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New Retinal Physician

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So You Have Diagnosed MacTel—Now What?

The retinal physician's duty does not end at diagnosis.

By: Zack Oakey, MD
New Retinal Physician July 1, 2022 Vol Retinal Physician 19, Issue July/August 2022 Page(s): 9-11, 17

Macular telangiectasia (MacTel), also known as idiopathic juxtafoveal or perifoveal telangiectasia, is a capillary disorder of the central retina. While various classification schemes have been created to better understand its manifestations, two basic forms are described. Type 1 is a developmental or congenital manifestation, usually unilateral, and part of a larger spectrum of vascular pathology found in Coats disease. Type 2 is a presumably acquired bilateral form found in middle-aged and older persons. This article will focus on the diagnosis and treatment of MacTel type 2.

In the Beaver Dam Eye Study, fundus photos of 4,780 subjects aged 43 to 84 were graded, with 5 individuals found to have MacTel type 2. This translates to a prevalence of 0.1% with an average age of 63 years at the time the condition was identified.1 While many who develop MacTel retain useful vision throughout life, a substantial number can lose vision through progressive atrophy or neovascularization. Knowing that progressive transformation to neovascular disease is possible, one must ask, how common is neovascularization sufficient to justify surveillance? And, if treated using currently available technology, is improved visual function attainable?

In its early appearance, MacTel exhibits a loss of retinal transparency, beginning temporally. As the disease progresses it may show dilated, ectatic capillaries to crystalline deposits, hard exudates, RPE cell migration, and atrophic changes (Figure 1). During this years-long transition, type 2 patients may develop asymmetric vision loss; one eye may be more affected than the other, but findings will be present in both eyes. The final resulting vision tends to fall within the 20/60 range; however, significant variation occurs, with some patients in the late atrophic stages developing 20/200 vision or worse. At this time there is no FDA-approved therapy to halt atrophic progression, though ciliary neurotrophic factor is being investigated.2

FIGURE 1. Color fundus photography showing pigmentary changes temporal to the fovea (A). There are ectatic capillaries and white-appearing crystalline deposits. OCT scanning (B) shows focal attenuation of the inner segment and outer segments of the juxtafoveal retina. IMAGE COURTESY ZACK OAKEY, MD
FIGURE 1. Color fundus photography showing pigmentary changes temporal to the fovea (A). There are ectatic capillaries and white-appearing crystalline deposits. OCT scanning (B) shows focal attenuation of the inner segment and outer segments of the juxtafoveal retina. IMAGE COURTESY ZACK OAKEY, MD

It has been felt that given the bilateral manifestation and higher incidence among monozygotic twins, as well as siblings and families, that genetic factors may play a role in the pathogenesis of the disorder.3,4 This was especially suspected when vertical transmission was identified in families, suggesting a dominant inheritance though with reduced penetrance given manifold phenotypes.5 However screening programs to identify candidate genes have proven unsuccessful.6

In some patients intraretinal thickening, subretinal or intraretinal hemorrhage, and possible visible vascular complex development with anastomoses and disciform scarring may occur, coinciding with significant vision loss. This is a neovascular process for which the retinal physician may be able to treat patients with available anti-VEGF technology. Otherwise, until a pre-neovascular treatment is developed, screening and surveillance is the only approach.

New vessels formed in MacTel are different from those more commonly found in the retina clinic for such disorders as neovascular age-related macular degeneration (AMD) wherein the source of neovessels is the choroid. In MacTel subretinal neovascularization is theorized to originate not from the choroid but from the deep retinal circulation. Retinal-retinal and retinal-subretinal anastomosis are found. Proximal or connected to these anastomoses are dilated and exuding aneurysms stimulating neovessel growth. A patient’s acuity in most cases declines substantially from baseline when neovascularization occurs, and there may be visible intraretinal or subretinal hemorrhage on clinical exam (Figure 2). When fluorescein angiography (FA) and optical coherence tomography (OCT) have been employed to understand neovascular anatomy, one can find the exudative aneurysm(s) and reactive neovessels. Additionally, subretinal fluid and intraretinal fluid that was not present prior to onset are now visible (Figure 3).

FIGURE 2. A color fundus photograph demonstrating neovascular macular telangiectasia type 2. The blue arrow indicates retinal-retinal anastomoses. The yellow arrow identifies a dilated aneurysm with hemorrhagic features. IMAGE COURTESY ZACK OAKEY, MD
FIGURE 2. A color fundus photograph demonstrating neovascular macular telangiectasia type 2. The blue arrow indicates retinal-retinal anastomoses. The yellow arrow identifies a dilated aneurysm with hemorrhagic features. IMAGE COURTESY ZACK OAKEY, MD
FIGURE 3. Fluorescein angiography and optical coherence tomography of a patient with neovascular macular telangiectasia. Yellow arrow (A) highlights an aneurysmal vascular change; blue arrow shows a proximal anastomosis. Imaging with Heidelberg OCT (B) reveals new subretinal fluid with intraretinal disorganization (most probably indicated intraretinal fluid) out of proportion to what is found in the contralateral eye. After the patient is treated with anti-VEGF injection (C), disorganization or intraretinal fluid and subretinal exudative fluid findings are resolved and the patient’s acuity returns to baseline. IMAGE COURTESY ZACK OAKEY, MD
FIGURE 3. Fluorescein angiography and optical coherence tomography of a patient with neovascular macular telangiectasia. Yellow arrow (A) highlights an aneurysmal vascular change; blue arrow shows a proximal anastomosis. Imaging with Heidelberg OCT (B) reveals new subretinal fluid with intraretinal disorganization (most probably indicated intraretinal fluid) out of proportion to what is found in the contralateral eye. After the patient is treated with anti-VEGF injection (C), disorganization or intraretinal fluid and subretinal exudative fluid findings are resolved and the patient’s acuity returns to baseline. IMAGE COURTESY ZACK OAKEY, MD

RISK OF NEOVASCULARIZATION

When a patient first presents with non-neovascular MacTel type 2, one important question the consulting retina specialist must address is the frequency of screening, surveillance, and counsel regarding the specific risk and incidence of neovascular disease. This manifestation is currently the only modifiable feature of the condition and has debilitating consequences. Therefore, until a proven therapy can be developed for the degenerative aspects, this specific element of consultation may be the cornerstone of the entire visit besides clarifying the diagnosis. It is certainly the author’s experience that many of these patients are mistaken for neovascular AMD and may receive intravitreal injection of anti-VEGF medications prior to presentation to a retina specialist when it may not be warranted given a more correct diagnosis of non-neovascular MacTel. By a simple clarification of the diagnosis, a patient is spared non-evidence-based therapy.

An examination of the literature can help ascertain how prevalent neovascularization may be. In 2006, Yanuzzi et al reviewed 36 patients who were seen over a 3-year period with macular telangiectasia. Of those patients, 10 eventually developed what was termed “aneurysmal” telangiectasia or neovascularization.7 The time from presentation to diagnosis was not described, nor was a predictive scheme developed to ascertain specific risk of neovascularization based on anatomic findings in a way similar to AMD. When Gass and Blodi reviewed 182 eyes (44 male, 48 female), 25 eyes reached what they termed Stage 5 or a neovascular state.8 When 72 patients of this group were followed for 2 years or longer (24 to 316 months, mean 91 months), 37 were legally blind (20/200 or worse), the primary cause of which was foveal atrophy in 26, choroidal neovascularization (CNV) in 10, and cataract in 1. When other studies have attempted to characterize MacTel’s epidemiology, only color fundus photography has been used, severely limiting understanding of the incidence of neovascular phenotypes that may be amenable to medical management.1,9,10 It has been shown that using a collage of more advanced imaging technologies—such as FA, OCT, or confocal scanning laser ophthalmoscopy imaging—is more sensitive in detecting early and/or asymptomatic disease stages.3 Logically, therefore, the true incidence of neovascularization remains unknown.

Nevertheless, some simple mathematics shows that 27.7% of the limited population studied by Yanuzzi had neovascular disease. In Gass and Blodi’s review, 13.7% of the 182 eyes studied developed neovascularization, and among those studied for a longer period, a similar crude incidence was discovered of 13.9%. Given the size of the population studied by Gass and Blodi, this may be a more accurate figure; however, as noted above, a more thorough longitudinal study has yet to be conducted utilizing all available imaging modalities.

When neovascular disease is present, treatment may not always be indicated. When fibrovascular proliferation injures photoreceptors, further efforts to curtail exudation may not be productive analogous to chronic, inactive neovascular AMD following foveal or macular injury. A review was conducted on those with inactive but neovascular MacTel type 2 disease and 20/200 or worse acuity; function did not change over time when improvement was not felt possible with intervention.11 Therefore, it has been proposed that, similar to neovascular AMD patients, early intervention prior to fibrosis is needed.

Among the first nondestructive therapies attempted for neovascular MacTel was photodynamic therapy (PDT). The largest study conducted included 6 patients.12 An average of 2.4 treatments were given according to a standard protocol. Mean follow-up time after the last treatment was 21 months and median initial and final visual acuity was 20/80. More than 2 lines decrease or increase in visual acuity was observed in one eye each while the other 5 eyes remained stable.

With the advent of anti-VEGF therapies, many have studied their benefits. The largest study so far available for review in the English language was a retrospective case series including 16 treatment-naive eyes of 16 patients. They were treated with intravitreal ranibizumab or bevacizumab monotherapy. A mean of 1.9 injections (range, 1 to 3 injections) were needed during a mean follow-up time of 12 months (range, 3 to 43 months). Mean visual acuity improved significantly from 20/120 to 20/70.13 The results of treatment with combined PDT and ranibizumab has been published in two case reports.14,15 An improvement of visual acuity from 20/125 to 20/60 and stabilization thereafter was achieved within a follow-up period of 9 months in one patient, and stabilization was achieved in the second patient. Only one PDT treatment with either one or two intravitreal injections was necessary.

As compared with extensive and populous studies conducted for neovascular AMD, the above evidence is somewhat underwhelming in MacTel. All treatments have been employed off label. Nevertheless, this author has had similar experience with improved visual function when the neovascular lesion is treated prior to the onset of fibrosis (Figure 3). It is my preference when meeting a patient with MacTel type 2 to suggest semiannual screening aided by angiography and OCT with the use of an Amsler grid at home. Informing a patient of a potential loss of vision may reduce the incidence of permanent harm to vision given sufficient understanding and a correct diagnosis. NRP

DR. OAKEY is a vitreoretinal surgeon with Pomona Valley and Arrowhead medical centers in Rancho Cucamonga, CA. He reports no disclosures. Reach him at oakeyz@gmail.com.

REFERENCES

  1. Klein R, Blodi BA, Meuer SM, Myers CE, Chew EY, Klein BE. The prevalence of macular telangiectasia type 2 in the Beaver Dam eye study. Am J Ophthalmol. 2010;150(1):55-62.e2. doi:10.1016/j.ajo.2010.02.013
  2. Chew EY, Clemons TE, Jaffe GJ, et al. Effect of ciliary neurotrophic factor on retinal neurodegeneration in patients with macular telangiectasia type 2: a randomized clinical trial. Ophthalmology. 2019;126(4):540-549. doi:10.1016/j.ophtha.2018.09.041
  3. Gillies MC, Zhu M, Chew E, et al. Familial asymptomatic macular telangiectasia type 2. Ophthalmology. 2009;116(12):2422-2429. doi:10.1016/j.ophtha.2009.05.010
  4. Chew EY, Murphy RP, Newsome DA, Fine SL. Parafoveal telangiectasis and diabetic retinopathy. Arch Ophthalmol. 1986;104(1):71-75. doi:10.1001/archopht.1986.01050130081025
  5. Parmalee NL, Schubert C, Figueroa M, et al. Identification of a potential susceptibility locus for macular telangiectasia type 2. PLoS One. 2012;7(8):e24268. doi:10.1371/journal.pone.0024268
  6. Parmalee NL, Schubert C, Merriam JE, et al. Analysis of candidate genes for macular telangiectasia type 2. Mol Vis. 2010;16:2718-2726.
  7. Yannuzzi LA, Bardal AM, Freund KB, Chen KJ, Eandi CM, Blodi B. Idiopathic macular telangiectasia. Arch Ophthalmol. 2006;124(4):450-460. doi:10.1001/archopht.124.4.450
  8. Gass JD, Blodi BA. Idiopathic juxtafoveolar retinal telangiectasis: update of classification and follow-up study. Ophthalmology. 1993;100(10):1536-1546.
  9. Aung KZ, Wickremasinghe SS, Makeyeva G, Robman L, Guymer RH. The prevalence estimates of macular telangiectasia type 2: the Melbourne Collaborative Cohort study. Retina. 2010;30(3):473-478. doi:10.1097/IAE.0b013e3181bd2c71
  10. Sallo FB, Leung I, Mathenge W, et al. The prevalence of type 2 idiopathic macular telangiectasia in two African populations. Ophthalmic Epidemiol. 2012;19(4):185-189. doi:10.3109/09286586.2011.638744
  11. Engelbrecht NE, Aaberg TM Jr, Sung J, Lewis ML. Neovascular membranes associated with idiopathic juxtafoveolar telangiectasis. Arch Ophthalmol. 2002;120(3):320-324. doi:10.1001/archopht.120.3.320
  12. Potter MJ, Szabo SM, Sarraf D, Michels R, Schmidt-Erfurth U. Photodynamic therapy for subretinal neovascularization in type 2A idiopathic juxtafoveolar telangiectasis. Can J Ophthalmol. 2006;41(1):34-37. doi:10.1016/S0008-4182(06)80063-3
  13. Narayanan R, Chhablani J, Sinha M, et al. Efficacy of anti-vascular endothelial growth factor therapy in subretinal neovascularization secondary to macular telangiectasia type 2. Retina. 2012;32(10):2001-2005. doi:10.1097/IAE.0b013e3182625c1d
  14. Rishi P, Shroff D, Rishi E. Combined photodynamic therapy and intravitreal ranibizumab as primary treatment for subretinal neovascular membrane (SRNVM) associated with type 2 idiopathic macular telangiectasia. Graefes Arch Clin Exp Ophthalmol. 2008;246(4):619-621. doi:10.1007/s00417-007-0732-0
  15. Ruys J, De Laey JJ, Vanderhaeghen Y, Van Aken EH. Intravitreal bevacizumab (Avastin) for the treatment of bilateral acquired juxtafoveal retinal telangiectasis associated with choroidal neovascular membrane. Eye (Lond). 2007;21(11):1433-1434. doi:10.1038/sj.eye.6702946

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