The Brain and the Eye – How They Work Together

The Brain and the Eye

The eye works like a camera. The iris and the pupil control how much light to let into the back of the eye, much like the shutter of a camera. When it is very dark, our pupils get bigger, letting in more light; when it is very bright our irises constrict, letting in very little light.

The lens of the eye, like the lens of a camera, helps us to focus. But just as a camera uses mirrors and other mechanical devices to focus, we rely on eyeglasses and contact lenses to help us to see more clearly.

The focus light rays are then directed to the back of the eye, on to the retina, which acts like the film in a camera. The cells in the retina absorb and convert the light to electrochemical impulses which are transferred along the optic nerve to the brain. The brain is instrumental in helping us see as it translates the image into something we can understand.

The Brain and the Eye

The eye may be small, but it is one of the most amazing parts of your body. To better understand it, it helps to understand the different parts and what they do.

Choroid
A layer with blood vessels that lines the back of the eye and is between the retina (the inner light-sensitive layer that acts like film) and the sclera (the outer white part of the eyeball).

Ciliary Body
The muscle structure behind the iris, which focuses the lens.

Cornea
The very front of the eye that is clear to help focus light into the eye. Corrective laser surgery reshapes the cornea, changing the focus to increase sharpness and/or clarity.

Fovea
The center of the macula which provides the sharp vision.

Iris
The colored part of the eye used to regulate the amount of light entering the eye. Lens focuses light rays onto the retina at the back of the eye. The lens is transparent, and can deteriorate as we age, resulting in the need for reading glasses. Intraocular lenses are used to replace lenses clouded by cataracts.

Macula
The area in the center of retina that contains special light-sensitive cells, allowing us to see fine details clearly in the center of our visual field. The deterioration of the macula can be common as we age, resulting in age related macular degeneration.

Optic Nerve
A bundle of more than a million nerve fibers carrying visual messages from the retina to the brain. Your brain actually controls what you see, since it combines images. Also the images focused on the retina are upside down, so the brain turns images right side up. This reversal of the images Is a lot like what a mirror does in a camera. Glaucoma can result when increase pressure in the eye restricts the flow of impulses to the brain, causing optic nerve damage and makes it difficult to see.

Pupil
The dark center opening in the middle of the iris changes size to adjust for the amount of light available to focus on the retina.

Retina
The nerve layer lining the back of the eye that senses light and creates electrical impulses that are sent through the optic nerve to the brain.

Sclera
The white outer coating of the eyeball.

Vitreous Humor
The clear, gelatinous substance filling the central cavity of the eye.

3/3/16

Susan DeRemerSusan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

Understanding and Treating Corneal Scratches and Abrasions

Corneal Scratches and Abrasions

Call it a scratch, an abrasion or erosion; no matter how you describe it or what the cause, damage to the cornea most always causes pain.

So what exactly is the cornea and why can even a small scratch hurt so much? The cornea is the clear dome at the very the front of the eye. Its primary job is to surface the tears and with them, focus light into the eye. It then passes through the crystalline lens and on to the retina where it is transformed into electrical impulses that are ultimately transformed by the brain into sight.

Because vision is so essential for survival and the cornea so critical to seeing, it is among the most richly innervated and exquisitely sensitive of all tissues. Even the smallest piece of dust that finds its way into the eye and touches the cornea can cause significant discomfort, irritation and copious tearing in an attempt to wash it away. A healthy cornea is transparent and consists of several layers that give the cornea its smooth dome like shape. The outermost layer, the epithelium, is designed to break away to protect the delicate deeper layers if scratched or abraded.
cornea layers - corneal scratches and abrasions

Looking For the Cause

The most common causes of corneal scratches are accidents. Tiny infant fingers and fingernails are a common cause of abrasions in young parents, tree branches are a frequent source of abrasions in hikers and lovers of the outdoors, and makeup brushes are a typical cause in women. Scratches can also be caused by foreign objects that get into the eye and then work their way on to the inside of the upper lid – causing a scratch that occurs with each blink. That’s why its important to carefully investigate the cause of every corneal scratch.

A scratch pr abrasion usually produces near instantaneous pain and tearing as the eye tries to wash away the irritant. Light sensitivity soon follows and can be so intense that the eye can involuntarily shut. This is actually nature’s way of “patching” the eye to facilitate healing.

To confirm you have a scratched cornea, a doctor or other health care professional will often apply a wetted fluorescein strip to the inside lid or white of the eye. Fluorescein is a dye that glows bright green when exposed to black light. The dye is absorbed by damaged areas, clearly showing the area if the scratch or abrasion.

Getting On the Mend

The good news is that most scratches will rapidly heal on their own, especially smaller and more superficial ones. The confocal microscope, a high tech device that provides extreme magnification views of living tissue, has been used to observe corneal healing in real time. The video captures are breathtaking as individual corneal cells can be seen literally stretching over each other to mend and seal the corneal surface.

If an abrasion is larger or deeper it may require patching to help healing. The traditional eye patch applied with tape to keep the eye shut has largely been replaced by the bandage contact lens which is far more comfortable and allows some vision and easier observation during follow up examination. It also allows medication to be applied if needed. Because there is a risk of infection whenever the outer boundaries of the body are breached, topical antibiotics are often used as a precaution in treating scratches of the cornea and ocular surface.

Most commonly the cornea heals quickly and completely, but not always. In rare cases damaged areas of the cornea may not heal fully, leaving the outer layers of the cornea susceptible to coming off again for no apparent reason. This is thought to be more common after scratches caused by organic material such as a tree branch. Called recurrent corneal erosions, they often occur during sleep waking the person with a sudden sharp pain and excessive tearing. There are a variety of treatments for recurrent corneal erosion.

Conclusion

Most people will sooner or later experience a scratched cornea. Most scratches will be minor and will resolve with minimal treatment. However, some can be serious and have significant consequences. The best way to avoid problems is to be aware that they can occur and take measures to protect the eyes in situations where the risk of eye trauma is higher. This includes: wearing safety glasses while working with power tools, or sports where eye contact is possible. This includes cycling and sport shooting.

Be aware of active infants with little fingers that seem to have a magnetic attraction of their parents eyes. If you use eye makeup, leave enough time to properly apply it without rushing and potentially scratching your cornea in the process.

Finally, if you experience a scratched cornea and the pain doesn’t rapidly abate, see an eyecare specialist. Urgent care centers are fine for most things, but when it comes to the eyes finding a knowledgeable eye care professional is wise.

2/10/15

AArthur B. Epstein, OD, FAAO
co-founder of Phoenix Eye Care
and the Dry Eye Center of Arizona
Fellow of the American Academy of Optometry
American Board of Certification in Medical Optometry
Chief Medical Editor of Optometric Physician™

Cataract Surgery and Keratoconus

1/8/15

The eye works like a camera, specifically a digital camera. There is the front lens of the camera (cornea), the aperture (iris), the film (retina), and a cable to take the image to the brain (optic nerve). This “camera” also has an additional lens – the natural crystalline lens, which lies behind iris. This natural lens is flexible when we are young, allowing us to focus at distance then instantaneously up close. Around age 40-45, this natural lens starts to stiffen, necessitating the need for reading glasses for most people. This stiffening is the beginning of the aging process that eventually leads to formation of a cataract. We refer to the lens as a cataract when it becomes sufficiently cloudy to affect ones quality of vision.cataract surgery and keratoconus-Cataract diagram In general, cataract surgery is one of the safest and most successful of all surgeries performed. The basics of cataract surgery in eyes with keratoconus is very similar to non-keratoconic eyes.

Keratoconus (KC) affects this “camera” by causing the front lens (cornea) to bulge. This causes the optics to be distorted. In many cases, this can be corrected for with hard contact lenses (CL) or spectacles; in other cases a corneal transplant may be necessary. When it comes time for cataract surgery in the setting of KC, there are several factors that need to be considered.

Corneal Stability
The first thing to be considered is the stability of your cornea. In general, KC progresses more in your late teens to early twenties, and then stabilizes with age. A very exciting treatment for KC is collagen crosslinking. This treatment is meant to stiffen the cornea to prevent instability that is inherent to KC. This treatment promises to stop the progression of KC at a young age. Fortunately, with age, the cornea naturally crosslinks and stiffens, therefore when it comes time for cataract surgery, there is little chance of the progression of KC. Your doctor needs to choose the appropriate intraocular lens (IOL) to refocus your eye after surgery. Two of the most important factors in IOL selection are the length of your eye and the shape of your cornea. Long term CL wear can mold your cornea. It is important to assure that you stay out of your CLs long enough for your cornea to reach its natural shape. Depending on how long you have worn your CLs, it may take several months for the cornea to stabilize. This time can be challenging as your vision will be suboptimal (because you can’t wear CLs), and will be changing (as your cornea reaches its natural shape). When your cornea does stabilize, it is important to determine whether the topography (shape) is regular or irregular. This “regularity” is also known as astigmatism. If the astigmatism is regular, light is focused as a line – generally, this distortion can be fixed with glasses. However, if the astigmatism is irregular, light cannot be focused with glasses, and hard CLs are needed to provide optimal focusing. If you have had a corneal transplant, I generally recommend all your sutures to be removed to allow your new cornea to reach its natural shape.

IOL Selection
The second thing to be considered is the type of IOL. IOLs allow your doctor to refocus the optics of your eye after surgery. In many cases, the correct choice of IOL may decrease your dependence on glasses or CLs. There are several factors that are important when considering the correct IOL for a keratoconic patient. The amount and regularity of your astigmatism plays a very significant role in IOL selection. In general, there are four types of IOLs available in the US – monofocal, toric, pseudo-accomodating, and multifocal. In general I do not recommend multifocal IOLs in patients with KC. These IOLs allow for spectacle independence by spitting the light energy for distance and near, however, with an aberrated cornea (which is what happens in KC), these IOLs do not fare well. If there is a low amount of regular astigmatism or irregular astigmatism, your best bet is a monofocal IOL. This is the “standard” IOL that is covered by your health insurance. If you have higher amounts of astigmatism that your doctor determines is mostly regular, you may benefit from a toric (astigmatism-correcting) IOL. These IOLs can significant improve your uncorrected vision and really decrease your dependence on glasses. It is important to realize that monofocal and toric IOLs only correct vision at one distance. With a monofocal IOL you still can wear a CL to fine-tune your vision, however, with a toric IOL, in general you will need glasses for any residual error. There is a pseudo-accomodating toric IOL available, and this may be a good option if you are trying to decrease your dependence on glasses and correct some of your astigmatism. These IOLs are relatively new to the US market.

If You Had A Corneal Transplant
In the setting of a corneal transplant many of the same factors need to be considered – stability of the graft, choice of IOL, etc. In addition, the health of the graft has to be judged. Prior to cataract surgery in my patients with corneal transplants, I make sure to remove all of their sutures and give the cornea time to stabilize (just as if they were a CTL wearer). If you are a CL wearer, the same rule of being out of the TL until the topography is stable applies. The health of a transplant needs to be established prior to undergoing cataract surgery. The cornea has five main layers to it –cataract surgery and keratoconus-corneal structure the back layer (inside) is called the endothelium. This layer is responsible for “pumping” fluid out of the cornea, allowing it to stay clear. In all eyes there is a loss of endothelium cells with cataract surgery. I generally perform a “specular microscopy,” which allows me to visualize and quantify the corneal endothelium prior to surgery. This allows me to risk stratify you before your surgery. It is important to realize that corneal transplants have a lifespan and may have to be repeated in the future.

Keep in mind, there is some uncertainty in biometry (the process of selecting an IOL) in all eyes – this error can be higher in keratoconic eyes. This highlights why assuring stability is important. Equally important is picking the correct IOL for your situation. Also, keep in mind that I have discussed generalities in this article. Your individual case could be different. This is a conversation best left between you and your surgeon. In general, cataract surgery and keratoconus or a corneal transplant can be a very safe and effective way in restoring vision.

Sam Garg, MDSumit (Sam) Garg, MD
Interim Chair of Clinical Ophthalmology and Medical Director
Gavin Herbert Eye Institute at the University of California, Irvine

The Way Eyes Work

9/16/14

Eyes are an amazing part of your body and not just because of what they do helping you see. The are also fascinating be because of the way eyes work. Here are 20 facts about how your eyes function.
Colorful eye - the way eyes work

      1. The pupil dilates 45% when looking at something pleasant.

2. An eye’s lens is quicker than a camera’s.

3. Each eye contains 107 million cells that are light sensitive.

4. The light sensitivity of rod cells is about 1,000 times that of cone cells.

5. While it takes some time for most parts of your body to warm up their full potential, your eyes are always active.

6. Each of your eyes has a small blind spot in the back of the retina where the optic nerve attaches. You don’t notice the hole in your vision because your eyes work together to fill in each other’s blind spot.

7. The human eye can only make smooth motions if it’s actually tracking a moving object.

8. People generally read 25% slower from a computer screen compared to paper.

9. The eyes can process about 36,000 bits of information each hour.

10. Your eye will focus on about 50 things per second.

11. Eyes use about 65% or your brainpower – more than any other part of your body.

12. Images that are sent to your brain are actually backwards and upside down.

13. Your brain has to interpret the signals your eyes send in order for you to see. Optical illusions occur when your eyes and brain can’t agree.optical illusion - the way eyes work

14. Your pupils can change in diameter from 1 to 8 millimeters, about the size of a chickpea.

15. You see with your brain, not your eyes. Our eyes function like a camera, capturing light and sending data back to the brain.

16. We have two eyeballs in order to give us depth perception – comparing two images allows us to determine how far away an object is from us.

17. It is reported that men can read fine print better than women can.

18. The muscles in the eye are 100 times stronger than they need to be to perform their function.

19. Everyone has one eye that is slightly stronger than the other.

20. In the right conditions and lighting, humans can see the light of a candle from 14 miles away.

Susan DeRemerSusan DeRemer. CFRE
Vice President of Development
Discovery Eye Foundation

Pediatric Contact Lenses

8/14/14

Because August is Children’s Eye Health Month we are pleased to present a four-part series on pediatric vision issues and contact lenses by Buddy Russell, FCLSA, COMT. With over thirty years experience fitting contact lenses, Buddy is currently an associate of the specialty contact lens service at Emory University Eye Center in Atlanta, Georgia. Buddy is a clinical instructor in Emory’s Ophthalmic Technology Program and teaches students and ophthalmology resident’s contact lens technology. 

Child refractive exam - pediatric contact lensesHe is a licensed dispensing optician, a Fellow member of CLSA and has been certified by JCAHPO as a Certified Ophthalmic Medical Technologist. He lectures at national and international meetings on contact lens related topics. Buddy has written articles for a number of publications, two chapters for CLSA’s advanced training manual and is a peer reviewer for the Cornea publication. He is also a contributing editor for CLSA’s Eyewitness journal. His current areas of research include pediatric aphakia and keratoconus. He joined the faculty at TVCI in 2006.

The first article will examine that pediatric contact lenses for children go beyond vision correction, the second will explore lenses as a treatment option, the third will look at a variety pediatric eye conditions and the final post will discuss the contact lens fitting challenges you face when you work with children.

Introduction

Working with the pediatric patient and their caregivers / family can be challenging, rewarding, fun, and yet sometimes frustrating. Many of these cases often include factors that are unique to the young patient. In addition to the technical challenges of obtaining the objective data, the fear of uncertainty is often present. The uncertainty of the unknown can either paralyze you or motivate you to step up and simply do what must be done.

The Definition May Vary

The definition of pediatric contact lens fitting can be different to different people. The fitter who works with the occasional twelve-year-old neophyte wearer will define pediatric fitting different from the person that works with babies on a routine basis. Pediatrics is generally defined as a branch of medical care that deals with infants, children and adolescents. The word pediatrics is derived from two Greek words (pais = child and iatros = healer), which means healer of children. Are you a “healer of children” or do you tend to feel better about someone else assuming the challenge and responsibility? This article will discuss some of the conditions, contact lens indications, fitting techniques and challenges that are present with the young patient.

Refractive Indications

What age is “appropriate “ to fit a contact lens on a child? In the absence of a medical indication, Jeff Walline, OD and his colleagues have addressed the answer to this question in the published literature. In addition, the American Academy of Optometry published a position paper in 2004 that stated that by the age of eight, a child was able to handle contact lenses and assume some degree of responsibility. We are all aware that not all eight year olds are capable of dealing with contact lenses. For that matter, not all eighteen year olds are mature enough to assume responsibility for anything. Some of the concerns that a contact lens practitioner may have in fitting these young children include the risk of safety to the child’s health, too much chair time, physical limitations, lack of hygiene, and lack of maturity. These are all legitimate concerns when you consider the child can see well with spectacles.

What does the literature reveal concerning these questions and concerns? Are the answers there?

CLIP Study

The Contact Lens In Pediatrics study compared 169 neophyte wearers in two age groups (children age 8-12 and teens age 13-17) over a period of three months. The summary of the clinical findings in the publication is that adverse events was low and the younger children took a little longer to train application and removal of the contact lenses. The more impressive outcomes from this study was determined by a tool used more frequently in child psychology referred to as the Pediatric Refractive Error Profile (PREP) survey. The PREP survey is a clinically validated quality of life instrument to assess how a child “sees” him or herself. This 26-question survey revealed that contact lenses improved the child’s self image in regards to their appearance, increased confidence in themselves while participating in activities and overall satisfaction of their form of vision correction. These findings were consistent in both age groups. More than 80% of both age groups found contact lenses easy to clean and take care of as all participants were fitted with 2-week disposable soft lenses and used a multipurpose disinfection care system.

The ACHIEVE Study

The Adolescent and Child Health Initiative to Encourage Vision Empowerment (ACHIEVE) were published in 2009. Jeff Walline, OD and his colleagues designed this study to find out the effects that glasses and contacts had on the self-perception of the child. This study examined 484 myopic children 8-11 years. The participants were randomized to spectacles (n=237) or contact lenses (n=247) and followed for three years. The children were evaluated at baseline, 1 month and every 6 months for three years by a validated psychology tool for self-perception referred to as the Self-Perception Profile for Children (SPPC). The SPPC instrument allows a 4 point self-assessment in 6 categories; scholastic competence, social acceptance, athletic competence, physical appearance, behavioral conduct and global self-worth. The participants revealed the most dramatic areas of improvement with contact lenses compared to spectacles in the areas of physical appearance, athletic competence, scholastic competence and social acceptance. Similar to the low occurrence of adverse events with contact lens wear found in the CLIP study, over the three year period there were only 13 adverse events among 9 subjects. In addition, the ACHIEVE study found very similar rates of myopic progression in both groups of patients over the three year period (1.08D spectacle group and 1.27D contact lens group).
What can we conclude from these two studies?

One is that we are in a position to not only help a young person see but we are also in a position to do it safely and assist the child by instilling more confidence in themselves at a young age that may impact them as they mature into an adult who feels good about themselves. Young children are accustomed to following rules. When properly trained, these same young patients may grow into some of the most compliant patients that we have in our practice. There are some practical considerations for prescribing contact lenses to the younger patient. Mary Lou French, O.D. has stated the three M’s are important for success; Maturity (good hygiene, good communication skills, signs of responsibility), Motivation (why do they want contacts? Does the child want them or just the mom or dad? Are they active in activities where freedom from spectacles is important?), Mom (is the mom / dad / older sibling willing to help?). Don’t let age be the deciding factor. Consider your position as one that may positively impact the young patient in how they “see” and feel about themselves.

Buddy Russell - pediatric contact lensesBuddy Russell, FCLSA, COMT
Associate, Specialty Contact Lens Service
Emory University Eye Center

What You Need to Know About Cataracts

6/5/14

Do you feel like your vision is getting worse? Do you feel like colors are not as vibrant as they used to be? Are you having more trouble with glare? If you have any of these symptoms, you may be experiencing the effects of cataracts.

Cataracts are a normal aging process of the crystalline lens in the eye. Well you may ask — what is the crystalline lens? It is easiest to think of the eye as a camera. The eye has a lens (actually two) – the cornea (the front window of the eye) and the crystalline lens (inside the eye). It also has an aperture (the colored iris), and film (the retina). All these structures work together to focus light and allow us to see – just like a camera. When we are young (less than 40), the crystalline lens is flexible. This is why we are able to see distance and then near without the need for reading glasses. The crystalline lens is able to change its shape depending on where one is looking.

Figure 1 – Slit-lamp photo of a visually significant cataract.
Figure 1 – Slit-lamp photo of a visually significant cataract.

As we age, the crystalline lens becomes less flexible, thereby causing one’s near vision to be more blurry. This necessitates the need for reading glasses. As the crystalline lens become less flexible with age, the lens also starts to become more yellow and can also become cloudy. When the yellowing and/or clouding become visually significant, we refer to this as a cataract (figure 1).

Are cataracts dangerous? The simple answer is no. In the vast majority of cases, a cataract can be monitored until it becomes visually significant (drop in vision, glare, decreased contrast, vision related difficulties with day to day activities, etc). However, there are a few instances in which cataract removal is a medical necessity. Routine examinations by your eyecare provider can help you determine if you are at risk for these less common instances.

Figure 2 – Intraoperative photo during cataract surgery (prior to cataract removal).
Figure 2 – Intraoperative photo during cataract surgery (prior to cataract removal).

What can I expect during cataract surgery? Do you have to replace the crystalline lens with anything? Cataract surgery involves removing the clouded crystalline lens (figure 2) and replacing it with an artificial lens known as an intraocular lens (IOL) (figure 3). Surgery generally takes 10-15 minutes under a mild sedative, and you don’t have to stop any of your current medications. Anesthesia is achieved with drops and you will only feel mild pressure during the surgery. IOLs come in different styles – Standard IOLs grossly correct your vision and you can fine tune your vision (distance and near) with glasses post-operatively;

Figure 3 – Intraoperative photo during cataract surgery (after implantation of an IOL).
Figure 3 – Intraoperative photo during cataract surgery (after implantation of an IOL).

Toric (astigmatism correcting) IOLs allow for increased spectacle independence, but glasses will still be needed for distance or near; Accommodating IOLs “flex” within the eye to decrease your dependence on distance and near glasses; Multifocal IOLs allow spectacle independence for distance and near. I always counsel patients that there is no perfect IOL and you have to determine which IOL is best for your particular situation. Your doctor can help you decide which IOL is best for you. Generally, cataract surgery is extremely safe. Your doctor will discuss particular risks specific to your eye.

How do I know if cataract surgery is right for me? The best way to know if you have a cataract and if it time to consider surgery is to consult with your local ophthalmologist. If you have experienced a recent drop in vision, that is not correctable with glasses, cataract surgery may be able to restore your vision!

Garg feb 2014 thumbSumit “Sam“ Garg, MD
Medical Director
Vice Chair of Clinical Ophthalmology
Assistant Professor of Ophthalmology
Gavin Herbert Eye Institute – UC, Irvine

New Hope for Corneal Scarring

5/22/14

There are several etiologies for limbal stem cell deficiency of the front of the eye. These include chemical and thermal burns, Steven-Johnson syndrome (which is an autoimmune severe allergic reaction that causes a burn from within), congenital aniridia, and a few other insults such as contact lens over-wear. All of these cause severe ocular surface scarring and problems with the cornea. Many eyes with these diseases have problems with corneal healing. They do not have the stem cells to support ocular surface health. The scarring can be so severe in many cases that severe corneal blindness can result.

Limbal stem cells from the human cornea, with a protein known as p63 stained yellow. Cell nuclei (which hold the DNA) are stained red.  From eurostemcell.org
Limbal stem cells from the human cornea, with a protein known as p63 stained yellow. Cell nuclei (which hold the DNA) are stained red. From eurostemcell.org

In these cases, a simple corneal transplant will quickly fail and not result in any visual improvement. The reason for this is that the stem cells of the ocular surface have been damaged or burned out.

Visual rehabilitation for these eyes usually requires a limbal-corneal stem cell transplantation. The stem cells can be taken from the other healthy eye of the same patient, a living related donor, and or cadaveric tissue. In most cases systemic immunosuppression medications need to be taken for 1 to 3 years following surgery in order to minimize risk of rejection. Management of these patients is done in conjunction with an immunologist or a transplant specialist who can co-manage and monitor for systemic toxicity while the patient is on the these immunosuppressive medications. As most of these eyes also have concomitant glaucoma and scarring of the eyelids to the globe, co-management with a glaucoma specialist and an oculoplastic specialist is also required.

For patients who cannot be on systemic immunosuppression for other health reasons such as diabetes or cancer, they may require an artificial corneal transplantation. The artificial corneal transplantation is reserved as a last step for visual rehabilitation in these eyes. The only artificial cornea that has shown potential, is the Boston keratoprosthesis. Even this artificial cornea carries a high risk for infection and glaucoma. Very close monitoring of eyes that have an artificial cornea is required to monitor for infection and glaucoma progression. However these eyes do not require systemic immunosuppression.

Eye with Boston keratoprosthesis
Eye with Boston keratoprosthesis


The management of eyes with severe ocular surface disease is a difficult one for the cornea specialist. A subspecialist in severe ocular surface disease and limbal stem cell transplantation is required to manage these very sick eyes. At the Gavin Herbert Eye Institute, we have developed a team approach for the management of severe ocular surface disease patients and have successfully treated and are managing many patients who have otherwise no place to go.

Farid 3.6.14Marjan Farid, MD
Director of Cornea, Cataract, and Refractive Surgery
Vice-Chair of Ophthalmic Faculty
Director of the Cornea Fellowship Program
Associate Professor of Ophthalmology
Gavin Herbert Eye Institute, University of California, Irvine

New Technology for Evaluating Contact Lenses

5/1/14

Successful management with contact lenses can sometimes be a frustrating process for those with keratoconus. The fitting and evaluation process involves numerous visits to the optometrist, out of pocket expenses as well as medical insurance co-pays. Luckily, the contact lens industry has responded to the need to have better contact lens materials for patients with keratoconus. It used to be that the only contact lenses available to manage keratoconus were gas-permeable (GP) lenses. Now, more and more patients are being fit with newer generation hybrid lenses (GP lens core with a skirt of soft lens material to aid in fit and comfort) and scleral lenses (large diameter GP lenses that do not rest on the cornea, only the outlying sclera). These newer designs are intended to vault over the central cornea and do not rest on the cornea at all. They have resulted in much more comfortable and wearable strategies for full-time use. As a result of the newer lens designs, the game has changed when it comes to the science of fitting and evaluating the lenses.

For years, optometrists have used corneal topography to guide their decision making on fitting keratoconic eyes. A corneal topographer is an instrument that maps the shape of the cornea, and gives information much like that of a topographical map for hiking. Corneal topography is still an absolutely mandatory part of evaluating the shape of the cone, the simulated corneal curvature, and monitoring for progression of the disease, and is not a standard part of a typical eye examination. However, doctors have a new tool at their disposal for fitting contact lenses on patients with keratoconus.

Optical Coherence Tomography (OCT) was once reserved for use in the back of the eye, or retina. OCT uses visible light passed through the clear structures of the eye to generate a cross-sectional image of the layers of the retina, much like an image generated by an MRI. Advances in OCT technology has improved the resolution to image the eye on the micrometer scale (one-thousandth of a millimeter). OCT technology is now commercially available not only for the retina, but the structures of the front part of the eye. The obvious application is to aid the doctor in the fitting and evaluating complex contact lenses that vault the cornea.

Figure 1.  OCT image of a scleral lens fit on a keratoconic patient.  The cornea is the opaque white band located at the bottom of this picture, the tear film reservoir is the middle clear band and the contact lens is the top band.  Using an electronic caliper tool, the precise amount of vault can be measured, leaving no doubt as to the precision of the fit.
Figure 1. OCT image of a scleral lens fit on a keratoconic patient. The cornea is the opaque white band located at the bottom of this picture, the tear film reservoir is the middle clear band and the contact lens is the top band. Using an electronic caliper tool, the precise amount of vault can be measured, leaving no doubt as to the precision of the fit.

OCT allows the optometrist to view a cross-sectional image of the contact lens on the eye in real time and to monitor the health of the cornea in the presence of the contact lens. This view is valuable for judging the vault of new designs of contact lenses over the cornea and judging where the lenses land on the eye. It is the most specific way to determine if the fit is acceptable and to troubleshoot if lenses are not fitting appropriately.

Figure 2.  OCT image of the periphery of a scleral lens on a patient with pellucid marginal degeneration.  The lens contacts the cornea over an area of 0.87mm long.  These types of measurements help guide decision making in modifying the lens fit and were impossible before the advent of this technology.
Figure 2. OCT image of the periphery of a scleral lens on a patient with pellucid marginal degeneration. The lens contacts the cornea over an area of 0.87mm long. These types of measurements help guide decision making in modifying the lens fit and were impossible before the advent of this technology.
Figure 3.  Hybrid lens on a highly irregular eye after corneal transplant.  The point of contact of the soft skirt with the cornea is visible to the right of the image.
Figure 3. Hybrid lens on a highly irregular eye after corneal transplant. The point of contact of the soft skirt with the cornea is visible to the right of the image.

Optometrists now have a much more powerful tool for evaluating and managing even the most challenging contact lens fits. It remains to be seen whether this technology has the ability to reduce the number of visits required for successful fit. But, the precision afforded by this technology does have the ability to improve patient outcomes.

Sonsino HeadshotJeffrey Sonsino, OD, FAAO
The Contact Lens Center at Optique Diplomate
Cornea, Contact Lens, and Refractive Therapies

The Evolving Contact Lens

4/22/14

Contact lenses give a person the ability to see without glasses. If you have keratoconus, they are essential for seeing as regular glasses don’t work with an irregularly shaped cornea. But lately these relatively simple lenses have created a whole new world where they can dispense eye medication, measure blood glucose levels and even help the blind see.

Courtesy Google
Courtesy Google

Monitoring Blood Sugar
You have heard about Google Glasses, but Google is looking beyond the smartphones of eye wear to monitoring health. They are currently working on a lens with tiny wireless chips and glucose sensors that are sandwiched between two lenses. They would monitor glucose levels once a second and use tiny LED lights, also inside the lenses, to flash when the levels are too high or low. And how big are these electronics? They are no larger than a speck of glitter, with a wireless antenna that is thinner than a human hair. While they are still in development – Google has run clinical research studies and is in discussions with the FDA – it could make blood sugar monitor far less invasive than pricking your finger several times a day.

Drug Delivery for Glaucoma
Getting glaucoma patients to regularly use their eye drops to regulate the pressure in their eyes has always been a problem. They forget, don’t want to be bothered, or have a hard time getting the drops into their eyes. This could change with two research projects exploring the use of contact lenses to deliver medication over a prolonged period of time.

Researchers at Massachusetts Eye and Ear/Harvard Medical School Department of Ophthalmology, Boston Children’s Hospital, and the Massachusetts Institute of Technology who are working on a lens designed with a clear central area and a drug-polymer film made with the glaucoma drug latanoprost, around the edge to control the drug release. These lenses can be made with no refractive power or the ability to correct the refractive error in nearsighted or farsighted eyes.

Another team from University of California, Los Angeles have combined glaucoma medication timolol maleate with nanodiamonds and embedded them into contact lenses. When the drugs interact with the patient’s tears, the drugs are released into the eye. While the nanodiamonds strengthen the lens, there is no difference in water content so they would be comfortable to wear and allow oxygen levels to reach the eye.

Seeing in the Dark
Researchers out of the University of Michigan have developed an infrared sensor that could eventually be used in the production of night vision contact lenses. Thanks to graphene, a tightly-packed layer of carbon atoms, scientists were able to create a super-thin sensor that can be stacked on a contact lens or integrated with a cell phone.

Stem Cells for Cornea Damage
Researchers in Australia are working on a way to treat corneal damage with stem cell infused contact lenses. Stem cells were taken from the subject’s good eye and then plated them onto contact lenses (if there is a defect in both eyes, stem cells are taken from a different part of the eye). After wearing for about two weeks the subjects reported a significant increase in sight.
Braille-Tracile-Contacts
Helping the Blind See
And what good are contact lenses if you are blind? At Bar Ilan University in Israel researchers are creating special lenses that translate images into sensations felt on the eye. It works by taking an image with a smartphone or camera, it is then processed and sent to the contact lens. The custom-made lens is fitted with a series of electrodes that use small electric impulses to relay shapes onto the cornea, similar to braille. After some practice, test subjects were able to identify specific objects.

In expanding the uses of contact lenses, these projects seem to be just the beginning, all reported in the first four months of this year. Researchers and developers are working together to find more and better ways help with vision and medical issues, using contact lenses.

Susan DeRemerSusan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

Wavefront Sensing Applied to Custom Contact Lens Research in Keratoconus

4/10/14

During a trip to the optometrist or ophthalmologist, a patient will encounter the process of subjective refraction.  This technique involves the clinician asking the patient to make a series of judgments (which is better, one or two?) about the clarity of their vision when looking through a series of lenses.  The choices that the patient makes guide the clinician in identifying an optical prescription which is typically made up of sphere, and potentially, cylinder lenses.

Why is it that glasses don’t always work for patients with keratoconus?

In many instances, individuals with keratoconus do not achieve excellent visual performance with spectacles or traditional soft contact lenses.  One cause for the failure of these corrections is that the changes in corneal shape that accompany keratoconus induce refractive errors which traditional spectacles simply cannot correct.  So, even when sphere and cylinder in the keratoconic eye are well-corrected, these “other refractive errors” or “other aberrations” remain uncorrected and can lead to a blurred retinal image and blurred vision.  Collectively these other aberrations can be referred to as higher order aberration, while the aberrations that are typically corrected with spectacles and soft contact lenses are referred to as lower order aberration.

What kinds of higher order aberrations are present in keratoconus:

Pantanelli et al. have stated that the level of higher order aberration present in an eye with keratoconus is, on average, approximately 5.5 times higher than the level experienced in a control group.  In an effort to visualize higher-order aberration data, they are commonly represented graphically as shown in the figures below.  Examples of higher order aberration measured in one normal eye are shown in figure A, while an example of higher order aberration from one keratoconic eye are shown in figure B.  The circular nature of the map denotes the boundary of the measurement, which is defined by the round pupil of the eye.  A majority of the higher order aberration map in figure A is green (denoting a relative absence of higher order aberration).  However, the map in figure B displays a much larger variation in color, indicating the presence of higher order aberration  in this individual keratoconic eye in a greater quantity than the normal eye shown in figure A.

Figure A - normal-keratoconus
Figure A – normal
Figure B - keratoconus
Figure B – keratoconus

A wavefront aberration map of the “other aberrations” or higher order aberrations of two eyes. Figure A is an example of data for a normal eye and figure B is an example of data for an eye with keratoconus.

If refraction is not capable of quantifying higher order aberrations, how are they measured?

One method for obtaining the information regarding higher order aberration shown above is with a wavefront sensor.  The wavefront sensor objectively (without patient feedback) collects information on the optical performance of the eye that can be used to calculate the amount of both lower and higher order aberration present.

Laboratory-based research related to custom contact lenses:

Several investigators in the laboratory (e.g. Katsoulos et al., Sabesan et al., Chen et al., Marsack et al.) have reported on work that attempts to further reduce higher order aberration by targeting the eye-specific higher order aberration seen in a given keratoconic eye.  The general philosophy behind these customized lenses is that the aberration pattern measured with the wavefront sensor is a more complete optical prescription for implementation of a custom contact lens.  Figure C demonstrates, in principle, the optical properties of a contact lens designed to correct the higher-order aberration in figure B.  Where the map of the eye (figure B) is red, the map of the correction (figure C) is blue, and vice versa.  When the lens is worn, the net effect as light propagates through the lens-eye system is the cancellation of the higher order aberration in a targeted manner.

Figure C -keratoconus correction
Figure C -keratoconus correction

In principle, this figure pictorially represents the higher order optical properties of a contact lens designed to fully correct the higher-order aberration of the eye represented in figure B.

What is next:

Investigators continue to push the technology behind custom contact lenses for keratoconus towards clinical relevance.  However, like every novel intervention strategy, we must manage our expectations.  Complexity in measuring keratoconic eyes, a need for specialized equipment and expertise to design and manufacture the lenses, the infrastructure needed to coordinate the clinical exam and manufacture efforts and cost associated with the process are a subset of the barriers that must be removed if this type of correction is to become more mainstream.  For this reason, it is my opinion that if/when these corrections become commonly available in the clinic, they will likely add to, and not replace, existing forms of corrections that patients and clinicians now utilize to correct vision.

jmarsack-bio-picJason Marsack, PhD
Research Assistant Professor
University of Houston, College of Optometry.
Dr. Marsack’s work focuses on the relationship between visual performance
and optical aberration in individuals with highly aberrated eyes.