Giant internal limiting membrane (ILM) tears—defined as a dehiscence of the ILM sufficiently large to result in an elevated and scrolled ILM edge—are often encountered in patients with ERMs. Despite this, the tears frequently go unrecognized and are seldom reported in the literature, said Mark W. Johnson, MD.
To further investigate this finding, Dr. Johnson and his colleagues conducted a study of giant ILM tears. In his presentation on Friday during Retina Subspecialty Day, he described the morphologic characteristics and associated features of the tears.
Prevalence and characteristics. In this retrospective study, 71 eyes that underwent vitrectomy with membrane peel for an ERM at the University of Michigan from 2016 to 2019 were evaluated.
Giant ILM tears were found in 23 (32.4%) of the 71 eyes. The average length of the torn ILM edge was 5.57 (± 0.43) mm. High myopia was seen in six eyes with and in four eyes without the tears (26.1% and 8.3%, respectively). No other significant differences emerged with regard to evaluated characteristics, including pre- and postoperative visual acuity, macular thickness, and presence of posterior vitreous detachment, Dr. Johnson said.
Pre-op OCT is key. The use of radial OCT scans increased the preoperative detection rate, Dr. Johnson said. “We found that giant ILM tears tended to be present in the perifoveal zone of the macula”—and as a result, they could be missed by conventional horizontal or vertical seven-line scans. All told, 17 of the 23 tears (73.9%) were found using seven-line rasters, and 22 of the 23 (95.6%) were found using radial scans. The remaining tear was identified during surgery.
In keeping with previous reports, Dr. Johnson and his colleagues found that retinal nerve fiber layer (RNFL) schisis was common in eyes with giant ILM tears. “Often, there was a diffuse area of RNFL schisis adjacent to a giant tear, which we think represents the area of greatest traction exerted by the ERM.” Other features included inner retinal dimpling within ILM dehiscence and two types of paravascular red lesions (intraretinal cavitations and inner lamellar retinal defects).
Underlying pathogenesis. The primary underlying mechanism appears to be progressive ERM contracture, Dr. Johnson said. It’s also possible that, in some eyes, vitreoretinal traction along retinal vessels may play a role in initiating the tear.
Surgical notes. The use of brilliant blue G dye (TissueBlue) aided in confirming suspected ILM tears, Dr. Johnson noted. Finally, he said, in all cases, the scrolled edge of the tear was used as a convenient and safe “handle” to initiate peeling of the ILM and overlying ERM. “Surgeons who do not routinely peel ILM at the time of ERM removal may consider doing so when giant ILM tears are present,” he added. —Jean Shaw
Financial disclosures: Dr. Johnson: Amgen: C; Apellis: S; Aura Biosciences: C; Pfizer: C.
Disclosure key. C = Consultant/Advisor; E = Employee; L = Lecture Fees; O = Equity Owner; P = Patents/Royalty; S = Grant Support.