Prior to the advent of laser technology, ophthalmologists relied purely on mechanical means of surgically correcting myopia (nearsightedness), hyperopia (far sightedness), and astigmatism.
Automated Lamellar Keratectomy is a procedure through which an automatic apparatus called a microkeratome slices an extremely thin layer of tissue from the surface of the cornea in order to alter the refractive index of the ocular lens. In the case of nearsightedness, the surgeon thins the cornea, while to correct farsightedness, he first elevates the outermost layer and then supplements the natural thickness of the lens by inserting tissue from a donor cornea.
A modicum of success was achievable through mechanical means, but the extraordinary precision necessary to perform precise alterations and the jelly-like consistency of corneal tissue below the surface layer required the development of laser technology which has revolutionized ophthalmology since its introduction.
Modern laser techniques include Photorefractive Keratectomy (PRK), in which the surgeon alters the thickness of the cornea through "ablation," or the removal of tissue in order to alter its refractive index. Laser-Assisted in Situ
Keratomileusis (LASIK) and recent variations thereof is the preferred method for suitable candidates, while Laser Epithelial Keratomileusis (LASEK) is the option for patients whose corneal thickness is insufficient for LASIK procedures.
Millions of patients have undergone laser eye surgery since its introduction, and the vast majority of them report profound satisfaction with their results, specifically, at being able to see well without glasses or contact lenses. (1)
Surveys of patients indicate that among the other most often cited benefits are increased confidence in personal appearance, improved ability to participate in contact sports, and simply being able to see upon waking up in the morning. The latest procedures have achieved a remarkable ability to correct vision, with upwards of ninety-percent of patients of some procedures enjoying restored vision of 20/20, with many even surpassing the 20/20 standard.(2)
Purely mechanical means have largely been replaced by laser procedures because they offer such unparalleled precision, as well as increased comfort and faster recuperation. In the hands of qualified ophthalmologists, all laser eye surgery is relatively safe, but like all surgical procedures, there are certain risks and potential complications inherent to the use of lasers in eye surgery. These can be minimized to large degree by careful patient selection and through application of procedures most appropriate to individual cases. More often than not, even those relatively rare incidents of unsatisfied patients reflect unrealistic pre-operative patient expectations, rather than technical or procedural failure. Therefore, ophthalmologists have learned to minimize patient frustrations by educating prospective patients as to the limitations and possible complications currently associated with laser eye surgery.
1. Maloney R, MD, Kraff C, MD, Colberston W, MD, O'Brien T, MD, Koch D, MD. Multicenter Trial of Wavefront-Guided LASIK ASCRS/ASOA Annual Symposium & Congress, San Francisco, April 2003.
2. Slade SG, MD, U.S. Clinical Trial of LASIK for Myopia with the Zyoptix System: Efficacy Assessment and Patient
Satisfaction ASCRS/ASOA Annual Symposium & Congress, San Francisco, April 2003.
significant category of post-operative complications relates to proper patient screening and procedure selection. Since many of the dangers and particular post- operative complications inherent in laser eye surgery vary directly as functions of prospective patient suitability, an outline of established criteria for patient selection is central to the analysis of possible risks and relative dangers associated with laser eye surgery.
Generally speaking, there are three main categories of prospective patients with respect to LASIK surgery. Predictably, statistics related to surgical error and post-operative complications and failures are markedly different where physicians adhere rigidly to accepted medical criteria delineating ideal patient candidates from less than ideal candidates, and where inappropriate candidates are preemptively excluded from any attempted laser surgery procedures.
Regardless of candidate criteria, there are certain risks and limitations inherent in laser eye surgery, even in the most optimistic scenarios. Therefore, it is always imperative -- both ethically, as well as a practical matter -- that patients be fully and completely informed that certain aspects of their vision might deteriorate as a consequence of (even) successful surgery, and that complete recuperation may take six months or more.
Ideal Prospective Patients for Laser Sugery:
Ideal prospective patients are older than eighteen years of age, because their eyes are no longer growing and changing in shape, and the problems for which they seek treatment fall within the category of pathology for which LASIK procedures are most appropriate such as myopia, hyperopia, and/or astigmatism. Within each different problem, there also exists an appropriate range of visual acuity defining ideal prospective candidates: namely, myopia no greater than minus-12 diopters, hyperoptia no greater than plus-6 diopters, and astigmatism no greater than 6 diopters.
Irrespective of age, another indication of stability concerning eye shape and size is the maintenance of the same contact lens prescription (or glasses) for at least two years.
Since the LASIK procedure employs a corneal flap technique, it is crucial that the corneal tissue thickness of a prospective patient be sufficient for the surgical creation of a flap appropriate in depth to ensure success of the procedure. Therefore, ideal candidates are those with relatively thick corneas.
Ideal candidates do not suffer from eye disease or from any other disease or autoimmune disorders that might delay or retard surgical healing or resistance from infection. Similarly, ideal candidates for laser surgery are not taking any medications that increase bleeding or edema. Finally, it is highly desirable that prospective patients fully understand the nature of their eye problems and the degree to which those issues are reversible through laser surgery, as well as the likelihood and nature of post- operative recuperative delays and residual vision problems and limitations.
Less Than Ideal Candidates:
Certain prospective laser surgery patients are suitable candidates, but not at the time of their first consultation. Included within this category are prospective patients younger than eighteen, or whose vision has not remained stabilized by virtue of any other factor, regardless of chronological age. Prospective patients should not be pregnant or nursing at the time of surgery, nor should a patient be considered who has had an active case of ocular herpes, or been diagnosed with ocular herpes within one year of laser surgery.(3)
3. Carr JD, Nardon R. Jr., Stulting RD, et al. Risk Factors for Epithelial Complications after LASIK. Invest Ophthalmol Vis Sci 1997;28(4):S232.
Additionally, the technical specifications of surgical laser equipment is still evolving, so some prospective patients whose visual acuity lies outside current acceptable parameters of available technology are not suitable candidates at the time of their initial consultation, but will be ideal candidates in the near future as physicians become able to treat more serious corneal deformities.
Prospective patients with scarred corneas are not necessarily precluded from consideration, but they represent a challenge to the skill and experience of the surgeon. Similarly, prospective patients suffering from autoimmune diseases, or taking medications that compromise their relative recuperative ability might be appropriately and safely treated, provided more stringent measures are taken with respect to monitoring their post surgical progress. The final consideration in this category are patients with a previous history of any condition such as dry eyes that is reliable predictor of post-surgical conditions about which they must be fully informed, primarily so that their expectations prior to laser surgery comport with the realities and possible limitations of the anticipated surgical outcomes.
Certain prospective patients are absolutely precluded from consideration for laser eye surgery because prior experience and statistical data have established that laser surgery is not sufficiently likely to improve their vision. In many cases, treating these patients is an ethical violation owing to the unacceptable risk of irreversible injury to their eyes.
Prospective patients suffering from glaucoma, corneal disease such as advanced cataracts, or whose corneal tissue is inherently too thin for the safe application of laser surgical techniques are absolutely precluded from consideration for laser surgery.
Since LASIK surgery can permanently effect depth perception, certain individuals will be precluded from consideration simply by virtue of their lifestyle or vocation. Military pilots represent one example of prospective patients who are not appropriate candidates for certain laser procedures, as are mountain climbers and deep-sea divers, by virtue of their need for accurate depth perception as well as their exposure to extreme variations in atmospheric pressure that could temporarily compromise their vision or even result in permanent blindness in extreme cases.
Post-Surgical Complications and Associated Risks:
Laser surgery was specifically developed in order to minimize the tissue trauma associated with eye surgery, and it is designed to allow the physician a greater degree of surgical precision than possible with a microkeratome. Nevertheless, even the most precise laser surgery still entails incisions (and excisions) of living tissue that requires time to heal properly.
Among the many issues that contribute to surgical healing, some require prudence on the part of the patient and diligence on the part of the surgeon, while others are strictly subject to the overall health and physical condition of the patient as well…