Having myopia (nearsightedness) can be the pits, especially when your prescription is high. You can’t see anything clearly beyond a foot or two of your eyes without the assistance of glasses or contact lenses! Luckily, glasses and contact lenses correct myopia well for most people. Not all myopia is created equal, however. Some prescriptions come with increased risk of not just seeing the clock on the nightstand without glasses, but sight threatening issues that can leave permanent vision loss or blindness.
You know you have myopia if your glasses or contact lens prescriptions have a negative (vs. a plus) sign in front of the first number (i.e. -4.25) or your vision is blurry in the distance but clearer when looking at things up close. Prescriptions higher than -6.00 or, less commonly measured, axial length of 26.5 mm are considered “high myopia”. There is another subset of myopia that affects 3% of the world population called “pathologic” or “degenerative” myopia. These patients have high myopia WITH physical degenerative changes in the back of the eye that results in progressive worsening of myopia and possibly irreversible vision loss during the most productive years of life.
How does pathological myopia affect the retina?
- Retinal detachment – the thin tissue lining the inside of the eye allowing us to see detaches from its blood supply.
- Retinal atrophy – areas where your retina has become very thin and is no longer working.
- Lattice degeneration – a type of retinal thinning at the far peripheral edges of the retina.
- Lacquer cracks – breaks that occur in the membrane (Bruch’s membrane) between the retina and its underlying blood supply (the choroid layer).
- New blood vessels (myopic choroidal neovascularization) – new leaky blood vessels can grow from the blood supply underneath the retina (from the choroid layer), through lacquer cracks or areas of atrophy onto the retina.
- Myopic macular degeneration – these degenerative changes can develop at the macula (the central part of the retina). Myopic macular degeneration is also known as myopic maculopathy and can affect your central detailed vision.
Because of the increased risk of sight threatening complications, patients with high myopia should have dilated eye examinations more frequently than average to look for any of these changes as treatments by a retinal specialist can reduce the risk of severe vision loss. If you do have a highly myopic prescription it is important to see your eye care professional immediately if you notice any strange visual symptoms or changes to your vision such sudden loss of vision, flashing/sparks of light that others do not see, and/or the appearance of moving floaters in your vision that others do not see.
By Jordan Keith, OD, FAAO