Videokeratoscopic indices in relation to epidemiological exposure to keratoconus

Background  

To establish the relationship between videokeratoscopic indices and the degree of epidemiological exposure to keratoconus in three groups of clinically normal subjects.     

Comparative monocular contributions to brightness in relation to abnormal stereothreshold

This study was designed to compare brightness contributions of the two monocular inputs to the binocular visual system at three different levels of luminance adaptation in two groups of 15 subjects each. The only known difference between these groups was stereothreshold, 50 to 70 sec arc in one group vs. 40 sec arc or less in the other group. The group with elevated threshold was found to have a significantly larger average difference (13.5%, p less than 0.002) in monocular brightness contributions, between the right and left eyes, when compared to the group with lower stereothresholds (4% mismatch). The results also indicate that neither group showed a significant variation in mismatch as adapting luminance was altered by a factor of four times (0.6 log units). Finally, no clear relation was found between eye dominance and the eye requiring higher illuminance to attain the dichoptic brightness match.     

Neuroprotection in Relation to Retinal Ischemia and Relevance to Glaucoma

Management of glaucoma is directed at the control of intraocular pressure (IOP), yet it is recognized now that increased IOP is just an important risk factor in glaucoma. Therapy that prevents the death of ganglion cells is the main goal of treatment, but an understanding of the causes of ganglion cell death and precisely how it occurs remains speculative. Present information supports the working hypothesis that ganglion cell death may result from a particular form of ischemia. Support for this view comes from the fact that not all types of retinal ischemia lead to the pathologic findings seen in glaucomatous retinas or to cupping in the optic disk area. Moreover, in animal experiments in which ischemia is caused by elevated IOP, a retinal abnormality similar to that seen in true glaucoma is produced, whereas after occlusion of the carotid arteries a different pattern of damage is found. In ischemia, glutamate is released, and this initiates the death of neurons that contain ionotropic glutamate (NMDA) receptors. Elevated glutamate levels exist in the vitreous humor of patients with glaucoma, and NMDA receptors exist on ganglion cells and a subset of amacrine cells. Experimental studies have shown that a variety of agents can be used to prevent the death of retinal neurons (particularly ganglion cells) induced by ischemia. These agents are generally those that block NMDA receptors to prevent the action of the released glutamate or substances that interfere with the subsequent cycle of events that lead to cell death. The major causes of cell death after activation of NMDA receptors are the influx of calcium into cells and the generation of free radicals. Substances that prevent this cascade of events are, therefore, often found to act as neuroprotective agents. For a substance to have a role as a neuroprotective agent in glaucoma, it would ideally be delivered topically to the eye and used repeatedly. It is, therefore, of interest that betaxolol, a β-blocker presently used to reduce IOP in humans, also has calcium channel-blocking functions. Moreover, experimental studies show that betaxolol is an efficient neuroprotective agent against retinal ischemia in animals, when injected directly into the eye or intraperitoneally.     

Factors in adjustment to blindness

We wished to explore the relationship between certain blinding eye diseases, residual vision and psychosocial adjustment, including acceptance of blindness. One hundred and fourteen patients were grouped according to level of vision, age, type of disease, general physical health and duration of blindness. Psychological symptoms were measured by the Minnesota Multiphasic Personality Inventory (M.M.P.I.) and social function by an adaptation to blindness of the Gunzberg Progress Chart of Social Function. Social adjustment was best and psychological morbidity least in those with non-diabetic retinal disorders, those who had the best vision and those who accepted their blindness. Non-acceptance of blindness was associated with the most psychological distress and the lowest scores in social adjustment. People with glaucoma and diabetic retinal disorders seemed more poorly adjusted. An attempt should be made to identify those most prone to maladjustment so as to assist them in rehabilitation.     

Introduction to apoptosis in ophthalmology

Apoptosis represents a mode of cellular death genetically programmed to maintain homeostasis of tissues. In specific pathologic circumstances, the death program may be activated by various environmental factors such as exposure to toxic substances or bacteria or deprivation of nutrients. From this point of view, apoptosis is considered the final event in several pathologies. In ophthalmology, experimental evidence has confirmed that apoptosis is a type of cellular death involved in various pathologic processes including glaucoma, retinitis pigmentosa, ischemic retinopathy, corneal reparative processes, cataract, and retinoblastoma. The aim of this article is to review the most recent results published in this field and to describe some of the molecular mechanisms responsible for the activation of the apoptotic program in some important ocular disorders. The understanding of such mechanisms could outline new therapeutic strategies for the prevention of cellular death in ophthalmology.     

Changes in the G-DRG System from 2003 to 2005 in Ophthalmology--Ophthalmologic G-DRG 2003 to 2005

BACKGROUND: The objective of the study was to illustrate the effect of the extensive changes of the German DRG System on reimbursement of clinical ophthalmology during the years 2003, 2004 and 2005. METHODS: All ophthalmologic patients treated as in-patients at the Department of Ophthalmology at the University Munich during the year 2003 served as a reference data basis. By means of appropriate software those cases were then re-grouped according to the G-DRG classification of the years 2003, 2004 and 2005. This resulted in different reimbursements caused only by system changes for an exemplary hospital of maximum medical care. In addition, the same calculations were performed for four virtual, typical clinics based on the calculation data of the "Institut für Entgeltsysteme (InEK)". For those four clinics it was assumed that 80 % of the cases came from one of the subspecialties retina, glaucoma, cataract or strabismus surgery. RESULTS: Changes in the G-DRG system caused the sample hospital of maximum care to loose 8.5 % case mix index (CMI) during the period of 2003 to 2005. For three of the four virtual, typical ophthalmological clinics the theoretic reimbursement conditions also deteriorated: retina surgery -- 10.6 %, glaucoma surgery - 15.8 % and cataract surgery -- 17.9 % CMI. Only strabismus surgery showed an increase of + 5.6 % in CMI during the period examined. CONCLUSION: Over the years 2003 to 2005 the CMI clearly deteriorated for many ophthalmological subspecialties given otherwise identical conditions. To calculate the changes specifically for an individual hospital, the individual base rates have to be considered.     

Reply to the letter to the editor: Multifocal electroretinography in amblyopia

Graefe's Archive for Clinical and Experimental Ophthalmology -     

Electroretinographic responses to the addition of nitrous oxide to halothane in rats

The electroretinograms of 20 anesthetised but spontaneously breathing rats (Wistar) were recorded over a period of 60 minutes. Two anesthetical procedures were applied to each of these rats respectively: (I) halothane/nitrous oxide/oxygen (2% halothane in 0.81 N₂O: 0.41 O₂/min) and (II) halothane/nitrogen/oxygen (2% halothane in 0.81 N₂: 0.41 O₂/min).From the 10th up to the 60th min of anesthesia the ERG amplitudes decreased gradually (I: a-wave 17% and b-wave 14%; II: a-wave 15% and b-wave 12%). Body temperature was experimentally maintained at nearly 37.0 °C. Under considerable diminution in both procedures the frequency of respiration was significantly higher under procedure I in the first 20 minutes only.Under procedure I the b-wave amplitudes were significantly higher in contrast to procedure II. This occurred at all applied stimulus intensities (6; 24; 100; 400 and 1600 Lux at the cornea). The a-wave amplitudes and the peak times of the a- and b-waves did not show any significant differences between the two experimental conditions.These ERG responses to nitrous oxide in addition to halothane are discussed on the basis of the respiratory, circulatory and cerebral effects of these anesthetics.     

Asymmetries related to cerebral dominance in returning the eyes to specified target positions in the dark

Left-handed subjects with left eye dominance and right-handed subjects with right eye dominance show differences of performance, related to their hand and eye preference, in returning the eyes to a target position in the dark, after making saccades away to the left or right. These differences are shown particularly in magnitude of error, but also in amount of undershoot and in the number of saccades made. It is suggested that the observed asymmetries of performance implicate a cortical mechanism concerned with the registration of information about saccadic eye movements.     

Ocular hypersensitivity to thimerosal in rabbits

Rabbits were immunized to thimerosal conjugates and challenged with specific antigen-sensitized contact lenses. The symptoms of acute ocular hypersensitivity observed included corneal edema, corneal infiltration and erosion, infiltration of the anterior chamber, iritis, conjunctival edema and hyperemia, and a significant increase in mucous production. Occasional evidence of corneal neovascularization and giant conjunctival papillae were seen. All these parameters were assessed on a five-point scale (0 to +4) and tabulated as an ocular index. The index of ocular hypersensitivity correlated with the titers of the serum antibodies to thimerosal. The major class of serum antibodies consisted of immunoglobulin (Ig) G, with IgA compromising approximately 5% of serum antibodies. During the ocular challenge, the total and IgG tear antibody titers increased as a result of increased vascular permeability. The tear IgA titers increased to a lesser extent than IgG. The influx of serum proteins directly into the tear film was confirmed by a protein-dye tracer technique. Histologic analysis showed that the ocular inflammatory response was accompanied by both polymorphonuclear and mononuclear cell infiltrates into the cornea and conjunctiva. In conclusion, thimerosal-immunized rabbits show an exquisite sensitivity to the minute quantities of thimerosal conjugates adsorbed to contact lenses. Both serum and tear antibodies correlate with the severity of the ocular inflammatory response. This model would appear to simulate an antibody-mediated immune complex or Arthus type of ocular hypersensitivity commonly seen to foreign antigens including preservatives.     

Accommodation to perceived depth in stereotests

The question of whether the eye may accommodate to the stimulus provided by apparent depth in stereograms is considered theoretically in relation to the magnitudes of the disparities and viewing distances found in typical clinical stereotests. It is concluded that, for the relevant range of disparities (≤2000 arc sec), any shift in accommodation is likely to be small (≤0.15 D). An experimental study with two different clinical stereotests (Lang, TNO) confirms this prediction.