Why Hospitals Ban Blood Donations for Those with Severe Myopia

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Title: Why Hospitals Ban Blood Donations for Those with Severe Myopia

Introduction: Patients with high myopia are restricted from donating blood due to risks of retinal tears from intraocular pressure fluctuations.

Keywords: ['health', 'safety']

At blood donation vehicles or blood centers, staff usually ask a question: "What is your degree of myopia?" If the answer exceeds 600 degrees, the individual is often politely declined.

Many people find it hard to understand: my blood quality is completely normal, and I'm in great shape, so why do I lose my eligibility to donate blood just because I wear thick glasses? In fact, this regulation is not due to a dislike of blood quality, but rather for the medical safety protection of the blood donors themselves. The core logic behind it is to avoid the potential risk of retinal detachment.

1. Basics of Anatomy: The Delicate Structure of the Retina

In medicine, myopia greater than 600 diopters (-6.00D) is defined as high myopia.

The normal axial length of an adult's eye is about 24 millimeters. In patients with high myopia, the axial length of the eye typically increases significantly, exceeding 26 millimeters or even longer. The wall of the eyeball consists of the sclera, choroid, and retina, from the outside to the inside. As the axial length elongates, the wall of the eyeball is forced to expand and stretch. Since the elasticity of the retina is much lower than that of the sclera, this expansion can lead to excessive stretching and thinning of the retina.

This thinning mainly occurs in the peripheral region of the retina, making it susceptible to lattice degeneration, cystoid degeneration, and even retinal tears. This places the fundal structure of highly nearsighted patients in a highly unstable "subhealthy" state, significantly reducing their tolerance to fluctuations in blood pressure and changes in intraocular pressure compared to normal individuals.

II. Inducing Mechanisms: Hemodynamics and Intraocular Pressure Fluctuations

Although blood donation itself (usually 200 to 400 milliliters) has a minimal impact on the circulatory system of healthy individuals, there are two potential risk factors for people with high myopia.

Intraocular pressure fluctuations: During the blood donation process, some donors may experience a stress response due to nervousness, pain stimulation, or the sight of blood, leading to sympathetic nervous system activation and a sudden increase in blood pressure. This fluctuation in blood pressure may be transmitted to the intraocular vessels, resulting in a temporary rise in intraocular pressure (IOP). For patients with already degenerated and thinned retinas, abrupt changes in eye pressure may stress the retina, potentially causing tears or detachment.

Hemodynamic changes: Blood collection in a short period can lead to a decrease in the total circulating blood volume. Although the body can quickly compensate, the perfusion of the choroidal and retinal blood vessels may experience minor fluctuations. In patients with pathological myopia (accompanied by fundus lesions), these microcirculatory changes could trigger vascular spasms or hemorrhages in the fundus, thereby endangering vision.

Three, Industry Standards and Risk Mitigation

One misconception that needs to be corrected is that national standards do not absolutely prohibit blood donation for individuals with high myopia.

According to China's latest "Health Examination Requirements for Blood Donors" (GB 18467-2011), "high myopia" is not explicitly listed as a permanent disqualification. It only stipulates that individuals with high myopia who have changes in the fundus are temporarily ineligible to donate blood.

However, in practice, blood centers and donation sites often implement stricter measures, frequently refusing individuals with a hemoglobin level above 600. The reason for this is:

Screening costs: The blood donation vehicle is not equipped to perform pupil dilation and detailed fundus examinations. Staff members are unable to determine whether a person with high myopia has developed retinal tears or degeneration.

Defensive medicine: To maximize the safety of blood donors and avoid serious medical disputes such as retinal detachment, blood collection agencies tend to adopt a one-size-fits-all exclusion strategy.

4. Conclusion

Hospitals or blood donation centers refusing blood donations from individuals with high myopia is essentially a risk control measure.

Although the statistical probability of blood donation directly causing retinal detachment is very low, for patients with high myopia who are characterized by extremely long axial length and very thin retinas, any activities that may lead to dramatic fluctuations in eye pressure or changes in hemodynamics—such as intense exercise, bungee jumping, heavy physical labor, and blood donation—are considered risk factors. This degree of caution is entirely warranted for that delicate, gossamer-thin retina.