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