Anesthesia and preoperative and postoperative medications

Retrobulbar blocks, although widely used, still have potentially serious complications. Topical anesthesia presents less risk of injury to the globe and less pain but requires careful usage and an experienced surgeon. New techniques, however, allow for an increase in the percentage of patients able to have topical anesthesia. Preoperatively, 2.5% phenylephrine is found to be just as effective as 10% phenylephrine, and, when compared with wound closure and surgeon's experience, the effect of prophylactic medications was found to be negated. Postoperatively, diclofenac is found to be as effective an anti-inflammatory agent as prednisolone. Also, the addition of 10% phenylephrine to 4% pilocarpine drops enhances the effectiveness of pharmacologic treatment of postoperative iridocorneal adhesions. In addition, ophthalmologists should be aware of emerging antibiotic resistance.     

Temporal Frequency and the Magnocellular and Parvocellular Systems

Can the magnocellular system be stimulated exclusively, or predominantly, by using a particular temporal frequency? There are two problems. (1) Many researchers have confused contrast reversal rates with luminance modulation frequencies, even though it is the latter (which is half the reversal rate) that may be compared to neuronal responses. (2) Many of the frequencies used are too low to selectively activate magnocellular neurons. While a pure magnocellular response may be obtained by employing particular combinations of temporal frequency, spatial frequency and contrast, however, this possibility is limited to stimuli close to detection threshold, and such stimuli give only weak responses.     

Clinical and theoretical considerations of a patient with narrow angles and shallow anterior chambers.

Clinicians must always be on the alert to identify those individuals who appear to be anatomically disposed to narrow angle glaucoma. However, it is not axiomatic that these individuals can be provoked into an attack even if a history of subacute attacks exists. In this paper, and in one other to follow, the case histories of several interesting patients that were seen by the author for routine eye examinations will be discussed. The intent of the papers is to demonstrate that the diagnosis of glaucoma, existent or potential, can be quite time consuming and is dependent on far more than just tonometry.     

Rod and cone ERGs and their oscillatory potentials

Normal human ERGs were recorded from a dark-adapted subject using white and colored test flashes. Oscillatory potentials (OPs) were studied after high-pass digital filtering. When blue and red responses were compared at equivalent photopic intensities, OPs were visible at much lower intensities for the blue flashes. As the intensity was reduced from maximum, the first (negative) wave for red flashes maintained a latency of 20-25 msec before being lost in noise, whereas the first wave for blue flashes increased its latency progressively from 25 to 60 msec. These differences between photopically matched red and blue responses are interpreted to be due to rod-generated responses. When blue, orange, and white responses were compared at equivalent scotopic intensities, the latency of the largest negative wave was found to be similar for all three colors. The authors interpret this wave to be the beginning of the rod-generated OPs, so that the preceding waves (particularly evident for orange flashes) are cone-generated OPs, and they propose that the existence of separate rod and cone OPs should be borne in mind when investigating clinical changes in OPs.     

Orbital infections and inflammations.

Orbital infections and inflammations present to the clinician with similar findings: periorbital edema, erythema, proptosis, and pain. History and clinical examination determine the work-up required to better define the disease process. Orbital infections continue to be associated primarily with diseases of the paranasal sinuses. Haemophilus influenza type B is no longer a significant pathogen, because of an effective vaccine. Fungal infections extending to the orbit are becoming more frequent due to the prevalence of immunocompromised patients. Orbital inflammations continue to be poorly understood, and an adequate classification scheme does not exist. Corticosteroids continue to be the preferred initial treatment, with the roles of radiation and nonsteroidal antiinflammatory medications to be determined. Specific causes of orbital inflammation such as Wegener granulomatosis must be considered to prevent potentially life-threatening complications.     

Aniseikonia and anisometropia: implications for suppression and amblyopia

Aniseikonia is a difference in the perceived size or shape of images between eyes, and can arise from a variety of physiological, neurological, retinal, and optical causes. Aniseikonia is associated with anisometropia, as both anisometropia itself and the optical correction for anisometropia can cause aniseikonia. Image size differences above one to three per cent can be clinically symptomatic. Common symptoms include asthenopia, headache and diplopia in vertical gaze. Size differences of three and more impair binocular visual functions such as binocular summation and stereopsis. Above five per cent of aniseikonia, binocular inhibition or suppression tend to occur to prevent diplopia and confusion. Aniseikonia can be measured using a range of techniques and can be corrected or reduced by prescribing contact lenses or specially designed spectacle lenses. Subjective testing of aniseikonia is the only way to accurately measure the overall perceived amount of aniseikonia. However, currently it is not routinely assessed in most clinical settings. At least two‐thirds of patients with amblyopia have anisometropia, thus we may expect aniseikonia to be common in patients with anisometropic amblyopia. However, aniseikonia may not be experienced by the patient under normal binocular viewing conditions if the image from the amblyopic eye is of poor quality or is too strongly suppressed for image size differences to be recognised. This lack of binocular simultaneous perception in amblyopia may also prevent the measurement of aniseikonia, as most common techniques require direct comparisons of images seen by each eye. Current guidelines for the treatment of amblyopia advocate full correction of anisometropia to equalise image clarity, but do not address aniseikonia. Significant image size differences between eyes may lead to suppression and abnormal binocular adaptations. It is possible that correcting anisometropia and aniseikonia simultaneously, particularly at the initial diagnosis of anisometropia, would reduce the need to develop suppression and improve treatment outcomes for anisometropic amblyopia.     

Serum and tear immunoglobulins in bacterial, fungal and viral corneal ulcers

Serum and tear IgA, IgG and IgM levels were studied in patients with bacterial, fungal and viral corneal ulcers. In patients with viral corneal ulcers serum IgA and IgG levels were found to be significantly raised, while IgM concentration remained unaltered. In bacterial and mycotic ulcerations, serum IgA, IgG and IgM levels remained unaltered. All three immunoglobulins were found to be raised in tears of patients with viral corneal ulcers, while only IgA levels were found to be increased in bacterial and mycotic ulcerations.     

Emotional stress and rejection,cause and effect

Over the years we have noticed on more than one occasion a connection between rejection of a corneal graft and emotional stress. We considered this at first to be a coincidence. However, we have now seen 11 patients in whom an acute rejection occurred just after emotional stress. There appears to be a clear relationship between psychological stress and rejection.     

Presbyopia and cataract: A question of heat and time

Not only are human lenses different in many ways from those of non-primates, they also undergo dramatic changes with age. These age-dependent alterations lead to perturbations in the properties of older lenses, and ultimately to disturbances in visual function, which typically become apparent at middle age. Recent data suggest that many, if not all, of these age-dependent features can be traced to the lack of macromolecular turnover in the lens and to the inexorable modifications to proteins and membrane components over a period of decades. Exposure of lenses to heat can reproduce many of these alterations, suggesting that long-term incubation at body temperature may be an important factor in aging the human lens. Two conclusions flow from this. Firstly, the human lens may be an ideal tissue for studying macromolecular aging in man. Secondly, it will be extremely challenging to examine the origin of human age-related conditions, such as presbyopia and nuclear cataract, using traditional laboratory animals.Characterising the unfolding and decomposition of long-lived macromolecules appears to provide the key to understanding the two most common human lens disorders: presbyopia and age-related nuclear cataract.     

Glare disability and driving safety

PURPOSE: Increasing investigation of the visual elements of safe driving environments may be of great benefit to society. Visual disability appears to be only one of many visual factors related to traffic accidents. The purpose of this article was to examine the type of visual impairment mediated by the increased glare sensitivity in adult drivers using the original halometer glare test. METHODS: In this article, the visual sensory, cognitive and motor functions relevant to driving, their measurement, the epidemiology and prevention of age-associated functional impairments and the relationship of functional impairments to both self-reported driving and the imposition of legal restrictions are reviewed. RESULTS: The problem of night and tunnel driving is the most urgent in relation to the effects of glare from vehicle headlights on motion perception of drivers. The reduced mesopic vision and increased sensitivity to glare are accompanied by an increased risk of nighttime accidents. Elderly drivers and patients with beginning cataract cannot sufficiently fulfill the criteria for night driving ability because of contrast and glare sensitivity. It is indispensable for the parameters mentioned to be carefully measured and for drivers to be informed that night driving ability may be impaired, even if visual acuity is sufficient. CONCLUSIONS: It would be advisable for traffic safety if simple tests for contrast and glare sensitivity were implemented for vehicles and/or were regularly added to the requirements for a driver's licence, at least for older drivers. The age, functional status and test result limits should be defined to avoid a risk factor in traffic.     

Age-related macular degeneration and apoptosis

Several studies suggest that apoptosis might play a major role in age-related macular degeneration. Apoptosis in retinal pigment epithelium cells undergoing severe oxidative stress has been reported and could therefore be involved in the pathogenesis of AMD. The processes of drusen formation seem to be similar to the processes described in apoptosis. Moreover, apoptosis appears to be involved in the early outgrowth of choroidal neovascular membranes as well as in the development of fibrotic scars at a later stage. Targeting apoptotic pathways should therefore be considered as a possible treatment approach for AMD.     

Nutrition and optic nerve disease

The syndrome characterized by papillomacular bundle damage, central or cecocentral scotoma, and reduction of color vision can be produced by toxic, nutritional, or hereditary causes. Patients who present with such a picture should be evaluated for toxic sources such as tobacco or alcohol use. Nutritional deficiencies must be considered and a good family history should be obtained to explore hereditary factors. DNA mutation analysis is available to detect genetic abnormalities. A trial of nutritional replacement may be advisable even in the face of normal laboratory values. Previous reports have shown dramatic visual improvement with intramuscular hydroxocobalamin and other oral vitamin B complexes, even when specific deficiencies are not found.     

Autoimmunity and glaucoma

Elevated intraocular pressure does not explain glaucoma in all patients, but there is information that autoimmune mechanisms may be involved in this disorder. This review attempts to reveal the findings about specific changes in autoantibody profiles in glaucoma patients and their possible role in glaucoma. Considering that these changes in natural autoimmunity can be found consistently among different study populations, it might be a promising new tool for glaucoma detection.     

Congenital glaucoma and trabeculodysgenesis. Clinical and genetic aspects

Congenital glaucoma is generally related to an iridocorneal angle malformation, with an obstacle to aqueous humor outflow. This spectrum of diseases can involve the angle, the iris and the cornea. The diagnosis relies on characteristic signs and is confirmed by an examination under general anaesthesia and paraclinical examinations (especially echography). An early diagnosis is essential for beginning surgical treatment. Several filtering surgery techniques with equivalent intraocular pressure results are available, but visual function must be protected in all cases. In many cases, genetic counseling relies on a careful clinical analysis and sometimes on a molecular analysis. A number of ocular and/or general abnormalities can be accompanied by glaucoma in infants and children. They must be screened in case of associated signs, but the existence of these abnormalities leads to suspicion of associated glaucoma.     

Evisceration and Enucleation

Evisceration and enucleation are delicate procedures that result in psychological trauma and physical disability. The preparation is as important as the surgery itself to assure that the patient will return to a productive life. The procedure must be performed in a way to provide the best conditions for a perfect prosthesis, which should look similar to the fellow eye, follow its movements, be comfortable and aesthetically pleasing. Indications and contra-indications, surgical techniques, pre- and post-operative care and complications are discussed in this paper.     

A micro-advancer device for vitreal injection and retinal recording and stimulation

A micro-advancer device that positions a narrow-gauge needle within the vitreous humor of the rat eye is described. The device is compact, simple and inexpensive to manufacture. It consists of an outer guard needle and an inner injection needle that is advanced through the guard needle. With the rat held in a stereotaxic holder and the globe fixed to a stabilizing ring, the outer 25-gauge guard needle is advanced through the sclera using a standard micromanipulator. The inner 31-gauge injection needle is then advanced through the guard needle with a manually controlled leadscrew and carriage mechanism. The inner injection needle is attached to a Hamilton syringe and can be positioned to within microns of the retinal surface under visual observation through a microscope. The injection needle is fixed to the device by a quick-release clamp on the carriage and can be rapidly exchanged while the guard needle remains in place in the vitreous. This permits different solutions to be injected sequentially into the vitreous humor. Recording electrodes, stimulating electrodes, and optical fibers can also be advanced through the guard needle and positioned accurately near the retinal surface or within the retina.     

Computer hardware and software to assist the visually impaired and blind

Modern developments in computer hardware and software for the business world have been adapted to allow the partially sighted and blind to participate successfully in computer usage in education, employment and recreation. Adaptations such as the enlargement of the whole screen display, production of enlarged print and voice output of screen contents can assist the partially sighted. Conversion of computer screen information into speech or braille can be used in conjunction with sound boards and touch pads to allow the totally blind access to the exact spatial layout of screen contents
Optical character recognition devices whereby the printed page can be accessed by computer, and recent voice recognition techniques which allow a computer to interpret voiced commands, can also be used to assist the totally blind. Developments in these areas are discussed together with specific examples of equipment now available which make use of the various methods described     

Pregnancy and glaucoma

Glaucoma, primarily a disease of the older population, may affect women of childbearing age. Pregnancy affects the intraocular pressure (IOP) of women with pre-existing glaucoma. Both elevations and reductions of IOP have been reported during pregnancy. Additionally, visual field test results may fluctuate during pregnancy. In managing the pregnant glaucoma patient with medical therapy, one must consider not only the systemic side effects on the mother, but also any potentially harmful effects on the developing fetus. All anti-glaucoma medications are categorized as class C by the Food and Drug Administration, except brimonidine and nonspecific adrenergic agonists, which belong to class B. In general, the lowest effective dosage of medication should be used. Systemic absorption can be reduced by punctal occlusion, eyelid closure, and blotting the excess drops away during administration. In those patients who need surgery, most local anesthetics may be used safely because they have not been shown to be teratogenic in humans. Antifibrotic agents commonly used adjunctively in trabeculectomy, however, should be avoided. Glaucoma laser procedures, such as laser peripheral iridotomy and laser trabeculoplasty, have been employed without identifiable teratogenic effects or increased risk of side effects for pregnant women.     

Central serous chorioretinopathy, corticosteroids, and uveitis

Any patient with a diagnosis of central serous chorioretinopathy (CSCR) should be questioned to determine any recent corticosteroid use, as the poor visual outcome may be due to unrecognized corticosteroid use. Atypical forms of CSCR may be misdiagnosed as an inflammatory serous retinal detachment, mainly Vogt-Koyanagi-Harada disease. CSCR that develops in association with preexisting uveitis could be a challenging diagnosis as it might be misinterpreted as a worsening of the primary inflammatory condition. Failure to differentiate CSCR from retinal or choroidal inflammatory diseases may result in inappropriate use of corticosteroids, leading to exacerbation of the condition and permanent visual loss. Discontinuation of corticosteroids should be the first step in the treatment of CSCR associated with corticosteroid therapy, and the use of immunosuppressive or immunomodulatory drugs may be required to control systemic or ocular inflammatory disease. The prognosis is usually favorable, but persistent visual loss may occur.     

Contact lenses and collagen shields

Contact lenses may change the topography of the eye of asymptomatic patients. Complications continue to occur requiring extreme attention to be paid to fitting techniques, care instructions, and follow-up. All physicians must be alert to complications. Early diagnosis and treatment are essential. The pediatric aphakic patient and the presbyopic contact lens wearer present a challenge. The contact lens fitter must understand the way these lenses function to fit patients more successfully. Collagen shields may be of some benefit in cataract surgery and symblepharon, but may exacerbate the effects of alkali burns on the eye.