Macular Edema Associated with Idiopathic Telangiectasias and Macroaneurysm
Peter Liggett
Nauman Chaudry
PARAFOVEAL TELANGIECTASIS
“Retinal telangiectasis” is a term first proposed by Reese in 1956 (1) to describe a retinal vascular disorder associated with ectasia and irregular dilation of capillaries in the macula or peripheral retina. Fundoscopic and fluorescein angiographic findings of eyes with loss of macular function associated with retinal telangiectasis have been well described by Gass (2) in 1968. The term “parafoveal telangiectasis” (PT), however, first was used in 1978 by Hutton and colleagues (3), describing the presence of dilated capillaries in the juxtafoveal area. The cause of this condition is unknown; Gass & Oyakama (4) termed this condition “idiopathic juxtafoveal retinal telangiectasis” and divided the disease into several groups based on clinical findings and the purported underlying cause. Gass (2) proposed that in some patients, the telangiectatic capillaries were of congenital or developmental origin (a variant of Coat’s disease), whereas in others, they were an acquired anomaly. Gass and Blodi (5) later modified the original classification system and sub-divided the group into three categories (Table 25-1).
EPIDEMIOLOGY
PT is a relatively rare condition, and precise incidence and prevalence figures have not been established. Patients typically first present in adulthood with decreased vision or scotoma in one or both eyes. Patient characteristics differ for each of these subgroups proposed by Gass and Blodi (Table 25-1). Group 1 patients are usually male and typically have only one eye involved. Patients with group 2 or 3 disease are older and typically have bilateral disease. Both males and females are affected with equal frequency with group 2 disease. Group 3A patients are typically women, whereas group 3B patients are usually men.
A familial tendency may be present in some subtypes (2B, 3A, 3B) (5), and one case of father-to-son transmission of PT has been reported (6).
TABLE 25-1 PARAFOVEAL TELANGIECTASIS CLASSIFICATION (4) | |||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
CONGENITAL PARAFOVEAL TELANGIECTASIS
The common finding on fluorescein angiography in all three groups is the presence of retinal capillary telangiectasis localized to the parafoveal region. Other features are typical (Table 25-1) of a particular group.
Group 1A: Unilateral Congenital Parafoveal Telangiectasis
Group 1A consists typically of men whose mean age at onset of the disease is 40 years. Only one eye is involved in these patients. The telangiectatic vessels are confined to the temporal parafoveal region, and the zone of involvement typically straddles the horizontal raphe (Fig. 25-1A-B). In patients with subtype 1A, the zone of involvement is usually one to two disc diameters in size. The telangiectatic vessels appear as microaneurysmal or saccular dilation of retinal capillaries and are visible biomicroscopically. Retinal capillary leakage is believed to be the principal abnormality in these eyes, and thus exudation is a prominent feature. Lipid exudates are often present at the margin of the zone of telangiectasis. Macular edema and exudation are the major causes of visual loss in these eyes. Visual acuity at presentation usually ranges from 20/25 to 20/40, although 20/200 may occur.
ACQUIRED PARAFOVEAL TELANGIECTASIS
Group 1B: Unilateral Idiopathic Parafoveal Telangiectasis
According to Gass (2), idiopathic PT (IPT) is found in middleaged men who have more localized disease, with less than two clock hours of telangiectasis. The foveal avascular zone (FAZ)
may be significantly smaller in these patients. Mansour and Schachat (7) found that the FAZ was almost completely vascularized in 65% of eyes with IPT studied by fluorescein angiography. The median FAZ in eyes with Group 1 PT was 0.0 mm2 compared with 0.405 mm2 in control eyes. Rarely does this area of telangiectasis have much leakage on fluorescein angiography. Visual acuity is usually better than 20/25.
may be significantly smaller in these patients. Mansour and Schachat (7) found that the FAZ was almost completely vascularized in 65% of eyes with IPT studied by fluorescein angiography. The median FAZ in eyes with Group 1 PT was 0.0 mm2 compared with 0.405 mm2 in control eyes. Rarely does this area of telangiectasis have much leakage on fluorescein angiography. Visual acuity is usually better than 20/25.
 Figure 25-1. Group 1A unilateral congenital parafoveal telangiectasis and macular edema. A: Left eye. B: Late phase fluorescein angiography. |
Group 2: Bilateral Acquired Parafoveal Telangiectasis
This is the most common form of IPT. Men and woman are affected equally, and the disease is nearly always bilateral. The telangiectatic capillaries are difficult to see biomicroscopically and often require fluorescein angiography for detection. The telangiectasis always involves the entire parafoveal retina. Multiple refractile, glistening deposits may be seen in the superficial retina overlying the zone of telangiectasis (8). A round yellow spot, 100-300 microns in size, may be present in the foveal center in some eyes.
Gass has described five stages in eyes with Group 2 IPT (5). In the first stage, there is minimal or no evidence of retinal telangiectasis, with only mild staining at the level of the outer parafoveal retina in the late phase of the fluorescein angiography. Stage 3 is characterized by the appearance of dilated venules that extend at right angles from the inner to the outer retina. The right angle venules may appear to drain the outer telangiectatic retinal capillary bed. In stage 4, retinal pigment epithelial hyperplasia develops. The hyperplastic retinal pigment epithelium may form intraretinal pigment plaques and may surround the right angle venules. In stage 5, subretinal neovascularization (SRNV) and fibrosis (Fig. 25-2) develop, typically in the region of intraretinal pigment epithelial migration. SRNV occurs in approximately 14% of eyes with Group 2 IPT. Optical coherence tomography (OCT) has provided further insight into the retinal thickness at the different stages of the natural course of the disease. It appears that, in the presence of retinal staining with fluorescein angiography, there may be no associated retinal thickening. Albani et al. (9) reported the presence of foveal cysts revealed by OCT in stage 3 IPT, but no correlation with fluorescein angiogram was found. Paunescu et al. (10) reported the following OCT features of IPT: a lack of correlation between retinal thickening on OCT and leakage on fluorescein angiography; loss of disruption of the photoreceptor layer; cystlike structures in the fovea and within the internal layers; a unique internal limiting membrane draping across the fovea related to underlying loss of tissue; intraretinal neovascularization near the fovea; and, central intraretinal deposits and plaques.
