|An uneven laser ablation can create an irregular corneal surface resulting in a topographical "island" as shown by the central red spot.
A central Island is a complication of excimer laser assisted refractive surgery that occurs when the laser fails to remove a portion
the cornea in the ablation zone. Light passing through the resulting bump in
the cornea bends erratically and
presents very poor vision. Visual symptoms of a central
island typically include distortion or monocular diplopia.
Central islands are exceedingly rare with current techniques and technology.
Why A Central Island Occurs
A central island tends to occur more often with a broad-beam type laser, when a foreign substance like water or
oil inadvertently gets on the corneal bed, or when the plume of escaping cells interferes with subsequent laser pulses. Central islands only occur with conventional
or custom wavefront Lasik, Bladeless Lasik, PRK, LASEK, or Epi-Lasik excimer laser assisted procedures. A central island can not occur with lens based refractive surgery procedures like RLE and P-IOL.
There are many treatment options for a central island and resolution
of some degree is highly likely, however a patient with a central island should proceed carefully with
any additional wavefront guided laser treatment. Wavefront guided ablation tends to provide limited relief from a central island. A central island is primarily a topography issue, not one
of higher order aberrations, which wavefront normally excels at resolving.
A noninvasive technique for central island resolution
is the use of contact lenses. A contact lens may "smash down" the central island and create
a more uniform surface. If the central island is shallow,
a soft contact may resolve the problem. If the central island is significantly
elevated, a Rigid Gas Permeable (RGP) contact lens may be the better
A more aggressive technique that may be appropriate to resolve a central island
is Contact Lens Assisted Pharmacologically Induced Kerato Steepening
(CLAPIKS). We have a detailed article about 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.
Depending upon the nature of the central island, a topography-guided flying spot laser ablation may remove the excess tissue and return the cornea to a more regular surface by applying laser energy only to the raised area.
Another topography based treatment for resolution of a central island
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 use of the 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 4,000 patients per year with rare medical
C-CAP uses a liquid material that is applied to the outside of
the cornea. 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 broad-beam 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.
Where To Seek Help
Before 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 obtained. A teaching hospital will commonly provide the greatest
level of resources, 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:
- Get a second opinion from a corneal specialist.
- Use a contact to reshape the cornea, soft or RGP as required.
- Discuss CLAPIKS with your doctor.
- Evaluate C-CAP or similar topography-based procedures.
How To Avoid A Central Island
The best way for a patient to avoid a central island is select
a doctor who uses current technology and has a proven track record of success. Selecting an evaluated doctor or evaluating a doctor yourself is always wise.
Looking For Best Lasik Surgeon?
If you are ready to choose a doctor to be evaluated for conventional
or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization.
Locate a USAEyes Evaluated & Certified Lasik Doctor.
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