Fun, fluorescein, and fundoscopy unite as our esteemed guest, Dr. Nisha Chadha @iEducatorMD (Mount Sinai School of Medicine) brings us ophthalmology for primary care! Dr. Chadha is a medical educator and the content creator of the med-ed simulation website 20/20 Sim. She teaches us the 3-vital signs of ophthalmology, how to recognize common diabetic eye diseases, how to explain diabetic retinopathy to our patients, how to optimize a patient for cataract surgery and so much more. This episode is truly vision-ary!
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The 3 – vital signs of ophthalmology are vision, pupils, and intraocular pressure. These can help you triage the urgency of a complaint.
To assess vision, utilize a Snellen chart or a phone application to check the visual acuity in each eye with the patient wearing any correction they have (ie glasses or contact lenses). A sudden decrease in vision needs to be evaluated urgently. The acuity and amount of change in vision can be used to help determine whether the triage to ophthalmology should be immediate, or if it can be delayed further. If no eye chart is available, you could ask a patient to try to read something with each eye individually. When concerned for significant vision loss, one could assess the patient’s ability to identify hand motion. If a patient cannot detect hand motion on a physical exam, this would warrant an immediate ophthalmology referral. Inability to detect hand motion indicates worse vision than 20/400, which is the visual acuity if one can only see the big. E” on the Snellen eye chart.
Non-reactive pupils, presence of an afferent pupillary defect (APD), and anisocoria are signs that a serious condition may be present. Anisocoria is when the pupils are asymmetric. An afferent pupillary defect can be detected by the “swinging flashlight test” (Stanford Medicine Physical Exam, Pupillary Response) . When you swing a flashlight from eye to eye, both pupils should remain constricted due to the consensual response. If when you are moving the light towards the affected eye, the pupil paradoxically enlarges (instead of remaining constricted), then this is considered an APD. It suggests that there is damage along the afferent pathway, like the retina or optic nerve.
Intraocular pressure (IOP) can be checked with a handheld tonometer device to measure pressure. If none is available, one way to roughly assess for high IOP can be to palpate the eye over a closed eyelid for firmness with the pads of your fingers. Look for asymmetry in firmness of the eyes, and if needed you can utilize your eye’s softness as a reference point.
Diabetic ocular complications can range from cataracts, to non-proliferative diabetic retinopathy (NPDR) with or without macular edema, then to proliferative diabetic retinopathy (PDR) which can be further complicated by vitreous hemorrhage or tractional retinal detachments (NIH – Diabetic Eye Diseases). DR and early cataract development are common ocular complications of diabetes. Over time diabetes can cause damage to the blood vessels in the eye, causing changes in the retina such as microaneurysms that leak into the macula causing macular edema which leads to blurry vision. As the micro vasculopathy progresses, ischemia develops leading to an increase in vascular endothelial growth factor (VEGF). Increased VEGF stimulates neovascularization in the retina, or development of abnormal new blood vessels which is when the stage of retinopathy is referred to as PDR. These abnormal vessels can bleed or contract which can lead to vitreous hemorrhage or retinal detachment, respectively. (Whitmer, 2003).
For patients with type 2 diabetes, the ADA guidelines recommend an initial dilated and comprehensive eye exam at the time of diagnosis, and yearly thereafter (ADA, 2017). In contrast, for patients with type 1 diabetes, they recommend an ophthalmology exam for screening within the first 5 years of diagnosis of type 1 diabetes (ADA, 2017). Expert opinion: having a baseline exam at time of diagnosis can be helpful if there are resources available. If the screening exam is normal, AAO guidelines recommend continued annual examinations (AAO, 2019). Expert opinion: if a patient has poorly controlled diabetes Dr. Chadha may opt to see the patient within 6 months to assess for further ocular fluctuations.
[Producer Note – The ADA guidelines for interval screening state that if there is no evidence of DR on a comprehensive eye exam for 1 or more years, then eye exams every 2 years may be considered (ADA, 2017). This contrasts to the AAO Preferred Practice guidelines, which recommends continued yearly eye exams in patients with type 2 diabetes (AAO, 2019)]
Teleretinal imaging has emerged for screening for diabetic retinopathy. The program was designed to increase screening, but it only captures an image of the macula, and does not include images of the peripheral retina. There can be limitations to the quality of this image, and does not replace a full examination (ADA, 2017).
A little improvement in a patient’s glucose control goes a long way in preventing ocular complications. Decreasing a patient’s A1C by 10% (ie, A1C decreasing from 8% to 7%), can decrease microvascular changes in the eye by up to 43% (Diabetes Control and Research Trial Group, 1995)!
When looking at a return report from ophthalmologists there are many abbreviations. The website 2020sim.com provides a guide to these medical abbreviations.
Many of the terminology associated with diabetic eye diseases are complex. To help counsel patients on their diagnosis Dr. Chadha displays an image of the eye and utilizes an analogy – the eye is a camera. She counsels patients to view the retina as the “film” of the eyes, and this is where our 20/20 vision lives. We can get swelling in the film due to damage from diabetes creating “drops of water” on the films. This means that the picture may not always be clear. This analogy helps break down the terminology in a simple way for patients to understand.
Utilizing a patient’s clinical symptoms can help guide a differential diagnosis. Asking them about pain, and any pattern of vision loss is instrumental. Most of the nerve receptors in the eye are located in the “front”, within the cornea and conjunctiva. Any cornea pathology, such as an abrasion or ulcer can cause eye pain. The retina does not have pain receptors, and thus pathology mainly within the retina presents without pain. With NPDR there usually is no pain, but rather slow painless deterioration in vision. Vitreous hemorrhage presents as a painless, sudden loss of vision. Retinal detachment also causes a sudden change in vision, but is typically characterized by a curtaining effect on the vision. It can be associated with flashing lights or floaters from disturbances or stimulation to the retina.
If fluorescein stain is available, you can utilize it within your office to assess for corneal abrasions or ulcers. After placing fluorescein stain in the eye, utilize the blue light functions on the fundoscope to assess for staining. Any staining will light up as green under the blue light and suggests a corneal abrasion or ulcer.
If on a physical exam you note a “firm eye” on palpation – think elevated IOP, likely caused by “glaucoma something”. In severe PDR, abnormal blood vessels can also grow into the front of the eye and into the trabecular meshwork, which normally should drain fluid into Schlemm’s canal, leading to a severe acute secondary form of glaucoma. The blood vessels block off the aqueous humor outflow, causing the IOP to become extremely elevated and can cause one of the most severe diabetic eye complications – neovascular glaucoma. For our patient with elevated IOP causing pain, a change in vision, and poorly controlled diabetes, neovascular glaucoma should be high on the differential diagnosis. In contrast, in a patient with severe, painless vision loss and poorly controlled diabetes, vitreous hemorrhage or retinal detachment would be more likely.
In general, for patients with NPDR and macular edema, the first line is often intravitreal injections of anti-VEGF (Stewart, 2016). Once the disease has progressed to PDR, treatment involves a combination of anti-VEGF injections and pan-retinal photocoagulation with lasers (Stewart, 2016). Progression to vitreous hemorrhage or retinal detachment often requires surgery to correct the underlying process (Berdahl, 2007, Boyd, 2020). The goal of these treatments are to improve or preserve vision. Dr. Chadha states that generally these interventions are fairly well tolerated by patients.
Patients with a diagnosis of macular degeneration do benefit from AREDS vitamins (Age Related Eye Disease Study Research Group, 2001). They have been demonstrated to decrease progression to advanced AMD over 5 years by about 25% (NIH AREDS2 FAQ). AREDS-2 vitamins include vitamin C, vitamin E, beta-carotene, copper, lutein, zeaxanthin, zinc (NIH AREDS2 FAQ). There is no evidence that AREDS-2 vitamins will impact the health of patients who do NOT have macular degeneration. Instead, Dr. Chadha recommends counseling a patient on a diet rich in green leafy vegetables for prevention.
Dr. Chadha recommends counseling patients to think of cataracts as the “lens” of the camera. Cataracts are when the lens becomes opacified and thus causes blurred vision. Medications such as chronic steroid use can accelerate cataract formation (Urban, 1986). In addition to cataract development, steroids can cause an increase in intraocular pressure. Dr. Chadha recommends that if an individual is on chronic oral, nasal (fluticasone), or topical steroids to have their IOP checked to see if their intraocular pressure is sensitive to steroids, a condition to referred to as steroid response glaucoma. UV exposure can contribute to cataract development, and in general it is recommended to wear sunglasses during periods of high UV exposure (McCarthy C, 2002, AAO Health Prevention Tips, 2020).
Perioperative Optimization for Cataract Surgery
Cataract surgery performed under topical anesthesia has a low risk of bleeding complications. The lens of the eye and cornea, through which the small incisions for surgery are made, have no blood vessels. The concern for a patient on anticoagulants previously came from an older, less commonly used anesthetic technique involving a retrobulbar injection, but this procedure has been largely replaced with topical anesthesia to anesthetize the eye. The bleeding risk is minimal during these procedures (Katz J, 2003). Dr. Chadha recommends that it is ok to continue DOACs, warfarin, aspirin, and antiplatelets the day of the procedure if needed.
Tamsulosin can cause intraoperative floppy iris syndrome, and once an individual is exposed the risk often remains (Cantrell M, 2008). Stopping the medication won’t necessarily change the risk of developing this complication. The key is for the ophthalmologist to be aware of tamsulosin exposure so that they are prepared with the proper techniques and instruments to manage this condition if it occurs in the OR. For hypertension medications, Dr. Chadha recommends continuing these medications with small sips of water in the morning of the procedure. Dr. Chadha notes that if a patient has elevated blood pressure, it could increase their risk of procedural bleeding.
Typically, a patient receives “light” sedation with MAC anesthesia during the procedure, because the surgeon may need a patient to follow gaze directions during the operation. During your periop evaluation take into consideration that the patient must be able to lay supine during the surgery without coughing. For certain patients, such as those with CHF, optimizing fluid status for surgical positioning is necessary.
Dr. Chadha recommends thinking of medication eye drops for glaucoma as similar to medications for HTN. Often, the more drops a patient is on, the higher the IOP. She discourages patients from being off of all their medications for multiple days, and to try to get the patient back on at least a few of their home eye drops as soon as possible. The change from a low pressure to a high pressure in the setting of missing home medications can be stressful to the optic nerve. If a patient is on one drop, but misses a few days, restarting within a few days is the goal.
Listeners will discuss screening, counseling, and management of common ocular diseases seen within primary care.
After listening to this episode listeners will…
Dr. Chadha reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
Chan C., Chadha N., Okamoto E., Watto MF. “#237 Ophthalmology for Primary Care”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list Original air date October 19, 2020.
The Curbsiders are partnering with VCU Health Continuing Education to offer FREE continuing education credits for physicians and other healthcare professionals. Visit curbsiders.vcuhealth.org and search for this episode to claim credit.
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