Abstract
Purpose
To study right-angled vessels (RAV) in disease progression and macular neovascularization in type 2 macular telangiectasia (MacTel) eyes.
Methods
This retrospective image analysis study examined type 2 MacTel patients’ multicolour® and OCT imaging records from January 2015 to March 2023. Age, gender, laterality, visual acuity, systemic disease, and follow-up duration were recorded. RAV characteristics were assessed using OCT and multicolour® images. This study examined RAV characteristics and type 2 MacTel disease stage.
Results
In total, 270 eyes of 146 patients (97 females, 66%) with a mean age of 60.77 ± 9.34 years were studied. 153 (57%) eyes showed RAV. The non-proliferative stage of type 2 MacTel had either no RAV or a normal-calibre right-angled vein, while the proliferative stage had a right-angled artery and a dilated or normal-calibre RAV [p < 0.001]. RAV characteristics differed at the final follow-up (p < 0.001). 11 eyes transitioned from non-proliferative to proliferative after a median period of 26 months (range: 5–96 months). RAV characteristics changed from a normal calibre right-angled vein at presentation to a normal calibre vein and artery in 6 (55%) eyes and to a dilated vein and artery in 5 (45%) eyes respectively.
Conclusion
RAV characteristics may indicate type 2 MacTel stages. A right-angled artery in type 2 MacTel may indicate proliferative disease.
Subject terms: Predictive markers, Retinal diseases
Introduction
Classically, ‘type 2 macular telangiectasia’ (MacTel) has been described as an idiopathic, acquired, bilateral disease of the elderly that affects the macular Müller cells and deep retinal capillary network, is associated with changes in the inner and outer retinal structure, and finally leads to the development of abnormal neovascular complexes [1]. In 1993, based on clinical and angiographic findings, Gass and Blodi provided an updated clinical staging of type 2 MacTel into five stages, beginning with perifoveal greying, loss of retinal transparency, and presence of superficial retinal crystals as stage 2, and progressing to dilated right angled vessels (RAV) and retinal pigment clumps as stages 3 and 4, respectively, and development of subretinal neovascular membrane (SRNVM) as stage 5 [2]. Stage 1 of type 2 MacTel disease was characterised by the absence of classical clinical fundus findings, but showed the presence of diffuse temporal perifoveal leakage on fluorescein angiography. Yannuzzi et al streamlined the classification proposed by Gass and Blodi into two distinct stages: non-proliferative and proliferative [3].
In general, stages 1 and 2 of type 2 MacTel are regarded as early forms of the disease that do not affect vision, whereas stages 4 and 5 are regarded as more advanced stages of the disease that impair visual acuity [4, 5]. Consequently, the identification of RAV or stage 3 disease on clinical examination is crucial, as it may indicate a possible transition from a non-proliferative to a proliferative disease stage. Gass and Blodi’s classic description of a RAV is a blunted, slightly dilated venule that does not appear to taper towards the foveola, abruptly terminates, and appears to dive at a right angle into the deeper retinal layers [2]. Tzaridis et al. recently published a cross-sectional study in which they attempted to discuss in detail the characteristics of RAV in type 2 MacTel and its relevance with secondary macular neovascularisations [6]. The authors noted that RAVs could be detected as early as stages 1 and 2, and that their origin could be either arteriolar or venular. However, the study did not provide a more detailed description of the RAV in terms of changes in vessel size and origin as the disease progressed from a non-proliferative to a proliferative stage.
In this study, we evaluate the characteristics of RAV in disease progression and the development of macular neovascularisation, utilizing the readily available and routinely used imaging modalities for a precise understanding of the retinal micro and macrovasculature changes in eyes with type 2 MacTel.
Methods
In this retrospective image analysis study, we reviewed the clinical records of type 2 MacTel patients who underwent Multicolour® and OCT imaging on the Spectralis (Heidelberg Engineering, Germany) machine between January 2015 and March 2023. The study adhered to the principles of the Helsinki Declaration and was approved by the local Institutional Review Board/Ethics Committee (C-2023-03-003). Because the study involved a retrospective analysis of images, patient consent was waived.
On the basis of the characteristics described by Gass and Blodi [2], Type 2 MacTel was diagnosed clinically and confirmed with confocal blue reflectance imaging in all cases. On confocal blue reflectance imaging, the diagnosis of type 2 MacTel can be confirmed by revealing a parafoveal area of increased reflectance that usually encompasses an oval parafoveal area, but some sectors may be spared as well [7–9]. In type 2 MacTel, the clinical features included loss of retinal transparency and the presence of perifoveal greying, superficial retinal crystals without or with RAVs in the early stages of the disease, and the presence of intraretinal retinal pigment epithelium hyperplastic plaques with or without SRNVM in the advanced stages of the disease. In accordance with the Gass and Blodi classification [2], the presence of RAVs on clinical examination signifies the presence of disease in the third stage.
On the Spectralis (Heidelberg Engineering, Germany) device, Multicolour® imaging was performed using confocal scanning laser ophthalmoscope technology. A 30° or a 55° image was obtained. The diagnosis and staging of type 2 MacTel were based on the findings observed in individual reflectance channels of the Multicolour® imaging technology by two independent observers (AH and SPC) in accordance with the descriptions provided in our previous publication on Multicolour® imaging [9]. The blue reflectance channel showed the area of parafoveal increased reflectance to suggest the parafoveal greying and loss retinal transparency seen in the early non-proliferative stages of type 2 MacTel. Other clinical findings such as superficial retinal crystals, RAVs, and retinal pigment epithelial hyperplasia/plaques were equally identified on the blue and green reflectance channels with high sensitivities. Superficial retinal crystals were identified as bright white spots on the blue and green reflectance channels. The retinal vessels appear dark on the blue and green reflectance channels and thus, can be used to note the findings of RAV in type 2 MacTel. The retinal pigment epithelial plaques were noted as jet-black spots in the parafoveal region on the blue and green reflectance channels. The presence and extent of SRNVM seen in proliferative stage of type 2 MacTel is identified a bright white speckled lesion on the infrared reflectance channel. Certain images where the diagnosis of MacTel was questionable were clarified after consulting with the senior ophthalmologist (RV).
Conventionally, Gass and Blodi defined RAV on dilated fundus examination or on colour fundus photography as visible, blunted, dilated vessels (venules) that are primarily located in the temporal parafovea and do not appear to narrow towards the foveola, but rather abruptly dive into deeper retinal layers [1, 2]. Alternatively, retinal vessels in the MacTel region whose ends tapered or narrowed toward the fovea were not considered RAV. Two independent observers (AH and SPC), blinded for the clinical data of the patient, analysed all multicolour images of the study patients to detect the presence of type 2 MacTel and various other characteristics of RAV. On the enface confocal green and composite Multicolour® image, other characteristics of the RAVs, such as the calibre, dilatation, and its origin (whether artery or vein) were noted. The RAV was considered ‘dilated’ if its diameter was larger than the adjacent retinal vessels (venules or arterioles) in the macular region. When the size of the RAV was comparable to that of the adjacent retinal vessels in the macula, it was deemed to be of “normal” calibre. The RAV that entered the MacTel region was then traced back to the retinal arcades to determine whether it originated from a retinal artery or vein. Using the concept that oxygenated and deoxygenated blood have different light absorption properties, the retinal venule appeared darker on the confocal green reflectance image than the retinal arteriole. When the vessel’s origin could not be easily determined, particularly in a 30° enface image, this was one of the techniques used to confirm the source of the RAV [10–12]. Cases showing disagreement between the two observers were solved after consulting with the senior experienced ophthalmologist (RV) in the study. After reaching a consensus, the eyes were classified as having RAV or not having RAV. Observations of the multicolour® image identified three distinct patterns of RAVs. This includes (1) a normal calibre right-angled vein, (2) a normal calibre right-angled vein with a right-angled artery, and (3) a dilated right-angled vein with a right-angled artery.
Before the final evaluation of Multicolour® imaging scans by two independent observers (AH and SPC), a series of 30 test scans were initially provided by the senior ophthalmologist (RV) to each observer. The purpose of these scans was to assess the level of agreement between the two readers in identifying the presence of type 2 MacTel, as well as detecting the presence and different characteristics of RAV in type 2 MacTel. The spectral domain Spectralis (Heidelberg Engineering, Germany) device was used to evaluate macular volumetric OCT measurements consisting of 512 A-scans per line with a 30° scanning area and 25-line horizontal raster volume scans centred at the fovea. OCT scan with quality scores >15 was utilized for analysis and interpretation of the findings [13]. The OCT scans were evaluated primarily to confirm the presence of proliferative disease, specifically SRNVM. SRNVM was defined as the presence of an oval, fusiform hyperreflective lesion in the subretinal space above the retinal pigment epithelium with or without subretinal fluid or exudation. Another independent observer (AC) who was unaware of the multicolour® imaging results evaluated the OCT scans to determine whether or not SRNVM was present. After consulting with senior experienced ophthalmologist (RV) in the study, certain doubtful scans were clarified.
The clinical details of each patient were collected retrospectively by review of records, including age, gender, laterality, visual acuity and systemic disease if any and total follow-up duration. The OCT and Multicolour® images were evaluated for the RAV characteristics at various time points throughout the duration of the study, including at the initial presentation, at the time of development of RAV, during the transition from a non-proliferative to the proliferative MacTel stage, and at the final follow-up visit. During every visit, different RAV characteristics and Snellen’s visual acuity was recorded. The observers were not blinded to the imaging findings during the initial and final visits for patients undergoing longitudinal follow-up. The relationship between the various characteristics of the RAV and the stage of type 2 MacTel disease was analysed in this study.
Statistical tests
All data were analysed using GraphPad Prism version 9.5.1 (733) for Windows, GraphPad Software, San Diego, California USA, www.graphpad.com. The measurement of inter-rater agreement involved the calculation of the proportion of ‘matched’ responses between the two observers, expressed as a percentage of the total number of test scans that were graded. The Shapiro-Wilk normality test was used to test the normality of the data sets. The visual acuity was recorded using Snellen’s chart and then converted to logarithm of minimum angle of resolution (logMAR) units for statistical analysis. The Chi-square test was employed to compare the categorical data depicting the RAV characteristics between the non-proliferative and proliferative type 2 MacTel eyes. P values < 0.05 were considered statistically significant.
Results
Based on clinical examination, type 2 MacTel was identified in 292 eyes of 153 patients. At presentation, in 22 (8%) of these eyes, either the multicolour® or OCT image was of a poor quality. These eyes were consequently excluded from further analysis. The inter-rater agreement between the two readers for diagnosing type 2 MacTel was calculated to be 93%. Additionally, an inter-rater agreement of 84% was determined for detecting the various characteristics of RAV. Table 1 outlines the demographic characteristics of the remaining participants included in the study. Patterns of the RAVs seen at presentation are listed in Table 2 and Fig. 1.
Table 1.
Demographic characteristics of the type 2 MacTel study patients.
| Variable | Value |
|---|---|
| No. of patients | 146 |
| No. of eyes | 270 |
| Age (Mean ± SD) [years] | 60.77 ± 9.34 |
| Gender (females) [n, %] | 97 (66) |
| Laterality (RE: LE) | 132:138 |
| Presence of diabetes mellitus (n, %) | 110 (75) |
| Mean logMAR visual acuity (Snellen equivalent) | 0.381 ± 0.361 (20/48) |
| Presence of non-proliferative disease (n, %) | 223 (83) |
| Presence of proliferative disease (n, %) | 47 (17) |
SD standard deviation, RE right eye, LE left eye, logMAR logarithm of minimum angle of resolution.
Table 2.
Characteristics of RAV in the type 2 MacTel eyes at presentation.
| Non-proliferative MacTel (n = 223, 83%) | Proliferative MacTel (n = 47, 17%) | P value | |
|---|---|---|---|
| Absent RAV (n, %) | 70 (31) | 0 (0) | <0.001 |
| Normal calibre right-angled vein (n, %) | 150 (67) | 2 (4) | |
| Normal calibre right-angled vein and right-angled artery (n, %) | 1 (1) | 24 (51) | |
| Dilated right-angled vein and right-angled artery (n, %) | 2 (1) | 21 (45) |
MacTel macular telangiectasia, RAV right-angled vessel.
Fig. 1. Different characteristic features of right-angled vessel (RAV) in type 2 macular telangiectasia (MacTel).
The Fig. 1 demonstrates the appearance of the RAV in the different phases of type 2 MacTel on composite multicolour images, green reflectance images and optical coherence tomography images. Row 1 (A–D) shows the absence of the RAV seen as a venule with no blunted tips and directed towards the foveola (black arrows) in a non-proliferative disease stage. Row 2 (E–H) shows the presence of a right-angled vein of a normal vessel calibre (white arrows) in a non-proliferative type 2 MacTel eye. Row 3 (I–L) shows the presence of a right-angled vein with normal vessel calibre (blue arrow) and right-angled artery (white arrow) in a proliferative type 2 MacTel disease eye. Row 4 (M–P) demonstrates the presence of a right-angled artery (red arrow) and dilated right-angled vein (white arrow) in a proliferative type 2 MacTel eye. Zoomed multicolour images are shown in Figs. B, F, J, N.
Development of RAV
Twenty-five (36%) of the 70 eyes with no RAV at the initial presentation had follow-up information available. In 9 (36%) of the 25 eyes, RAV development was observed, manifesting as a normal calibre right-angled vein in a non-proliferative stage of type 2 MacTel after a median time interval of 46 months, ranging from 20 to 78 months. Table 3 provides useful details regarding the transition from no RAV to development of RAV stage.
Table 3.
Details of the cases showing transition from no RAV development to RAV development.
| Variable | Value |
|---|---|
| No. of eyes with no RAV at presentation | 70 |
| No. of eyes where details regarding follow-up details were available | 25 (36) |
| No. of eyes where RAV was noted at further follow-up visits | 9 (36) |
| Median time interval for the RAV development in these eyes (months) [Range] | 46 (20–78) |
| Non-proliferative stage of type 2 MacTel | 9 (100) |
| Mean logMAR visual acuity at the time of RAV development (Snellen equivalent) | 0.282 ± 0.087 (20/38) |
MacTel macular telangiectasia, RAV right-angled vessel, logMAR logarithm of minimum angle of resolution.
Conversion from non-proliferative to proliferative stage of type 2 MacTel
At initial presentation, 223 (83%) of 270 eyes were identified as having a non-proliferative stage of type 2 MacTel. In this study, follow-up information was available for 87 (39%) of these eyes. 11 eyes (13%) exhibited conversion from a non-proliferative to a proliferative stage of type 2 MacTel after a median time interval of 26 months, ranging from 5 to 96 months. The average logMAR visual acuity of these eyes developing the SRNVM was 20/79 on the Snellen scale. The RAV characteristics changed from a normal calibre right-angled vein at presentation to a normal calibre right-angled vein and artery in 6 (55%) eyes and to a dilated right-angled vein and artery in 5 (45%) eyes respectively. Supplementary Table 1 depicts the necessary study information regarding this group of cases.
Details at the last follow-up visit of the entire cohort of MacTel study patients
In this study, follow-up information was available for 116 (43%) of 270 eyes diagnosed with type 2 MacTel. The duration of follow-up was 43.73 ± 36.45 months on average. 0.41 ± 0.285 (20/51) was the mean logMAR visual acuity. In 77 (66%) eyes, the non-proliferative stage of type 2 MacTel was observed, and in 39 (34%) eyes, the proliferative stage was observed. Supplementary Table 2 and Fig. 2 lists the characteristics of the RAV at the final follow-up visit.
Fig. 2. Changes in the characteristics of right-angled vessel (RAV) over transition from a non-proliferative to a proliferative type 2 macular telangiectasia (MacTel) disease stage.
This figure depicts the evolution of the clinical characteristics of the RAV on enface retinal imaging with composite multicolour images and green reflectance images, as well as on optical coherence tomography (OCT) images, in an eye with type 2 MacTel disease. Row 1 (A–D) depicts a normal-sized, retinal vein (blue arrow) in a type 2 non-proliferative MacTel at presentation to the retina clinic. Row 2 (E–H) illustrates the changes in clinical presentation over a six-month period. It depicts the visibility of a right-angled artery (red arrow) and a normal-sized right-angled vein (blue arrow) during the proliferative phase of a disease. Row 3 (I–L) represents the clinical findings three years after the initial presentation. In this image, in addition to the right-angled artery (red arrow) and vein (blue arrow) being visible, the vein appears dilated and prominent. With the development of outer retinal cavitation at the fovea, the OCT scan displays a progressive change. Row 4 (M–P) represents the clinical findings five years after the initial presentation. Currently, there is a progressive increase in the size of the neovascular membrane, as well as the right-angled artery (red arrow) and a prominently dilated right-angled vein (blue arrow). This figure depicts the longitudinal changes observed over time in an eye from the non-proliferative to proliferative disease stage in the type 2 MacTel study eye. Zoomed multicolour images are shown in (B, F, J, N).
Discussion
This study analysed the characteristics of RAV in the non-proliferative and proliferative phases of type 2 MacTel. The study made pertinent observations regarding the various characteristics of RAV, such as its presence, origin, and vessel dilatation in different stages of type 2 MacTel. According to the findings of this study, a RAV was observed in all proliferative disease-stage eyes. The RAV was characterized by the presence of a right-angled artery and a normal-sized or dilated right-angled vein during the proliferative disease stage. In the non-proliferative stages of the disease, either no RAV or a normal-sized right-angled vein was observed. Eyes displaying progression from a non-proliferative to a proliferative disease stage exhibited alterations in RAV characteristics, such as the presence of a right-angled artery and vein. Such observations on RAV in type 2 MacTel have not yet been published, according to our research.
In type 2 MacTel, the detection of stage 3 disease or RAV is vital because it indicates a potential shift from a non-proliferative to a proliferative stage in the future. Multiple enface retinal imaging modalities can detect the RAV. These include the use of invasive dye-based imaging techniques like fluorescein angiography or non-invasive techniques like colour fundus photography, pseudo-colour Multicolour® imaging, fundus autofluorescence imaging, and OCT angiography [9, 14–16]. In this study, Multicolour® imaging was used to detect the RAV due to its ability to confirm type 2 MacTel, to produce better quality images due to the use of scanning laser ophthalmoscopy technology, and to provide superior ability to distinguish between a vein and an artery due to the differential light absorption properties of deoxygenated blood in the vein and oxygenated blood in the artery.
Gass and Blodi first described a RAV as a blunted, dilated venule that abruptly terminates and dives deep into the outer retinal layers in the MacTel region. Tzaridis et al. demonstrated in a recent study using early-phase fluorescein angiography that the origin of the RAV could be either arteriolar or venular [6]. Our findings differed from those reported by Tzaridis et al. In both stages of MacTel, the origin of a RAV was primarily venular, as was observed. However, a right-angled artery was frequently observed in the proliferative stage of type 2 MacTel disease.
Our study’s observations on the RAV could assist in understanding the disease’s pathogenesis and progression from a non-proliferative to a proliferative phase. Draining the retinal capillaries is the primary function of the retinal venules. In the early stages of type 2 MacTel disease, which is characterized by the loss of macular perifoveal Müller cells and macular carotenoids (lutein and zeaxanthin), the deep retinal telangiectatic capillaries and the retinal venule that drains these capillaries become more visible [17, 18]. However, the retinal venule gradually tapers toward the foveola and does not abruptly descend into the outer retinal layers. Therefore, a right-angled venule is not observed in the early stages of type 2 MacTel. As the damage and degeneration of Müller cells progresses, the deep retinal telangiectatic capillaries lose their structural support, resulting in the capillaries’ migration toward the outer retina. On OCT, this appears as an outward bending of the perifoveal inner retinal layers, as described in a prior publication by our group [19]. As the deep retinal telangiectatic capillaries descend toward the outer retina, the accompanying draining retinal venule follows the same path. On enface retinal imaging, it appears that the retinal venule has abruptly terminated and has blunted tips, giving the appearance of a normal-sized, right-angled venule. This is the third stage of type 2 MacTel disease. With the development of right-angled venule, the progression of the disease continues, leading to inner retinal disorganization, outer retinal cavities, and disruption of the ellipsoid zone. This promotes two series of events: (1) exposure of the retinal pigment epithelium pigments and their migration to the inner retina (stage 4 disease) and/or (2) stimulation of the damaged retinal telangiectatic capillaries to proliferate into new abnormal capillaries (neovascular complexes), referred to as intra retinal neovascularisation. In the second scenario, in which abnormal neovascular capillaries develop in the retinal layers, the retinal arteriole supplies these additional capillaries. Thus, it is observed that the retinal arteriole dips perpendicularly towards the outer retina, supplying the new abnormal capillaries. Consequently, the right-angled arteriole and normal-sized right-angled venule are observed at this stage. As the disease progresses, the intraretinal neovascularization proliferates and invades the subretinal space, forming an SRNVM [1]. Due to the neovascular process, the right-angled venule must drain more blood from the capillaries than usual at this stage. This causes a dilated right-angled venule and a right-angled arteriole during the proliferative stage of the disease.
This study’s findings could lead to the development of an alternative treatment for type 2 proliferative MacTel. Direct laser photocoagulation of RAVs (primarily arterioles) could cut off the blood supply to neovascular complexes and promote their regression. A recent case report from our group demonstrated the advantages of direct laser photocoagulation to the RAVs in type 2 MacTel by successfully achieving macular neovascularisation inactivity for a long period [20]. Due to the extrafoveal location of the RAVs supplying the macular neovascularization, this treatment alternative may be safe.
The strengths of the current study are the large cohort of cases from a single centre, imaged on the same Spectralis machine for OCT and Multicolour® imaging throughout the duration of the study, thereby ensuring consistency in imaging findings across the various disease stages. This paper also examines the changes in RAV characteristics upon progression from the non-proliferative to the proliferative disease stage, as well as the longitudinal data of patients with type 2 MacTel. There are a number of limitations associated with this study. The study’s most significant limitation is its retrospective design, diverse cohort of patients with type 2 MacTel disease at follow-up visits, and unavailability of fluorescein angiography, fundus autofluorescence, and OCTA in all cases.
Finally, the detection of various RAV characteristics may indicate various stages of type 2 MacTel. Identification of a right-angled artery in type 2 MacTel could indicate a proliferative disease process.
Supplemental material is available at Eye’s website.
Summary
What was known before:
Type 2 macular telangiectasia (MacTel) is an idiopathic, non-familial, bilateral disease of the elderly that affects the macular perifoveal Müller cells and microvascular deep capillary network.
It causes abnormal neovascular complexes by altering inner and outer retinal structure.
Dilated right-angled veins are currently described in the type 2 non-proliferative MacTel disease.
Right-angled vessels and its relation to the development of neovascular complexes is currently underexplored.
What this study adds:
Different characteristics of right-angled vessels is noted at different stages of type 2 MacTel.
Both retinal artery and retinal vein can show right-angled dipping in type 2 MacTel.
Presence of right-angled artery indicates a possible proliferative disease stage.
Supplementary information
Author contributions
RV, JC, VP—conceptualising the study, data acquisition, analysing the data, statistics and results, interpreting the findings, writing & reviewing the manuscript. AC, AH, SPC, ISA, RB—Data acquisition and analysing the data. NKY—critically reviewing the manuscript.
Data availability
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
The online version contains supplementary material available at 10.1038/s41433-023-02853-w.
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Associated Data
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Supplementary Materials
Data Availability Statement
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.