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An American Society of Cataract and Refractive Surgery (ASCRS) committee 2013 review quoted the incidence of incomplete femtosecond laser assisted cataract surgery (FLACS) capsulotomies as having been reduced from over 10% initially, to about 1%.
The microscopic serrations induced by femtosecond lasers have been blamed for the reduced strength of a FLACS capsulotomy, and manufacturers have adjusted the power and distribution of laser pulses to make the serrations finer and overlapping. Other contributing causes are optical shielding of the capsule by corneal scars; the anterior capsule being irregular, crenated, or fibrotic; adhesions to underlying cortical fibers; and increased intracapsular pressure (hypermature cataract).
A free cap may be attached at a single small point, have multiple discreet residual attachments, or have floated free over 80%–90% of its surface, folded back over the peripheral lens and remain anchored to a broad attachment area in a radially awkward-to-access position. To reduce tear-outs, it is desirable to have a surgical strategy to reliably complete capsulotomies as the very beginning of surgery.
An incompletely free cap tear-out is most similar to Argentinean flag sign, where there is increased posterior pressure pushing forward against the anterior capsule, because femto-created gas from nuclear softening may be trapped intralenticularly.
When the surgeon grasps the capsular flap and pulls radially, and inevitably anteriorly as well, the tear wants to spiral outward. The common method of grasping the cap centrally with microforceps and pulling the edges of the flap centrally, thus attempting to mimic the Little tear-out rescue radially, usually works, but may be insufficient in some cases to avoid outward extension.
Instead, a pressure-equalized cataract surgery method, “the FLACS OVD press,” similar to what I have described for hypermature cataracts will just about always work, because the induction of pressure anterior to the anterior capsule with an ophthalmic viscosurgical device (OVD) pushing posteriorly counterbalances the forward-pushing intracapsular pressure and encourages the capsule to tear inward.
Trypan blue is not used because, unlike with Argentinean flag sign, the capsulotomy is mostly completed and clearly visible in FLACS cases. The addition of trypan blue would allow the anterior chamber (AC) to shallow, lowering the AC pressure and thereby encouraging extension of the tear.
After prepping and draping the eye, a mixture of 1% isotonic nonpreserved xylocaine and 0.1% phenylephrine is injected intracamerally through the side port to pressurize the eye and enhance anaesthesia and pupil dilation.
After waiting about 20 seconds for pupil dilation, Healon or Healon GV (preferred for their 27-gauge thin-walled cannulas that are easier to insert under the corneal dome) is injected over the centre of the laser-created cap until the cap becomes concave. If the cap has folded over the peripheral capsule, it is simply directed back with Healon or Healon GV, which is easier than if the more viscous Healon5 is used.
Observation of the cap at this point will clearly show where the cap is free (separated from the peripheral capsule in an arc), and where it remains attached. The small sharp tips of a fine capsulorhexis instrument are used to grasp the capsule near the residual adhesions to depress the cap posteriorly and pull it centrally. With a circular motion (learned in another context, from James Gills, many years ago), of combined depression into the lens and central dragging, the tear is completed (Fig. 1, Fig. 2; Videos 1 and 2). The combination of pressure-equalized cataract surgery to depress the central capsular surface, and the inverted Gillsean capsulorhexis prevents the capsulotomy from tearing outward, and can be initiated anywhere over the 360 degrees of the cap. In 352 consecutive cases, 2 of 102 cases had suffered anterior capsulotomy extensions before I developed this technique, whereas 0 of the 250 subsequent cases using this technique developed anterior capsular tears (p < 0.05, calculated at www.openepi.com/TwobyTwo/TwobyTwo.htm; mid P exact).
Footnotes and Disclosure
The author has no proprietary or commercial interest in any materials discussed in this article.
Video 1—FLACS OVD Press. This video shows case 1, in which, from the viewpoint of the video, the left superior aspect of the capsulotomy appears to not be separated from the peripheral capsule. As the ophthalmic viscosurgical device (OVD) is injected between the cap and the corneal dome, the separation of the cap from the peripheral capsular ring is seen to gradually increase. Injection is stopped when the centre of the cap is seen to become concave. At that point the previously attached area of the capsulotomy is uncertain as to whether it is entirely free or not, as sometimes just the OVD injection alone can free it. The forceps action to depress the edge of the cap and pull centrally completely frees the cap and it is removed.
Video 2—FLACS OVD Press. This video shows case 2, where the pupil is inadequately dilated, and the cap appears to be attached to the peripheral capsule for over 180 degrees in the left and inferior aspects. The ophthalmic viscosurgical device (OVD) injection does not free the cap. Depression of the cap edge and pulling centrally can be seen to tear the cap free from the peripheral capsule. The free cap is then removed.
Inter-eye comparison of femtosecond laser-assisted cataract surgery capsulotomy and manual capsulorhexis edge strength.
Presented, in part, at the American Society of Cataract and Refractive Surgery annual meeting, San Diego, CA, May 5, 2019; at European Society of Cataract and Refractive Surgeons annual meeting, Paris, September 16, 2019; at Videocataratta-Refractiva, Milan, October 25, 2019; and at McMaster University, Hamilton, Ont., Department of Ophthalmology Research Day February 19, 2020.