Biomedical subjects

R M Nuijts

Publications and source records attributed to R M Nuijts.

9 recordsLinked to original sources

PubMed2001

Rigid gas-permeable contact lens fitting in LASIK patients for the correction of multifocal corneas.

BACKGROUND: Laser in situ keratomileusis (LASIK) has recently become the most commonly performed refractive surgery procedure. Results are promising in correcting low to moderate myopia. Most complications occur during the surgeon's learning curve. One of the complications is a decentration of the ablated area that causes monocular diplopia and a nocturnal halo phenomenon due to a multifocality of the corneal surface overlying the entrance pupil. The corneal shape is significantly altered after LASIK. We evaluate the efficacy of rigid gas-permeable contact lens designs and fitting techniques used in eight eyes with multifocal LASIK ablations to correct haloes and impaired night vision complaints. METHODS: We used large-diameter tetra-curved rigid gas-permeable (RGP) contact lenses for visual recovery in eight eyes of seven LASIK patients. We used the power on the transition zone of the corneal topographic map, 0.2 mm outside the ablated refractive area, for selection of the back optic zone radius of the RGP contact lenses. Procedures for lens fitting are described. Visual acuity (high-contrast logarithm of the minimum angle of resolution, LogMAR) was measured before- and 6 months after contact lens fitting. RESULTS: Large-diameter tetra-curve RGP lenses with a mean diameter of 11.85 (SD 0.16) mm were successfully used in LASIK patients with multifocal corneas. Mean best spectacle-corrected visual acuity was +0.3 LogMAR (SD 0.19; in Snellen equivalent, 20/40) and improved significantly with the contact lenses to +0.08 LogMAR (SD 0.11; in Snellen equivalent, 20/25, P=<0.01). During the follow-up period of 16.7 months, the average daily wearing time of the lenses was 12.5 h. Contact lenses with a standard geometry were not useful due to excessive movement and inadequate centration. CONCLUSIONS: Contact lenses with large diameters, in combination with selection of the back optic zone radius 0.2 mm peripheral of the refractive ablation zone, facilitate contact lens fitting to restore best-corrected visual acuity in LASIK patients with multifocal corneas.

Adult↗

PubMed2001

A new technique for rigid gas permeable contact lens fitting following penetrating keratoplasty.

PURPOSE: To evaluate a new, rigid gas permeable contact lens fitting technique following penetrating keratoplasty. METHODS: For the correction of postoperative anisometropia or astigmatism, a rigid gas permeable, tetra-curve contact lens with an overall diameter of 12.0 mm and a back optic zone diameter of 8.5 mm was fitted in 36 eyes of 33 patients, 7 months after penetrating keratoplasty. The contact lens back optic zone radius was selected using the videokeratography values over the elevated edges of the transplant wound (with the sutures in place). Graft clarity, visual outcome, and corneal topography were evaluated up to 3 years after surgery at intervals of 6 months. RESULTS: Throughout the follow-up period (range 6-36, mean 19.3+/-sd 11.8 months), all grafts remained clear. Mean contact lens daily wearing time averaged 13.6 (+/- sd 4.7) hours. Mean best-corrected visual acuity improved from +0.36 (+/- sd 0.18) LogMAR with spectacles to +0.11 (+/- sd 0.11) LogMAR with contact lenses (p < 0.0001). One patient was excluded from the study due to a lack of motivation and one had an adverse reaction to the stitches. CONCLUSIONS: To improve the visual performance following penetrating keratoplasty, the described fitting technique, guided by videokeratography, eased selection of the back optic zone radius of the initial trial lens. The large diameter contact lenses with a tetra-curve design were well tolerated in all patients for more than 13 hours daily.

Adult↗

PubMed2000

Biodegradable three-dimensional networks of poly(dimethylamino ethyl methacrylate). Synthesis, characterization and in vitro studies of structural degradation and cytotoxicity.

In ophthalmology, there is a need for novel degradable biomaterials for e.g. controlled drug release in the vitreous body. These degradable materials should feature both excellent biocompatibility, and well-defined kinetics of degradation. In most cases, poly(D,L-lactic acid), or poly(lactic-co-glycolic acid) are used. These materials, however, suffer from some serious drawbacks, since the degradation kinetics are difficult to control, especially since the so-called 'burst-degradation' occurs. Here, we describe a set of novel polymeric networks which largely consist of poly(dimethylamino ethyl methacrylate) (poly(DMAEMA)); these materials are crosslinked via a dimethacrylate molecule that contains two carbonate groups. This system is susceptible to hydrolytic scission. The degradation products do not exert a catalytic effect on the ongoing degradation reaction (i.e. there is no burst effect). We describe the synthesis of three of these materials, which differ merely with regard to the crosslinker content. These materials were characterized through DMTA, 1H NMR and FT-IR spectroscopy, and scanning electron microscopy. The reaction DMAEMA + 2-hydroxyethyl methacrylate (HEMA) was studied in detail, using 1H NMR spectroscopy, and these experiments revealed that the reaction of DMAEMA and HEMA produces a random (Bernouillian-type) copolymer. From this, we contend that the new materials have more or less uniform distribution of the crosslinks throughout their volume. Structural degradation of the three materials was studied in vitro, at pH 7.4, 9.1 and 12.0. It is found that the materials exhibit smooth hydrolysis, which can be controlled via the crosslink density and the pH, as was expected a priori. It should be noted that degradation of these materials produces non-hydrolysable, but water-soluble, oligo(DMAEMA) and poly(DMAEMA) molecules. We subsequently performed in vitro studies on the biocompatibility of these materials. The MTT cytotoxicity assay revealed that the materials were cytotoxic to chondrosarcoma cells. This is most probably due to local increase of the pH due to the basic character of the pending dimethylamino groups. Cytotoxicity remained virtually unchanged after extended washing with water. This indicates that the cytotoxicity is an intrinsic property of the material and was not caused by remnants of free monomer. Cytotoxicity was also seen in cell cultures (human fibroblasts isolated from donor corneas) which were grown in contact with the materials. It is concluded that the new materials have attractive degradation characteristics, but their cytotoxicity makes them unsuitable for applications in ophthalmology.

Biocompatible Materials↗

PubMed2000

Determinants of patient satisfaction after cataract surgery in 3 settings.

PURPOSE: To analyze the determinants of satisfaction and postoperative visual function after cataract surgery in 3 settings in The Netherlands. SETTING: University Hospital Maastricht (outpatient care), Atrium Medical Center Heerlen (inpatient care), and Medical Center Maastricht Annadal (outpatient care), Maastricht, The Netherlands. METHODS: This cross-sectional study consisted of 150 patients of 50 years and older who had first-eye phacoemulsification with intraocular lens implantation. Data were collected by a written questionnaire. The following parameters were measured: medical outcome, postoperative function, patient satisfaction with medical outcome and hospital care, and overall patient satisfaction. RESULTS: In general, patients were very satisfied (mean score 8.43 on a 10-point scale ranging from 1 = very bad to 10 = excellent). The 3 centers did not differ regarding the patient satisfaction (P =.092). However, postoperative visual function (P =.012), counseling (P =.010), and waiting time (P <.001) were different among the settings. Patient satisfaction with hospital care had a stronger correlation with overall satisfaction than patient satisfaction with the medical outcome (r = 0.669 versus r = 0.543, respectively). CONCLUSIONS: A causal model of patient satisfaction was tested, indicating that satisfaction was related to the patient's preoperative expectations and the quality of care given during the hospital stay and follow-up at the outpatient clinic. This emphasizes the relevance of patient education (to set realistic expectations) and counseling (need for care) by hospital staff in a cataract surgery setting.

Aged↗

PubMed2000

Tailoring of new polymeric biomaterials for the repair of medium-sized corneal perforations.

The aim of this study was to investigate whether polymeric biomaterials can be designed such that they become suitable for surgical closure of medium-sized perforations in the cornea, the transparent tissue in the front of the eye. Such a biomaterial must meet stringent requirements in terms of hydrophilicity, strength, transparency, flexibility, and biocompatibility. Four different copolymers of n-butyl methacrylate (BMA) and hexa(ethylene glycol) methacrylate (HEGMA) were prepared and characterized. Poly(BMA) was made as a reference material. Physicochemical properties were measured (contact angles, glass-transition temperatures, thermal degradation, water uptake and swelling), and cytotoxicity in vitro was assessed with a MTT test. Moreover, the interaction between the materials and cultured human corneal epithelial cells was studied. The copolymers may be useful for temporary closure of corneal perforations.

3T3 Cells↗

PubMed2000

Phacotrabeculectomy.

The outcome of combined same-site phacoemulsification, posterior chamber lens implantation and trabeculectomy was retrospectively studied in patients with cataract and moderately controlled glaucoma, with a follow-up of at least 6 months. Primary phacotrabeculectomy without antimetabolites was performed in 74 patients. Mean IOP decreased from 22.8 to 14.3 mm Hg (35.3%). A maximum IOP of 19 mm Hg without glaucoma medication was reached in 66.2%. Mean logMAR visual acuity increased from 0.58 to 0.30. Primary phacotrabeculectomy has been shown to be a safe and effective procedure with good IOP control and rapid visual rehabilitation.

Aged↗

PubMed2000

Evaluation of a new system of lens parameter selection and comparison of traditional vs one-step lens care systems for aspheric high-Dk RGP contact lenses.

PURPOSE: We investigated the value of newly developed systems for parameter selection on the performance of high Dk rigid gas permeable (RGP) contact lenses with a spheric-aspheric design made of Boston Equa material in normal daily wear conditions. A comparison was also made between the safety and efficacy of a traditional care system vs a one-step chemical care system during the follow-up period of 1 year. METHODS: A total of 66 patients were randomly assigned to traditional and newly developed systems for computing the back optical zone radius (BOZR) and the total diameter (TD) of the lenses. Evaluation parameters incorporated assessment of fit, visual acuity, wearing time, comfort, and lens condition. RESULTS: The traditional method of computing the BOZR, using a method based on flat-K, predicted the BOZR successfully in 83% of the cases. Corneal topometry reached a lower, but not significantly different (P > 0.01) value of 75% correct prediction of BOZR. Analysis of the differences in eccentricity (E) values between quadrants per eye was a significant (P < 0.001) factor in fault predictions in the topometric system. A newly developed guide forTD selection performed, with 90% correct predictions, significantly (P < 0.01) better than a traditional method (72%) based on corneal diameter on supraversion. No significant differences (P > 0.05) were found in the capabilities of care systems (a traditional care system using a surfactant cleaner vs a one-step solution) to keep the lenses in proper condition and without deformation, over the 1 year follow-up period. The final success rate was 85%. CONCLUSIONS: Although high Dk RGP contact lenses can be fit and used with a 85% success rate using advanced systems for determining the BOZR and TD, it remains necessary to evaluate the fit before dispensing high Dk RGP lenses in 15% of the cases. The one-step solution used in this study was a good starting point for lens care. If needed, surfactant cleaning in the traditional care system can be done without the risk of lens deformation.

Adolescent↗

PubMed1999

Autologous limbal transplantation in unilateral chemical burns.

PURPOSE: To describe the results of autologous limbal transplantation in the treatment of unilateral chemical burns. PATIENTS AND METHODS: Two patients, a 40-year-old male (case 1) and a 35-year-old male (case 2), experienced grade III chemical trauma and were treated with autologous limbal grafting (case 1) after a postaccident period of 3 and 9 months, respectively. Change in visual acuity, epithelial healing time and postsurgical topography healing patterns were documented. RESULTS: Snellen visual acuity improved from 0.1 to 1.0 in both cases. Epithelial healing time for cases 1 and 2 were 4 and 2 weeks, respectively. Corneal topography of case 1 showed an induced inferior steepness type of asymmetrical astigmatism in the graft area. Serial topography showed no induced astigmatism in the donor eyes. CONCLUSION: Autologous limbal grafting is an adequate treatment for selected cases of unilateral chemical burns and facilitates rapid improvement in visual function. Early limbal grafting in case 1 resulted in rapid re-epithelialization and prevention of complications.

Adult↗

PubMed1997

Mitomycin C primary trabeculectomy in primary glaucoma of white patients.

PURPOSE: To evaluate the clinical outcome of eyes which underwent primary trabeculectomy with adjunctive mitomycin C (MMC) for primary glaucoma. PATIENTS AND METHODS: A prospective analysis of 25 eyes in 23 patients who underwent primary trabeculectomy with MMC for primary glaucoma was performed. Clinical outcome measures including postoperative intraocular pressure, change in logarithm of the minimum angle of resolution (LogMAR) visual acuity, and incidence of complications were measured up to 1 year postoperatively. RESULTS: Mean intraocular pressure decreased from 26.0 +/- 4.4 mmHg preoperatively to 12.5 +/- 3.9 mmHg (p < 0.0001) 1 year postoperatively. The mean LogMAR visual acuity changed from 0.23 +/- 0.19 preoperatively to 0.23 +/- 0.20 1 year postoperatively (p = 1.0). One eye developed a temporary hypotonous maculopathy and 4 eyes progressed in cataract formation. CONCLUSION: Primary trabeculectomy with MMC in eyes with primary glaucoma showed excellent pressure reduction. There were no cases of persistent hypotonous maculopathy or bleb endophthalmitis.

Antimetabolites↗