High Risk Patients
Chat Highlights
April 16, 2008

On Wednesday, April 16, 2008, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "High Risk Patients".

Moderator: Tonight's topic is “High Risk Patients.” Are we talking about “high risk suspects” or patients who are at high risk to have their glaucoma progress?

Dr. Pro:  We'll look at both over the course of the discussion.

The earliest data comes from observation. Centuries ago physicians noticed that elevated eye pressure could lead to blindness. The development of the ophthalmoscope in the 1850’s allowed examination of optic disc cupping from glaucoma. Modern scientific studies and papers have better defined risk factors. It has been known for over 30 years that disk hemorrhages are associated with glaucomatous progression. It has also been noted that family history of glaucoma in a first degree relative is a risk factor. But these earlier studies suffered from a lack of strong data.

We now have several landmark studies which are better defining risk factors: The Advanced Glaucoma Intervention Study (AGIS) was NIH sponsored. It enrolled 591 patients with advanced glaucoma who had failed medical treatment and needed glaucoma surgery. It randomized these patients to different treatment protocols. AGIS findings. Patients with IOP consistently lower than 18 over six years on average had minimal visual field progression.
[Note: Information about the AGIS can be found at the US government National Eye institute, part of the National Institutes of Health, http://www.nei.nih.gov/neitrials/static/study49.asp —ed.]

P:  What is a disk hemorrhage? Is it something a patient would be aware of?

Dr. Pro:  Good question. No, a disk hemorrhage is a spot of blood on the optic nerve as small as the period at the end of this sentence. It is found at examination when the doctor looks at your optic nerve.

P:  Is this (disk hemorrhage) an indication that the glaucoma is progressing, or simply a risk factor?

Dr. Pro:  Well, it can be both. In a person with ocular hypertension but no visual field loss a disc hemorrhage is associated with a greater risk of developing glaucoma. Similarly, in a person with glaucoma a disc hemorrhage is associated with a greater risk of getting worse. But it is not 100%; rather the risk is about 15% higher than without the hemorrhage. A disk hemorrhage can be due to other things, like a vitreous detachment.

P:  Does the course of treatment change if a patient determined to be high risk?

Dr. Pro:  Yes, I think many doctors treat these patients more aggressively. Certainly if I have a patient in my exam room and I know that one or both of her parents were blinded from glaucoma and she already has a degree of visual field loss I will be more aggressive in going for a lower treated IOP.

Other risk factors appear in some studies and not in others. They include myopia, diabetes, African or Latino ancestry, and hyper or hypotension. The Barbados Eye Study found that found that a perfusion pressure doubled the risk of developing glaucoma as were persons over 60 years old.

[Note: M. C. Leske, A. M. Connell, A. P. Schachat and L. Hyman, The Barbados Eye Study. Prevalence of open angle glaucoma, Archives of Ophthalmology, 994 Jun;112(6):821-9, was, at the time, the largest study of glaucoma in a black population, yielding a wealth of information. Studies from the Barbados Eye Studies Group continue to be published to this date, with a search of PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) on “Barbados Eye Studies” giving 34 results, the most recent in April of 2008 –ed.]

P:  What is perfusion pressure?

Dr. Pro:  Perfusion pressure is a function of intraocular pressure and blood pressure. So if the BP is low and the IOP is high then it is tougher to pump blood into the eye and the perfusion pressure is low.

P:  Do the patient's general health and other medical conditions make the patient high risk for suffering adverse effects of treatment and/or eye surgery?

Dr. Pro:  Yes, general poor health seems to affect surgical outcomes. The healing is different and these patients take longer to recover from any complications that might occur in glaucoma surgery.

P:  Dr. Pro, what if a person has a one-time intra ocular pressure (IOP) reading of 28 and 30 mm Hg? Does that constitute high risk, and is it sufficient to start a person on drops? Does it mean the patient has glaucoma?

Dr. Pro:  Good question. The fact that it was only a single reading does not matter; the important information is the status of the optic nerves and the visual fields. If the nerves look healthy and the visual fields are normal then the person may have ocular hypertension. This is like having high blood pressure. High BP is a risk factor for heart disease, but not everyone with hight BP has heart disease. So high IOP is a risk factor to develop glaucoma, but not everyone with high IOP has glaucoma.

P:  Is hypertension a risk factor for either glaucoma or ocular hypertension?

Dr. Pro:  Hypertension does not consistently show up as a risk factor in the good studies. In fact hypotension (low BP) may be a greater risk.

P:  Are there patients that are high risk for suffering side effects of glaucoma medications? If so, explain, please.

Dr. Pro:  Some patients can't take certain medications. For example, some asthmatics can't take beta-blocker drops because it worsens their breathing problems.

P:  Does previous eye surgery make subsequent eye surgery riskier?

Dr. Pro:  The risks of post-surgical failure are probably greater. Complicated previous intraocular surgery often makes further eye surgeries more difficult. With the increased difficulty comes greater chance of complications.

P:  I have heard it said that three glaucoma surgeries in one eye is the most that should be done - i.e. filtering or a shunt - is that correct?

Dr. Pro:  No, it all depends on the amount of scar tissue and the types of surgeries. Three shunts might be the limit, but one could possibly perform two trabeculectomies and follow those up with several shunts if needed (and if the person has useful vision to save).

P:  Thin corneas are a risk factor for glaucoma. How does corneal thickness effect the absorption of glaucoma eye drops? Can the corneal thickness be measured by Ocular Coherence Tomography (OCT)?

Dr. Pro:  Unless the cornea is swollen (edematous) then the corneal thickness does not affect drop absorption. The corneal thickness can be measured by different techniques. The standard OCT does not measure it, but I think an anterior segment OCT does.

P:  Does corneal thickness change with age?

Dr. Pro:  I don't think so, certainly not as an adult.

P:  Would you say that there are more problems with low IOP than with high IOP? Can one stay for years with out loss of vision on eye drops alone?

Dr. Pro:  In general the risk for developing glaucoma increases with increasing IOP (over 21). So, persons can certainly remain stable on drops alone.

P:  What would be the normal course of treatments - would you start with one medication over another - and if that stopped working what would your next step be?

Dr. Pro:  It depends on the situation. But if I have a patient with a higher IOP and early glaucoma. I usually discuss treatments. I might offer drops or a laser trabeculoplasty. Most of my patients in this category start a drop and right now most ophthalmologists or optometrists would begin with a prostaglandin analogue (like Xalatan, Travatan, Lumigan).

Moderator: Thank you for your time and for sharing your knowledge with the group, Dr. Pro. It is always a pleasure.

Dr. Pro:  You're welcome and until next time, goodnight all.

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