Choroidal neovascularisation following inverted internal limiting membrane flap technique for idiopathic macular hole: a case for modified flaps

Abstract

A 70-year-old woman presented with sudden decrease of vision 2 months following a successful vitrectomy with inverted internal limiting membrane flap for a full thickness macular hole. Serial review of fundus pictures and optical coherence tomography scans revealed a focal retinal pigment epithelial disruption at the site of the macular hole after surgery and a choroidal neovascular membrane arising from the same. This report describes the possible role of the surgical technique in causation of the membrane and discusses modifications to avoid the same.

Background

Ever since its first description in 1991 by Kelly and Wendel,¹ vitrectomy has been the gold standard for surgical management of full thickness macular holes (FTMH). Introduction of internal limiting membrane (ILM) peeling by Eckardt et al² in 1997 further improved the anatomical success rates of this surgery. However, surgery for FTMH underwent a paradigm shift with introduction of the inverted ILM flap technique by Michalewska et al³ in 2010. They brought in the concept of proving a scaffold for tissue proliferation to help fill in the macular defect. This was followed by use of various other materials to stuff in the FTMH including human amniotic membrane, autologous lens capsule and autologous full thickness retinal grafts.^{4 5} Development of a choroidal neovascular membrane (CNVM) following macular hole surgery using the conventional approach of vitrectomy with ILM peeling has been reported in literature previously.^6–10 However, none of the cases reported to date underwent surgery using the inverted ILM flap technique. We describe our experience of managing a CNVM following inverted ILM flap technique for idiopathic FTMH with possible role of the technique in the causation of the CNVM and discuss modifications to the technique to avoid the same.

Case report

A 70-year-old woman presented with gradually progressive diminution of vision in her right eye (RE) over the last 6 months with sudden deterioration in the last 2 weeks. Left eye (LE) had undergone an uncomplicated cataract surgery 1 year ago. On examination, her uncorrected Snellen’s visual acuity in the RE was 20/630 and LE was 20/20. Intraocular pressures were 12 mm Hg in both eyes. Her best corrected visual acuity (BCVA) in RE was 20/125. Anterior segment of the RE showed a cataractous lens with nuclear sclerosis, while the LE had a well-centred intraocular lens in place. In the RE, an FTMH was observed on fundus examination and a stage 3 FTMH with a minimum hole diameter of 438 μm was confirmed on optical coherence tomography (OCT) (figure 1A). Fundus examination and OCT of the LE were unremarkable (figure 2A, B). She was taken up for a combined cataract surgery with intraocular lens implantation and 25-gauge pars plana vitrectomy using the Constellation vitrectomy system (Alcon Laboratories, Fort Worth, Texas, USA). After core vitrectomy, posterior vitreous detachment was induced and extended until the margin of the vitreous base. ILM was stained using 0.025% brilliant blue G dye (D.O.R.C. Dutch Ophthalmic Research Center, Zuidland, The Netherlands). ILM was peeled using the pinch-and-peel technique using a 25-gauge ILM forceps (Grieshaber, Alcon Laboratories, Fort Worth, Texas, USA). Multiple segments of ILM were peeled towards the hole margin and left attached to the edges of the hole. Consequently, the remnants of the ILM were trimmed using a vitreous cutter and massaged over the hole from all sides until the ILM became inverted as described previously.³ Sulphur hexafluoride 20% tamponade was given and the patient was advised face down positioning for 3–4 days.

Figure 1.

Colour fundus and optical coherence tomography (OCT) images of the patient at (A) presentation showing a full thickness macular hole (FTMH). (B) Three weeks following vitrectomy with inverted internal limiting membrane flap, the hole is closed but the fundus shows a small haemorrhage at the site of the FTHM with focal retinal pigment epithelium (RPE) disruption on OCT. (C) Six weeks after the procedure, haemorrhage resolves with improvement in foveal anatomy. (D) Two months after the procedure, fundus shows a choroidal neovascular membrane (CNVM) inferotemporal to the fovea arising from the focal RPE disruption (white arrow) at the site of the FTMH. (E) Three months after the surgery, the CNVM has grown extensively with haemorrhages all around and evidence of intraretinal fluid on OCT. (F) Resolved CNVM after three monthly injections of ranibizumab. BCVA, best corrected visual acuity.

Figure 2.

Fundus photograph (A) and optical coherence tomography scan (B) of the left eye showing a normal retinal examination. BCVA, best corrected visual acuity.

Three weeks after the procedure, the gas had completely absorbed and BCVA improved to 6/24. Examination revealed a small haemorrhage at site of the macular hole. This was at that time attributed to possible surgical trauma. The OCT documented type 1 closure of the macular hole with presence of the ILM flap with some disruption of the outer retinal layers (figure 1B). At the 6-week follow-up visit, BCVA improved to 6/18, haemorrhage resolved and the foveal contour improved on OCT (figure 1C). Two weeks later, the patient presented with sudden decrease in vision of 2 days’ duration. The BCVA had dropped to 20/200. The fundus showed a dull-white subretinal membrane inferotemporal to the fovea (figure 1D), which in retrospect was present on previous follow-ups also and appeared to be increasing in size. OCT demonstrated distortion of the foveal contour, presence of intraretinal fluid with a dip in the retinal pigment epithelium (RPE)—Bruch’s complex (figure 1D—white arrow). Suspecting a CNVM, the patient was advised OCT angiography (OCTA) and treatment with antivascular endothelial growth factor (anti-VEGF). However, the patient did not consent for the same at this point of time. She presented back a month later with further decrease in vision to 20/630. Fundus revealed a large CNVM associated with intraretinal haemorrhages over the macula (figure 1E). OCT and OCTA at this visit demonstrated intraretinal fluid and a florid network of vessels in the avascular retina slab, respectively (figure 3A). She was treated with three intravitreal injections of ranibizumab 0.5 mg/0.05 mL (Accentrix, Novartis India, Mumbai, India) administered at 1-month intervals.

Figure 3.

Optical coherence tomography angiography documenting the choroidal neovascular membrane regression at the site of the macular hole before (A) and after (B) treatment with three injections of ranibizumab. BCVA, best corrected visual acuity.

Outcome and follow-up

After 3 months, the haemorrhages resolved (figure 1F) and the patient’s vision improved modestly to 20/400. The OCT showed significant resolution of the intraretinal fluid and the network of vessels shrunk on OCTA (figure 3B). At final follow-up of 12 months, the patient was maintaining a BCVA of 20/400 with a crenated CNVM on OCTA and did not require any more intravitreal anti-VEGF injections.

Discussion

This case demonstrates the possibility of iatrogenic trauma leading to the development of a CNVM following inverted ILM flap technique for a large FTMH. The act of ‘massaging’ the trimmed ILM flaps over the hole to invert the ILM, as suggested in the original technique, likely led to iatrogenic RPE injury (figure 1D). A review of the surgical video did not reveal any other step that could have resulted in inadvertent iatrogenic retina trauma. The initial improvement in visual acuity probably led to a delay in detection of the CNVM which was in retrospect present at the 3-week follow-up visit also. The patient responded to treatment with anti-VEGF and had no recurrence following three monthly injections. Given this was a one-time insult due to the surgical trauma, such a response was expected.¹⁰

Although the technique of ILM peeling and inversion has increased the chances of successful FTMH closure, the increased risk of iatrogenic trauma to retinal tissue remains.³ Various complications such as focal retinal haemorrhages, retinal oedema, paracentral scotomas, dissociated optic nerve fibre layer, focal RPE alterations and iatrogenic para-macular retinal tears have been reported following ILM peeling.¹¹ All these complications, including CNVM formation from iatrogenic RPE disruption, are caused due to direct/indirect surgical trauma. Limiting the surgical manoeuvres during ILM peeling and inversion is prudent to minimalise chances of iatrogenic retinal injury.

Modified ILM flaps are a step in this direction. They work on the principle of limited ILM peeling followed by inversion of the complete flap of ILM over the FTMH, instead of trimming the flap and massaging the smaller remnants over the hole. Michalewska et al, the original authors of the inverted ILM flap technique, proposed a temporal inverted ILM flap and compared it with the conventional inverted ILM flap.¹² They found similar results with lesser surgical trauma. These results have been substantiated with other authors using modified temporal and superior ILM flaps to close the FTMH.^{13 14}

CNVM has been reported previously after vitrectomy for FTMH.^6–10 However, there are no reports following inverted ILM flap technique for the same. The cause here being a possible iatrogenic trauma, there are high chances of under-reporting as well. We wish to report the same, as the case highlights an important complication of this technique and possible modifications to avoid the same. With increasing evidence that modified single-layered flaps may be as effective as conventional multilayered inverted flaps along with the reduced risk of causing iatrogenic retinal injury, we advocate the former technique for large FTMH closure.

Learning points.

• Choroidal neovascular membrane can form following surgery for macular hole.

• Iatrogenic trauma during internal limiting membrane (ILM) peeling and inversion may have a causative role in the same.

• Inverted ILM peel technique with multiple flaps being inverted and massaged over the hole may have higher chances of iatrogenic trauma to the underlying retinal pigment epithelium.

• Modified inverted flaps with single large flap being inverted over the hole may help in reducing the chances of this iatrogenic insult.