The results are reported of 38 ultrasonographic in vivo mensurations of intraindividual differences in axial thickness between a cataractous lens in one eye and a biomicroscopically clear or slightly cataractous lens (incipient deep cortical opacity) in the other. Obviously intumescent cataractous lenses were excluded. In general, the cataractous lens was thinner than the contralateral clear or slightly cataractous lens. Large decreases in lens thickness appeared in lenses with the capsule-near opacities of posterior subcapsular cataract (PSC) + anterior capsular/subcapsular opacity (ACSCO). PSC was more closely correlated to lens thinning than was ACSCO. Nuclear cataract very often occurred in thin lenses, but did not appear to cause lens thinning per se. Deep cortical opacity was not associated with lens thinning. The present results contributed to our argumentation that the decrease in lens thickness is due to a leak of lens material through the "lens membrane" beside a possible cessation of growth of the lens fibres.

The concentrations of some ribonucleoside tri- and diphosphates, adenosine-5'-monophosphate, L-lactate and pyruvate were determined in human senile cataractous lenses removed during cataract operations. Pyruvate concentrations were found to be negligible (median = 56 mumol/kg lens wet weight) in 15 human senile cataractous lenses. On the basis of correlations between the biomicroscopic appearances of the senile cataractous lenses (N = 80) and the concentrations and ratios of the metabolites in question, the following classification was found to be justified: 1. Immature cataractous lenses without anterior capsular/subcapsular opacity: high levels of ribonucleoside triphosphates (RTP), high sums of RTP, ribonucleoside diphosphates (RDP), and adenosine 5'-monophosphate (AMP) as well as high levels of L-lactate and high ratios of L-lactate in the lens/L-lactate in the aqueous. 2. Immature cataractous lenses with anterior capsular/subcapsular opacity; intermediate levels of RTP, intermediate values for the sums of RTP, RDP, and AMP, high L-lactate levels, and intermediate values of the ratios of L-lactate in the lens/L-lactate in the aqueous. 3. Totally opaque lenses, which all had extensive anterior capsular/subcapsular opacity; low values for the concentrations of lens RTP, for the sums of RTP, RDP and AMP, and for lens L-lactate. Low ratios of L-lactate in the lens/L-lactate in the aqueous.

In 49 human senile cataractous lenses the sodium and potassium concentrations of the lens water as well as the water and dry weight percentages were examined. It was found justifiable to classify the lenses into three categories on the basis of correlated biomicroscopic and biochemical findings: 1. Immature cataractous lenses without anterior capsular/subcapsular opacity (ac-sco) were characterized by low CNaL+, high CKL+ and low sums of CNaL++CKL+. 2. Immature cataractous lenses with ac-sco were characterized by intermediate value of CNaL+ and CKL+, as well as high sums of CNAL++CKL+. 3. Totally opaque lenses (these lenses had 80-100% of ac-sco) were characterized by high CNaL+, low CKL+, high sums of CNaL++CKL+, high water, and low dry weight percentages. It was found that in immature cataractous lenses increasing extension of ac-sco was correlated to increasing CNAL+ and increasing ratios of CNAL+/CNAA+ as well as to decreasing CKL+ and decreasing ratios of CKL+/CKA+. The sums of CNaL++CKA+ increased. There was a correlation of the extent of ac=sco to the water and dry weight percentages of the immature senile cataractous lenses with ac-sco, viz. a negative correlation for water and a positive one for the dry weight. However, these latter two correlations may be due to chance significances, the level of significance being only greater than P greater than 0.02 in both instances. Lenses which were estimated to have larger than or equal to 30% of ac-sco were found to be more opaque than lenses with less than or equal to 25% of ac-sco.

Light- and electron-microscopic studies of human senile cataractous lenses with and without biomicroscopically detectable anterior capsular/subcapsular opacity (ACSCO) revealed the main difference between the two types of cataract to be in the subepithelial cortex, where ACSCO lenses showed disintegrating cortex fibres, fibres of the deep cortical type and even in some cases collapsed fibres. These findings were considered to be associated with the decomposition and disappearance of the superficial cortex in ACSCO lenses. Numerous mitochondria in the epithelium of ACSCO lenses point towards a high oxidative metabolism, which may facilitate active transport across the epithelium. No difference in capsular surface morphology between cataractous lenses with and without ACSCO was found by scanning electron microscopy. Transmission electron microscopy showed in both categories of lenses granular inclusions in the capsules, most pronounced in totally opaque lenses. Large intercellular vacuoles were seen in the anterior part of the epithelium, both light- and electron-microscopically in both categories. Consequently, these ultrastructural changes do not seem to form part of the biomicroscopical picture of ACSCO. Based on our study, we prefer the term: ASCO (anterior subcapsular opacity) in place of ACSCO, the latter term having been used by us previously.