Anterior Vitreous Biostaining in Pediatric Cataract Surgery

Suqin Guo, MD · Arthur C. Tutela, MD · Rudolph Wagner, MD · Anthony Caputo, MD

This research is funded by The Eye Institute of New Jersey.

Introduction

Congenital cataract is one of the common ocular disorders responsible for causing blindness in children when not surgically removed promptly or properly.^1,2 Congenital cataract removal may result in posterior capsular opacification (PCO), which may also produce amblyopia (blindness).^3,4

Because of the characteristics of children's eyes, a primary anterior vitrectomy is a critical surgical step to avoid PCO.^3,4 However, the vitreous is transparent and difficult to visualize in the anterior chamber during cataract surgery. Any vitreous remaining in the anterior chamber can incarcerate surgical wounds and cause tractional retinal detachment or endophthalmitis.

Highlighting the vitreous during the surgery will facilitate a thorough vitrectomy to ensure an anterior chamber free from vitreous and to eliminate subsequent complications.

Our goal is to improve the visualization of vitreous during anterior vitrectomy for pediatric cataracts. We have evaluated four biostains for their ability to selectively stain and highlight the vitreous and ensure a clean anterior vitrectomy.

Materials and Methods

We performed open sky and closed eye vitreous staining on human cadaver eyes and monkey cadaver eyes. Open sky vitreous staining involved dissection of the cornea and lens under a surgical microscope and injecting the anterior vitreous with the selected biodyes.

Closed eye staining required leaving the corneas intact and subluxating the lens into the posterior chamber to expose anterior vitreous. We injected the biodyes to stain the vitreous exposed to the anterior chamber. The stained vitreous was examined under a surgical microscope and digitally recorded for comparison.

The four stains and concentrations were triamcinolone acetonide (Kenalog, Bristol-Myers Squibb) 10mg/mL, indocyanine green (ICG) 0.125%, fluorescein 10%, and trypan blue 0.1%.

After open sky lensectomy or closed eye lens subluxation, the anterior vitreous was stained by injecting 0.1 mL to 0.2 mL of ICG, Kenalog, fluorescein, or trypan blue of above concentration respectively. The subsequent staining of each biodye was recorded with digital photographs.

Results

Slide 1

All four biostains produced acceptable vitreous staining while staining other surrounding ocular structures. Kenalog best differentiated vitreous from other ocular structures (Slide 1).

Kenalog is a precipitate of white particles held in solution that became trapped in the vitreous gel. As the Kenalog solution is not a true stain but a suspension, it did not highlight surrounding ocular tissues in the anterior chamber as the other biostains did.

Slide 2

The other biodyes stained vitreous as well. However, they also stained surrounding ocular tissues, making it difficult to discriminate between vitreous and other intraocular structures (Slide 2).

Discussion

The biostains that were used in our study for better visualization of anterior vitreous have documented uses in other ophthalmologic procedures. It is important to consider the clinical significance as well as the safety of these biodyes.

Triamcinolone acetonide (Kenalog) is a water insoluble cortical steroid⁵ that inhibits inflammation and has been used intraocularly as a potent anti-inflammatory agent for various ocular diseases such as diabetic macular edema, cystoid macular edema, central vein occlusion, macular degeneration, and subretinal neovascularization.^6-10

The safety of an intravitreal injection of triamcinolone acetonide has been evaluated in an animal model.¹¹ Researchers did not find differences in slit-lamp examination, ophthalmoscopy, electroretinography, and intraocular pressure (IOP). However, researchers concluded that the preservative benzyl alcohol in Kenalog has been implicated in fetal toxic syndromes when used in intravenous medications.

Nevertheless, the preservative can be removed as was described by Burk and colleagues.⁵ In this study, the preservative-containing vehicle of Kenalog was exchanged for balanced salt solution before being introduced into the anterior chamber for staining of anterior vitreous.⁵

Intravitreal Kenalog is considered safe to use in human eyes. It has shown efficacy in reducing macular edema associated with uveitis and diabetic retinopathy as well as improving subfoveal choroidal neovascularization secondary to age-related macular degeneration.6-8 Complications reported in these studies included elevated IOP and lenticular opacity.10-11 Other rare and assumed complications of Kenalog include retinal detachment, endophthalmitis, choroidal, and vitreous hemorrhage from injection sites. ^6-11

In our experiment, the amount of Kenalog (0.1 mg/0.1 mL) used to visualize vitreous strands was twenty times less concentrated than that reported to treat retinal diseases. The stained vitreous is consequently removed as trapped particles, thereby significantly decreasing the possibility of IOP elevation.

Because the result of cataract surgery is lens removal, Kenalog-induced cataract is not a concern. Kenalog is introduced into the anterior chamber via surgical wound during cataract surgery so that the injection site vitreous hemorrhage and retinal tears are less of a concern.

ICG is a commonly used intravenous dye for retinal imaging. Many studies indicate that ICG has a long history of safety and little toxicity.12,13 ICG has also been reported being injected into the vitreous for the visualization of the internal limiting membrane (ILM) in macular hole surgery¹⁴ with minimal damage to the retina and no intraoperative or postoperative complications.¹⁴

Conversely, atrophic changes in the retinal pigment epithelium (RPE) over the base of macular holes has been reported.¹⁵ It is suggested that the RPE atrophic changes may be related to a high concentration of ICG solution and light toxicity.¹⁵ ICG anterior lens capsule staining has been used safely to facilitate performance of the circular continuous capsulorrhexis in pediatric and adult mature cataract surgery.^16,17

Trypan blue has been reported to be carcinogenic in concentrations of 100 mg/kg and 300 mg/kg.¹⁸ Retinal toxicity from high concentration of trypan blue, such as abnormal photoreceptors and increased proliferative activity in Muller cells¹⁹ has been reported. It is suggested that if and when trypan blue is used, lower concentrations are obligatory.¹⁹

Trypan blue has been used to facilitate anterior capsulorrhexis in the absence of a red fundus reflex during cataract surgery.²⁰ Trypan blue has been shown to stain acrylic IOLs despite a short exposure time.²⁰ Trypan blue (0.06%) has been used successfully to stain epiretinal membranes during surgery for proliferative vitreoretinopathy without signs of toxicity or adverse reaction.²¹

Fluorescein, like ICG, is commonly used intravenously for retinal imaging. It has been shown to be safe for ophthalmologic use such as for angiography of the retina and uveal tract. Allergic reactions can occur with administration of fluorescein and must be considered when used intraocularly.²²

Fluorescein was the first dye advocated for staining and visualization of the anterior capsule in white cataract surgery.^16,22,23 Corneal edema has been reported with fluorescein capsular staining. It was suggested that due to a low molecular weight of fluorescein sodium, the cornea is stained and fluorescein migrates to the vitreous cavity easily.²³

Conclusion

We studied the value of vitreous biostains for enhancing visualization of the vitreous and ensuring a clean anterior vitrectomy to improve the outcome of pediatric cataract surgery. Our results suggest:

• Biostains are useful for enhancing visualization of the vitreous, thus potentially improving the outcome of anterior vitrectomy during pediatric cataract surgery.
• All four biostains studied produced acceptable vitreous staining, while also staining surrounding ocular structures. Triamcinolone, however, best differentiated the vitreous.

References

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The authors thank Dr. Kathryn Pokorny for her invaluable help in editing the manuscript.