Conjunctival chemosis can happen during cataract surgery if one of our incisions nicks the edge of the conjunctiva. This allows fluid to egress from the anterior chamber infusion to the space under the conjunctiva which then balloons it. The solution is relatively easy and it should be done prior to being completely underwater.
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In the event that the wound is too gimbal form the outset, I would be inclined to free the conjunctiva on either side of the phaco main incision before chemises starts. Or once chemises starts early on during phaco, would use a keratose to free the conjunctiva on either side of the incision. Once the conjunctiva has ballooned to the extent that you have shown, one could easily use a Westcott spring scissors to make large radial cuts; which as you rightly said heal with no consequence..