Contact lens induced peripheral corneal infiltrates

 
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Peripheral corneal infiltrates
 
Peripheral Corneal Infiltrates

Peripheral corneal infiltrates are a class of contact lens associated corneal infiltrates or CLACI. In this condition, inflammatory cells enter the cornea in response to the presence of toxins or other eye irritants. The disorder is mostly limited to the edges of the cornea. This is so because it is a secondary infection spread from an already infected sclera - the white part of the eye or an infected conjunctiva - the inside lining of the eyelid. The periphery is affected because of its proximity to these two eye structures. The disorder can cause considerable discomfort but it is not eye-threatening.

The numbers affected are small in percentage terms but are large enough in absolute terms to warrant attention.

Types of infiltrates

Infiltrates can be sterile or infectious. Peripheral infiltrates are typically sterile infiltrates where microbes are present but inactive. They are normally less than 1mm. in diameter size, peripheral, hazy and having well defined edges. However, there are infectious infiltrates less than 1mm in diameter and non-peripheral infiltrates, which are sterile.

Types of peripheral infiltrates

Peripheral infiltrates are further classified as contact lens induced peripheral ulcer or CLPU and contact lens associated red eye or CLARE.

CLPU is associated with ulcers. It is seen with daily wear contacts but is more common with extended contacts. Initially the condition of CLPU is acute and presents with or without symptoms. The symptoms include redness, pain and watering. Clinical features of CLPU are circular, dense, focal and peripheral to mid-peripheral infiltrates with epithelium involvement.

CLARE is most commonly seen with extended wear contact lenses. The patient is typically woken up from sleep and notices some symptoms. These include moderate pain, redness, burning sensation, tearing and photophobia. Clinical features of CLARE are focal or diffuse, peripheral to mid-peripheral infiltrates with typically no epithelium involvement.

Causes of peripheral corneal infiltrates

Microbial presence: Although bacteria are undoubtedly associated with peripheral infiltrates, in CLACI the relationship is not straightforward.

Studies show that degree of lens colonization sometimes depends on the individual patient. Furthermore, a generalized colonization has been observed in the presence and absence of infiltrates. The intensity of the response also depends on the bacteria strain. Bacteria detection is sometimes difficult in bio-film contact lenses. These factors show that the relationship between infiltrates and bacteria is quite complex.

Contact lens use

CLACI is also seen with contact lens use. Contact lens related problems like hypoxia can trigger inflammation. The contact lens can itself be a vehicle for bacteria. Contact lens deposits, especially in soft contacts are often a direct cause of infiltrates.

Overnight wear

The higher incidence of CLACI with extended wears strongly suggests the closed eye as an important cause. During sleep the eye is in a sub-clinical inflammatory condition, protected by the eyelid from microbial infection. The several host agents in the eye trigger the inflammation.

Lens fit

A tight lens can sometimes be a direct cause of CLACI. Tight lenses prevent free eye movement and blinking causing tear stagnation and preventing the tear from cleaning the debris under the lens. The stagnating tear and the debris trigger inflammation. It is also called a ‘tight lens syndrome’.

Lens replacement schedule

Absence of regular lens replacement schedule may also cause CLACI. Otherwise, it is difficult to explain the presence of infiltrates in regular replacement soft contacts and even in disposable contacts which are known to have considerably reduced eye complications.

Lens material

Incidence of CLACI is higher in hydrogel lenses than in PMMA or RGP lenses indicating material susceptibility. Infiltrates are higher in high water content lenses perhaps due to higher deposits in such lenses. Higher water content lenses also have higher absorption levels which may lead to easier absorption of inflammation causing organisms.

Solution preservatives

CLACI has been associated with hypersensitivity to lens solutions like thimerosol and chlorhexidine. A retrospective study on 1600 patients with CLACI showed 1% with such hypersensitivity.

Lens care

In a prospective study on 94 patients with CLACI inadequate lens care was a major cause. The incidence of CLACI was higher with daily wear disposables than in extended disposables. The reason, it is believed, was poorer lens care regime with daily wears which need more frequent cleaning.

Treatment

Treatment should firstly remove and control the responsible organism and then remove the destructive components of inflammation. Since it is a secondary infection, a conservative treatment with only topical antibiotics initially for 24 to 48 hours and then a judicious addition of topical steroids should best eradicate bacterial colonies. Eyelids should be cleaned regularly with baby shampoo or lid scrubs.

Patient’s progress should be monitored after resolution. If the problem recurs, the patient should change over to daily wear or RGP lenses.