Sir,

We read with interest the article by Slaughter and Lee1 on macular hole surgery with and without indocyanine green assistance. Pars plana vitrectomy followed by internal gas tamponade is the key operation in the treatment of macular hole. In addition, internal limiting membrane (ILM) peeling has been suggested to improve the success rate of macular hole surgeries.2 Indocyanine green (ICG) staining has been used to enhance the intraoperative visualization of the ILM.2 Yet, it is still unclear as to whether the use of ICG will affect the visual outcome of macular hole surgeries because of its potential toxicity.2, 3, 4 Slaughter and Lee have nicely addressed this important issue in their article. They have found no statistically significant difference in the mean postoperative visual acuity between two groups of patients who have undergone macular hole surgeries, one of which received ICG-assisted ILM peeling and the other received ILM peeling without ICG staining. However, we would like to discuss two important issues regarding this study.

Firstly, it has been shown in many in vitro studies that the toxicity of ICG to retinal cells is related to its concentration and duration of application.3, 5 Therefore, the concentrations and durations of ICG application may be crucial in causing different degrees of retinal toxicity and hence affecting the visual outcome in macular hole surgeries with ICG-assisted ILM peeling. These important parameters relating to the use of ICG have not been elaborated in the article, and we are keen to learn more about this key information.

Secondly, the postoperative visual acuity was used as one of the most important outcome measures in this study. Yet, visual acuity can be heavily affected by cataract and posterior capsular opacification, both of which are common conditions after pars plana vitrectomy and cataract extraction, respectively. The severities of these conditions in the studied cases, however, have not been discussed. We would therefore like to know whether the influence of cataract and posterior capsular opacification have been taken into account during the analysis of the postoperative visual acuity. Furthermore, LogMAR visual acuity would be a better option as compared to Snellen visual acuity since the latter is less precise especially in those patients with macular holes in whom the visions are usually poor.

While we commend Slaughter and Lee for their success in macular hole surgeries using ICG-assisted ILM peeling, we hope the above issues can broaden the discussion and deepen our understanding on how the use of ICG may affect the visual outcome of macular hole surgeries.