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Ophthalmology Emphasizing Corneal and Refractive Issues

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The Blue Line Cataract Incision

The Blue Line incision is a simple technique to produce a scleral tunnel cataract incision, combining the efficiency in creation of a clear corneal incision with the safety of a scleral tunnel incision. Because the entry of blue line incision originates in the sclera, wound healing progresses much more quickly than comparable corneal healing and because the incision is longer  the incision is stronger (figure A).

A more in depth description can be found on this site in the Blue Line  paper and in The Blue Line Incision book.

 The initial reaction of an incision through the conjunctiva would be concern about chemosis during the surgical procedure. In fact the initial pass of the diamond knife creates an instant “mini-peritomy” which does not become chemotic with an efficient phacoemulsification. The key is to make the “mini-peritomy” larger than the final scleral tunnel incision.

The “Blue Line" that we use in this context is not the blue line that has been discussed in the past at the limbus. In this context, the blue line is posterior to the limit of the firm adherence of the conjunctive to the sclera , approximately 2 mm from the surgical limbus (figure B). At this location, the conjunctiva ends firm adherence to the sclera and becomes mobile. The external landmarks of the surgical limbus include a bluish translucent zone, 1 to 1.2 mm wide at the superior limbus when the conjunctiva is removed. The incision is made at the posterior border of this zone.The "Blue Line" incision is constructed by first creating with the side of the diamond knife, a 4.00 mm incision through the conjunctiva about 1.5 to 2 mm behind the surgical limbus (represented by an anatomic appearance of a blue line). In the usual case the conjunctiva sags naturally away from the incision and the resulting conjunctival gaping creates a “mini-peritomy”.

As seen in figure D, the knife is placed parallel to the posterior sclera and pressure is applied to slightly indent the sclera with the knife, pushing forward to begin the scleral tunnel incision. During the scleral tunnel construction, progressive pressure is applied on the heel of the diamond knife to prevent early interior entry caused by the changing curvature at the limbus between sclera and cornea (Figure D). Finally when the tip of the knife has approached the desired location for the internal corneal incision, the heel of the knife is rotated slightly upwards and the pressure is transferred toward the tip of the knife.  At that point, a slight dimple is visible in the corneal surface that disappears when the knife penetrates into the anterior chamber (Figure D). The knife is then inserted until the “shoulders” are at the level of the internal corneal incision, which is 2.5 mm in width (figure E). Light cautery is then applied to the conjunctival edge to control bleeding. The creation of the incision is simplified with the use of a “blunt tip” diamond knife and is slightly longer than the usual clear corneal knife. An advantage of the Blue Line incision is the ability to grasp the exterior of the wound during extraction of the cataract. Closure is usually completed with inflation of the eye through a side port. If the wound leaks,cautery applied to the sides of the scleral strip will enhance closure.

Click on the figures above to see larger clinical views of the incision creation.

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