Keratoconus: The ABCD Grading System.

PURPOSE: To propose a new keratoconus classification/staging system that utilises current tomographic data and better reflects the anatomical and functional changes seen in keratoconus. METHOD: A previously published normative database was reanalysed to generate both anterior and posterior average radii of curvature (ARC and PRC) taken from a 3.0 mm optical zone centred on the thinnest point of the cornea. Mean and standard deviations were recorded and anterior data were compared to the existing Amsler-Krumeich (AK) Classification. ARC, PRC, thinnest pachymetry and distance visual acuity were then used to construct a keratoconus classification. RESULTS: 672 eyes of 336 patients were analysed. Anterior and posterior values were 7.65 ± 0.236 mm and 6.26 ± 0.214 mm, respectively, and thinnest pachymetry values were 534.2 ± 30.36 µm. The ARC values were 2.63, 5.47 and 6.44 standard deviations from the mean values of stages 1-3 in the AK classification, respectively. PRC staging uses the same standard deviation gates. The pachymetric values differed by 4.42 and 7.72 standard deviations for stages 2 and 3, respectively. CONCLUSION: A new keratoconus staging incorporates anterior and posterior curvature, thinnest pachymetric values, and distance visual acuity and consists of stages 0-4 (5 stages). The proposed system closely matches the existing AK classification stages 1-4 on anterior curvature. As it incorporates posterior curvature and thickness measurements based on the thinnest point, rather than apical measurements, the new staging system better reflects the anatomical changes seen in keratoconus.

Performance evaluation of non-porous versus porous ion-exchange packings in the separation of proteins by high-performance liquid chromatography.

The performance of a non-porous, anion-exchange packing was evaluated and compared with a number of similar porous high-performance liquid chromatography packings. The non-porous columns were found to be equally efficient for proteins spanning a wide range of molecular weights, while the porous columns exhibited decreasing efficiency as the proteins became larger. The porous materials also exhibited size exclusion effects that were not seen with the non-porous materials, which partially accounts for the loss of efficiency with large proteins. When increasingly steep gradients were employed, the loss of resolution was less with the non-porous materials.

Factors associated with variation in the consultation rates of children aged under five years.

In a large urban practice, all families with a child aged under five years were identified and, after suitable exclusions, 294 (80%) of the 369 families approached cooperated in the study. For each child, the number of parentinitiated first consultations in a one-year period was extracted from general practice records, and mothers were asked to provide additional information by postal questionnaire, which included a test of the mother's reaction to a series of hypothetical child ;illness situations'.The most important factors found to be associated with higher rates of consultation were increased urgency of the mother's reaction to the test situations and attendance of the child at a pre-school group. Children with low consultation rates tended to be younger and more likely to come from larger families; their mothers generally spent less time in regular employment outside the home and were more likely to be single parents. The effect of family size was independent of maternal age and no socioeconomic gradient was found. There was also no evidence that differences in frequency of consultation were related to particular diagnostic categories. The mothers' sources of advice in the postulated event of their child becoming unwell are also described.

Rapid cation-exchange chromatography of hemoglobins and other proteins.

A new, weak cation exchanger (MA7C) is useful for the very rapid resolution of protein mixtures. MA7C columns (30 X 4.6 mm I.D.) are packed with non-porous spherical particles (7-micron in diameter) having carboxylic acid ion-exchange groups. These columns can readily separate human hemoglobin A1c from other hemoglobin species in 7 min. Quantitative results agree well with those of accepted techniques. Other separations are possible with flow-rates up to 5 ml/min. Chromatography on MA7C columns is characterized by very narrow bandwidths, even at high flow-rates.

Rapid protein profiling with a novel anion-exchange material.

A new anion-exchange material has been developed which allows very rapid resolution of protein mixtures. The Microanalyzer MA7P matrix consists of small (7 micron), spherical, non-porous, polymethacrylate beads with polyethyleneimine (PEI) covalently coupled to the surface. When packed 30 X 4.6 mm I.D. columns, this matrix is particularly well suited for applications in which 1-300 micrograms of a protein mixture must be resolved in a minimum of time. Recoveries of injected proteins are usually quantitative, even when the amounts of individual proteins are in the submicrogram range. Chromatography on Microanalyzer MA7P columns is characterized by very narrow bandwidths, even at relatively high flow-rates. This is due to the combined effects of short column length, high selectivity, and the lack of velocity-dependent bandbroadening attributable to diffusion into and out of pores. These columns have no discernable gel filtration effects in the molecular weight range from 10(3) to 10(6) daltons. Columns are very rapidly equilibrated with new solvents, further reducing cycle-to-cycle times.