Ranibizumab is a monoclonal antibody fragment that inhibits angiogenesis by inhibiting vascular endothelial growth factor A, used as a treatment for patients with wet aged-related macular degeneration (ARMD). Adverse effects from intravitreal Ranibizumab injections are well recognised [1-3]. Macular hole formation following Ranibizumab injection is a complication that has been recently reported in few case reports. We present a larger case series of five patients, who developed full thickness macular holes (FTMH) after intravitreal Ranibizumab injections for treatment of wet ARMD that we were aware of between 2009 and 2013.

Deterioration of central vision following intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections for ARMD, especially in the presence of PED may be commonly due to new macular haemorrhage or retinal pigment epithelial rip. FTMH formation until now has been reported in a few isolated cases [4-8].

The mechanism of idiopathic FTMH formation was hypothesized by Gass as a result of contraction of the prefoveal vitreous cortex, causing focal tangential traction on fovea [9]. Gaudric et al. in an optical coherence tomography (OCT) study concluded that vitreous traction may be oblique [10]. Therefore, both tangential and anterior-posterior transvitreal traction has been implicated in the development of idiopathic FTMH.

Posterior vitreous detachment (PVD) in recent years has been closely speculated to have a potential significant role in the development of FTMH following intravitreal injections. Geck et al. observed a 25% PVD rate after intravitreal injections within a mean follow-up period of 11 weeks and incidence correlates with increasing age [11]. Querques et al. suggested that intravitreal anti-VEGF might induce vitreous incarceration causing vitreoretinal traction. Contraction of the CNVM may impose forces on the retinal pigment epithelium and the retinal surface resulting in macular hole formation [4]. Chemical compounds applied to the vitreous cavity is also suggested to modify the structure of the vitreous gel, leading to incomplete PVD and traction causing a macular hole [5]. Grigoropoulos et al. hypothesized that intravitreal injections can increase the traction on the fovea by causing vitreous syneresis, globe deformation during needle insertion, and vitreous incarceration at the insertion site. Incomplete PVD, which may be induced by the intravitreal injections may create focal sites of traction on the retinal surface and in the presence of pre-existing VMA, this may increase the chances of FTMH [6]. Our cases support this latter theory as 3 out of 5 cases have evidence of pre-existing focal VMT or incomplete PVD before the first injection (VMT grading was based on OCT classification [12]).

In a case report by Cho et al. of FTMH formation after intravitreal Ranibizumab injection for IPCV, the patient underwent prompt macular hole surgery followed by two Ranibizumab injections achieving good result of 6/18 in that eye [7]. In our series of 5 patients, three had existing PED. The significant number of PED could be attributed to the fact that PED has a recognized risk to tear from tangential stress in the detached tissues. It is possible that subfoveal PED causes elevation of the foveal retina and stretching of the photoreceptor layer by physical forces and thereby affecting the structural support of the fovea. This makes it more susceptible to vitreofoveal tractional forces, which can initiate a neurosensory retinal detachment and ultimately a FTMH [13]. Dynamic changes of flattening and recurrent distension of PED following injections could also possibly exacerbate the already unstable adhesion of vitreous and neuroretinal interface also rendering the PED more susceptible to macular hole formation. Oshima et al. reported a FTMH case following initial PED rip based on same theory but emphasized on perhaps the rapid contraction of retinal pigment epithelium as the exacerbating factor [8].

In summary, it is important for clinicians to be aware, that patients receiving intravitreal injections are at a small risk of developing complication such as a FTMH which is often unrecognised or under reported. The risk may perhaps be higher when treating CNVM in the presence of pre-existing PED and or VMT. Based on our case series, both PED and VMT may be an important pre-existing contributory factor for FTMH separately or as a combined factor. Early recognition of this adverse effect and prompt consideration for vitreoretinal surgery may improve visual prognosis. With the recent introduction of Ocriplasmin [14] early recognition of VMT in particular, may also benefit from the challenging concept of treating any pre-existing VMT before intravitreal injection, to reduce the risk of FTMH.