Healthcare and Medicine Reference
In-Depth Information
In summary, it is important to ensure suffi cient oxygen supply to
the cornea and thus its epithelium. In doing so, the health status is best
maintained and the self defense is strongest. Next to oxygen, one should
avoid weakening or disrupting the corneal epithelium by mechanical effects,
i.e. the fi t of the CL or the fi nger nails during manipulation. Foreign bodies
that are trapped under the CL may also cause such trauma. LCPs can affect
the epithelium integrity as well. Staining the cornea reveals the type of the
alteration of the epithelium, its depth and extent. Any grade of three or
higher on the CCLRU grading scale should trigger a more detailed search
for the potential cause(s) and a possible resolution.
Superior Epithelial Arcuate Lesion (SEAL)
When mentioning superior epithelial arcuate lesion (SEAL), many
practitioners immediately associate this condition with a) SiHy CLs and b)
material rigidity. In 1987, Hine et al. reported about the aetiology of SEALs
(Hine et al. 1987), Jones et al. also describe them as being “relatively common
complications in soft CL wear” and to be “found in all soft CL types”
(Jones et al. 1995). These 2 to 5 mm long and 0.1 to 0.3 mm wide splits of
the epithelium can be found in the superior and peripheral cornea (within
1-3 mm of the limbus and between 10 and two o'clock) and run parallel
to the limbus. They can present themselves combined with symptoms
(irritations, burning, itching and photophobia) and an associated reduced
wearing time or asymptomatic. They may be bi- or monocular. In the case
with irritations, superior bulbar and palpebral conjunctival redness may
be present, too. Their existence may be attributed to the combination of
the CL material, design, dehydration characteristics, hypoxia, and solution
used. The pressure that the upper lid exercises on the CL when it moves
over it during the blink and the CL movement during the blink over the
cornea may be the mechanics and the friction required to break/split the
epithelium.
The condition usually resolves within a few days (three to four) of
non CL wear. Frequent use of lubricants/artifi cial tears may be advisable
during that time. Some ECPs may also recommend the prophylactic use of
antibiotics. Thirty seven percent of the cases will have a reoccurrence when
using the same CL and or LCP. It may therefore be better to think about an
alternative CL (design, fi t etc.) or LCP.
CL design and the choice of base curve are more important than the
material's rigidity (often mentioned as being a major driver). The case
of changes made by one manufacturer to its high modulus SiHy CL
that showed a much higher incidence of SEALs than the other SiHy CL
launched at the same time (all attributed it to the modulus) is proof to this.
The change of the back surface design from a tri-curve to an aspheric one
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