Capsular Dye by David Chang

Capsule staining and mature cataracts: a comparison of indocyanine green and trypan blue dyes
David F Chang

Accepted for publication 3 May 2000
 

Video.The capsulorhexis for a dense white cataract is shown in the first segment of the video, where capsule visualisation is limited by the poor red reflex and by the release of milky cortical material. In the second segment, ICG staining is performed after injecting air into the anterior chamber; visualisation of the greenish capsule facilitates capsulorhexis. In the third segment, trypan blue provides intense blue staining to allow capsular visualisation.

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Background:

Of the numerous challenges that mature white cataracts present to the phaco surgeon, the most significant one is visualisation of the capsulorhexis. In addition to the complete absence of the red reflex, the liberation of cortical "milk" following perforation of the anterior capsule further compromises visibility. The excessive hydration of these lenses also promotes peripheral radial extension of the developing capsule tear.

Many techniques have been proposed for improving anterior capsule visualisation in such eyes. Although oblique illumination with a fiberoptic light pipe is effective, the most reliable method is the use of a dye to stain the anterior capsule. Indocyanine green (ICG) dye, as reported by Horiguchi et al1, and trypan blue dye, as reported by Melles et al2, each work beautifully in this regard. They are both superior to fluorescein3 which, because it is a much smaller molecule, diffuses into the lens and the vitreous. Use of any of these dyes in cataract surgery constitutes an off label use.

Technique:

ICG (Akorn) is widely used for fundus angiography, but is not FDA approved for capsule staining. It comes as a lyophilised compound, which must first be dissolved in 0.5 ml of sterile diluent supplied by the manufacturer. It is then further diluted with 4.5 ml of BSS Plus (Alcon) immediately prior to use. This creates a 270 mOsm, 0.5% concentration. Trypan blue dye (Vision Blue, DORC, Netherlands) is available in Europe for capsule staining and is supplied as a premixed sterile solution. It is not currently available in the United States.

An identical technique is used with either dye. Through a small paracentesis, the anterior chamber is filled with an air bubble to avoid excessive dilution of the dye. Using a 30-gauge cannula several drops of dye from a TB syringe are placed directly onto the anterior capsule surface, which is stained immediately. Through the paracentesis, the air is then exchanged for BSS, which is used to irrigate the dye out of the anterior chamber. Waiting 10-15 seconds to remove the dye can intensify the staining. Following viscoelastic placement, the capsulotomy is performed in the usual manner. No special illumination is needed. At first the capsule may not appear very coloured. However, once the tear is initiated, the white cortex creates a "white reflex" against which the stained capsule is easily delineated.

Comments:

The use of capsular dye does not eliminate other problems posed by mature white lenses. The egress of cortical "milk" may still impair visibility of the anterior capsule. An irrigating cystotome has the advantage of lavaging the milky material away, and can be used in young patients to initiate the tear when this problem is anticipated. If there is liquified cortex, the resulting intralenticular fluid pressure may also cause peripheral radial extension of the capsular tear. One must optimise control of the tear by proceeding slowly, frequently regrasping and redirecting the flap, maintaining a deep chamber, and erring towards a smaller diameter.

Besides the white cataract, capsular staining is helpful in any situation where either the red reflex is poor or visualisation of the capsule is compromised. The presence of asteroid hyalosis, corneal scarring, corneal edema, or a dark brunescent nucleus are examples of other such situations.

Clinical studies of both of these capsular dyes have been published. In April 1998, Horiguchi et al reported the results of their technique in a prospective, randomised study of 20 patients with mature white lenses1. Ten patients underwent ICG capsule staining, and the other 10 served as a control. Specular microscopy and laser flare-cell photometry were compared and showed no statistical difference between the two groups.

ICG creates a pale green staining of the capsule, which is gone by the conclusion of the case. One slight disadvantage is that the dye is lyophilised and larger particles often remain suspended in the mixture. These may appear in the anterior chamber, but seem to be eliminated during the ensuing irrigation/aspiration steps of the cataract surgery. Because BSS Plus (Alcon) is used for the mixture, the dye must be discarded at the end of the day.

In January 1999, Melles et al reported on the use of trypan blue dye in 30 patients with mature white cataracts2. There were no complications attributable to the dye. He also cited trypan blue’s long track record of safety when used to stain and examine endothelial cells in donor corneoscleral buttons. Since May 1998, I have used ICG dye in a total of 18 mature white or brunescent cataracts, and trypan blue dye in an additional 10 cases. Both have provided consistently excellent visualisation and clinical results. I have not experienced any adverse problems attributable to the dye, such as increased inflammation or corneal oedema. No residual staining of the iris or capsule is apparent by the following day.

Trypan blue creates a much darker staining and provides superior visualisation when compared with ICG. Unlike ICG, there is no particulate suspension with trypan blue, and it is much more convenient to use because there is no mixing involved. Because it is supplied in a smaller amount, it is less expensive. Finally, trypan blue staining lasts longer and usually persists throughout the entire phaco step. Without a red reflex, phaco of the nucleus is challenging even with a completed capsulorhexis because the capsule edge cannot be seen during sculpting or chopping. For this reason, dye-aided visualisation of the anterior capsule can decrease the risk of inadvertently cutting or tearing the capsulorhexis edge during these phaco manoeuvers. The more intense and persistent capsule staining provided by trypan blue dye is particularly advantageous in this regard.

Suresh Pandey, working in David Apple’s laboratory, has reported a comparison study of fluorescein, ICG, and trypan blue dye for anterior capsule staining in postmortem human eyes4. He found that trypan blue and ICG dye were superior to fluorescein for improving visualisation, with ICG being slightly better than trypan blue. However, unlike the surgical techniques described, his method was to inject the dye in the subcapsular space. Injecting dye through a capsule puncture into these overly hydrated lenses might result in an uncontrolled capsular rip. Supracapsular dye application is sufficient, and avoids this potential complication.

Conclusion :

ICG and trypan blue dye are extremely effective in providing anterior capsule visualisation with mature white or brown cataracts. In my experience, trypan blue dye produces a more conspicuous and persistent stain. Until trypan blue becomes available in the US, ICG provides an excellent alternative.

References:

1. Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the Lens Capsule for Circular Continuous Capsulorhexis in Eyes with White Cataract. Arch Ophthalmol 1998;116: 535-537.

2. Melles G, de Waard P, Pameyer J, Beekhuis,W. Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery. J Cataract Refract Surg 1999;25:7-9.

3. Fritz, W. Fluorescein blue light-assisted capsulorhexis for mature or hypermature cataract. J Cataract Refract Surg 1998;24:19-20.

4. Pandey SK, Werner L, Escobar-Gomez M, Roig-Melo EA, Apple DJ. Dye-enhanced cataract surgery. Part I. Anterior capsule staining for capsulorhexis in advanced/white cataracts: A comparative laboratory study using human eyes obtained post-mortem. J Cataract Refract Surg 2000 (in press).

 

ICG Dye Formulation : ICG dye (Akorn 800-535-7155) comes in a bottle containing 25 mg lyophilised ICG powder, with a second bottle of single use diluent. Add 0.5 ml of the diluent to the bottle to dissolve the ICG. Add 4.5 ml of BSS Plus (Alcon). Concentration will be 0.5%, and osmolarity = 270 mOsm. Use TB syringe and #30 cannula to stain the anterior capsule under an air bubble. Irrigate out air and dye prior to using viscoelastic. Sold as box of 6 (approx. US$330 (£206) or $55 (£34) each).

Trypan Blue Dye: DORC (1-800-75-DUTCH) not FDA approved at this time. This is available in Europe. Supplied as a premixed sterile solution. Technique same as for ICG. Sold as a box of 10 (approx. US$100 (£60) or $10 (£6) each).

David F Chang, University of California, San Francisco, and private practice in Los Altos, California, USA.

The author has no financial interest in any of the products mentioned.