Ophthalmol Clin North Am
· 2003 Sep · PMID 14564754
The experience with the complications associated with extended wear contact lenses has made practitioners and patients fearful of this modality. Today, strong scientific evidence suggest that the hypoxia problems associa...The experience with the complications associated with extended wear contact lenses has made practitioners and patients fearful of this modality. Today, strong scientific evidence suggest that the hypoxia problems associated with extended wear lenses have been solved. Good clinical evidence suggests that the new high-Dk silicone lenses are safe and can be worn successfully for up to 30 days. Patients can now be offered contact lenses that meet their desire of continuous vision; however, practitioners and patients must be instructed regarding the signs and symptoms of contact lens complications. Practitioners need to be educated in the diagnosis and management of the complications. Patients need to be educated about the need for proper eye care, contact lens care regimens, and appropriate follow-up visits.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809164
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Visual function declines with age in a variety of ways. It must also be kept in mind, however, that the results reported here are primarily group findings. When evaluating the performance of older persons, there is extre...Visual function declines with age in a variety of ways. It must also be kept in mind, however, that the results reported here are primarily group findings. When evaluating the performance of older persons, there is extremely wide variability, and even though average performance may decline as a function of age, many older adults maintain excellent visual function throughout their lifetimes. It is important to keep the variability of individual performance in mind to avoid ageist stereotypes. Although declines in age-related vision are well documented, it is less clear why these declines have occurred. Most recent studies have controlled for criterion differences by using forced-choice methods. These studies confirm that even after correcting for differences in threshold criteria, age-related declines persist. Many other studies have controlled for optical changes using a variety of techniques. Again, some age-related declines still exist Although it is widely believed that the neuroanatomy and physiology of the visual pathways are affected by aging, there is still relatively little understanding of how these changes impact visual function. Thus, there is a need for further studies to link potential neural mechanisms to observed changes in functional visual performance. Furthermore, there is also a possibility that there may be multiple sites of decline within a given person and that these sites of decline may vary across persons. Thus, the use of an individual-differences approach is needed to evaluate the many potential explanations for sensory decline. Finally, there is frequently a discrepancy between performance in the laboratory and real-world performance. In trying to predict the performance of real-world tasks and in designing the best environments for the elderly, sensory function should not be considered in isolation. Rather contributing factors such as cognitive ability, expectations, distractions, and other health-related and motor problems must also be considered. Traditional clinical measures of visual function, though appropriate for evaluating the presence of disease, are often inadequate in explaining everyday performance impairments. Thus, further research is needed to fully understand the complex interactions between sensory, cognitive, motor, economic, and physical factors that together determine one's level of ability or disability in everyday tasks.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809163
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In this article we have demonstrated the significant visual impairments in elders with good vision by standard measures when the viewing conditions are less than ideal--low contrast, low or changing light level, or glare...In this article we have demonstrated the significant visual impairments in elders with good vision by standard measures when the viewing conditions are less than ideal--low contrast, low or changing light level, or glare. Much of this impairment can be accounted for by the known age-related changes in the eye. We have emphasized that two people of the same age with the same standard acuity can have dramatically different vision under these nonideal conditions. Because one cannot predict vision under these conditions on the basis of standard acuity, it is important to use these additional measures. These other vision measures are more closely related to task performance (reading, face recognition) than standard acuity. We find that persons who perform poorly on these low-contrast measures are more likely to have significant losses of standard acuity in the future. Hence, these measures help identify persons who should be more closely monitored. Each of the vision functions shows significant decline across age. It is important to recognize that a 60-year-old with 20/30 acuity is different from an 80-year-old with the same acuity. The older person is more likely to be impaired under the conditions of daily life. Measurement and appreciation of visual function should allow better understanding of subjective visual symptoms and allow the clinician to offer appropriate advice for mitigating these impairments. Often simple interventions, such as correcting refractive error, improving lighting, avoiding large changes in light level, increasing contrast, and avoiding glare (perhaps through cataract surgery), can greatly improve not only vision function but quality of life. Many studies have reported that good vision allows for independent living, which is the goal for most elders.
Robbins SL, Christian WK, Hertle RW
… +1 more, Granet DB
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809162
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The goal of office testing of the child remains the same as it is for the adult--to gather as much information as efficiently as possible. Clinical testing of the child requires familiarity with the limitations available...The goal of office testing of the child remains the same as it is for the adult--to gather as much information as efficiently as possible. Clinical testing of the child requires familiarity with the limitations available tests. Perhaps most important is the ability choose the proper test to use at every development stage. Cooperation may be surprisingly good in to hands of experienced examiners, though very young children can be unpredictable. The general ophthalmologist should not fear having young patients but rather take joy in the interaction with them. Armed with as many tools as possible, the challenge of testing children can be converted to the reward of helping families.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809161
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Numerous electrophysiologic tests are available for use in the clinic. When properly recorded and analyzed, these tests provide important diagnostic and prognostic information about the site and nature of the disease pro...Numerous electrophysiologic tests are available for use in the clinic. When properly recorded and analyzed, these tests provide important diagnostic and prognostic information about the site and nature of the disease process. If the results from these tests are combined with psychophysical findings (color vision, acuity, visual fields), their usefulness in defining disease can be further extended.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809160
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Short-wavelength automated perimetry (SWAP) is a visual field test designed to assess the short-wavelength sensitive color system by isolating the blue-yellow pathway. SWAP is a powerful clinical tool able to detect visu...Short-wavelength automated perimetry (SWAP) is a visual field test designed to assess the short-wavelength sensitive color system by isolating the blue-yellow pathway. SWAP is a powerful clinical tool able to detect visual field deficits 3 to 5 years before standard automated perimetry (white-on-white) in most glaucoma patients, and progression of visual field defects up to 3 years earlier. SWAP deficits are predictive of the onset and location of future visual field loss, and they correlate well with structural damage associated with glaucoma. The main disadvantage of SWAP remains the longer testing time required. In the clinic, it is recommended that SWAP be performed on patients who are at higher risk for glaucoma. Although SWAP was originally developed to detect visual loss in glaucoma patients, it is also useful for patients with diabetic retinopathy and maculopathy, optic neuropathies, vision loss associated with HIV, migraine, and multiple sclerosis. More sensitive psychophysical tests of visual function, such as SWAP, can significantly shorten clinical trials and aid in the validation of new therapeutic approaches.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809159
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The FDT perimeter is a compact and relatively inexpensive perimeter whose transportability, tolerance to refractive errors, and rapid test times (less than 1 minute per eye) make it a suitable candidate for visual field...The FDT perimeter is a compact and relatively inexpensive perimeter whose transportability, tolerance to refractive errors, and rapid test times (less than 1 minute per eye) make it a suitable candidate for visual field screening. It is a uniform finding that the C-20-1 screening protocol of the FDT perimeter provides good sensitivity and specificity for the detection of moderate and severe losses in glaucoma. Sensitivity can be increased by use of the C-20-5 screening protocol. In addition, the FDT perimeter demonstrates good sensitivity and specificity for detecting the presence of neuro-ophthalmic disorders, though it may have a limited ability to determine whether a field defect is hemianopic. There is only limited evidence that the FDT can appropriately detect retinal disease. Despite some evidence that the current FDT perimeter may be suitable for staging and monitoring the progression of visual field damage, the large targets used in the test make this of limited practicability. The development of a frequency-doubling test with smaller targets spaced over narrower intervals would improve the ability of FDT perimetry to determine the spatial extent of visual field defects.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809158
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As distinguished from measuring the ability to see at the location where the eye's gaze is fixated, perimetry consists of determining the visual capabilities throughout the field of vision. Traditionally the ability to s...As distinguished from measuring the ability to see at the location where the eye's gaze is fixated, perimetry consists of determining the visual capabilities throughout the field of vision. Traditionally the ability to see a white object or a projected spot of white light is determined and quantified under standard conditions. Modern machines use automated methods to present spots of light in a programmed manner to determine the threshold of visual capability, and, after recording the data, these machines also apply statistical analyses of the results to assist the clinician in evaluation of the patient. New methods for testing particular aspects of visual function and analyzing the results are continuously under development.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809157
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Many visual disorders produce acquired color vision defects. Color vision theory emphasizes several stages of visual processing: prereceptoral filters (lens, macular pigment, pupil), cone photopigments (L-, M-, and S-con...Many visual disorders produce acquired color vision defects. Color vision theory emphasizes several stages of visual processing: prereceptoral filters (lens, macular pigment, pupil), cone photopigments (L-, M-, and S-cones), and postreceptoral processes (red-green, S-cone, and luminance channels). Congenital color defects, which affect 8% to 10% of males and 0.4% to 0.5% of females, result from alterations in the photopigment absorption spectra or the absence of one or more photopigments. The most common defects are color vision deficiencies (protan and deutan defects), which are milder than the rarer achromatopsias (complete loss of color vision). Acquired color vision defects can be attributed to a number of different causes: alteration of prereceptoral filters, reduced cone photopigment optical density, greater loss of one cone type than the others, and disruption of postreceptoral processes. Acquired color vision defects have been divided into three classes: type 1, red-green defect with scotopization; type 2, red-green defect without scotopization; and type 3, blue defects (with or without pseudoprotanomaly). Blue defects are usually type 3 acquired defects because congenital tritan defects have an incidence of one in several tens of thousands. Red-green defects can be acquired or congenital, and ruling out acquired defects can require a battery of tests (plates and arrangement tests, anomaloscopy, perhaps genetic analysis). Color vision tests must be administered carefully (with a standard illuminant and protocol), and pupillary miosis or high lens density should be noted and their possible effects considered when interpreting test results. Plate tests provide a simple screening method but do not provide a diagnosis. Arrangement tests and anomaloscope testing take more time and make greater demands on the tester, but they provide a more thorough evaluation. When standard protocols are followed and results are interpreted in terms of prereceptoral filters, photopigment optical density, cone loss, and disruption of postreceptoral processes, a battery of color vision tests can be useful in the differential diagnosis, after progression of the disease, and for evaluating the effectiveness of treatment.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809156
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Spatial contrast is a physical dimension referring to the light-dark transition of a border or an edge in an image that delineates the existence of a pattern or an object. Contrast sensitivity refers to a measure of how...Spatial contrast is a physical dimension referring to the light-dark transition of a border or an edge in an image that delineates the existence of a pattern or an object. Contrast sensitivity refers to a measure of how much contrast a person requires to see a target. Contrast-sensitivity measurements differ from acuity measurements; acuity is a measure of the spatial-resolving ability of the visual system under conditions of very high contrast, whereas contrast sensitivity is a measure of the threshold contrast fur seeing a target. Today the most common methods for measuring contrast sensitivity are chart-based systems that can be mounted on the wall. These charts use test targets that are either sine-wave gratings or letters. Which specific chart a clinician selects should be guided by his or her purpose in using contrast sensitivity for patient management. In the research setting, chart selection should rest on ensuring that the scientific aims of the study are met. Contrast-sensitivity tests can provide useful information by revealing in some conditions visual loss not identifiable through visual acuity tests, by providing another method of monitoring treatments, and by providing a better understanding of visual performance problems faced by persons with vision impairment.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809155
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Despite its critical importance to our daily life, the most common measurement of visual function, visual acuity, is a relatively crude and narrow one testing only a small portion of the broad range of visual functions....Despite its critical importance to our daily life, the most common measurement of visual function, visual acuity, is a relatively crude and narrow one testing only a small portion of the broad range of visual functions. Visual acuity is the measurement of the ability to discriminate two stimuli separated in space at high contrast relative to the background. Clinically, this is measured by asking the subject to discriminate letters of known visual angle. The visual acuity is represented as the reciprocal of the minimal angle of resolution (the smallest letters resolved) at a given distance and at high contrast. Other measurements of visual acuity also exist, including Vernier acuity. Newer charts, such as the ETDRS chart, use letters of equal recognition difficulty and use the log of the minimal angle of resolution; these charts have significant advantages over the old Snellen-type charts. This article reviews visual measurements in children and in patients with low vision, and it reviews factors affecting visual acuity, such as pupil size, refractive error, media opacities, and pharmacologic agents.
Ophthalmol Clin North Am
· 2003 Jun · PMID 12809154
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Examination of the pupil provides critical objective information that complements subjective visual measurements and can provide important clues for distinguishing among different etiologies of loss of visual function. A...Examination of the pupil provides critical objective information that complements subjective visual measurements and can provide important clues for distinguishing among different etiologies of loss of visual function. Although automated technologies and pupillary perimetry provide valuable insight into the correspondence between visual and pupillary dysfunction, a firm understanding of the principles of the afferent examination of the pupil is all that is required for the clinician to quickly obtain this objective measure of function during any routine examination.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683256
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Laser subepithelial keratomileusis (LASEK) has become a viable alternative to photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in selected patients. LASEK may decrease the complications associat...Laser subepithelial keratomileusis (LASEK) has become a viable alternative to photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in selected patients. LASEK may decrease the complications associated with PRK, including postoperative pain and slow visual rehabilitation. In this article, the authors present the visual outcomes and complication rates of LASEK based on the retrospective case review of 101 consecutive patients (163 eyes) treated with LASEK surgery over the past 6 years. Seventy-eight percent of these eyes showed complete epithelial healing by day 3, and there were no incidents of recurrent erosions. As with LASIK, the achieved correction for LASEK was greater than the treatment dose (requiring undercorrection nomogram adjustments). Mean logMAR UCVA was 0.03 (20/20) at 1 year. LASEK seems to be a safe and effective option for patients who request refractive surgery.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683255
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Lamellar refractive surgery has evolved into LASIK, which is a widely performed, versatile procedure with a high patient acceptance. In this chapter, the two main components of LASIK were discussed: flap creation and str...Lamellar refractive surgery has evolved into LASIK, which is a widely performed, versatile procedure with a high patient acceptance. In this chapter, the two main components of LASIK were discussed: flap creation and stromal ablation. In each of these areas, the authors explored current technology and new advances, including the femtosecond laser and wavefront-guided ablations. Expanded indications and therapeutic application of LASIK also have come to the forefront. The treatment of anisomyopic amblyopia in the pediatric population is a prime example and was discussed fully in this chapter. The field of refractive surgery has never been stagnant. Surgeons and scientists continue to explore new modalities to increase safety, to improve results, and to broaden applications that benefit the patient population.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683254
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The concept of selectively transplanting the corneal endothelium has been contemplated since the middle of the twentieth century. Procedures leading up to and including endothelial lamellar keratoplasty are described and...The concept of selectively transplanting the corneal endothelium has been contemplated since the middle of the twentieth century. Procedures leading up to and including endothelial lamellar keratoplasty are described and discussed in this article.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683253
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The limbal pocket approach to endothelial replacement shows extraordinary promise in fulfilling the ideal goals of surgical treatment for endothelial dysfunction. From its inception, DLEK surgery has demonstrated that, b...The limbal pocket approach to endothelial replacement shows extraordinary promise in fulfilling the ideal goals of surgical treatment for endothelial dysfunction. From its inception, DLEK surgery has demonstrated that, by preserving the limbus and eliminating surface corneal incisions and sutures, the corneal topography can be stabilized with little change from preoperative measurements of astigmatism and corneal power. The surgical dissection planes of DLEK surgery are inherently stronger than that of PK or any other form of endothelial replacement, allowing early stability of the refraction and making the eye safer from blunt trauma over the long term. Further work with DLEK must be performed in perfecting the optical properties of the stromal interface before this technique can be used widely; however, as technology and techniques improve, DLEK surgery holds the promise of being the ideal method for endothelial replacement in the 21st century.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683252
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Therapeutic soft contact lenses were first approved in the 1970s, but the variety of available materials and parameters continues to evolve. Currently, the armamentarium of therapeutic contact lenses allows the clinician...Therapeutic soft contact lenses were first approved in the 1970s, but the variety of available materials and parameters continues to evolve. Currently, the armamentarium of therapeutic contact lenses allows the clinician to select lenses that not only protect the corneal surface but also assist in modulation of the healing process. This article summarizes the available contact lenses, the conditions most amenable to treatment, and the decision-making process that allows optimal selection of a therapeutic contact lens for a specific patient. Many of the hydrophilic soft contact lenses used for cosmetic correction are not approved for therapeutic use but have been used in an off-label manner as therapeutic lenses. Communicating with the patient is important when recommending the use of a therapeutic contact lens, explaining the goals of therapy, warning about the risks contingent upon contact lens use, and determining whether the lens is being used in an off-label fashion. The advances in contact lens technology have opened new options for use of therapeutic contact lenses. With a new generation of high-Dk lenses whose makers promise fewer limiting problems of vascularization and infection, the utility of the older, traditional therapeutic lenses can be enhanced and the more selective application of individual lenses can be permitted. By considering the healing objectives of the particular treatment plan for a specific patient, greater control of the endpoint and timeframe of therapy is now possible.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683251
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Fluid-ventilated, gas-permeable scleral lenses are a valuable front-line tool in the management of severe ocular surface disease. In addition to enhancing vision, they have the potential to reduce greatly the disabling o...Fluid-ventilated, gas-permeable scleral lenses are a valuable front-line tool in the management of severe ocular surface disease. In addition to enhancing vision, they have the potential to reduce greatly the disabling ocular pain and photophobia associated with SJS, TEN, and ocular cicatricial pemphigoid. They are also useful in healing some PEDs that are refractory to all other treatment strategies and in reducing PED recurrence in stem cell-deficient and neurotrophic corneas. The therapeutic benefits of these lenses are provided by the oxygenated aqueous environment they create over the corneal epithelium. The oxygenated precorneal fluid compartment that is maintained at neutral pressure protects the epithelial surface from the desiccating effects of exposure to air and the friction generated by blinking and avoids the shearing forces generated during the blink-induced movement of soft lenses.
Ophthalmol Clin North Am
· 2003 Mar · PMID 12683250
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Practitioners and patients have been hesitant to use extended-wear contact lenses because of their history of complications; however, there is strong scientific evidence that the hypoxia problems associated with these le...Practitioners and patients have been hesitant to use extended-wear contact lenses because of their history of complications; however, there is strong scientific evidence that the hypoxia problems associated with these lenses have been solved. Similarly, clinical evidence shows that the new generation of contact lenses is safe and can be worn without complications for up to 30 days. Patients are now able to wear contact lenses that meet their desire of continuous vision. Both practitioner and patient, however, must be instructed about the signs and symptoms of contact lens complications. Practitioners need to learn about the diagnosis and management of these problems, and patients must be educated about proper eye care, contact lens care, and appropriate follow-up.