Some surgeons prefer to make a superior phaco incision while others prefer a temporal approach. Is there a substantial difference and what are the considerations when choosing where to make the crucial main incision for cataract surgery? For most patients I prefer a temporal phaco incision because it provides the easiest access to the anterior and posterior chambers even if the brow is prominent or the eyes are deep-set. Also the temporal limbus is farthest from the visual axis and thus the astigmatic effect of the phaco incision is the least. But what about patients who have a degree of with-the-rule (WTR) astigmatism which has a steep axis at or about 90 degrees?
A temporal phaco incision is farther from the visual axis than an identical incision placed at the superior position. As such, the superior incision will induce more corneal flattening and more astigmatic effect compared to like incisions placed temporally. We can use this to our advantage in patients who have pre-existing with-the-rule (WTR) astigmatism and a steep axis at or about 90 degrees.
The superior approach can be more difficult in patients with prominent brows and/or deep-set eyes. The temporal approach tends to offer better access in these types of patients. An advantage of the superior incision is that it is protected under the upper eyelid compared to temporal incisions which are more exposed.
In the case here, the patient has about 1 diopter of corneal astigmatism, steep at 105 degrees. We place our phaco incision at this axis and that will help neutralize the majority of the pre-existing astigmatism. We are careful to place our incision at the limbus, barely nicking the blood vessels, and with a tunnel length that avoids encroaching on the visual axis. Our patient is also highly myopic and we determined via www.IOLcalc.com that an IOL power of +7.0 D would give her a post-op result of about -0.25 spherical.
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