OVERVIEW
Sickle cell anemia is a genetic defect in hemoglobin that can be divided into several types, with the severity of ocular lesions varying by type. Sickle cells are crescent shaped like a sickle, and are more susceptible to sickling, especially under low oxygen conditions. This sickle red blood cell is harder than normal red blood cell, not easy to deform, so it is easy to block the small retinal arteries, especially the peripheral small arteries, resulting in retinal ischemia. The lack of oxygen in the tissue is more likely to prompt the sickling of red blood cells, thus causing a vicious circle.
Causes
Sickle cell anemia ophthalmopathic patients 90% to 100% have hemoglobin S. Sickling cells slow down the blood flow in the microcirculation and lead to the development of the disease.
Symptoms
The main lesion is retinal ischemia and its complications, which is the most common feature of other vascular diseases such as diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity.
1. Proliferative sickle retinopathy (PSR) is divided into five stages
(1) Small artery obstruction The lesion is located in the peripheral part of the retina, the small artery obstruction is silvery or white line, the small vein reflux is also blocked, forming a peripheral non-perfusion area, the area of the retina is grayish-brown, the tissue is blurred, and the normal orange-red fundus is a clear contrast.
(2) Arteriovenous short circuit At the occlusion of small arteries, the capillaries located on the side of the arteries are enlarged and traffic with the veins, forming arteriovenous traffic branches, which are often located between the nonperfused area and the perfused area. Fluorescence angiography shows that the walls of these arteriovenous short circuits do not leak.
(3) Neovascularization Neovascularization occurs most frequently in the peripheral retina over the temporal area, followed by the inferotemporal, supranasal, and subnasal retinas.
(4) Vitreous hemorrhage Neovascularization begins to grow parallel to the retinal surface, and later breaks through the inner border membrane to reach the center of the vitreous through the base of the vitreous, with leakage of fluid into the retina.
(5) Retinal detachment Due to the proliferation of neovascularization, the contraction and pulling of the mechanized membrane or strips, the retina adjacent to the vascular membrane forms a rupture hole, which is in the shape of an oval or horseshoe, resulting in retinal detachment.
2. Non-proliferative sickle retinopathy
Non-proliferative lesions include the following:
(1) tortuous dilatation of retinal veins in the peripheral and/or posterior pole;
(2) Black sunburst spots, characterized by a 0.5 to 2PD-sized black spot with clear borders in the equatorial portion of the retina, similar to a retinal choroidal scar, but with an irregularly star-shaped or needle-shaped border, resembling a sunburst-shaped pin embedded with a gemstone;
(3) Glittering dot-like deposits, with shiny granular dots deposited near the lesion, resembling cholesterol crystals, but not lipid-like;
(4) Salmon spot hemorrhages, hemorrhages into the subinner border membrane or into the retina, occasionally between the retinal pigment epithelium and photoreceptors, in the form of ovoid, 0.25 to 1 PD red spots, with the color changing from pink to orange-red and finally to white;
(5) Other ocular symptoms may include segmented conjunctival vessels, occasionally combined with angioid streaks, or retinal arterial or venous obstruction.
Examination
Routine blood tests and genetic tests. Fundus examination can detect ischemic lesions and their complications.
Diagnosis
Diagnosis is made on the basis of family history, a positive sickle test, findings on fundus examination, hemoglobin electrophoresis, and clinical presentation.
Complications
Vitreous hemorrhage and retinal detachment are common complications.
Treatment
Closure of neovascularization is the key to treatment, and argon laser or cryotherapy can be used. Argon laser treatment can completely close the neovascularization in most cases.