Macular Telangiectasia Type 2, or MacTel, is a progressive disease affecting the macula, the central part of the retina responsible for sharp, detailed vision. This condition develops in people between 50 and 60 and affects both eyes, though progression may not be symmetrical. The disease is a neurodegenerative condition where the loss of retinal Müller cells leads to changes in the capillary network. As the condition advances, it moves through several stages with unique effects on vision.
The Early (Non-Proliferative) Stages
The initial phases of MacTel Type 2 are non-proliferative, meaning there is no growth of new, abnormal blood vessels. In the first stage, changes are subtle, characterized by a slight graying or loss of transparency in the retina near the fovea. During this period, individuals rarely experience noticeable symptoms, making diagnosis uncommon. The earliest signs may only be detectable through advanced imaging.
As the disease moves into its next early stage, the signs become more apparent to an ophthalmologist. The capillaries in the macula become telangiectatic, meaning they are dilated and can leak. This leakage contributes to the loss of retinal transparency. A person might start to notice mild symptoms, such as blurriness in central vision or difficulty reading small print.
The third non-proliferative stage presents more definitive clinical markers. One sign is the appearance of right-angle venules, where small veins bend sharply as they dive into deeper retinal layers. Another characteristic is the presence of tiny, refractile crystalline deposits on the retina’s surface. Visual symptoms become more pronounced, with increasing blurriness and possible distortion.
The Advanced (Proliferative) Stage
The advanced, or proliferative, stage is defined by the development of new, abnormal blood vessels that grow beneath the retina, a process called subretinal neovascularization. These new vessels are fragile and prone to leaking fluid and blood into and under the macula.
This leakage causes rapid damage to the photoreceptor cells that detect light. The introduction of fluid and blood into these layers disrupts the macula’s function. A person entering this stage may experience a sudden decline in their central vision.
Common symptoms of the proliferative stage include a marked increase in visual distortion, where straight lines appear wavy or bent (metamorphopsia). Individuals may also develop a dark or gray spot in their central field of vision (a scotoma). The onset of these symptoms requires prompt medical attention to limit further vision loss.
End-Stage Macular Atrophy
The final phase of MacTel Type 2 is characterized by macular atrophy, the death and subsequent loss of the light-sensing photoreceptor cells and the underlying retinal pigment epithelium (RPE). The RPE is a layer that supports and nourishes the photoreceptors. This cellular death leads to a permanent scar in the macula.
This end-stage can result from a slow progression of the non-proliferative stages or occur more rapidly following damage from the proliferative stage. When the photoreceptor cells are lost, they are not replaced, resulting in an irreversible loss of function and a permanent central blind spot.
While this means the loss of sharp, straight-ahead vision, peripheral vision is preserved. The central vision loss is permanent, as current medical science cannot regenerate the lost retinal tissue.
Stage-Specific Management Approaches
Management of MacTel Type 2 is tailored to the disease stage. During the early, non-proliferative stages, the approach is monitoring. This involves regular eye examinations and imaging tests like Optical Coherence Tomography (OCT). These tests allow ophthalmologists to track the disease’s progression. Patients are encouraged to use an Amsler grid at home to self-monitor for new distortions in their vision.
Once the disease progresses to the proliferative stage, management shifts to active treatment. The primary intervention is anti-VEGF (vascular endothelial growth factor) injections into the eye. These medications work by blocking chemical signals that stimulate abnormal blood vessel growth and by reducing leakage. This treatment can help stabilize vision and, in some cases, partially restore it by reducing macular swelling, though it is not a cure.
In the end-stage, when significant atrophy and permanent cell loss have occurred, management moves from medical treatment to adaptation and rehabilitation. The goal is maximizing the utility of the remaining peripheral vision. This involves working with low-vision specialists and occupational therapists. They can recommend and provide training on various low-vision aids, such as magnifiers, specialized lighting, and electronic devices, to help individuals adapt to the loss of central vision and maintain their independence.