Sir,

Since the first report of hemoglobin (Hb) AC retinopathy,1 few cases have been described and the pathogenesis remains obscure.2 Significant intraoperative bleeding may make vitrectomy for proliferative retinopathy from sickling hemoglobinopathies challenging.3

Case report

A 33-year-old African American male, with idiopathic hypertension and mild renal failure, complained of decreased vision in his right eye for 6 months and floaters in his left eye for 2 years. Right and left visual acuities (VA) were 6/18 and 6/7.5, respectively. Anterior segments were normal. Fundoscopy showed vitreous hemorrhage (VH), right more than left; sclerotic retinal vessels, more so inferiorly (right more than left); and preretinal fibrosis with localized traction retinal detachments in the midperiphery of both eyes (Figures 1a and b). Fluorescein angiography showed neovascularization, capillary dropout and capillary remodeling (Figures 1c and d). Infective and autoimmune laboratory screen was negative. Hematological assessment revealed Hb AC (A=56.9%, A2=2.8%, F=0.7%, C=39.6%), no sickling, and a normal blood count with an Hb level of 15.0 g/dl. Blood sugar was normal and creatinine was mildly raised to 1.5 mg/dl.

Figure 1
figure 1

Left eye imaging. (a, b) Pretreatment color photographs show neovascularization, preretinal fibrosis and equatorial hemorrhage. (c, d) Pretreatment fluorescein angiography shows neovascular leakage from the preretinal fibrotic membranes, vascular remodeling of the posterior pole and capillary dropout at the midperiphery. (e) At 3 weeks after scatter laser therapy, color photograph shows a good laser pattern peripheral to preretinal hemorrhage of the superonasal equatorial region. (f) At 8 months post vitrectomy, the retina is fully attached with islands of segmented fibrosis, with visual acuity of 6/7.5.

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Scatter photocoagulation was placed in the anterior retina in both eyes. Three weeks later the left VH worsened (Figure 1e). One month later, VA remained at 6/60, due to nonclearing central VH, and possibly macular traction. After receiving 1.25 mg IVB 5 days before surgery, the VH and preretinal fibrosis were removed and the retina attached, with postvitrectomy VA stable at 6/7.5 (Figure 1f).

The right VH worsened 2 months after laser treatment. Because of nonclearing VH and tractional detachment threatening the macula, this eye was vitrectomized 4 months post laser with VA at 6/45. IVB of 1.25 mg was given 5 days before vitrectomy. The VA improved to 6/18, with persistent inferior macular ischemia (similar to presurgery; Figure 2).

Figure 2
figure 2

Right eye color photograph 4 months postvitrectomy. The retina is fully attached with islands of segmented preretinal fibrosis. Bands of subretinal fibrosis are seen temporal to the macula. Inferior macula and disk are ischemic and atrophic, as they were presurgery, with visual acuity of 6/18.

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Comment

The present understanding of Hb C trait retinopathy is that it is extremely rare and, like Hb S trait retinopathy, only occurs with comorbidities.4 We theorize that the increased blood viscosity (due to Hb AC), and the narrowed vessels (due to hypertension), acted synergistically to cause occlusive microangiopathy, which lead to proliferative neovascularization. Our case demonstrates how two non-neovasculogenic diseases, if coexisting, can cause sight-threatening retinopathy.

Because the preretinal fibrosis leaked fluorescein (Figures 1c and d), we used preoperative IVB to decrease bleeding when cutting these fibrovascular membranes. The right eye VA did not improve beyond 6/18 after surgery because of preexisting disease-related ischemic maculopathy. As reported by others,5 we did not see IVB-related complications, such as worsening of the traction retinal detachment and macular ischemia.