Prostaglandins analogues like Latanoprost, Travoprost and Bimatoprost work by increasing the aqueous humor outflow at the uveoscleral area. They reduce the intraocular pressure by 25% to 35%. They should be administer once a day during the bed time. Side effects of these medications include conjunctival hyperemia, blurred vision, eyelash growth, red eye and irreversible discoloration of the iris more evident in the users of Latanoprost.
As a special consideration, Travoprost is contraindicated in pregnant patients. Alpha adrenergic agonist Such as Apraclonidine and Brimonidine work through the gonist effect at the alpha-2 receptors, decreasing the release of norepinephrine which in turn is required for the activation of beta receptors at the ciliary epithelium. By decreasing the activation, this medications reduce the formation of aqueous humor and lower the intraocular pressure.
Additionally, this drugs also increase the outflow at the uveoscleral pathway. The side effects of the alpha adrenergic agonists include, allergic reactions, red eye, ocular hyperemia and somnolence. As a special consideration, Brimonidine has been associated with respiratory depression in children, therefore its use is ontraindicated in those younger than 2 years of age. Alpha adrenergic agonist are also contraindicated in patients taking Monoamine Oxidase Inhibitors (MAOI).
Cholinergic agonist Such as Pilocarpine and Carbachol work by stimulating the parasympathetic muscarinic receptors to increase the flow at the Schlemm’s canal and the trabecular meshwork area. By increasing the Humor aqueous flow they eventually decrease the intraocular pressure. Pilocarpine is considered the drug of choice for emergency situations that require a decrease in the intraocular pressure. The side effects include eye pain, blurred ision and a miotic response that may generate night blindness.
According to the Preferred Practice Pattern guidelines of the American Academy of ophthalmology. Prostaglandins are recognized as the first-line therapy for Open Angle Glaucoma (OAG) because they are the most effective at decreasing the intraocular pressure. Beta blockers are considered the second line of therapy, they are usually prescribed in cases were the prostaglandins fail to reduce the IOP or as an additional therapy, in cases were the pressure reduction with prostaglandins is not enough to achieve the desired levels of ntraocular pressure.
As a third-line of therapy, carbonic anhydrase inhibitors alone or in combination with alpha adrenergic agonist can be used. The health professional should always considered different factors when deciding the type of medication to be administered, cost, side effects, toxicity, adherence to therapy and efficacy in decreasing the intraocular pressure are some of the key elements that the professional should consider when deciding the type of treatment. If the medical treatment is not enough to reduce the intraocular pressure, surgical procedures can be considered.
Laser Trabeculoplasty (Figure 6) which consist of a beam of light aimed to the trabecular area to facilitate drainage is a procedure that can decrease the intraocular pressure and increase the aqueous outflow, it is safe and can be performed at the office. However, the effects of the procedure can decrease over time. Trabeculectomy with Mitomycin C or others antifibrotic agents can also be considered. (Figure 7). The procedure consist of creating a drainage pathway for the aqueous humor at the trabecular meshwork.
As the third step in the surgical procedures, glaucoma drainage implants can also be onsidered, however they are reserved for refractory cases. (Weinreb, 2014). Figure 6. Laser Trabeculoplasty. Figure 6. Laser Trabeculoplasty aimed to the trabecular meshwork. Adapted from The Glaucoma Institute of Northern New Jersey. Figure 7. Trabeculectomy. Figure 7. Trabeculectomy. Graph that shows the creation of a drainage pathway. Adapted from Armadale eye Clinic. Closed Angle Glaucoma The main characteristic of the closed angle glaucoma is the complete obstruction of the drainage pathway with the subsequent closure of the anatomical angle.
Some of the main isk factors associated with it include changes in the anatomical size of the different eye components. An anterior chamber of the eye either too small or completely crowded, an iris too thick and a short axis of the anterior chamber are some of the anatomical factors associated with the presence of a closed- angle glaucoma. At the moment, the diagnosis is made through the use of more sophisticated and objective tests that allow the identification of the closed angle such as the ultrasound biomicroscopy.
The management of such patients depends on the severity of the process. The initial step include the laser peripheral iridotomy, a procedure in which a hole is created in the iris to establish a communication with the Schlemm’s canal, the maneuver can be generally performed at the office without major adverse effects. However, some side effects include rare cases of synechiae (adhesions of the iris to the lens) or increased intraocular pressure, therefore it is of utmost importance to follow up the patient.
Follow up and Nursing Implications As part of the initial evaluation in patients who have not been diagnosed with glaucoma, the health professional should onsider a good clinical assessment with emphasis on those with a family history of glaucoma, older people, African Americans or Hispanics. Depending on where the professional practice and the resources available at the site, the physical exam should include in addition to measuring the intraocular pressure, a method to evaluate the optic nerve and retinal ganglion cells, fundoscopy whenever possible and assessment of visual fields.
Any suspicious lesions found during a routine visit will ensure that the health professional refer such patients to the specialist, who will perform a much deeper evaluation of he case. In those cases where a prior diagnosis of glaucoma has already been stablished, the approach is different. During the follow up evaluation the professional should ask questions related to the presence of side effects, adherence to prescribed treatments, cost of drugs, problems with treatment and prescribed medications.
The professional should also document the results of the diagnostic tests recommended by the specialist and perform a good physical exam. The physical examination should include three essential elements as mentioned before. The assessment of the optic nerve and the etinal ganglion cells appearance as the initial step to the evaluation of any pathological damage to the eye, should be done according to the American Academy of ophthalmology with the help of a slit-lamp biomicroscopy, a type of magnified stereoscopic visualization technique. (Figure 8). Figure 8. Slit Lamp Biomicroscopy.
Figure 8. Slit Biomicroscopy of a patient with chronic uveitis and glaucoma showing the presence of a glaucoma valve implant. (a) Diffuse illumination. (b) Slit illumination. Adapted from The Indian Journal of Ophthalmology. The second element to onsider is related to the measurement of the intraocular pressure. Through the use of Goldmann Applanation Tonometry, the health professional must ensure that the intraocular pressure is at least 25% below the intraocular pressure recorded before the start of treatment, according to the Preferred Practice Pattern guidelines. Figure 9). Additional test that may be included in this phase include: Gonioscopy, to measure the angle of the anterior chamber. Fundoscopy, to see additional changes of the optic nerve and Thickness of the cornea, which helps assess the risk of increased intraocular ressure. Figure 9. Goldmann Applanation Tonometry. Figure 9. Goldmann Applanation Tonometry. The gold standard for measuring intraocular pressure. Adapted from Gem Clinic. The third element of the physical exam includes an evaluation of the visual field.
Assessment that according to the American Academy of Ophthalmology should be performed with the help of the Automated Static Threshold Perimetry technique. (Figure 10). Follow-up evaluation by the nurse or any health professional who is in charge of monitoring the patient diagnosed with glaucoma, should aim to relate the data btained during the physical assessment. By doing these, the professional can establish the level of damage of the Figure 10. Threshold Perimetry. Figure 10. Perimetry showing the visual field defect as a grey scale.
Adapted from Optometric Management. com optic nerve and the retinal ganglions cells, the progression or not of visual field defects and the levels of intraocular pressure. According to the Preferred Practice Pattern guidelines, if the pressure levels are ideal and there are no signs of damage to the optic nerve the patient should be seen every 6 months. Conversely, in cases here the target intraocular pressure is not achieved and there are signs of damage to the optic nerve, the patient should be seen every 2 months in average.
The professional has the responsibility to educate the patients on the appropriate management and the proper ways to administer the medications and drops. The provider must establish in conjunction with the patient a treatment plan to follow, Patients should also be educated about their condition, the signs and symptoms of it so that they can quickly inform the professional of any changes observed along the treatment, doing the necessary corrections. Glaucoma is considered the second cause of avoidable blindness worldwide after cataract.
According to the Glaucoma Research Foundation, In the United States more than 3 million suffer from glaucoma, of which only half know they have it. Additionally, more than 120,000 people suffer from blindness secondary to glaucoma. Therefore, it is a professional responsibility for those working in the health field to educate patients, to provide them with the best care possible, contribute with an early and timely diagnosis and help them to assume the responsibility of their condition.