eyecing on the cake

Thursday, July 14, 2016

4 reasons NOT to buy glasses online

four-eyed cupcakes

Every now and then, I have patients tell me that they plan on buying their glasses online. I can certainly understand why that would be appealing: low prices, large selection, and ease. In our drone-delivery, instant-gratification culture, convenience is king! I, personally, am all about finding cheaper prices from the comfort of my Snuggie (before you start judging, it's a Buzz Lightyear Snuggie). However, knowing what I know about vision and eyewear, I would urge you to think twice before buying glasses online. In pursuit of convenience and ease, we forgo the knowledge and expertise of the eyecare professional team in precisely fitting and knowledgeably selecting our eyewear. This blog post is my attempt to "let the buyer beware."

----------

Here are 4 things to consider when looking into buying eyeglasses online:

1. Questionable lens accuracy and quality. For me, this is the biggest reason to avoid buying glasses online. A recent study of internet eyewear orders found that nearly half (44.8%) of the glasses examined had incorrect prescriptions or safety issues:

Nearly three out of 10 pairs (29%) of glasses ordered online had at least one lens that failed to meet the required prescription. When you buy a pair of glasses from an optometrist's office or optical, someone typically checks the lenses for accuracy and quality before the glasses are dispensed to you.
Nearly a quarter (23%) of the lenses failed impact resistance testing, which highlights a major safety issue. Children’s glasses performed even worse, with 29% failing impact testing. (1)

Quality and safety are a big deal, as is prescription accuracy. These are not areas where you want to cut corners. At a very minimum, you need to be sure that the power in your lenses is the power on your prescription. I have had more than a few patients come in complaining about the glasses they bought online, only to find that the prescription in their lenses is in fact not the prescription I wrote for them. And there's more to it than just having the prescription correct; you can still have headaches, eyestrain, and problems seeing even if the numbers match.

Beyond having the correct power in your lenses, you also need to be looking through the right part of the lens to see clearly and comfortably. The optical center of your lens should be placed right in front of the center of your pupil. For the maker of the glasses to know where exactly to put the lens within the frame to achieve that, an accurate pupillary distance is needed. Multi-focal lenses (lenses that allow you to see at more than one distance, like bifocals or progressive addition lenses) involve additional measurements and powers; fitting multifocal lenses is a careful process and should definitely be done by experienced professionals. The segment height is a specific measurement for multifocal lenses, and it needs to be measured while you are wearing the frame, with the frame positioned where you normally wear it. Both the pupillary distance and the segment height are very important measurements that influence what part of the lens you are looking through, and what power you are getting when looking through that part of the lens. The more complicated the prescription, the more crucial it is to consult with experienced professionals. Some forms of optical correction, especially for children, are prescribed as part of a treatment for a condition, such as accomodative esotropia or accomodative insufficiency. If given the incorrect treatment, the condition will not be effectively treated. After all, glasses are considered Class 1 Medical Devices by the Food and Drug Administration (FDA). Glasses are not just an accessory; they require a precise prescription and accurate measurements to enable you to see clearly and comfortably.

2. Lack of customization. Health care should be pursued in-person, because it should be tailored to the individual. What you need in eyewear depends on your specific prescription and visual needs. A conversation with your optometrist and optician about such things should happen in order to build a pair of glasses that gives you the best vision and comfort for your daily life. Do you use a computer all day? Do you drive for a living? Do you knit? Do you play golf? Now more than ever, there are SO many choices in terms of lens types, materials, and coatings; it really is important to speak with a knowledgeable expert to help you navigate the options and decide on what products suit your visual needs and increase your visual comfort.

3. Lack of input in selecting an appropriate frame. Frame selection is both an art and a science. Did you know frames have sizes? Glasses are NOT one-size-fits-all. If glasses don't fit properly, you can experience physical as well as visual discomfort. Aesthetically speaking, certain frame shapes look better on certain face shapes. But more importantly, there are some frame sizes and styles that should be ruled out based on your prescription and/or the type of lens you need. A trained optician can tell you what frames to avoid. The way a frame looks certainly matters, but there are many other factors to consider when choosing a frame for your lenses.

4. Customer service. This is by no means a rule, but in general, the smaller the shop, the better the customer service. There are typically only a few degrees of separation, if any, between you and the manager or owner. You have a person to go back to if you are having any issues with your glasses, or if you need a frame adjustment. I believe human interaction is SO important to building business relationships and creating loyalty. Maybe I'm an old soul, but it's just not the same as clicking around on a website or calling a 1-800 number.

----------

Every pair of glasses purchased online is not a disaster. But I would suggest that you as a consumer consider service and quality as well as price and convenience. Glasses are an investment, and you want your money to go towards a pair that fits properly and comfortably, and provides you with the best possible vision. If you choose to purchase your eyeglasses online, be informed and may the odds be ever in your favor! :)

CliffsNotes: Glasses are not one-size-fits-all accessories. A team of eye care professionals can help you choose a frame and lenses that are ideal for you, considering your prescription and visual needs. In my opinion, the convenience of ordering glasses online is not worth the potential compromise in accuracy and quality.

Additional recommended resources:

Thursday, May 19, 2016

cancer and the eye

I would venture a guess that everyone reading this blog has been affected by cancer, either personally suffering from it or having a loved one that is suffering/has suffered from it. That makes it a pretty relevant topic to discuss here. Eye cancer is rare, certainly, but it does exist. Most people don't see the eye as an organ, just like the lungs or liver, that can have tumors. In terms of eye tumors, there are many types of benign (harmless, non-invasive) and malignant (bad news bears) tumors that can be found in any part of the eyeball and surrounding tissue. For the sake of brevity, we won't talk too much about the benign tumors; instead, this post will just focus on the scary stuff.

First off: what is cancer? Cancer is a group of diseases characterized by uncontrolled cell division. These dividing cells may form tumors. Malignant tumors are cancerous; they can invade nearby tissue. Cancer originates in one place and can spread to other parts of the body. The term for this spread is metastasis. The National Cancer Institute has a great, easy-to-understand overview of cancer here. According to the Center for Disease Control (CDC) and the American Cancer Society (ACS), the most common cancers in the US are breast, prostate, and lung (1, 2).

From ACS

In terms of ocular cancer, there are various sites within and around the eye that cancerous tumors can be found. We'll go through some of the major types in each category.

1. INTRAOCULAR [within the eye]

Primary intraocular cancers are cancers that originate in the eyeball.

Retinoblastoma is the most common eye cancer in children, accounting for 3% of all childhood cancers. This rare cancer can be non-inherited or inherited via a mutation in the RB1 gene, which is also linked to an increased risk of osteosarcoma (bone cancer). All babies are screened at birth, but this may not be present at birth. That's why it is crucial to not only see your pediatrician for well-baby exams but to ALSO see your eye doctor (for more info on infant eye exams, read the InfantSEE post). Early diagnosis is key! The most common signs of retinoblastoma are a white pupillary reflex (instead of the normal red reflex that you often see when you take a flash photo) called leukocoria, and eye turns (strabismus) (3).

Leukocoria from retinoblastoma, image: University of Michigan

Uveal melanoma is the most common primary intraocular malignancy in adults. It forms in the eye's melanocytes, the cells that make pigment (melanin). [The uvea is the pigmented middle layer of the eye and includes the iris, ciliary body, and choroid. The choroid is the vascular tissue that lies between the retina (the light sensitive tissue that lines the back of the eye) and the sclera (the white part of the eye).] Choroidal melanomas account for 80% of all uveal melanomas, affecting six out of every one million Americans (4). Choroidal melanomas most often have no symptoms and are found during routine eye examination. Choroidal melanomas can metastasize, to the liver most commonly, also occasionally to the lungs, bone, skin, and brain (Kanski, 7th ed).

Choroidal melanoma, image: ECN

Primary intraocular lymphoma (PIOL) often presents in the elderly and immunocompromised, with possible symptoms of floaters, blurred vision, redness, and/or sensitivity to light. Lymphoma is a cancer of the lymphatic system, the system that helps protect the body from infection. Lymphoma is classified as either Hodgkins or non-Hodgkins. Non-Hodgkins lymphoma can be further categorized based on what type of cells are involved. Most are B-cell. Because lymph tissue is found throughout the body, lymphoma can begin nearly anywhere. Lymphomas can occur intraocularly but also can occur in other structures on/around the eye (more on that later). PIOL is primarily non-Hodgkins, B cell lymphoma, and is highly correlated with primary central nervous system lymphoma (PCNSL). In fact, up to 80% of patients with PIOL will be subsequently diagnosed with brain lymphoma (5).

Secondary intraocular, or metastatic, cancer is cancer that originates elsewhere in the body and spreads to the eye. Secondary intraocular cancer occurs more often than primary. The most common cancers to spread to the eye are breast and lung, and the most common place for them to spread within the eye is the vascular choroid. One study found that 34% of those eyes diagnosed with uveal metastasis did not have a history of cancer at the time of diagnosis. Further evaluation of that 34% revealed over a third of them had a primary tumor in the lungs (6). According to Wills Eye Hospital, about 25% of patients who present to the eye doctor with eye metastasis have no known history of systemic cancer and are later found to have a cancer in the body (7). Key point: the detection of cancer in the eye can precede the diagnosis of cancer elsewhere in the body, especially in the case of lung cancer.

2. CONJUNCTIVA [the tissue covering the white part of the eye]

Conjunctival squamous carcinoma occurs most often in older white males, and is linked to UV exposure. This rarely spreads to distant sites but can spread locally behind the eye and in the orbit (8).
Conjunctival melanoma appears as a pigmented area on the white part of the eye. It can arise from an existing nevus/mole or from a precancerous condition called primary acquired melanosis (PAM). Unlike a squamous carcinoma, there is a risk of spread to the lymph nodes and other organs (9).
Conjunctival lymphoma presents as a salmon-colored patch, often found under the eyelids, most commonly in late adulthood. In about 20% of cases, lymphomas in other parts of the body are found (10).

Conjunctival lymphoma, image: Wills Eye

3. EYELIDS [The Skin Cancer Foundation reports that eyelid skin cancer accounts for 5-10% of all cases of skin cancer.]

Basal cell carcinoma (BCC) is by far the most common eyelid tumor, accounting for about 90% of eyelid cancers. Most occur on the lower lid, and are found more commonly in older, fair-skinned people with chronic exposure to UV radiation. BCC is locally invasive but does not metastasize (Kanski, 7th ed).

BCC, image: Wills Eye

Squamous cell carcinoma (SCC) is similar to BCC in that it's typically found on the lower lid of older, fair-skinned patients with chronic exposure to UV radiation. It is less common than BCC, but more aggressive, and metastasis to nearby lymph nodes occurs in 20% of cases (Kanski, 7th ed).
Melanoma accounts for less than 1% of eyelid cancers. Melanomas are aggressive and potentially life-threatening. They are typically pigmented, but sometimes not. Melanomas can look like moles (nevi), or can arise from moles. The ABCs of melanomas point out characteristics of malignant melanomas that are usually not present with benign moles:

Asymmetry
Border (uneven or irregular)
Color (non-uniform, variety of colors or shades)
Diameter (bigger is not better)
Evolution (change over time)

Sebaceous gland carcinoma (SGC) is a malignant cancer arising from the oil glands in the eyelids. It typically presents as a painless bump on the upper lid, and can be difficult to diagnose. Sebaceous carcinoma is found more frequently in females than males, and is more common in the elderly (Kanski, 7th ed). It can metastasize to lymph nodes and other organs (11).
Merkel cell carcinoma (MCC) is a rare form of skin cancer that grows quickly and metastasizes early. It appears as a raised, red-violet bump on the skin, typically linked to chronic sun exposure. MCC is most common in elderly caucasians (12).

MCC, image: pubmed

4. ORBIT [the eye socket, including bones, muscles, nerves, and the lacrimal glands (the almond-shaped glands that secrete tears)]

Rhabdomyosarcoma is a malignant tumor that arises from skeletal muscle. About 10% of cases involve the orbit, usually causing the eyes to bulge (proptosis) (13, 14).

Lacrimal gland lymphoma accounts for over a third of all malignancies of the lacrimal gland, predominantly affecting elderly women (15). It was found that one to two-thirds of patients develop systemic disease (if not already present at the time of orbital biopsy), usually within 2.5 years of orbital biopsy (16).
Adenoid cystic carcinoma of the lacrimal gland is the most common malignant epithelial tumor of the lacrimal gland. Occurring most often between the ages of 40 and 60, adenoid cystic carcinoma causes the eye to be displaced downward, and can also cause pain as it spreads to the nearby nerves and bone (17,18).

CT of an adenoid cystic carcinoma of the lacrimal gland, image: ECN

Malignant mixed tumor of the lacrimal gland is the second most common malignant tumor of the lacrimal gland. It occurs most often in the elderly. It can appear without a history of lacrimal mass, or it can arise from a prior benign mass that was incompletely excised or a long-standing mass that suddenly increases in size (19. 20).

5. BRAIN
Why do I include this in our conversation? Because the eyes are an extension of the brain, and some brain tumors can be detected during an eye examination. I plan to do a separate blog post about it, but in short, visual field exams can help detect and even localize some masses in the brain.

CliffsNotes: Cancer can start in and around the eye, or it can spread to the eye from elsewhere in the body. It often doesn't have symptoms, so be sure to get your yearly dilated eye exam whether you have a history of cancer or not!

Additional recommended resources:

Saturday, April 16, 2016

eye floaters

Ever wonder what those squiggly things are that float around in your field of vision? They may look like bugs, strands, or cobwebs, and they are especially noticeable when you're looking at a plain, bright background (like a clear sky). When you move your eye to get a closer look, those sly boogers drift away! Wonder no more: they are vitreous floaters.

Let's do a quick anatomy review before we continue: The vitreous (sometimes called vitreous humor or vitreous body) is the transparent, gel-like substance that fills the area between the lens and the light-sensitive tissue that lines the back of the eye (retina). The vitreous accounts for about 80% of the eye's volume. It is made up of water (~99% of its volume is water) and a network of proteins (collagen fibrils) and sugars (hyaluronan). As we age, the vitreous becomes less gel-like and more liquid. The vitreous is attached to the retina at a few key points.

From Mayo Clinic

What is a floater?
What we see as floaters are actually the shadows cast on the retina by substances in the vitreous. Those substances can be clumps of protein, blood cells, or pieces of tissue. Check out this great video for an illustration.

Below are a couple of Optomap images that show floaters (both photos are from the same patient- we decided she just has very photogenic floaters). Depth doesn't translate well in these photos, so here's an explanation of what we are looking at: if you cut the eyeball in half, the red tissue you see in the photos is the inside lining of the back of the eye (retina), and the strands/blobs that the arrows are pointing to are the floaters in the vitreous, which is in front of the retina.

What causes floaters?
Sometimes, floaters are no big deal. The floaters that we see from time to time are usually just that; they're clumps of fibers that cast shadows on the retina. Other times, floaters are a symptom of an eye condition.

Posterior vitreous detachment (PVD): A PVD can occur as a result of trauma, though it's most often a result of age-related changes in the vitreous. As the vitreous shrinks and becomes more liquid, it may collapse and pull away from the retina. The point where the vitreous was attached to the optic nerve is what most people complain of- a large floater that appears somewhat suddenly. A PVD typically occurs earlier in people who are near-sighted and those who have had cataract surgery or eye trauma (1). Another symptom that may be experienced during a PVD is flashes of light. The mechanical pulling of the vitreous on the retina as it detaches can cause stimulation of the retinal photoreceptors, resulting in the perception of flashes of light. The concern with a PVD is that the pulling of the vitreous from the retina may result in a retinal break. Between 8% and 26% of acute, symptomatic PVDs are associated with a retinal tear upon initial examination. Even if no break is found upon initial examination, there is still a 2-5% chance of a retinal break being found a few weeks later (2, 3, 4). Take home point: it's impossible to know if there is cause for concern based on symptoms alone; a thorough examination is necessary.
Retinal break: A retinal break can occur as a result of a PVD or trauma. Most retinal breaks are treated, as a break can allow fluid under the retina and cause a retinal detachment, which results in permanent vision loss if untreated.
Vitreous hemorrhage: The vitreous contains no blood vessels, so blood in the vitreous comes from the leakage of vessels into/near the vitreous. This finding is usually associated with trauma, a PVD (with or without retinal tear, but more often with), or vascular disease. The source of the blood can be breakage of a normal retinal blood vessel, as a result of a tear or trauma, or it can be breakage of an abnormal blood vessel (neovascular membrane). For example, I had a young patient with insulin-dependent diabetes come in complaining of a cobweb in her vision. The cause of her symptoms was a large hemorrhage in the vitreous stemming from diabetic retinopathy. She had a neovascular membrane form in the back of the eye; these vessels are inherently fragile and bleed easily.
Vitritis: A vitritis is an inflammation of the vitreous body. The inflammatory cells in the vitreous can cause floater-like symptoms. Blurred vision is also a common accompanying symptom. A vitritis can occur as a result of an infection, autoimmune disorder, or trauma, or it can be idiopathic (no known cause). This entity requires treatment.

I have floaters! What should I do?
As mentioned earlier, a few floaters every now and then is not unusual. However, you should see your eye doctor right away if you experience:

sudden floaters and/or flashes of light
an increase in the frequency and/or number of your floaters
a loss of peripheral vision

How are floaters treated?
Really, they're not. The underlying cause of the floaters may need treatment, as in the case of a retinal tear, a vitreous hemorrhage, and a vitritis. PVDs, in the absence of a retinal tear, are just monitored. Floaters often become less noticeable as they break apart and settle towards the bottom of the eye, and as the brain learns to ignore them. Rarely, there are instances where laser treatment or vitrectomy (a surgery where the vitreous is removed) may be pursued to remove large, very symptomatic floaters. However, risks-vs-benefits must be carefully considered, as floaters are harmless and there are risks associated with any surgical procedures.

CliffsNotes: Occasional floaters are normal and increase with age. However, if you have sudden floaters and/or flashes of light, a loss of peripheral vision, or an increase in the frequency and/or number of your floaters, it's a good idea to go see your optometrist ASAP.

Additional recommended resources:

Monday, February 22, 2016

age-related macular degeneration

Fundus cupcake sprinkled with drusen

February is Age-related Macular Degeneration (AMD) Awareness Month. AMD is one of the leading causes of irreversible vision loss among Americans over 60 (1).

Let's preface our AMD discussion with a quick anatomy review. The tissue that lines the back of the eye is called the retina. The retina has millions of light-sensing cells called photoreceptors (rods and cones). These cells absorb light and convert it into signals that are sent to the brain via the optic nerve, allowing us to see the world around us. The macula is a small area near the center of the retina that is responsible for our central, sharpest vision. Within the macula is a high density of cones, the photoreceptors responsible for color vision. When you look at retinal photos (or the cupcake above), the macula is the dark red area. For reference, here is a labeled photo of a healthy retina.

What is age-related macular degeneration?
Age-related macular degeneration, commonly called AMD or ARMD, involves a breakdown of the tissue that makes up the macula. Waste products called drusen accumulate beneath the retina, in and around the macula. Drusen are the yellow-ish deposits you see in the photo below. This disruption causes the photoreceptor cells to die, which impairs vision. Over time, central vision becomes blurry and distorted. AMD can be classified as either dry or wet.

Dry (non-exudative) AMD: This is the most common form of the disease. The early and intermediate stages of dry AMD involve drusen and/or pigmentary changes in the retinal pigment epithelium (RPE). The late stage involves the death of large areas of retinal tissue, called geographic atrophy, which affects central vision significantly.

Fundus photo of dry AMD

Wet (exudative) AMD: About 10% of dry AMD cases progress to the wet form, meaning that neovascularization has occurred. Neovascularization is the formation of new, abnormal blood vessels under and into the retina. These vessels are weak and can leak, causing vision loss. Neovascularization is bad news bears and warrants prompt treatment (discussed below). Wet AMD typically affects vision more rapidly and more significantly than dry AMD.

What are the risk factors?
AMD is a multifactorial disease. The exact cause is unknown, but research suggests some factors increase the risk of AMD:

Age. Age is a major risk factor, with most cases typically occurring after the age of 50.

Smoking. Several studies have found a positive association between smoking and the development of AMD. The risk of developing the disease for current smokers is at least two to three times greater than the risk for non-smokers (2, 3). Smoking is the leading modifiable risk factor for AMD.

Family history/genetics. Having a close relative with AMD increases the risk of developing the disease (4). Researchers have identified variants of a few complement genes that are associated with an increased risk of developing AMD (5).

Diet. Those with diets low in omega-3 fatty acids and antioxidants may be at greater risk of progression to advanced disease (6).

Hypertension. Some studies have shown wet AMD to be associated with moderate to severe hypertension (7, 8).

Obesity. Research has suggested an association between body mass index (BMI) outside the normal range and early AMD (9) as well as progression to advanced AMD (10).

High cholesterol. Elevated high-density lipoprotein (HDL) levels may be associated with higher risk of AMD (11).

Sun exposure. Exposure to large amounts of visible and blue light may play a factor in disease progression (12, 13, 14).

Ethnicity. AMD is more prevalent in Caucasians.

Gender. AMD is more prevalent in females.

How is AMD diagnosed?

AMD is diagnosed during a dilated eye exam. It may manifest itself in changes in central vision, but it most likely will not in the early stages. Upon dilation, pigmentary changes and/or drusen may be noted by your eye doctor in/around the macula.

How it is monitored and treated?

Various tools exist to help monitor AMD and guide treatment:

Retinal photo. Periodic photos allow for monitoring progression over time.
Amsler grid. This is an easy way for patients to monitor for changes in their central vision. AMD can cause parts of the grid to appear distorted or missing. I suggest that my AMD patients leave it on their refrigerator and test each eye a few times a week, monitoring for any changes.

The ForeseeHome monitoring device utilizes a similar concept. Patients are presented with a series of straight lines containing a wave/bump, and the patient must identify where the distortion is. The device collects the data and alerts the patient's eye doctor if there are abnormal results.

Optical Coherence Tomography (OCT). A scanning laser is used to image the tissue of the back of the eye. It can produce a cross section of the macula, showing retinal thinning or thickening.

OCT showing drusen (red arrows) below the retina

Fluorescein angiography (FA). Fluorescein dye is injected into a vein in the arm and photos of the retina are taken as the dye reaches the retinal vessels. An FA may be ordered to identify neovascular membranes, evaluate leakage, and/or guide treatment.
Coming down the pike: OCT Angiography. This technology just got FDA approval in the US. It will allow doctors to image the vessels of the retina and choroid without injecting a contrast dye (unlike an FA).

Treatment:

Dry- There is no FDA-approved treatment for dry AMD as of yet. Plenty of research is being done in this area. Studies have shown that antioxidant supplementation may help slow progression to advanced AMD (15, 16). For more information on ocular nutrition, check out this post.
Wet- Most cases of wet AMD are treated with anti-vascular endothelial growth factor (VEGF) drugs. Anti-VEGF drugs are periodically injected into the eye to stop abnormal vessel growth. Photodynamic therapy (PDT) and laser photocoagulation are also treatment options, though less commonly used.

Vision loss is often life-altering and difficult to cope with. There are support groups and low-vision rehabilitation resources available to those dealing with AMD. Low vision aids include hand-held, stand, or spectacle magnifiers, video magnifiers (CCTVs), and even implantable telescopes! We'll do a separate post on low vision devices and rehab services later on, but here's a great place to begin: Living Well with Low Vision.

CliffsNotes: AMD is a multifactorial disease with several modifiable and non-modifiable risk factors. The best way to prevent vision loss from AMD is to have routine dilated eye exams, especially if you fall into a higher-risk category.

Additional resources:

Sunday, February 14, 2016

Happy Valentine's Day!

Sunday, January 24, 2016

worldwide blindness

I recently went on an overseas medical mission trip, and it got me thinking. Thinking about a lot of things, but as it pertains to this blog: worldwide blindness. So this post will unpack some of the major diseases affecting vision globally.

The leading causes of preventable blindness world-wide are cataracts, glaucoma, trachoma, and onchocerciasis. We do not see the latter two much, if at all, in the United States; they are prevalent primarily in less developed areas, where there are also specific environmental hazards (1).

TRACHOMA
Trachoma is the world's leading infectious cause of preventable blindness. Eight million world-wide are visually impaired as a result of trachoma (2). It is caused by a bacteria, Chlamydia trachomatis, and typically spreads by contact with an infected person’s hands or clothing, or can be transmitted by flies who have had contact with discharge from an infected person's nose or eyes. Trachoma is endemic in the poorest, most rural parts of Africa, Asia, the Middle East, South and Central America, and Australia (3), where lack of access to water and sanitation play a role in the disease's proliferation.

Trachoma spreads easily among children, and from child to caregiver. Blindness typically occurs in adulthood, and affects women 3 times more than men (4). Left untreated, the repeated trachoma infections cause scarring of the conjunctival tissue of the eyelid, which in turn causes the eyelashes to turn in (trichiasis). The lashes then rub against the cornea, which causes scarring that leads to visual impairment and blindness.

Trachoma grading card (image: WHO)

Control: The SAFE strategy is a public health initiative developed by the World Health Organization (WHO), combining treatment with prevention to eliminate blinding trachoma by the year 2020. Trachoma is transmitted through close contact, so it is a community problem and all intervention must be community-targeted.

Surgery to correct trichiasis. As discussed earlier, trichiasis is the precursor to blindness.
Antibiotics to treat active disease. Single dose azithromycin, donated by Pfizer in the 1990s, is the treatment of choice (5).
Facial cleanliness and Environmental improvement. While the former two points of the SAFE strategy target treatment of the disease, the latter two focus on prevention. Facial cleanliness reduces disease transmission. Better environmental sanitation and proper waste disposal helps control the fly population (6).

ONCHOCERCIASIS

Onchocerciasis, also known as river blindness, is the second leading infectious cause of blindness globally. It accounts for at least one million cases of blindness or severe visual disability. The majority of those infected live in sub-Saharan African countries. Onchocerciasis is caused by a parasitic nematode, Onchocerca volvulus. The worms induce intense inflammatory responses of the skin and eyes, especially when they die (7). The disease is transmitted from person to person by a black fly of the genus Simulium. Repeated bites are usually necessary for infection. The fly breeds near rivers and streams.

Onchocerciasis causes inflammation in the eyes (uveitis, keratitis, chorioretinitis, optic neuritis (8)) and the skin (itchy rash, nodules under the skin). The disease's toll extends into the social and economic realm as well. Once blind, affected individuals have a life expectancy of only one third that of the sighted, and most die within 10 years (9). There is also a social stigma attached to the skin lesions and disfigurement associated with this disease.

Sclerosing keratitis in Onchocerciasis (image: CEH Journal)

Control: Onchocerciasis elimination strategy involves vector control and/or large scale ivermectin chemotherapy (10).

In terms of vector control, regular aerial spraying of Similium breeding sites for at least 14 years is recommended (until the infection has died out of the human population).

A single dose of ivermectin (Mectizan), donated by Merck in the 1980s, is effective for up to a year. It has the added benefit of helping with intestinal worms, scabies, and head lice, which are common problems in the areas where this disease is endemic. Ivermectin must be given yearly for 12-15 years.

CliffsNotes: The elimination of preventable worldwide blindness is within sight!

Additional Resources:

Thursday, December 17, 2015

cataracts

What is a cataract?
A cataract is a clouding of the part of the eye called the lens. The lens sits right behind the colored part of the eye (iris), and it helps focus light onto the light-sensitive tissue that lines the back of the eye (retina). It is normally clear. Over time, the proteins that make up the lens begin to clump together and cause a clouding of the lens. Most cataracts progress slowly and eventually affect vision. While most cases involve both eyes, a cataract can develop in only one eye.

For those of you, like myself, who need a visual, here's a good video to watch.

Are there different types of cataracts?
There are many different types of cataracts, and a person can have more than one type.

Age-related, or senile: cataracts that result from the normal physiological changes that occur in the lens of the eye. Most, but not all, cataracts are age-related.

Nuclear sclerotic cataracts involve a yellowing of the central lens. They sometimes cause a shift in prescription, leading to a temporary improvement in near vision (often referred to as "second sight").
Cortical cataracts involve spoke or wedge-like opacities that often start around the periphery of the lens.
Posterior subcapsular cataracts involve a hazing of the back of the lens. This type of cataract may progress more rapidly and affect vision more significantly than others. Posterior subcapsular cataracts may be seen more frequently in diabetic patients, in patients using steroids, and in patients who have had vitreoretinal surgery.

Congenital: cataracts that are present at birth. The majority affect both eyes, and they vary in severity. If the cataracts are significant and obstruct vision, they are removed early on to allow vision to develop properly, preventing deprivational amblyopia.
Traumatic: cataracts that result from blunt or penetrating trauma to the eye.

There are still other, rarer cataracts that occur secondary to disease processes. For instance, a Christmas tree cataract is often found in those with myotonic dystrophy.

Images courtesy of the AOA

Can you prevent cataract formation?
One theory suggests that cataract formation is due to oxidative changes in the lens, and some studies (1, 2, 3) have shown that antioxidant consumption can help reduce the risk of cataracts. (For more information on how diet affects the eye, check out this previous post). While cataract prevention is still being researched and debated, we do know of risk factors for progression that we can aim to reduce/eliminate. Evidence suggests that UV exposure increases the risk of cataract development (4, 5), so wearing UV-blocking sunglasses is a good practice. Smoking increases the rate of cataract formation (6, 7), so that's yet another reason to kick the habit.

What are the symptoms?
Early on, cataracts have few or no symptoms. Colors may appear faded. You may begin to notice glare, especially when driving at night. Because the lens is no longer clear, it scatters light, which prevents a sharp, clear image from focusing on the retina. As the cataracts progress, they begin to cause blurry vision that is not correctable with glasses or contact lenses. At that point, the option of surgery is discussed. Cataracts can be diagnosed by your optometrist during your annual dilated eye exam.

What is the treatment?
While cataracts are the leading cause of visual impairment world-wide (47.9%, according to the WHO), they are easily treated here in the US. Cataract extraction is currently the only treatment available. This procedure involves removing the natural lens of the eye and replacing it with an intraocular lens (IOL). There are many different types of IOLs available. It is up to the patient and his/her team of eye care professionals to discuss the options and determine which type of IOL is best suited for the patient. Here is a video of a local ophthalmologist performing cataract surgery (if you're squeamish, you should probably pass on watching it).

The future may hold non-surgical options for the prevention and treatment of cataracts. In a recent study, dogs who received treatment with lanosterol injections and drops showed a noteable reduction in their cataracts.

Do they recur?
No- once a cataract is removed, it is gone. However, you can develop a posterior capsular opacification (PCO) after cataract surgery. That's when the lens capsule that holds the implant becomes hazy. It is sometimes referred to as an "after-cataract" or "secondary cataract," but it is not a true cataract. A YAG laser capsulotomy is a simple procedure that involves using a laser to remove the hazy portion of the capsule that is obstructing vision.

CliffsNotes: A cataract is a clouding of the lens of the eye. There are several different types, but the most common are the natural results of aging. When cataracts affect vision significantly, the option of surgical extraction is discussed.

Additional Resources: