May 2008

 

CATARACT/ IOL

 

Endoillumination probe, an alternative to dyes


by Matt Young EyeWorld Contributing Editor

 

What you should know about the new endoillumination technique

• This technique differs from previous ones in that the endoilluminator is held on the peripheral corneal surface instead of on the limbus.

• It essentially eliminates any reflection from the corneal surface that may decrease the clarity of vision.

• The contrast between the anterior capsular flap and the underlying cortical fibers under green illumination is optimized so the edges of the capsulorhexis are more refractile.

• It is an alternative to dyes like trypan blue.

• The surgeon does have to move the endoillumination probe as the capsulorhexis is created, which could be bothersome.

Source: Tugrul Akin, M.D.

 

Study describes use of probe

Anterior view of a human eye obtained postmortem with advanced cataract that shows the staining of the anterior capsule using trypan blue

Trypan blue (VisionBlue, Dutch Ophthalmic Research Center International, B.V., Zuidland, The Netherlands) often is cited as an excellent agent to assist with visualization during cataract surgery when the red reflex is poor or absent.

But it’s not a foolproof method. Complications have been reported in association with trypan blue, including permanent blue discoloration of some expandable hydrophilic acrylic IOLs. In lieu of trypan blue, there are alternatives for enhanced visualization. One newly described technique associated with an endoillumination probe could be a good alternative. “With the technique we described, we found that the contrast between the anterior capsular flap and the underlying cortical fibers under green illumination is enhanced, allowing the edges of the capsulorhexis to be more refractile and more clearly defined,” wrote lead study author Tugrul Akin, M.D., GATA Haydarpasa Egitim Hastanesi, Istanbul, Turkey.

In detail

Dr. Akin described this technique as one that includes attaching a green filter to the endoillumination unit of the vitrectomy set. Some vitrectomy models even have green-light filters pre-installed, Dr. Akin noted. The surgeon then turns off the operating room and microscope lights. “The surgeon uses his or her non-dominant hand to hold the endoilluminator as a green-light source, which can be placed in any position on the peripheral cornea,” Dr. Akin reported. “The endoilluminator is held obliquely such that the surface of its tip is horizontal to the surface of the cornea, completely covering the corresponding corneal surface underneath it, and the light beam is perpendicular to the edge of the capsulorhexis. This provides a clear view of the anterior segment under green illumination.” So the capsulorhexis is performed with the aid of the green light of the probe, “which was placed on the periphery of the cornea in a manner that followed the tearing edge of the capsulorhexis,” Dr. Akin reported. “The surgeon changes the position of the endoillumination probe on the peripheral cornea at each 45 degrees to 90 degrees in the same direction as the tearing edge of the capsulorhexis is advanced.”

So why does the green light work?

The green light enters directly into the corneal tissue. It avoids any reflection from the corneal surface and “allows the edges of the capsulorhexis to be relatively reflective and well delineated with higher contrast,” Dr. Akin reported. Dr. Akin noted the potential problems of using a dye during visualization, including staining the corneal tunnel and side port. Plus, they can be expensive. Further, Dr. Akin noted, “Trypan blue, which is one of the most commonly used capsular dyes, may cause inadvertent staining of vitreous, especially in cases with suspected zonular dialysis.”

This also is not the first time endoillumination has been described for such purposes. However, this technique is distinct. Formerly, an endoilluminator was described as being held at the limbus parallel to the plane of the iris. “Our technique differs from theirs in that we use a green filter, and we hold the endoilluminator on the peripheral corneal surface instead of the limbus,” Dr. Akin noted. “The surface of the tip of the endoilluminator is just parallel to the surface of the cornea, and this way we virtually eliminate any reflection from the corneal surface that may decrease the clarity of vision due to interference.”

It is, however, disadvantageous that the surgeon must move the probe as the capsular flap is created, due to the limited green light emitted, Dr. Akin found. “A wider probe or a new apparatus that could be placed on the peripheral cornea and provide green illumination with a wider field may be designed in the future for this purpose,” Dr. Akin concluded. Still, Mark Packer, M.D., clinical associate professor, ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, said that at this point in time, alternatives to trypan blue aren’t really warranted. Using endoilluminators used to be a valid approach for visualization, but now capsule staining can safely be performed with highly viscous ophthalmic viscosurgical devices to prevent leakage.

So now, using an endoilluminator is “just an extra hassle,” Dr. Packer said. “It’s putting something else on the eye that you have to hold.”

Editors’ note: Dr. Akin has no financial interests related to this study. Dr. Packer has no financial interests related to his comments.

Contact Information

Akin: akintugrul@yahoo.com

Packer: 541-687-2110, mpacker@finemd.com

Endoillumination probe, an alternative to dyes Endoillumination probe, an alternative to dyes
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