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Diagnosing MacTel

For Healthcare Providers

Macular telangiectasia type 2 is a rare disease of the retina that leads to a gradual loss of central vision. MacTel is estimated to affect about 0.1% of the population, and its onset is age-related. Affected individuals are typically diagnosed in their 40s and 50s. MacTel is sometimes mistaken for age-related macular degeneration, due to similar patterns of neovascularization in both diseases.  MacTel is a bilateral disease. Fellow eyes are usually similarly affected by the disease, showing the same pathological features. However, the disease may progress at a different rate in each eye.

The retinal alterations caused by MacTel usually begin in a temporal paracentral area. Retinal changes are most pronounced on the temporal side of the retina. Microperimetry and OCT studies to assess function and structure, respectively, suggest that the area temporal to the fovea can be considered the epicenter of disease.

As MacTel progresses, it may encompass an oval region with a radius of about 6⁰ horizontally and 5⁰ vertically, centered on the foveola. Alternatively, MacTel may affect a circular region of the retina, centered on the foveola. MacTel may also be restricted to the temporal macula, leaving the nasal side mostly unaffected.

Early Signs and Symptoms of MacTel

  • People with MacTel may experience some (or all) of the following symptoms:
    1. Blunting or lack of the foveolar reflex. This observation is restricted to early-stage disease.
    2. Crystalline deposits, located in the inner retina at the level of the inner limiting membrane. They may appear as hyperreflective dots at the anterior surface of the nerve fiber layer in OCT scans. The deposits are present at all stages of disease. In participants of the MacTel Natural History Study, 46% of patients had crystalline deposits. For those with deposits, 60% showed deposits bilaterally.
    3. Reduced retinal transparency in the parafoveolar area may be one of the first visible changes in the retina. This symptom is also referred to as retinal graying.
    4. Distorted or blurry vision.
    5. Scotoma or “spot” of worse vision in the center of the visual field
    6. Difficulty reading, missing/skipping letters, numbers or parts of words.
    7. Difficulty with adapting to changing light conditions or seeing in low-light conditions.

Common Symptoms of MacTel

  • Reduced number of Müller glia cells.
  • Changes in retinal pigment epithelial (RPE) cells.
  • Mildly ectatic capillaries affect primarily the deeper capillary network, though telangiectatic vessels have been observed in inner and outer retinal circulation.
  • Blunted, slightly dilated venules are often associated with ectatic capillaries and, in later disease stages, with retinal pigment plaques. These vessels don’t appear to narrow as they approach the foveola, rather, they suddenly seem to dive at right angles into the deeper retinal layers.
  • Foveal atrophy. This may appear as small foveal non-prominent cysts, or a pseudo-lamellar macular hole, or as slightly altered foveal reflectivity. Atrophy can be missed on fundus images. Atrophy of the outer retinal photoreceptor layer is the endpoint of MacTel, and results in localized loss of visual function.
  • Abnormal distribution of macular pigment. Macular pigment deposition is normally concentrated in the fovea. In MacTel eyes, there is a loss of macular pigment from the central retina. Instead, MacTel eyes show a ring of pigments about 12 degrees in diameter, much larger than the normal 1-2 degrees in diameter. This can be visualized with autofluorescence imaging. Studies found that dietary supplementation with lutein and zeaxanthin enhanced the existing ring of macular pigments, but does not restore normal macular pigment distribution.
  • Retinal pigment plaques (pigment-hyperplasia) seem to originate from small foci of RPE hyperplasia that migrate into the neurosensory retina. Photoreceptor atrophy precedes, and may cause, the presence of retinal pigment plaques. Retinal pigment plaques may be surrounded by RPE atrophy.

Rarely Observed Features of MacTel

  • A small round yellow spot may be found centered on the fovea, roughly ½-disc diameter size.
  • Small retinal hemorrhages in the absence of a neovascular complex. These are transient, usually resolving in a few weeks.
  • True lamellar, or full thickness macular holes, may occur. This is a complication of the disease, possibly resulting from the progressive degeneration and atrophy of the retina. Cellular death may destabilize the fovea, leading to a macular hole which may be more difficult to surgically treat than other types of macular holes.
  • Neovascular complexes may develop at any time point, and complicate the natural course of the disease. These are most commonly located temporal to the foveola. They seem to originate from the retinal vasculature, not the choroid as is seen in age-related macular degeneration. In MacTel, these neovascular complexes may, however, still gain access to the subretinal space and develop chorio-retinal shunts.

Disease Stages of MacTel

The following disease grading system was developed by Dr. Emily Y. Chew et al. based on research that was published in 2023 titled, “Macular Telangiectasia Type 2: A classification system using multi-modal imaging MacTel Project Report Number 10.” You can find the full article in the “Publications” section of the LMRI website. 

An important consideration for grading the severity/progression of MacTel includes 3 factors that have been found to be associated with visual acuity (VA) loss: 1) Ellipsoid Zone loss (a layer of the retina with photoreceptors), 2) changes in pigment, and 3) hyper-reflectivity as seen in OCT images.

Grade 0: Only key features of MacTel are present & none of the 3 factors associated with VA loss are   present

Grade 1: Break in the Ellipsoid Zone is present, but it is not in the fovea & VA is not affected

Grade 2: The break in the Ellipsoid Zone affects the fovea and the VA score drops by ~ 10 letters

Grade 3: The break in the Ellipsoid Zone affects the fovea and the VA score drops by ~ 15 letters

Grade 4: Hyper-reflectivity is observed in OCT images

Grade 5: Presence of pigment changes in the macula

Grade 6: Presence of pigment changes and neovascularization

Prognosis

MacTel is a progressive disease, which means that the vision continues to deteriorate gradually over time.

  • Loss of vision typically continues to progress over 10-20+ years after diagnosis.
  • Rate of vision loss can differ widely among MacTel patients:
    • Some people may experience a sudden loss in just a year or two and then remain stable for a long time, while others lose vision very slowly over the course of several decades.

Full blindness is not an expected outcome.