vision problems undestanding your eyes

You turned to eyeglasses and contact lenses when life became blurry. When you visited your eye doctor, you probably heard about vision problems like nearsightedness, farsightedness, and astigmatism, but all that mattered was that you could see better when you left. So how do your eyes work, and what happens to your eyes when your vision becomes blurry?
How Your Eyes Work How Vision Problems Happen
Your eye works much like a camera. The light and images you see pass through the cornea and the lens at the front of your eye. They focus directly onto the retina, the nerve layer at the back of the eye, which then sends the image to the brain through the optic nerve.
Light rays must be bent, or refracted, by the cornea and the lens so they can focus on the retina. If you have a refractive error, the shape of your eye doesn't bend the light properly, giving you vision problems.

Common Vision Problems
Your doctor can identify many of the common vision problems, including:
Nearsightedness images focus in front of the retina because the eye is too long or the cornea too curved, so objects far away are blurry.
Farsightedness -- images focus behind the retina because the eye is too short or the cornea is too flat, so objects close to you are blurry.
Astigmatism images are distorted and are not uniform in all directions, so objects both near and far appear blurry.
Presbyopia disorder caused by the normal aging process that typically affects reading vision.
Doctors can also measure the severity of these vision problems by evaluating the shape of your eye and its cornea. The results determine your prescription.
These problems are usually corrected with eyeglasses, contact lenses, or by laser vision correction procedures. However, good visual acuity does not necessarily mean good visual quality. Experts believe other qualitative factors contribute to common low-light vision problems, including glare and halos. You can have these vision problems and still score 20/20 on a vision exam.

Questions to ask your doctor

For more information on questions to ask your doctor please review article "Questions for your Eye Doctor".
Are the desired results I described realistic?
Where is the surgery performed? How long will the procedure take?
How much will my vision improve?
Is it realistic to expect 20/20 vision in my particular case?
Would another procedure, such as PRK, radial/ astigmatic keratotomy, or implantable contact lens work better for me?
Are there other procedures that I should consider to enhance the affects of this procedure?
What kind of anesthesia is used?
What is your experience in performing this procedure? (How long has he/she performed this procedure, and how many he/she has performed in the past year?)
What percentage of patients has had significant complications? (The physician should disclose this information to you.)
Will you repeat or correct the procedure if it does not meet agreed upon goals? And if the procedure must be repeated / corrected, will I be charged again? (The physician should provide you with his/her policy on this issue.)
May I see testimonials or outcomes statistics of recent patients? The physician should provide many photos of recent patients.
May I have the names and contact information for several recent LASIK patients? (Follow up to get first-hand information on the procedure and the surgeon.)
Could I observe the exact procedure I am considering before I decide to have the surgery? (Either on videotape or ask to view one in real life.)
What should I expect post-operatively, in terms of soreness, what to watch for, medication, bathing, and level of activity?
Who will be assisting during the surgery? What are their qualifications? (Does the ophthalmologist perform the entire surgery?)
Have you ever had your malpractice insurance coverage denied, revoked, or suspended?
Do you offer patient financing?

What will happen at the initial consultation?

During the consultation, your physician will talk with you about the changes that you want to make in your vision. He/she will explain the different options available, the LASIKprocedure itself, and the risks and limitations involved. He/she will also explain the kind of anesthesia required; the surgical facility used, and costs. Your physician will begin by asking you for a complete medical history. He/she may also give you specific instructions in preparing for surgery, including guidelines for eating and drinking, smoking, and taking (or avoiding) vitamins, supplements and medications.If you wear contact lenses, you’ll need to stop wearing them for a specified period of time before your initial consultation or examination. The physician may schedule additional visits to ensure that the eye is stable. This lens-free period is different for hard and soft lenses, so you should ask your doctor to be sure that you have prepared properly.Take this opportunity to ask all the questions you have about the surgery, and ask to see testimonials and out-come statistics of the doctor’s recent patients, before and after surgery. Also ask for, and follow up on, patient references. Learning everything you can about your options, risks and benefits is the key to making an informed decision.

What are the most common benefits of this surgery?

LASIK eye surgery is used to correct and restore vision to individuals who currently wear glasses for near-sightedness, far-sightedness or astigmatism.Using surgery to correct vision is not necessarily a new idea; other older procedures, such as radial keratotomy, have been used to correct vision for many years. Now, LASIK is able to achieve the same or better results with less pain and a shorter healing time.

Lasik Information For Perfect Eyesight

If you need Lasik information, you have come to the right place. Here we will offer you all the information that you need regarding Lasik. Lasik is an acronym for Laser Assisted in Situ Keratomileusis. It is a type of refractive laser eye surgery, which, since its approval by the US Food and Drugs Administration (FDA), has been gaining immense popularity. Surveys show that 92-98% of the patients who have undergone Lasik vision correction have been satisfied.
Is Lasik Surgery Right For You?
Lasik vision correction is not for everyone. Therefore, you must have the right Lasik information before opting for this surgery. If you are: - Below 18 years of age- Pregnant- Taking prescription medicines- Diabetic- Suffering from any other health complications like glaucoma, rheumatoid arthritis, herpes infection of the eye or lupus- Averse to taking risksIf your answer is yes to any one of these, then Lasik surgery is not the right option for you. If you answered no, and suffer from refractive errors such as near-sightedness, far-sightedness or astigmatism, then continue reading for other Lasik information and the cost of Lasik eye surgery.
Before you undergo Lasik surgery, you will be asked to stop wearing contact lenses, make-up, lotion and perfume so that nothing interferes with the laser eye surgery. You will be given a mild sedative along with anesthetic eye drops during the operation. You will be awake during the operation. Once the operation is over, your vision may be slightly blurred and you may experience some discomfort. However, this will change over the next few days. As a precaution, you must be sure not to go near a hot tub or swimming pool for at least two weeks after undergoing a Lasik vision correction.What Are The Complications Of Lasik Eye Surgery?Like any surgery, Lasik surgery also has certain complications. The most common ones would be:- Dry eyes- Light sensitivity- Ghosts or Double vision- Blurry vision- Discomfort- Corneal scarring or infection- Overcorrection or under correctionYet, Lasik vision correction is an FDA approved safe way of permanently improving your eyesight.
What is the Cost of Lasik Eye Surgery?
The cost of Lasik eye surgery varies considerably, depending on the condition of your eyes, the centre and the surgeon. The cost of pre-surgical investigations and post-surgical treatment can increase the overall costs. The cost of laser eye correction surgery is quoted in terms of per eye. It can cost anything between $500 and $3000 per eye. Prices have been increasing due to improved technological equipment being used for surgery. Get adequate Lasik information before settling for a surgeon and a centre. After all, your eyes are at stake.

What should I expect before, during, and after surgery?

What to expect before, during, and after surgery will vary from doctor to doctor and patient to patient. This section is a compilation of patient information developed by manufacturers and healthcare professionals, but cannot replace the dialogue you should have with your doctor. Read this information carefully and with the checklist, discuss your expectations with your doctor.Before SurgeryIf you decide to go ahead with LASIK surgery, you will need an initial or baseline evaluation by your eye doctor to determine if you are a good candidate. This is what you need to know to prepare for the exam and what you should expect:If you wear contact lenses, it is a good idea to stop wearing them before your baseline evaluation and switch to wearing your glasses full-time. Contact lenses change the shape of your cornea for up to several weeks after you have stopped using them depending on the type of contact lenses you wear. Not leaving your contact lenses out long enough for your cornea to assume its natural shape before surgery can have negative consequences. These consequences include inaccurate measurements and a poor surgical plan, resulting in poor vision after surgery. These measurements, which determine how much corneal tissue to remove, may need to be repeated at least a week after your initial evaluation and before surgery to make sure they have not changed, especially if you wear RGP or hard lenses. If you wear:soft contact lenses, you should stop wearing them for 2 weeks before your initial evaluation.toric soft lenses or rigid gas permeable (RGP) lenses, you should stop wearing them for at least 3 weeks before your initial evaluation.hard lenses, you should stop wearing them for at least 4 weeks before your initial evaluation.

Lasik Surgery Checklist

Know what makes you a poor candidateCareer impact - does your job prohibit refractive surgery? Cost - can you really afford this procedure? Medical conditions - e.g., do you have an autoimmune disease or other major illness? Do you have a chronic illness that might slow or alter healing? Eye conditions - do you have or have you ever had any problems with your eyes other than needing glasses or contacts? Medications - do you take steroids or other drugs that might prevent healing? Stable refraction - has your prescription changed in the last year? High or Low refractive error - do you use glasses/contacts only some of the time? Do you need an unusually strong prescription? Pupil size - are your pupils extra large in dim conditions? Corneal thickness - do you have thin corneas? Tear production - do you have dry eyes?Know all the risks and procedure limitationsOvertreatment or undertreatment - are you willing and able to have more than one surgery to get the desired result? May still need reading glasses - do you have presbyopia? Results may not be lasting - do you think this is the last correction you will ever need? Do you realize that long-term results are not known? May permanently lose vision - do you know some patients may lose some vision or experience blindness? Dry eyes – do you know that if you have dry eyes they could become worse, or if you don’t have dry eyes before you could develop chronic dry eyes as a result of surgery? Development of visual symptoms - do you know about glare, halos, starbursts, etc. and that night driving might be difficult? Contrast sensitivity - do you know your vision could be significantly reduced in dim light conditions? Bilateral treatment - do you know the additional risks of having both eyes treated at the same time? Patient information - have you read the patient information booklet about the laser being used for your procedure?Know how to find the right doctorExperienced - how many eyes has your doctor performed LASIK surgery on with the same laser? Equipment - does your doctor use an FDA-approved laser for the procedure you need? Does your doctor use each microkeratome blade only once? Informative - is your doctor willing to spend the time to answer all your questions? Long-term Care - does your doctor encourage follow-up and management of you as a patient? Your preop and postop care may be provided by a doctor other than the surgeon. Be Comfortable - do you feel you know your doctor and are comfortable with an equal exchange of information?Know preoperative, operative, and postoperative expectationsNo contact lenses prior to evaluation and surgery - can you go for an extended period of time without wearing contact lenses? Have a thorough exam - have you arranged not to drive or work after the exam? Read and understand the informed consent - has your doctor given you an informed consent form to take home and answered all your questions? No makeup before surgery - can you go 24-36 hours without makeup prior to surgery? Arrange for transportation - can someone drive you home after surgery? Plan to take a few days to recover - can you take time off to take it easy for a couple of days if necessary? Expect not to see clearly for a few days - do you know you will not see clearly immediately? Know sights, smells, sounds of surgery - has your doctor made you feel comfortable with the actual steps of the procedure? Be prepared to take drops/medications- are you willing and able to put drops in your eyes at regular intervals? Be prepared to wear an eye shield - do you know you need to protect the eye for a period of time after surgery to avoid injury? Expect some pain/discomfort - do you know how much pain to expect? Know when to seek help - do you understand what problems could occur and when to seek medical intervention? Know when to expect your vision to stop changing - are you aware that final results could take months? Make sure your refraction is stable before any further surgery - if you don't get the desired result, do you know not to have an enhancement until the prescription stops changing?

FDA-Approved lasers for LASIK

devises at fda can help you search for detailed information about specific medical devices, including diagnostic tests. Use this web site to:Find out if devices are approved by FDAGet phone numbers and addresses of medical device companiesRead and print patient information and instructions for useLearn about changes to devices since they were approved.

Technological development

The LASIK technique was made possible by the Colombian-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. He also provided the knowledge about how much of the cornea had to be left unaltered to provide a stable long-term result.Later technical and procedural developments included the RK (radial keratotomy) started in the 70’s in Russia by Svyatoslav Fyodorov and the development of PRK (photorefractive keratectomy) in the 80’s in Germany by Theo Seiler.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, would develop the Excimer laser, where molecules that do not normally exist come into being when xenon, argon or krypton gases are excited. This would form 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. [1]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.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, and wavefront-optimized and -guided techniques have significantly improved the reliability of the procedure as 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.

Complications

The incidence of refractive surgery patients having unresolved complications six months after surgery has been estimated from 3%[4] to 6%.[5] The risk for a patient of suffering from disturbing visual side effects like halos, double vision (ghosting), loss of contrast sensitivity (foggy vision) and glare after LASIK depends on the degree of ametropia before the laser eye surgery and other risk factors.[6] For this reason, it is important to take into account the individual risk potential of a patient and not just the average probability for all patients.[7] The following are some of the more frequently reported complications of LASIK[8][6]:Surgery induced dry eyesOvercorrection[9] or undercorrectionVisual acuity fluctuationHalos[10] or starbursts[11] around light sources at nightLight sensitivityGhost images[12] or double visionWrinkles in flap (striae)[13]Decentered ablationDebris or growth under flapThin or buttonhole flap [14]Induced astigmatismCorneal EctasiaFloatersEpithelium erosionPosterior vitreous detachment[15]Macular hole[16]Complications due to LASIK have been classified as those that occur due to preoperative, intraoperative, early postoperative, or late postoperative sources

Intraoperative complications

The incidence of flap complications has been estimated to be 0.244%.[18] Flap complications (such as displaced flaps or folds in the flaps that necessitate repositioning, diffuse lamellar keratitis, and epithelial ingrowth) are common in lamellar corneal surgeries[19] but rarely lead to permanent visual acuity loss; the incidence of these microkeratome-related complications decreases with increased physician experience.[20][21] According to proponents of such techniques, this risk is further reduced by the use of IntraLasik and other non-microkeratome related approaches, although this is not proven and carries its own set of risks of complications from the IntraLasik procedure.A slipped flap (a corneal flap that detaches from the rest of the cornea) is one of the most common complications. The chances of this are greatest immediately after surgery, so patients typically are advised to go home and sleep to let the flap heal. Patients are usually given sleep goggles or eye shields to wear for several nights to prevent them from dislodging the flap in their sleep. A faster operation may decrease the chance of this complication, as there is less time for the flap to dry. "Traditional" LASIK is the fastest form of the procedure, as IntraLasik requires the flap to be left flipped over for up to forty minutes to allow the surgeon to clear the haze over the cornea created by the laser microkeratome during the procedure.Flap interface particles are another finding whose clinical significance is undetermined.[22] A Finnish study found that particles of various sizes and reflectivity were clinically visible in 38.7% of eyes examined via slit lamp biomicroscopy, but apparent in 100% of eyes using confocal microscopy.

Early postoperative complications

The incidence of diffuse lamellar keratitis (DLK)[7], also known as the Sands of Sahara syndrome, has been estimated at 2.3%.[23] When diagnosed and appropriately treated, DLK resolves with no lasting vision limitation.The incidence of infection responsive to treatment has been estimated at 0.4%.[23] Infection under the corneal flap is possible. It is also possible that a patient has the genetic condition keratoconus that causes the cornea to thin after surgery. Although this condition is screened in the preoperative exam, it is possible in rare cases (about 1 in 5,000) for the condition to remain dormant until later in life (the mid-40s). If this occurs, the patient may need rigid gas permeable contact lenses, Intrastromal Corneal Ring Segments (Intacs),[24] Corneal Collagen Crosslinking with Riboflavin[25] or a corneal transplant.The incidence of persistent dry eye has been estimated to be as high as 28% in Asian eyes and 5% in Caucasian eyes.[5] Nerve fibers in the cornea are important for stimulating tear production. A year after LASIK, subbasal nerve fiber bundles remain reduced by more than half.[26] Some patients experience reactive tearing, in part to compensate for chronic decreased basal wetting tear production.The incidence of subconjunctival hemorrhage has been estimated at 10.5% (according to a study undertaken in China; thus results may not be generally applicable due to racial and geographic

Late postoperative complications

The incidence of epithelial ingrowth has been estimated at 0.1%.[23]Glare is another commonly reported complication of those who have had LASIK.[27]Halos or starbursts around bright lights at night are caused by the irregularity between the lasered part and the untouched part. It is not practical to perform the surgery so that it covers the width of the pupil at full dilation at night, and the pupil may expand so that light passes through the edge of the flap into the pupil.[28] In daytime, the pupil is smaller than the edge. Modern equipment is better suited to treat those with large pupils, and responsible physicians will check for them during examination.Late traumatic flap dislocations have been reported 1–7 years post-LASIK

Other

k Lasik and other forms of laser refractive surgery (i.e. PRK,LASEK and Epi-LASEK) change the dynamics of the cornea. These changes make it difficult for your optometrist and ophthalmologist to accurately measure your intraocular pressure, essential in glaucoma screening and treatment. The changes also affect the calculations used to select the correct intraocular lens implant when you have cataract surgery. This is known to ophthalmologists as a "refractive surprise". The correct intraocular pressure and intraocular lens power can be calculated if you can provide your eye care professional with your preoperative, operative and postoperative eye measurements.Although there have been improvements in LASIK technology[30][31][32], a large body of conclusive evidence on the chances of long-term complications is not yet established. Also, there is a small chance of complications, such as haziness, halo, or glare, some of which may be irreversible because the LASIK eye surgery procedure is irreversible.The incidence of macular hole has been estimated at 0.2 per cent[16] to 0.3 per cent.[33] The incidence of retinal detachment has been estimated at 0.36 per cent.[33] The incidence of choroidal neovascularization has been estimated at 0.33 per cent.[33] The incidence of uveitis has been estimated at 0.18 per cent[34]Although the cornea usually is thinner after LASIK, because of the removal of part of the stroma, refractive surgeons strive to maintain a minimum thickness to avoid structurally weakening the cornea. Decreased atmospheric pressure at higher altitudes has not been demonstrated as extremely dangerous to the eyes of LASIK patients. However, some mountain climbers have experienced a myopic shift at extreme altitudes.[35][36] There are no published reports documenting scuba diving-related complications after LASIK.[37]In situ keratomileusis effected at a later age increases the incidence of corneal higher-order wavefront aberrations.[38][39] Conventional eyeglasses do not correct higher order aberrations.Microfolding has been reported as "an almost unavoidable complication of LASIK" whose "clinical significance appears negligible".[22]Myopic (nearsighted) people who are close to the age (mid- to late-forties) when they will require either reading glasses or bifocal eyeglasses, may find that they still require reading glasses despite having undergone refractive LASIK surgery. Myopic people generally require reading glasses or bifocal eyeglasses at a later age than people who are emmetropic (those who see without eyeglasses), but this benefit is lost if they undergo LASIK. This is not a complication, but an expected result of the physical laws of optics. Although there is currently no method to completely eradicate the need for reading glasses in this group, it may be minimized by performing a variation of the LASIK procedure called "slight monovision". In this procedure, which is performed exactly like distance-vision-correction LASIK, the dominant eye is set for distance vision, while the non-dominant eye is set to the prescription of the patient's reading glasses. This allows the patient to achieve a similar effect as wearing bifocals. The majority of patients tolerate this procedure very well and do not notice any shift between near and distance viewing, although a small portion of the population has trouble adjusting to the monovision effect. This can be tested for several days prior to surgery by wearing contact lenses

What is lasik

The eye and vision errorsThe cornea is a part of the eye that helps focus light to create an image on the retina. It works in much the same way that the lens of a camera focuses light to create an image on film. The bending and focusing of light is also known as refraction. Usually the shape of the cornea and the eye are not perfect and the image on the retina is out-of-focus (blurred) or distorted. These imperfections in the focusing power of the eye are called refractive errors. There are three primary types of refractive errors: myopia, hyperopia and astigmatism. Persons with myopia, or nearsightedness, have more difficulty seeing distant objects as clearly as near objects. Persons with hyperopia, or farsightedness, have more difficulty seeing near objects as clearly as distant objects. Astigmatism is a distortion of the image on the retina caused by irregularities in the cornea or lens of the eye. Combinations of myopia and astigmatism or hyperopia and astigmatism are common. Glasses or contact lenses are designed to compensate for the eye's imperfections. Surgical procedures aimed at improving the focusing power of the eye are called refractive surgery. In LASIK surgery, precise and controlled removal of corneal tissue by a special laser reshapes the cornea changing its focusing power.(See the animation of the LASIK procedure and what should I expect before, during, and after surgery.)Other types of refractive surgery Radial Keratotomy or RK and Photorefractive Keratectomy or PRK are other refractive surgeries used to reshape the cornea. In RK, a very sharp knife is used to cut slits in the cornea changing its shape. PRK was the first surgical procedure developed to reshape the cornea, by sculpting, using a laser. Later, LASIK was developed. The same type of laser is used for LASIK and PRK. Often the exact same laser is used for the two types of surgery. The major difference between the two surgeries is the way that the stroma, the middle layer of the cornea, is exposed before it is vaporized with the laser. In PRK, the top layer of the cornea, called the epithelium, is scraped away to expose the stromal layer underneath. In LASIK, a flap is cut in the stromal layer and the flap is folded back.Another type of refractive surgery is thermokeratoplasty in which heat is used to reshape the cornea. The source of the heat can be a laser, but it is a different kind of laser than is used for LASIK and PRK. Other refractive devices include corneal ring segments that are inserted into the stroma and special contact lenses that temporarily reshape the cornea (orthokeratology).What the FDA regulatesIn the United States, the Food and Drug Administration (FDA) regulates the sale of medical devices such as the lasers used for LASIK. Before a medical device can be legally sold in the U.S., the person or company that wants to sell the device must seek approval from the FDA. To gain approval, they must present evidence that the device is reasonably safe and effective for a particular use, the "indication." Once the FDA has approved a medical device, a doctor may decide to use that device for other indications if the doctor feels it is in the best interest of a patient. The use of an approved device for other than its FDA-approved indication is called "off-label use." The FDA does not regulate off-label use or the practice of medicine.The FDA does not have the authority to:Regulate a doctor's practice. In other words, FDA does not tell doctors what to do when running their business or what they can or cannot tell their patients.Set the amount a doctor can charge for LASIK eye surgery."Insist" the patient information booklet from the laser manufacturer be provided to the potential patient.Make recommendations for individual doctors, clinics, or eye centers. FDA does not maintain nor have access to any such list of doctors performing LASIK eye surgery.Conduct or provide a rating system on any medical device it regulates.The first refractive laser systems approved by FDA were excimer lasers for use in PRK to treat myopia and later to treat astigmatism. However, doctors began using these lasers for LASIK (not just PRK), and to treat other refractive errors (not just myopia). Over the last several years, LASIK has become the main surgery doctors use to treat myopia in the United States. More recently, some laser manufacturers have gained FDA approval for laser systems for LASIK to treat myopia, hyperopia and astigmatism and for PRK to treat hyperopia and astigmatism.See the section on FDA-approved lasers for more details on which lasers have received FDA approval and the specific indications and treatment ranges for which they were approved.