Dr Barbara Parolini gives her guidance on navigating and managing the pathology in stages
Myopic traction maculopathy (MTM) is a pathology reported to affect 20% of eyes with pathologic myopia (PM), defined as a refractive error above 6 diopters and/or axial length above 26.5 mm1–3-16.93 +/- 5.74
In eyes with PM, tractional forces act on the retina and the fovea. Forces perpendicular to the retinal plane can cause maculoschisis or detachment. Forces tangential to the retinal plane can cause lamellar macular holes and full thickness macular holes.
MTM is a spectrum of different clinical pictures. The MTM staging system (MSS) describes the nomenclature of MTM as well as a proposal of pathogenesis, natural evolution and prognosis and offers potential guidelines for management.4
The MSS is summarised in Figure 1. The four rows represent the evolution of the disease in a direction perpendicular to the macular plane from inner/ outer schisis (stage 1) to predominantly outer schisis (stage 2) to schisis-detachment (stage 3) to complete macular detachment (stage 4). The 3 columns represent the evolution in a direction tangential to the macula from normal fovea (stage a) to the formation of an inner lamellar macular hole (stage b) to full-thickness macular hole (stage c).
The outer lamellar macular hole, marked as a capital O in the MSS, represents an interruption in the line of the photoreceptors which might occur in stage 2, 3, and 4. The presence of epiretinal abnormalities is marked as + (read as “plus”) and might occur in every stage. The retina can evolve from stage 1 to stage 4 and from stage a to c simultaneously or separately. The average time taken to evolve from one stage to the next is marked in the MSS Table. MTM stages might show a spontaneous improvement.5 However, we observed that, when the eyes are followed for a long time, even after spontaneous resolution, MTM might restart and still evolve.
The best management of MTM
Early stages such as 1a and 2a, with intact fovea and good vision, should be observed since progression is slow. For more advanced cases treatment is recommended. Forces perpendicular to the retinal plane, causing maculoschisis and detachment, can be counteracted by placing a macular buckle (MB) that pushes the sclera toward the retina. Forces tangential to the retinal plane, causing lamellar or full thickness macular hole, can be counteracted by pars plana vitrectomy (PPV) and manoeuvres on the internal limiting membrane (ILM) and ILM flap. The elevation of ILM and the creation of an ILM flap create a force pointing toward the centre of the fovea. PPV can also counteract the forces perpendicular to the retinal plane exerted by the vitreous pulling the retina anteriorly. The management customised per stage is summarised in the Table.
Possible complications of MB are superficial extrusion of the lateral arm of the MB (5%), temporary foveal detachment (1%), diplopia (1%) and temporal choroidal hemorrhage (0.5%). Possible complications of PPV are temporary foveal detachment, worsening of the retinal stage, jatrogenic FTMH (20%), retinal detachment relapse, proliferative vitreoretinopathy, other complications inherited to PPV including cataract, vitreous hemorrhage, choroidal hemorrhage, retinal tears and secondary glaucoma or hypotony.8-10
One additional advantage of using a MB to solve the schisis and detachment secondary to MTM is to avoid the use of silicone oil, often proposed when treating the frequent relapsed retinal detachment in MTM. Standard or heavy silicone oil in highly myopic eye leads inevitably to secondary glaucoma.
The MB is a device that shortens the eye. The surgical technique aims to counteract the pulling effect exerted on the retina by the elongation of the sclera. A recent model of MB was designed, the NPB (AJL, Spain). The buckling side of the device (head of the buckle) is placed behind the posterior pole in order to push the sclera anteriorly and has a lodge for an illuminated fiber. The lateral side (arm of the buckle) is as large as the head and has holes in the most anterior side to guide the suture.
Surgery may be performed under general or local anesthesia. For local anesthesia, weprefersub-Tenon anesthesias with a blunt cannula to avoid scleral perforation with retrobulbar injections in high myopic eyes.
Surgery step by step
It is important to avoid excessive indentation of the sclera. The final profile of the retina and the sclera should be as flat and horizontal as possible resembling a nonmyopic macula. Intraoperative OCT can assist centring the buckle and setting the right amount of indentation, although the procedure can be completed without. By following these guidelines, the prognosis of surgery offers good expectations.
The best-corrected visual acuity (BCVA) improves significantly, although BCVA is limited by the amount of preoperative atrophy and anterior media opacity. It is important to highlight this because currently high myopic eyes with MTM are expected to improve only anatomically and not functionally after surgery.6
A long-term study on the evolution of macular atrophy after macular buckle insertion was undertaken and still ongoing (unpublished data of the author). Preliminary data show a 46% evolution rate in the macular buckle group versus a 66% evolution rate in the control group (contralateral nonoperated eye).
Barbara Parolini, MD | E: email@example.com
Parolini is the head of the vitreoretinal unit at the Eyecare Clinic in Brescia, Italy.She is a consultant for AJL Ophthalmic.