28

QUESTION

HOW DO I DIFFERENTIATE A MACULAR HOLE FROM A LAMELLAR HOLE FROM AN EPIRETINAL MEMBRANE WITH A PSEUDOHOLE, AND WHY DO I CARE?

SriniVas R. Sadda, MD

Optical coherence tomography (OCT) has proven to be a critical tool in the evaluation of the vitreoretinal interface.¹ In addition to providing high-resolution cross-sectional images of the neurosensory retina, OCT is also capable of demonstrating the relationship between the posterior hyaloid and the retina—a relationship that is difficult to assess by clinical examination alone. In fact, when OCT imaging was first introduced in the early 1990s, the ability to distinguish similar yet distinct conditions, such as macular hole, lamellar hole, epiretinal membrane (ERM) with pseudohole, and vitreomacular traction (VMT) syndrome, was among the first really useful clinical applications of the new technology. Further advances in OCT, including the development of high-speed, highly-sensitive swept source OCT technology has allowed the vitreoretinal relationships to be understood in even greater detail (Figure 28-1), and for the steps in the evolution of vitreous detachment to be identified.

Prior to the introduction of OCT, there were many hypotheses, but only limited evidence regarding the pathogenesis of macular hole and associated disorders. While there is still more to be learned, it is now clear that macular hole, ERM, and related vitreomacular interface (VMI) disorders are due to abnormalities in the normal vitreous separation process.² The normal process of vitreous detachment involves progressive liquefaction of the vitreous (leading to increased mobility) as well as weakening of the adhesion between the vitreous and retina. Defects in this normal process can lead to these VMI diseases. For example, if liquefaction of the vitreous gel outpaces the weakening of the adhesion, vitreous movements can lead to traction on the retina at points of continued attachment (eg, at the fovea).² This traction results in structural changes at the foveal center and ultimately the formation of a macular hole or related condition. Alternatively, in some cases, the main body of the cortical vitreous separates, but small bits of residual vitreous remain adherent to the retinal surface. These residual islands of vitreous may form the nidus for subsequent epiretinal proliferation.

This improved understanding of the pathophysiology of these vitreoretinal disorders and the broad availability of OCT allowed the development of a new international consensus classification of VMI diseases.2 This new classification system also identifies specific features to define and differentiate these disorders and includes specific subclassifications that help define the appropriate management.

Full-Thickness Macular Holes

Full-thickness macular hole (FTMH) formation is age-related, typically occurring in postmenopausal women. A staging system for macular holes was originally suggested by Johnson and Gass³ and subsequently adapted (with minor modifications). In these original staging systems, a Stage I hole was defined by pseudocyst formation in the inner retina (Figure 28-2), which sometimes may be seen clinically as a yellow dot or ring. This was thought to be an important stage to recognize clinically, since in many cases, spontaneous resolution was possible. In Stage II, there is early separation of the outer photoreceptor layer and, consequently, small full-thickness loss of retinal tissue (Figure 28-3). Stage III occurs when the hole is greater than 400 μm in diameter with surrounding thickened retina, including intraretinal cystoid spaces. Stage IV holes consist of Stage III holes with a complete posterior vitreous detachment (Figure 28-4). Although not originally defined by Johnson and Gass, some investigators also defined a Stage 0 hole to refer to the fellow eye with vitreomacular adhesion (VMA) (but no traction) of a patient with FTMH in the one eye—such an eye was thought to still be at risk for developing a FTMH. Prior to the advent of OCT, the subjective disappearance of a portion of a slit beam of light (Watzke-Allen test) or a laser aiming beam projected into the hole was a useful method for distinguishing a FTMH from other vitreoretinal interface disorders. Despite its widespread use, this staging system had several obvious limitations. For example, patients with small holes (eg, < 400 μm) could develop vitreous separation (see Figure 28-4). Such a hole would then be considered a Stage IV hole though it may be smaller than a larger Stage III hole with some persistent vitreous attachment. Due to these inconsistencies, and to provide a classification system that would be relevant to pharmacologic and surgical therapeutics, the International Vitreomacular Traction Study (IVTS) group was convened.2 The IVTS system classified holes based on size and presence or absence of traction. The old term Stage 0 hole was replaced by VMA. The term Stage I hole or impending macular hole was replaced by VMT. VMA and VMT were distinguished based on demonstrable morphological changes in the retina in the setting of VMT (see Figure 28-2). FTMH were classified as having VMT present or absent and also classified by size as small (aperture < 250 μm), medium (250 to 400 μm), and large (> 400 μm). The cutoff of 250 μm for small holes was based on the fact that these holes do have a small rate of spontaneuous closure, a very high closure rate with vitrectomy,^4,5 and the most favorable outcome with pharmacologic vitreolysis (eg, ocriplasmin).^6,7 The cutoff of 400 μm was chosen because these holes were unlikely to close with pharmacologic approaches. This new system does not easily align with the old Gass system. A Gass Stage II hole would be a small or medium FTMH with VMT with the new system (see Figure 28-3). A Gass Stage III hole would be a medium or large FTMH with VMT, and a Gass Stage IV hole would be small (see Figure 28-4), medium, or large FTMH without VMT. Regardless, the recognition of FTMH hole is of critical importance as it defines an eye that likely will need therapeutic intervention.

Stay updated, free articles. Join our Telegram channel

Join