Vitreomacular traction (VMT) is an age-related condition of the eye where the naturally occurring vitreous gel pulls abnormally on the macula, the small central area of the retina responsible for detailed, sharp vision. This mechanical pulling action can distort the delicate retinal tissue, leading to a decline in central visual function. Understanding VMT involves recognizing how age-related changes can disrupt the interface between the vitreous and the retina, which ultimately affects a person’s ability to see fine details.
Understanding the Physical Cause
The interior of the eye is largely filled with the vitreous humor, a clear, gel-like substance that is attached to the retina by millions of fine collagen fibers. The macula, a specialized part of the retina, is where these attachments must be perfectly maintained for high-resolution vision. As a person ages, the vitreous gel begins to liquefy and shrink, a process that normally leads to a complete separation from the retina called a Posterior Vitreous Detachment (PVD).
Vitreomacular traction occurs when this separation is incomplete, and a portion of the vitreous remains firmly stuck to the macula’s surface. This persistent attachment then exerts a mechanical force on the macula, causing it to be pulled or distorted. The tractional forces can be directed either anteroposteriorly (straight back) or tangentially (sideways), leading to structural changes in the fovea, the center of the macula.
The severity of VMT is directly related to the strength and persistence of this pulling action. This mechanical stress can result in anatomical damage, such as the formation of fluid-filled spaces, or pseudocysts, within the retinal layers.
Recognizing the Signs
The visual consequences of VMT stem from the macula’s distortion. A common symptom is metamorphopsia, where straight lines appear wavy or bent, making tasks like reading challenging. Patients may also notice micropsia, a phenomenon in which objects appear smaller than their actual size.
Central vision may become blurry or diminished in sharpness, making it difficult to see fine details clearly. Some people report photopsia, which are brief flashes of light, a symptom caused by the vitreous pulling on the light-sensitive retinal tissue.
Classification and Diagnostic Tools
The diagnosis and classification of VMT rely heavily on advanced imaging technology, primarily Optical Coherence Tomography (OCT). The OCT device uses light waves to capture high-resolution, cross-sectional images of the retina and the vitreous interface, allowing ophthalmologists to visualize the anatomical disruption caused by the traction. This imaging precisely maps the area of attachment and any resulting structural damage.
The International Vitreomacular Traction Study Group developed an OCT-based classification system to standardize diagnosis. VMT is defined by the presence of an incomplete PVD with the vitreous cortex still attached to the macula within a three-millimeter radius, accompanied by foveal surface distortion. The condition is subclassified based on the width of the vitreous attachment: focal VMT is defined as an attachment of 1,500 micrometers or less, while broad VMT is greater than 1,500 micrometers.
Classification also includes whether the traction has caused specific structural complications. These complications can include the formation of intraretinal pseudocysts, cystoid macular edema (macular swelling), or a full-thickness macular hole (FTMH). The OCT also helps determine if the VMT is concurrent, meaning it is associated with another underlying macular disease like diabetic retinopathy.
Management Approaches
The treatment strategy for VMT is highly individualized, guided by the severity of the symptoms and the anatomical findings from the OCT scan. For mild cases where vision is not significantly impacted, the standard approach is watchful waiting, or observation. This is a viable option because VMT can resolve spontaneously, with studies showing a spontaneous resolution rate as high as 53% in some series.
Pharmacological Intervention
For symptomatic patients who meet specific criteria, a pharmacological intervention offers a non-surgical option. This involves an intravitreal injection of ocriplasmin, a recombinant proteolytic enzyme. Ocriplasmin works to dissolve the protein components, like laminin and fibronectin, that form the adhesion between the vitreous and the macula. By enzymatically cleaving these proteins, ocriplasmin facilitates the separation of the vitreous and relieves the traction.
The best candidates for ocriplasmin are those with focal VMT, defined as an attachment diameter of 1,500 micrometers or less, and who do not have an associated epiretinal membrane. Clinical trials have shown that this single injection can lead to a significantly higher rate of VMT resolution compared to a placebo, sometimes resulting in the closure of small macular holes.
Surgical Intervention
Surgical intervention, specifically a pars plana vitrectomy, represents the most definitive treatment and is typically reserved for severe or progressive cases. This procedure involves the surgeon using micro-instruments to enter the eye, remove the vitreous gel, and peel away any scar tissue that may be present on the macula. The removal of the vitreous immediately eliminates the source of the traction, allowing the macula to return to a more normal anatomical position. Vitrectomy is the preferred option when VMT has progressed to a larger full-thickness macular hole or when other treatments have failed to release the traction.