Gass Atlas of Macular Diseases: 1-2

Also, diabetes mellitus and hypertension could lead to increased vulnerability of the macular vasculature for the eponymous vascular alterations. It had been proposed already in earlier studies that diabetes mellitus may be associated with the disease Chew et al. However, others suggested that the association would not be stronger than expected in an age matched population Maberley et al. However, these often were only single observations and certainly could represent the normal prevalence in the population and thus coincidence.

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Notably, they did not find telangiectatic vessels within the macular area. They reported narrowing of the capillary lumen from proliferation of a multilaminated endothelial cell basement membrane, a partial loss of pericytes, accumulation of lipids within the capillary walls and localized areas with disrupted endothelial cells. The neurosensory retina showed intracellular and intercellular edema in the temporal paracentral area with granular material in the extracellular spaces. Some ganglion cells and cells in the inner nuclear layer appeared to be undergoing degeneration.

The outer nuclear layer was less affected and the retinal pigment epithelium appeared normal. They postulated that the angiographic appearance of telangiectasis could be due to rapid diffusion of the dye into the thickened wall of the capillary sites of endothelial cell degeneration, subsequent diffusion within the wall and eventual leakage into the surrounding tissue.

It should be noted that data on the normal appearance of the aged human retinal vasculature on electron microscopy is scarce. Notably, Powner et al. In a separate study, Powner et al. An angiogram 12 years before the patient's death showed alterations characteristic for MacTel type 2. Striking loss of central macular pigment was evident macroscopically see Chapter 6.

Histology revealed abnormally dilated vessels in the deeper plexus of the retinal paracentral vasculature. Immunohistochemistry suggested a marked reduction of basement membrane proteins indicating vascular pathology. Claudin-5, a marker for tight junctions between retinal endothelial cells, showed immunoreactivity in normal as well as in telangiectatic vessels. Due to poor preservation of the photoreceptors in the available sections, no definite conclusions were possible regarding the extent of photoreceptor loss.

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No differences compared with a control eye were observed on the immunohistological staining for macrophages using the Iba1 microglia marker and no obvious abnormalities were found within the retinal pigment epithelium Powner et al. The fellow eye was also studied by electron microscopy Cherepanoff et al. The most significant finding was a subretinal accumulation of degenerate photoreceptor elements within the central retina with only minimal retinal pigment epithelial reaction and a normal appearing Bruch's membrane. There was also a focal loss of the outer limiting membrane and mild irregularity of the inner limiting membrane within the central retina.

Notably, the vascular membrane originated from the retinal vessels and no connection to the underlying choriocapillaris was found. A further histopathological study of presumed parafoveal telangiectasis is mentioned for completeness Eliassi-Rad and Green, The authors described histological findings that appear not to be compatible with the current concept of MacTel type 2.

There was no clear clinical diagnosis of MacTel type 2 made before the patient's death, suggesting a different diagnosis. Several features of MacTel type 2 may be found in other diseases that should be considered when funduscopic assessment allows no clear-cut diagnosis. Findings that may be helpful in distinguishing MacTel type 2 include the temporal predilection of a bilateral disease process not respecting the horizontal raphe, the characteristic inner and outer retinal cavities seen on OCT imaging and the loss of macular pigment visible on fundus AF imaging.

Further clues may be the apparent lack of retinal thickening despite vascular low grade leakage due to underlying retinal atrophy, and more pronounced visual disturbance e. It is less prevalent than MacTel type 2, although this might not be true in all populations Lee et al. Little is known of its pathophysiology and natural history. It may be that the classification into type 1A and 1B represents different stages of the same disease rather than different disease groups Gass and Blodi, ; Watzke et al.

It has been proposed that the disease is a developmental disorder which represents a mild variant of Coats' syndrome and Leber's miliary aneurysms Cahill et al. Disease severity may be associated with age of onset, with earlier disease occurrence having the worse prognosis Cahill et al. No clear association with systemic or other ocular diseases has been identified.

The characteristic funduscopic findings of MacTel Type 1 include visible aneurysmatic dilation of the macular blood vessels, mainly confined to the temporal region, with surrounding cystoid macular edema and yellowish exudates Gass and Blodi, ; Yannuzzi et al. The presence of microaneurysms is an important feature to distinguish MacTel Type 1 against MacTel Type 2, where microaneurysms are not a characteristic phenotypic feature. A serous or exudative detachment of the macula, a cicatricial disciform macular lesion and haemorrhages may develop Yannuzzi et al.

The vascular changes typically involve an irregular or oval zone and are centered temporal to the fovea. The different proportions of peripheral involvement may be due to different definitions of peripheral or extramacular location, the restricted availability of peripheral angiographic images in retrospective case series or different diagnostic criteria in the respective studies. Fluorescein angiography typically reveals vascular aneurysmal widening of the macular vessels in the early phase with diffuse leak and cystoid edema in the late phase Gass and Blodi, ; Yannuzzi et al.

There may be variable capillary occlusion or loss, possibly secondary to longstanding neurosensory edema Gass and Blodi, ; Yannuzzi et al. On indocyanine green angiography, there commonly is staining of the aneurysmal vascular changes in the late angiographic phase, which is usually not observed in MacTel type 2. Optical coherence tomography OCT shows cystoid macular edema with retinal thickening Surguch et al. The characteristic localized loss of macular pigment within the central retina as described for MacTel type 2 is not present in type 1; however, central macular pigment density has been noted to be slightly decreased compared to normal Sawa et al.

Complaints reported by patients with MacTel type 1 include impaired visual acuity and blurred vision, less frequently metamorphopsia or a negative scotoma Abujamra et al. Patients with MacTel type 1 may present with advanced disease since they usually have one unaffected eye. In a recent structure—function correlation, disruption of the inner segment—outer segment border and cystoid retinal thickening was found to be associated with reduced retinal function Takayama et al.

Patients with type 1B disease usually only report mild metamorphopsia while visual acuity may be preserved. Focal laser photocoagulation direct coagulation of aneurysms has been reported to decrease vascular exudation and may improve visual acuity in some patients Chopdar, ; Gass, ; Gass and Blodi, ; Gass and Oyakawa, ; Lowe et al. The success of treatment may depend upon the extent of pre-existing neurosensory damage due to longstanding edema or lipid exudates extending into the foveola. Repeated treatment may be necessary. Single reports showed that intravitreal administration of the steroid triamcinolone may result in a decrease of the macular edema associated with MacTel type 1 Charbel Issa et al.

Intravitreal injections of the VEGF-inhibitor bevacizumab have also been tried, but these resulted in reduction of retinal edema and an increase in visual acuity in only few eyes Gamulescu et al. The vascular alterations, which likely are structural in nature, did not disappear completely with either intravitreal steroids or VEGF-inhibitors, the effect in most cases being only temporary with recurrence of macular edema after cessation of therapy.

Information from controlled prospective trials to address systematically the natural history and potential long-term treatment effects in this rare condition is lacking. Rebound phenomena following therapy were described after different treatment approaches and changes of the activity of the disease, including spontaneous stabilization and even resolution of the macular edema without treatment have been reported Gass and Blodi, ; Gass and Oyakawa, Therefore, intervention should be recommended thoughtfully and weighed against potential risks and side effects.

If central vision is in danger due to threatened extension of lipid exudates into the foveola, intervention should seriously be considered. Telangiectatic vascular alterations within the macular area may be observed in diabetic retinopathy, radiation retinopathy, branch retinal vein occlusion or secondary to inflammatory ocular disease.

A thorough medical history is essential. Except in small branch retinal vein occlusions, these diseases usually reveal more wide-spread and additional fundus changes, including alterations such as haemorrhages and nerve fiber layer infarcts. Exudative cystoid macular edema commonly accompanies retinal vascular disease.

Branch retinal vein occlusions usually respect the horizontal raphe and occur distal to an arteriolar-venular crossing. Little is known about rare types of idiopathic macular telangiectasia as proposed in Gass and Blodi's type 3, which are associated with capillary occlusion and systemic diseases Gass and Blodi, Rare syndromic occurrence of macular telangiectasia may also include patients with dyskeratosis congenita Yannuzzi, or facioscapulohumeral muscular dystrophy Fitzsimons et al.

Hyporeflective cavities of the neurosensory retina observed with OCT imaging similar to those in MacTel type 2 have been reported in patients with a variety of inherited retinal dystrophies Barthelmes et al. Also, the area affected in MacTel type 2 is similar to that involved in various inherited dystrophies that present with e. However, no similar vascular changes have been shown in the few available angiographic reports of these conditions Gualino et al.

Notably, funduscopy in such patients may reveal crystalline deposits as in MacTel type 2 Drenser et al. In age-related macular degeneration, drusen are usually present early in the disease course. Late disease stages are characterized by the either geographic atrophy or neovascular membranes originating from the choroidal vasculature in contrast to the primarily retinal origin of neovascular complexes in MacTel type 2.

Further macular alterations that may be considered in the differential diagnosis of selected cases are Irvine-Gass syndrome in pseudophakic patients, solar retinopathy which may present with a yellowish foveal lesion on funduscopy and atrophic changes within the foveal photoreceptor layer on OCT imaging, other diseases with crystalline retinal deposits Drenser et al.

Various approaches have been investigated to treat MacTel type 2 Table 4. Most available reports are single cases or retrospective small case series, with no data available from larger controlled prospective trials. Overview of reported treatment approaches for non-proliferative and neovascular MacTel type 2. The slow progression of functional defects in MacTel type 2 Fig. Outcome parameters different from visual acuity assessment, such as microperimetry or enlargement of areas of photoreceptor loss on OCT appear more suitable for monitoring treatment effects in MacTel type 2 see Chapters 8 and 9.

Only few publications with small patient numbers have reported such parameters. Moreover, short term effects such as improvement in visual acuity after intravitreal application of bevacizumab see below may be due to the temporary decrease of neurosensory edema without affecting the natural history of the disease course, i. Therefore, due to insufficient information, general recommendations concerning the treatment of MacTel type 2 cannot currently be made.

Autofluorescence of Basal Laminar Drusen

Since the potential gain of function after any treatment might be limited by pre-existing neurosensory atrophy, initial thorough phenotypic and functional characterization is most important. The timing of intervention may be crucial since any treatment might be ineffective once neurosensory atrophy or fibrosis have occurred. This chapter is divided into treatment approaches for nonproliferative and proliferative phases. A separate paragraph in Chapter 5 summarizes reports of treating macular holes in eyes with MacTel type 2. Despite individual observations of improvement after focal argon laser photocoagulation for MacTel type 2 Chopdar, ; Hutton et al.

Park and co-workers retrospectively analyzed the long-term outcome median follow up time: Compared with untreated eyes, previous laser photocoagulation was associated with distortion of retinal vessels, more fibrovascular tissue, retinal pigment epithelial clumping, new draining venules and retinal hemorrhages. Argon laser photocoagulation for MacTel type 2 may be complicated by subretinal hemorrhage Friedman et al.

Therefore, because no proven benefit has been shown and because there may be an increased risk for developing neovascular complexes, laser photocoagulation is not recommended for the treatment of non-proliferative MacTel type 2. Photodynamic therapy was used in two eyes of two patients with non-proliferative MacTel type 2 De Lahitte et al.

OCULAR EXAMINATION

In neither patient did the authors observe significant changes in visual acuity, fluorescein angiographic leakage or OCT findings. Intravitreal injection of triamcinolone IVT has been reported to reduce late phase hyperfluorescence in fluorescein angiography with Martinez, or without Alldredge and Garretson, ; Cakir et al. Smithen and Spaide did not find an effect on either fluorescein angiography or visual acuity Smithen and Spaide, There appeared to be a reduction in retinal thickness after IVT followed by a waning of the effect after nine months in one report Cakir et al.

In the largest study reported to date, the change in visual acuity of 19 eyes 14 patients which received one or two IVT injections was analyzed retrospectively Wu et al. After a mean follow-up of IVT had a beneficial anatomical and functional effect in a MacTel type 2 patient presenting with bilateral foveal detachment Maguluri et al.

Posterior juxtascleral administration of anecortave acetate, an angiostatic synthetic cortisol derivative supposedly without corticosteroid bioactivity, was reported to stabilize visual acuity over 24 months in two non-proliferative eyes. However, no data were provided with regard to the natural history in the fellow eye for comparison, the angiographic effects, or alterations on OCT-imaging Eandi et al. Short term observation after inhibition of VEGF using intravitreal bevacizumab, resulted in a marked decrease of parafoveolar leakage, normalization of macular capillaries and decrease in retinal thickness.

Visual acuity was reported to improve in few patients Charbel Issa et al. Other studies have not found similar effects, possibly because treated eyes had more advanced disease Charbel Issa et al. As a result of the chronic nature of the disease, the effect of the anti-VEGF-treatment tended to wear off after two to four months Charbel Issa et al.

Further studies with longer follow up identified a beneficial effect of intravitreally applied bevacizumab in patients who were treated on a pro re nata PRN regimen over a mean follow up time of 18 Charbel Issa et al. Conclusions from those studied are limited due to the small patient cohorts and the retrospective study design. At the end of those studies, there was no effect on visual acuity.

While the overall light sensitivity within the area of vascular leakage might increase slightly Toy et al. It was concluded that monthly ranibizumab is not recommended for patients with MacTel type 2. The foveal anatomy regained its normal configuration with improved visual acuity in several retrospectively analyzed cases.

This observation needs further investigation in larger prospectively designed trials. Various treatments have been used for subretinal neovascularisation, which is a major cause of severe vision loss in a minority of patients with MacTel type 2 Engelbrecht et al. Park and co-workers found little change in the size of the fibrovascular tissue over time and a final visual acuity similar for eyes with and without fibrovascular tissue.

This group consequently questioned the usefulness of treatment in those eyes Park et al. Therefore, interventions might be most beneficial in early and active proliferative disease stages before the development of fibrotic membranes. Visual improvement, stabilization and deterioration have all been reported after argon laser photocoagulation. The resulting scotoma and the potential to trigger further growth of neovascular membranes would not favor this treatment approach, even if the membranes were extrafoveal. Photodynamic therapy PDT was first reported in a patient with recent decrease in visual acuity due to subretinal neovascularisation.

Visual acuity improved 2 lines after two treatments and remained stable for seven months Potter et al. Interestingly, leakage from the neovascular membrane ceased after treatment while parafoveal leakage typical for MacTel type 2 continued. They noted a significant and rapid improvement in visual acuity following each treatment but also a rapid reperfusion of the neovascular membrane following PDT-induced closure.

The group speculated that the first may be attributable to a relatively healthy pigment epithelium compared to other diseases in which PDT is used, such as age-related macular degeneration. The latter finding was explained by the high-flow anastomoses described in MacTel type 2. The largest series studying PDT for neovascular MacTel type 2, a retrospective analysis, described seven eyes of six patients Potter et al. An average of 2. More than 2 lines decrease or increase in visual acuity was observed in one eye each while the other 5 eyes remained stable.

Hussain and co-workers treated six eyes of three patients three times at shorter interval 2 months than usual. All eyes in this series had stable visual acuity after a median follow up time of 10 months range 6—21 months. The researchers noted associated retinal pigment epithelium collateral damage in all six eyes of their study. There is the theoretical concern with PDT for MacTel type 2 that the photosensitizing drug may leak out of the retinal vessels in the macula and cause harm when it is activated Hussain et al.

However, others did not observe any side effects Potter et al. Few cases of MacTel type 2 treated with PDT combined with an intravitreal injection of either triamcinolone Smithen and Spaide, or ranibizumab Rishi et al. As an additional finding, they reported a complete absence of telangiectasia after treatment. However, intravitreal injection of triamcinolone alone in the fellow nonproliferative eye revealed no marked functional or angiographic effect.

Combined PDT and intravitreal ranibizumab injection was reported in two case reports. Only one PDT treatment with either one Rishi et al. T ranspupillary thermotherapy TTT was used in an interventional case series by Shukla et al. After a mean follow up of 8. The median visual acuity remained stable compared with baseline. Posterior juxtascleral administration of anecortave acetate 15 mg, 6-month retreatment interval in five eyes of four patients was reported to result in stabilization or improvement of lesion size, resolution of leakage, and stabilization of vision Eandi et al.

One eye with a very short history of visual deterioration showed the best result with an increase of 3 lines in visual acuity within a follow up period of 12 months. Three other eyes showed an increase of two and one line or a decrease in one line within a follow up period of 24 months. Visual acuity did not change in one eye that was last said to be stable 9 months after the first treatment.

Intravitreal application of VEGF-inhibitors has become the first line treatment for neovascular membranes due to age-related macular degeneration AMD. Jorge and co-workers were the first to show a positive effect of bevacizumab in a patient with a juxtafoveolar neovascular membrane Jorge et al. Mandal presented a case series of six eyes of six patients treated with intravitreally injected bevacizumab Mandal et al. After a mean period of 4.

One eye without functional improvement exhibited retinal pigment hyperplasia involving the center of the fovea. A decrease in retinal thickness and leakage was demonstrated by OCT imaging and fluorescein angiography, the latter also showing diminuation of leakage from telangiectatic vessels. Another retrospective case series 9 eyes by Roller et al.

A mean of 1. Most other smaller case reports have demonstrated similar outcomes of intravitreally applied bevacizumab on the activity of neovascular membranes in MacTel type 2. Effects of intravitreal bevacizumab therapy in neovascular MacTel type 2. A Findings at baseline visit: Foveal hemorrhage in funduscopy left, cf. In microperimetry, there is a large absolute scotoma which encompasses the foveal center. Four months after one single treatment with intravitreal bevacizumab B , the hemorrhage had been resorbed and leakage was reduced. Surgical removal of subfoveal vascular membranes in MacTel type 2 could not be performed without also removing pieces of neurosensory retina due to adherence of the membranes to the retinal vasculature Berger et al.

Since the functional outcome was unfavorable, it may be concluded that subretinal surgery with current techniques is not efficacious for proliferative MacTel type 2. Since the landmark study by Gass and Blodi in , little knowledge has been added on the phenotypic and functional changes of MacTel type 2 until recently. In the last several years, however, a large number of previously unknown findings have been identified by applying advanced imaging and functional testing.

Thorough and valid evaluation of disease progression will be necessary not only to assess treatment effects in future therapeutic trials, but also to assess the natural history and eventually generate a more refined disease staging. Analysis of longitudinal data using new tools for disease phenotyping will help to identify outcome measures for interventional clinical trials as well as to stratify patients regarding their risk for disease progression. Longitudinal data will also reveal if patients can be stratified according to different disease characteristics into subgroups of fast or slow progressors, possibly according to different genetic backgrounds or environmental factors.

There may also be variation in the individual pathophysiological response to the disease. For instance, the chronic low grade leakage due to an impaired blood-retinal barrier might trigger anti-retinal-antibodies in a subset of patients which might subsequently develop a faster or different disease progression.

The most widely accepted clinical endpoint in ophthalmology, visual acuity, appears not to be a sensitive marker for progression of MacTel type 2. Central retinal function, including distance visual acuity, may remain relatively intact over substantial periods of time even though other visual functions, such as reading ability and the size of paracentral scotomata, deteriorate Fig.

However, the high variability of psychophysical testing results in difficult verification of functional deterioration in a slowly progressing disease such as MacTel type 2. Objective surrogate markers, e. Since not all structural changes over time are functionally meaningful, such surrogate markers would need to be validated in independent studies against true clinical endpoints.

A recent interventional study illustrates how relying on certain imaging modalities could be misleading in MacTel type 2: VEGF-inhibition over one year resulted in regression of the vascular alterations on fluorescein angiography and visual acuity, after a transient increase, was stable compared with baseline after one-year see Chapter However, microperimetry rather showed a decrease in paracentral retinal sensitivity and point-to-point structure—function correlation revealed that functionally relevant alterations within the photoreceptor layer visible on spectral domain OCT progressed in treated eyes Charbel Issa et al.

Therefore, despite the apparently positive effect on fluorescein angiography and visual acuity testing, this therapy was not recommended. Notably, the atrophic changes in the photoreceptor layer as the structural correlate of the retinal sensitivity loss were already visible on spectral domain OCT before their functional relevance could be detected by microperimetry Charbel Issa et al. The reduced macular pigment density within the central retina is one of the most striking features of MacTel type 2.

The lack of its function as a blue light filter could result in increased light damage of macular photoreceptors. In MacTel type 2, a primary loss of macular pigment due to defective trafficking or storage e. It remains to be determined if macular pigment is simply reduced centrally or if there is additional displacement of macular pigment towards the periphery.

The authors found values comparable to normal controls, suggesting that lutein and zeaxanthin are actually not lost from the posterior fundus, but rather displaced laterally to a certain extent. Longitudinal data studying the evolution and progression of macular pigment loss in MacTel type 2 patients are so far lacking. Since MacTel type 2 shares structural features with retinal dystrophies, assessment of macular pigment density and distribution in patients with other macular dystrophies may help to further understand this finding.

Loss of macular pigment may be considered a secondary phenomenon if it occurs uniformly in unrelated diseases.

The known deficiency of fatty aldehyde dehydrogenase in patients with this disease may suggest possible pathogenetic pathways involved in the lack of macular pigment. Moreover, similar deposits and OCT-changes have been reported for patients with Tamoxifen retinopathy, for which no data on macular pigment distribution have yet been published.

Tamoxifen was suggested to inhibit glutamate uptake into retinal pigment epithelial cells. Increased concentrations of glutamate in the extracellular retinal space might lead to excitatory toxicity with subsequent cell death. Experimental data are available for Canthaxanthin retinopathy which also shows similar crystalline deposits, although in a slightly different distribution. In the monkey retina, the amount of the carotenoid canthaxanthin and its metabolites in retinal tissue correlated with the amount of ophthalmoscopically visible crystalline deposits, strongly suggesting that these crystals indeed are due to a high load of this carotenoid Goralczyk et al.

A histopathological investigation of a human eye with canthaxanthin retinopathy also suggested that carotenoids are involved in the pathogenesis of the crystalline deposits Daicker et al. It appears more likely that structural alterations lead to a localized loss of macular pigment, which then — hypothetically — may be converted into its crystalline form. Further research into the pathophysiology of MacTel type 2 is likely to benefit research on the so far incompletely understood mechanisms of macular pigment accumulation in the central retina.

Vice versa , a better knowledge of the physiological mechanisms and anatomical structures involved in accumulation, trafficking and storage of lutein and zeaxanthin in the central retina may shed light on the pathophysiology of MacTel type 2. Immunohistochemical studies showed specific labeling for both binding proteins of rod and cone inner segments, especially in the mitochondria-rich ellipsoid region. Since OCT studies in patients with MacTel type 2 suggested this retinal layer to be affected early in the disease course see Chapter 6. Additional strong labeling with anti-GSTP1 was found in the outer plexiform layer Henle's fiber layer.

Recently, polymorphisms in the GSTP1 gene were looked at in MacTel type 2 patients but no obvious association was found Parmalee et al. Questions to be answered with regard to the characteristic distribution of macular pigment in patients with MacTel type 2 will include: Does the expression of lutein and zeaxanthin-binding proteins in photoreceptors point to a primary photoreceptor disease? What is the anatomic or physiological correlate that defines the characteristic area of macular pigment loss? Hyporeflective atrophic cavities of the neurosensory retina have been reported in patients with inherited retinal dystrophies Barthelmes et al.

With regard to the inner hyporeflective cavities, there may be a loss of retinal structural integrity possibly similar to X-linked retinoschisis. In the absence of a bullous central retinal schisis, OCT findings in X-linked retinoschisis may actually resemble those in MacTel type 2 Gerth et al. The atrophy of the outer neurosensory retina which is primarily supplied by the choroid, the localized loss of macular pigment which has not been reported to occur in other retinal vascular disease, and the larger size of areas of macular pigment loss compared with angiographically visible vascular alterations all do not support a primarily vascular disease process.

The eponymous and characteristic ectatic parafoveolar capillaries may represent a secondary phenomenon, e. This could lead to the development of ectatic and sprouting capillaries along a concentration gradient towards the outer retina. A medical history that may lead to similar vascular alterations e. Accordingly, some studies identified diabetes mellitus, a pathologically decreased glucose tolerance as well as a history of radiation exposure to be associated with MacTel type 2 Chew et al.

It may be speculated that similar neurosensory atrophic alterations may occur with varying vascular alterations depending on additional factors that modify the susceptibility to develop the vascular phenotype. For instance, it was suggested that the presence of more numerous arterio-venous crossings temporal to the fovea compared with nasally might give rise to chronic low grade congestion or venous stasis of the temporal paramacular capillaries Gass and Oyakawa, However, a similar vascular pattern was identified in 43 of 54 randomly selected control eyes. This could cause structural abnormalities with subsequent decompensation of these vessels in adult life.

The reason for the temporal predilection may not necessarily be found in the retinal vasculature. If the vascular alterations are a secondary feature in the pathophysiology of the disease, any proposed mechanism would have to explain why a primarily atrophic disease process would be restricted to or most pronounced within this area. Notably, the retinal area involved in MacTel type 2 is similar to the localization of changes in other macular dystrophies without vascular pathology Kurz-Levin et al.

The underlying cause for the affection of this particular area as well as the temporal predilection is, however, still unknown. They are intimately connected with cone photoreceptors through microvilli extending from the outer limiting membrane. They express GLAST, the predominant transporter within the retina for the removal of the excitotoxic neurotransmitter glutamate. Results from a clinico-pathological analysis of a pair of eyes obtained post mortem from a confirmed case of MacTel type 2 Powner et al.

Macular pigment is located in Henle's layer Snodderly et al. The retina in this model showed a rapid photoreceptor apoptosis, vascular telangiectasia, a blooderetinal barrier and breakdown later also deep retinal neovascularization Shen et al. The procedure resulted in structural damage and compromised retinal function. Other animal models with similar retinal alterations may add to the understanding of the pathogenesis of MacTel type 2. Transgenic mouse models with over-expression of VEGF in photoreceptor cells share overexpression of VEGF as well as neurosensory alterations similar to the findings in patients Lai et al.

A mouse with a defect in the gene for very low density lipoprotein receptor also develops some features similar to MacTel type 2 Dorrell et al. Deep retinal neovascularisation arising from the retinal vasculature is prominent in this model. Photoreceptor cell death associated with the neovascularisation was inhibited by both antioxidants and cell-based delivery of neurotrophic factors Dorrell et al.

Since loss of photoreceptors appears to be the main cause for the loss of vision in MacTel type 2, treatment to prevent progression of the condition may be aimed at preventing photoreceptor loss. It has been shown to protect the photoreceptors from degeneration in a variety of animal models of retinitis pigmentosa, such as rd mice Cayouette and Gravel, ; LaVail et al. There is already evidence that CNTF might be beneficial in human retinal degenerative disease as shown recently in a phase Ib trial in retinitis pigmentosa Sieving et al.

1. Introduction

Macular telangiectasia MacTel type 2 is a neurodegenerative disease affecting the central retina. There has been remarkable progress in characterizing the disease and revealing its pathophysiology. General progress in phenotyping and therapy for retinal disease has helped tremendously to study MacTel type 2.

Examples are imaging studies using high-resolution OCT and confocal laser scanning ophthalmoscopy, fundus-controlled perimetry, and intravitreal pharmacotherapy. So far, no therapy has been shown to be efficacious to modify the slow photoreceptor loss characteristic for the disease. While efficacy of anti-VEGF therapy has not been shown in the non-proliferative disease, there may be a benefit for patients with neovascular disease manifestation. MacTel type 2 shows some unique features such as a central reduction of macular pigment and hyporeflective cavities at the level of the inner and outer retina as observed with high-resolution OCT imaging.

Such characteristic features provide further clues for the development of future therapy. Since the condition appears to be primarily neurodegenerative in nature, therapeutic interventions with compounds that have neuroprotective properties appear promising. An interventional clinical trial in Mactel type 2, making use of neuroprotection is currently underway. Frieda Derdeyn Bambas Professor of Ophthalmology.

Gass' Atlas of Macular Diseases: 2-Volume Set - Expert Consult: Online and Print by Anita Agarwal

None of the authors has a conflict of interest. Supplementary data Supplementary material associated with this article can be found, in the online version, at http: National Center for Biotechnology Information , U. Prog Retin Eye Res. Author manuscript; available in PMC May 1. Note the extensive areas of early hyperfluorescence producing a 'stars-in-the-sky' appearance. Age related macular degeneration, adult vitelliform foveomacular dystrophy, basal laminar drusen, Best vitelliform dystrophy, pattern dystrophy, familial drusen, fundus albipunctatus.

The patient had no family history of macular degeneration. Because there was no evidence of active choroidal neovascularization on fluorescein angiogram, we elected to monitor his condition. He was seen two months later for follow up with no interval change in his vision or in the quantity of subretinal fluid. In the event of an increase in subretinal fluid or presence of choroidal neovascularization, anti-vascular endothelial growth factor injections will be initiated.

Basal laminar drusen cuticular drusen is a rare condition first described by Donald Gass in Histopathologically they are a focus of thickened RPE basement membrane 3 , with elevation between the RPE-basal laminar band. Later in life drusen may become more numerous and at times form a cluster of 15 to These basal laminar drusen may predispose patients to the development of loss of central vision from a vitelliform exudative macular detachment. Most patients to date have no family members with signs of disease.

OCT findings disclosed three types of drusen configurations: Type 1 with a very shallow elevation of the RPE-basal laminar band, Type 2 pattern with a triangular elevation, and Type 3 with a broad mound-shaped elevation of the RPE-basal laminar band. It is important to distinguish basal laminar drusen from age related macular degeneration as the treatment approaches and prognoses differ. The prognosis for retaining useful central vision is better than in age-related macular degeneration.

In some instances the fluid may resolve spontaneously with restoration of good vision. In others, however, poor vision may develop from geographic atrophy, choroidal neovascularization, or serous hemorrhagic disciform detachment. Treatment is not necessary unless the visual decline is significant, or if there is evidence of choroidal neovascularization. To see what your friends thought of this book, please sign up.

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