Keun Heung Park

Perfluoro-n-octane–assisted Single-layered Inverted Internal Limiting Membrane Flap Technique for Macular Hole Surgery

Vitrectomy became the standard treatment of macular hole after its introduction by Kelly and Wendel.1 Although progression of surgical techniques and diagnostic tools have improved the anatomical outcomes of macular hole surgery, postoperative visual recovery is usually limited.2–4 Furthermore, surg

Auxiliary role for d-alanylated wall teichoic acid in Toll-like receptor 2-mediated survival of Staphylococcus aureus in macrophages

We previously reported that Staphylococcus aureus avoids killing within macrophages by exploiting the action of Toll‐like receptor 2 (TLR2), which leads to the c‐Jun N‐terminal kinase (JNK)‐mediated inhibition of superoxide production. To search for bacterial components responsible for this event, a series of S. aureus mutants, in which the synthesis of the cell wall was interrupted, were screened for the level of JNK activation in macrophages. In addition to a mutant lacking the lipoproteins that have been suggested to act as a TLR2 ligand, two mutant strains were found to activate the phosphorylation of JNK to a lesser extent than the parental strain, and this defect was recovered by acquisition of the corresponding wild‐type genes. Macrophages that had phagocytosed the mutant strains produced more superoxide than those engulfing the parental strain, and the mutant bacteria were more efficiently killed in macrophages than the parent. The genes mutated, dltA and tagO, encoded proteins involved in the synthesis of d‐alanylated wall teichoic acid. Unlike a cell wall fraction rich in lipoproteins, d‐alanine‐bound wall teichoic acid purified from the parent strain by itself did not activate JNK phosphorylation in macrophages. These results suggest that the d‐alanylated wall teichoic acid of S. aureus modulates the cell wall milieu for lipoproteins so that they effectively serve as a ligand for TLR2.

Perfluoro-n-octane Assisted Free Internal Limiting Membrane Flap Technique for Recurrent Macular Hole.

Perfluoro-n-octane Assisted Free Internal Limiting Membrane Flap Technique for Recurrent Macular Hole Vitrectomy combined with removal of the internal limiting membrane (ILM) and gas tamponade is considered a standard procedure for macular hole. Hole closure is not sufficient for the recovery of vision but is necessary to ensure good visual acuity and prevent further vision loss. It is challenging to achieve hole closure in cases of chronic large macular holes or in highly myopic eyes. Recently, various surgical techniques using the ILM have been introduced to improve the surgical outcomes in such cases. The inverted ILM flap technique, first described by Michalewska et al, has shown improved functional and anatomical outcomes. Our group has reported a similar technique, whereby the macular hole is covered with a singlelayered ILM flap using perfluoro-n-octane (PFO) to stabilize the flap during fluid–air exchange. However, these procedures are not feasible in cases where the ILM around the macular hole has already been removed, such as cases of recurrent macular hole or failed surgery. Herein, the authors describe a modified technique for covering a recurrent macular hole with a free flap of the ILM with the assistance of PFO.

TOPOGRAPHIC CHANGES OF THE MACULA AFTER CLOSURE OF IDIOPATHIC MACULAR HOLE.

Purpose: To investigate retinal displacement in the macula after surgical closure of idiopathic macular hole and to identify factors correlated with displacement. Methods: This retrospective multicenter study included 73 eyes of 73 patients having idiopathic macular hole. A custom program was developed to compare the position of the retinal vessels in the macula between preoperative and postoperative photographs. En face images of a 6 mm × 6 mm optical coherence tomography volume scans were registered to calculate the scale. A grid comprising 16 sectors in 2 rings (inner; 2–4 mm and outer; 4–6 mm) was superimposed. The displacement of the retinal vessels was measured as a vector value by comparing the location of the retinal vessels in each sector. The correlation between displacement and various clinical parameters was analyzed. Results: The average displacement was 57.2 &mgr;m at an angle of −3.3° (nasal and slightly inferior). Displacement was larger in the inner ring (79.2 &mgr;m) than in the outer ring (35.3 &mgr;m, P < 0.001), and larger in the temporal sectors than in the corresponding nasal sectors (P ⩽ 0.008). Inferior and superior displacement was noted in the superior and inferior sectors, respectively. Multiple regression analysis revealed that basal horizontal macular hole diameter and size of internal limiting membrane removal were independent factors of displacement. Conclusion: The macula was displaced centripetally, nasally, and slightly inferiorly after surgical closure of idiopathic macular hole. Hole closure, contraction of the nerve fiber layer, and gravity are the suggested mechanisms of macular displacement caused by internal limiting membrane peeling.

Functional end-arterial circulation of the choroid assessed by using fat embolism and electric circuit simulation

The discrepancy in the choroidal circulation between anatomy and function has remained unsolved for several decades. Postmortem cast studies revealed extensive anastomotic channels, but angiographic studies indicated end-arterial circulation. We carried out experimental fat embolism in cats and electric circuit simulation. Perfusion defects were observed in two categories. In the scatter perfusion defects suggesting an embolism at the terminal arterioles, fluorescein dye filled the non-perfused lobule slowly from the adjacent perfused lobule. In the segmental perfusion defects suggesting occlusion of the posterior ciliary arteries, the hypofluorescent segment became perfused by spontaneous resolution of the embolism without subsequent smaller infarction. The angiographic findings could be simulated with an electric circuit. Although electric currents flowed to the disconnected lobule, the level was very low compared with that of the connected ones. The choroid appeared to be composed of multiple sectors with no anastomosis to other sectors, but to have its own anastomotic arterioles in each sector. Blood flows through the continuous choriocapillaris bed in an end-arterial nature functionally to follow a pressure gradient due to the drainage through the collector venule.

Vascular Displacement in Idiopathic Macular Hole after Single-layered Inverted Internal Limiting Membrane Flap Surgery

Purpose To compare vascular displacement in the macula after surgical closure of idiopathic macular hole (MH) after single-layered inverted internal limiting membrane (ILM) flap technique and conventional ILM removal. Methods This retrospective study included patients who underwent either vitrectomy and ILM removal only or vitrectomy with single-layered inverted ILM flap for idiopathic MH larger than 400 µm from 2012 to 2015. A customized program compared the positions of the retinal vessels in the macula between preoperative and postoperative photographs. En face images of 6 × 6 mm optical coherence tomography volume scans were registered to calculate the scale. Retinal vessel displacement was measured as a vector value by comparing its location in 16 sectors of a grid partitioned into eight sectors in two rings (inner, 2 to 4 mm; outer, 4 to 6 mm). The distance and angle of displacement were calculated as an average vector and were compared between the two groups for whole sectors, inner ring, outer ring, and for each sector. Results Twenty patients were included in the ILM flap group and 22 in the ILM removal group. There were no statistical differences between the groups for baseline characteristics. The average displacement in the ILM flap group and the ILM removal group was 56.6 µm at −3.4° and 64.9 µm at −2.7°, respectively, for the whole sectors (p = 0.900), 76.1 µm at −1.1° and 87.3 µm at −0.9° for the inner ring (p = 0.980), and 37.4 µm at −8.2° and 42.7 µm at −6.3° for the outer ring (p = 0.314). There was no statistical difference in the displacement of each of the sectors. Conclusions Postoperative topographic changes showed no significant differences between the ILM flap and the ILM removal group for idiopathic MH. The single-layered ILM flap technique did not appear to cause additional displacement of the retinal vessels in the macula.