Accuracy of intraocular lens power formulas in patients with average keratometry greater than 46 diopters.

OBJECTIVE: To compare the accuracy of Kane, Barrett Universal II, Haigis, and SRK-T formulas in eyes with average keratometry greater than 46 diopters (D). METHODS: A retrospective analysis was conducted on 101 eyes of 101 patients with average keratometry greater than 46 D. The absolute prediction error (EA) was obtained for each patient one month after surgery. The mean absolute prediction error (MEA), median absolute prediction error (MedEA) and the percentage of patients with absolute refractive error less than 0.25 D, 0.50 D, and 1.00 D were calculated for each formula analyzed. RESULTS: The Kane formula achieved the lowest MEA (0.53 ±â€¯0.43) and the lowest MedEA (0.41), followed by Barrett Universal II (MEA: 0.56 ±â€¯0.42, MedEA: 0.49), SRK-T (MEA: 0.59 ±â€¯0.44, MedEA: 0.54), and Haigis (MEA: 0.77 ±â€¯0.47, MedEA: 0.69), showing a significant difference in the results. It was also observed that the Kane formula was the most accurate, with the highest percentage of patients, with EA less than 0.25 D, 0.50 D, and 1.00 D (30.7%, 54.4%, and 86.1%, respectively), while the Haigis formula was the least accurate (12.9%, 33.7%, and 69.3%, respectively). CONCLUSION: In eyes with corneas having average keratometry greater than 46 D, the Kane formula proves to be a useful tool in intraocular lens (IOL) power calculation and demonstrates higher precision compared to the Barrett Universal II, SRK-T, and Haigis formulas.

On the phasic reflex bronchodilation in the cat.

In records of tracheal pressure or flow taken from anesthetized cats appear large pressure-negative, or air inflow excursions, in response to single pulses applied to the central end of the vagus nerve. These responses have been attributed to phasic bronchodilation and not only due to the brief contractions of inspiratory muscles that occur as part of the total responses. Phasic bronchodilation responses appear mainly during inspiration but they may also occur in the expiratory phase through facilitation, during post-hyperventilatory apnea or that induced by constant current (d.c.) vagal stimulation. They are significantly reduced after lung sympathectomy. These bronchomotor responses showed long term depression (LTD) after spontaneous or reflexly evoked hiccups, and long term potentiation (LTP) after repetitive, or d.c. vagal stimulation. They are also potentiated on the experimental conditions that include exaggerated sympathetic activity. These and some other characteristics described indicate that bronchomotor responses are legitimate and can be used to follow the changes in excitability of the central generator of breathing.

On the phasic reflex bronchodilation in the cat.

In records of tracheal pressure or flow taken from anesthetized cats appear large pressure-negative, or air inflow excursions, in response to single pulses applied to the central end of the vagus nerve. These responses have been attributed to phasic bronchodilation and not only due to the brief contractions of inspiratory muscles that occur as part of the total responses. Phasic bronchodilation responses appear mainly during inspiration but they may also occur in the expiratory phase through facilitation, during post-hyperventilatory apnea or that induced by constant current (d.c.) vagal stimulation. They are significantly reduced after lung sympathectomy. These bronchomotor responses showed long term depression (LTD) after spontaneous or reflexly evoked hiccups, and long term potentiation (LTP) after repetitive, or d.c. vagal stimulation. They are also potentiated on the experimental conditions that include exaggerated sympathetic activity. These and some other characteristics described indicate that bronchomotor responses are legitimate and can be used to follow the changes in excitability of the central generator of breathing.

On the mechanism of the cortical depression induced by afferent stimulation.

The cortical depression induced by the stimulation of some afferent fibers affects strychnine spikes elicited in two different ways: by direct electrical stimulation, and through the evoked potentials induced at the somatosensory area by single shocks to the radial nerve. The effects on these two types of responses were found to be very similar, which was taken to indicate that the site of action of the mechanism involved is the same, that is, the non-synaptic membranes of the dendrites of pyramidal neurons. It is suggested that the depressant action is mediated through the serotonergic neurons, since the previous administration of 5,6-Dihydroxytryptamine (5,6-DHT) blocked the changes. The 5-Hydroxytryptamine (5-HT) liberated would act as a neurohumoral agent, since the synaptic mechanisms do not seem to be involved and the effects are manifested in a diffuse manner.

On the mechanism of the cortical depression induced by afferent stimulation

The cortical depression induced by the stimulation of some afferent fibers affects strychnine spikes elicited in two different ways: by direct electrical stimulation, and through the evoked potentials induced at the somatosensory area by single shocks to the radial nerve. The effects on these two types of responses were found to be very similar, which was taken to indicate that the site of action of the mechanism involved is the same, that is, the non-synaptic membranes of the dendrites of pyramidal neurons. It is suggested that the depressant action is mediated through the serotonergic neurons, since the previous administration of 5,6-Dihydroxytryptamine (5,6-DHT) blocked the changes. The 5-Hydroxytryptamine (5-HT) liberated would act as a neurohumoral agent, since the synaptic mechanisms do not seem to be involved and the effects are manifested in a diffuse manner.

On the mechanism of the cortical depression induced by afferent stimulation.

The cortical depression induced by the stimulation of some afferent fibers affects strychnine spikes elicited in two different ways: by direct electrical stimulation, and through the evoked potentials induced at the somatosensory area by single shocks to the radial nerve. The effects on these two types of responses were found to be very similar, which was taken to indicate that the site of action of the mechanism involved is the same, that is, the non-synaptic membranes of the dendrites of pyramidal neurons. It is suggested that the depressant action is mediated through the serotonergic neurons, since the previous administration of 5,6-Dihydroxytryptamine (5,6-DHT) blocked the changes. The 5-Hydroxytryptamine (5-HT) liberated would act as a neurohumoral agent, since the synaptic mechanisms do not seem to be involved and the effects are manifested in a diffuse manner.