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© 2016, BSM Consulting
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Modern Glaucoma Surgery
anxiety may experience substantial stress being covered this extensively while awake. Patients with
respiratory problems can become short of breath if positioned on their backs for extended periods of time.
One important question to ask people with breathing problems is how many pillows they sleep with at
night. If the answer is two or more, there may be anticipatable breathing issues during surgery and a
consultation with the anesthesiology support staff may be warranted preoperatively. Likewise, morbidly
obese patients may have difficulty with supine positioning and may also warrant anesthesia consultation.
A thorough past medical history is a standard component of the preoperative evaluation. Special
emphasis should be placed on a history of bleeding or clotting issues, as well as the use of any blood
thinners. Many patients take a daily baby aspirin and forget to list it because it is not a prescription
medication. These issues should be directly queried, as some forms of glaucoma surgery can result in
bleeding, the risk of which can be minimized with preoperative planning.
Finally, patients who have had prior surgeries of any kind—ocular or otherwise—should be asked if they
had any problems at all during their prior surgeries. Specifically, they should be asked if they had any
reactions to drugs administered during past procedures. This information is easy to obtain and can make
a huge difference in surgical outcomes in patients who are prone to reactions to common perioperative
medications.
Examination
Visual acuity must be assessed before any procedure for medicolegal reasons: any pre-existing deviation
from 20/20 vision post-procedure could be attributable to the procedure if the baseline acuity is not
documented beforehand. Also, visual acuity decline that is attributable to cataract may be an indication
for a combined cataract and glaucoma procedure. In addition to the trabecular bypass procedures
previously described that are commonly paired with cataract surgery, both trabeculectomy (with or without
an Ex-PRESS implant) and less commonly tube-shunt implantation can be paired with cataract surgery if
there are coinciding indications for both procedures.
IOP is both an indication for glaucoma surgery and the primary benchmark by which surgical success will
be determined. IOP is a dynamic biometric parameter that varies significantly over time. Not uncommonly,
patients referred for glaucoma surgery based on elevated IOP will have a reasonably normal IOP at the
time of the consultation. A single measurement of IOP generally is inadequate to characterize the breadth
of IOP behavior, so whenever possible, IOP should optimally be assessed more than once before
committing to surgical intervention. Ideally these would occur on different days and at different times of
day to account for diurnal IOP variation.
The anterior segment examination should identify any evidence of conjunctival scarring that might affect
surgical planning. Prior surgery involving the conjunctiva (for instance, scleral buckling or strabismus
procedures) or ocular surface inflammatory conditions (such as ocular pemphigoid) can increase the risk
of glaucoma surgery failure. Likewise, the technician should be alert for signs of secondary glaucoma that
might affect management decisions. These include keratic precipitates on the corneal endothelial surface
indicative of uveitis, blood vessels on the iris surface suggestive of neovascular glaucoma,
pseudoexfoliation on the anterior lens capsule, or narrow angles by the von Herick test, which may
indicate angle-closure glaucoma.
Preoperative perimetry is necessary both to document the need for surgical intervention as well as to
provide a baseline from which future progression can be detected.
A dilated examination of the posterior segment should be performed preoperatively; although the
technician should not dilate a new patient referred for glaucoma evaluation until after the doctor has
examined the anterior segment. Like perimetry, documentation of the optic nerve appearance (using a
drawing, photography, or imaging technology) verifies the need for surgical intervention and provides a
baseline from which future progression can be detected.