LASER IRIDOTOMYOphthalmologist Carolina Valdivia, MD discusses laser iridotomy, a surgical procedure performed to help control primary angle-closure glaucoma.  A 60 year-old woman from the British Virgin Islands writes:Dear Dr. Valdivia, I was diagnosed with angle-closure glaucoma about six months ago. My doctor gave me a surgery called laser iridotomy in both eyes. A subsequent checkup proved that the holes were open and everything seemed all right. Last month I returned for another checkup and was told that the pressure in my eyes is too high – 30 in the right eye and 26 in the left. My doctor prescribed an eye drop called Cosopt and has recommended another surgery. I am not sure if this will be a second laser iridotomy or something else. My question is can I use eye drops instead of surgery to slow down the glaucoma? I ask because there seems to be no guarantee that even with surgery, I will not lose my eyesight. I have not returned yet to the doctor to see if the Cosopt eye drops have reduced the pressure in my eyes. Kind regards.
The fact that your ophthalmologist diagnosed you with
primary angle-closure glaucoma (PACG)
signifies that she or he has observed some degree of damage to your
optic nerve
and/or reduction in your
visual field.
This
type of glaucoma
is characterized by a constriction of the angle formed by the iris and cornea (iridocorneal angle), such that drainage of
aqueous humor
through a structure called the
trabecular meshwork
is impeded. Laser iridotomy is a surgical procedure that often is performed on PACG patients in order to prevent an episode of acute angle-closure glaucoma from occurring through something called a pupillary block. I am going to explain a little more about laser iridotomy, so that you can understand why it was necessary. Aqueous humor is produced in the posterior chamber of the eye in a structure called the ciliary body. This fluid normally circulates into the anterior chamber through the pupil. However, when narrow iridocorneal angles impede aqueous humor outflow through the trabecular meshwork, normal circulation becomes disrupted.
Ophthalmologists take a staged approach in the treatment of glaucoma. This means that we opt for the least invasive control measures first before proceeding to others. In your particular case, a laser iridotomy was an excellent treatment option, because you were at risk for the appearance of an acute episode of angle-closure glaucoma. Now your ophthalmologist must take steps to manage your persistent elevated intraocular pressure. An ophthalmologist selects medications to manage glaucoma depending upon the type of glaucoma and the level of increased intraocular pressure in the patient. For effective management, they may prescribe one, two or more different medications. In your case, Cosopt ophthalmic solution is a combination of two glaucoma medications: timolol maleate and dorzolamide. It was necessary to start with this dual therapy because your intraocular pressure remained high after surgery. Your ophthalmologist now will monitor your intraocular pressure closely to determine if the Cosopt is lowering it to an acceptable level. If Cosopt treatment has reduced your intraocular pressure, but not to a level at which you are protected against further damage to your optic nerve, then additional medications will be added to your regimen. It also is important to keep in mind that your ophthalmologist treats your eyes individually. A medication regimen that is effective in one eye, may not be sufficient to control intraocular pressure in the other eye.In most instances, medication is sufficient. However, if medication treatment proves inadequate in controlling intraocular pressure, then surgery is recommended. It is a mistake to judge your laser iridotomy procedure as unsuccessful based upon the fact that your intraocular pressure remained elevated following surgery. On the contrary, it has achieved its intended objective to prevent an episode of acute angle-closure glaucoma from occurring. If an additional surgical procedure is required, then it likely will be to facilitate the exit of aqueous humor from the eye, either through the trabecular meshwork or by creating a new drainage route. The goal of glaucoma surgery is to reduce intraocular pressure in patients where it is inadequately controlled with medication. However, it is important to understand that surgery is not a cure for glaucoma. Damage to the optic nerve is irreversible. At present, there is no cure for glaucoma. In most cases, glaucoma surgery is successful in lowering intraocular pressure, although it often is necessary to continue using medication therapy. However, surgery carries its own risks, which is why ophthalmologists only recommend it when other non-invasive treatments have had limited success. As you can see, there is not an easy answer to your question. Remember that treatment of glaucoma uses a staged approach. When it is determined that surgery is warranted, options for treatment by medication alone usually have been exhausted. Thus, glaucoma treatment is not as simple as a preference for one type of treatment over another type. I wish you well in the ongoing management of your glaucoma and achieving control of your intraocular pressure. Carolina Valdivia, MD
REFERENCE:Sharma T, Low S, and Foster PJ. The Classification of Primary Angle-Closure Glaucoma. In: Grehn F and Stamper R. Essentials in Ophthalmology: Glaucoma. Berlin: Springer-Verlag, 2009:41-48.
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This causes aqueous humor to accumulate and elevates
