Prospective evaluation of penetrating deep sclerectomy in advanced open-angle glaucoma: Filtration surgery adapted to resource scarcity in developing countries.

PURPOSE: Two of the hurdles that are facing ophthalmologists in developing countries are scarcity of resources and patient follow-up. Deep sclerectomy (DS) has proven less costly and more effective than topical therapies and has a more favorable safety profile than trabeculectomy. The main factors preventing its use in developing countries are the need to perform laser goniopuncture in 40-80% of cases to maintain filtration and the risk of postoperative iris incarceration. The purpose of this study is to assess the efficacy and safety profile in advanced open-angle glaucoma of a relatively new surgical technique designed to overcome this limitation: penetrating DS. SETTING: This was an investigator-initiated, prospective, interventional study, conducted at a single ophthalmology center in Kinshasa, Congo. The study was conducted in full compliance with the Declaration of Helsinki. METHODS: Fifty-one eyes (34 patients) with uncontrolled advanced primary open-angle glaucoma (visual field mean deviation<-10 dBs) were enrolled between October 2012 and June 2016. Age, gender, comorbidities (hypertension/diabetes), best-corrected visual acuity, topical medications, medicated and unmedicated intraocular pressure (IOP) were recorded. All patients underwent penetrating DS, during which, following standard dissection of the scleral flaps, the anterior chamber was penetrated through the trabeculo-Descemet membrane and an iridectomy was performed. Patients attended postoperative appointments at months 1, 3, 6 and 12. Surgical success was defined as a 20% reduction of IOP from baseline in conjunction with a 12-month unmedicated IOP≤12mmHg. RESULTS: The mean age was 64.5±14.0 years (44.1% female, 100% African). Mean IOP decreased from 20.2±6.1 (medicated) and 30.7±9.8mmHg (unmedicated) preoperatively to 12.1±4.1 at 12 months. Concomitantly, the number of topical medications decreased from 1.5±0.7 to 0.0. Complete surgical success was achieved in 64.7%. Four eyes (7.8%) were considered surgical failures due to uncontrolled IOP. None of the eyes lost light perception or required additional surgery. A significant association between surgical failure and hypertension was observed (HR=1.49; P=0.008). There were no intraoperative complications. Postoperatively, 4 bleb encapsulations (7.8%) and 1 iris incarceration (2%) were observed. CONCLUSIONS: The present study demonstrates that penetrating DS achieved similar efficacy and safety results to traditional non-penetrating DS. In addition, it showed a lower potential for intraoperative complications, which might be associated with a more benign surgical learning curve. Finally, the rates of serious postoperative complications (iris incarceration, choroidal effusion and hypotony) were significantly lower than in DS and trabeculectomy, and this technique does not require subsequent Nd: YAG laser goniopuncture to maintain filtration, making frequent follow-up visits less critical. In view of these findings, perforating deep sclerectomy could offer a viable option for glaucoma management in developing countries as well as worldwide.

Anomalous effects of hormone fragments on the measurement of parathyroid hormone by radioimmunoassay.

One of the basic assumptions underlying the use of radioimmunoassay and other competitive protein-binding assays is the homogeneity of the antigen or ligand. This assumption is not valid for the measurement of parathormone (PTH) because of the presence of fragments. Hence, there is a potential for errors and high variability in the measurement of parathyroid hormone (PTH) by radioimmunoassay. Even though region-specific radioimmunological and immunoradiometric assays for PTH measurement can overcome some of the difficulties caused by the presence of hormone fragments, the possibility for serious measurement errors still remains. We therefore examined experimentally and by modeling the impact of fragments on the estimation of the concentration of a highly purified intact bovine parathyroid hormone by radioimmunoassay. Our experimental results show that the mere presence of fragments can lead to a significant underestimation or overestimation of the amount of the intact hormone. The results have been simulated by a model in which fragments bind to the antibodies, thus competing with the intact hormone, and to the intact hormone as well, thereby reducing the amount of free intact hormone in competition with the radioligand. This work indicates that it may be preferable to consider alternative methods, other than competitive protein-binding assays, for the measurement of secreted PTH.

Anomerization and hydrolysis of lactose by beta-galactosidase from Saccharomyces lactis.

Beta-Galactosidase from Saccharomyces lactis was found to be able to catalyze both the anomerization of alpha-lactose and the hydrolysis of beta-lactose; the rate of hydrolysis appeared to be four times higher with a 1:1 mixture of alpha and beta lactose than with a freshly prepared solution of alpha-lactose. The enzyme was also found to be unable to hydrolyze alpha-lactose. Thus, it appears that beta-galactosidase from S. lactis has its hydrolytic activity on lactose adapted only to the naturally more abundant beta-lactose.

Separation and characterization of four enzyme forms of beta-galactosidase from Saccharomyces lactis.

beta-Galactosidase from Saccharomyces lactis has been purified to serve as a model for the kinetic behavior of human lactase in adult lactase deficiency. Enzymes from both species are neutral and follow Michaelis-Menten kinetics. beta-Galactosidase of S. lactis is more readily available than the human lactase. An enzyme preparation from S. lactis (Maxilact 40,000), which is used commercially to hydrolyze lactose in milk, has been found to contain four isozymes of beta-galactosidase. Methods have been developed for the separation and purification of each of the four enzymes. The enzymes were found to differ in molecular mass, kinetic behavior, isoelectric point, response to pH, specific volume and sensitivity to metal ions. The four enzymes had apparent molecular masses of 630 kDa, 550 kDa, 41 kDa and 19 kDa. Their specificity constants (kcat/Km) were found to be 42.0, 355.2, 0.38 and 0.48 mM-1 s-1, respectively. The techniques of reiterated ultrafiltration used for the isolation of these isozymes may be applicable to other purification processes.