The human cornea is incapable of complete wound healing after LASIK surgery. In 2005, researchers at Emory University found permanent pathologic changes in all post-LASIK corneas examined, including undulation of Bowman's layer, spatial separation of the LASIK flap from the stromal bed, epithelial thickening over the wound margin, interface debris, and severed and severely disordered collagen fibrils. The study reveals that the healing response never completely regenerates normal corneal stroma.
Another study demonstrates that the LASIK flap produces a scar at the margin that is only 28.1% of the tensile strength of normal corneal stroma, and the flap itself heals to only 2.4% of normal tensile strength. This publication reports that one author has lifted LASIK flaps out to 11 years after initial surgery, further attesting to long-term weakness of the LASIK interface wound. Reports of late flap dislocations suggest that LASIK patients are vulnerable to traumatic flap injury for life.
Monday, August 23, 2010
IATROGENIC KERATECTASIA
The cornea is under constant stress from normal intraocular pressure pushing outward. Collagen bands of the cornea provide its form and biomechanical strength. LASIK thins the cornea and severs collagen bands, permanently weakening the cornea. This results in forward bulging of the posterior cornea, which may progress to a condition known as keratectasia, characterized by loss of best corrected vision and possible corneal failure requiring corneal transplant.
The FDA, laser manufacturers, and refractive surgeons are aware of limits on flap thickness, ablation depth, and diameter of the optical zone imposed by corneal biomechanics. When the FDA initially approved lasers for LASIK, it established a minimum of 250 microns of corneal tissue under the flap after LASIK surgery to prevent corneal instability and progressive forward bulging. Subsequent reports in medical literature indicate that 250 microns is not sufficient to ensure corneal biomechanical stability.20,21 In response, some surgeons stopped performing LASIK or raised the residual stromal thickness limit in their practices. However, the majority of surgeons continue to observe the 250 micron rule initially established by the FDA, even though this limit has been shown to be insufficient.
The 250 micron rule is often violated inadvertently during surgery, as microkeratomes that cut the LASIK flap are unpredictable and produce flaps of varying thickness.22 For this reason, flap thickness should be measured intraoperatively. Most surgeons have not incorporated this important measurement into the surgical procedure prior to ablation, which places patients with thicker-than-expected flaps at greater risk.
Keratectasia may develop months or years following seemingly successful LASIK.23 Since most cases are never reported, the true rate of this devastating complication may never be known. The only way to prevent surgically induced keratectasia is to abandon LASIK altogether. It is important to remember that LASIK is elective surgery. There is no sound medical reason to place patients at risk of vision loss from unnecessary surgery.
The FDA, laser manufacturers, and refractive surgeons are aware of limits on flap thickness, ablation depth, and diameter of the optical zone imposed by corneal biomechanics. When the FDA initially approved lasers for LASIK, it established a minimum of 250 microns of corneal tissue under the flap after LASIK surgery to prevent corneal instability and progressive forward bulging. Subsequent reports in medical literature indicate that 250 microns is not sufficient to ensure corneal biomechanical stability.20,21 In response, some surgeons stopped performing LASIK or raised the residual stromal thickness limit in their practices. However, the majority of surgeons continue to observe the 250 micron rule initially established by the FDA, even though this limit has been shown to be insufficient.
The 250 micron rule is often violated inadvertently during surgery, as microkeratomes that cut the LASIK flap are unpredictable and produce flaps of varying thickness.22 For this reason, flap thickness should be measured intraoperatively. Most surgeons have not incorporated this important measurement into the surgical procedure prior to ablation, which places patients with thicker-than-expected flaps at greater risk.
Keratectasia may develop months or years following seemingly successful LASIK.23 Since most cases are never reported, the true rate of this devastating complication may never be known. The only way to prevent surgically induced keratectasia is to abandon LASIK altogether. It is important to remember that LASIK is elective surgery. There is no sound medical reason to place patients at risk of vision loss from unnecessary surgery.
NIGHT VISION IMPAIRMENT
Millions of LASIK surgeries have been performed in the United States in the past decade. Many patients now suffer from visual impairment at night. Some patients, especially those with large pupils, are unsafe to drive at night and can no longer live normal, independent lives.
“When I drive to work every day, fighting the DC traffic I hear lots of great advertisements including the advertisements from the center that did my surgery talking about 95, 98 percent, whatever the percentage is of their patients who achieve 20/20 or 20/40 or better vision, and they consider that a success. I am considered a success by that criteria as well. However, in anything but extremely bright daylight I am visually impaired by starbursts, halos, multiple ghost images because of LASIK done on my 8-millimeter pupils…
FDA approval of devices should include not only approval within a certain range of myopia or astigmatism or hyperopia but within a range of pupil sizes such that any use of that device outside of that pupil size should be considered against the FDA approval of that device….”
LASIK patient, Mitch Ferro, testifying before the FDA Ophthalmic Devices Panel in July, 1999.
“When I drive to work every day, fighting the DC traffic I hear lots of great advertisements including the advertisements from the center that did my surgery talking about 95, 98 percent, whatever the percentage is of their patients who achieve 20/20 or 20/40 or better vision, and they consider that a success. I am considered a success by that criteria as well. However, in anything but extremely bright daylight I am visually impaired by starbursts, halos, multiple ghost images because of LASIK done on my 8-millimeter pupils…
FDA approval of devices should include not only approval within a certain range of myopia or astigmatism or hyperopia but within a range of pupil sizes such that any use of that device outside of that pupil size should be considered against the FDA approval of that device….”
LASIK patient, Mitch Ferro, testifying before the FDA Ophthalmic Devices Panel in July, 1999.
DRY EYE
A report by the American Academy of Ophthalmology published in 2002 states that dry eye is the most common complication of LASIK surgery.1 Refractive surgeons are aware that LASIK induces dry eye, yet patients are not fully informed as to the etiology, chronic nature and severity of this condition.
“My LASIK dry eye is not a minor problem, as downplayed by some ophthalmologists. It's a disability. I estimate that I am blind approximately 10 percent of the time due to my eyes being closed because of the pain. At the time of my surgery, I was told only a small number of patients experience a complication from this procedure. There is substantial evidence that shows this crippling side effect to be relatively common.” LASIK patient David Shell, testifying before the FDA Ophthalmic Devices Panel in August, 2002.
Persistent Dry Eye and Quality of Life after LASIK
Patients elect to undergo LASIK surgery with the expectation of improved quality of life. Instead, many are living with chronic pain from LASIK-induced dry eye. The FDA website states that dry eyes after LASIK may be permanent (http://www.fda.gov/cdrh/LASIK/risks.htm).
Patients should be informed that LASIK surgery severs corneal nerves that play a crucial role in tear production, and that these nerves do not return to normal. Inability to sense and respond to dryness may lead to ocular surface damage.
Medical Research on Duration and Severity of Dry Eye
Dry eye disease is a painful, chronic condition for some patients after LASIK surgery. In 2001, Hovanesian, Shah, and Maloney found that 48% of LASIK patients reported symptoms of dryness at least 6 months after surgery, including soreness, sharp pain and eyelid sticking to the eyeball.
A Mayo Clinic study published in 2004 demonstrates that 3 years after LASIK, corneal nerves are less than 60% of preoperative densities.
In 2006, researchers at Baylor College of Medicine reported the incidence of dry eyes six months after LASIK at 36% overall and 41% in eyes with superior-hinges. These findings were based on objective medical tests rather than patient questionnaires, which is significant as patients with nerve damage may not be capable of sensing dryness.
The scientific literature is replete with case reports and studies of LASIK-induced dry eye. This complication is widely recognized in the industry as the most common complaint of LASIK patients, yet the problem is downplayed in the informed consent process. Most dry eye therapies provide only marginally effective symptomatic relief. There is no cure for LASIK-induced dry eye. Internet bulletin boards with forums devoted to post-LASIK dry eye are a testament to this widespread, debilitating condition.
“My LASIK dry eye is not a minor problem, as downplayed by some ophthalmologists. It's a disability. I estimate that I am blind approximately 10 percent of the time due to my eyes being closed because of the pain. At the time of my surgery, I was told only a small number of patients experience a complication from this procedure. There is substantial evidence that shows this crippling side effect to be relatively common.” LASIK patient David Shell, testifying before the FDA Ophthalmic Devices Panel in August, 2002.
Persistent Dry Eye and Quality of Life after LASIK
Patients elect to undergo LASIK surgery with the expectation of improved quality of life. Instead, many are living with chronic pain from LASIK-induced dry eye. The FDA website states that dry eyes after LASIK may be permanent (http://www.fda.gov/cdrh/LASIK/risks.htm).
Patients should be informed that LASIK surgery severs corneal nerves that play a crucial role in tear production, and that these nerves do not return to normal. Inability to sense and respond to dryness may lead to ocular surface damage.
Medical Research on Duration and Severity of Dry Eye
Dry eye disease is a painful, chronic condition for some patients after LASIK surgery. In 2001, Hovanesian, Shah, and Maloney found that 48% of LASIK patients reported symptoms of dryness at least 6 months after surgery, including soreness, sharp pain and eyelid sticking to the eyeball.
A Mayo Clinic study published in 2004 demonstrates that 3 years after LASIK, corneal nerves are less than 60% of preoperative densities.
In 2006, researchers at Baylor College of Medicine reported the incidence of dry eyes six months after LASIK at 36% overall and 41% in eyes with superior-hinges. These findings were based on objective medical tests rather than patient questionnaires, which is significant as patients with nerve damage may not be capable of sensing dryness.
The scientific literature is replete with case reports and studies of LASIK-induced dry eye. This complication is widely recognized in the industry as the most common complaint of LASIK patients, yet the problem is downplayed in the informed consent process. Most dry eye therapies provide only marginally effective symptomatic relief. There is no cure for LASIK-induced dry eye. Internet bulletin boards with forums devoted to post-LASIK dry eye are a testament to this widespread, debilitating condition.
Sunday, March 21, 2010
Non-vision-threatening side effects
I understand that these conditions usually occur during the normal stabilization period of from one to three months, but they may also be permanent requiring chronic care or additional surgery:
1. Increased sensitivity to light, glare, and fluctuations in the sharpness of vision; eye irritation related to drying of the corneal surface; overcorrection or under correction causing nearsightedness or increase in astigmatism and that this could be either permanent or treatable;
2. Glare, a “starbursting” or halo effect around lights, or other low-light vision problems that may interfere with the ability to drive at night or see well in dim light. For most patients, this is a temporary condition that diminishes with time or is correctable by wearing glasses at night or taking eye drops. For some patients, however, these visual problems are permanent.
1. Increased sensitivity to light, glare, and fluctuations in the sharpness of vision; eye irritation related to drying of the corneal surface; overcorrection or under correction causing nearsightedness or increase in astigmatism and that this could be either permanent or treatable;
2. Glare, a “starbursting” or halo effect around lights, or other low-light vision problems that may interfere with the ability to drive at night or see well in dim light. For most patients, this is a temporary condition that diminishes with time or is correctable by wearing glasses at night or taking eye drops. For some patients, however, these visual problems are permanent.
Saturday, March 20, 2010
Other Advances in Refractive Surgery
The eye’s optical system creates a limit as to how wide and deep the laser ablation should be, i.e., the wider the ablation, the deeper the laser must ablate into the cornea, which may result in delayed healing and prolonged visual recovery. The development of new lasers allows the creation of a wider ablation zone while removing the least amount of tissue. Studies have shown that this reduces problems with night vision and other side effects associated with laser refractive surgery.
Wavefront LASIK
Eye care specialists have traditionally used standard measurement techniques that identify and correct lower-order aberrations, such as nearsightedness, farsightedness, and astigmatism. However, no two
people share the same eye irregularities or have similar refractive needs. Vision is unique and as personal as fingerprints or DNA.
Wavefront technology allows eye surgeons to customize the LASIK procedure for each eye, providing the possibility of even better vision. The FDA approved the first system for general use in October 2002.
A laser beam is sent through the eye to the retina and is reflected back through the pupil, measuring the irregularities of the light wave (wavefront) as it emerges from the eye. This process produces a three dimensional map of the eye’s optical system.
Measuring the cornea’s imperfections or aberrations in this way allows the refractive surgeon to develop a personalized treatment plan for the patient’s unique vision needs. Correcting the patient’s specific imperfections can result in sharper vision, better contrast sensitivity, and reduces problems associated with higher-order aberrations after surgery, such as haloes and blurred images. Studies indicate that 90-94% of patients receiving wavefront LASIK achieved visual acuity of 20/20 or better. However, those with thin corneas, high degrees of aberrations, severe dry eyes, or conditions affecting the lens and vitreous fluid inside the eye may not be good candidates for wavefront LASIK.
people share the same eye irregularities or have similar refractive needs. Vision is unique and as personal as fingerprints or DNA.
Wavefront technology allows eye surgeons to customize the LASIK procedure for each eye, providing the possibility of even better vision. The FDA approved the first system for general use in October 2002.
A laser beam is sent through the eye to the retina and is reflected back through the pupil, measuring the irregularities of the light wave (wavefront) as it emerges from the eye. This process produces a three dimensional map of the eye’s optical system.
Measuring the cornea’s imperfections or aberrations in this way allows the refractive surgeon to develop a personalized treatment plan for the patient’s unique vision needs. Correcting the patient’s specific imperfections can result in sharper vision, better contrast sensitivity, and reduces problems associated with higher-order aberrations after surgery, such as haloes and blurred images. Studies indicate that 90-94% of patients receiving wavefront LASIK achieved visual acuity of 20/20 or better. However, those with thin corneas, high degrees of aberrations, severe dry eyes, or conditions affecting the lens and vitreous fluid inside the eye may not be good candidates for wavefront LASIK.
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