overnight contact lens wear remains the major risk factor for developing MK irrespective of material type. Other risk factors included poor storage case hygiene, smoking, Internet purchase of CLs and socioeconomic class.

The authors of this Australian study write that contact lens-related corneal infection remains rare, affecting 4.2 per 10 000 wearers in Australia per year, which is consistent with rates previously reported in the United States, Holland, Hong Kong and Scotland.

Previously studies report that permanent vision loss after corneal infection occurred in 11 to 13 percent of cases. This study also reports an annualized incidence in 0.6 per 10 000 wearers (13.9 percent of cases) who experienced a reduction in best-corrected visual acuity of ≥2 lines. Using a final corrected acuity of 6/12, the rate of vision loss was 9.9 percent, or 0.4 per 10 000 wearers overall.

While the highest risk of visual loss occurred with overnight CL use, there was no difference in the annual rate of vision loss in soft (4.0 per 10 000) and silicone hydrogel (2.8 per 10 000) use. These estimates are consistent with a recent report of vision loss in overnight silicone hydrogel CL use of 3.6 per 10 000 wearers per year.