16.2 Macular Hole Repair

Jason Chan, Timothy Lai, Adrian Fung

Full Thickness Macular Hole

Full thickness macular holes (FTMH) refer to complete defects of the neurosensory retina down to the retinal pigment epithelium (RPE) at the fovea. Patients can present with blurred vision, central scotoma and/or metamorphopsia. Macular holes can be idiopathic or secondary to myopic traction maculopathy, trauma, cystoid macular edema, solar retinopathy, retinal detachment, laser, proliferative vitreoretinopathy (PVR), macular telangiectasia type II or Alport Syndrome. Idiopathic macular holes are more frequent in females (3.3:1) and are bilateral in approximately 12% of patients.[1]

Classifications

There are two main classifications for macular holes. Gass firstly described the evolution of macular holes based on the biomicroscopic feature[2,3] but this classification has largely been replaced by the International Vitreomacular Traction Study (IVTS) group which introduced an anatomic classification for diseases of the vitreomacular interface based on OCT findings in 2013.[4]

Vitreomacular adhesion (VMA): vitreous adhering to central macula without retinal morphologic changes and the attachment is within a 3 mm radius of the fovea
Vitreomacular traction (VMT): vitreous adhering to the central macula with anatomic changes shown by OCT, no full thickness tissue dehiscence
Full Thickness Macular Hole:
- Small: ≤ 250 μm
- Medium: > 250 μm and ≤ 400 μm
- Large: > 400 μm
- With or without vitreomacular traction

Management

Approximately 50% of “stage 1” impending macular holes regress spontaneously.[5] About 11.5% of stage 2 FTMH close spontaneously in one year, while only 4% of stage 3 or 4 FTMH close spontaneously.[6,7] For symptomatic stage 2-4 FTMH, vitrectomy and membrane peeling is indicated as most of the macular holes will close following surgery. After successful closure of macular hole, visual acuity is generally improved unless there is irreversible photoreceptor or RPE damage associated with chronic macular hole.[7]

1. Pars Plana Vitrectomy (PPV)

Using microincisional vitrectomy system, transconjunctival PPV (23-, 25- or 27-gauge) can be performed with small sclerotomy wounds which can be self-sealing. The vitreous core should be first removed by the vitreous cutter. Peripheral vitrectomy can be performed after posterior vitreous detachment (PVD) induction.

2. Induction of Posterior Vitreous Detachment

Following core vitrectomy, the posterior hyaloid is aspirated and lifted off the optic disc by using aspiration of the vitrectomy probe. In difficult cases or if there is uncertainty if a PVD is present, intravitreal stains can be used. Although intravitreal triamcinolone acetonide stains vitreous the most clearly, since an internal limiting membrane dye (e.g. Brilliant Blue G or Indocyanin Green) is often required for later membrane peeling, it can be used to stain the vitreous too. Further details regarding PVD induction can be found in Chapter 4 Posterior Vitreous Detachment Induction.

3. Stain the Internal Limiting Membrane (ILM)

ILM is difficult to visualize but vital dyes can help to highlight it. Vital dye-assisted ILM peeling can facilitate macular hole closure when compared to vitrectomy alone.[8] Various types of vital dyes are described in Chapter 6 Membrane Stains.

Dilute (e.g. 10%) triamcinolone acetonide
1. Deposits in the vitreous and the posterior hyaloid
2. May also be useful in treating cystoid macular edema
Trypan blue
1. Stains epiretinal membrane (ERM) but barely stains ILM[9]
2. Potentially toxic to retinal pigment epithelium[10] and may cause cystoid macular edema[11]
Brilliant Blue G (BBG)
1. Stains ILM more than trypan blue
2. Less retinotoxic and has no apparent effects on visual acuity[12]
3. Safer than trypan blue and ICG
Indocyanine green (ICG)
1. Best staining effect on ILM
2. Dose-dependent toxic effect on the retina (including retina ganglion cells and retinal pigment epithelial cells) which may result in visual field defects[13]
Infracyanine green
1. Less retinotoxic than ICG due to the absence of hypo-osmolarity[14]

NOTE

BBG / ICG only stains ILM but not ERM; hence a “negative stain” is seen where ERM is present

Before the injection of the dye, all air bubbles in the syringe should be carefully expelled. If not using a dual bore canula, the infusion can be clamped prior to dye injection into the vitreous cavity to prevent flow from the infusion line blowing the dye off the macula. This is usually unnecessary with new vitrectomy systems and valved cannulae. Some dyes contain a 4% PEG solution that allow them to sink directly onto the macula.[15] Dyes without this may sometimes diffuse throughout the globe, obscuring the intraoperative view of the fundus. Another method to stain the membrane (with better visualization of the retina maintained during the removal of the dye) is to perform partial fluid-air exchange until the level of BSS® is just above the retinal surface before injection of the dye (Figure 16.2.1). After approximately 30 seconds of staining, fluid is infused and is aspirated simultaneously with the dye in the vitreous cavity. Of note, staining under air may increase the relative concentration of the dye and the stain with a potentiald increased risk of retino-toxicity.

4. Membrane Peeling

Use a high magnification lens: contact flat lens on the cornea, 90D/high-resolution Oculus BIOM® lens or green Zeiss Resight® lens
Slowly insert the membrane forceps designed for ILM peeling (e.g. ILM, asymmetrical or end-grasping forceps) into the anterior vitreous. For the beginners, extra care must be taken to avoid traumatic contact with the crystalline lens or retina
Adjust the field of view, magnification and focus until the macula is well visualized. Novice surgeons have a tendency to increase magnification but remember this reduces both the depth of field and field of view. Operate at the lowest magnification that allows for safe ILM peeling
Start the ILM peeling at approximately one-third distance between the fovea and the retinal vessel arcades. Select a retinal area that the instrument naturally approaches- this may depend on the positioning of the cannulae, speculum and patient’s nose. Starting too close the fovea risks damaging this vital structure, starting too far away makes it more difficult to start the peel (as the ILM is more adherent peripherally). If possible, avoid starting within the papillo-macular bundle or over retinal vessels (Figure 16.2.2)
Pinch the ILM with the forceps and move the tips of the closed forceps slowly from side to side until an ILM break occurs. If the retina is grasped as indicated by movement of retinal blood vessels, it should be released and re-grasped with a slightly shallower bite. Re-grasping the site previously grasped is often easier as the ILM will have tented up
After creating the ILM break, use the forceps to gently grasp the lifted edge of the ILM and then pull in a straight line tangential to the macula and parallel to the retinal surface. It is best if the piece of peeled ILM is not completely detached off the retina- this allows for easier re-grasping for the next stage of the peel. Direct lifting up of the ILM off the retinal surface will often result in a shorter peel. As the retina has a concave surface, be cautious during the peeling to avoid dragging the forceps into the retina. In addition, if possible, avoid peeling directly towards the macula as this might cause foveal trauma
Peel the ILM circumferentially around the macula, like a capsulorrhexis (Figure 16.2.3). Once half of the ILM is peeled, the middle of the flap can be grasped and peeled directly over the hole. If the ILM flap detaches from the retina, re-grasp the ILM at the edge of where it has been peeled, away from the fovea. If membrane fragments are stuck to the forceps, this can be removed with an instrument wipe. Some surgeons will flick them off using the light pipe, but care must be taken to avoid inadvertently hitting the retina
It is essential to carefully observe the edges of the ILM during peeling. It provides the starting point for re-grasping the next peel attempt
Use the forceps to remove large pieces of ILM from the vitreous cavity as they are peeled. This avoids the need to remove them with the vitreous cutter later on- sometimes they can be difficult to “chase”. Leaving them in the eye risks the patient complaining of post-operative floaters
Use the vitreous cutter to aspirate residual pieces of ILM from the vitreous cavity
There is no consensus on the extent of ILM peeling (Figure 16.2.4). The correct extent ensures that sufficient traction has been relieved to allow the hole to close. In order to ensure that traction is sufficiently removed around a large macular hole, extended ILM peeling up to the arcades or an inverted ILM flap is performed. Sometimes, only a limited peel is performed in order to minimize the peeling risks which might be heightened when a patient is moving or the view is poor

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16 Vitreomacular Interface Disorders