Hyperopic eyes tend to be shorter and smaller than the average eye, so everything is condensed in the eye, including the angle. Besides hyperopic patients, elderly patients who have not had cataract surgery are also at risk because as a cataract develops, it pushes the iris forward, narrowing the angle.
On the other hand, angle closure if it develops often leads to dramatic symptoms — an unbearable pressure like headache, blurry vision, nausea, vomiting, redness, extreme eye pain. Occasionally, patients with narrow angles suffer from intermittent episodes of angle closure attacks, and these are usually associated with a mild or moderate headache in dark light conditions, blurring of the vision for a few hours, redness, and sometimes nausea and vomiting.
There are several options for narrow angles, and your doctor will review which option is the best depending on the overall health of the eye. In general, treatment involves either laser surgery or cataract surgery. Laser surgery typically involves making an iridotomy, which is a small hole in the iris that causes the angle to become less acute, and to open further. Some require estimation or measurement of the degrees of angle opening, with an angle measuring 10 to 20 degrees defined as narrow.
The most common form of primary angle closure is thought to arise from pupillary block 11 in which aqueous forces the pupil forward. In this scenario, apposition of the lens and the posterior iris at the pupil leads to blockage of the aqueous flow from the posterior chamber to the anterior chamber. As the pressure in the posterior chamber increases, the peripheral and midperipheral iris is pushed forward, blocking trabecular meshwork drainage.
Another mechanism of primary angle closure is plateau iris in which the iris root is displaced anteriorly, creating a fold in the angle and displacing the peripheral iris into the trabecular meshwork. Secondary angle closure may arise from pathological enlargement and anterior displacement of the lens, pushing the iris forward to narrow the angles in phacomorphic glaucoma. Another contribution to recognize in the development of narrow or closed angles is the role of prescription and over-the-counter medications.
Many widely prescribed and readily available antidepressants and antihistamines can increase the risk of ACG by inducing iris dilation or anteriorly displace the lens-iris diaphragm. One medication to note is topiramate Topamax, Janssen , used in the treatment and management of epilepsy and migraines and more recently for weight loss, along with many off-label uses.
Topiramate can cause swelling of the ciliary body and lens, as well as uveitis, myopia, and bilateral angle closure. Related: The dangers of starting and stopping glaucoma treatment. Although it is difficult to be precise about the mechanism of narrow angle in all eyes, 15 it is important to recognize it may be the result of a combination of a number of factors. Gonioscopy is the standard for visualizing and diagnosing angle closure. It is important to evaluate all angles carefully.
If the most posterior structure visible is the posterior trabecular meshwork, the angle is described as narrow. If only the anterior trabecular meshwork is visible, the angle is typically open 10 degrees or less and is likely to close. If greater than degrees of the angle is found to be narrow, that patient is considered to be at risk for angle closure. When performing gonioscopy as an initial assessment, it is important to balance the pressure of the lens and not inadvertently perform indentation gonioscopy.
In that case, a narrow or closed angle may be mistakenly perceived as open. Additional factors when performing gonioscopy include the level of illumination, both in the exam room and the light entering the pupil from the slit lamp. In addition, using a small parallelepiped square to assess the inferior angle first will allow for a more accurate assessment. The lack of a fixation target will serve to reduce the role of accommodation in pupil constriction, although it may create some additional complications when the lens is first applied.
As mentioned, it is important to assess all angles because peripheral anterior synechiae may be more likely to develop earlier in the superior and temporal angles due to anatomical structure. Angle OCT and ultrasound biomicroscopy are useful adjunct imaging tools but may not reveal important characteristics such as peripheral anterior synechiae and should not replace gonioscopic evaluation. Note that these adjunct tests do not yield information about the amount of pigment in the trabecular meshwork.
Angle OCT imaging is also helpful in monitoring angle position status post treatment as well as for patient education. In cases of identified acute angle closure, the first line of treatment is to reduce IOP in order to prevent glaucomatous optic neuropathy.
This may be accomplished by using fast-acting topical glaucoma medications such as beta blockers, alpha agonists, carbonic anhydrase inhibitors, and pilocarpine. With the exception of pilocarpine, these medications work to reduce the aqueous production quickly-pilocarpine constricts the pupil and helps widen the angle. It should be noted that if a secondary angle closure such as phacomorphic glaucoma is suspected, pilocarpine should not be used because it may narrow the angle further.
Pilocarpine may also worsen an angle closure due to uveal effusion because it facilitates vascular permeability. Prostaglandins may not be as effective in immediate IOP reduction but should be used if no alternative or additional medications are available. The medications may be instilled every 10 to 30 minutes and should be continued until the IOP has been reduced to under 30 mm Hg. As with any treatment, optometrists should be aware of systemic conditions and potential contraindications with these medications.
These include but are not limited to asthma, chronic obstructive pulmonary disease COPD , kidney disease, and allergies. Related: Medically managing glaucoma. In urgent or nonresponsive IOP, systemic carbonic anhydrase inhibitors two mg tablets po in one dose may be given but are contraindicated in secondary angle closure induced by topiramate. Indentation gonioscopy may also be performed with a smaller lens such as a four-mirror lens. Applying pressure to the central cornea may drive the iris posteriorly, allowing the angle to open.
Once the IOP is controlled, the next step is to reverse the mechanism of angle closure. Laser peripheral iridotomy PI has been the definitive treatment for ACG due to pupillary block as well as a preventative treatment in narrow angle suspects.
A PI establishes an alternative route for aqueous flow between the anterior and posterior chambers and allows for the iris to return to a neutral position.
This is thought to be the result of prolonged irido-trabecular contact, resulting in long-term damage to the trabecular meshwork. Most patients who undergo PI will require additional intervention for either IOP lowering or improvement of visual acuity.
Even though PI is a minimally invasive procedure, complications may develop as a result, although unlikely. The causes for the change in the position of the iris that create Narrow Angle Glaucoma include blockage of the pupillary channel, iris plateau, farsightedness, and possible tumors surrounding the iris.
These issues are eye conditions that a leading eye care specialist will know to watch out for. This is why it is critical to get regular eye exams and schedule a checkup with an ophthalmologist when symptoms of eye conditions like Narrow Angle Glaucoma arise. Treatment for Narrow Angle Glaucoma involves reducing pressure, which can be done by oral or intravenous medication. Eye drops for glaucoma can also be helpful. Sometimes, laser and non laser glaucoma surgery may be necessary to decrease the intraocular pressure.
Whether you believe you are suffering from an episode of Narrow Angle Glaucoma or another eye condition that requires proper diagnosis and monitoring or treatment, Fort Lauderdale Eye Institute is the best eye care facility to turn to.
With professionals who have decades of experience as eye care specialists, you can find relief and solace when being cared for. Book your appointment with an ophthalmologist today at Fort Lauderdale Eye Institute.
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