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Saturday
Jan082011

Silent Thief of Sight

What a dramatic title.  But it's important to be aware of how glaucoma progresses, what to look out for, and how to prevent or arrest its progression.  I also needed a noteworthy title since glaucoma is the 2nd leading cause of blindness worldwide, behind only diabetic retinopathy, among adults. 

There are 2 generalized categories of glaucoma.  Simplified, this is open angle and closed angle.  POAG, or primary open angle glaucoma is painless and asymptomatic, hence the "silent thief of sight."  The only weapon we have against this disease are our local eye doctors.  Patients rely on these physicians to catch "suspicious" findings and order further testing.  There is just no way for a patient to know that there is a problem early on.  By the time the patient notices that something is wrong, a high percentage of the ganglion cell layer has died off.  Modern science does not yet have a great way to bring back nerve fibers in patients, so this nerve fiber "death" is irreversible. 

Therefore, efforts must be focussed on preventative care that can screen, monitor and watch for this predictable disease pattern.  Clinically, there are changes with the nerve fiber layer that occur.  We can see this on a dilated eye exam at the very place where the nerve fiber layer enters the eye:  cranial nerve #2, the optic nerve.  It is easiest to judge a ratio, or percentage at the point where the nerve enters to ascertain how much nerve fiber layer a patient has remaining. 

This has its own share of problems since differing physicians tend to estimate this ratio in different ways and inter-physician variability of what is called "c/d assessment" has been demonstrated to be quite high.  In this increasing environment of corporate eyecare, it makes the challenge even more daunting since many patients will doctor "hop."  Monitoring optic nerve head changes in this manner becomes impossible. 

Luckily, science has advanced for us in this realm with fantastic instruments for measuring these changes in the ganglion cell layer.  Every doctor will have an opinion on this based on his own bias, and most instruments will have merit in different ways.

The bottom line is for patients to find and select an eye doctor they like, whether he/she be in a corporate or private setting, and try to stick with them.  I find it best to get recommendations from friends who have doctors they have gotten to know over the years.  You also want someone who is willing to stay abreast of new technology and has invested in imaging equipment that is kept up to date, firmware and software-wise.  But a doctor you develop a relationship with is going to be better equipped to catch changes that could be sight threatening vs. a patient that hops around from doctor to doctor every year. 

The other type of glaucoma is called closed angle glaucoma.  That will be coming up in a future post.  It is usually easier to detect since the patient's sympoms can be acute and dramatic. 

 

 

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