EYE DEFECTS AND CURE

Common Eye Diseases & Disorders

2009-03-17T23:28:00.000-07:00

Myopia people see nearby objects clearly but distant objects appear blurred. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. The opposite defect of myopia is hyperopia or "farsightedness" or "long-sightedness" — this is where the cornea is too flat or the eye is too short.

Cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated.

Hyperopia, also known as far-sightedness, long-sightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred.

Nyctalopia is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition.

Iritis: acute and chronic. They differ in numerous ways. Acute iritis is a type of iritis that can heal independently within a few weeks. If treatment is provided, acute iritis improves quickly. Chronic iritis can exist for months or years before recovery occurs. Chronic iritis does not respond to treatment as well as acute iritis does. Chronic iritis is also accompanied by a higher risk of serious visual impairment.

Glaucoma is part of a group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. Raised intraocular pressure is a significant risk factor for developing glaucoma (above 22mmHg). One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.

Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.

Strabismusis a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles that prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception. Strabismus can be either a disorder of the brain coordinating the eyes or a disorder of one or more muscles, as in any process that causes a dysfunction of the usual direction and power of the muscle or muscles.

Ophthalmoparesis is a physical finding in certain neurologic illnesses. It refers to paralysis of the extraocular muscles which are responsible for eye movements. It can refer to complete paralysis of the eyes, in which case it is synonymous with ophthalmoplegia. More usually, it refers to a partial paralysis, in contrast to the complete paralysis denoted by ophthalmoplegia.

Red eye is a non-specific term to describe an eye that appears red due to illness, injury, or some other condition. "Conjunctival injection" and "bloodshot eyes" are two forms of red eye.

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Technology of lasic laser

2008-07-11T04:01:00.000-07:00

The LASIK technique was made possible by the Colombia-based Spanish ophthalmologist Jose Barraquer, who, around 1950 in his clinic in Bogotá, Colombia, developed the first microkeratome, used to cut thin flaps in the cornea and alter its shape, in a procedure called keratomileusis. Stephan Schaller assisted. Barraquer also provided the knowledge about how much of the cornea had to be left unaltered to provide stable long-term results.

Later technical and procedural developments included the RK (radial keratotomy), started in the '70s in Russia by Svyatoslav Fyodorov , and the development of PRK (photorefractive keratectomy) in the '80s in Germany by Theo Seiler. RK is a procedure where radial corneal cuts are made typically using a micrometer diamond knife, and has nothing to do with LASIK

In 1968, at the Northrup Corporation Research and Technology Center of the University of California, Mani Lal Bhaumik and a group of other scientists, while working on the development of a carbon-dioxide laser, developed the Excimer laser. This formed the cornerstone for LASIK eye surgery. Dr. Bhaumik announced his discovery in May of 1973 at a meeting of the Denver Optical Society of America in Denver, Colorado. He would later patent it.

The introduction of Laser in this refractive procedure started with the developments in Laser technology by Rangaswamy Srinivasan. In 1980, Srinivasan, working at IBM Research Lab, discovered that an ultraviolet excimer laser could etch living tissue in a precise manner with no thermal damage to the surrounding area. He named the phenomenon Ablative Photodecomposition (APD).[2]. Dr. Stephen Trokel published a paper in the American Journal of Ophthalmology in 1983, outlining the potential of using the excimer laser in refractive surgeries.

The first patent for LASIK was granted by the US Patent Office to Gholam A. Peyman, MD on June 20, 1989, US Patent #4,840,175, "METHOD FOR MODIFYING CORNEAL CURVATURE", describing the surgical procedure in which a flap is cut in the cornea and pulled back to expose the corneal bed. This exposed surface is then ablated to the desired shape with an excimer laser, following which the flap is replaced.

Using these advances in laser technology and the technical and theoretical developments in refractive surgery made since the 50's, LASIK surgery was developed in 1990 by Lucio Buratto (Italy) and Ioannis Pallikaris (Greece) as a melding of two prior techniques, keratomileusis and photorefractive keratectomy. It quickly became popular because of its greater precision and lower frequency of complications in comparison with these former two techniques.

Today, faster lasers, larger spot areas, bladeless flap incision, intraoperative pachymetry, and wavefront-optimized and -guided techniques have significantly improved the reliability of the procedure compared to that of 1991. Nonetheless, the fundamental limitations of excimer lasers and undesirable destruction of the eye's nerves have spawned research into many alternatives to "plain" LASIK, including all-femtosecond correction (Femtosecond Lenticule EXtraction, FLIVC), LASEK, Epi-LASIK, sub-Bowman’s Keratomileusis aka thin-flap LASIK, wavefront-guided PRK, and modern intraocular lenses.

RETREATMENTS

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Examples of healing and ablation related complications are:
Topographical abnormalities: decentrations, central islands, and peninsulas
Spherical aberrations: night vision problems, night glare, halos, star-bursting, ghosting
Irregular astigmatism: loss of best corrected spectacle vision
There is of course considerable cross-over as many surgically induced complications produce loss of contrast sensitivity, loss of best corrected vision and severe disturbances in night vision. While we have been managing surgical complications for several years, the development of wavefront technology has allowed us to finally fully evaluate all these patients and present possible treatment options for them. In about 70% of cases, we are now able to provide topographically guided solutions for patients. It is impossible however to predict which patients will be the most suitable candidates with the best chance of success until completing the diagnostic wavefront and topographical testing. The WaveLight 500 Hz Concerto Laser has been our excimer laser system of choice as the Tscherning wavefront analysis system has provided us with reproducible detailed data in the majority of cases for surgical planning. The laser system also possesses specific features ideal for both the new patient and the post-refractive surgery patient for higher quality visual results:
Laser spot size < 0.90 mm [0.63 mm half max.] Repetition rate 400 Hz True Effective Optical Zones upto 7 mm Infrared Eye-tracker with 2.5 msec response time and automatic centration Prolate cornea ( aspheric treatment patterns for classic and wavefront applications) The small laser spot size is mandatory to produce fine complex treatment patterns. The rapid repetition rate is vital to maintain corneal hydration intra-operatively, especially in wavefront guided procedures with larger optical zones where a prolonged treatment time could adversely affect the planned treatment profile. A simple principle in laser refractive surgery is to keep the eye as physiologically hydrated as possible intra-operatively for a faster visual recovery with less risk of swelling and epithelial ingrowth. In cases of patients with night glare, the ability to create a prolate 7 mm true effective optical zone with a 9mm blend zone is highly beneficial. Lastly, the eye-tracking response time must be short enough to adequately account for saccadic eye movement. The Wavelight Allegretto response time is better than any other excimer laser system without the need to dilate the pupil, which allows the patient to fixate on the target light more easily with a faster visual recovery. For topography-linked retreatments, the WaveLight 500 Hz Concerto Laser has the best capabilities at present. It should be understood however that the diagnostic analysis is what determines the final treatment method of choice recommended to any individual patient.

Safety

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The WaveLight 500 Hz Concerto Laser is a laser that provides the doctor and the patient the highest level of safety, accuracy and reliability in LASIK, allowing the doctor to truly customize and offer a treatment that is ideally adjusted to the individual needs of the patient.
The WaveLight 500 Hz Concerto Laser saves upto 40% of valuable corneal tissue for every dioptre of treatment when compared with other lasers. This results in the doctor being able to treat a higher power range keeping in mind long-term safety as well as treating lower powers with unmatched stability.

Procedure

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This is an outpatient procedure that usually takes 5-10 minutes per eye. The actual laser treatment usually takes a few seconds. First you will lie on the motorized bed. The eyes are anesthetized with eye drops only. The head is positioned under the laser. A soft clip keeps the eyelids gently and comfortably open during the treatment. You will be asked to look at a soothing green blinking light during the entire procedure.
During the treatment, an instrument called the microkeratome creates a corneal flap to make it a painless procedure. The computerized Excimer laser uses a beam of light to gently reshape the cornea so as to alter its curvature to the desired extent. The flap when replaced on the new corneal curvature allows images to be sharply focused on the retina. The goal is to eliminate or greatly reduce the dependence on glasses or contact lenses.
Once the procedure is completed, a soft contact lens or shield is sometimes placed on the eye. A post - procedure eye examination is performed and eye drops are prescribed. There may be mild discomfort for a few hours after the procedure.

Patients

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The treatment is for patients who have a refractive error and meet certain visual and medical criteria. In addition the best candidates tend to be those who are dissatisfied with their contact lenses or glasses and are motivated to make a change, whether it is due to occupational or lifestyle reasons. However, only a thorough examination by our LASIK team can evaluate whether or not you are medically suited for LASIK.

Custom LASIK

2008-07-11T03:27:00.000-07:00

With the latest technological advances, the standard LASIK eye surgery procedure can now be tailored to each individual patient. This is known as Custom LASIK or wavefront-guided LASIK, because it is driven by wavefront analysis of the eye optical system. This is how it works:
Like our fingerprints, each of our eyes is different and has its own unique shape and optical characteristics. As light passes through different structures in the eye, different optical errors are created that can interfere with sharp vision. There are two main types of optical errors, lower-order errors and higher-order errors. Lower order errors are nearsightedness, farsightedness, and astigmatism which are readily corrected with glasses or contact lenses. The error is measured by the quantity of lens power needed to achieve best-corrected vision. Higher order errors are caused by irregularities or imperfections in the optical structures of the eye, also affecting the quality of vision. These higher order errors are associated with subtle visual problems such as poor night vision, decreased contrast sensitivity, halo effects around lights, and other visual disturbances.
New technology called wavefront analysis can measure these higher and lower order errors and plot them onto a map, which can then be programmed on the excimer laser. This wavefront map is unique for each individual eye. In this way wavefront-guided LASIK eye surgery goes beyond treatment of the lower order errors addressed in conventional LASIK. Wavefront-guided LASIK is a customized laser treatment based on an individual's wavefront map, thus the name Custom LASIK.
Clinical trials in patients treated with Standard LASIK in one eye and Custom LASIK in the other eye showed that, even with 20/20 vision in both eyes, patients reported better clarity in the Wavefront guided eye. It is currently believed that patients have a greater chance of achieving 20/20 vision or better with Custom LASIK. They also have a reduced chance of having night vision problems.

INTRODUCTION

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LASIK eye surgery has become the most popular refractive procedure of all time and is the vision correction procedure of choice for refractive surgeons the world over. LASIK combines the precision of the excimer laser delivery system with the benefit of a sophisticated surgical instrument known as a microkeratome. LASIK eye surgery is performed under anesthetic eye drops. The microtome is used to create a thin corneal flap, which is opened like the page of a book. The excimer laser is then used to sculpt ultra-thin layers of the remaining cornea to change its shape.
By changing the shape of the cornea, treatment of nearsightedness, farsightedness, and/or astigmatism is possible for the appropriate eye. After the laser treatment, the flap is returned back to its original position and adheres without the use of stitches. The entire procedure takes less than 15 minutes for both eyes. There are two types of LASIK eye surgery, Standard LASIK and Custom LASIK (also known as Wavefront-guided LASIK).