High refractive index vs. regular lenses: What’s right for you?

hand holding a pair of spectacles

High-index spectacle lenses are the right choice if you want thinner, lighter lenses and glasses that are as attractive and comfortable as possible.

Thinner, lighter high-index lenses are especially recommended if you have a strong eyeglass prescription for short sightedness, long sightedness or astigmatism. But high-index lenses can make your spectacles noticeably slimmer, lighter and more attractive regardless of how strong your prescription is.

Most spectacle wearers are short sighted, which requires corrective lenses that are thin in the centre but thicker at the edge of the lens. The stronger the prescription, the thicker the edges.

Most of today’s fashionable frames are made of plastic or metal with rims thinner than the lens itself.

Also, popular rimless mountings mean that the edges of the lenses are completely exposed.

In either case, the lens edges are highly visible, and thicker edges can detract from the appearance of your eyewear.

How high-index lenses vs. regular spectacle lenses

Spectacle lenses correct refractive errors by bending (refracting) light as it passes through the lens. The amount of light-bending ability (lens power) that’s needed to provide good vision is indicated on the spectacle prescription provided by your optician.

The difference a high-index lens material can make: the same correction for nearsightedness in regular plastic lenses (left) vs. high-index lenses (right). Images: Essilor

 

Refractive errors and lens powers required to correct them are measured in units called dioptres (D). If you are mildly shortsighted, your lens prescription might say -2.00 D. If you are highly myopic, it might say -8.00 D.

If you are longsighted, you need “plus” (+) lenses, which are thicker in the centre and thinner at the edge.

Regular glass or plastic lenses for high amounts of shortsightedness or long sightedness can be quite thick and heavy.

Fortunately, manufacturers have created a variety of new “high-index” plastic lens materials that bend light more efficiently.

This means less material can be used in high-index lenses to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.

Advantages of high index-lenses
Thinner

Because of their ability to bend light more efficiently, high-index lenses for shortsightedness have thinner edges than lenses with the same prescription power that are made of conventional plastic material.

Lighter

Thinner edges require less lens material, which reduces the overall weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in conventional plastic, so they’re more comfortable to wear.

High-index glass lenses also have thinner edges, but high-index glass is heavier than conventional glass, so there is not as much weight savings with glass as there is with plastic lenses.

Lightweight lenses are even more of a benefit for long sighted prescriptions, which can make conventional lenses very heavy.

And most high-index lenses also have an aspheric design, which gives them a slimmer, more attractive profile and reduces the magnified look that conventional lenses cause in strong longsighted prescriptions.

High-index lens choices

There is a wide variety of thin, lightweight high-index spectacle lenses, based on how efficiently they bend light.

The light-bending ability of spectacle lenses is determined by the “refractive index” of the lens material. This refractive index is the ratio of the speed of light when it travels through air to the speed of light when it passes through the lens material.

The speed of light is reduced the more it is refracted as it passes through a lens material. Therefore, lenses that bend light more efficiently have a higher refractive index than those that bend light less efficiently, and lenses with a higher refractive index are thinner than lenses of the same power made of materials of a lower refractive index.

In short: the higher the refractive index, the thinner the lens.

Conventional plastic lenses have a refractive index of approximately 1.50. For glass, it’s 1.52.

Any lens material with a refractive index that’s higher than that of glass or plastic is considered to be high-index.

High-index plastic lenses are now available in a wide variety of refractive indices, typically ranging from 1.53 to 1.74. Lenses with a refractive index of 1.70 or higher typically are at least 50 percent thinner than conventional plastic lenses.

Also, generally speaking, the higher the index, the higher the cost of the lenses.

Your spectacle prescription also determines what kind of high-index material you might want for your lens. The highest index materials are used primarily for the strongest prescriptions.

If you want high-index lenses, be sure to ask for them. But rely on your optician’s advice regarding which index to use. Your optician can explain which high-index lenses are the best choice for your needs and budget.

Most of today’s popular lens designs and features — including progressive lenses and photochromic lenses — are available in high-index materials. But there are exceptions, so ask us for details.

AR coating: A perfect companion for high-index lenses

All lens materials block some light from passing through the lens. This light reflects back from the lens surface, causing distractions and reducing the clarity of night vision.

Conventional glass or plastic lenses reflect about 8 percent of light that otherwise would reach the eye. High-index lenses reflect up to 50 percent more light than conventional glass or plastic lenses.

For the best vision and appearance, it’s a good idea to have an anti-reflective lens coating (AR coating) applied to high-index lenses. AR-coated high-index lenses transmit up to 99.5 percent of light to the eye for optimum vision.

And because AR coating virtually eliminates lens reflections, it makes high-index lenses appear nearly invisible, so others see your eyes, not your lenses.

Also, studies have shown that spectacle lenses with anti-reflective coatings provide sharper night vision with less glare — a real advantage for night drivers.

Source: all about vision – www.allaboutvision.com/en-gb/eyeglasses/high-index-lenses/


Lighting Tips For Less Eye Strain And Better Visibility

Light… it’s the most essential element of vision. We are surrounded by it all day, whether it be natural or artificial.
So it’s no surprise that we frequently get asked if certain types of light can negatively affect our eyes. Here we’ve compiled some tips so you can protect your eyes and prevent strain!

Adjust Your Workspace To Reduce Eye Strain

The American Optometric Association reports that over half of office workers who regularly use computers suffer from eye strain. You may not know it, but it’s not just caused by staring at your computer. The lighting surrounding your workspace could be making it worse. Here are some tips:

 

  • Reduce interior lighting: Most offices have harsh interior lighting that can contribute to eyestrain. If possible, use fewer light bulbs and fluorescent tubes.
  • Minimize glare: If there is a window directly in front or behind you, your eyes are working much harder than they need to be due to the glare and reflections on your computer screen. You can move or adjust your workstation, close the blinds, or get an anti-reflective coating on your glasses to reduce glare.
  • Adjust screen brightness: The blue light from the computer contributes to eye strain as well. Adjusting your brightness so it’s approximately the same as your surrounding workstation can help.

 

Improve The Lighting In Your Home

Remember when your parents used to tell you that reading in dim lighting will ruin your eyesight? While reading in the dark won’t do any lasting damage, it can give you a nasty headache. Doing any task that requires more intense focus in poor lighting can result in eye strain and all the uncomfortable symptoms that come with it.

Here’s a hint: take advantage of task lighting around your home. Desk lamps, reading lamps, under-cabinet lighting for kitchen work areas, among other types of task lighting, can help reduce your risk of eye strain when you’re doing near-work for longer amounts of time.

Good Lighting Is Even More Crucial For Those With Low Vision

In general, lighting needs to increase as you age. Research shows that a 60-year-old needs almost twice as much light to see as a 30-year-old!

Lighting is even more important for those with low vision. People with macular degeneration, glaucoma and other vision conditions should consult with their eye doctor about specific lighting improvements they can make in their homes to improve visibility.

See Things In A New Light
Believe it or not, small changes can make a big difference! The right kind of lighting can improve our reading ability, create a more noticeable difference in colors and prevent eye strain. Make some of these small changes and we promise, you’ll start seeing things in a whole new light!


Ocular and visual migraines: What’s the difference?

Visual disturbance caused by an ocular migraine

An ocular migraine is a rare condition characterized by temporary vision loss or even temporary blindness in one eye. Ocular migraines are caused by reduced blood flow or spasms of blood vessels in the retina or behind the eye.

In an ocular migraine, vision in the affected eye generally returns to normal within an hour. Ocular migraines can be painless or they can occur along with (or following) a migraine headache.

Unfortunately, the term “ocular migraine” is often used to describe a much more common (and harmless) condition — called a visual migraine or migraine aura — characterized by temporary visual disturbances that generally disappear within 30 minutes.

Unlike ocular migraines, a visual migraine typically affects both eyes.

Now let’s take a closer look at ocular migraines and visual migraines:

Ocular migraine and visual migraine symptoms

Ocular migraine symptoms generally include a small blind spot that affects your central vision in one eye. This blind spot gets larger, making it impossible for you to drive safely or read with the affected eye.

In some cases, the entire visual field of one eye may be affected. Generally, the episode lasts less than an hour.

Visual migraine symptoms can vary, and may include:

  1. A flickering blind spot in the center or near the center of your field of view
  2. A wavy or zigzag ring of colored light surrounding a central blind spot
  3. A blind spot that slowly migrates across your visual field
Visual migraines often appear suddenly and may create the sensation of looking through a cracked window. The visual migraine aura usually moves across your field of view and disappears within 30 minutes.

 

The symptoms of a visual migraine typically affect both eyes and last 30 minutes or less. A migraine headache may occur shortly after the symptoms of a visual migraine subside or no headache may occur.

If you’re experiencing a blind spot or other visual disturbance and you’re not sure if it’s an ocular migraine or a visual migraine, then cover one eye at a time. If the visual disturbance is occurring in just one eye, it’s likely that it’s an ocular migraine. If it affects both eyes, it’s probably a visual migraine.

But don’t take chances. If you suddenly experience any sort of blind spot in your field of vision, call or consult your optometrist  immediately to determine if it’s harmless or possibly a sign of something more serious, such as a retinal detachment.

What causes ocular and visual migraines?

Ocular migraines are believed to have the same causes as migraine headaches.

Migraine headaches have a genetic basis, and some studies say that up to 70 percent of people who suffer from the disorder have a family history of migraine headaches.

According to the World Health Organization, migraine headaches appear to be triggered by activation of a mechanism deep in the brain, which releases inflammatory substances around nerves and blood vessels in the head and brain.

Imaging studies have revealed changes in blood flow to the brain during ocular migraines and migraine auras. But why this happens and what brings about the spontaneous resolution of ocular migraines and visual migraines remain unknown.

Common migraine “triggers” that can cause a person to have a migraine attack (including ocular and visual migraines) include certain foods, such as aged cheeses, caffeinated drinks, red wine, smoked meats, and chocolate.

Food additives, such as monosodium glutamate (MSG), and artificial sweeteners also can trigger migraines in some people.

Other potential migraine triggers include cigarette smoke, perfumes and other strong odors, glaring or flickering lights, lack of sleep and emotional stress.

Treatment and prevention

As already noted, visual disturbances caused by ocular migraines and visual migraines typically disappear within an hour or less without treatment.

If you are performing tasks that require clear vision, when an ocular migraine or visual migraine occurs, stop what you are doing and relax until your vision returns to normal.

If you’re driving, park on the side of the road and wait for the vision disturbances to completely pass.

If you experience visual disturbances that are accompanied by a migraine headache, see your family physician or a neurologist for evaluation of your migraine episodes.

Your doctor can advise you on the latest medicines for treating migraines, including medicines designed to prevent future attacks.

It’s also a good idea to keep a journal of your diet and activities just prior to your ocular migraine or migraine aura episodes to see if you can identify possible triggers that you can avoid in the future.

If your ocular migraines or migraine auras (visual migraines) appear to be stress-related, you might be able to reduce the frequency of your migraine attacks without medicine by simply:

  • Eating healthful meals on a regular basis
  • Avoiding common migraine triggers
  • Getting plenty of sleep
  • Trying stress-busters such as yoga and massage

EXPERIENCING VISUAL DISTURBANCES? Don’t take chances. Contact us to discover what’s causing the visual disturbances.

Source: www.allaboutvision.com/conditions/ocular-migraine.htm

by Gary Heiting, OD


Eye’s cornea can resist infection from novel coronavirus

 

New findings from researchers at Washington University School of Medicine in St. Louis suggest the eye’s cornea can resist infection from the novel coronavirus. Although the herpes simplex virus can infect the cornea and spread to other parts of the body in patients with compromised immune systems, and Zika virus has been found in tears and corneal tissue, SARS-CoV-2, the virus that causes COVID-19, does not appear to replicate in the human cornea.

The researchers have yet to determine, however, whether other tissue in and around the cornea, such as the tear ducts and the conjunctiva, are vulnerable to the virus.

The new findings are published Nov. 3 in the journal Cell Reports.

“Our findings do not prove that all corneas are resistant,. But every donor cornea we tested was resistant to the novel coronavirus. It’s still possible a subset of people may have corneas that support growth of the virus, but none of the corneas we studied supported growth of SARS-CoV-2.”

Jonathan J. Miner, MD, PhD, First Author

Miner, an assistant professor of medicine, of molecular microbiology and of pathology and immunology, teamed up with ophthalmologist Rajendra S. Apte, MD, PhD, to study mouse and human corneas exposed to the herpes simplex, Zika and SARS-CoV-2 viruses.

“Some COVID-19 patients get eye symptoms, such as conjunctivitis (pinkeye), but it’s not clear that the viral infection itself causes that; it could be related to secondary inflammation,” said Apte, the Paul A. Cibis Distinguished Professor in the John F. Hardesty Department of Ophthalmology & Visual Sciences. “The cornea and conjunctiva are known to have receptors for the novel coronavirus, but in our studies, we found that the virus did not replicate in the cornea.”

Prior research in human and mouse corneal tissue had demonstrated that Zika virus could be shed in tears, and the researchers wanted to learn whether the cornea might serve as an entry point for SARS-CoV-2. Apte, Miner and their colleagues tested that by exposing the eye tissue to the different viruses and observing whether they could grow in and replicate. They also identified key substances in corneal tissue that can promote or inhibit viral growth.

One inhibitor they identified is called interferon lambda. They found that interferon lambda prevented efficient growth of Zika virus and herpes simplex virus in the cornea. But with SARS-CoV-2, levels of the substance had not effect on whether the virus could replicate. It simply could not gain a foothold whether interferon lambda was present or not.

That’s reassuring to Apte, also a professor of developmental biology and of medicine, who said it suggests COVID-19 probably cannot be transmitted through a cornea transplant or similar procedures in the eye.

“Our data suggest that the novel coronavirus does not seem to be able to penetrate the cornea,” Apte said.

Miner added, however, that because of unknowns involving the tear ducts and the conjunctiva, it’s too soon to dismiss the importance of eye protection.

“It’s important to respect what this virus is capable of and take appropriate precautions,” he said. “We may learn that eye coverings are not necessary to protect against infection in the general community, but our studies really are just the beginning. We need larger clinical studies to help us better understand all the potential routes of SARS-CoV-2 transmission, including the eye.”

Source:
Washington University School of Medicine

Journal reference:
Miner, J.J., et al. (2020) HSV-1 and Zika Virus but Not SARS-CoV-2 Replicate in the Human Cornea and Are Restricted by Corneal Type III Interferon. Cell Reports. doi.org/10.1016/j.celrep.2020.108339.


Presbyopia: Symptoms, causes and treatment

Presbyopia is the normal loss of near focusing ability that occurs with age. Most people begin to notice the effects of presbyopia sometime after age 40, when they start having trouble seeing small print clearly — including text messages on their phone.

You can’t escape presbyopia, even if you’ve never had a vision problem before. Even people who are short sighted will notice that their near vision blurs when they wear their usual spectacles or contact lenses to correct distance vision.

The eye’s lens stiffens with age, so it is less able to focus when you view something up close.

 

Researchers estimate that nearly 2 billion people worldwide have presbyopia.

Though presbyopia is a normal change in our eyes as we age, it often is a significant and emotional event because it’s a sign of ageing that’s impossible to ignore and difficult to hide.

In parts of the world where there is no access to vision care, presbyopia is much more than an inconvenience — it’s a leading cause of vision impairment that reduces people’s quality of life and productivity.

Presbyopia symptoms

When you become presbyopic, you either have to hold your mobile phone and other objects and reading material (books, magazines, menus, labels, etc.) further away from your eyes to see them more clearly.

Unfortunately, when we move things further away from our eyes they get smaller in size, so this is only a temporary and partially successful solution to presbyopia.

If you can still see close objects pretty well, presbyopia can cause headaches, eye strain and visual fatigue that makes reading and other near vision tasks less comfortable and more tiring.

What causes presbyopia?

Presbyopia is an age-related process. It is a gradual thickening and loss of flexibility of the natural lens inside your eye.

These age-related changes occur within the proteins in the lens, making the lens harder and less elastic over time. Age-related changes also take place in the muscle fibres surrounding the lens. With less elasticity, it gets difficult for the eyes to focus on close objects.

Presbyopia treatment

Presbyopia can be treated with spectacles (including reading glasses), contact lenses and vision surgery.

Spectacles

Spectacles with progressive lenses are the most popular solution for presbyopia for most people over age 40. These line-free multifocal lenses restore clear near vision and provide excellent vision at all distances.

Another presbyopia treatment option is spectacles with bifocal lenses, but bifocals provide a more limited range of vision for many people with presbyopia.

It’s also common for people with presbyopia to notice they are becoming more sensitive to light and glare due to ageing changes in their eyes. Photochromic lenses, which darken automatically in sunlight, are a good choice for this reason.

Reading glasses are another choice. Unlike bifocals and progressive lenses, which most people wear all day, reading glasses are worn only when needed to see close objects and small print more clearly.

If you wear contact lenses, your optician, can prescribe reading glasses that you wear while your contact lenses are in. You may purchase reading glasses at a retail shop, or you can get higher-quality versions prescribed by your optician.

Regardless which type of spectacles you choose to correct presbyopia, definitely consider lenses that include anti-reflective coating. Anti-reflective coating eliminates reflections that can be distracting and cause eye strain. It also helps reduce glare and increase visual clarity for night driving.

Contact lenses

People with presbyopia also can opt for multifocal contact lenses, available in gas permeable or soft lens materials.

Another type of contact lens correction for presbyopia is monovision, in which one eye wears a distance prescription, and the other wears a prescription for near vision. The brain learns to favour one eye or the other for different tasks.

While some people are delighted with this solution, others complain of reduced visual acuity and some loss of depth perception. Because the human eye changes as you grow older, your presbyopia glasses or contacts prescription will need to be increased over time as well. You can expect your optician to prescribe a stronger correction for near work as you need it.

Presbyopia surgery

If you don’t want to wear spectacles or contact lenses for presbyopia, a number of surgical options to treat presbyopia are available as well.

One presbyopia correction procedure that’s gaining popularity is implantation of a corneal inlay.

Typically implanted in the cornea of the eye that’s not your dominant eye, a corneal inlay increases depth of focus of the treated eye and reduces the need for reading glasses without significantly affecting the quality of your distance vision.

The first step to see if you are a good patient for presbyopia surgery is to have a comprehensive eye exam and a consultation with a refractive surgeon who specialises in the surgical correction of presbyopia.

Presbyopia is a part of growing older

Presbyopia is a normal part of the ageing process, and we’re all going to have to deal with it sometime after age 40. Whichever option you choose – spectacles, contact lenses or surgery – you’ll be able to easily read messages on your phone or a book to your granddaughter without any trouble.

If you are beginning to notice signs and symptoms of presbyopia, contact us for an eye exam and consultation regarding the best presbyopia treatment options for you.

Source: https://www.allaboutvision.com/en-gb/conditions/presbyopia/


Risks associated with eye-make up

Applying make-up is an everyday routine for millions of people worldwide. Even if a person only applies make-up once or twice a week, maintaining good make-up hygiene is essential in preventing skin irritations and serious eye infections.

How to practice good make-up hygiene

There are a number of simple but important steps that can help to prevent eye irritation and eye infections.

Renew your make-up every three months to reduce the risk of developing infections. This is particularly true in the case of eye make-up like mascaras or eyeliners. In some rare cases, women who have developed an eye infection from cosmetics have been temporarily or permanently blinded, according to the FDA. Some of these infections may stem from the make-up wands or brushes themselves.

 

Image Credit: Lucky Business / Shutterstock

Once a mascara wand or eyeliner brush comes into contact with the eyelashes, contamination of the applicator occurs as eyelashes naturally have bacteria on them. Over time, this contamination of both the brush and the container builds up and can lead to an increased risk of infection or allergic reactions. For this reason, sharing cosmetics is not advised at any time, as bacteria can harm another person even if the original user does not experience any reactions or infections themselves.

Fortunately, most people won’t experience any problems using make-up for longer than three months. If irritation does occur after using make-up products, it is essential to stop using the product immediately. If the irritation persists, medical attention should be sought.

Storing make-up products properly is also important. If cosmetics are stored in particularly hot conditions, for instance above 85°F (29°C), the preservatives in the products are at a higher risk of deteriorating.

Risks associated with eye-make up

It is important to remove make-up before sleeping. Ophthalmologist Dana Robaei published a case study in 2018 about a woman suffering from chronic foreign body sensation in both of her eyes. The article detailed the harmful effects that can occur after leaving mascara on overnight.

After examining the eyes, Robaei found subconjunctival mascara deposition beneath both eyelids. This was due to over 25 years of heavy mascara use without taking care to remove it properly. Small pieces of mascara had built up inside the eyelid and formed into solid concretions that were scratching the cornea, resulting in irritation and discomfort. The patient was left with permanent scarring on the cornea and on the eyelid after a surgical procedure to remove the built up concretions. Although Robaei clarifies it was a rare and extreme case, it nevertheless highlights the importance of removing eye make-up properly every night.

Other reports have been made about the risk of mascara-induced damage to the lacrimal drainage system, with one patient developing a dacryolith (a concretion usually comprising lipids, epithelial cells and other debris) loaded with mascara. Other reports in literature reviews on problems caused by mascara include eyelid dermatitis, infection keratitis, and mascaroma, among others.

Additionally, not all make-up applied to the eyes remains within the area of application. For instance, mascara can flake off and small particles travel into the eye, causing redness or irritation. In other cases, the eye can be scratched by make-up brushes or pencils that can then lead to serious eye infections. Ensuring that any applicator used near the eyes is clean can help to reduce the risk of scratch-induced infections. However, the trauma caused by scratches may still trigger problems or reactions.

Summary

As most make-up and cosmetic products undergo rigorous testing before being sold, the daily use of make-up is thought to pose minimal initial risk. It is when make-up is not removed properly, contaminated, or used when individual allergies are already apparent, that risks of infection, irritation and permanent damage to the application area increase.

A microbial study asked forty women to use one of two brands of non-waterproof mascara every day for three months. It was found that out of the 33 samples collected from the 40 women, microbial growth was present in over 36% of mascara containers.

As such, the need to practice good make-up hygiene is clear. Careful application of make-up around the eyes can reduce the risk of eye injury and subsequent irritation, infection, and loss of vision, in rare cases.

Sources

https://www.news-medical.net/health/Risks-Associated-with-Eye-Make-Up.aspx
http://www.scielo.br/pdf/abo/v79n6/0004-2749-abo-79-06-0411.pdf
journals.lww.com/…/…anifestations_of_Long_Term_Mascara_Use.29.aspx
https://wexnermedical.osu.edu/blog/eye-makeup-risks
https://www.aaojournal.org/article/S0161-6420(17)33788-0/fulltext
https://www.ajo.com/article/0002-9394(75)90798-9/pdf
www.sciencealert.com/mascara-make-up-remove-health-effects-dangerous-eyes
https://www.sciencedirect.com/science/article/pii/S1529183908003795


Eye spots, floaters and flashes

Vitreous detachment and floaters within the eye

Eye floaters are those tiny spots, specks, flecks and “cobwebs” that drift aimlessly around in your field of vision. While annoying, ordinary eye floaters and spots are very common and usually aren’t cause for alarm.

Floaters and spots typically appear when tiny pieces of the eye’s gel-like vitreous break loose within the inner back portion of the eye.

At birth and throughout childhood, the vitreous has a gel-like consistency. But as we age, the vitreous begins to dissolve and liquefy to create a watery centre.

Some undissolved gel particles occasionally will float around in the more liquid centre of the vitreous. These particles can take on many shapes and sizes to become what we refer to as “eye floaters.”

You’ll notice that these spots and eye floaters are particularly pronounced if you gaze at a clear or overcast sky or a computer screen with a white or light-coloured background. You won’t actually be able to see tiny bits of debris floating loose within your eye. Instead, shadows from these floaters are cast on the retina as light passes through the eye, and those tiny shadows are what you see.

You’ll also notice that these specks never seem to stay still when you try to focus on them. Floaters and spots move when your eye and the vitreous gel inside the eye moves, creating the impression that they are “drifting.”

When are eye floaters and flashes a medical emergency?

Noticing a few floaters from time to time is not a cause for concern. However, if you see a shower of floaters and spots, especially if they are accompanied by flashes of light, you should seek medical attention immediately from an optician.

The sudden appearance of these symptoms could mean that the vitreous is pulling away from your retina — a condition called posterior vitreous detachment.

Or it could mean that the retina itself is becoming dislodged from the back of the eye’s inner lining, which contains blood, nutrients and oxygen vital to healthy function. As the vitreous gel tugs on the delicate retina, it might cause a small tear or hole in it. When the retina is torn, vitreous can enter the opening and push the retina farther away from the inner lining of the back of the eye — leading to a retinal detachment.

A detached retina is a medical emergency that requires immediate treatment to prevent permanent vision loss. Treatment consists of surgery to reattach the retina to the back surface of the eyeball, reconnecting it to its source of blood, oxygen and other nutrients.

Posterior vitreous detachments (PVDs) are far more common than retinal detachments and often are not an emergency even when floaters appear suddenly. Some vitreous detachments also can damage the retina by tugging on it, leading to a tear or detachment of a portion of the retina.

What causes eye floaters and spots?

As mentioned above, PVDs are common causes of vitreous floaters, and retinal tears and detachments also can contribute to floaters and spots.

What leads to vitreous detachments in the first place?

As the eye develops, the vitreous gel fills the inside of the back of the eye and presses against the retina and attaches to the surface of the retina. Over time, the vitreous becomes more liquefied in the centre. This sometimes means that the central, more watery vitreous cannot support the weight of the heavier, more peripheral vitreous gel. The peripheral vitreous gel then collapses into the central, liquefied vitreous, detaching from the retina.

It’s estimated that more than half of all people will have a PVD by age 80. Thankfully, most of these vitreous detachments do not lead to a torn or detached retina.

Light flashes during this process mean that traction is being applied to your retina while the PVD takes place. Once the vitreous actually detaches from the retina this traction pressure is eased, and the light flashes should subside.

What causes eye flashes?

Ordinarily, light entering your eye stimulates the retina. This produces an electrical impulse, which the optic nerve transmits to the brain. The brain then interprets this impulse as light or some type of image.

If the retina is mechanically stimulated (physically touched or tugged), a similar electrical impulse is sent to the brain. This impulse is then interpreted as a flash or flicker of light called a photopsia.

When the retina is tugged, torn or detached from the back of the eye, a flash or flicker of light commonly is noticed. Depending on the extent of the traction, tear or detachment, these photopsias might be short-lived or continue indefinitely until the retina is repaired.

Photopsias also may occur after a blow to the head that is capable of shaking the vitreous gel inside the eye. When this occurs, the phenomenon sometimes is called “seeing stars.” In some cases, photopsias are associated with migraine headaches and ocular migraines.

Other conditions associated with eye floaters and flashes

When a PVD is accompanied by bleeding inside the eye (vitreous hemorrhage), it means the traction that occurred may have torn a small blood vessel in the retina.

A vitreous hemorrhage increases the possibility of a retinal tear or detachment. Traction exerted on the retina during a PVD also can lead to development of conditions such as macular holes or puckers.

Vitreous detachments with accompanying eye floaters also may occur in circumstances such as:

  • Inflammation in the eye’s interior
  • Short sightedness
  • Cataract surgery
  • YAG laser eye surgery
  • Diabetes (diabetic vitreopathy)
  • CMV retinitis

Inflammation associated with many conditions such as eye infections can cause the vitreous to liquefy, leading to a PVD.

When you are shortsighted, your eye’s elongated shape also can increase the likelihood of a PVD and accompanying traction on the retina. Shortsighted people also are more likely to have PVDs at a younger age.

PVDs are very common following cataract surgery and a follow-up procedure called a YAG laser capsulotomy.

Months or even years after cataract surgery, it’s not unusual for the thin membrane (or “capsule”) that’s left intact behind the interocular lens (IOL) to become cloudy, affecting vision. This delayed cataract surgery complication is called posterior capsular opacification (PCO).

In the capsulotomy procedure used to treat PCO, a special type of laser focuses energy onto the cloudy capsule, vaporising the central portion of it to create a clear path for light to reach the retina, which restores clear vision.

Manipulations of the eye during cataract surgery and YAG laser capsulotomy procedures cause traction that can lead to posterior vitreous detachments.

How to get rid of eye floaters

Most eye floaters and spots are harmless and merely annoying. Many will fade over time and become less bothersome. In most cases, no eye floaters treatment is required.

However, large persistent floaters can be very bothersome to some people, causing them to seek a way to get rid of eye floaters and spots drifting in their field of view.

But the risks of a virectomy usually outweigh the benefits for eye floater treatment. These risks include surgically induced retinal detachment and serious eye infections. On rare occasions, vitrectomy surgery can cause new or even more floaters. For these reasons, most eye surgeons do not recommend vitrectomy to treat eye floaters and spots.

Laser treatment for floaters

A relatively new laser procedure called laser vitreolysis has been introduced that is a much safer alternative to vitrectomy for eye floater treatment.

In this in-office procedure, a laser beam is projected into the eye through the pupil and is focused on large floaters, which breaks them apart and/or frequently vaporises them so they disappear or become much less bothersome.

To determine if you can benefit from laser vitreolysis to get rid of eye floaters, your optician will consider several factors, including your age, how quickly your symptoms started, what your floaters look like and where they are located.

Many floaters in patients younger than age 45 may be located too close to the retina and can’t be safely treated with laser vitreolysis. Patients with sizable eye floaters located farther away from the retina are better suited to the procedure.

An ophthalmologist who performs laser vitreolysis also will evaluate the shape and borders of your eye floaters. Those with “soft” borders often can be treated successfully. Likewise, sizable floaters that appear suddenly as a result of a posterior vitreous detachment often can be successfully treated with the laser procedure.

What happens during laser vitreolysis

Laser vitreolysis usually is pain-free and can be performed in an eye surgeon’s office. Just prior to the treatment, anesthetic eye drops are applied, and a special type of contact lens is placed on your eye. Then, the surgeon will look through a medical device and deliver the laser energy to the floaters being treated.

During the procedure, you might notice dark spots. These are pieces of broken up floaters. The treatment can take up to a half hour, but it’s usually significantly shorter.

At the end of the procedure, the contact lens is removed, your eye is rinsed with saline and the surgeon will apply an anti-inflammatory eye drop. Additional eye drops may be prescribed for you to use at home.

Sometimes, you may see small dark spots shortly after treatment. These are small gas bubbles that tend to resolve quickly. There also is a chance that you’ll have some mild discomfort, redness or blurry vision immediately after the procedure. These effects are common and typically won’t prevent you from returning to your normal activities immediately following laser vitreolysis.

If you are bothered by large, persistent eye floaters, ask your optician if laser vitreolysis might be a good treatment option for you.

Remember, a sudden appearance of a significant number of eye floaters, especially if they are accompanied by flashes of light or other vision disturbances, could indicate a detached retina or other serious problem in the eye. If you suddenly see new floaters, visit your optician without delay.

 

Source: allboutvision.com

By Marilyn Haddrill; contributions and review by Charles Slonim, MD


Could Glasses Protect Against COVID-19?

Wearing spectacles may lower your chances of contracting the coronavirus, according to a new study from Hubei Province, China. The findings appeared in JAMA Ophthalmology, a medical journal. But does this mean everyone should wear eye protection to prevent COVID-19? Not exactly, says ophthalmologist Thomas Steinemann, MD, clinical spokesperson for the American Academy of Ophthalmology and a professor of ophthalmology at MetroHealth Medical Center.

Ophthalmologists say there’s not enough information to recommend that people start wearing eye protection in addition to masks.

“It’s a provocative and fascinating study. But in the scheme of things, this is a small portion of the population. We’d require a much larger study before making any conclusions about whether wearing glasses really does mean people are touching their eyes less often, and therefore decreasing infection rates,” Dr. Steinemann said.

Coronavirus can spread through the eyes when an infected person coughs or sneezes near your eye or if you touch an infected object before touching your eye.

A possible link between spectacles and the coronavirus

The study came from a curious observation made by researchers in China. They noticed that very few of their sick patients wore glasses, which was remarkable since nearsightedness is common in China. They examined hospital records from patients with Covid-19 to learn more. Of 276 patients admitted to the hospital over a 47-day period, only 16 patients (5.8%) had myopia or nearsightedness that required them to wear glasses for more than eight hours a day.

Earlier research shows that more than 30% of people in the region needed glasses for nearsightedness.

Dr. Steinemann says it could be that glasses serve as a reminder to avoid touching your eyes. It may also be that glasses act as a partial barrier, protecting eyes from the splatter of a cough or sneeze. There are several factors other than wearing glasses that could explain the study’s finding. It could be that people who wear glasses tend to be older and more likely to stay home during the pandemic, compared with people who do not wear glasses. Or maybe people who can afford glasses in China are less likely to contract the virus because they can afford to live in less-crowded spaces.

Should you wear eye protection to prevent COVID-19?

While it’s too soon to say everyone should wear eye protection, Dr. Steinemann said that wearing goggles or face shields does make sense for frontline health care workers and people who care for those with the virus. For the rest of us, wearing a mask, frequent hand washing and practicing social distancing continue to be our best bet against the virus.

Source: www.aao.org/eye-health/news/eyeglasses-protect-against-covid-19-coronavirus


Eye Health and Diet

Healthy vision is important in ensuring quality of life. Two common threats to aging eyes are cataracts and age-related macular degeneration (AMD) which can, however, be prevented to some extent by a good diet.

Close up of the senile cataract during eye examination, senile cataract, mature cataract, neuclear sclerosis cataract. Image Credit: ARZTSAMUI / Shutterstock

 

Some important nutrients are found in common foods, and including them in the daily diet will help to preserve good vision throughout life. Antioxidants protect tissues from the toxic effects of free radicals which lead to a breakdown of cell membranes and nucleic acids. Free radicals are formed when tissue is exposed to ultraviolet radiation as from direct sunlight, in cigarette smoke, and other air pollutants. The retina is exposed to a lot of light and is therefore a prime spot for free radical damage, which makes it all the more important to provide antioxidants that reduce the high level of oxidative stress.

Specific Nutrients

Lutein and zeaxanthin: Found in spinach and kale, as well as other green leafy vegetables, and also eggs, these powerful antioxidants, which are typically found together in food, are known to reduce the risk of AMD as well as cataracts. They enter the retina and the lens and prevent degenerative changes, absorbing light frequencies such as blue and ultraviolet frequencies, which promote free radical formation, especially the vulnerable macular area. Other sources include kiwis, grapes, collard greens, and broccoli.

Lutein and zeaxanthin foods, info graphic food, fruit and vegetable icon vector. Image Credit: Plalek / Shutterstock

Vitamin C or ascorbic acid is found in fruits and vegetables, and may reduce the risk of cataracts. AMD may also be slowed if vitamin C and other nutritional factors are taken in combination. Vitamin C is found in grapefruit, strawberries, Brussels sprouts, ripe papayas, oranges, and green peppers.

Vitamin E or alpha-tocoferol is another powerful antioxidant found in nuts, sweet potatoes, and fortified cereals. It is also found in sunflower seeds, wheat germ oil, and vegetable oils.

Essential fatty acids: these fats are not synthesized in the human body but are required for the proper health and functioning of the nervous system, for energy metabolism and immunity. Among these, omega-3 fatty acids like DHA (docosahexaenoic acid) are vital for retinal function and for the development of vision, being concentrated in the outer parts of the photoreceptor cells. These are anti-inflammatory agents, which helps to prevent AMD. These fatty acids are found in salmon, herring and sardines, as well as tuna, halibut and flounder. Two servings or more a week are advised.

Zinc: this trace mineral is a cofactor in the transport of vitamin A from its storage site in the liver to the retina, where it is converted to melanin. This black pigment is essential in protecting retinal tissues against photodamage. High concentrations of zinc are present in the retina and the choroidal vascular tissue under the retina. Zinc is found in white meats from turkey, oysters, and crab meat, as well as eggs, peanuts, whole grains, and red meats.

Beta carotene which is found in all vegetables and fruits that are deep yellow or orange is part of the essential visual pigments, and its deficiency causes night blindness. Pumpkins, red peppers, kale, carrots, sweet potatoes and winter squash are all prime sources.

Supplements – Do They Play a Role?

AMD may be prevented or slowed using supplements made to AREDS standards. AREDS stands for the pivotal Age-Related Eye Disease Studies which tested the formula of this mix of antioxidants clinically. The current AREDS 2 version contains more lutein and zeaxanthin than before, which covers any dietary deficiency. Unlike many other supplements, it does not have beta-carotene and is therefore safe for smokers or those who have just quit. In this subgroup, this nutrient could cause a higher risk of lung cancer, though only at very high doses.

While no research suggests exactly how much of each of these nutrients is necessary to keep vision in good working order, the good old rule of five or more servings of colorful fruits and vegetables every day, with fish at least twice a week, seems to be most helpful in preventing eye problems with age.

Sources
www.aoa.org/…/diet-and-nutrition
www.health.harvard.edu/…/top-foods-to-help-protect-your-vision
https://www.health.ny.gov/publications/0911/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693724/
https://www.moorfields.nhs.uk/content/your-eye-health

Written by

Dr. Liji Thomas


What is astigmatism? What are correction options?

 

man experiencing eye strain

What is astigmatism?

Astigmatism is a type of refractive error caused by the irregularities in the shape of a person’s cornea. In this condition, the eye fails to focus the light equally on the retina leading to blurred or distorted vision. It can be present at the time of birth, or can develop gradually in life.

Astigmatism is a common eye condition which usually occurs with myopia (short-sightedness) or hyperopia (long-sightedness) and can be easily diagnosed with a simple eye exam.

Astigmatism is a refractive error and is not an eye disease or eye health issue.

Astigmatism is simply a problem with how the eye focuses light.

Astigmatism symptoms

Astigmatism usually causes vision to be blurred or distorted to some degree at all distances. Some of its symptoms are eye strain, headaches, squinting and eye irritation.

What causes astigmatism?

Astigmatism is usually caused by an irregularly shaped cornea. Instead of the cornea having a symmetrically round shape (like a football), it is shaped more like an egg (or rugby ball), with one meridian being significantly more curved than the meridian perpendicular to it.

(To understand what meridians are, think of the front of the eye like the face of a clock. A line connecting the 12 and 6 is one meridian; a line connecting the 3 and 9 is another.)

The steepest and flattest meridians of an eye with astigmatism are called the principal meridians.

In some cases, astigmatism is caused by the distortion of shape of the lens inside the eye. This is called lenticular astigmatism, to differentiate it from the more common corneal astigmatism.

It’s important to schedule an eye exam for your child to avoid vision problems in school from uncorrected astigmatism.

3 types of astigmatism
There are three primary types of astigmatism:

  • Myopic astigmatism.

One or both principal meridians of the eye are short sighted. (If both meridians are short sighted, they are myopic in differing degree.)

  • Hyperopic astigmatism.

One or both principal meridians are long sighted. (If both are long sighted, they are hyperopic in differing degree.)

  • Mixed astigmatism.

One prinicipal meridian is short sighted, and the other is long sighted.

Astigmatism is also classified as regular or irregular. In regular astigmatism, the principal meridians are 90 degrees apart (perpendicular to each other). In irregular astigmatism, the principal meridians are not perpendicular.

Most astigmatism is regular corneal astigmatism, which gives the front surface of the eye an oval shape.

Irregular astigmatism can result from an eye injury that has caused scarring on the cornea, from certain types of eye surgery or from keratoconus, a disease that causes a gradual thinning of the cornea.

Astigmatism tests

Astigmatism is detected during a routine eye exam with the same instruments and techniques used for the detection of short-sightedness and long-sightedness.

Your optician can estimate the amount of astigmatism you have by shining a light into your eye while manually introducing a series of lenses between the light and your eye. This test is called retinoscopy.

Astigmatism correction options

Astigmatism can usually be corrected with glasses or contact lenses.

Refractive surgery is one of the less common astigmatism correction options, however, since it is a laser procedure that changes the shape of your eyes, it comes with risks associated with most surgeries.

Astigmatism should be treated as soon as possible. Once diagnosed, regular visits to an optician are required as astigmatism can fluctuate over time, making it necessary for prescriptions to be modified.

Source: allaboutvision.com/en-gb/conditions/astigmatism/