Staining the anterior capsule

Abstract

In their article about indocyanine green staining in a traumatic cataract,1 Newsom and Oetting report a case of a 50-year-old patient with white traumatic cataract associated with a tear in the anterior capsule. Indocyanine green (ICG 0.5%) was injected under an air bubble to stain the torn anterior capsule, thus enhancing its visualization during the anterior capsulotomy procedure. The anterior capsule stained green, but the cortical material exposed to ICG did not stain. According to the authors, ICG seems to have selective affinity for the anterior capsule over cortical lens material. Staining an intact anterior capsule with nontoxic capsular dyes is currently used by many cataract surgeons for performing anterior capsulorhexis in cases of advanced/white cataract. Fluorescein sodium (2%) was the first dye advocated for this use by Hoffer and McFarland in 19932; ICG (0.5%) was further recommended for anterior capsule staining by Horiguchi and coauthors in 1998.3 Melles and coauthors4 recently introduced the use of trypan blue (0.1%) for this purpose. We extensively studied the use of these 3 nontoxic capsular dyes to learn and perform anterior capsulorhexis and other critical steps of phacoemulsification in a laboratory setting using a total of 28 human eyes obtained postmortem (S.K. Pandey, MD, et al., “Anterior Capsule Staining in Advanced Cataracts: A Laboratory Study using Postmortem Human Eyes,” presented at the annual meeting of the American Academy of Ophthalmology, Orlando, Florida, USA, October 1999; S.K. Pandey, MD, et al., “Dye-Enhanced Cataract Surgery in Human Eyes Obtained Post-mortem: A Laboratory Study to Learn and Perform Critical Steps of Phacoemulsification,” video presented at the XVIIth Congress of the European Society of Cataract & Refractive Surgeons, Vienna, Austria, September 1999). We performed an anterior capsulorhexis in experimental closed-system surgery in 12 postmortem human eyes with advanced cataracts after staining the anterior capsule with fluorescein sodium, ICG, and trypan blue.5 We also compared the 2 commonly used methods: staining under an air bubble and intracameral subcapsular injection. The anterior surface of the anterior lens capsule was stained after injection of the dye under an air bubble. After intracameral subcapsular injection, all 3 dyes were trapped in the central and midperipheral subcapsular space; both the posterior surface of the anterior lens capsule and the subcapsular cortex stained after using this technique. However, we were able to distinguish the anterior lens capsule from the superficial subcapsular lens cortex by a different pattern of staining (smooth staining of the capsule and feathery staining of cortex). We have also demonstrated the use of capsular dyes (ICG 0.5% and trypan blue 0.1%) to enhance visualization to learn and perform other critical steps of the phacoemulsification procedure, including posterior capsulorhexis.6,7 Staining the capsular bag enhances its visualization and the surgeon can distinguish feathery, irregular staining of residual subcapsular cortex from smooth staining of the anterior, equatorial, and posterior capsule (Figure 1). Thus, the staining facilitates cleaning of residual cortical matter from the capsular bag. Posterior capsule staining can also be useful in learning and performing the posterior capsulorhexis procedure.7Figure 1.: (Pandey) Gross photographs of 2 postmortem human eyes after dye-enhanced cataract surgery was performed. Note the staining of the capsular bag with ICG (A) and trypan blue (B). The arrows demonstrate the staining of the residual cortical material in both cases.As per our experience on postmortem eyes with advanced cataract, the subcapsular cortex and residual cortical material can be stained with capsular dyes (ICG and trypan blue). The lens cortical staining pattern may be different (feathery, irregular, and fainter) from that of anterior capsule staining (smooth, regular). This is in contrast to the case of white traumatic cataract reported by Newsom and Oetting, in which injection of ICG under an air bubble selectively stained the anterior lens capsule but cortical material exposed to ICG did not stain.1 Although the reason for this was not explained, the authors presumed that ICG has a selective affinity for the anterior capsule over lens cortical material. We assume that this may vary with the technique (injection under an air bubble or intracameral subcapsular injection) used for staining, the concentration and type of capsular dye used to stain the anterior capsule, and possibly the cataract type (white/nonwhite). Additionally, the interval between staining and surgery may influence the degree and pattern of staining. The results of our studies of dye-enhanced cataract surgery should be interpreted carefully since postmortem changes in the aqueous humor and human crystalline lens possibly influence the affinity as well as the degree and staining pattern of the anterior capsule and other structures of the capsular bag. Further studies with more cases are needed to reach definitive conclusions concerning the staining of the lens cortex. Suresh K Pandey MD Liliana Werner MD, PhD David J Apple MD aCharleston, South Carolina, USA