A new diagnostic approach in patients with type 2 macular telangiectasia: confocal reflectance imaging

Editor, Type 2 idiopathic macular telangiectasia (type 2 IMT) usually presents with a slow decrease in visual acuity in the fifth to seventh decade. This typically bilateral disease is characterized by occult, parafoveolar telangiectasis and minimal exudation that may be visible on fluorescein angiography only (Gass & Blodi 1993; Charbel Issa et al. 2007a). Typical clinical findings are located predominantly in the temporal parafovea and include a reduction of parafoveal retinal transparency, superficial retinal crystalline deposits, dilated blunted venules. Functional deterioration is predominantly due to foveal atrophy, intraretinal pigment proliferation or development of neovascular membranes (Charbel Issa et al. 2007b). Diagnosis is usually confirmed by invasive fluorescein angiography. We present findings in two patients with type 2 IMT using non-invasive blue (488 nm) and infrared (820 nm) reflectance imaging with a confocal scanning laser ophthalmoscope (cSLO; HRA2, Heidelberg Engineering, Heidelberg, Germany). The images are compared to findings of fluorescein angiography and digital fundus photography. Patient 1 (female, 65 years) had a visual acuity of 20/80 in the right eye and 20/63 in the left eye. There was slight parafoveal greying bilaterally and a dilated blunted venule in the upper temporal quadrant of the macula in the left eye. Patient 2 (male, 54 years) presented with a visual acuity of 20/63 in the right eye and 20/200 in the left eye. He had an advanced disease with intraretinal pigment proliferation in both eyes and a secondary vascular membrane in the left eye. In both patients, red-free imaging (Zeiss FF450 fundus camera; Zeiss, Oberkochen, Germany; filter with a transmission range of 515–575 nm) highlighted the dilated right-angled venules and enabled the visualization of small ectatic parafoveal capillaries (Fig. 1D,J). Retinal crystals in patient 2 appeared to follow the topography of retinal nerve fibres, suggesting a superficial location of these deposits. Left eye of a patient (#1) representing an early stage and right eye of a patient (#2) representing a late disease stage of type 2 idiopathic macular telangiectasia. The right eye in patient 1 was similar to the left eye. In patient 2, macular appearance in the left eye was changed because of a neovascular membrane. Upper row: fluorescein angiography showing ectatic parafoveal capillaries in the early phase (A, G) and diffuse parafoveal leakage in the late phase at 10 min after dye injection (B, H). Middle row: colour fundus image (C, I) showing a slight loss of parafoveal retinal transparency and a dilated blunted venule temporal to the fovea in patient 1 (C). In the right eye of patient 2 (I), loss of parafoveal retinal transparency, dilated blunted venules temporal to the fovea, retinal crystalline deposits and intraretinal pigment clumping are present. Red-free fundus photography using a filter (D, J) enabled visualization of small ectatic parafoveal capillaries. Lower row: confocal blue reflectance imaging (E, K) shows an oval parafoveal area of increased reflectance. Confocal infrared reflectance (F, L) reveals an area of slightly patchy reflectance in patient 1 and an oval-shaped decreased reflectance in patient 2. The changes in confocal reflectance imaging (E, F, K, L) are topographically related to the leakage in late-stage angiography (B, H). In both patients, confocal blue reflectance imaging (Fig. 1E,K) using the cSLO disclosed a well-defined area of increased reflectance topographically related to the leakage in late-phase angiography (Fig. 1B,H). Infrared reflectance (Fig. 1F,L) showed a uniform reflectance in patient 1 and a decreased reflectance in patient 2. The latter again coincided with the area of leakage in late-phase angiography. Spectral narrowing of the fundus illumination by using filters may reduce chromatic aberrations and enhance the contrast and resolution of details. Small retinal vessels are best imaged at wavelengths of 510–570nm (Delori et al. 1977). The use of an appropriate filter enhanced the visualization of the parafoveal ectatic vascular changes in type 2 IMT. Macular imaging by cSLO technique allows the detection of light from a conjugate plane and decreases artefacts by stray light (Jorzik et al. 2005). Increased confocal reflectance at 488 nm may be explained by decreased light absorption and/or increased reflection in the retina. These retinal areas are related to the area of leakage in late-phase fluorescein angiography and hence may provide information as to the extent of the macular area involved. Since alterations in type 2 IMT can be detected in an early disease stage (patient 1) using confocal blue reflectance imaging, this imaging modality might be helpful in the early detection of the disease. Because confocal infrared reflectance imaging showed major changes only in patient 2 (who represents a later disease stage), this imaging mode may rather be suitable for follow-up in patients with type 2 IMT. In summary, spectral narrowing in fundus photography using red filters as well as confocal blue reflectance imaging may contribute to the detection of type 2 IMT. Furthermore, confocal reflectance imaging may be useful in estimating the extent of the macular area involved. Larger studies are needed to assess the value of these imaging techniques in type 2 IMT for the purposes of staging and monitoring the disease course. Supported by The Lowy Medical Foundation (The Macular Telangiectasia Project, http://www.mactelresearch.org), Deutsche Forschungsgemeinschaft Heisenberg fellowship (SCHO 734/2-1): EU FP6, Integrated Project ‘EVI-GENORET’ (LSHG-CT-2005-512036).