A man in his mid 70s presented with drastically decreased vision of his right eye starting that morning upon awakening. He reports a recent diagnosis of wet macular degeneration in the same eye one week prior to presentation. His visual acuity was “hand motion” in the right eye and 20/40 in the left eye. The intraocular pressures and pupil exam findings were normal. He had modest cataracts in both eyes. He was a past smoker for nearly 35 years.
The dilated fundus exam of the right eye revealed a large suspected neovascular membrane with retinal thickening and hemorrhage. The left eye’s fundus exam showed a blunted foveal reflex but no hemorrhage. Optical coherence tomography (OCT) and OCT-angiography imaging was completed to better evaluate the fundus findings.
What happened next
Despite a guarded visual prognosis, the patient was motivated to undergo treatment to attempt improving his vision in the right eye and received a series of three monthly intravitreal injections of an anti-VEGF agent. The visual acuity did not improve significantly with treatment, and observation was recommended. About two years later, the patient, who had been following up routinely with his retina specialist, returned to the ophthalmic emergency room with a complaint of decreased vision in his left eye for 3 days. His vision had declined from 20/40 to 20/250. On examination, there was a subtle change in the left fundus but no hemorrhage was seen. OCT imaging revealed the presence of intraretinal fluid, pigment epithelial detachments, and increased outer retinal distortion suspicious for active neovascularization (Image 5). The left eye received an intravitreal injection of anti-VEGF, and the patient followed up monthly afterwards.
Do you agree with the initial diagnosis?
The patient was diagnosed with age-related macular degeneration at an outside office visit, but interestingly, that may not be the true etiology of our patient’s vision loss. The right eye’s fundus was at a late stage of disease at presentation and therefore difficult to assess, but the left eye can give us a couple of clues. On the OCT (Figure 3A), we see a finding that is often misdiagnosed as macular edema. The dark retinal spaces represent inner and mid retinal cavitations with a visible overlying internal limiting membrane (ILM). One clue in differentiating these findings from edema is that in cystoid macular edema, there is thickening of the retina. In our patient, there was mild thinning of the central macula. Additionally, the OCT-A reveals an abnormality in temporal parafoveal deep capillary plexus. Both of these findings can be seen in a condition known as macular telangiectasia, or MacTel. Although our patient did have a couple drusen – and therefore early macular degeneration was likely also present – it wasn’t likely a solo player.
What is MacTel?
Macular telangiectasia (MacTel) is a condition affecting the microvasculature of the macula. It is grouped into two main categories. Type 1 is generally characterized by unilateral paramacular aneurysmal telangiectasias and macular edema. The most common subtype, type 2, is seen bilaterally and presents with temporal retinal loss of transparency, inner (and later outer) retinal cavitations, preservation of the ILM (“ILM drape”) on OCT, and outer retinal atrophy (1). MacTel type 2 may present with subretinal and choroidal neovascular membranes at the advanced stage of disease. There is a third type of MacTel that remains very rare and is poorly described.
Our patient was diagnosed with MacTel type 2 given the bilateral findings, so we will focus the remainder of discussion on this type. MacTel 2 occurs in individuals over 40 years of age and is more common in women. There does appear to be a genetic component, but there are likely numerous genes implicated in this disease. Additionally, external factors such as smoking, diabetes mellitus, hypertension, and coronary artery disease may also play a contributing role in disease manifestation(2).
Both OCT and OCT-A have proved invaluable to diagnosis and monitoring of MacTel. Given this is a microvascular disease and difficult to diagnose clinically at its onset, OCT-A provides critical information. Early in the disease process, when the fundus exam may still appear normal, OCT will often reveal retinal cavitations with the classic ILM drape (Image 3). OCT-A typically demonstrates dilated vasculature in the temporal deep retinal capillary bed (seen in our patient’s left eye, Image 4). As MacTel 2 progresses, the vascular telangiectasias progress in number and extend into other layers of the retina. Retinal anastoamoses begin form, and in the late (or proliferative) stage of disease, subretinal fibrovascular plaques develop. It is thought that this neovascular membrane communicates with both the retinal and choroidal circulation(2). This varies from the more commonly diagnosed exudative age-related macular degeneration, which typically has choroidal (not subretinal) neovascular membranes.
Treatment in patients with MacTel type 2 is, at this time, generally reserved for those who develop proliferative disease. In these cases, anti-VEGF agents are injected into the vitreous. These intravitreal injections, in many cases, can arrest progression of the neovascular membrane. In some, intravitreal injections may improve visual acuity, although visual recovery is less likely if the neovascular membrane is located in the subfoveal area (4). Although there are no pharmacologic treatments available for early and mid stages of MacTel type 2, Phase 2 and 3 studies are underway to study the effect of an implant containing ciliary neurotrophic factor (CNTF) (Neurotech 501 Cell Implant, Neurotech Pharmaceuticals).
Citations
- Yannuzzi LA, Bardal AMC, Freund KB, Chen KJ, Eandi CM, Blodi B. Idiopathic macular telangiectasia. Arch Ophthalmol. 2006;124(4):450-460.
- Kedarisetti KC, Narayanan R, Stewart MW, Reddy Gurram N, Khanani AM. Macular telangiectasia type 2: a comprehensive review. Clin Ophthalmol. 2022;16:3297-3309.
- Roisman L, Rosenfeld PJ. Optical coherence tomography angiography of macular telangiectasia type 2. Dev Ophthalmol. 2016;56:146-158.
- Charbel Issa P, Kupitz EH, Heeren TFC, Holz FG. Treatment for macular telangiectasia type 2. Dev Ophthalmol. 2016;55:189-195.
