Retinal Arterial Macroaneurysm: Report of 3 Cases

Introduction

Retinal Macroaneurysm have been observed since 1808, In 1973 Robertson first described RAM with its characteristic features [1, 2, 3, 4]. RAMs are acquired disease [3].

Retinal arterial macroaneurysms (RAM) may be defined as fusiform (cuffed’) or saccular (‘blow-out’) dilatations of the retinal arteries, usually arising within the first three orders of retinal artery bifurcation [1, 2, 3, 4, 5]. The supratemporal artery is most commonly affected because patients with such involvement are more likely to have visual impairment [2]. In most reported cases RAM are unilateral and single, while 10% may be bilateral2 as well as some report noted multiple macroaneurysms [2]. Majority of reported cases showed female predominance [2, 5]. Commonly RAM occur at sixth and seventh decades of life [2, 5]. RAMs are strongly associated with systemic hypertension and atherosclerosis in approximately 75% of patients [1, 2, 3, 4, 5].Retinal arteriolar RAMs may be asymptomatic, if the macula is not involved. Deterioration of central vision occur as a result of macular edema, exudation or haemorrhage [2, 3, 4, 5, 6].

Natural history may lead to a spontaneous resolution of the lesion, but also have a number of vision- threatening complications, including subretinal, preretinal or vitreous haemorrhages, macular oedema, serous macular detachment, macular deposition of hard exudates, macular hole and branch retinal vein occlusion [3, 4, 5, 6].

Treatment is indicated when RAMs causing exudative manifestations or haemorrhage involving the fovea. Treatment of RAMs is still controversial [4, 5, 6]. Mostly threshold laser photocoagulation is carried out in an attempt to achieve the obliteration of the vascular lesion. Several studies evaluated laser treatment for exudative RAMs with 4 months of follow-up and showed that it improved visual acuity and central foveal thickness [3, 4].

Nevertheless, several complications have been related to direct threshold laser treatment (TLT) [3, 4, 5, 6]. So subthreshold laser treatment (STLT) has been proposed in an attempt to minimise the adverse aspects of conventional laser photocoagulation [4, 5, 6].

Recently, intravitreal injections of anti–vascular endo- thelial growth factor (VEGF) drugs have been considered as a treatment option for RAMs [6]. In this report we analyse three patients with RAMs who were followed up for period ranging from four months to four years. All three patients presented with dimness of vision due to chronic decompensation due to an exudative response.

Discussion

Retinal arterial macroaneurysms (RAM) may be defined as fusiform or saccular dilatations of the retinal arteries, usually arising within the first three orders of bifurcation and at AV crossings [1, 2, 3, 4, 5]. The most common involvement is along the superotemporal or inferotemporal arcades, with the nasal vessels more rarely involved. Macroaneurysm have also been reported in cilioretinal arteries and on the optic nerve head1. The diameter of macroaneurysm is 100 to 250 micron3. Our first and second case had RAM along the superotemporal arcade and third case showed RAM along inferotemporal arcades (Table 1).

Table1: Demographic and clinical profile of three patients. HTN-Hypertension DM- Diabetes Malitus, ST- Superior Temporal IT- Inferior Temporal. BCVA- Best corrected visual acuity.

RAMs are associated with exudation and hemorrhage, which may result in decreased visual acuity if it involves the central macula. In all three of our cases, RAM predominantly associated with exudation not haemorrhage involves the central macula.All of them came with huge deterioration of vision (Table-1).

Several series have reported on the natural history and treatment response of macroaneurysms [1, 2, 3] Approximately 10 % of macroaneurysms are pulsatile on initial presentation. (can be a sign of impending rupture). Formation of retinal macroaneurysms is associated with systemic hypertension and atherosclerotic disease, serum lipid abnormalities. Some author postulate that person have focal arterial wall atheroma occurring at defects in the wall, which may be at risk sites of aneurysm formation. After acute hemorrhage, there may be spontaneous thrombosis and closure of the aneurysm lead to resolution of the condition; in some cases, the artery may return to normal [2]. Older woman (Female : male-3:1), usually greater than 60 yrs of age with established history of systemic hypertension are mostly affected [1, 2, 3, 4] Our all three cases were female. Two of the cases were 60 years old and third one was 65 years old. All of them had history of hypertension and second one had diabetes also (Table-1).

The vision threating complications are cystoid macular edema, diffuse /focal macular edema, hemorrhage at different layers like sub retinal pigment epithelial (RPE) hemorrhage sub internal limiting membrane (ilm) and vitreous hemorrhage,secondary epiretinal membrane, serous retinal detachment,macular lipid exudation, branch retinal vein occlusion [3, 4]. The visual prognosis is good in cases presenting with bleeding, poor in those presenting with macular edema, exudation or hemorrhage leading to damage of photoreceptor and scarring [1, 2]. All three cases of this report presented with reduced vision and RAMs with macular oedema and exudate.

The Differential Diagnosis are - Exudative age- related macularm, degeneration(AMD), Branch retinal vein occlusion, Diabetic macular edema, Choroidal melanoma, Diabetic retinopathy, Retinal telangiectasis, Leber’s miliary aneurysms, Von Hippel’s angiomatosis, Capillary hemangioma, Cavernous hemangioma, Radiation retinopathy.

Fluorescein angiography is particularly important in making the diagnosis when there is hemorrhage (which obscures the vasculature). Late fluorescein leakage from within the areas of hemorrhage is characteristic of the aneurysms and may assist in the diagnosis when the vasculature is not visible on direct exam.

A quiet macroaneurysm that is asymptomatic without visible leakage should not be treated, monitored until spontaneous fibrosis occurs. Aneurysms that leak fluid or exudate, or both, and threaten to involve or already involve the central macula may be considered for therapy [4, 5]. Because, the long-term persistence of exudative manifestations or hemorrhages leads to a progressive photoreceptor damage with functional impairment [3, 5]. So in case of indication, early treatment may be desirable in attempting to avoid irreversible structural and functional damage [2, 3, 4, 5].

But there is no clear indication for treatment with laser photocoagulation has been established, and the beneficial effects of such treatments have not been proven [2].

The best approach to treat RAMs is still a matter of controversy and at present there is no general consensus about the optimum approach [1, 2, 3, 4]. The most commonly employed approach is conventional threshold laser treatment (TLT) [1, 2, 3, 5]. In TLT there is direct treatment of the aneurysm with moderately heavy argon green or yellow dye laser with large spot size (500 m) and long duration (0.5 s). But this technique has many complications, like enlargement of the laser scar, and scarring with possible retinal traction, choroidal neovascularization, and subretinal fibrosis, branch retinal artery occlusion, increased retinal exudation have been reported [3, 4, 5].

So recently some author employed indirect laser photocoagulation with Subthreshold Laser Treatment (STLT) to surrounding retina around RAM [3, 4, 5]. STLT may lead to an improved balance in cytokines release,perhaps including an up regulation of basic fibroblast growth factor, thus, STLT may act on the complex interaction among the different molecules implicated in the vascular permeability,promoting a vascular repair together with an improved fluid reabsorption.4 Subthreshold laser treatment (STLT) was reported to be effective in achieving the cessation of leakage, Associated with functional improvement [3]. In M N Abdel-Khalek et al. 1 series of 10 treated eyes two showed improvement in visual acuity. Seven eyes showed no alteration in vision.They1 treated RAM directly either with xenon arc or laser and did not observed any untoward sequelae. Direct treatment speeds the rate of absorption of perianeurysmal exudates and seals the RAMs itself1. The question of direct or indirect treatment of RAMs, however, remains controversial [1, 3, 4]. Recently, several case reports have shown encouraging results of intravitreal anti-VEGF agents for retinal arterial macroaneurysms [5, 6]. It reduces the vascular permiability and act on coagulation cascade ,thus it promote obliteration of RAM and absotption of fluid and exudates.

In our cases we used both TLT and SLT. In 2nd case we also gave additional anti VEGF injection (Bivacijumab). Our 1st and 3rd case showed visual improvement and 2nd case showed visual deterioration.1st case visual improvement from counting finger to 6/12 snellen chart (Table 1). 3rd case showed improvement from 6/60 to 6/9 Snellen chart. 3rd case could not regain vision may be due to late presentation and RAM located near to fovea.

Conclusion

RAMs are probably commoner than is realised. They may confront the ophthalmologist in one of two ways: (1) sudden loss of vision due to rupture of RAMs causing haemorrhage that obstract the vision: (2) grdual loss of vision due to macular oedema and hard exudate.

Acknowledgement

We acknowledge with thanks the expert and industrious help of Mr Michael Strachan, medical photographer, Mohammad Shamsal Islam, Research officer, (Dr. Ahmadur Rahman Research Centre, ICO, CU) and the following consultants who were kind enough to refer cases:.