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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.
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