Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error

The description of sphero-cylinder lenses is approached from the viewpoint of Fourier analysis of the power profile. It is shown that the familiar sine-squared law leads naturally to a Fourier series representation with exactly three Fourier coefficients, representing the natural parameters of a thin lens. The constant term corresponds to the mean spherical equivalent (MSE) power, whereas the amplitude and phase of the harmonic correspond to the power and axis of a Jackson cross-cylinder (JCC) lens, respectively. Expressing the Fourier series in rectangular form leads to the representation of an arbitrary sphero-cylinder lens as the sum of a spherical lens and two cross-cylinders, one at axis 0 degree and the other at axis 45 degrees. The power of these three component lenses may be interpreted as (x,y,z) coordinates of a vector representation of the power profile. Advantages of this power vector representation of a sphero-cylinder lens for numerical and graphical analysis of optometric data are described for problems involving lens combinations, comparison of different lenses, and the statistical distribution of refractive errors.

Power vector analysis of the optical outcome of refractive surgery

PURPOSE

To demonstrate the power vector method of representing and analyzing spherocylindrical refractive errors.

SETTING

School of Optometry, Indiana University, Bloomington, Indiana, USA.

METHODS

Manifest and keratometric refractive errors were expressed as power vectors suitable for plotting as points in a 3-dimensional dioptric space. The 3 Cartesian coordinates (x, y, z) of each power vector correspond to the powers of 3 lenses that, in combination, fulfill a refractive prescription: a spherical lens of power M, a Jackson crossed cylinder of power J0 with axes at 90 degrees and 180 degrees, and a Jackson crossed cylinder of power J45 with axes at 45 degrees and 135 degrees. The Pythagorean length of the power vector, B, is a measure of overall blurring strength of a spherocylindrical lens or refractive error. Changes in refractive error due to surgery were computed by the ordinary rules of vector subtraction.

RESULTS

Frequency distributions of blur strength (B) clearly demonstrate the effectiveness of refractive surgery in reducing the overall blurring effect of uncorrected refractive error.

CONCLUSIONS

Power vector analysis also revealed a reduction in the astigmatic component of these refractive errors. Paired comparisons revealed that the change in manifest astigmatism due to surgery was well correlated with the change in keratometric astigmatism. Power vectors aid the visualization of complex changes in refractive error by tracing a trajectory in a uniform dioptric space. The Cartesian components of a power vector are mutually independent, which simplifies mathematical and statistical analysis of refractive errors. Power vectors also provide a natural link to a more comprehensive optical description of ocular refractive imperfections in terms of wavefront aberration functions and their description by Zernike polynomials.

Vinorelbine (navelbine) as a salvage treatment for advanced breast cancer

BACKGROUND

Vinorelbine (Navelbine), a new vinca alkaloid, is an effective drug in breast cancer. Our study was undertaken to assess the efficacy and tolerance of Navelbine in refractory advanced and/or metastatic breast cancer (AMBC).

PATIENTS AND METHODS

One hundred heavily pretreated patients with AMBC entered the study and were scheduled to receive 30 mg/m2 of Navelbine weekly by a 20 min i.v. infusion with dose adjustments according to tolerance. All patients had previously received at least one chemotherapy regimen including an anthracycline for advanced disease.

RESULTS

Sixteen of the 100 assessable patients responded (1 complete response and 15 partial responses), for an overall response rate of 16% (IC 95: 8%-23%). The median duration of response was 5 months (3-18). Responses were seen in lymph nodes (13/27), breast (11/34), soft tissue and skin (13/36), lung (3/14) and liver (2/25), but not in bone metastases. The main toxicities (WHO grade > or = 3) were granulocytopenia and anemia in, respectively, 51% and 9% of all 100 eligible patients. Thrombocytopenia and other non-haematological toxicities consisting of peripheral neuropathy, constipation, nausea/vomiting, alopecia and phlebitis were rare and mild.

CONCLUSION

Vinorelbine is an active drug in AMBC, particularly in breast, lymph nodes and skin/soft tissue sites, with an excellent tolerance. Since the mean dose intensity was 19.7 mg/m2/week, a dose of 20 mg/m2/week is recommended for heavily pretreated patients (radiotherapy and chemotherapy).

Characterization of a mitochondrion-like organelle in Cryptosporidium parvum

Cryptosporidium parvum is a protozoan parasite that causes widespread diarrhoeal disease in humans and other animals and is responsible for large waterborne outbreaks of cryptosporidiosis. Unlike many organisms belonging to the phylum Apicomplexa, such as Plasmodium spp. and Toxoplasma gondii, there is no clinically proven drug treatment against this parasite. Aspects of the basic biology of C. parvum remain poorly understood, including a detailed knowledge of key metabolic pathways, its genome organization and organellar complement. Previous studies have proposed that C. parvum lacks a relic plastid organelle, or 'apicoplast', but that it may possess a mitochondrion. Here we characterize a mitochondrion-like organelle in C. parvum by (i) ultrastructural and morphological description (ii) localization of heterologous mitochondrial chaperonin antibody probes (iii) phylogenetic analysis of genes encoding mitochondrial transport proteins (iv) identification and analysis of mitochondrion-associated gene sequences. Our descriptive morphological analysis was performed by energy-filtering transmission electron microscopy (EFTEM) of C. hominis and C. parvum. The 'mitochondrion-like' organelle was characterized by labelling the structure with a heterologous mitochondrial chaperonin probe (hsp60) both in immunoelectron microscopy (IMEM) and immunofluorescence (IMF). Phylogenetic analysis of the mitochondrial import system and housekeeping components (hsp60 and hsp70-dnaK) suggested that the C. parvum mitochondrion-like organelle is likely to have descended from a common ancestral apicomplexan mitochondrion. We also identified a partial cDNA sequence coding for an alternative oxidase (AOX) gene, a component of the electron transport chain which can act as an alternative to the terminal mitochondrial respiratory complexes III and IV, which has not yet been reported in any other member of this phylum. Degenerate primers developed to identify selected mitochondrial genes failed to identify either cytochrome oxidase subunit I, or cytochrome b. Taken together, our data aim to provide new insights into the characterization of this Cryptosporidium organelle and a logical framework for future functional investigation.

Adaptive disorders of accommodation and vergence in binocular dysfunction

Disturbances of binocular vision are described clinically by the Duane-White classification in terms of the magnitude of the accommodative-convergence ratio (AC/A). Convergence excess and convergence insufficiency are assumed to result from high and low AC/A ratios respectively. It is assumed that the abnormal AC/A ratio is an independent variable that underlies abnormal phorias. However, recent studies have demonstrated that the AC/A ratio is inversely related to the adaptability of tonic accommodation (lens adaptation) and directly related to adaptability of tonic vergence (prism adaptation). We have tested whether clinical categories of convergence excess and convergence insufficiency are associated with insufficient and excessive adaptation of tonic accommodation and tonic vergence. Results demonstrate greater amplitude and duration of accommodative after-effects (lens adaptation) in the convergence insufficiency than the convergence excess group. Vergence after-effects (prism adaptation) had the reverse trend for the two groups. These results indicate that adaptive disorders of accommodation and vergence may underlie binocular disorders in symptomatic patients categorized as convergence excess and convergence insufficiency.

Treatment options in intermittent exotropia: a critical appraisal

Clinical opinions regarding treatment of intermittent exotropia (IXT) vary widely and there is controversy as to which treatment modality is most successful. This paper reviews the clinical literature related to five different treatment modalities used for IXT: overminus lens therapy, prism therapy, occlusion therapy, extraocular muscle surgery, and orthoptic vision therapy. Based upon review of 59 studies of treatment of IXT, and using each author's stated criteria for success, the following pooled success rates were revealed: over-minus lens therapy (N = 215), 28%; prism therapy (N = 201), 28%; occlusion therapy (N = 170), 37%; extraocular muscle surgery (N = 2530), 46%; and orthoptic vision therapy (N = 740), 59%. Success rates for IXT surgery differed depending upon whether a functional (43%) or cosmetic (61%) criterion was used to evaluate treatment success. These pooled success rates must be viewed carefully because nearly all the studies suffer from serious scientific flaws such as small sample sizes, selection bias, inadequately defined treatments and success criteria, absence of statistical analysis, and results reported in a manner that makes interpretation difficult. These problems indicate the need for a careful, circumscribed, and well controlled clinical trial to study the efficacy of different treatment modalities in remediating IXT.

Prevalence of domestic violence among patients attending a hospital emergency department

A cross-sectional study was conducted to determine the prevalence of domestic violence victims among patients using emergency services at Sydney's Royal North Shore Hospital, in an affluent urban area of New South Wales. This study used a self-administered questionnaire (used in a similar study at the Royal Brisbane Hospital) to investigate the history of domestic violence among patients attending the emergency department during 64 randomly selected nursing shifts in October-November 1994. Adult domestic violence was reported by 19.3 per cent of females and 8.5 per cent of males, confirming the results of the Brisbane study. Evidence for underreporting was found: 4 per cent of females and 6.3 per cent of males who did not report being victims revealed experiences of abuse on nine measures of types of violence, including six taken from the Conflict Tactics Scale. Results supported evidence from other studies suggesting that experience of abuse as a child is a risk factor for being in abusive relationships as an adult. In the past, comparison of results has been limited because of variation in definitions of domestic violence; this has been overcome by intentional replication of the Brisbane study. The study was enhanced by inclusion of patients from non-English-speaking backgrounds and a cohort of parents of children attending. Similar prevalence estimates were found in these groups. Results have implications for the detection and treatment of victims of domestic violence across all strata of society and have potential to raise awareness and affect attitudes towards this significant community problem.

Selective nonconjugate binocular adaptation of vertical saccades and pursuits

Hering's law describes the equal and symmetrical rotation of the two eyes. It is possible to calibrate the binocular yoking of the two eyes in response to disparate size and/or motion of the two ocular images. It is unclear if the ratio of movements by the two eyes is modified by selective adaptation of each versional system (i.e. saccades and pursuits) or if there is an apparent adaptation of Hering's law that results from a single underlying process. The latter could be accomplished by vergence (prism) adaptation, which could interact with all versional systems. In this investigation, binocularly stimulated saccades and pursuits were adapted separately for 2 hr to unequal vertical target displacements. Three adaptation paradigms were used; each included a 10% binocular gradient disparity. The adapting stimulus for the pursuit system was 0.25 Hz vertical triangular motion of 20 deg, peak to peak. Two saccade adaptation paradigms included one which emphasized correcting vertical disparity during the pulse component of the saccade, the other minimized the influence of disparity prior to, during and immediately after saccades (vergence paradigm). Yoking ratios (YRs) for vertical pursuits and saccades were compared before and after adaptation. The pursuit paradigm produced marked adaptation of the pursuit YRs while it had negligible effect on saccade YRs. The pulse saccade paradigm adapted the saccade YRs twice as much as the pursuit YRs whereas the vergence paradigm resulted in little adaptation of YRs for either saccades or pursuits. Pursuits adapted to the first paradigm in 15-30 min whereas saccades adapted to the second paradigm in 1.5-2 hr. These results indicate that there is not a single common nonconjugate adaptation mechanism for vertical pursuits and saccades. Results of the vergence paradigm demonstrate that feedback during or immediately after eye movements is necessary in order to stimulate the binocular versional adaptation mechanism. Versional adaptation may be considered as a calibration of Hering's law.

Novel hypotheses for the roles of EBNA-1 and BHRF1 in EBV-related cancers

Epstein-Barr virus has been linked to several types of human cancer including Burkitt's lymphoma and nasopharyngeal carcinoma but the mechanisms by which the virus might contribute to cancer remain obscure. Here we consider the possibility that EBNA-1, which is expressed in both tumours, directly transactivates cell genes. The EBNA-1 protein was tested for transcription transactivation domains and the human genome was screened for high-affinity EBNA-1-binding sites that might mediate transactivation. None were found, although novel low-affinity-binding sites in the EBV genome were detected. We also investigated the expression of BHRF1, the viral homologue to bcl-2, in epithelial cells and showed that it is expressed in vivo in the EBV replication found in oral hairy leukoplakia. A novel hypothesis is proposed for nasopharyngeal carcinoma in which BHRF1 expression protects cells against apoptotic death caused by environmental DNA damaging agents and thus contributes to the early stages of cancer development.

The nursing shortage revisioning the future

A severe shortage of nurses is being experienced nationally and globally. In South Florida, one of the most severely impacted regions in the world, a group of healthcare organizations, educational institutions, and nursing organizations formed the Nursing Shortage Consortium to combat the nursing shortage. Strategic efforts to recruit and retain nurses are underway, with a focus on nurturing interest among young people and increasing opportunities to stimulate their interest, to increase the supply of appropriately prepared professional nurses.

Current perspectives on maternity critical care

Maternal critical care is a developing area of clinical practice. Looking after a critically ill woman requires a multidisciplinary team that must endeavour to maintain the relative normality of pregnancy. Whilst consideration of the fetus should be taken when making clinical decisions regarding maternal care, unfounded concerns for the fetus can contribute to therapeutic inertia such that potentially life-saving therapies are denied to pregnant women. The management of a critically ill obstetric patient must reflect, as closely as possible, the management of critical illness outside pregnancy. We will discuss some of the current evidence and concepts around this emerging area in obstetrics, including enhanced maternity care, maternal medicine networks and clinical care.

Augmentation mammoplasty and 'silicone-osis'

BACKGROUND

Claims have been made that breast augmentation induces a previously unrecognized disease ("silicone-osis").

AIMS

To confirm the existence of "silicone-osis", qualify and quantify its characteristics.

METHODS

In this population-based retrospective cohort study, the health status of 458 female Sydney residents who had augmentation mammoplasty for cosmetic reasons ("augmentation mammoplasty-exposed" or "exposed" cohort) between 1979 and 1983 was compared with the health status of 687 female Sydney residents who had non-silicone-associated plastic surgery ("augmentation mammoplasty-nonexposed" or "non-exposed" cohort). Both groups were matched for age (+/- 5 years), year of plastic surgery (+/- 2 years), plastic surgeon, anaesthetist and mode of anaesthesia. Outcome measures comprised dummy symptoms to assess reporting bias, as well as symptoms and symptom clusters from a comprehensive 78-symptom list.

RESULTS

Dummy variables were not over-reported by the exposed cohort. The following individual symptoms developed more commonly in the exposed cohort after index plastic surgery: "memory loss/confusion", "altered bowel habit", "chest pain made worse by deep breathing", "shortness of breath after walking up 10 steps", "breast pain", "sweating mainly at night" and "tunnel vision". Of eight identified symptom clusters, three were rejected as biologically unimportant: "joint swelling of the bunion joint", "haemorrhoids" and "breast lumps" (the latter two occurring more commonly in the non-exposed cohort). In contrast, five symptom clusters were thought to have potential biological importance and occurred more commonly in the exposed cohort. The symptom "night sweats" was common to all five clusters, and comprised the sole symptom in one instance. The other four multisymptom clusters were also characterized by "low energy" (lethargy) and "pins and needles", whereas "breast pain", "impaired memory", "muscle pain" and "reflux", occurred in three of the four clusters.

CONCLUSION

Cluster analysis suggested the existence of a multisystem disorder occurring more commonly in the exposed cohort and characterized by night sweats, lethargy, breast pain, impaired mentation, reflux, paraesthesiae, hand muscle weakness and myalgia. The argument against this being a new disease entity --"silicone-osis"-- however, was its presence, albeit at lower frequency, in the silicone-unexposed cohort. Thus this study did not confirm the existence of a new disease entity "silicone-osis" uniquely and causally associated with silicone exposure. The possible interpretations of these findings are discussed.

Estradiol and progesterone receptors in breast cancer: prognostic value after relapse

The prognostic significance of estradiol (ER) and progesterone receptors (PgR) for survival from relapse has been studied in two groups of breast cancer patients: group 1, 35 patients in whom receptor levels were measured at the time of mastectomy; group II, 49 patients in whom receptor levels were measured at the time of recurrence. ER+ (greater than 10 fmoles/mg) patients had a better survival from relapse than ER- patients. High levels of PgR (greater than 50 fmoles/mg) had a prognostic significance only in group II patients.

Sugar or salt ("SOS"): A protocol for a UK multicentre randomised trial of mannitol and hypertonic saline in severe traumatic brain injury and intracranial hypertension

Hyperosmolar solutions are widely used to treat raised intracranial pressure following severe traumatic brain injury. Although mannitol has historically been the most frequently administered, hypertonic saline solutions are increasingly being used. However, definitive evidence regarding their comparative effectiveness is lacking. The Sugar or Salt Trial is a UK randomised, allocation concealed open label multicentre pragmatic trial designed to determine the clinical and cost-effectiveness of hypertonic saline compared with mannitol in the management of patients with severe traumatic brain injury. Patients requiring intensive care unit admission and intracranial pressure monitoring post-traumatic brain injury will be allocated at random to receive equi-osmolar boluses of either mannitol or hypertonic saline following failure of routine first-line measures to control intracranial pressure. The primary outcome for the study will be the Extended Glasgow Outcome Scale assessed at six months after randomisation. Results will inform current clinical practice in the routine use of hyperosmolar therapy as well as assess the impact of potential side effects. Pre-planned longer term clinical and cost effectiveness analyses will further inform the use of these treatments.

Magnitude estimates of cold pressor pain: effects of suggestions, cognitive strategy, and tolerance

Pain magnitude when subjects immersed an arm in ice water was assessed by means of a magnitude estimation procedure during baseline and posttest sessions. Before the posttest session, subjects either received or did not receive an analgesic suggestion. Best-fit functions were linear, though power fits were also good. Analgesic suggestions had no effect on the rate of change in pain intensity. When subjects were classified as copers or catastrophizers on the basis of written testimony, pain intensity increased more rapidly for catastrophizers than for copers during the posttest session but not during the baseline session. Subjects who kept their arm immersed for more than 240 s were classified as high in tolerance. High-tolerance subjects experienced a slower rate of growth in pain intensity than low-tolerance subjects. Theoretical implications of the results are discussed.

An unusual cause of chest pain: atraumatic clostridial myonecrosis

Atraumatic clostridial myonecrosis is a rare but potentially life-threatening infective condition which is thought to occur in elderly and immunocompromised subjects via bacterial translocation through the gut wall and distant haematological seeding. Previous case reports have mainly focused on an association with malignancy and bowel inflammation. The case is reported of an 84-year-old woman initially treated for cardiac chest pain, with a medical history comprising only of type 2 diabetes, hypertension and monoclonal gammopathy of unknown significance. Chest pain remains a common presentation to all emergency departments worldwide and, with increasing pressure for early intervention in cardiac causes, prehospital treatment is becoming more commonplace. Clinicians must be sure to make a thorough initial assessment and take care when prescribing cardiac medications for chest pain, owing to the vast spectrum of differential diagnoses.

A congenital abnormality masquerading as encephalitis in an 11-year-old girl

Craniopharyngiomas are reported to be the commonest non-glial tumours of childhood. The classic presentation is typically progressive, commonly manifested as visual field defects, growth abnormalities and/or endocrine disturbance. We report a case of an 11-year-old girl presenting in acute confusional state, with few historical factors suggestive of an intracranial mass lesion and no objective localising signs on examination. Although initially treated as encephalitis, neuroimaging revealed a large craniopharyngioma with acute hydrocephalus and bilateral frontal lobe compression. She was transferred immediately to the local neurosurgical unit and underwent reservoir drainage of the cystic tumour within 24 h. This resulted in immediate symptomatic resolution. This case highlights the importance of early cerebral imaging in the paediatric patient with diagnostic uncertainty and suggests a high index of suspicion for space-occupying lesions in children, despite perceived duration of symptoms.