Do Alpha-agonists and LASIK
Mix? Christopher J.
Quinn, O.D.
Some doctors have suggested
that Alphagan (brimonidine) may have neuroprotective properties as well the
ability to lower intraocular pressure in the management of glaucoma.
Others have pointed
to the transient increase in IOP that occurs when the surgeon applies suction
to the microkeratome during refractive surgery. They say this may induce
glaucoma-like optic nerve damage. (See “Does LASIK Damage the Nerve Fiber
Layer?” News Review, January 2000.)
Both hypotheses are tentative at
best. Until they are proven through rigorous scientific evaluation, it’s
probably not prudent to change our clinical practice patterns.
Complications Arise
Nevertheless, in response to the theorized optic
nerve damage that may occur during LASIK and because some evidence has been
presented that Alphagan has neuroprotective properties, some surgeons have
incorporated the routine use of Alphagan as a preoperative treatment for LASIK.
But as this
treatment became briefly popular, a number of other complications associated
with the use of Alphagan surfaced. The most significant was an apparent
increase in the number of cases of flap slippage. Refractive surgeons have
observed flap slippage the day following LASIK.1,2 It’s easy to recognize
flap slippage following LASIK because the flap shrivels and bunches at the
hinge. Patients complain of poor vision and pain the day following surgery.
The flap slippage
occurs due to poor adhesion between the flap and underlying corneal bed, which
probably results from poor endothelial cell function. Corneal endothelial cells
create an osmotic gradient that maintains the cornea in a state of relative
dehydration. If the endothelial cells don’t function adequately, the flap
may not properly adhere to the corneal stroma. Slippage may also occur if the
ocular surface is too dry and the flap instead adheres to the eyelid, resulting
in mechanical flap dislocation.
Treatment Succeeds
Fortunately, surgeons can treat most cases of flap slippage
successfully. The surgeon can “refloat” the flap, re-dry the cornea,
and then place a bandage contact lens on the eye to protect to the flap and
prevent recurrence. Patients still can achieve excellent visual results,
although the best results occur if the surgeon repairs the flap as soon as
possible following surgery.
So if alpha-agonists are associated
with flap slippage, do they have any role in refractive surgery? Not as
neuroprotective agents, but they probably do for other reasons. Indeed,
alpha-agonists are effective in dehydrating the conjunctiva, and they are also
powerful vasoconstrictors that don’t induce significant papillary
dilation.
In
patients who have peripheral corneal neovascularization who would otherwise
bleed following the creation of the LASIK flap, pretreatment with Alphagan or
Iopidine (apraclonidine) results in rapid vasoconstriction and prevents
bleeding during the procedure. This is particularly useful in cases where a
large flap may impinge on these peripheral corneal blood vessels.
Alphagan or
Iopidine may help when the surgeon has difficulty obtaining suction with the
microkeratome because the patient has a thick or boggy conjunctiva. These drugs
can dehydrate the conjunctiva so that the microkeratome achieves appropriate
suction and the surgeon can make a successful microkeratome pass.
Neuroprotection may
be the Holy Grail of glaucoma management, but its day has not yet come, and it
certainly is not ready for prime time in refractive surgery. u
Thanks to Brian Den
Beste, O.D., Orlando, Fla., for his input and expertise on this topic.
- Walter KA. Adverse effect of
Alphagan on LASIK flap adherence. American Society of Cataract and Refractive
Surgery Abstracts May 2000;155.
- Talamo JH, de Luise VP. Increased
incidence of flap slippage after LASIK associated with the use of preoperative
Alphagan. American Society of Cataract and Refractive Surgery Abstracts May
2000;155. Rk, Ab
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