Since
glaucoma patients are by definition at risk of losing vision from a potentially blinding disease, the first objective in glaucoma surgery is always to stabilize their glaucoma and prevent further damage.
Refractive considerations are secondary, and in many cases, appropriate glaucoma treatment will necessarily incur some unwanted refractive changes.
When more than one surgical option can effectively address the patient’s glaucoma, however, the refractive implications of these options can play a role in surgical planning. In these cases, surgeons may opt for the procedure that is least likely to affect patients’ vision and/or one that does not impair their ability to wear contact lenses.
While trabeculectomy, is a less-than-ideal procedure from a refractive standpoint, it remains the gold standard for controlling intraocular pressure (IOP), so I often opt for this procedure with more advanced cases of glaucoma, even if it means I must subsequently address surgically-induced astigmatism or fit these patients with spectacles.
Similarly, canaloplasty and deep sclerectomy procedures also have the potential to induce astigmatism, since these procedures involve removing a fairly sizable block of deep scleral tissue. As with trabeculectomy, patients who undergo canaloplasty or one of the deep sclerectomy variants may need subsequent treatment to address surgically-induced refractive change.
With aqueous drainage devices such as Ahmed™ (New World Medical) and Baerveldt® (AMO) shunts, on the other hand, the effect on refraction is relatively minimal, assuming the patient does not develop hypotony after surgery. The Ex-PRESS™ mini-glaucoma shunt (Optonol) also has minimal effect on refraction; in fact, because the Ex-PRESS shunt can be implanted with a 27-gauge needle track entry into the eye, the potential for surgically-induced astigmatism may be even less with this device than with standard shunts, although the scleral sutures may induce some astigmatism as with a standard trabeculectomy.
Finally, Trabectome® (NeoMedix) procedures, when performed through a 2-mm to 3-mm clear corneal incision, should have minimal effect on refractive status, while laser trabeculoplasty and endocyclophotocoagulation (ECP) should not affect refractive status at all. While they may not lower IOP as effectively as trabeculectomy, trabeculoplasty and ECP are suitable options for many less advanced cases of glaucoma, and their refractive neutrality is an added bonus.
Having this range of options allows me to consider the refractive side effects of a procedure in some cases. The degree to which I consider the refractive implications of a procedure depends on several factors, including patients’ age, their preferred method of vision correction, and the status of their glaucoma.
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