High myopia is commonly defined as severe nearsightedness with a refractive error of -6.00 diopters or greater, which significantly alters the physical shape of the eyeball. Retinal detachment is a severe medical emergency where the retina, the light-sensitive tissue lining the back of the eye, pulls away from the underlying supportive tissue. When this separation occurs, the retina is deprived of oxygen and nutrients, leading to a rapid loss of vision. For individuals with high myopia, the risk of experiencing this sight-threatening complication is notably elevated compared to the general population.
Quantifying the Risk of Retinal Detachment
Studies show that eyes with a spherical equivalent of -3.00 diopters or worse have a risk of detachment that is at least 10 times greater than that of non-myopic eyes. For individuals with high myopia, the lifetime risk of developing a retinal detachment is estimated to be up to 20 times higher compared to those with no refractive error.
The risk escalates with the severity of the myopia, demonstrating a direct correlation between prescription strength and vulnerability. Patients with extremely high myopia, measured at -9.00 diopters or worse, face a risk that can be over 21 times greater than their non-myopic counterparts. In terms of annual incidence, high myopes experience a rate of approximately 868 detaching events per 100,000 person-years, which is nearly 40 times the rate seen in non-myopic individuals.
Anatomical Changes Driving Increased Risk
The primary factor driving the increased risk is the physical elongation of the eyeball, known as increased axial length. In high myopia, the eye stretches from front to back, often exceeding 26 millimeters in length, causing the internal tissues to be continuously pulled taut. This stretching causes the retina to become significantly thinner and more fragile, particularly in the peripheral regions.
The thinned retina is highly susceptible to tears and holes, which are the typical precursors to detachment. Certain associated conditions, such as lattice degeneration, are far more common in highly myopic eyes. The vitreous humor, the gel-like substance that fills the eye, begins to liquefy and separate from the retina at an earlier age in myopic individuals.
As the vitreous pulls away, a process called posterior vitreous detachment, it exerts excessive traction on the already weakened and thinned retina. This pulling force can easily create a tear at a vulnerable point, such as a patch of lattice degeneration. Fluid from the vitreous cavity can then pass through this opening and accumulate underneath the retina, pushing it away from the blood supply of the underlying choroid and causing the detachment. In some cases of extreme elongation, an outward bulging of the posterior eye wall, called a posterior staphyloma, also introduces abnormal tractional forces that can lead to detachment starting at the center of the retina.
Recognizing the Urgent Warning Signs
Since retinal detachment is a painless condition, recognizing its acute visual symptoms is the only way to detect the emergency. The most common first sign is a sudden and dramatic increase in the number of floaters, which appear as specks, strings, or cobwebs drifting across the field of vision. This sudden shower of floaters indicates bleeding or debris released into the eye as the retina tears.
The next major symptom is the experience of flashes of light, often described as brief streaks of lightning, especially noticeable in the peripheral vision. These flashes occur because the vitreous gel is tugging on the retina, stimulating the light-sensitive cells. As the detachment progresses, a shadow or dark curtain begins to move across the side or center of the vision, representing the area of the retina that has lost function. Anyone experiencing these symptoms must seek an emergency eye examination immediately, as prompt intervention is necessary to prevent permanent vision loss.
Proactive Screening and Monitoring Strategies
For people with high myopia, proactive monitoring by an eye care professional is the most effective defense against permanent vision loss. Routine comprehensive eye exams should be scheduled at least annually. A thorough examination requires pupil dilation to allow the doctor to inspect the entire retina, especially the fragile peripheral areas.
The eye care professional will perform a scleral depressed examination, which uses gentle pressure on the outside of the eye to bring the far edges of the retina into view for detailed inspection. This technique is particularly effective for identifying peripheral lesions like lattice degeneration or small retinal holes before they progress to a full detachment. If a high-risk area, such as a retinal tear or significant area of thinning, is identified, the doctor may recommend a preventative procedure. This can involve using a focused laser to create small scars around the weak spot, sealing the area to the underlying tissue and preventing fluid from causing a detachment.