Sickle cell disease (SCD) can affect the vascular bed of any part of the eye, including the conjunctiva, iris and anterior segment, optic nerve, retina, and choroid (Figure 20-1).1 Fortunately, severe vision loss in patients with SCD is rare. Proliferative sickle cell retinopathy (PSR), in which pathologic preretinal neovascularization occurs, is the most common cause of significant vision loss in patients with SCD.2-4
Diagram of the eye. Note the peripheral location of many of the pathological events.
Detection of sickling within the eye can be observed directly by the practitioner using conventional diagnostic instruments (well-illuminated magnifying devices such as the ophthalmoscope and also the slit lamp biomicroscope). Both transient and permanent effects of intraocular sickling are virtually pathognomonic, especially in the white of the eye (conjunctiva) and in the ocular fundus (retina and associated tissues). In the fundus, potentially blinding complications of sickling can be identified and treated. Growth of neovascular tissue in the retina, PSR, is usually treated by laser photocoagulation or by intraocular injection of anti–vascular endothelial growth factor (VEGF) agents (eg, bevacizumab and others). Intraocular blood clots within the vitreous chamber in the rear of the eye can be treated surgically. Blood clots in the front (anterior) chamber of the eye can be treated with surgical evacuation.
This chapter includes discussions of the following topics: pathophysiology and epidemiology of vision loss in SCD; sickle cell hyphema (blood in the anterior chamber of the eye and its induced ocular hypertension, which can be blinding); natural history of SCD affecting the peripheral and also the central macular portion of the retina; the classification of PSR; imaging modalities for both the front and back portions of the eye; treatment techniques; and screening advice. The chapter concludes with illustrative cases and “High-Yield Facts.”
The risk for permanent and severe vision loss is highly correlated with SCD genotype. PSR lesions can be identified through regular dilated fundus exams and may potentially regress with or without treatment. Herein, we discuss how SCD affects the eyes and our recommendations for evaluation, management, and prevention of vision loss related to SCD.
Pathophysiology and Risk Factors for Loss of Vision in SCD
Risk factors for loss of vision in SCD are primarily understood to be those that predispose to PSR, including genotype, age, and systemic SCD therapy. Individuals with the homozygous genotype (HbSS), although more likely to experience higher rates of vaso-occlusive crises and overall morbidity and mortality, are counterintuitively less likely to experience PSR and subsequent loss of vision as compared to individuals with compound heterozygous mutations (eg, HbSC) or those with hemoglobin S (HbS)-β thalassemia. Reasons for this are not fully understood. However, it is likely that in HbSS, small arterioles throughout the retina frequently undergo complete occlusion, causing ...