Soft and GP contact lenses are typically considered safe. In fact, the overall incidence of microbial keratitis in contact lens wearers is about 20 cases per 10,000 patient years or less depending upon the contact lens modality being worn (Stapleton et al, 2013), and the majority of these contact lens-related events are associated with poor contact lens care and compliance (Stapleton et al, 2013; Wagner et al, 2014). While microbial keratitis can stem from a number of different microbes such as Acanthamoeba species and fungus, bacteria are by far the most common offenders. This is why clinicians often empirically treat cases of microbial keratitis as if they were bacterial in nature (Ehlers and Shah, 2008). Patients who have a bacterial keratitis will typically present with a red and painful eye, and they may be experiencing photophobia or acute contact lens intolerance (Ehlers and Shah, 2008). Bacterial keratitis patients may also have mucopurulent discharge, corneal edema, an anterior chamber reaction, corneal infiltrates, or a corneal ulcer, which is more likely to be central than peripheral (Ehlers and Shah, 2008). Understanding the differences among the most common species causing a bacterial keratitis (e.g., gram negative versus gram positive) can affect the treatment plan and the overall clinical outcomes (Kanski, 2007).

Bacterial Species

Pseudomonas Aeruginosa This is an aggressive, gram-negative, rod-shaped bacterium that is most commonly associated with cases of bacterial keratitis in contact lens wearers (Kanski, 2007; Black, 2002). Pseudomonas aeruginosa is a commensal organism that requires corneal compromise to cause an infection. Ulcers stemming from Pseudomonas aeruginosa typically present with a “gray, necrotic appearance” that extends beyond the site of excavation (Hauswirth and Mangan, 2016).

Staphylococcus Aureus This is a gram-positive cocci bacteria (Black, 2002). Staphylococcus aureus is a commensal organism that requires corneal compromise to cause a corneal infection. It typically causes a “dense, round-to-oval, focal white infiltrate with clear margins” (Hauswirth and Mangan, 2016).

Streptococcus Pneumoniae This is a gram-positive diplococci (Black, 2002). Streptococcus pneumoniae is a commensal organism that requires corneal compromise to cause a corneal infection. It typically causes a “dense, round-to-oval, focal white infiltrate with clear margins” (Hauswirth and Mangan, 2016).

Bacterial Keratitis Treatment

Bacterial keratitis is more common in contact lens wearers than in non-wearers; contact lens wear introduces bacteria into the eye, and contact lens wear itself can cause the corneal compromise needed for the above commensal organisms to cause an infection (Evans and Fleiszig, 2013). If bacterial keratitis is diagnosed, contact lens use should be immediately ceased, old contact lenses should be discarded to avoid reinfection, and large (> 1mm) central ulcers should be aggressively treated or the patient referred to a corneal specialist (Ehlers and Shah, 2008).

Significant ulcers should be cultured along with the patients’ contact lenses and case, especially if the clinical appearance as described above is unclear (Ehlers and Shah, 2008; American Academy of Ophthalmology, 2013). Topical antibiotics should then be applied after diagnosis based upon the severity of the condition. To help manage inflammation, pain medication and cycloplegics may be administered, and topical steroids can be added after the condition is under control (Kanski, 2007). All patients should be monitored daily until the corneal epithelial defect is closed (Ehlers and Shah, 2008).

After the condition has resolved, patients can resume contact lens wear, though clinicians should extensively educate their patients about proper contact lens care and compliance, determine the likely precipitating factor (e.g., unprescribed overnight contact lens use), and create an alternative treatment plan (e.g., switching to daily disposable contact lenses) that helps patients avoid future red eyes (Morgan et al, 2011). CLS