a combination of tangential and antero - posterior traction has been postulated in the pathogenesis of macular hole ( mh ) formation resulting from vitreomacular traction ( vmt ) . usa ) can relieve antero - posterior traction and results in mh closure in 40% of cases . however , removal of tangential forces by internal limiting membrane ( ilm ) peeling has also been shown to improve mh closure after vitrectomy . the balance of these forces is well - illustrated in the case that we present here , where intraoperative optical coherence tomography ( ioct ) during vitrectomy for an eye with vmt revealed a small retinal defect that rapidly enlarged to a large full - thickness mh over 1 week . the mh remained open after treatment with gas tamponade alone , but closed after the ilm peeling was performed . her history included high myopia and pseudophakia in both eyes and prior laser retinopexy for a retinal tear in the affected eye . on examination , va was 20/30 in the right eye and 20/50 in the left eye . pupils were normal with no relative afferent pupillary defect and the intraocular pressures were normal . anterior segments were normal in both eyes , and dilated fundus examination was normal in the right eye . spectral domain oct ( sd - oct ; heidelberg spectralis ) demonstrated vmt with an inner lamellar hole ( fig . the patient desired treatment for her worsening vision and metamorphopsia , and surgical repair was recommended . a 25-gauge pars plana vitrectomy was performed , and the adherent posterior hyaloid required use of intravitreal triamcinolone and an illuminated pick to carefully induce a posterior vitreous detachment . ioct imaging ( zeiss rescan 700 ) demonstrated successful release of the vmt from the posterior pole ( fig . 2a , b ) , and no ilm peeling or gas tamponade was performed . on the first postoperative day , va was 20/60 , but it decreased to 20/200 at 1 week . a full - thickness mh of approximately 500 m in diameter was noted ( fig . the patient underwent in - office fluid - gas exchange with 16% c3f8 , followed by face - down positioning . one week later , her va had not improved and the mh remained open ( fig . she then underwent 25-gauge vitrectomy with ilm peeling and 20% sf6 gas , following which the mh closed ( fig . 1d ) . a closer retrospective review of the ioct scans obtained during her first surgery revealed an occult full - thickness mh after lifting the posterior hyaloid ( fig . the retinal defect was only seen in a single scan from numerous scans of the macular region , and was not noticed during the surgery . mh formation is an uncommon complication of vitrectomy surgery for vmt , but its occurrence may recapitulate the mechanism by which spontaneous vmt release can lead to idiopathic mh formation . here , ioct imaging showed a small retinal defect during surgery that rapidly enlarged to a 500-m mh over 1 week , which could only be closed subsequently with ilm peeling , suggesting that significant tangential traction from the ilm was present . we postulate that this tangential traction was unmasked after the antero - posterior traction and centripetal forces were relieved from vmt release in the initial surgery , and the tangential forces were left unopposed to cause the large mh . this case supports the important role of the ilm in the pathophysiology of mhs , and that ilm peeling may not just be a surrogate for removing vitreous cortex remnants at the macula which may contract and induce mh formation or prevent hole closure   here , ioct imaging showed no evidence of residual vitreous , and mh closure was only achieved after ilm removal . importantly , this case also demonstrates the strengths and weaknesses of current intrasurgical imaging technologies . ioct may reveal subclinical changes that impact surgical decision - making   as well as changes in the retinal architecture caused by the surgical instrumentation . however , cursory intraoperative review of these images and the limited quality of heads - up display projections may also lead to a false sense of security if subtle changes are overlooked . hence , while ioct is a useful emerging adjunct for vitreoretinal surgery , clinical judgment remains paramount .
we report the case of a 69-year - old patient who underwent vitrectomy for vitreomacular traction ( vmt ) and developed a postoperative macular hole that was observed 1 week after surgery . the hole did not close by in - office fluid - gas exchange alone , but was achieved after repeat surgery with internal limiting membrane ( ilm ) peeling . 
 intraoperative oct ( ioct ) images from the first surgery revealed an occult macular hole that formed after vmt release . 
 we discuss how ioct findings provide insight into the role of the ilm in macular hole formation and emphasize the importance of carefully inspecting ioct images in real time to avoid missing small but important findings .