haps as innocent bystanders) in the process of proliferative vitreo-retinal membrane formation [24]. This most likely accounts for the hypercellularity of premacular membranes in MP. Hyalocytes have also been shown to be capable of inducing membrane contraction [25], another important component in the pathophysiology of MP. Thus, following anomalous PVD with vitreoschisis, the remnant hyalocytes can induce cell migration and proliferation as well as collagen contraction, all important features of macular MP.

Recent studies using OCT/SLO detected multifocal retinal contraction in nearly half of eyes with MP (Fig. 14.6) [20]. In this investigation, multifocal retinal contraction was associated with more intraretinal cysts and macular edema than unifocal MP, suggesting that multifocality may cause greater retinal damage, possibly due to greater amounts of tangential traction. Another feature that has been found to be associated with the formation of intraretinal cysts in MP is VPA (Fig. 14.7). In that study [17], a higher incidence of intraretinal cysts was found in eyes with MP and VPA (80%) when compared with those having MP without VPA (4.3%), suggesting that VPA may

Fig. 14.6  Multifocal retinal contraction in MP. The coronal plane OCT image shows three centers of retinal contraction. Studies have shown that nearly half of eyes with MP have multifocality on coronal plane imaging. The number of contraction centers also appears to correlate with the degree of retinal damage, possibly secondary to greater tractional force

contribute to intraretinal cyst formation by providing an anchor for the forces of tangential traction on the macula.

14.6.2  Macular Hole (MH)

Macular hole (MH) is characterized by a full-thickness defect of the neural retina in the center of the macula. Most cases are unilateral, but 10–20% of patients can be affected bilaterally. Presenting symptoms include central visual distortion, central scotomas, and loss of visual acuity. The prevalence of MH has been reported to be 1:3,300, usually affecting patients in the 6th and 7th decades of life [26]. The incidence in women is twice as high as in men [27]. SD-OCT/SLO is particularly helpful in identifying and staging MH as it provides precise in vivo measurement of MH diameter as well as accurate characterization of the vitreo-macular interface.

The cause of MH is not known. Gass described four stages based on biomicroscopic observations [28–30]. In a stage 1 MH, the retina is believed to be intact without neural retinal defect or vitreo-foveal separation. Oblique vitreous traction on the fovea has been speculated to be the initial mechanism. Stage 1 MH can be further divided into stage 1a and stage 1b, the former characterized by a small central yellow spot representing cystic changes within the fovea [31]. Tangential vitreous traction on the fovea may cause elevation of the fovea, foveal detachment, and an increase in the xanthophyllic pigment. A yellow ring in the foveal area with a bridging interface characterizes stage 1b MH. An MH progresses to stage 2 when the vitreofoveal separation occurs. Recently, it has been proposed that perifoveal vitreous detachment is the primary pathogenic event in MH formation [32]. A stage 2 MH is characterized by a central or eccentric full thickness retinal defect (100–300 mm) with or without an overlying pseudo-operculum. Unlike stage 1 MH, most stage 2 holes will advance to stage 3 as a result of persistent vitreo-foveal traction. Stage 3 MH is characterized by a central round full-thickness retinal defect (350–600 mm) associated with a gray ring surrounding the hole (previously believed to be a cuff of subretinal fluid), yellow deposits, and cystic changes. A stage 4 MH is distinguished from a stage 3 MH by a complete PVD.

Recent studies have identified vitreoschisis (Fig. 14.8) in 53% of eyes with MH. The vectors of force that induce tangential vitreo-retinal traction most likely result from anomalous PVD, but there may also be a contribution from persistent adhesion of vitreous to the optic disc. Studies [17] have shown that VPA is far more prevalent in MH (87.5%) than lamellar hole (LH) (36.4%) and MP (17.9%), suggesting that persistent adhesion at the disc

may contribute to the hole formation. While anomalous PVD with vitreoschisis may be the initial event in the pathophysiology of both MH and MP, VPA could influence the vector of forces and subsequent course of pathology. Persistent traction at the disc provides an anchor for outward (centrifugal) tangential traction, resulting in central retinal dehiscence and MH development (Fig. 14.9). In the absence of VPA, inward (centripetal) tangential traction is more likely and will result in MP.

In recent years, vitrectomy with membrane peel and air-fluid exchange has become a successful treatment for MH, with a very high (85–100%) reported closure rate [33, 34]. Intraoperative findings and histological analyses have determined that these membranes are thin and hypocellular. This is consistent with the hypothesis that if

anomalous PVD and vitreoschisis play a role in MH pathogenesis, then the split most likely occurs posterior to the level of the hyalocytes embedded in the posterior vitreous cortex [11]. These cells separate away from the retina along with the anterior portion of the posterior vitreous cortex, leaving the thinner, hypocellular portion attached to the macula. Persistent attachment of vitreous to the optic disc (found in 87.5% of cases) somehow influences the tangential forces that open a dehiscence in the central macula (Fig. 14.9).

Another interesting feature that was demonstrated by coronal plane imaging with combined OCT/SLO was that 40% of subjects with MH also have eccentric MP. Thus, the level of the split, which occurs during anomalous PVD with vitreoschisis, may not be the same in all MP