Why can't people with high myopia donate blood?
High myopia is defined as refractive error with a degree greater than 600 degrees (greater than 400 degrees for children). Because this type of myopia is often accompanied by pathological changes in the eye, blood banks generally discourage blood donation. Generally speaking, mild myopia (less than 300 degrees) has few complications, while in high myopia (greater than 600 degrees), the anteroposterior diameter of the eyeball is significantly elongated, but the retina cannot lengthen accordingly. This leads to retinal elongation and diffuse atrophy, and the corresponding blood vessels become increasingly thin. This makes the blood vessels very sensitive to changes in blood pressure, and the vitreous humor can change from a gel-like state to a liquefied state.
During blood donation, blood pressure may fluctuate slightly. For highly myopic individuals whose retinal blood vessels are stretched thin, this slight fluctuation can cause retinal vascular spasm, leading to retinal tears in already damaged areas. At this point, liquefied vitreous humor can enter the subretinal space, causing retinal detachment and severely affecting vision. Therefore, from the perspective of protecting the safety of blood donors, it is recommended that highly myopic individuals not donate blood.
Experts indicate that myopic blood donors are not uncommon. Because my country's blood donation regulations do not explicitly specify the degree of high myopia, considering factors such as astigmatism, in practice, a threshold of around 500 degrees is generally used as a benchmark, and myopic donors are patiently persuaded not to donate.
What complications can high myopia cause?
1. Floaters: People with this condition often see black shadows floating in their field of vision as their eyes move, like flies or mosquitoes. This is due to the liquefaction of the normal colloidal structure of the vitreous humor.
2. Macular Hemorrhage: In people with high myopia, the enlarged eyeball constantly pulls on the eyeball wall, causing metabolic disorders in the retina. In particular, small blood vessels in the macula rupture due to this tension, leading to macular hemorrhage, which severely impairs central vision. At this time, the patient feels a fixed black shadow blocking their vision. Although the hemorrhage can be absorbed with treatment, it will always leave some bloodstains, affecting vision to varying degrees.
3. Retinal Detachment: This is a relatively serious complication with complex causes. Internally, the retinal tissue in patients with high myopia becomes weak due to degeneration and atrophy, making it extremely prone to retinal detachment and blindness. Externally, accidental impacts from external forces, conducted through the vitreous humor, can cause retinal tears, leading to retinal detachment and blindness.
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Post time: Jan-16-2026