What is Hypotony?
Chat Highlights – March 20, 2013
Guest Speaker – Dr. Anand Mantravadi
Lorraine Miller, Editor, Chat Topic Researcher
Moderator: Glaucoma specialist, Dr. Anand Mantravadi, is joining us for tonight’s chat. Our topic for this evening is “What is Hypotony?”
P: Doctor, for the new chatters present this evening, would you please describe hypotony?
Dr. Mantravadi: Hypotony is defined as low eye pressure. Some definitions state 5 mmHg, but clinically, the eye can often withstand low pressures without a problem. In some eyes, structural changes can develop at a low pressure that can impact vision and visual function.
P: What intraocular pressure (IOP) is considered too low?
Dr. Mantravadi: There is no set number. If structural changes do not develop and the eye withstands a low pressure with good visual function, then the absolute number is generally irrelevant. Low single digit pressures can often result in issues.
P: How low does an IOP need to be to disturb vision?
Dr. Mantravadi: Someone may tolerate a pressure of 1 very well, and another person may have problems at a pressure of 6. There is no set number.
P: Is the length of time or the mmHg of pressure more important in causing long term problems from hypotony?
Dr. Mantravadi: Both are important. Transient low pressure that resolves quickly does not result in any major issues. Low pressure that persists can lead to structural problems.
P: What other clinically significant changes occur in the eye from hypotony?
Dr. Mantravadi: Corneal swelling, accelerated cataract formation, swelling in the retina, macular edema, and swelling in the choroidal layer or effusion can all develop.
P: What role does inflammation play in hypotony?
Dr. Mantravadi: Inflammation can reduce the amount of fluid made by the ciliary muscle, leading to a lower pressure.
P: To what extent can glaucoma eye drops decrease pressure? Can they cause hypotony?
Dr. Mantravadi: Medicines are highly unlikely to cause hypotony. They do not lower pressure lower beneath pressure of the veins of the eye which is 8-9mmHg.
P: Are there medications that can be used to eliminate hypotony?
Dr. Mantravadi: Steroids can decrease inflammation and increase aqueous humor production by the ciliary muscle. A clear substance called viscoelastic used during eye surgery can be instilled into the eye to temporarily raise the eye pressure to allow the body to recuperate.
P: Are retina wrinkles, macular edema or macular wrinkles caused by hypotony?
Dr. Mantravadi: All conditions are due to hypotony.
P: Is a wrinkled macula always a permanent result of hypotony?
Dr. Mantravadi: No, a wrinkled retina or retinal folds can result from other things as well. The condition may not be permanent. It can resolve itself depending on the cause.
P: Are either hypotony or high intraocular pressure following surgery predictable prior to surgery?
Dr. Mantravadi: Nothing can be predicted with certainty. Sometimes, given a specific problem, one can establish a likelihood that this will occur.
P: Does hypotony always cause vision loss?
Dr. Mantravadi: No, it does not always cause vision loss.
P: How long does a pressure need to be low in order to cause a rapidly growing cataract?
Dr. Mantravadi: There is no set time because there are no real rules with hypotony. Some patients may tolerate a low pressure and not have any major consequences. Others, if they are predisposed to this problem, can develop problems faster. Cataracts can develop very slowly or they can develop very quickly. In eyes with hypotony, one may expect more accelerated cataract formation, but in no set length of time.
P: After a trabeculectomy, is the only reason a cataract would quickly grow be due to hypotony?
Dr. Mantravadi: No. Some theorize that there is a tendency to develop cataracts at a faster rate than if surgery was not performed regardless of hypotony. This was an observation in the Collaborative Initial Glaucoma Treatment Study (CIGTS).
P: Can a patient self-diagnosis their hypotony?
Dr. Mantravadi: They may experience blurred vision. Some may feel their eye is soft but I would discourage people from testing it themselves.
P: Is continued blurriness and eye pain after a trabeculectomy and continued blurriness and eye pain after a bleb revision a sign of hypotony, and if so, what can be done?
Dr. Mantravadi: I am not sure I have enough detail and would discuss individual situations with your treating physician.
P: Are continued blurriness and eye pain common after a trabeculectomy?
Dr. Mantravadi: No, your physician may recommend certain medications to guide you to heal the right way.
P: Is there anything that can be done to raise the pressure without resorting to medication?
Dr. Mantravadi: It depends on the cause for low pressure. If it is surgically lowered pressure that would occur as a result of glaucoma surgery often Mother Nature and your body’s natural healing response will result in eventual higher pressures. It is not uncommon after all glaucoma surgeries to have temporarily low pressures and even some issues related to hypotony in the short-term recovery period.
P: Can chiropractic manipulation help with eye pressures?
Dr. Mantravadi: Not that I’m aware.
P: For a year and a half since being diagnosed with glaucoma, I have been using Latanaprost and Timolol once a day. My heart beat is now slow and my energy level is zero and I am starting to feel like I am going into an anxiety state. What should I do for it? I am getting terrified of this being a side effect. What choice do we have when it comes to saving our eyesight?
Dr. Mantravadi: I would advise you to discuss this with your doctor.
P: Is it common to have this side effect using Latanaprost and Timolol?
Dr. Mantravadi: Timolol can cause slowed heart rates in some individuals.
P: Do many patients have side effects from the medications prescribed?
Dr. Mantravadi: Side effects are a possibility with any medication. Some get them, many do not. It is important to avoid certain medications if people have certain conditions in order to avoid common side effects.
P: Can you explain the difference between anesthetic and viscoelastic gels and when each is added to the eye?
Dr. Mantravadi: A gel is anything with greater viscosity. There are gels for dry eye. There is an anesthetic gel to place on the eye for topical anesthesia. There is a “gel-like” substance called viscoelastic used in eye surgery to reform parts of the eye and temporarily raise eye pressure in special circumstances.
P: Why do some patients need a stitch added after a trabeculectomy?
Dr. Mantravadi: If your physician feels there is too much fluid flowing out of the drain and the body is unlikely to sufficiently scar, an additional stitch maybe added.
P: How does this stitch differ from those used during surgery?
Dr. Mantravadi: There is no difference. They are just additional reinforcement.
P: Are these stitches later removed?
Dr. Mantravadi: If the rate of fluid flow is adequate, stitches to the drain flap are left in place. They are removed to increase the rate of fluid flow at the surgically-created drain.
P: Can these stitches be felt by the person?
Dr. Mantravadi: Stitches are not usually felt by the patient.
P: How is the eye immobilized when additional stitches are required?
Dr. Mantravadi: It is not immobilized since topical anesthesia is usually sufficient. A suture can be placed to keep the eye from moving excessively.
P: What type of time period do you have in removing the stitches before they become permanent?
Dr. Mantravadi: They are always permanent. Stitches can be cut within the first one to two months to lower pressure. The earlier they are cut, the more impact it has in terms of increasing the flow at the surgical drain.
P: Immediately following surgery, how does an eye acquire a tear or hole in the bleb?
Dr. Mantravadi: Fluid will often direct to the point of least resistance. If the tissue is very thin, weak, or a small gap exists, the fluid can divert to that area. Mother Nature and scarring usually seals the tear or hole but sometimes, it must be surgically sealed.
P: Doctor, is there new updated information about life expectancy rates of tube shunts? I have had mine for 16 years. Whenever I ask this question, people respond by saying that there is no known life expectancy. It could be a few years or the rest of my life! Are there any new updates?
Dr. Mantravadi: No new updates to report.
Moderator: Our chat time is over for tonight. Thank you everyone for coming and thank you, Dr. Mantravadi, for your time!