Introduction

Neovascular glaucoma (NVG) is a secondary glaucoma characterized by the formation of new blood vessels (rubeosis iridis) on the iris and the proliferation of fibrovascular tissue in the anterior chamber angle, resulting in increased intraocular pressure (IOP), optic nerve damage, and visual loss. This disease is refractory to treatment and has a poor prognosis. It is commonly associated with retinal and anterior segment ischemia, such as proliferative diabetic retinopathy (PDR), central retinal vein occlusion (CRVO), and carotid occlusive disease (COD).¹

Coats was the first to describe histopathological evidence of new blood vessel formation in the iris of a patient with central retinal vein occlusion.² Salus reported similar findings of new blood vessel formation in the eyes of patients with diabetes.³ In one study, 36% of all cases of NVG arose from CRVO, 32% from PDR, and 13% from carotid artery occlusive disease.⁴

Early recognition of NVG secondary to carotid artery stenosis can be life-saving; however, its rarity makes diagnosis challenging. With only a few cases reported in the literature, the condition often remains underrecognized. COD can exacerbate retinal and anterior segment ischemia, leading to further complications. This case illustrates the intricate relationship between these conditions and underscores the importance of a multidisciplinary approach to management.

Case Presentation

We report the case of a 60-year-old woman diagnosed with NVG secondary to proliferative diabetic retinopathy. During her hospital stay, the ophthalmology and vascular surgery teams at the Bahrain Defence Force Royal Medical Services, Military Hospital Bahrain, successfully managed her concomitant carotid occlusive disease with intravitreal anti-VEGF injections, pan-retinal photocoagulation (PRP), implantation of an Ahmed glaucoma valve, and thromboendarterectomy.

The patient had a history of type 2 diabetes mellitus, hypertension, and dyslipidemia. She was on regular follow-up at the eye clinic for bilateral NVG secondary to advanced diabetic eye disease. During this period, her condition remained stable, with well-controlled IOP and diabetic retinopathy.

In August 2024, during a scheduled follow-up, the patient presented with a two-day history of right eye pain. The pain had a sudden onset, was localized, sharp, and not associated with vision changes or halos. No history of ocular trauma or contact lens use was reported. Examination revealed best-corrected visual acuity of 6/6 in the right eye and 6/12 +2 in the left eye, with IOPs of 32 mmHg and 22 mmHg, respectively. Slit lamp examination showed aggressive iris neovascularization in the right eye. Gonioscopy revealed new vessels at the anterior chamber angle.

The patient was treated with medications, intravitreal anti-VEGF, and PRP. Despite regression of rubeosis, IOP remained poorly controlled, and an Ahmed glaucoma valve was implanted in the right eye. Four months later, the patient presented with recurrent NVG (IOP 45 mmHg, conjunctival congestion, corneal edema, and rubeosis iridis). Maximal medical therapy and anti-VEGF/PRP were applied, but IOP remained uncontrolled. A carotid Doppler ultrasound revealed 80% occlusion of the right internal carotid artery.

CTA confirmed significant stenosis (≥70%) of the proximal right internal carotid artery. The patient underwent thromboendarterectomy, after which regression of neovascularization and IOP control were achieved.

Discussion

NVG is caused primarily by PDR, CRVO, and less commonly ocular ischemic syndrome (OIS).⁵ OIS is associated with carotid artery stenosis or occlusion, resulting in decreased blood supply to the eye and orbit.⁶ Atherosclerosis plays a key role by limiting retinal blood supply.⁷ Risk factors for OIS include hypertension (73%), diabetes mellitus (56%), and myocardial infarction (4%).⁸ The estimated 5-year mortality rate is ~40%.⁸

The simultaneous occurrence of NVG, PDR, and COD presents a unique challenge. Retinal ischemia stimulates VEGF production, leading to neovascularization. Carotid occlusive disease further compromises retinal perfusion. Anti-VEGF therapy reduces iris neovascularization, while PRP addresses retinal ischemia. In this patient, standard treatments showed limited response due to underlying carotid stenosis, which was confirmed and corrected surgically.

Outcomes and Follow-Up

At nine months follow-up, ocular pain significantly improved, and right eye IOP reduced to 16 mmHg. Visual acuity in the left eye remained stable. The patient was advised to maintain strict glycemic control and follow-up with a vascular specialist.

Conclusion

This case highlights the importance of recognizing the interplay between NVG, PDR, and carotid occlusive disease. Multidisciplinary management involving ophthalmology and vascular teams is crucial. Early intervention and comprehensive strategies can preserve vision and improve overall patient outcomes. Regular follow-up is essential to prevent recurrence and manage complications.