Ocular Hypertension
Chat Highlights
April 3, 2002

Norma Devine, Editor

On Wednesday, April 3, 2002, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Ocular Hypertension."

Moderator:  Welcome,  Dr. Rick.  The topic tonight is "Ocular Hypertension."  Is a patient with ocular hypertension (OHT) a glaucoma suspect?

Dr. Rick Wilson:  Yes. We don't like the term ocular hypertension, because it suggests there may not be anything wrong.  We prefer the term "glaucoma suspect" on the basis of elevated IOP (intraocular pressure), disc appearance, visual field, or family history. 

P:  Calling people glaucoma suspects makes me think they need police surveillance.  It would probably be more instructional to call elevated IOP ocular hypertension, which would be less scary for the patients.  

Moderator:  But if the person takes the diagnosis less less seriously, then maybe he or she will not follow up.

P:  I agree.  It would seem to promote the "denial stage" more.

Dr. Rick Wilson:  That's the point I was trying to make, but you made it better.

P:  Serious and scary are two different things!

Moderator:  What IOP is considered hypertensive?

Dr. Rick Wilson:  Usually, an IOP over 22 mm Hg if over 60 years of age, and over 18 mm Hg if a child.  

P:  What does "ocular hypertension" mean?

Dr. Rick Wilson:  Ocular means "eye."  "Hyper" means increased tension.  "Tension" means pressure in the eye.  In other words, ocular hypertension means a higher pressure than would normally be expected.

P:  What is the difference between ocular hypertension and glaucoma? 

Dr. Rick Wilson:  In ocular hypertension , the IOP is above normal, but no damage to the optic nerve (the hallmark of glaucoma) has yet been detected.  Remember that the optic nerve has to be 35% to 45% damaged before damage shows on a visual field test.  However, direct observation of the nerve can reveal changes when as little as approximately 10% to 15% of it has been damaged. 

Moderator:  If a patient has OHT and narrow angles, should that patient have an iridotomy to prevent attacks of acute-angle closure?

Dr. Rick Wilson:  Yes.  If the angle is judged occludable (that is, the iris can get caught in the drain of the eye), an iridectomy should be performed. 

P:  When is the pressure considered high enough for surgery?

Dr. Rick Wilson:  There is no pressure that always justifies surgery, except maybe over 30 mm Hg.  Each patient has an individual pressure level that will do damage to his or her optic nerve.

P:  Why does the pressure change throughout the day?  

Dr. Rick Wilson:  People make more fluid in the eye at some times more than at others on a daily cycle, related to hormones. If the drain (trabecular meshwork) in the eye is partially clogged with debris, the pressure of the patient with glaucoma will fluctuate much more than normal.  Normal is about 4 mm Hg.  People with glaucoma fluctuate about 11 mm Hg.

P:  Does stress increase IOP?

Dr. Rick Wilson:  All my patients feel stress elevates their pressure, but that is subjective and hard to prove. 

P:  Is a patient who has been treated for high IOPs that have been controlled with surgery and eye drops considered to have OHT?  

Dr. Rick Wilson:  No.  That person would be considered as having glaucoma.

P:  Does the IOP of females fluctuate more than the IOP of males?  

Dr. Rick Wilson:  Yes, slightly.  Women's anterior segments are smaller and more prone to angle-closure attacks.  Women's pressures are also more likely to rise more as they age.  Because hormones associated with pregnancy increase the outflow of fluid, IOPs drop during pregnancy. 

P:  Are the hormones associated with pregnancy used in eye drops to increase fluid outflow?

Dr. Rick Wilson:  No, but that is a thought.  Recent evidence suggests that hormone replacement may actually make dry eyes slightly worse, though it might make the IOP better.

P:  Would exercise help? 

Dr. Rick Wilson:  Exercise helps. 

P:  Does IOP increase when the eye is being used for close-up work?  

Dr. Rick Wilson:  When the eye focuses on something nearby, the muscle that controls focusing also pulls open the drain more, lowering IOP.

P:  Why hasn't there been more research into regulating diurnal variation with hormones (for example, melatonin?)
(Editor's note: Melatonin is an N-methyl-D-aspartate (NMDA) receptor antagonist.)

Dr. Rick Wilson:  The hormone that I remember being most linked to IOP fluctuation is serum cortisol.  That hormone has many effects all over the body.  Reducing the amount of circulating cortisol would be very detrimental to health.

P:  Is IOP affected by seasonal changes?   

Dr. Rick Wilson:  IOP varies with the season, and is higher in winter.

P:  What follow-up care do you recommend for someone who has just been diagnosed with OHT? 

Dr. Rick Wilson:  That person will need to have a photo of his or her optic nerve (maybe computerized imaging), visual field tests, and should be followed every 6 to 12 months, depending upon the amount of concern.  Remember that the visual field test detects glaucoma first only 15% of the time.  The appearance of the optic nerve should usually determine whether you have glaucoma damage yet or not.  It takes an experienced observer to recognize glaucoma early.

P:  When do you expect to get the results of the Ocular Hypertension Treatment Study (OHTS) to set some standards about whether, or when, to treat OHT?

Dr. Rick Wilson:  Glaucoma is such a long-term disease that I think the most pertinent information may be some time away yet.

P:  If focusing on something nearby lowers IOP, wouldn't eye exercises help to lower pressure?  Also, I thought reading and working at a computer might strain the eyes, but maybe it's actually good for them.  

Dr. Rick Wilson:  Yes, close work lowers IOP.  Eye exercises do not seem to lower IOP except when you are doing them.

P:  The pressure in my eyes was 26 mm Hg yesterday. What does that really mean?

Dr. Rick Wilson:  It means your IOP is 4 mm Hg above the top of the "normal" range of IOP. 

P:  What is the high end of the normal range of IOP?  Is it 18 mm Hg?  

Dr. Rick Wilson:  It's 22 mm Hg.  

P:  My biggest hang-up dealing with OHT is that the pressure is the only risk factor that can be manipulated.  I have OHT, but must wait until glaucoma starts to begin treatment.  It seems a little backward.  It seems you would want to start treatment to prevent it.

P:  But if tolerance of glaucoma medications or resistance to them builds up, why start using medications before damage occurs?  

Dr. Rick Wilson:  If you have two or more risk factors and elevated IOP, I wouldn't wait for damage to occur before starting a very benign medication.  On the other hand, our aim in glaucoma is to keep patients without symptoms for their entire life, not to prevent every little bit of visual field loss.  Some field loss seems to be very well tolerated even though the patients had no symptoms.

P:  Is it true that many people go for years with elevated pressures without suffering glaucomatous damage? 

Dr. Rick Wilson:  True.  That's why I said a person would have to have serious risk factors besides elevated IOP before I would start them on drops without definite damage to the optic nerve.  Such risk factors would be a family history of glaucoma, advanced age, black race, low systemic blood pressure, or vasospastic disease.

P:  I'm curious about my IOP of 26 mm Hg.  Since that's only 4 mm Hg above normal, wouldn't it be more prudent to wait before having a trabeculectomy?  Isn't there something I could try in the meantime to lower pressure?  I'm now taking timolol and pilocarpine twice a day.

Dr. Rick Wilson:  Have you tried five different classes of medication?  If you have and cannot take more than the two you are on, then laser or surgery would be the next step, if the IOP seems to be at a level that would damage your eyes. 

P:  Can optic nerve damage in a patient with elevated IOP be caused by something besides IOP?

Dr. Rick Wilson:  Yes, vasospasm or a spasm of the vessel going to the nerve or retina. Autoimmune disease seems to play a role in some patients. Low systemic blood pressure is another cause.

P:  My biggest concern is that I have amblyopia in one eye with some visual impairment already, but normal visual fields.  I may have the beginning of a cataract in that eye, too.  So waiting is rather frightening.  I know I am at low risk for developing glaucoma, but it concerns me that the loss of any sight in my good eye could be difficult to cope with.

Dr. Rick Wilson:  I understand and sympathize.

P:  Thanks.

Dr. Rick Wilson:  Sorry, gang.  Got to run.  Have a good week.

End of highlights for April 3, 2002.

On April 10, Dr. Wilson discussed "Treating Recalcitrant Glaucoma" in the Chat room. Click here for highlights of that meeting.

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