Published: 20 October 2021 | Updated: 28 September 2026 | Author: Smart Vision Optometry
Editorial and clinical update — 30 September 2026: The original article/interview below is preserved from the pre-project WordPress revision, including its attributed quotations and editorial structure. Numerical definitions, risk descriptions and pathologic-myopia terminology have been corrected to current International Myopia Institute guidance. Current evidence below should be relied on where older wording or risk estimates differ.
The “Not So Highs” and “Lows” of Myopia: Degrees of Myopia that Drive Greater Risk of Blindness
Myopia (nearsightedness) is a condition in which close objects are visibly clear, while distanced objects are blurred. This is understood as a refractive disorder that occurs as the eyeball elongates (gets longer). Myopia can cause exponentially more serious complications if the refractive error is severe, -5.00D or worse.
People with myopia have good near vision, and poor distance vision.
Gary Rodney, founder of Smart Vision Optometry and Fellow of the International Academy of Orthokeratology and Myopia Control (FIAOMC), explains the different degrees of myopia and how it leads to a great risk of age-related blindness.
The causes of myopia traditionally include genetics and the working environment. Now we are seeing that there does not have to be any evidence of genetic tendencies and a simple lifestyle can cause myopia to develop. Genetics simply makes the problem worse. The lifestyle factors include doing work focusing on close objects, like a computer screen, digital device, or book and/or less time outdoors in the daylight.
Rays of light that enter the eye, also influence the development of myopia. “Vision is made clear as light rays enter the eye through the cornea and lens, which bend the light to the retina at the back of the eye,” says Rodney. This gives a clear and sharp image. Therefore if a person is experiencing blurry vision they are experiencing a refractive error, as the light rays are not focused correctly at the back of the eye.
If not treated for prevention and not just compensation, myopia can progressively advance, causing other disorders that can result in blindness.
Low myopia
Current definition: The International Myopia Institute defines myopia as spherical-equivalent refractive error of ≤ −0.50 D and high myopia as ≤ −6.00 D. Refractive values should be written correctly in dioptres (D); the older numerical wording on this page has been corrected.
While there is no cure, vision treatment, management and control can be influenced using Smart Vision Optometry proprietary techniques with glasses, lenses or orthokeratology (Ortho-K). Ortho-K has been shown to produce a reduction in the rate of progress of myopia.
Studies have shown that children who spend long hours doing outside activities are at a lower risk of myopia. Progressive nearsightedness/myopia can cause vision impairment, including cataracts, macular degeneration, retinal detachment and myopia maculopathy.
High myopia
High myopia is associated with a greater risk of sight-threatening complications, including myopic maculopathy and retinal detachment. The International Myopia Institute defines high myopia as spherical-equivalent refractive error of ≤ −6.00 D.
High myopia and pathologic myopia are not interchangeable terms. Pathologic myopia refers to excessive axial elongation associated with structural changes in the posterior eye, such as myopic maculopathy or posterior staphyloma, that can reduce best-corrected vision. Retinal tears and detachment are separate complications for which risk increases with myopia.
Studies have shown that the higher myopia, the bigger the risk a person has of developing glaucoma. “As myopia worsens, retinal nerve fibre layers and macular thickness charge, increases the risk of glaucoma,” says Rodney.
Common risks to blindness led by myopia include retinal detachment, cataracts and glaucoma. These disorders may lead to visual impairment and blindness.
Retinal detachment
A thinned retina can cause retinal breaks. “Retinal detachment occurs when the retina detaches from the back of the eye,” says Rodney, and “if this detachment is not repaired urgently, it can cause blindness.”
Glaucoma
Glaucoma is a group of optic-nerve diseases that can cause irreversible vision loss. Raised intraocular pressure is an important risk factor, but glaucoma can also occur when measured eye pressure is within the statistically normal range.
Glaucoma is found significantly in those with myopia. In some cases, the eye can stretch out of its shape resulting in a refractive error. “The cause of high myopia inpatients should be examined,” says Rodney.
Cataracts
Cataracts are common among people with myopia. “This condition occurs when the eyes lens, located behind the pupil, has a cloudy appearance,” says Rodney.
Patients with high myopia can develop cataracts earlier than those with no refractive errors.
For current assessment and management information, read our myopia control and management guide.
Smart Vision Optometry clinics are located in Sydney. Book a Smart Vision Comprehensive Vision Skills Assessment or Advanced Eye Health Test for any child or adult by calling the Mosman clinic (02) 9969 1600 or the Bondi clinic (02) 9365 5047.
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Current evidence and clinical context
The International Myopia Institute’s definitions and classification report proposes ≤ −0.50 D as the threshold for myopia and ≤ −6.00 D for high myopia. It also distinguishes high myopia from pathologic myopia, which is defined by structural posterior-eye changes and their visual consequences.
The National Eye Institute’s myopia guide explains that myopia is diagnosed through an eye examination and that severe myopia increases the risk of other eye problems. A dilated retinal examination may be important when symptoms or level of myopia warrant it.
Urgent warning: sudden flashes, a sudden increase in floaters, a shadow or curtain in the vision, or sudden loss/distortion of vision can signal a retinal emergency and require urgent assessment.
Related Smart Vision reading
Myopia control and management · Myopic macular degeneration · Myopia and cataracts
Frequently asked questions
What prescription is considered high myopia?
The International Myopia Institute defines high myopia as spherical-equivalent refractive error of ≤ −6.00 D when accommodation is relaxed.
Is high myopia the same as pathologic myopia?
No. High myopia is a refractive definition. Pathologic myopia refers to structural changes in the back of the eye associated with excessive axial elongation that can reduce best-corrected vision.
Why does higher myopia need ongoing eye-health monitoring?
Higher myopia is associated with increased risk of conditions such as myopic maculopathy and retinal detachment. The appropriate review schedule depends on the person’s prescription, retinal findings, symptoms and other risk factors.
