Retinal telangiectasis refers to a developmental retinal vascular disorder characterized by ectasias of capillaries of the retina, in which irregular capillary dilation and incompetence occur in the retinal periphery or at the macula. If only the capillaries of the foveal… are involved, it is called parafoveal telangiectasia, which is a condition of micro-aneurysmal and saccular dilation and capillary non-perfusion of the parafoveal capillaries. Right angle granules draining the telangiectatic capillary bed may also be seen.
Parafoveal telangiectasis can be considered as having two basic forms:
- A developmental or congenital vascular anomaly, which may be part of the largest spectrum of Coats Disease.
- A presumably acquired form found in middle-age and older patients.
1 a) Congenital Parafoveal Telangiectasia
Patients with unilateral congenital parafoveal telangiectasis typically are men whose mean age and onset of the disease is 40 years. The telangiectasis usually is confined unilaterally to the temple half of the macula, occurring in an area of one to two disc diameters with equal areas superior and inferior to the horizontal raphe. A limited number of cases with this have experienced improvement in visual acuity after treatment of the area with laser photocoagulation. Spontaneous resolution has also occurred.
1 b) Unilateral Idiopathic Parafoveal Telangiectasis
Unilateral idiopathic parafoveal telangiectasia is found in middle-aged men who have a very small area of capillary telangiectasis confined to one clock hour at the edge of the foveal avascular zone. This may or may not be accompanied by hard exudates. Rarely does the area of telangiectasis have much leakage in fluorescein angiography. Visual acuity is rarely less than 20/25. Those are the actual visual acuity, and the close proximity of the telangiectasis to the center of the foveal is probably not advisable to photocoagulate such lesions.
2 a) Bilateral Acquired Parafoveal Telangiectasias
This is the most common group of all patients with parafoveal telangiectasias. These patients typically are diagnosed in their 5th and 6th decade of life. Both sexes may be affected, familiar incidents also have been reported. Usually the telangiectasis is symmetric, bilateral, and involve an area less than one disc diameter. This often involves the area temporal to the fovea, or it may involve the entire parafoveal capillary network. Right angled retinal venules are commonly seen in this group of patients of parafoveal telangiectasis, and they appear on stereopsis viewing to be draining the outer retinal capillary plexus. A characteristic feature of this group is eventually to develop hyperplasia of the retinal pigment epithelial along these right angle venules.
2 b) Bilateral Idiopathic Parafoveal Telangiectasis and Capillary Obliteration
This is a rare form and occurs in the fifth decade of life with loss of central vision to the lead to blindness bilaterally secondary to telangiectasis and progressive obliteration of vessels enlargement of foveal avascular zone. Usually there is no fluorescein leakage from these telangiectatic vessels. Additional clinical features include optic disc palor, hyperactive, deep tendon knee reflexes and disc macular changes similar to those with sickle cell retinopathy.
Slight graying in the retinal area may be noted with mild to moderate dilation. Eventual development of the hyperplasia of retinal pigment epithelium will be noted. Some patients have yellow centered lesions, which will display leakage on fluorescein angiography. These yellow lesions are easily confused with adult vitelliform foveomacular dystrophy or Best Disease. (Lack of retinal abnormalities help differentiate these two conditions.) Central vision loss occurs gradually of the years with progressive atrophy of the central fovea. Laser photocoagulation is NOT advisable with this category. Small documented case studies have shown no benefits with laser treatments.
Parafoveal telangiectasis is distinctly different from secondary telangiectasis, which can result from other diseases. Noted common condition is branch vein obstruction. This can be distinguished from parafoveal telangiectasis by the area of involvement in the branch retinal vein occlusion effect on the entire capillary bed. Radiation retinopathy may result secondary to telangiectasis. The notable changes in radiation retinopathy are abnormal retinal areas with cotton-wool spots and retinal neovascularization. The history of irradiation of the eye will help distinguish this disease from parafoveal telangiectasis. Age-related macular degeneration is another, for which parafoveal telangiectasis may be mistaken, but can be differentiated by good quality fluorescein angiography.