ABSTRACT

A 31-year-old woman with inverse retinitis pigmentosa presented with severe ocular pain and ingrained visual loss. Biomicroscopy revealed a large scleromalacia area above the superior limbus, minimal Descemet’s membrane folds, aqueous flare, rubeosis iridis, and mature cataract. Intraocular pressure was 39 mmHg, and the clinical picture was consistent with neovascular glaucoma. After immediate medication to reduce ocular discomfort, an anterior chamber bevacizumab injection was performed. At 1 week post-injection, the rubeosis iridis had largely regressed and intraocular pressure was 21 mmHg. At post-injection 1 month, antiglaucomatous medication was discontinued because intraocular pressure was stable. Clear cornea, normal anterior chamber depth, and mature cataract were seen via biomicroscopy, and increased axial length with no significant change in posterior segment echogenicity were observed on ultrasonography. Three years after the single dose of bevacizumab, neovascularization was not seen in either the anterior chamber angle or on the iris surface, and intraocular pressure remained within normal range. The most important aspect of this case report is that it is the first to show an unusual association between neovascular glaucoma, scleromalacia, and inverse retinitis pigmentosa.

Introduction

Retinitis pigmentosa (RP) is a heterogeneous group of inherited disorders characterized by photoreceptor and retinal pigment epithelium (RPE) abnormalities. It can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner, and over 40 genes are associated with this group of retinal dystrophies.¹ Typical clinical symptoms are night blindness, reduced central vision, and visual field constriction. Mid-peripheral pigment migration, vascular attenuation, and disc pallor are the classical triad of retinal findings of RP.² Primary open-angle glaucoma, early-onset senile cataract, and cystoid macular edema are relatively common complications of the disease, which accelerates permanent visual loss.²

Inverse RP is a rare form of RP that initially affects photoreceptors in the macula, causing significant visual impairment at very early stages of presentation. Autosomal recessive inheritance has been suggested. Many authors agree that this rare form of RP may correspond to cone-rod dystrophy with macular hyperpigmentation. However, diagnosis is difficult, and other inherited retinal disorders, such as Leber’s congenital neurosis, progressive cone-rod dystrophy, and central areolar choroidal sclerosis should be excluded.³

In this case report, we present a patient with an unusual association of inverse RP, scleromalacia, and neovascular glaucoma (NVG), which was treated with an intracameral anti-vascular endothelial growth factor (VEGF). To the best of our knowledge, this is the first report to show an association between RP and anterior segment neovascularization and scleromalacia.

Discussion

The presence of NVG and rubeosis iridis in a case of inverse RP was very unexpected. The most common cause of NVG is retinal vein occlusion, especially an ischemic type central retinal vein occlusion.⁴ To the best of our knowledge, there is only one report in the literature that mentions ischemic central retinal vein occlusion in a patient with RP.⁵ In this case, possible past ischemic central retinal vein occlusion may have been the cause of rubeosis iridis and NVG. Even in this hypothesis, NVG can be explained with ischemic central retinal vein occlusion; however, the reason for dense cataract presentation in the same eye in a 31-year-old patient could not be explained. While early-onset senile cataracts occur in RP, this patient was very young and the cataracts in both eyes were significantly asymmetrical.² The exact reason for progression of pathological new vessels could not be determined because the posterior segment of the globe was covered by cataract. This is the most significant disadvantage of this study, that the definitive cause of rubeosis iridis and NVG in a patient with RP could not be clarified.

Some reports have mentioned the coexistence of retinal neovascularization and RP.^6,7,8 One of these mentioned the presence of NVG in RP.⁸ However, the patient in that report had multiple ocular comorbidities including cataract, vitreous hemorrhage, subretinal exudation, and diffuse posterior pole edema.⁸ The patient had multiple ocular surgeries before NVG, including bilateral lens extraction and retinal detachment surgery on the fellow eye.⁸ The patient underwent multiple systemic steroid treatments, and there was no comprehensive investigation about NVG-related systemic inflammatory or ischemic conditions.⁸ Therefore, the relationship between NVG and RP was unclear and disputable in that case because there were many NVG-related risk factors other than RP. In contrast, NVG in our RP patient, who had no history of ocular surgery, was not associated with any other known ocular condition. In addition, the patient had no systemic NVG-related condition or history of steroid use. Therefore, it can still be argued that this case is the first presentation of NVG in a patient with RP.

Recurrent anterior uveitis attacks can be observed in RP; however, they generally do not cause neovascularization. Extensive ocular inflammatory diseases, including choroiditis, panuveitis, or scleritis can be reasons for general ocular ischemia and scleromalacia.⁹ These diseases may explain unilateral NVG and cataract, and some may result in scleromalacia. A weak point of this hypothesis is there was no history of severe ocular inflammatory diseases or clinical findings of past uveitis, such as synechiae, keratic precipitates, pigment on the anterior lens capsule, etc. The exact mechanism of anterior segment neovascularization in this case remains unclear and it should not be completely ruled out that the relationship between RP, scleromalacia, and NVG may be just a coincidence.

Bevacizumab is a humanized monoclonal antibody that affects all VEGF isoforms. Its injection into the anterior chamber can provide a rapid regression of neovascularization on both the iris surface and anterior chamber angle.¹⁰ In the current case, IOP decreased to a normal level 1 week after the intracameral anti-VEGF injection. Throughout the 3-year follow-up, stable IOP was provided with a single injection, without additional medication. A 3-year follow-up period is sufficient for the treatment of NVG, and as far as we know, this is the longest period showing the efficacy of a single dose of intracameral bevacizumab. In addition, to the best of our knowledge, this is the first case of a patient with scleromalacia receiving intracameral bevacizumab injection without any long-term complications. Although the pathogenesis of the anterior chamber neovascularization could not be fully explained, one of most important aspects of this study is that this is the first report to show the association of NVG, scleromalacia, and RP.