Alan C. Bird

Macular telangiectasia type 2

Macular telangiectasia type 2 is a bilateral disease of unknown cause with characteristic alterations of the macular capillary network and neurosensory atrophy. Its prevalence may be underestimated and has recently been shown to be as high as 0.1% in persons 40 years and older. Biomicroscopy may show reduced retinal transparency, crystalline deposits, mildly ectatic capillaries, blunted venules, retinal pigment plaques, foveal atrophy, and neovascular complexes. Fluorescein angiography shows telangiectatic capillaries predominantly temporal to the foveola in the early phase and a diffuse hyperfluorescence in the late phase. High-resolution optical coherence tomography (OCT) may reveal disruption of the photoreceptor inner segment-outer segment border, hyporeflective cavities at the level of the inner or outer retina, and atrophy of the retina in later stages. Macular telangiectasia type 2 shows a unique depletion of the macular pigment in the central retina and recent therapeutic trials showed that such depleted areas cannot re-accumulate lutein and zeaxanthin after oral supplementation. There have been various therapeutic approaches with limited or no efficacy. Recent clinical trials with compounds that block vascular endothelial growth factor (VEGF) have established the role of VEGF in the pathophysiology of the disease, but have not shown significant efficacy, at least for the non-neovascular disease stages. Recent progress in structure-function correlation may help to develop surrogate outcome measures for future clinical trials. In this review article, we summarize the current knowledge on macular telangiectasia type 2, including the epidemiology, the genetics, the clinical findings, the staging and the differential diagnosis of the disease. Findings using retinal imaging are discussed, including fluorescein angiography, OCT, adaptive optics imaging, confocal scanning laser ophthalmoscopy, and fundus autofluorescence, as are the findings using visual function testing including visual acuity and fundus-controlled microperimetry. We provide an overview of the therapeutic approaches for both non-neovascular and neovascular disease stages and provide a perspective of future directions including animal models and potential therapeutic approaches.

Consensus Definition for Atrophy Associated with Age-Related Macular Degeneration on OCT Classification of Atrophy Report 3

PURPOSEnTo develop consensus terminology and criteria for defining atrophy based on OCT findings in the setting of age-related macular degeneration (AMD).nnnDESIGNnConsensus meeting.nnnPARTICIPANTSnPanel of retina specialists, image reading center experts, retinal histologists, and optics engineers.nnnMETHODSnAs part of the Classification of Atrophy Meetings (CAM) program, an international group of experts surveyed the existing literature, performed a masked analysis of longitudinal multimodal imaging for a series of eyes with AMD, and reviewed the results of this analysis to define areas of agreement and disagreement. Through consensus discussions at 3 meetings over 12 months, a classification system based on OCT was proposed for atrophy secondary to AMD. Specific criteria were defined to establish the presence of atrophy.nnnMAIN OUTCOME MEASURESnA consensus classification system for atrophy and OCT-based criteria to identify atrophy.nnnRESULTSnOCT was proposed as the reference standard or base imaging method to diagnose and stage atrophy. Other methods, including fundus autofluorescence, near-infrared reflectance, and color imaging, provided complementary and confirmatory information. Recognizing that photoreceptor atrophy can occur without retinal pigment epithelium (RPE) atrophy and that atrophy can undergo an evolution of different stages, 4 terms and histologic candidates were proposed: complete RPE and outer retinal atrophy (cRORA), incomplete RPE and outer retinal atrophy, complete outer retinal atrophy, and incomplete outer retinal atrophy. Specific OCT criteria to diagnose cRORA were proposed: (1) a region of hypertransmission of at least 250 μm in diameter, (2) a zone of attenuation or disruption of the RPE of at least 250 μm in diameter, (3) evidence of overlying photoreceptor degeneration, and (4) absence of scrolled RPE or other signs of an RPE tear.nnnCONCLUSIONSnA classification system and criteria for OCT-defined atrophy in the setting of AMD has been proposed based on an international consensus. This classification is a more complete representation of changes that occur in AMD than can be detected using color fundus photography alone. Longitudinal information is required to validate the implied risk of vision loss associated with these terms. This system will enable such future studies to be undertaken using consistent definitions.

Progression of Vision Loss in Macular Telangiectasia Type 2

PURPOSEnTo investigate progressive vision loss in patients with macular telangiectasia (MacTel) type 2 and to compare the ability to detect functional decline between microperimetry and visual acuity testing.nnnMETHODSnChange of cumulative defect size (number of test points with absolute scotoma) on microperimetry testing and change in distance best-corrected visual acuity (BCVA) were evaluated in a prospective longitudinal observational study.nnnRESULTSnThe mean review period was 55.3 months (SD 17.3 months). In 58% of 71 eyes (40 patients) included for analysis, microperimetry revealed spread (n = 31) or new development (n = 10) of an absolute scotoma. At the same time, BCVA decreased more than two lines in only 17% (n = 12). Twenty-five (35%) eyes showed no change in visual function. Presence of an absolute scotoma at baseline, but not baseline BCVA, was predictive for functional decline on longitudinal microperimetry testing. Eyes with an absolute scotoma at baseline (n = 33) showed further growth of the scotoma in 94% (n = 31). In contrast, only 26% (n = 10) of eyes without an absolute scotoma at baseline (n = 38) developed an absolute scotoma de novo. Scotoma growth rate (new test points with an absolute scotoma per year) was 0.62 ± 0.10 for all eyes and 1.30 ± 0.12 for the subgroup of eyes with scotoma at baseline. Scotomata always first occurred in the quadrant temporal to the foveal center.nnnCONCLUSIONSnA characteristic feature in patients with MacTel type 2 is progressive focal loss of macular sensitivity, preceding loss of visual acuity. Microperimetry is sensitive to detect such functional decline and thus may provide considerable power when being used as a functional outcome measure in future clinical trials.

A Population-Based Ultra-Widefield Digital Image Grading Study for Age-Related Macular Degeneration–Like Lesions at the Peripheral Retina

PURPOSEnOur understanding of the relevance of peripheral retinal abnormalities to disease in general and in age-related macular degeneration (AMD) in particular is limited by the lack of detailed peripheral imaging studies. The purpose of this study was to develop image grading protocols suited to ultra-widefield imaging (UWFI) in an aged population.nnnDESIGNnA cross-sectional study of a random population sample in which UWFI was introduced at the 12-year review of the Reykjavik Eye Study in Iceland.nnnPARTICIPANTSnFive hundred seventy-six subjects 62 years of age or older.nnnMETHODSnUltra-widefield (up to 200°) color and autofluorescence images were obtained using the Optos P200CAF laser scanning ophthalmoscope (Optos plc, Dunfermline, Scotland). The images were graded at Moorfields Eye Hospital Reading Centre primarily based on the International Classification for AMD. Macular and peripheral changes were graded using a standardized grid developed for this imaging method.nnnMAIN OUTCOME MEASURESnPresence or absence of hard, crystalline, and soft drusen; retinal pigment epithelial changes; choroidal neovascularization (CNV); atrophy; and hypoautofluorescence and hyperautofluorescence were graded in the peripheral retina.nnnRESULTSnOf the eyes examined, 81.1% had AMD-like changes in the macula alone (13.6%), periphery alone (10.1%), and both periphery and macula (57.4%). There was no AMD-like CNV or pigment epithelial detachment in the periphery except in those cases in which these clearly originated from the macula. Seven patients had AMD-like atrophy in the periphery without end-stage disease in the macula. One patient with end-stage disease in the macula had normal periphery results on the color images. While analyzing the eyes, we detected pathologic appearances that were very reliably identified by graders.nnnCONCLUSIONSnPhenotyping the retinal periphery using the categories defined by the International Classification confirmed the presence of wide-ranging AMD-like pathologic changes even in those without central sight-threatening macular disease. Based on our observations, we propose here new, reliably identifiable grading categories that may be more suited for population-based UWFI.

ABNORMAL RETINAL REFLECTIVITY TO SHORT-WAVELENGTH LIGHT IN TYPE 2 IDIOPATHIC MACULAR TELANGIECTASIA

Purpose: Macular telangiectasia Type 2 (MacTel) is a bilateral, progressive, potentially blinding retinal disease characterized by vascular and neurodegenerative signs, including an increased parafoveal reflectivity to blue light. Our aim was to investigate the relationship of this sign with other signs of macular telangiectasia Type 2 in multiple imaging modalities. Methods: Participants were selected from the MacTel Type 2 study, based on a confirmed diagnosis and the availability of images. The extent of signs in blue-light reflectance, fluorescein angiographic, optical coherence tomographic, and single- and dual-wavelength autofluorescence images were analyzed. Results: A well-defined abnormality of the perifovea is demonstrated by dual-wavelength autofluorescence and blue-light reflectance in early disease. The agreement in area size of the abnormalities in dual-wavelength autofluorescence and in blue-light reflectance images was excellent: for right eyes: &rgr; = 0.917 (P < 0.0001, 95% confidence interval 0.855–0.954, n = 46) and for left eyes: &rgr; = 0.952 (P < 0.0001, 95% confidence interval 0.916–0.973, n = 49). Other changes are less extensive initially and expand later to occupy that area and do not extend beyond it. Conclusion: Our findings indicate that abnormal metabolic handling of luteal pigment and physical changes giving rise to increased reflectance are widespread in the macula throughout the natural history of the disease, precede other changes, and are relevant to early diagnosis.

Why the macula

The regional susceptibility of the retina to diseases has been well known by clinicians for many years. It is surprising that the implications of these observations have not spawned major research efforts to characterise the structural and functional attributes of the outer retina in different regions of a foveate retina. Without such an effort, the understanding of the disease mechanisms in retinal dystrophies will remain limited and may hamper therapeutic efforts. That outer retinal disease is responsible for over 50% of blind registration in the western world underlines the importance of these considerations.

SCOTOMA CHARACTERISTICS IN MACULAR TELANGIECTASIA TYPE 2: MacTel Project Report No. 7-The MacTel Research Group.

Purpose: To characterize scotomas in macular telangiectasia Type 2 (MacTel). Methods: Five of the 27 centers performed microperimetry as part of the MacTel Natural History Observation Study. Data were analyzed in the Moorfields Eye Hospital Reading Centre. The number of stimuli under a threshold of 12, 10, 8, and <0 dB were counted (thresholding) and compared with one another. Results: A total of 565 examinations were gradable, received from 632 eyes of 322 participants (age 61.1 ± 9.1 years, 62% females). The authors found absolute scotomas in 243 eyes (43%), 98% of these affected the temporal quadrant, and 99.5% were unifocal. Growth of absolute scotomas was limited to an extent of approximately 40 deg2. Although transition from functionally unimpaired retina to absolute scotomas is generally steeply sloped, the larger a scotoma, the steeper it is. Conclusion: Scotoma features were consistent throughout a large MacTel cohort. The temporal quadrant was confirmed as predominantly affected, which might result from vascular or metabolic asymmetry. Functional loss did not exceed an area of 5° × 8° however advanced the disorder. Different MacTel phenotypes seem likely and point toward different types of progression; identifying these would improve planning for clinical trials and might lead to better understanding patient outcome.

CORRELATION OF STRUCTURAL AND FUNCTIONAL OUTCOME MEASURES IN A PHASE ONE TRIAL OF CILIARY NEUROTROPHIC FACTOR IN TYPE 2 IDIOPATHIC MACULAR TELANGIECTASIA

Purpose: Macular telangiectasia Type 2 is a bilateral, progressive, potentially blinding retinal disease characterized by both vascular and neurodegenerative signs. Both the area of the break in the ellipsoid zone seen in “en face” optical coherence tomographic (OCT) images and microperimetric focal retinal sensitivity loss have been proposed as potential measures of progression in macular telangiectasia. The authors aimed to assess the characteristics and interrelationship of these structural and functional disease markers from the data collected in a phase one clinical trial of ciliary neurotrophic factor in macular telangiectasia. Methods: Orthogonal topographic (en face) maps of the ellipsoid zone were generated from Heidelberg Spectralis OCT volume scans (15 × 10° area, 30-&mgr;m B-scan intervals) or Zeiss Cirrus HD-OCT 4000 512 × 128 cube scans. Mesopic microperimetry was performed on CenterVue MAIA perimeters, using a Goldmann III stimulus in a custom test grid. Structural and functional data were analyzed by two methods: by calculating aggregate loss and by simple thresholding. The alignment quality of structural and functional data was also evaluated. Results: Overall, the break area showed a good correlation with aggregate sensitivity loss (&rgr; = 0.834, P < 0.0001, 95% confidence interval 0.716–0.906) but also with the number of test points below a threshold value (e.g., <20 dB: &rgr; = 0.843, P < 0.0001, 95% confidence interval 0.755–0.902). Significant misalignment of the MAIA test grid was apparent in 13/48 visits of 7/14 eyes. Conclusion: The authors found a good correlation between ellipsoid zone break area and function loss. En face OCT mapping of the ellipsoid zone appears to demonstrate structural change before mesopic microperimetry can detect a focal loss of retinal sensitivity. Thresholding offers a quick alternative to calculating aggregate sensitivity loss.

LONGITUDINAL CORRELATION OF ELLIPSOID ZONE LOSS AND FUNCTIONAL LOSS IN MACULAR TELANGIECTASIA TYPE 2

Purpose: To compare ellipsoid zone (EZ) loss and functional loss in macular telangiectasia (MacTel) type 2 longitudinally. Methods: Prospective natural history study. Ellipsoid zone loss was measured in en-face images created from spectral domain optical coherence tomography. Functional loss was assessed by best-corrected visual acuity and microperimetry, counting the number of test points with impaired function. Results: A total of 56 eyes of 31 participants were followed for 4.5 ± 1.2 years. Ellipsoid zone loss was 18,600 ± 3,917.3 pixel at baseline (≈0.59 mm2) and increased 2,627.8 ± 427.9 pixel (≈0.08 mm2) per year. Best-corrected visual acuity decreased 2.2 ± 0.9 letters per year. Change in EZ loss correlated significantly with change in relative and absolute scotomas (r = 0.62; P-value < 0.0001 and r = 0.72; P-value < 0.0001), but not with loss of best-corrected visual acuity. Functional loss showed a similar frequency of progression as EZ loss, but a higher rate of “regression,” likely due to higher variability of the measurement, assuming a progressive neurodegenerative disease. Conclusion: The results of the authors support EZ loss as surrogate measure for visual function in MacTel type 2. Being objective, EZ loss might be considered more suitable than microperimetry as primary end point in future interventional trials.

CHARACTERISTICS OF PIGMENTED LESIONS IN TYPE 2 IDIOPATHIC MACULAR TELANGIECTASIA

Purpose: Pigment in the midretina is a characteristic sign in Type 2 idiopathic macular telangiectasia (MacTel) and is considered to characterize the late stage of the disease. Our aim was to investigate its incidence, and relationship with risk factors for MacTel, including outer retinal vascularization and subretinal neovascular proliferation (SRNV). Methods: Pigment extent was measured in fundus autofluorescence images of 150 eyes of 75 MacTel probands, using the Region Finder tool of Heidelberg Eye Explorer. A linear mixed model was used to analyze the dynamics of pigment and its associations with other features of the phenotype. The relative incidence of pigment and of outer retinal outer retinal vascularization and SRNV was analyzed within the full MacTel Study cohort (1,244 probands). Results: Mean pigment area at baseline was 0.157 mm2 (range = 0–1.295 mm2, SD = 0.228 mm2, n = 101). Progression demonstrated a nonlinear pattern (P < 0.001) at an overall rate of 0.0177 mm2/year and was associated with the initial plaque size and with SRNV. There was a strong correlation between fellow eyes (P ⩽ 0.0001). In approximately 25% of all SRNV cases, SRNV may coincide with or precede pigment. Conclusion: Our data may be useful for refining the current system for staging disease severity in MacTel.