Biomedical subjects

N P Strong

Publications and source records attributed to N P Strong.

22 records · Page 2Linked to original sources

PubMed1991

Daycase cataract surgery.

The increasing demand for cataract surgery, combined with limited resources, has created renewed interest in daycase admission. We have audited the results of all daycase and inpatient cataract surgery in a large unit over a six-month period to determine the factors influencing daycase admission and surgical outcome; 34% of cataract patients were admitted as daycases in the study period. Neither distance travelled by the patient nor age appear to influence daycase admission. However, the differing policies of the individual consultant surgeons resulted in a wide variation in the number of operations performed on a daycase basis by each firm. The rate of preoperative complications was unaffected by daycase admission, by the grade of surgeon operating, or by the type of anaesthetic employed. Only 2.1% of daycase admissions resulted in unplanned inpatient admission on the day of surgery, with another 2.1% being readmitted within six months of surgery. Late cancellation of surgery was much lower for daycases (0.4%) than for inpatients (5.1%).

Aged↗

PubMed1984

Horizontal optokinetic nystagmus in the cat: recovery from cortical lesions.

We have examined recovery from the acute effects of unilateral and bilateral visual cortex lesions on horizontal optokinetic nystagmus (OKN) in the cat. A single bilateral cortical lesion virtually abolishes monocular OKN in response to temporalward stimulation, and severely reduces OKN in response to nasalward stimulation at higher drum velocities. A unilateral cortical lesion causes deficits in OKN toward the side of the lesion, but these changes are less substantial than those observed after a bilateral lesion. The nature of the acute changes in OKN caused by cortical lesions supports the notion that the visual cortex has two important roles in the OKN system of the cat: first, it mediates OKN in response to temporalward motion of the visual environment during monocular viewing; second, it expands the response range of the OKN system to include higher stimulus velocities. Finally, the results from unilaterally lesioned cats suggest that a single hemisphere can mediate OKN in both directions, with an emphasis on the direction ipsilateral to that hemisphere. The patterns of recovery of OKN in lesioned cats follow two major trends: a small, gradual increase in the overall gain of OKN from its severely depressed level immediately after a large bilateral lesion, and a 'balancing' process that reduces the marked asymmetry between rightward and leftward OKN caused by a unilateral lesion. This balancing of the reflex is accomplished by an improvement in performance in one direction while performance in the opposite direction actually declines. Recovery is faster and more pronounced in lesioned cats with one cortical hemisphere intact, suggesting that the surviving visual cortex compensates for the effects of the lesion by modifying activity in subcortical pathways. These experiments indicate that the visual system of the cat has the capacity to recover at least partially from the deficits in OKN behavior caused by cortical lesions, and that this recovery is the outcome of an interaction between cortical and subcortical pathways mediating this important visuomotor reflex.

Adaptation, Physiological↗

PubMed1984

Horizontal optokinetic nystagmus in the cat: effects of long-term monocular deprivation.

The effects of prolonged monocular deprivation (MD) on horizontal optokinetic nystagmus (OKN) have been examined in cats subjected to unilateral or bilateral visual cortex lesions. Presurgically , OKN elicited through the deprived eye was substantially weaker than that through the non-deprived eye. This effect was most prominent for OKN in response to temporalward stimulation, which essentially was abolished in the deprived eye. In addition, OKN elicited by temporalward stimulation of the non-deprived eye tended to be weaker in comparison to nasalward stimulation of that eye. A bilateral cortical lesion severely disrupted OKN behavior through the non-deprived eye but left OKN through the deprived eye relatively unaffected, with the result that the marked interocular differences in OKN that were present presurgically disappeared. During the recovery period following this lesion, there was a small gradual improvement in OKN through both eyes, so that OKN performance through the deprived eye ultimately exceeded that observed presurgically . Unilateral cortical lesions had little effect on OKN through the deprived eye, but they produced substantial changes in OKN through the non-deprived eye. Both the immediate effects of cortical lesions, and the patterns of recovery observed following these lesions, in many ways resemble those observed when normally reared cats are subjected to similar lesions. These behavioral experiments indicate that while subcortical OKN pathways are spared from the effects of long-term monocular deprivation, cortical pathways mediating OKN through the deprived eye are severely disrupted.

Animals↗

PubMedDate not supplied

Exchange technique for opacified hydrophilic acrylic intraocular lenses.

PURPOSE: To report an exchange technique for opacified hydrophilic acrylic intraocular lenses (IOLs). METHODS: . Twenty patients with two different types of opacified hydrophilic acrylic IOLs underwent IOL exchange by a single surgeon. Circumferential enlargement of the pre-existing capsulorrhexis was a critical step of the procedure, and resulted in expression of the IOL with minimal traction to the capsule. Implantation of an in-the-sulcus IOL followed. Surgical technique, complications, and visual outcome are discussed. RESULTS: Time from the initial cataract operation varied from 15 to 61 months (mean 30.5), and in all cases marked fibrosis was encountered. Eighteen patients had uncomplicated IOL exchange. Posterior capsule rupture occurred in two cases. Vision improved in 16 cases, remained unchanged in 3 cases, and deteriorated in 1 case. CONCLUSIONS: IOL exchange of opacified hydrophilic acrylic IOLs is a particularly challenging procedure due to extensive fibrosis. Circumferential enlargement of the pre-existing capsulorrhexis significantly facilitates the mobilization of the IOL from its fibrous pocket, with the use of minimal forces. Thus, the risk of zonular dehiscence or posterior capsule rupture is minimized.

Acrylic Resins↗