Decoding the Numbers: Hyperopia
Welcome to Part 2 of Decoding the Numbers!
In the last post of this series, I discussed near-sightedness, or myopia. This time we're switching gears and talking about hyperopia!
*Note: From my experience, far-sightedness is a bit harder for people to grasp (unless, of course, they are hyperopic) than near-sightedness. I'll do my best to make it easy to understand, but bear with me, and don't be afraid to ask questions if something is confusing!*
- Patients with hyperopia, or hypermetropia, are commonly referred to as being “far-sighted”. This is because they are able to see more clearly at distance than at near. This becomes more pronounced as patients age.
What causes hyperopia?
- All refractive errors (essentially the reason for needing glasses) are caused by a mismatch of power in the eyes. In the case of hyperopia, the power (created by the cornea/clear surface and intraocular lens) is too little for the length of the eye, or, conversely, the length of the eye is too short for the power of the eye. Either case means that light is focused behind the retina (back part of the eye), resulting in a blurred image.
For those of you who are asking how in the world light can be focused behind the retina - you're not alone. Let's go back to myopia for a second. In this case, light from a distance is focused in front of the retina. As objects get closer to the retina, so does the image, until, at a certain distance, the image falls exactly on the retina!
Unfortunately, this doesn't happen with hyperopia. Distance light is already behind the retina, and no matter how you physically move the source of light, it will never be on the retina. What changes is just how far behind the retina the focal point is. As objects come closer and closer, the image moves farther and farther behind the retina.
However, in hyperopia, there's a bypass mechanism called accommodation (think focusing the eyes). When your eyes accommodate, the physical lens within your eye changes shape and, consequently, power. It takes work, but, with modest amounts of far-sightedness at younger ages, the lens can compensate for the prescription!
Why do we need lenses?
- At younger ages, people with mild to moderate far-sighted prescriptions often don't need glasses for distance, because, like I said, they can compensate! However, the higher the prescription, the harder this is.
- Though many younger people with hyperopia are able to compensate at distance, they may need reading glasses to help relax their eyes at near. Remember, as objects get closer to the eye, the image moves further behind the eye, causing the eye to even harder at near.
- Additionally, as we age, the eye naturally loses its ability to focus due to changes in the structure of the lens. For this reason, people with a far-sighted prescription eventually become unable to compensate... at any distance. Sorry guys!
- Because of the mismatch between the retina and the image, plus (convex) lenses are prescribed. Due to their structure (thicker in the center, thinner on the edges), convex lenses cause light to converge (get closer together). This convergence moves the eye’s natural focus point forward - putting it right on the retina, and providing a clear image.
Who gets hyperopia?
- Refractive errors in general are thought to be inherited. Hyperopia is no different.
- Almost everyone starts out far-sighted in infancy secondary to the eye being shorter at birth and growing over time. In most people, this gradually decreases over the first several years of life in a process known as emmetropization. However, with high far-sighted prescriptions the amount of hyperopia is less likely to decrease over time to normal ranges.
- The most common genetic condition associated with far-sightedness is Down Syndrome.
When should I suspect hyperopia?
- Some signs of being hyperopic are:
- Complaining of headaches, eyestrain, or fatigue when reading/doing near tasks
- Some people may have an inward eye turn that gets worse when they're looking at things close up
- (Occasional) squinting when looking at distance (normally only with higher prescriptions)
Does hyperopia get worse?
- Unlike myopia, hyperopia rarely increases!
- Rather, at young ages, far-sightedness naturally decreases (more so if it's not super high to begin with)
Are there any complications with being far-sighted?
- High amounts of uncorrected hyperopia (greater than +5.00) at a young age may cause permanently (with some nuances) reduced vision (amblyopia).
- As hyperopia is often associated with a shorter eye, with age, far-sighted individuals may be more prone to developing problems with the outflow of fluid in the eye (angle-closure, or angle-closure glaucoma).
- Far-sighted patients have an increased likelihood of having an eye turn (strabismus).
Can hyperopia be treated?
- Most often, patients are prescribed glasses or contacts to improve vision.
- Refractive surgery can also be used to change the power of the eye.