Wednesday
May112011

drusen...

with a resultant pigment epithelial detachment...

Tuesday
May032011

Spectral Domain OCT scan

using a 512 x 128 macular cube scan, the results of which are a normal macula. patient # 3547

 

Wednesday
Apr202011

Herpes Virus and the Eye

Herpes Simplex is a virus broken into 2 categories:  type 1 and type 2.  Easy enough.  Herpes outbreaks or "cycles" occur semi-randomly, but seem to coordinate with periods of other sickness or emotional stress.  The virus itself lives within the host indefinitely as there is no way to eradicate the virus completely, from a systemic standpoint.  So in the realm of eyecare, we treat the local outbreaks of the eye when they occur.  

If your eye doctor tells you you have "herpes of the eye," your official diagnosis is likely Herpes simplex epithelial keratitis.  There are around 48,000 new cases of this per year.  The "epithelium" referenced in the diagnosis is the outermost layer of the cornea (which is the 5 layered clear tissue on the front surface of the eye.)  So this can usually be considered a surface disease and is fairly easy to treat with a topical antiviral called trifluridine.  A newer drug that is now my 1st choice is Zirgan (ganciclovir).  The drug delivery system with Zirgan is superior, being in a gel form. 

Recurrence can be a troubling issue.  Sometimes the patient can have a more severe version of the disease where HSV infects the large central portion of the cornea called the stroma.  Longterm corneal problems such as scarring are more likely in these cases.  

There was a study done around 10 years ago called the Herpes Eye Disease Study that looked at ways to curb recurrence since there always exists the risk of corneal scarring with each subsequent outbreak.  Turns out a low dose oral anti-viral like Zovirax or Valtrex used as maintenance therapy sharply reduced number of outbreaks in the majority of patients.  If you are having bouts of recurrent HSK, definitely discuss this option with your Optometrist.  These low doses tend to be tolerated well with little side effects.  

Valacyclovir (Valtrex) makes a little more sense to me in this regard due to it being a pro drug.  Pro drugs rely on the body to do the metabolism into the more active form.  In effect, getting rid of the "Val" part, which is just an amino acid called Valine that they tack on to make the compound "less active" until the body converts it.  The advantage of this process is to enhance "bioavailability," thereby making the drug available for longer periods of time.  You can usually get by with less frequent dosings as well as lower drug concentration with the Pro form of drugs.  

If you fall into one of these categories of patients who have problems with recurrence rates, this is something to look at.  Most of the time, we can just treat a case of HSK (Herpes Simplex Keratitis)  with a topical antiviral for 2 to 3 weeks and the patient may not have another recurrence for several years.  This meets the standard of care for herpetic surface disease without having to go to an oral.  

Herpes Zoster infections are a different animal and tend to take a higher dosage of antivirals for longer periods.  It lives in the 1st branch of the 5th cranial nerve, or the ophthalmic division of the trigeminal.  

The epithelial disease is the most common and is generally easy to diagnose, though there can be much variation in its staining patterns, making an early diagnosis difficult.  Staining patterns are seen when your doctor puts the ophthalmic dye into your eyes and shines a cobalt blue light at you.  

There are even studies that suggest herpes simplex may have a role in Bell's Palsy (a partial facial paralysis, cranial nerve VII involvement).  

Questions or comments welcome.

Sunday
Apr102011

Entrepreneurs

Know anyone who has started their own business or just someone who has great ideas or dreams?  Is that person you?

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.