Revealing the Hidden Impact: Essential Thrombocythemia (ET) and Its Effects on Ocular Blood Vessels through Optical Coherence Tomography Angiography (OCTA) Imaging

Objective: To explore retinal vascular changes in patients with Essential Thrombocythemia (ET) using Optical Coherence Tomography Angiography (OCTA) and to examine the relationship between vascular density and clinical indicators such as visual acuity(VA) and thrombotic events.

Methods: Twenty patients diagnosed with ET based on the 2022 WHO classification and diagnostic criteria between 2023 and 2024 were enrolled, along with 20 healthy controls, for a total of 40 eyes per group. All participants provided written informed consent. OCTA was utilized to assess the superficial retinal capillary plexus (SRL), deep retinal capillary plexus (DRL), and conjunctival capillary plexus of the macular retina in each eye. The study aimed to compare changes in superficial large vessels (SMAR), deep large vessels (DMAR), total vessels (STMI, DTMI), microvessels (SMIR, DMIR), and temporal conjunctival vessels between ET patients and healthy controls. Retinal areas were analyzed using the following methods: A. Early Treatment Diabetic Retinopathy Study (ETDRS) grid, dividing into superior (S), left (L), inferior (I), and right (R) regions; B. Cerebral hemisphere method, dividing into left upper (SL), left lower (IL), right lower (IR), and right upper (SR) quadrants; C. Central circular method, categorized into C1-C6.Each captured image was analyzed according to these designated areas and methods.

Results: This study included 20 patients with ET. The median age at onset was 57 years, with a range from 18 to 76 years. The cohort comprised 17 males (85%) and 3 females (15%). Genomic DNA isolated from bone marrow samples was analyzed for JAK2/V617F, MPLW515K/L, and CALR mutations. The results revealed that 18 patients (90%) tested positive for JAK2/V617F or CALR mutations, with JAK2/V617F being the most prevalent (65%). Two patients (10%) were negative for JAK2, CALR, and MPL mutations, classified as "triple-negative genotype (TN)". Five patients (25%) experienced thrombotic events.

OCTA analysis demonstrated a decrease in microvascular density in both the superficial retinal capillary plexus (SRL) and deep retinal capillary plexus (DRL) among ET patients. Specifically, in the SRL, reductions were noted in the total vessel metrics (STMI), microvessel density (SMIR), and large vessels (SMAR) (P<0.001). In the Early Treatment Diabetic Retinopathy Study (ETDRS) grid, vascular density was significantly lower in the superior (S), left (L), inferior (I), and right (R) areas (P<0.001). The hemispheric division revealed significant reductions in the superior right (SR), superior left (SL), inferior left (IL), and inferior right (IR) regions (P<0.001). The central circular method showed reduced vascular density in areas C1-C4 and C6 (P<0.05). In the DRL, decreases in total vessels (DTMI) and microvessels (DMIR) were significant (P<0.001), although reductions in large vessels (DMAR) were not significant. The ETDRS grid demonstrated lower vascular density in the S, L, and I areas (P<0.01). The hemispheric division showed reductions in the SL, IL, and SR regions (P<0.05), and the circular method indicated decreased vascular density in C1-C2 (P<0.001). Additionally, temporal conjunctival microvascular density was significantly lower in ET patients compared to controls (P<0.05).

A positive correlation was found between microvessel density (MIR) in the SRL's SR and R regions and visual acuity (VA) (r=0.568, P<0.05; r=0.389, P<0.05), and between MIR in the DRL's R and C1 areas and VA (r=0.340, P<0.05; r=0.384, P<0.05).

In patients with thrombotic events, OCTA revealed a significant decrease in vascular density in the C1 area of the SRL (P<0.05) and a significant increase in the C5 area (P<0.05). In the DRL, patients with thrombotic events exhibited significant increases in vascular density in the C3 and C6 areas (P<0.05).

Conclusion: OCTA measurements reveal a significant reduction in retinal microvascular density within both the SRL and DRL in patients with ET compared to healthy controls. Notably, patients who experienced thrombotic events exhibited reduced microvascular density in central retinal regions and increased density in peripheral areas, in contrast to those without thrombotic events. These findings underscore the utility of OCTA in monitoring retinal microvascular changes associated with ET and in elucidating the underlying mechanisms of thrombosis in this condition.