Optometry in Focus: Macular Degeneration

Happy Friday, y’all!
First things first: if you haven’t guessed it by now, here’s the official notice – I will probably not be blogging here every week of 2021.  In fact, I know I won’t.
 
The 1/1/21 version of Hannah was feeling very ambitious when she made that goal… while concurrently starting a 100 day blog, increasing the daily patient load, working out more consistently, learning organ, organizing service music, and attempting to foster a social life.
 
Too ambitious.
 
And so, the 2/1/21 version of Hannah (or 2/5… whatever), is backing that goal down to something more realistic.  Like, maybe a post a month.
 
Maybe.
 
Okay, now, all disclaimers aside, let’s get to eyes.
 
 
As I have, somehow, managed to switch my career to the complete opposite end of the age spectrum, from pediatrics to the (often) very advanced in age (believe it or not, the exam techniques are pretty much identical), the primary diseases that I’m working with have changed as well.
 
The last two weeks, I have had the pleasure of discovering macular degeneration in a plethora of patients who didn’t know (or at least didn’t remember being told) that they had the condition.
Which, I guess, makes this the perfect time for a (somewhat) in-depth discussion on the disease.
Let’s get started.

What is Macular Degeneration?

Age-related macular degeneration, or AMD, most simply put, is a disease that causes a degeneration, or breakdown, of the macula, or most central part of the vision.

What happens in Macular Degeneration?

All macular degeneration starts with the dysfunction of special retinal cells called the retinal pigmented epithelium (RPE).  These cells are responsible for maintaining the health of the photoreceptors (light-receiving cells).  Without the RPE doing their job, byproducts build up, creating a toxic environment (with lipofuscin) and disruption of physical cell apposition (drusen), eventually leading to photoreceptor death.

During this process, the immune response is also activated, further damaging cells and, at times, leading to the formation of new blood vessels.  Unfortunately, the blood vessels that form, form quickly, and with improper barriers, allowing blood to leak from the vessel walls.  This blood is also toxic to retinal cells, causing further vision loss.

What causes Macular Degeneration?

The complete cause of AMD is unknown, however, all current research points to several factors coming into play in the disease process.
  • Genetics: Macular degeneration tends to run in families.  Not all of the genes responsible for AMD have been isolated, but a specific gene has been found that seems to explain ~50% of AMD cases.
  • Oxidative stress: Okay, so we all know that “oxidative stress is bad” and “anti-oxidants are good”, but how many of you have thought back to the mechanism of action behind this line of thought?  For those of you who haven’t, here’s a quick review:
    • In the process of cellular respiration (aka metabolism), glucose and oxygen are combined to create carbon dioxide, water, and energy through oxidative phosphorylation.  However, sometimes this process doesn’t work properly, and creates free radials (or reactive oxygen species) that easily react with, well, whatever they run into.  Over time, this can cause permanent damage to the cell/tissue/organ.
    • The eye, specifically the macula, has the highest metabolic rate of the entire body. Which means that it has the highest potential for free radical formation, and consequently, permanent damage from oxidative stress.
  • Inflammation: We already talked about this one, but, for those of you who missed the memo, inflammation, especially chronic inflammation, is really hard on the body – eye included.
  • Protein deposition: Again, this was mentioned above, but for a slightly different wording, physical separation, by any cause, of the RPE and photoreceptors is a recipe for cell death.

Type of AMD

Generally, AMD is divided into two types: dry, and wet.
  • Dry macular degeneration is characterized by a lack of neovascularization (leaky blood vessels).
  • Wet macular degeneration is characterized by the presence of neovascularization.

Unfortunately, these two types are not mutually exclusive.  Most individuals start out with dry macular degeneration, and may or may not progress to wet macular degeneration over the years.

Signs and Symptoms of AMD

From a patient standpoint, the earliest signs of AMD are normally distortions in central vision, or mild decrease in visual acuity.
 
Over time, this progresses to significant decreases in central vision.
 
*Note: I said central, because this condition ONLY AFFECTS the very center part of vision.  Side vision? That remains unscathed.  For this reason, patients with AMD may have a hard time reading, picking up small objects, or recognizing faces, but they won’t be running into walls, despite having a visual acuity that may be recorded as hand motion, or counting fingers at ___ feet.
From a clinical perspective, the first changes that I may see are generally drusen (cellular deposits) and pigmentation changes in the macula.  Over time, the drusen generally increase in number, and atrophy (or tissue loss) at the macula becomes more obvious.   In some (wet) cases, there may be bleeding or blood around the macula. In other (dry) cases, there may be significant atrophy – to the point where we describe it as “geographic.”  Finally, in very late stage (wet) AMD, there may only be a large (disciform) scar visible in the area where the neovascular net/membrane previously was.

Who gets AMD?

Macular degeneration has several known risk factors:
  • Age (with the risk being highest for those over 80)
  • History of smoking
  • Obesity
  • Family history
  • Being caucasian
  • History of excessive UV exposure

Treatment for (and Prevention of) Macular Degeneration

One of the greatest preventions for AMD is simple: DON’T SMOKE.
 
(Yes, that is in all caps, bolded, underlined, and italicized. This is the number one modifiable risk factor.  You can’t change your age.  You can’t change your family history.  You can’t change your race.  But you can change whether or not you smoke.  And yes, even if you’ve smoked before, STOPPING NOW IS BENEFICIAL!)
 
The second greatest prevention? Eat right.  No, I’m not a dietician, and can’t tell you 100% what you should eat, but a healthy diet with healthy fats and green leafy vegetables has been shown to increase systemic inflammation – and that affects your eyes too.
 
For those who already have AMD:
 
With dry AMD, I always tell my patients that there’s good and bad news.  The good news is, it generally progresses slower, and may never result in super significant vision loss.  The bad news? There’s not much we can do for it. Some people suggest “eye vitamins”, but really, the specific AREDs formulation has only been shown to have an effect in eyes that already have moderate to severe disease.  And so, those are the only ones that I really suggest it for.  Otherwise, just pay attention to your vision, and come in if you think you’re noticing changes.
With wet AMD – good news! There are treatments!
Unfortunately, they’re generally shots.  In your eyes.
However, these intraocular medications have been proven to reverse blood vessel growth.
 

Prognosis

If I’m honest, prognosis is probably the hardest part for me to talk about with patients, because there’s no guarantee.  Some people stay at early to intermediate stages indefinitely, and notice relatively mild visual changes.  Other people progress more quickly, and have much more significant visual concerns. At the end of the day, the only thing I can promise is this: as an eye doctor, I will do my best to help each of my patients see as much as possible for as long as possible.
 
Sometimes that means taking vitamins.
Sometimes that means a referral to a retinal specialist.
Sometimes that means working to find the right magnifiers for reading and other near tasks.
Sometimes that means a relatively minor glasses change that helps you feel more visually confident.
Sometimes that means finding filters that increase contrast to help in certain environments.
Sometimes that means educating about lighting – when it may be too much, or too little.
Sometimes that means connecting you with a center that works with the visually impaired.
Sometimes that means a referral to vision or occupational therapy to learn how best to use your remaining vision.
Sometimes that means having the hard conversations about not being able to drive anymore.
And sometimes that means just being there while you process the information, and being available to talk if you need to.
 
 
 
 
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