AAO 2023: OCT and OCTA longitudinal study further highlights macular thickness and microvascular changes in children with sickle cell disease

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Reviewed by Sandra Hoyek, MD, and Nimesh A. Patel MD

A collaborative investigative effort found that optical coherence tomography (OCT) and OCT angiography (OCTA) imaging were especially valuable in this patient population because the images extended the current definition of sickle cell retinopathy. The findings can serve as biomarkers of disease severity and help monitor disease progression in children over time, according to Sandra Hoyek, MD, lead author from the Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston.

She was joined in the study by principal investigator, Nimesh A. Patel MD, and others from the Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, and the Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore.

(Image Courtesy of Sandra Hoyek, MD)

The investigators explained the rationale for their study, ie, that there has been little published on sickle cell maculopathy (SCM) in children with sickle cell disease. No longitudinal studies have investigated progression of retinal thinning and vessel density changes over time in this patient population.

For this reason, the research team longitudinally assessed the macular thickness and microvascular changes in a retrospective consecutive series of children with sickle cell disease.

The study was conducted at Boston Children’s Hospital from January 1998 to August 2022. The primary outcomes were the total retinal thickness obtained by OCT in the macula, the vessel density in the superficial and deep capillary plexuses and the foveal avascular zone (FAZ) area obtained by 6 x 6- mm OCTA scans.

The key findings in the study were as follows:

• Sickle cell disease can affect the macula without necessarily presenting the classic peripheral findings. This underscored the usefulness of OCT as a diagnostic tool in screening pediatric patients with sickle cell disease.
• Gradual retinal thinning can start when children are young and may be secondary to chronic ischemia rather than acute occlusion.
• A possible compensatory increase in the vessel density nasally may be a response to temporal macular atrophy.
• HbSC, a genotype of sickle cell disease, ismore frequently associated with peripheral sickle cell retinopathy
• HbSS, another genotype, is correlated more with temporal macular thinning

(Image Courtesy of Nimesh A. Patel, MD)

The investigators forwarded their hypothesis on the pathogenesis of sickle cell maculopathy, that is, the initial loss of vessels temporally, leading to chronic ischemia, progressive retinal thinning, and the compensatory increase in vessel density nasally.

The researchers also proposed the distinct pathophysiologies of sickle cell maculopathy and sickle cell retinopathy. They explained that the former may be related to the severity of the systemic disease, resulting in chronic low perfusion of the temporal paramacular watershed zone, and that the latter may be associated with higher blood viscosity.

Hoyek and colleagues enumerated the study findings.

• The temporal retinal thinning in pediatric patients with sickle cell disease was progressive and occurred in eyes with and without peripheral sickle cell retinopathy.
• A compensatory nasal increase in the vessel density in the deep capillary plexus was seen on OCTA images.
• Eyes with peripheral sickle cell retinopathy had a larger FAZ, lower temporal deep capillary plexus vessel density, and higher nasal deep capillary plexus vessel density compared with patients without peripheral sickle cell retinopathy.

While the HbSC genotype was associated with higher rates of peripheral retinopathy, patients with the HbSS genotype had more severe macular atrophy.

OCT and OCTA findings could supplement the current definition of sickle cell retinopathy, serve as biomarker of disease severity, and help monitor disease progression in children over time.