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.

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.

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 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.

$Child refractive exam - pediatric contact lenses$ He 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, 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.

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).

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).

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!

Sumit “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

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.

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.

Marjan 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.

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 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.

Jeffrey 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.

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.

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 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.

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.

Jason 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.

Help for Computer Users

Working long hours in front of the computer requires a fairly unchanging body, head and eye position which can cause discomfort. Correct working position, periodic stretch breaks, frequent eye blinking, artificial tears for lubrication are all very important. However, it’s not always easy to remember this when you are engrossed in work. Here are a few fun, free and easy-to-install “break reminders” to help:

WorkSafe Sam - break reminder — WorkSafe Sam

WorkSafe Sam is a desktop tool that provides stretching tips to help reduce eye and muscle strain for office workers (clicking on this link will open a file on your computer because this is a zip file).

Workrave is break reminder program that alerts you to take “micro-pauses” and stretch breaks.

Take Your Break is another break reminder designed to prevent or minimize repetitive strain injury, computer eye strain and other computer related health problems. It has a friendly interface and a tray icon status indicator. It runs quietly in the background, monitoring your activity and reminding you to take regular breaks.

And remember to blink. Blinking cleans the ocular surface of debris and flushes fresh tears over the ocular surface. Each blink brings nutrients to the eye surface structures keeping them healthy. The flow of tears is responsible for wetting the lower third of the cornea. This is very important in KC, since this area is generally below the bulge of the cone and in many cases irritated by wobbly RGP lenses. Maybe your job requires hours of work at a computer. Maybe you like to spend your free time surfing the internet. Whatever the reason, your body is probably feeling the effects of spending too much time staring at a computer monitor, which could result in Computer Vision Syndrome (CVS). The most common symptoms are: eye strain, dry or irritated eyes,redness in eyes,difficulty in refocusing eye,neck pain,double vision,blurred vision, fatigue, and headaches.

Please join us on Thursday when Dr. Bezalel Schendowich will be providing a detailed insight into the importance of blinking, going beyond computer usage.

Cathy Warren, RN
Executive Director
National Keratoconus Foundation

Corneal Transplant Surgery Options

In this day and age of advancing technology, corneal transplants have changed from a long arduous ordeal to a more simple and precise procedure that offers faster visual recovery. Instead of replacing the entire cornea for any and all corneal diseases, we now perform disease targeted partial corneal transplants. If the disease involves the back layer of the cornea, we perform endothelial keratoplasty and replace only the diseased inner layer of the cornea. Conversely, if the problematic portions are the front layers of the cornea, we perform anterior lamellar keratoplasty. The co-morbidity and risk of rejection from partial corneal transplants are significantly less than the traditional full thickness transplants.

With endothelial keratoplasty, a small incision, about 4-5 mm is made and a sheet of donor endothelial cells are placed into the anterior chamber of the eye. A large air bubble is then used to float this sheet up so that it opposes the posterior or back portion of the cornea. The patient is asked to position face up for 24 hours. Over this period of time, the cells will “stick” on their own and thus no sutures are required to keep the graft in place.,/span>

Figure 1 - corneal transplant — Figure 1

Anterior lamellar keratoplasty is done for superficial scars and opacities of the cornea or for keratoconus, a genetic degeneration of the cornea that is seen in younger individuals. In this case, the native endothelial cells of the patient are healthy and therefore are left intact while the remainder of the cornea is transplanted. This significantly lowers the risk of rejection, which is traditionally a much higher risk in young patients. Multiple sutures are required to maintain this graft in place however, with the advent of femtosecond laser technology, the wound configuration is made in such a way as to promote rapid healing and visual recovery. (Figure 1) Sutures are removed at an earlier time than with traditional surgery and the eye is able to undergo visual rehabilitation with glasses or contact lenses in 3-6 months’ time.

Corneal transplantation does not require waiting on a list for a donor to become available like it once did. There are now multiple excellent eye banks across America that harvest, screen, and distribute donor tissue to surgeons. This way, tissue is readily available and patients only need to schedule a time based on their own and their surgeon’s time schedule. Post operatively, patients are asked to return to regular activity with the exception of no heavy lifting or bending for a period of 2 months. Antibiotic and anti-rejection drops are started immediately after surgery and continued for several months after. No oral medications aside from the patient’s regular medications are required.

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