Hi, my name is Shahzad Mian. I'm going to be speaking to you today about perioperative medications for cataract surgery. The goal with perioperative medications for cataract surgery, includes achieving adequate pupillary dilation. Achieving an anti-infective prophylaxis, anesthesia for surgery, and anti-inflammatory effects. In addition, it's also important to be aware of what medications the patient is already taking prior to surgery, as they may impact the outcomes and the surgical procedure. When it comes to pupillary dilation, the sympathomimetic drops we use tend to stimulate the dilator pupillae muscle. The most common medication used is 2.5% phenylephrine, which is an alpha-receptor agonist. It achieves its maximum dilation in 45 to 60 minutes, and the recovery time is approximately 3 hours. Topical use can cause systemic side effects, therefore, it is important to be aware of patient's cardiac history prior to using the drops. Additional sympathomimetic drops that can be used, include intraoperative use of Shugarcaine, which is a formulation that includes use of lidocaine and epinephrine, as well as a formulation that we use here in University of Michigan Kellogg Eye Center. These formulations allow for intraoperative pupillary dilation by stimulating the dilator pupillae muscle. In addition to using sympathomimetic agents, parasympatholytic agents, which are anticholinergic can also be used, they paralyses sphincter pupillae muscle as well a ciliary muscle. The common agents use, includes tropicamide, which in the 1% solution is used commonly prior to surgery, which has a peak mydriasis 20 to 30 minutes after use and recovery in 4 to 6 hours. Additional agents that may be used, includes cyclopentolate, homatropine, and atropine. It's important to note that the combination of sympathomimetic and parasympatholytic agents induces greater mydriasis. Anti-infective prophylaxis is used to address potential sources of microbes that lead to infection. And the potential sources, include flora of the conjunctiva, and the skin. Intraocular anterior chamber contaminants almost always are indigenous and these include, Staphylococci, Diphtheroids, Streptococcus, and Gram negative bacilli. The prophylaxis used is due to the need for decreasing or eliminating the bacterial load on the ocular surface. We want agents, which can penetrate into the aqueous to treat bacteria seeded at the time of surgery. And it is the community standard of care. The ideal antibiotic would have a broad spectrum of coverage, minimal side effects or toxicity, and a rapid kill rate. However there is limited evidence to show that pre-operative drops actually decrease risk of Endophthalmitis. We're going to review briefly what endophthalmitis is, because it's important to recognize this in terms of why we are trying to prevent it. Often patients present with pain, loss of vision, floaters, and light sensitivity. The most common signs of endophthalmitis, include lid swelling, vitreous inflammation, periorbital edema, ciliary injection, and a layering of white blood cells or a hypopyon. Most cases of endophthalmitis are culture positive, however about a third are culture negative. When they are culture positive bacteria account for the most common source of endophthalmitis, although rarely can be fungal as well. In the acute stage that is define as less than 2 weeks, the most common organism is coag (-) staph, followed by staph aureus, and streptococcus. In the subacute stage, which is defined by two to six weeks after surgery, coag (-) staph is the predominant organism. And chronic endophthamitis is after six weeks, is caused by propionbacterium acnes. Endophthamitis can also be caused by toxic materials and retained lens materials, therefore not being infectious. Prophylaxis of the endophthalmitis, includes treatment of blepharitis, since the most common organisms are present on the eyelids, by using warm compresses, lid hygiene, and oral doxycycline or azithromycin. Aseptic technique intraoperatively is very important with used of 5% povidone iodine because this is bactericidal, 10% may be used as well, however it may have greater endothelial toxicity. Preoperative use at the time of surgery has been shown to have a significant benefit in preventing a risk of endophthalmitis. Prophylactic broad-spectrum antibiotics are used including fluoroquinolones, which bind to bacterial topoisomerase, thus inhibiting bacterial DNA to supercoil. There are also bactericidal, and the fourth generation fluoroquinolones have lower have greater advantages of lower toxicity and superior penetration through the cornea. Therefore, providing higher minimum inhibitory concentrations into the aqueous. And our broad-spectrum in covering both gram positive and gram negative organisms. Many different regimens for preoperative antibiotics have been described in the literature, including one hour prior to surgery, three days prior to surgery, with different types of fluoroquinolones. And with postoperative use of different types of fluoroquinolones. However, when we examine the evidence, and in looking at the American Academy of Ophthalmology preferred practice patterns, they state that there is no clear evidence that any of these regimens actually decrease risk of endophthalmitis. Additional prophylaxis has been described in literature through the European Society of Cataract Refractive Surgery study of prophylaxis with intracameral of cefuroxime. This dosage involved using 1 milligram per point 1 mils at the time of surgery. In this study, there was a five-fold decrease in the rate of endophthalmitis in the treatment group as compared to the control group. Similar data has been reported with use of cefazolin used in intracamerally. In addition, prevention of endophthalmitis also involves modifying the surgical technique. There has been an associated increased risk of endophthalmitis with a transition from scleral tunnel incisions to scleral corneal incisions. And use of smaller incisions, as well as suturing incisions closed may decrease risk of endophthalmitis. Moving on to anesthetics for cataract surgery, we commonly use proparacaine eye drops, tetracaine eyedrops, lidocaine 2% jelly, or intracameral preservative free lidocaine. In addition, bupivicaine may be used as a peribulbar, or retrobulbar agent. Topical non-steroidals are used as an anti-inflammatory agent and their main mechanism of action is to inhibit cyclooxygenase activity by inhibiting prostaglandin formation in the arachidonic acid pathway. They're using cataract surgery to maintain adequate pupillary dilation. Control of inflammation after surgery, as well as prophylaxis and treatment of pseudophakic cystoid macular edema. Cystoid macular edema is the most frequent visual complication after uncomplicated cataract surgery. All of the incidents was much greater with earlier generations of cataract surgery techniques. It still remains relatively high when we look at uncomplicated cataract surgery risks, where patients who are symptomatic with vision less than 20/40, having a range of 1 to2%. There is greater evidence of cystoid macular edema when patients are examined angiographically or with additional testing including ERG, photostress test, and contrast sensitivity. The peak incidents of cystoid macular edema is 6 to 10 weeks postoperatively. Why does cystoid macular edema occur? Well, it starts to occur because there is increased perifoveolar capillary permeability, intraocular vascular instability, and increased production of prostaglandin that especially released from the anterior uvea. This results in cystoid spaces, and lacunar cavities in the outer plexiform layer of Henle. Because this is a thick layer, which is able to absorb large quantities of fluid. It is avascular, therefore there's limited capillary absorption of fluid. And there is a thin fovea and internal limiting membrane in this region, which increases susceptibility to inflammatory exudates and toxic products through the vitreous. What are the risk factors for cystoid macular edema? Well, there are a number of identified risk factors preoperatively, including having a epiretinal membrane, and noted prior to surgery. Hypertension, diabetes, history of uveitis or active uveitis, and having a history of cystoid macular edema including in the contrary lateral eye. Intraoperative risk factor, include types of surgery, as I mentioned earlier, earlier generation cataracts surgery techniques had a higher rate than newer generation cataracts surgery techniques. If there is increased vitreomacular traction, a prolonged case with ultraviolet light exposure, that's prolonged posterior capsular rupture, vitreous loss, especially if there's incarceration to the wound or adhesion to the iris. Even in iris prolapse can increase risk of cystoid macular edema after surgery. Types of lenses used can also increase the risk earlier generation lenses, which were iris-supported or closed-loop anterior chamber intraocular lenses have been reported to have a higher rate of cystoid macular edema after cataract surgery. Postoperative risk factors for cystoid macular edema, include medications, if patients are on epinephrine, dipivefrin, or even prostaglandin analogs, they may be at a higher risk for cystoid macular edema after surgery. Prolonged inflammation after surgery, as well as hypotony also increase the risk. Patients often present with decreased vision, they may have mild pain, redness, light sensitivity. We are looking for signs of complicated anterior segment surgery, mild anterior chamber reaction, loss of foveal reflex, yellowish reflex or spot in the macula, and perifoveal cystoid spaces with red-free light. A honeycomb lesion appearance, and perifoveal hemorrhages may also be present. In addition, capillary microaneurysms, and optic disc edema may also be noted. The goal standard for detection of cystoid macular edema is fluorescein angiography, where we can note a petaloid pattern with feathery margins, and signs of optic disc edema. However, now the most common method that's used is optical coherence tomography, which can easily detect cystoid spaces in the outer plexiform layer of henle. Topical non-steroidals that are used, include flurbiprofen, which is often used in the preoperative regimen to prevent interoperative miosis. Additional agent, include diclofenac, ketorolac, nevanac, and bromfenac. Topical non-steroids are contraindication if there is a known hypersensitivity a patient may have to non-steroidals. And a cross reactivity with any other non-steroidal. Bleeding may also be increased in patients, especially those who are on anticoagulation, or have a tendency to bleed more easily. Adverse reactions associated with non-steroidals, include sterile infiltrates, transient burning and stinging, and keratitis. So, topical non-steroidals maybe used preoperatively and postoperatively one to three days pre and postoperatively to reduce risk of cystoid macular edema. However, the role of preoperative non-steroidal to prevent clinically significant cystoid macular edema is still controversial. It is not clear from the literature that routine use versus using in high risk patients, or never routinely using non-steroidals, is the best treatment at this time. It is important to ask patients about what medications they're using, and which eye drops they are using prior to cataract surgery, because this can impact the intraoperative surgical treatment. Anticoagulation, antiplatelet medications may increased risk of medical and ophthalmic complications. However, it's low overall, and do not need to be routinely need to be stopped. You can stop use of anticoagulation if bulbar block's performed. However, that is also not required. Flomax, which is a alpha1-blocker, has been shown to cause complete and prolonged antagonism of the iris dilator muscles by affecting the iris smooth muscle tone. Other alpha1-adrenoreceptor blockers, such as terazosin and prazosin are non-selective, however, they also impact the muscle tone. Stopping these medications prior to surgery does not change the outcome during surgery. Additional herbs and vitamins can also have an impact on anticoagulation, and have antiplatelet effects. Their effect is not well-characterized, and there's no data to support whether there's a negative or beneficial impact during cataract surgery. Caution is necessary on patients on taking multiple herbs and vitamins, and this needs to be individually assessed with each patient prior to surgery. Topical prostaglandins can increase risk of pseudophakic cystoid macular edema by disrupting the blood-aqueous barrier. This is an important consideration in patients who have glaucoma who are undergoing cataract surgery, and may need to be stopped especially in patients who are at higher risk for macular edema after surgery. In summary, preoperative medications for cataract surgery, include those agents used for dilation, including phenylephrine 2.5% and tropicamide 1% because they have a synergistic affect. Non-steriodals, such as flubriprofen may be used at the time of surgery to improve dilation, and prevention of myosis. Topical anesthesia is performed often with proparacaine and lidocaine jelly, however, additional agents may be used for peribulbar and retrobulbar blocks. Antibiotics are not routinely recommended prior to cataract surgery because there is no known benefit of using it preoperatively. Intraoperatively, anesthesia is achieved with intracameral lidocaine. Dilation may further be enhance by using balanced salt solution with epinephrine, or using shugarcaine mixture of epinephrine. Anti-effective agents such as cefuroxime intraoperatively had been shown to reduce risk of endophthalmitis after cataract surgery. Postoperatively antibiotics maybe use, however the data for this is lacking, and agent such as Polytrim maybe adequate for providing broad-spectrum bactericidal coverage. Non-steroidals may be used, especially in patients who are at higher risk for cystoid macular edema. And use of topical corticosteroids is recommended to reduce risk of pain, and controlling inflammation after cataract surgery. Thank you.
