Central Islands are a complication of
excimer laser assisted
refractive surgery when the laser fails to remove a portion
of
cornea. A central island is exactly what it sounds like, a small
island of raised tissue in the center of the cornea. This bump in
the cornea causes light passing through it to bend erratically and
creates very poor vision. If one views the concave area of the
ablation zone like the bottom of a lake, one can imagine an
island sticking up in the center.
Visual symptoms with central
islands are typically monocular
diplopia or distortion. Central islands only occur with conventional
or custom
wavefront
Lasik,
All-Laser Lasik,
PRK,
LASEK,
Epi-Lasik
excimer laser assisted procedures. Central islands can not
occur with lens based refractive surgery procedures like
RLE and
P-IOL, nor can they occur with
Intacs.
Central islands are quite rare with current techniques and technology.
Central islands tend to occur more often with a
broadband beam type laser and a conventional
ablation (not
wavefront-guided). These days about the only cause of a central
island is the use of broadbeam lasers or something like water or
oil getting on the corneal bed just before the laser treatment.
The best way for a patient to avoid a central island is select
a laser that uses a
flying spot technology, not broadbeam technology. Keeping the
treatment bed absent of impurities is the doctor's responsibility,
so selecting an
evaluated doctor or
evaluating a doctor yourself is always wise.
A central island is not a desirable complication...not that there
are any that are actually desirable...with slow recovery and additional
treatment necessary. There are many options available and resolution
of some degree is highly likely.
The first and least invasive technique for central island resolution
is the use of contact lenses. If the central island is shallow,
soft contacts may do the trick. If the islands are significantly
elevated, a Rigid Gas Permeable (RGP) contact lens may be the better
choice. This type of lens will "smash down" the island and make
a more uniform surface. If there is no refractive error other than
the central island, RGPs without correction are available.
A technique that may be appropriate to resolve central islands
is called
CLAPIKS. We have a detailed article on CLAPIKS including a downloadable
white paper for your doctor to review. This is an advanced use of
contact lenses and topical eye drops to reshape the cornea.
A patient with central islands should proceed carefully with
any additional laser treatment. At least, laser treatment in the
conventional sense. Wavefront diagnosis is usually dreadful with
central islands. A central island is a topography issue, not one
of
higher order aberrations which wavefront excels at resolving.
A topography based laser treatment for resolution of central islands
is Custom Contoured Ablation Pattern (C-CAP).
C-CAP is the customization of laser vision correction treatments
for central islands and similar corneal aberrations. The
FDA has approved the use of C-CAP method with an excimer laser
under a Humanitarian Device Exemption (HDE). Procedures under a
HDE are medical procedures specially designated by the FDA for the
treatment of fewer than 4000 patients per year with rare medical
conditions.
C-CAP uses a liquid material that is applied to the outside of
the eye. In some cases, a contact lens is applied over the liquid
to give a smooth surface. The liquid becomes more firm, and the
contact (if used) is removed. A broadbeam laser applies energy to
the entire treatment area with each pulse. The liquid ablates at
the same rate as corneal tissue. As the laser removes tissue or
the liquid, the high areas of the cornea are exposed and ablated
down to the low areas. C-CAP has been shown to resolve many topographical
imperfections caused by disease, trauma, or surgery.
Before you a patient with a central island considers any surgery
of any kind, it is very highly recommend that the opinion of a corneal
specialist, preferably one who is affiliated with a nearby teaching
hospital, is attained. A teaching hospital will provide the greatest
amount of resources available, and the second opinion will provide
an affirmation that the proposed corrective procedure is appropriate,
and the peace of mind that the patient is on the right path to recovery.
Recommendations for patients with central islands are:
1) Get a second opinion from a corneal specialist.
2) Get a pair of contacts, soft or RGP as required.
3) Discuss CLAPIKS with your doctor
4) Evaluate C-CAP or similar topography-based procedures
If you are ready to choose a doctor to be evaluated for conventional
or custom
wavefront
Lasik,
All-Laser Lasik,
PRK,
LASEK,
Epi-Lasik,
NearVision CK,
RLE, or any
refractive surgery procedure, we highly recommend you consider
a doctor who has been evaluated and certified by the USAEyes nonprofit organization.
Locate a USAEyes Evaluated & Certified
Lasik Laser Eye Surgery Doctor.
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