Macula Function improves after surgery using brilliant blue G dye for ILM staining: IJO
Surgical techniques for macular holes (MHs) have evolved over the last decade, and today, MHs have the best success rates of any retinal surgical condition. MH surgery involves small gauge vitrectomy with internal limiting membrane (ILM) peeling.
Brilliant blue G (BBG) is one of the frontrunners among the currently available dyes used for the staining of the ILM during vitrectomy for several macular pathologies. BBG dye has been used as an alternative to indocyanine green which has been shown to be toxic to retina, and different formulations of BBG dye with polyethylene glycol, trypan blue, etc., are commercially available.
Heavy BBG (hBBG) is isotonic and directly sediments on the posterior pole without dispersing in the vitreous cavity. Moreover, less dye is needed in terms of both volume and concentration. It also obviates the need for a fluid air exchange (FAE) as required for trypan blue, since the staining effect is almost instantaneous. In this study, authors Kannan NB, Chakrabarti A, Sen S, Rajan RP, Kumar K, Baliga G, et al attempted to analyze the functional improvement in patients undergoing MH surgery with hBBG‑assisted ILM peeling, to evaluate the safety profile of hBBG in macular surgeries.
Forty‑four eyes with idiopathic MH were randomized into two groups – 24 eyes undergoing vitrectomy with ILM peeling using hBBG staining and 20 eyes without staining; anatomical and functional status (with microperimetry (MP)) at baseline and during postoperative follow‑up were noted and compared.
All eyes had closure of MH postoperatively and overall baseline MP indices (average threshold, AT; foveal sensitivity, FS) improved significantly at 6 weeks and 6 months of follow‑up.
AT and FS showed significant improvement at 6 weeks and 6 months from baseline in both individual groups (P < 0.001).
Intergroup comparison showed that there was no statistically significant difference in AT and FS values at any point of time (baseline, 6 weeks, 6 months) between staining and no‑stain group.
No eyes in the cohort had any unexplained visual loss.
ILM peeling for MHs was first started after Gass's theory on MH pathogenesis. ILM contributes to 50% of retinal rigidity and may also lead to tangential due to the presence of contractile cells on inner surface of ILM. Hence, ILM peeling relieves this tangential traction and also prevents glial tissue‑induced epiretinal membrane formation and MH reopening postoperatively. However, proper and meticulous peeling of ILM is difficult due to its thin and transparent structure. Several dyes have been introduced to stain the ILM to aid in its peeling; however there is always a concern of injury to the neurosensory retina due to direct toxicity of the dye or due to dye‑mediated phototoxicity.
Technically, ILM peeling without staining is much more challenging than dye‑assisted peeling, since the ILM gets stained far better with the dye and this provides for better visualization of ILM and contrast during peeling and may reduce chances of mechanical trauma to the retina and risk of bleeding.
Triamcinolone acetonide although does not particularly stain the ILM, ILM peeling with TA without staining has been proven to be safe and effective in MH surgeries. Previously, MHs in which ILM peeling was done assisted with TA have shown significant improvement in microperimetric indices postoperatively.
Visual acuity assessment may be a basic requirement for foveal functional evaluation; however, it may underestimate the subclinical foveal functional changes in MH surgery patients. In this regard, MP can help determination of point to point retinal sensitivity and provides specific functional information of the macula and visual restoration after hole surgery.
After postoperative closure of the MH, the fixation status of eyes may show a complex reorganization, and fixation may become more stable with follow‑up. Fixation stability is an important functional parameter in MH patients. In this study, authors observed a similar trend toward recovery of fixation stability postsurgery till the final follow‑up.
"To summarize, improvements in functional parameters were similar in both staining and no staining group till the 6 months follow‑up period. The use of hBBG may obviate the need for FAE, thereby avoiding annoying residual bubbles and saving time. The hBBG technique for staining may also be evaluated in the future for patients with MH and retinal detachments or even in patients with long‑standing macular detachments."
Source: Kannan NB, Chakrabarti A, Sen S, Rajan RP, Kumar K, Baliga G, et al. Evaluation of retinal functional changes after macular hole surgery using heavy brilliant blue G dye for internal limiting membrane staining: A prospective, single blind, randomized controlled trial. Indian J Ophthalmol 2021;69:2752-6.