Glaucoma Screenings
Chat Highlights
December 5, 2007

On Wednesday, December 5, 2007, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Glaucoma Screenings".

Moderator:  Welcome, Dr. Pro. Tonight our topic concerns glaucoma screening.  Let's begin.

P:  Who should be screened for glaucoma?

Dr. Pro:   Well, the quick answer is to screen individuals at risk.  That has been discussed in earlier chats.  The big risk factors, however, are a positive family history of glaucoma, being elderly, having thin corneas, elevated intraocular pressure (IOP) and myopia.

Moderator:  Even without those risk factors, shouldn't everyone be screened, starting at a certain age?

Dr. Pro:  Well, everyone should be receiving routine eye care from an ophthalmologist or optometrist.  The American Academy of Ophthalmology has certain guidelines regarding care.  Basically, everyone over age 40 should have yearly or bi-yearly examinations. Those with certain diseases, such as diabetes, should have more frequent examinations.

(Editor's Note: At this time, Dr. Rick Wilson relieved Dr. Michael Pro.)

Moderator:  Dr. Rick, what does glaucoma screening include?

Dr. Rick Wilson:    The screening includes not only checking the IOP, but also a good, usually dilated, examination of the optic nerve.  A visual field test, if there is anything suspicious, makes the examination more reliable.

P:  Is there a difference between a glaucoma screening at a health fair and screening as part of an annual or biannual eye examination by an eye doctor?

Dr. Rick Wilson:  That depends.  Often, a glaucoma screening at a health fair may be just an intraocular pressure check by allied health personnel.  If so, the screening will miss the 50% of patients who have glaucoma with an IOP of less than 23 mm Hg on their first eye examination.

P:  Who does the screening?

Dr. Rick Wilson:  The screening should be done by an ophthalmologist (Eye MD) or an optometrist. If the situation is border line, an MD should make the final decision.

P:  Are tonopens usually used at health fairs and public screening for glaucoma?

Dr. Rick Wilson:  Often they are, because they are easier to use than Goldmann applanation tonometers.  Tonopens, however, are less accurate than the Goldmann.  Occasionally, tonopens may be highly inaccurate without providing any warning.

P:  What happens if a patient's IOP is found to be high during a glaucoma screening at a health fair or similar event?

Dr. Rick Wilson:  The patient is then referred to a doctor for a more thorough examination.

P:  Do most of the people who are found to be glaucoma suspects at a free screening actually follow up with a full eye examination?

Dr. Rick Wilson:  Unfortunately, many people, when told they are glaucoma suspects, don't follow up or may not follow up for several years, till serious damage occurs.

P:  My optometrist phoned me a week after a screening to make sure I came in for a visual field test.

P:  How accurate are air puff tests?

Dr. Rick Wilson:  The air puff tests are rarely used any more, because they are not as accurate as the tonopen, which is not as accurate as the Goldmann.

P:  Do optometrists check carefully for early signs of glaucoma, and do they refer potential glaucoma patients to glaucoma specialists?

Dr. Rick Wilson:  Unfortunately, the quality of eye exams by optometrists, or even ophthalmologists, is quite variable, especially in a screening setting.  A study in Sweden showed that when all the people in a small town were given a thorough eye examination, many of those diagnosed with glaucoma had had an eye examination within the previous one to two years.

P:  As a mother diagnosed with closed-angle glaucoma and ICE (iridicorneal syndrome) in my mid to late 30's, when should I begin to have my children tested for glaucoma?

Dr. Rick Wilson:  Close to birth, all children's eyes should be examined by a pediatrician using a penlight. If the child's vision is normal, it should be checked again before pre-school.  Then I would advise examinations every three to five years until age 20, and every two years thereafter.

P:  Wouldn't it be better to use a tonopen to monitor for spikes in IOP than to rely on a Goldmann test every month? Why use the tonopen if it is not reliable?

Dr. Rick Wilson:  Most of the time, a tonopen is within a couple of mm Hg of a Goldmann, but now and then it is much further off.  I would feel uncomfortable making decisions on the basis of a tonopen measurement alone.  Following diurnal fluctuation of IOP with a calibrated tonopen is better than an occasional office visit during which the IOP is measured just once during the day.

P:  What is "border line" IOP?

Dr. Rick Wilson:  It must be remembered that normal IOP is different for different people. In older people, especially Hispanics of Mexican descent, at least one out of six people with glaucoma never evidence an IOP greater than 22 mm Hg.  With this proviso, most doctors feel 20 to 24 mm Hg is border line. But glaucoma patients with normal IOPs are the reason that an optic nerve exam (and, if any questions, a visual field exam) is crucial to detect glaucoma.

P:  Is glaucoma screening reimbursable under the U.S. Medicare Program?

Dr. Rick Wilson:  On January 1, 2002, an annual eye screening exam for African-Americans, age 50 and older, people with a family history of glaucoma, and diabetics became reimbursable under Medicare.

P:  Does Wills Glaucoma Service offer free glaucoma screenings?

Dr. Rick Wilson:  Twice a year, Wills has free screenings for all major eye diseases.  It is important to detect glaucoma early and prevent glaucoma damage because, compared with control subjects, patients with glaucoma were over three times more likely to have fallen down in the previous year, over six times more likely to have been involved in one or more motor vehicle collisions in the previous five years, and more likely to have been at fault.  One-third of elderly people who fall and break a hip die within year, and a third are barely mobile.  Clearly, the risk of falling is serious.

P:  What can you tell us about World Glaucoma Day, March 6, 2008?  Will doctors at the Wills Eye Institute be participating in some way?

Dr. Rick Wilson:  March 6 will be in the middle of the American Glaucoma Society (AGS) meeting in Washington, D.C.  We will be going to visit our legislators to try to restore funding for glaucoma research, explain the nature of the disease, and why it needs to be caught early.

P:  Do you think that glaucoma should be diagnosed on the basis of an IOP reading of 28 mm Hg and 25 mm Hg?  I am 82-years old and have poor co-ordination of my hands, so my visual field test results were poor.

Dr. Rick Wilson:  I think several IOPs should be obtained, unless there is optic nerve damage on examination.  A thorough, skilled examination of the optic nerve is better than a visual field test at detecting early glaucoma.

P:  Which parameters are most powerful for diagnosing glaucoma in a new patient, as opposed to tracking changes over time in the same patient?

Dr. Rick Wilson:  The most powerful parameters are the height of the IOP, fluctuation of IOP during the day, vertical cup-to-disc ratio, and a suspicious visual field.  If there are any definite changes in the optic nerve or visual field, then the person has glaucoma and is no longer a suspect.

P:  Although IOPs are an indicator of ocular hypertension, isn't visual inspection of the optic nerve more important?

Dr. Rick Wilson:  Yes, followed by visual fields, then IOP, since it is so variable and is often normal when first tested.

P:  My doctor says I have glaucoma.  Should my daughters be examined for glaucoma?  At age 82, I have difficulty taking a visual field test and would prefer that my doctor check my peripheral vision by using a manual hand test.  What do you think?

Dr. Rick Wilson:  Your offspring’s vision should definitely be checked yearly.  The visual field test uses small lights that are harder to see than a hand.  That is probably why you can see your hand to the side, but the field test shows damage there.  Remember that glaucoma takes a doughnut of vision around the center, with the far side vision usually left till the bitter end.  Vision nasal to center is a better test for vision loss.

P:  Would you find it surprising if five or six highly skilled eye doctors who were asked to evaluate a patient's optic nerve for damage did not agree on what they saw?

Dr. Rick Wilson:  No.  That is common in many glaucoma studies, and makes doing standardized and multicenter research that much more difficult.

Moderator:  Thank you, Dr. Rick.  Have a great holiday season.

Dr. Rick Wilson:  You're welcome.  I hope everyone has a wonderful, healthy holiday season.

On December 19, Dr. Pro discussed "The Optic Disk" in the Chat room. Click here for highlights of that meeting.

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