"Help, I'm Losing My Vision"
Chat Highlights
June 22, 2005

On Wednesday, June 22, 2005, Dr. Rick Wilson a glaucoma specialist at Wills, and the glaucoma chat group discussed "Help, I'm Losing My Vision."

Moderator:  Welcome back to chat, Dr. Wilson.  Tonight our topic is "Help, I'm Losing My Vision.”  Some patients here are already losing vision and fear that loss will continue.

Dr. Rick Wilson:  Clearly, that's a very scary thought.

Moderator:  Definitely. And a scarier experience.

Dr. Rick Wilson:  I think knowledge is the best defense against fear. In my practice I very rarely see patients under medical treatment lose the last of their vision to glaucoma. That is because I carefully select the patients who are at significant risk for worsening of their glaucoma due to a combination of their pressure and the health of their optic nerve and circulation. I give these at-risk patients the option of surgery to lower their intraocular pressure (IOP) to a safer level. Surgery, unfortunately, also entails risk, and it is after surgery that the majority of my patients who have lost vision do so.

P:  What are some of the reasons for losing vision after surgery?

Dr. Rick Wilson:  The most common reasons for serious post-operative vision loss is a hemorrhage between the layers of the eye from the rapid decrease in intraocular pressure (IOP) after surgery or from later bleb-related infections. Other patients do not see as well post-trabeculectomy due to too low an IOP or the development of a cataract. Those who lose vision from a hemorrhage, however, maintain their remaining vision for life, and those who developed cataract can be cured. Clearly, surgery saves the vision of exponentially more people than it harms.

The real bottom line is that the vast majority of vision lost to glaucoma in the U.S. occurs before patients see the doctor. If the doctor is aggressively trying to lower the IOP to an adequate target pressure and the patient is diligently following the treatment regimen, few people lose their vision while under medical therapy.

P:  If a patient has lost 90% of his or her vision, what are the chances the rest will be lost?

Dr. Rick Wilson:  That depends on how low one is able to get the IOP.  If the IOP is reduced to the under-12 mm Hg range, adjusting for thin corneas, I think the chances are quite good that the vision will be retained for life.  That means under 12 mm Hg at all times of the day. Surgery levels the IOP and laser significantly decreases IOP fluctuation.  Medications don't do as good a job as we would like in keeping IOP level.

P:  What is the adjustment unit for thin corneas?

Dr. Rick Wilson:  Our best present guess is 1 mm Hg for every 20 microns thinner than 545 microns.

P:  How often should a patient ask for a visual field test to help allay fears of rapidly losing vision?

Dr. Rick Wilson:  If field loss is mild to moderate and the IOPs seem controlled, then yearly.  If the IOP is above normal and the glaucoma is mild, then every 9 to 12 months.  If the loss is moderate to severe, then every 6 months.  I rarely get visual field tests more than every 6 months, unless the patient develops new symptoms that may be related to visual field loss.

P:  What are the vision requirements for driving a motor vehicle?

Dr. Rick Wilson:  State laws usually mandate 160 degrees of vision with both eyes open, and a vision of 20/50 in the better eye.

P:  How do you know when you have had a hemorrhage?  After my trabeculectomy, I had blurred vision and still do.  At first, the doctor thought that was caused by cataract, then he thought it was caused by glaucoma.  Could I have had a hemorrhage, and would that cause loss of vision right away?

Dr. Rick Wilson:  A hemorrhage into the vitreous gel in the eye or in the retina would cause an immediate decrease of vision.

P:  Do you find that time helps patients' fear subside?  Getting used to the idea (and finally accepting) that this is a life-long battle has helped me deal with the medications and surgery.

Dr. Rick Wilson:  Yes. I think patients often go through denial, then anger (why me?), and bargaining, before acceptance.

P:  Maybe, in the words of Winston Churchill, we have nothing to fear but fear itself.

Dr. Rick Wilson:  I wish that were entirely true, but it sure is partly true.

P:  I think what Churchill said is right.  If we are losing our vision or are afraid of it, we should research visual aids and other services for the visually impaired.

Dr. Rick Wilson:  With the advances that are coming in surgery, gene therapy, and stem cell research, there is every reason to be optimistic over the long term.  Also, if you are losing visual field in spite of your doctors' best efforts, a second opinion often helps by suggesting other avenues to try and reassuring the patient about his or her care.

P:  What are the first signs of losing vision to glaucoma?  I seem to remember sensing sort of a generalized loss of contrast, sort of a grayness, less brightness.

Dr. Rick Wilson:  The dangerous aspect of glaucoma is that there are few symptoms.  Color vision (blue-yellow) can be lost early in a few people, loss of contrast sensitivity, like you noticed, is common.  That is, you see well with good light and excellent contrast (black on white), but much less well with decreased contrast (gray on gray).

P:  I think the list of the first signs of losing vision should include starting to trip and fall, being unable to judge distances, and things starting to jump out at you.

Dr. Rick Wilson:  Unfortunately, those are late signs of serious visual field disturbance.

P:   Her husband recently got his guide dog, so she knows something about losing vision from his experience.

Dr. Rick Wilson:  I agree. Having had Labradors for years, it always amazes me when a seeing eye dog comes in and is incredibly well behaved.

P:  What are some examples of low vision aids besides seeing-eye dogs?

Dr. Rick Wilson:  Strong, directed reading lights such as goose-neck pharmacy lights.

Magnifying lenses.  Video viewers that magnify hugely.

P:  What services does a low-vision department offer?

Dr. Rick Wilson:  Low-vision refraction, to see if telescopic and magnifying lenses can help, plus a full range of low-vision aids. Some even offer mobility training and activities-of-daily-living help for the more seriously impaired.

P:  Couldn't IOP that is under control fluctuate four points?  Does that amount of fluctuation necessarily mean you will lose more vision?  I'm at the target pressure after trabeculectomies, but my IOP still fluctuates 3 to 4 mm Hg.

Dr. Rick Wilson:  Normals have an IOP fluctuation of 3 to 4 mm Hg.  If your nerve is healthy, that amount of fluctuation should be okay.  If you have serious disease, the absolute level of the highest IOP is probably the main determinant, although fluctuation may be a risk factor in its own right.

P:  I have a cataract in my right eye.  A specialist thought my 20/50 vision was partially due to glaucoma.  After a second OCT (ocular coherence tomography), which had better readings than the first, I wonder if maybe it was just due to cataract.  How accurate is OCT?

Dr. Rick Wilson:  That depends upon what generation of OCT was used.  At this point, OCT is better suited to retinal disease than to glaucoma, but it's getting better.  I can't wait till the next generation comes out.  I have seen pictures from the prototypes, and they are impressive.

P:  How does OCT work?

Dr. Rick Wilson:  OCT is a device that uses the characteristics of light to measure the thickness of the retinal nerve fiber layer around the optic nerve.  Since glaucoma kills these nerve fibers, the retina in glaucoma patients is thinner than it should be.

P:  I have trouble with the vision in one eye.  It's a blurriness that's not reflected in my visual field tests, in my acuity, or in other common optometric tests.  My weaker (acuity) eye has become totally dominant.  Should I look to my optometrist, more than my ophthalmologist, for help with this?

Dr. Rick Wilson:  I would think the ophthalmologist should have a better chance to explain it, and the optometrist may be better at finding glasses to help.

P:  Why would I have light sensitivity on sunny days even with sunglasses?  My mom had the same problem when she lost her sight.

Dr. Rick Wilson:  Anything that irritates your corneas, from dry eyes to a toxic reaction to glaucoma medicines and preservatives, can cause light sensitivity.  Intraocular inflammation and previous surgery, especially if the iris is affected, also can result in light sensitivity.

P:  If there is no usable vision and cataracts develop, is there any point in removing the cataracts?

Dr. Rick Wilson:  No, is the answer to your question, but clearly there are shades of gray for someone with a little vision and white cataracts.

P:  Even though my husband has no sight, he still has headaches all the time.  He feels that his eyes are causing the headaches.  Do you have any suggestions or explanations?

Dr. Rick Wilson:  If his IOPs are elevated or if he has inflammation in the eye or fluid gathered between the layers of the eye that has a nerve on stretch, there could easily be symptoms from the eye. Or the cornea could have serious irritation.

P:  What does "a nerve on stretch" mean?

Dr. Rick Wilson:  That means a nerve bridging two layers of the eye that should be in close apposition, but now are being pushed apart by fluid, can "stretch" a nerve, causing serious pain.

P:  What surgical advances or new meds are in the pipeline?  Can we hope that stem cell work will yield any results in the near future?

Dr. Rick Wilson:  There are multiple approaches to surgery on Schlemm's canal, the drain in the eye.  These approaches offer less invasive IOP control, without the formation of a bleb that can leak and get infected.  The surgery, however, may only be for those who can get by with an IOP over 15 mm Hg.  No new blockbuster meds are close at the moment.  Several other combination drugs are being tried.  Stem cell advances are 10 to 15 years off, depending upon whom you talk to.

Moderator:  Thanks so much, Dr. Rick Wilson.  You've been terrific as usual.  Have a great week.

Dr. Rick Wilson:  You're welcome.  Good night all.

On June 29, Dr. Wilson discussed "Blue-on-Yellow Visual Field Testing" in the Chat room. Click here for highlights of that meeting.

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