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As light rays pass through one medium to another, such as from air to water, they bend.(1) This is known as refraction. When these rays pass through the eye tissues of the cornea Cornea: The clear, curved surface at the front of the eye through which light enters the eye. Along with the sclera, the cornea provides external protection for the eye. and lens, they are also refracted in a manner that brings them into focus on the retina. When the eye is unable to focus light on the retina, usually because the shape of the eye isn’t quite right, this is called a refractive error. Refractive error: Vision problems caused by an imperfect optical system, most commonly myopia, hyperopia, and astigmatism.
If you’re reading this, chances are you’ve already been dealing with contact lenses or eye glasses to correct your vision. To help you better understand common visual issues, below is a brief overview of the most typical refractive error conditions, as well as eye problems that stem more from aging and the stiffening or clouding of the eye’s lens that can develop in our later years.
Nearsightedness
Also called myopia, Myopia: A refractive error resulting in the inability for the eye to see distant objects. Also referred to as "nearsightedness." Occurs when the eyeball is too long or when the cornea has too much curvature, preventing the light entering the eye from focusing correctly on the retina and resulting in blurry vision at a distance. Eyeglasses, contact lenses, and refractive surgery are treatment options for correcting vision impairment caused by myopia. nearsightedness (blurred distance vision) is the most common refractive error. This happens typically when the eye is too long or the cornea too steep. This extra length causes light from distant objects to focus at a point just short of reaching the retina, which causes the light to disperse and provides the brain with an out-of-focus image.
Farsightedness
The common term for hyperopia, Hyperopia: The medical term for "farsightedness," a refractive error resulting in an inability to see objects at close range. Typically caused by either a cornea with too little curvature or an eyeball that is too short, hyperopia causes light entering the eye to focus improperly on the retina, resulting in blurry close-up vision. Eyeglasses, contact lenses, and refractive surgery are treatment options for correcting vision impairment caused by hyperopia. farsightedness (meaning you can’t see things up close) is caused by an eye that is too short or a cornea that is too flat. The reduced length leaves the cornea and lens Lens: The transparent disc behind the pupil that brings light into focus on the retina. insufficient space to bring together the light rays to a focal point upon the retina, thus focusing the image beyond the retina and, again, sending poor signals to the brain.
Astigmatism
Another term used for poor eye curvature, astigmatism is what happens when the cornea is not round enough but shaped more like a football, which prevents the eye from being able to focus clearly at any distance, near or far.
Presbyopia
This condition typically begins to affect people between the ages of 40 and 50. Presbyopia occurs when the natural lens of the eye ages, thus hardening and losing its flexibility, which typically results in loss of up-close vision and often leads to a need for reading glasses.
Cataracts
Contrary to popular belief, a cataract is not a film that forms over the eye(2) but rather a change in the clarity of the lens inside your eye, allowing less light to pass through. This gradual clouding can make vision less sharp over time. The light that does make it through to the retina is diffused, turning vision blurry.
References1.Oracle ThinkQuest Education Foundation. Light Rays, Refraction. http://library.thinkquest.org/27066/lightrays/nlrefraction.html. Accessed on October 16, 2010.
2.Oregon Academy of Ophthalmology. Public Info: Cataract.
http://www.oregoneyephysicians.org/pages/medinfo-pages/cataract.html. Accessed October 16, 2010.
Posted on 5 November 2012 | 1:19 pm
INTACS were approved for the treatment of relatively low degrees of nearsightedness in the 1990's. INTACs are semi-circular implants that are placed within the stroma of the cornea: hence they are classified as intracorneal ring segments. The segments are placed in the mid-periphery of the cornea and improve the uncorrected vision in myopes by flattening the central cornea. While intracorneal ring segments were effective for low degrees of myopia, laser vision correction was a least as effective as INTACs, and could be performed without incurring the cost of an implant. The intense competition in the vision correction market prevented INTACS from gaining any significant market share; however, the intracorneal implant has found a niche market by being a popular and effective treatment in the treatment of a corneal condition called keratoconus.
Posted on 19 September 2012 | 10:32 am
The postoperative period involves the instillation of drops for a few weeks while the eye heals. The medications that are applied include Antibiotics and anti-inflammatory agents. The anti-inflammatory agents (chemically similar to aspirin formulated as a drop.) Recently, the trend has been to use both types of anti-inflammatory agents, as each type of drug acts through a slightly different pathway. You will be provided with a medication schedule, and a list of activities to avoid.
I do ask that patients take a one to two week hiatus from swimming, hot tubs or other activities that could but their eyes in contact with "common" water. Pools, hot tubs and other forms of common water often serve as breeding grounds for microbes which may infect an incompletely healed surgical wound. Typically patients resume most of their normal activity level within a few days, as small-incision surgery has largely eliminated the need for an extended convalescence.
Patients are seen on the day after their procedure, and usually are fully rehabilitated within a month of their treatment. Congratulations! It is time to enjoy your new and improved vision!
Posted on 17 July 2012 | 2:59 pm
While most people would select the enhanced optical performance offered by the presbyopic lenses, these implants are not appropriate for all patients. There are a number of conditions and diseases which either decrease or totally neutralize the benefits these lenses can deliver. While many of these limitations are agreed upon by most cataract specialists, there may be room for debate among surgeons, so I will offer you my own guidelines (and preferences) based upon the specific ocular condition. Of course, I have a discussion with each patient who has any of these conditions and is considering optimizing his/her cataract procedure with an advanced technology IOL. Accordingly, these patients realize that their eyes are not 100% typical, and there is the very real possibility that the eyes will not see 20/20 after ANY type of IOL is implanted.
Macular Degeneration Age-related macular degeneration (ARMD) is the subject of numerous articles, chapters and indeed textbooks. To attempt to describe it in any detail is well beyond the scope of this text. Suffice it to say that macular degeneration is typically an age-related loss of the cells which comprise the retina – the “film” where images are generated in your eye. While there are a few dissenting opinions at the time this monolog is being printed, most surgeons queried will not recommend the use of multifocal IOLs in patients with moderate to severe macular degeneration. It is typically my custom NOT to implant multifocal presbyopic IOLs in eyes that have macular degeneration. The disease typically is progressive (that is, it gets worse as time passes) so it is questionable if a patient would appreciate any benefit with these lenses. In contrast, I have had success implanting accommodating intraocular lenses (the lenses which flex like our natural lens) in patients with early to moderate macular degeneration. Macular degeneration tends not to affect the performance of the accommodating IOLs – presumably due to their more physiologic mechanism of action.
Severe Dry Eye Syndrome The cornea is the outer “window” and primary light-bending structure of the eye. The cornea is covered by a thin layer of tears, the precorneal tear film (PCTF). The tear film protects the eye from dust, allergens and infectious agents, as well as serving as an avenue for the immune system. Additionally, a stable, contiguous PCTF is vital for the cornea to fulfill its function as the eye’s primary focusing element.
Dry eye syndrome is the condition when the surface of the eye has a deficient or unstable PCTF. As a result, there are “dry spots” on the surface of the cornea. The dry spots can cause irritation to the extent that the patient experiences excessive tearing – this is caused by the dryness becoming a noxious stimulus which causes a physiologic response similar to the tearing that occurs when there is a piece of sand or dust in the eye. The excessive tear volume actually causes the vision to decrease, in addition to introducing the inconvenience of having tears running down one’s cheek in severe cases.
The patient’s vision may also be affected even when there is not any discomfort or excessive tearing. The dryness may cause an irregularity upon the surface of the cornea which results in light scattering. The process of light scattering introduces a source of inefficiency in the eye’s optical system. A cornea that scatters light is described by ophthalmologists as having aberrations. Aberrations are imperfections which cause light to defocus, resulting in a blurring of images, as light does not pass efficiently to the retina. Highly aberrated corneas prevent ALL IOLs from working optimally, but especially multifocal presbyopic lenses from working effectively. For this reason, I do not recommend placing multifocal intraocular lenses in eyes with severe dry eye.
In contrast, accommodating presbyopic lenses and astigmatism-correcting lenses may be placed in eyes with significant corneal optical aberrations; while the results may not be “perfect” 20/20 vision, the results of cataract surgery in patients with aberrated corneas can be quite gratifying.
Dry eye syndrome is not the only condition which results in cornea-based optical aberrations. Corneal scarring from disease or trauma may introduce optical aberrations. Radial keratotomy was a popular refractive surgery procedure in the 1980s and 90s. The keratotomy incisions induce optical aberrations, and actually induce multifocality of the cornea. Accordingly, most cornea specialists will not place a multifocal IOL in an eye that has had radial keratotomy. Instead, the use of the accommodating presbyopic IOL in “post-RK” eyes has resulted in some excellent outcomes as these patients enjoy the dual benefit of a multifocal cornea combined with an accommodating IOL.
The decision on whether to implant a presbyopic lens (or indeed perform cataract surgery at all!) in a patient with dry eye, or any eye that has corneal disease can be difficult. Among the factors to be considered preoperatively include the degree of dryness, cause of dryness, degree of visual debilitation, visual potential of the eye and patient expectations.
Diabetes Mellitus The ocular sequelae of diabetes mellitus were among the leading causes of blindness in the United States in the mid to late 1900s. Diabetes affects virtually all of the body’s systems and the eye is no exception. Cornea, lens and retina are all potential targets of this disease. Diabetic retinopathy, like macular degeneration, is a disease which has been well chronicled, and an extensive discussion about diabetic ocular disease is beyond the scope of this text.
The process of diabetic retinopathy is caused by serum glucose compromising the competence of the vascular endothelium. That is, abnormally high levels of blood sugar cause blood vessels to leak into the retina, causing a loss of retinal function – again a process where the “film” of the camera is impaired. I generally do not recommend the multifocal presbyopic intraocular lenses in cases where the patient’s retinal function has been affected (although the accommodating lenses may be considered).
There is one diabetic condition where I typically do NOT recommend either type of presbyopic intraocular lens; the condition is called proliferative diabetic retinopathy. In proliferative retinopathy, the serum glucose has so adversely affected the retinal vasculature that there is a gross lack of oxygen being delivered to the retina. This lack of oxygen, or hypoxia, results in the growth of new abnormal retina vessels which have a tendency to actually bleed inside the eye. Eyes that have this degree of impairment from diabetes do not typically realize a significant benefit from presbyopic IOLs.
Posted on 29 May 2012 | 2:55 pm
The front of the eye serves as a focusing element to bring a sharp image upon the retina. Creating a sharp retinal image requires that the cornea and lens each create a single focal point. Generating a single focal point for the cornea requires that the cornea has a round "dome" shape with the same degree of curvature for 360 degrees, therefore no matter what place light enters the cornea, it is bent to the same degree en route to the lens. Astigmatism, specifically corneal astigmatism, may be described as the condition where the cornea has at least two radii of curvature. Less technically explained, the outer window of the eye has a more oval or "football" shape. The two different curvatures of the cornea generate tow different focal points because light rays are bent differently depending upon which part of the cornea they enter; as a result even a perfectly symmetric crystalline lens or standard IOL will not be able to bring the light rays to a single retinal focal point, so the eye does not create a clear image for the patient.
Before the advent of advanced technology implants removing the cataract involved exclusively removing and replacing the eye's lens and if the eye had significant corneal astigmatism before cataract surgery, the condition would exist after surgery. The introduction of astigmatism-correcting or toric intraocular lenses finally gave astigmatic patients an answer to correct their vision, no only reversing the effects of the cataract, but actually making their uncorrected vision better than it had been for years - typically decades! Toric lenses correct vision in a manner that standard single focus lenses cannot - the toric lens, like the astigmatic eye's particular corneal curvature so that the toricity of the IOL neutralizes the patient's corneal astigmatism.
Correcting or "neutalizing" the corneal astigmatism creates a more precise focal image, thereby reducing or totally eliminating the cornea-induced blur (in ophthalmology speak" this is called "collapsing the Conoid of Sturm" or reducing the distance between the two corneal focal points.
Posted on 24 April 2012 | 1:27 pm
Modern cataract surgery is a "day stay" procedure. Most ambulatory surgicenters (ASCs) and hospitals allow the patient to remain in their clothes and merely wear a gown, cap and shoe covers in the operating room. Typically, the patients are allowed to have a light breakfast. On the day of treatment, you will be at the hospital or ASC for about three hours. The procedure is usually performed under topical anesthesia, which means drops are applied to the eye for comfort, in addition to dilating drops. The dilating drops increase the size of the pupil so the surgeon has easier access to the cataract. In addition, an intravenous catheter is placed to facilitate the use of sedation during your procedure.
You will then be brought into the treatment room where the anesthesiologist and circulating nurse will make sure you are comfortable and well-positioned appropriately the next member of our surgical team, the scrub nurse, will use an antiseptic solution to "prep" your eye. The scrub nurse will then place a light drape around your eye so that there will be a sterile surgical field. Alas! We can get to the actual process of removing the cataract and restoring your vision. (see video at http://www.northeastlaser.net/Special-id-85.html)
The surgical microscope will then be positioned about one foot above the operative eye. The microscope has intense lighting and in combination with the dilation, the brightness can be very impressive. The light intensity is notable only for a few moments, after which your eye will adapt to the brightness. The surgeon then places a small eyelid supporting instrument so that you will not have to worry about blinking.
Utilizing the microscope to magnify your eye, the surgeon creates a small peripheral corneal incision that allows controlled access to the internal structures of the eye. The surgeon has micro instrument which enable him/her to address the cataract through the pupil. The next step involves creating a small opening in the cataract capsule. This opening is about 5 millimeters in diameter, and it is through this opening the surgeon applies ultrasonic energy to gently disassemble the cataract nucleus into tiny fragments. The cataract fragments are suspended in the balanced saline solution which the surgeon gently rinses from your eye.
Once the nucleus has been removed, the cortex of the cataract remains. As the cortex is typically very soft, no energy is needed to disassemble it, and cortical removal is usually performed with a very low power vacuum delivered by an instrument called the irrigation/aspiration hand piece. Cortical clean-up completes the process of cataract extraction, and the eye is now ready for intraocular lens implantation.
Today's IOLs are made of very soft, flexible polymers, so they can be folded in order to be placed through the very small corneal incision directly into the capsular bag. The lens is supported in the capsule by the flexible haptics.
The surgeon does a final check to make sure the lens is in good position. The wound is tested to ensure that it is watertight, and the lid supporting speculum is removed. Immediately following the treatment, the patient is monitored in the post operative holding area and finally discharged.
Posted on 13 March 2012 | 11:13 am
A recent literature review examining the common characteristics between Alzheimer's disease and age-related macular degeneration (AMD) indicates that the 2 diseases may share a common pathogenic mechanism and suggests that therapeutic approaches applied to patients with Alzheimer's may offer some benefit to those with AMD. The review focused on amyloid beta, an amino acid peptide found in both senile plaques of Alzheimer's patients and the drusen of patients with AMD. Specifically, the review looked at the role the peptide plays as a regulator in the progression from drusen to AMD.
"Age is a common risk factor for Alzheimer's disease and age related macular degeneration," wrote study author Ohno-Matsui from Tokeyo Medical and Dental University, Japan (Prog Retin Eye Res 2011). Studies indicate the "long-term course of developing Alzheimer's disease pathology appears quite similar to the long term and progressive development of AMD. These data support the idea that the retina is a part of the brain, and pathological ageing changes occur in the brain and the retina similarly."
Ohno-Matsui suggested that similar therapies, including anti-amyloid therapies, including anti-amyloid therapies, might be successfully used to treat both groups of patients. Amyloid beta-targeting drugs originally developed to treat Alzheimer's are expected to be tested in patients with AMD, and pharmaceutical companies are currently developing genetically based and complement-targeted therapies with the goal of reducing complement-related AMD disease processes. These include therapies targeting C3-convertase, long implicated in the Alzheimer's disease pathogenesis.
"Although AMD should be considered as a distinct type of 'amyloid disease,' amyloid beta targeting therapies that are being tested in Alzheimer's patients can be applied to AMD," Phno-Matsui said. "Te reverse should also be considered i.e., therapies tested for AMD should also be tested on Alzheimer's disease patients."
Posted on 7 February 2012 | 3:15 pm
A retrospective review compiled by Orucoglu et al from Hadassah - Hebrew University Medical Center, Israel (I Refract Surg 2011), indicates that laser refractive surgery may be a good option for patients with mild-to-moderate amblyopia from anisometropic myopia, where one eye has a greater degree of myopia than the second eye. Amblyopia, or "lazy eye," is the most common cause of unilateral visual impairment in adults. Laser surgery is the procedure most often performed to correct adult ametropia, including mildly amblyopic eyes in the absence of organic disease.
The study assessed the amblyopic eyes of 30 patients. At the conclusion of their review, the authors found that in amblyopic eyes, the best spectacle-corrected visual acuity (BSCVA)
- improved >= 1 line in 16 eyes (53.3%), with a maximum improvement of 4 lines
- remained unchanged in 10 eyes (33.3%)
- decreased by 1 or 2 lines in 4 eyes (13.3%) In the fellow nonamblyopic eyes, the best-corrected visual acuity (BCVA)
- improved by 1 or 2 lines in 9 eyes (30.3%)
- remained unchanged in 16 eyes (53.3%)
- decreased by >=1 line in 5 eyes (16.7%)
The gain of lines of BCVA was significantly greater in the amblyopic eyes group compared with the nonamblyopic eyes. In addition, laser refractive surgery was effective and safer in amblyopic eyes to correct myopia. "In our series, gain in BSCVA after refractive surgery in amblyopic eyes was significantly higher than fellow nonamblyopic eyes," the authors wrote. "We demonstrated that laser refractive surgery was safe and effective in mild-to-moderate adult amblyopic eyes."
Posted on 24 January 2012 | 4:09 pm
A recent study conducted by Wolffsohn et al from Aston University United Kingdom (J Cataract Refract Surg 2011), revealed that even small amounts of uncorrected astigmatism in post-cataract-surgery patients can have a significant effect on vision quality and if left untreated, can affect the quality of life of older patients. Uncorrected astigmatism may also contribute substantially to falls among the elderly, the study noted.
Approximately 85% of the general population has corneal astigmatism and 20%-30% of those >60 years of age have significant astigmatism. Because cataracts and astigmatism with intraocular lenses (IOLs) offers a viable solution to both cataracts and astigmatism, but many patients do not choose IOLs to correct astigmatism due to added cost.
"Many public health services consider intraocular lenses that correct astigmatism to be premium," the authors noted. "Therefore, older patients with coexisting cataract and astigmatism must pay for the IOL as well as the cost of private surgery if they wish to achieve optimum vision."
The study assessed whether leaving patients with uncorrected astigmatism after cataract surgery had an impact on visual acuity and reading speed also decreased with increasing uncorrected astigmatism power. Light scatter was not significantly affected by uncorrected astigmatism; however, the reliability and variability of measurements decreased with increasing uncorrected astigmatic power. Driving simulator performance was unaffected by uncorrected astigmatism, although clarity decreased with increasing uncorrected astigmatic power.
"With modern IOLs implanted after cataract surgery, astigmatism can easily be corrected and the additional cost of these 'premium' IOLs is likely to be far less than the consequences of leaving the patient with uncorrected astigmatism," the authors noted. "Hence, correction of corneal astigmatism during cataract surgery and IOL implantation should be considered the standard of care."
Posted on 10 January 2012 | 3:36 pm
Cataract surgery poses no greater risk of ocular complications for patients in their 90s than those in their 80s, according to a recent study of patients treated within the U.S. Veterans Health Administration (VHA). The study, conducted by Tseng et al from the VA Medical Center, Rhode Island (Ophthalmology 2011), used data from the National Patient Care Database to compare surgical complication rates of 554 nonagenarians and 11,407 octogenarians who received cataract surgery in the VHA. The authors collected patient demographics and preoperative systemic and ocular comorbidities, and evaluated both intraoperative complications and 90-day postoperative complications.
A previous study of 45,000 veterans undergoing cataract surgery in the VHA, which evaluated a comprehensive list of comorbidities and ocular complications, found that patients aged >= 80 years were at increased risk for ocular complications after cataract surgery. This study sought to determine whether patients at the higher end of the age spectrum - those in their 90s - were at greater risk for complications than were patients in their 80s.
For both age groups in this study, diabetes mellitus was the most common systemic comorbidity and age-related macular degeneration the most common ocular cormorbidity. The study showed that while octogenarians had a higher prevalence of systemic comorbidities overall, nonagenarians were more likely to experience ocular comorbidities.
In both age groups, the most common intraoperative and postoperative complications were vitreous loss or posterior capsular tear and posterior capsular opacification. The authors noted that within this VHA study population, the risk of having any intraoperative or postoperative complication was 13.5% for octogenarians and 13.4% for nonagenarians.
"This study was not designed to determine criteria for selecting nonagenarians for cataract surgery," the authors wrote. "However, once the decision has been made to proceed with surgery, [these data] may inform cataract surgeons and their nonagenarian patients regarding the risk of experiencing an ocular complication." Additional studies are needed to assess how nonagenarians are selected for cataract surgery and to evaluate visual function and quality of life in these patients, the authors added.
Posted on 4 January 2012 | 3:53 pm
The accommodating style IOLs are actually able to flex in response to the ciliary muscle contracting – in a manner similar to how a natural lens would change shape in the younger eye. Very slight motion and flexing of the lens allows the eye to gain more “power” when a patient focuses from distant to near objects.(Figure 5 A & 5 B) The other mechanism by which an intraocular lens may replace the loss of accommodation is through multifocal optics. The multifocal system has a modified optic (lens portion of the IOL) which is able to modify the light entering the eye and focus some light for near visualization and another portion focuses the energy to allow visualization of distant images. Simply speaking, the multifocal implants, apportions the light to different focal lengths so different distances are in focus; this occurs without effort from the patient and is a totally passive system. Thus, patients do not have to worry about looking through a certain portion of their implant to see at a specific distance. In summary, advances in cataract surgery and its outcomes have gone hand-in-hand with the evolution of intraocular lenses. The latest quantum leap in IOL technology is the introduction of presbyopic intraocular lenses. Unlike standard monofocal IOLs, these lenses restore the eye’s ability to have a range of clear vision.
Posted on 28 December 2011 | 11:04 am
Children between the ages of 3 and 5 years should be seen at least once by an eye care professional to detect the presence of amblyopia or its risk factors, according to an updated statement issued by the U.S. Preventive Services Task Force (USPSTF). The 2011 recommendation was made following an initiative undertaken by the USPSTF to update 2004 statement offering guidelines for vision screening in young children.
The USPSTF reviewed multiple studies that evaluated the accuracy and outcomes of preschool vision screening tests. They also assessed the effectiveness of early detection and treatment and the harm of screening treatment.
The researchers found that vision screening tools used to assess preschool-age children accurately detected visual impairment, such as
- refractive errors
- strabismus
- amblyopia
The task force determined that early treatment for amblyopia in children 3 to 5 years of age, including the use of cycloplegic agents, patching and eyeglasses, leads to improved visual outcomes. The 2004 Guidelines also recommended vision screening for children between 3 and 5 years of age; this review reconfirmed those recommendations based on updated evidence. According to the statement, there is "adequate evidence that early treatment for amblyopia...for children 3 to 5 years of age leads to improved visual outcomes."
Posted on 19 December 2011 | 11:54 am
In the United States, men are 3x more likely to suffer an eye injury, according to the Eye Injury Snapshot, and annual survey conducted by the American Academy of Ophthalmology (AAO) and the American Society of Ocular Trauma (ASOT). Conducted during a 1-week period in the spring of 2010, the survey revealed that men suffered about three-quarters (73.5%) of all reported eye injuries, and the survey also found that most of the total eye injuries suffered occurred at home, while doing chores or playing sports.
The AAO and the ASOT collected eye injury data each year to help increase public awareness and to encourage behavior that can help circumvent eye injuries. The Eye Injury Snapshot survey also found the following:
- One quarter of eye injuries that occur at home resulted from play/sport activities
- One quarter occurred during home repair work or while using power tools.
- Most home-based eye injuries occurred in the yard or garden
- About 50% of reported injuries occurred in men and women 30-64 years of age; children < 12 years of age accounted for about 12% of injuries.
- Almost half of eye injuries occurred between noon and 7:00 pm.
To prevent some of the most common eye injuries that happen during household chores and repairs, the AAO and the ASOT recommend that every household have at least one pair of protective eyewear approved by the American National Standards Institute (ANSI). ANSI-approved eye wear is available at most hardware and home improvement stores and can be identified by the mark "Z87". For sports activities, eye wear approved by the American Society for Testing the Materials is recommended. To locate Appropriate eyewear for specific sports, the AAO and the ASOT suggests that clinicians tell their patients to talk to their ophthalmologists or visit the AAO Web site, www.geteyesmart.org.
Posted on 21 November 2011 | 2:44 pm
Despite data linking prolonged statin use with cataract development, a recent study shows that patients with diabetes who take statins for a long period of time have no greater risk of developing cataracts than patients who have not taken prolonged coursed of statins. Conducted by Hermans et al from Cliniques Universitaires St. - Luc, Belgium (Diabetes Metab, 2011), the analysis studied 780 patients with type 2 diabetes (T2D) at very high risk for diabetic retinopathy (DR) and cataract, and determined that chronic statin therapy was neither cataractogenic nor was cataract presence associated with increased use of statin or other lipid-lowering drugs.
According to the authors, studying patients with T2D offers "an ideal condition in which to assess the potential beneficial/detrimental effects of satins or other lipid-lowering drugs (LLD) on cataract, because T2D patients have a high prevalence of atherogenic dyslipidaemia as part of the associated metabolic syndrome, and also exhibit an increased incidence/prevalence of both hyperglycaemia and age-related cataracts(s)."
Major risk factors for cataract in T2D patients include hyperglycemia, diabetes duration and the presence of DR. Additionally, the study noted that certain risk factors or markers may differ according to cataract subtype; for example, smoking is associated with nuclear opacities, ultraviolet radiation increase the risk for cortical opacities, and high blood pressure and corticosteroids raise the odds for subcapsular cataract.
The diagnosis of cataract was made by an ophthalmologist in 16.8% of the study population during annual or biannual retinal checkups. Lens extraction was considered a surrogate for cataract prevalence in patients who had undergone prior lens surgery for cataract. Both age and duration of diabetes were significantly higher in the group with cataracts compared with those without. DR was diagnosed in 23% of the patients. According to the researchers, the "benefits of statin therapy in T2D may far outweigh any potential ocular drawbacks as a side effect which, in any case, were not supported by our findings."
Posted on 7 November 2011 | 5:36 pm
Despite an association between increased ocular perfusion pressure (OPP) and glaucoma, increasing blood pressure in an effort to modulate OPP appears to offer no value for treating glaucoma, according to a study published in a 2010 issue of the American Journal of Ophthalmology. Caprioli and Coleman from the Jules Stein Eye Institute at the University of California, Los Angeles, conducted the study, which reviewed current literature and presented the findings of the Blood Flow in Glaucoma Discussion Group.
"There is currently no evidence that manipulation of blood pressure or blood flow improves outcomes in glaucoma," the authors wrote. "Although low OPP is now an established risk factor in glaucoma, is is not clear whether it is truly independent of the sum of 2 separate risk factor-high [intraocular pressure] and low blood pressure."
While in theory, controlling OPP via blood pressure may seem appealing, modulating OPP in practice is complicated by a range of factors, including the potential for inaccuracy in OPP measurements, the authors noted. OPP measured during a routine examination may vary significantly from a patients physiologic OPP and therefore may not accurately correlate with the perfusion of the optic nerve head.
The authors added that there is currently little evidence to identify which vascular beds are important in the development and prevention of glaucoma, and therapies not targeted to those beds could cause an unwarranted increase in overall pressure and an attendant increase in morbidity and mortality. "There is the possibility that improving optic nerve perfusion by diverting blood from elsewhere (such as retinal capillary beds) may have unforeseen adverse effects, " they wrote.
While future drugs developed to target specific pathways or receptors may offer hope for treatment of glaucoma via OPP modulation current evidence does not support such treatment. "Glaucoma is a heterogeneous group of related diseases," the authors noted. "There may be subgroups of patients in whom vascular factors are important, (but) those patients subgroups have not been well identified."
Posted on 17 October 2011 | 3:52 pm
The use of oral antiviral medications in patients with herpes simplex virus (HSV) appears to help decrease the risk of recurrence of epithelial keratitis, stromal keratitis, conjunctivitis, and blepharitis, and may decrease the risk of vision loss in these patients, according to a retrospective study conducted by Young et al from Mayo Clinic, Minnesota. The results of the study were published in a 2010 issue of the Archives of Ophthalmology.
In the study, researchers reviewed the outcomes of 394 residents of Olmsted County, Minnesota, diagnosed with ocular HSV from 1976 through 2007, and compared the frequency of recurrence and adverse outcomes such as vision loss or need for surgery, among patients treated prophylactically with oral antiviral medication and those who did not receive oral antiviral medication. According to their data, the authors found that patients who were not being treated prophylactically were
- 9.4 x more likely to have a recurrence of epithelial keratitis
- 8.4 x more likely to have a recurrence of stromal keratitis
- 34.5 x more likely to have a recurrence of blepharitis or conjunctivitis
Of the 20 patients included the study who experienced adverse outcomes, 17 were not being treated with oral antiviral medications immediately prior to the adverse event.
HSV is a common cause of corneal disease, and recurrence is relatively common. Following initial exposure and primary systemic infection, HSV establishes a latent infection in the trigeminal or other sensory ganglia, disease may recur in one or both eyes, with the risk of recurrence significantly increasing over time. The cumulative effect of these reactivations may lead to stromal inflammation or neurotrophic keratitis, resulting in scar of perforation, the authors noted.
"The results of this study suggest that oral antiviral prophylaxis should be considered for patients with frequent recurrences of corneal disease," the authors concluded. "Additionally, we recommend an evaluation of possible barriers preventing compliance with antiviral prophylaxis and a reassessment of the cost-effectiveness of long-term oral antiviral therapy."
Posted on 12 October 2011 | 3:36 pm
10/3/11
Finding the Causes of Pediatric Cataracts
Although approximately 200,000 children worldwide are bilaterally blind from cataracts, the causes of the majority of cases remain undetermined, making prevention often problematic. A retrospective study of pediatric cataracts by Lim et al from the Hospital for Sick Children, Canada, indicates that, although the cause remains unclear in many instances, understanding associated and potential contributing factors can be a powerful tool in both treatment and diagnosis of the condition.
"Data on the characteristics of pediatric cataracts are useful for the purpose of diagnosis, genetic counseling, and selection of treatment options," the aauthors wrote in a 2010 issue of the American Journal of Ophthalmology. "Prevention strategies also require information about etiology."
The authors reviewed 1122 eyes of 778 consecutive patients suffering from cataract. About a third of syndrome-associated cataracts occurred in patients with Down syndrome. Posterior subcapsular cataract was the most common morphologic type, and more than half of all patients presented with unilateral cataracts. Almost 13% of patients examined had developed cataracts as the result of trauma, and almost 12% of cases had genetic origins. Although the most common systemic association involved diseases treated with steroids, about 58% had no clear etiology.
"Slightly over half of our patients had cataracts of unknown etiology despite examinations of their parents and siblings and, where indicated, laboratory investigations," the authors noted. "Idiopathic cataract is a diagnosis of exclusion. A metabolic and genetic examination tailored, with the assistance of a pediatrician, according to the medical and developmental history may be indicated when there are no other clear etiologic factors." The authors added that while steroid use is clearly established a relationship between the incidence of cataracts and the dosage or duration of steroid therapy."
Posted on 3 October 2011 | 2:18 pm
The advertised cost of laser vision correction is noted to have a wide variation. The operative word in the preceding sentence is ADVERTISED. In this volatile economy, many providers have been advised to advertise price point as an inducement to get their phones to ring. Almost without exception, these practices engage in a “bait and switch” technique to “up sell” the prospective patient. Indeed, one study demonstrated that patients who presented to discount chains advertising “LASIK for $599” actually ended up paying an AVERAGE of $1,800 per eye!
It has always been my practice philosophy to avoid selling patients a procedure. We have set pricing and recommend the optimal procedure for an individual’s eyes. My practice has built its reputation on delivering optimal results – we will recommend the procedure that will provide you with the best possible vision, and in some cases the recommendation may be not to have any treatment at all…
Laser vision correction is an important and exciting step in your life, it should not be an experience focused on upgrades and negotiation.
Posted on 10 March 2009 | 2:02 pm
Patients are often surprised to learn that some providers utilize a blade during a LASIK procedure. The blade is used during creation of the protective flap, and is incorporated into a device called the microkeratome. The microkeratome is analogous to a miniature carpentry plane which passes over the surface of the eye and creates the flap. The flap is then lifted and the laser is applied to the exposed area.
Review of the literature shows that while bladed LASIK is generally safe, most complications that did occur were associated with bladed flap creation.
No Blade LASIK avoids microkeratome- related complications. Instead of a stainless steel blade, the flap is created by a femtosecond laser, an ultra-fast, highly precise system which places millions of laser spots at a precise depth underneath the surface of the eye. The femtosecond laser I have used since 2003 is the IntraLase laser. Because the laser is computerized, the surgeon has the ability to customize the flap contour and dimensions to tailor each treatment. The unparalleled precision of the femtosecond laser provides the patient with the highest level of safety.
At our center, following creation of the protective flap with the IntraLase, the patient is situated next to the Allegretto Eye-Q Laser. The Eye-Q system then performs the actual cornea modeling that corrects the patient’s vision.
Thousands of patients (including yours truly) have benefited from the precision and accuracy of our No Blade LASIK technology. Unlike bladed LASIK performed at discount LASIK providers, this technique requires the surgeon to be skilled in the use of two advanced laser systems to provide you with the clearest vision possible.
Posted on 10 March 2009 | 2:00 pm
Using your Flex Spending Account (FSA), if available through your workplace, can help save up to 30% off your procedure as pretax income is used. A few tips if considering payment for your lasik using an FSA.
Be 100% certain that you are a candidate before setting aside the money. A complete preoperative exam is the only way to be sure.
Companies either issue a reimbursement check after the procedure or a Visa/Master Card to present at the time of payment.
A tool on the web that may help you plan your finances https://www.fsafeds.com/fsafeds/fsa_calculator.asp
Keep in mind that detailed questions on your FSA accounts are best answered by your human resource department.
Posted on 10 March 2009 | 1:57 pm
LASIK is the most commonly performed elective procedure in the United States. Patients frequently as me how LASIK works. The best way to describe the procedure is to begin by explaining the eye's optical function. It may help to refer to the diagram of the eye in our animation below.
The eye can be compared to a camera. Light passes through two light bending surfaces, the cornea, or the outer window, and the internal crystalline lens. In an eye with perfect vision, these two structures focus light precisely upon the retina (analogous to the film of a camera). When a patient needs glasses or contacts to see, they are dependent upon a third lens to bring light to focus on the retina. Laser vision correction works by enhancing the eyes optical status to decease the dependence upon an external lens - be it a spectacle or contact lens. The Allegretto Eye-Q laser is the world's most precise system that allows me to make subtle changes upon the outer window (cornea) and fine tune the focusing ability of the cornea to provide crisper, clearer sight.
Posted on 10 March 2009 | 1:53 pm
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