Biomedical subjects

G van Rij

Publications and source records attributed to G van Rij.

At least 19 recordsLinked to original sources

PubMed2000

Intrastromal corneal ring segments (ICRs): three- and six months results.

In the period from May 1997 to November 1998 twenty-one eyes of fifteen patients with sighted eyes received Intrastromal Corneal Ring Segments (ICRS) for the surgical treatment of low myopia. The mean pre-operative refraction was -3.0 diopters (D) ranging from -1.5 D to -4.1 D. Three months results showed that 44% of the treated eyes had an uncorrected visual acuity (UCVA) of 1.0 or better while 94% had an UCVA of 0.5 or better. In 94% the postoperative refraction was within one diopter (D) of emmetropia and in 61% within 0.5 D of emmetropia. Mean induced astigmatism was 1.03 (std 0.75). The best spectacle corrected visual acuity (BSC VA) after 3 months was 1.0 or better in all patients. After six months the UCVA was 1.0 or better in 43% of the treated eyes while in 100% the UCVA was 0.5 or better. The post-operative refraction was within 1 D of emmetropia in 100% and within 0.5 D of emmetropia in 81%. Mean induced astigmatism was 1.00 (std 0.50). BSCVA was in 88% 1.0 or better and in 100% 0.9 or better. In one patient vascular ingrowth occurred due to a ring segment located under the incision. Three patients experienced a lower UCVA due to postoperative astigmatism. In only one patient in this series the ICRS were removed because of induced astigmatism. These preliminary results show that the ICRS seem to offer a safe, stable and reproducible method to correct low myopia. The operation carries a low risk but care must been taken to insert the ICRS as central as possible to prevent postoperative astigmatism.

Adult↗

PubMed2000

Delayed graft rejection in pre-vascularised corneas after subconjunctival injection of clodronate liposomes.

PURPOSE: To test the effects of clodronate liposomes on graft survival and neovascularisation after transplantation in pre-vascularised recipient corneas. METHODS: Corneal neovascularisation was induced in F344 rats by injecting heat inactivated rabbit serum intrastromally. After 4 weeks F344 rats were orthotopically grafted with corneal buttons from DA rats. Directly after transplantation and on 2, 4, 6 and 8 days postoperatively clodronate liposomes were administrated subconjunctivally in one group, whereas the other group remained untreated. For 60 days grafts were observed for signs of graft rejection and neovascularisation. RESULTS: Graft survival was significantly prolonged, but not prevented in clodronate liposome treated rats compared to untreated rats ( p =.004). Also clodronate liposome administration delays growth of corneal neovascularisation after transplantation. CONCLUSIONS: Previous studies revealed that clodronate liposomes prevent corneal graft rejection and reduce neovascularisation in orthotopic corneal allotransplantation in rats. This study shows that also in pre-vascularised recipient corneas subconjunctival administration of clodronate liposomes seems to delay corneal graft rejection and reduces neovascularisation.

Animals↗

PubMed2000

Effect of macrophage depletion on immune effector mechanisms during corneal allograft rejection in rats.

PURPOSE: In rats, corneal allograft rejection is delayed for at least 100 days by clodronate liposomes. These liposomes selectively deplete macrophages. To investigate the immunologic basis for absence of graft rejection in treated rats, the effect of these liposomes on the generation of cytotoxic T lymphocytes (CTLs) and antibody production after orthotopic corneal allotransplantation was determined. METHODS: Transplantations of corneal buttons from PVG rats were performed in AO rats. After surgery, one group received clodronate liposomes subconjunctivally at five time points, and the other group remained untreated. On postoperative day (POD) 3, 7, 12, or 17, rats were killed, the presence of CTLs was investigated at three different anatomic locations, and antibodies against donor antigens were tested. RESULTS: No significant differences were found between the groups tested 3 and 7 days after surgery. But on POD 12 (the time of onset of rejection in the untreated group) and on POD 17, the CTL activities detected in the submandibular lymph nodes (P < or = 0.008) and the spleen (P < or = 0.009) were significantly less in the treated groups compared with the untreated groups. In the untreated groups complement-independent antibodies were present only on POD 17, whereas no antibodies were found in the treated rats. CONCLUSIONS: Local treatment with clodronate liposomes was shown to downregulate local and systemic CTL responses and to prevent the generation of antibodies. Local depletion of macrophages in the initiation phase of the immune response appears to lead to a less vigorous attack on the grafted tissue and therefore to promote graft survival.

Animals↗

PubMed1999

Endoluminal pulse oximetry of the sigmoid colon and the monitoring of the colonic circulation.

Colonic ischaemia is a frequently observed serious complication following abdominal aortic reconstruction. For adequate treatment of this disorder, early diagnosis and resection of the diseased colon is essential. The purpose of this study was to evaluate a new method, based on pulse oximetry, to detect colonic ischaemia at an early preclinical stage. During a 7-year period (1989-1995) colonoscopy and pulse oximetry were performed in all patients at risk of colonic ischaemia: complicated acute or elective aortic reconstructions, colostomies with superficial necrosis and in patients who underwent uncomplicated aortic reconstruction and non-ischaemic colonic problems (n = 90). The sensitivity, specificity and positive predictive values, and negative predictive value, were calculated. All patients, except four for whom an acute relaparotomy was necessary, subsequently underwent colonoscopy combined with endoluminal pulse oximetry. Of the 90 patients, 30 had colonic ischaemia according to endoscopy (n = 26) or relaparotomy (n = 4), and in 33 patients the absence of pulsatile signal was detected by means of pulse oximetry. Thus, in three patients, pulse oximetry was falsely positive for colonic ischaemia. The calculated sensitivity and specificity of pulse oximetry were 100 and 95%, respectively. In comparison to other methods used for early detection of colonic ischaemia, pulse oximetry appears to be a promising method for the evaluation and monitoring of colonic ischaemia because it is non-invasive and easy to apply with a high sensitivity and specificity.

Adult↗

PubMed1998

Efficacy of ophthalmic solutions to detach adhering Pseudomonas aeruginosa from contact lenses.

PURPOSE: To compare the efficacies of two all-in-one contact lens (CL) cleaning solutions and a detergent mixture on the detachment of a pathogenic bacterium adhering to two types of contact lenses in the absence and presence of a tear film. METHODS: Bacterial-detachment studies were carried out in a parallel-plate flow chamber. Rigid gas permeable (RGP) CLs with and without a tear film were fixed on the bottom plate of the flow chamber. After adhesion of Pseudomonas aeruginosa no. 3, bacterial detachment was stimulated by perfusing the system either with an all-in-one CL-cleaning solution, for soft contact lenses (SCL solution) and for rigid lenses (RCL solution), or with a detergent mixture of 0.25% (wt/vol) sodium lauryl sulfate (SLS) and 0.2% sodium methyl cocoyl taurate (Tauranol). In addition, the all-in-one RCL-cleaning solution supplemented with 0.025% (wt/vol) SLS and 0.02% (wt/vol) Tauranol was evaluated. A surface physical-chemical analysis of the lenses before and after application of the solutions was done to determine whether remnants of the ophthalmic solutions or detergents could be found adsorbed to the CL surfaces. RESULTS: Both all-in-one CL-cleaning solutions stimulated minor bacterial detachment from CL surfaces with or without a tear film. The SLS/Tauranol detergent mixture, however, removed < or = 95% of the adhering P. aeruginosa cells, whereas the RCL-cleaning solution supplemented with detergents also stimulated significant detachment. Surface physical-chemical analysis clearly demonstrated the presence of a tear film on the CL surfaces, but remnants neither of the ophthalmic solutions nor of the detergents could be found. CONCLUSION: Ophthalmic solutions are not effective in stimulating detachment of adhering bacteria from CL surfaces. Supplementing of an all-in-one CL-cleaning solution with only small amounts of detergents yielded a solution much more effective in stimulating bacterial detachment while leaving no detectable remnants of the ophthalmic solution or of the detergents on the CL surfaces.

Bacterial Adhesion↗

PubMed1997

Triple procedure; analysis of outcome, refraction, and intraocular lens power calculation.

AIMS: A total of 97 triple procedures performed over a 6 year period were studied retrospectively to determine the best approach to calculate intraocular lens power. METHODS: The cases were divided into two diagnostic categories. RESULTS: After 1 year best corrected visual acuity was 20/40 or better in 37.5% of the cases of the 'modified group'. This group consists of patients with the diagnosis Fuchs' dystrophy, non-guttate endothelial dystrophy, and Reis-Buckler dystrophy. Analysis of visual acuity was made using logMAR. A final postoperative refraction within 2 dioptres of predicted refraction was achieved in 76.5% of patients in the modified group. CONCLUSION: In future, in the absence of a keratometry, a keratometry value of 7.49 mm will be used for calculation of the power of the implant as analysed in this study.

Adult↗

PubMed1996

Hydrogel intracorneal lenses in aphakic eyes.

BACKGROUND: The theoretical benefits of synthetic keratophakia over conventional corneal lamellar procedures are the elimination of donor concerns and superior refractive predictability. Additionally, synthetic material can be inspected for optical quality and power, and it can be sterilized. Furthermore, visual recovery should be more rapid since epithelium is not removed from the central part of the cornea and the need for keratocyte repopulation is eliminated. OBJECTIVE: To present results on patients who received an intracorneal implant (Kerato-Gel, Allergan Medical Optics, Irvine, Calif) that was made from lidofilcon A, a glucose-permeable hydrogel with an equilibrium water content of 68%. METHODS: The intracorneal implants were implanted in 35 adult patients for correction of aphakia. Inclusion criteria excluded patients with aphakia who were candidates for intraocular lenses. RESULTS: A total of 19 patients were followed up through 2 years postoperatively. For 16 patients with 2-year postoperative refractive data, the average spherical equivalent was -0.63 +/- 2.07 diopters (D). At 2 years, 88% of patients were within +/- 3.00 D of plano and 50% were within +/- 1.00 D. the mean change in Snellen's line for corrected visual acuity was -3.25 lines at 2 years for all patients and -2.0 lines for a subgroup of five patients who were free of vision-limiting preoperative disease. CONCLUSIONS: Results suggest that this intracorneal implant is well tolerated by the cornea and can provide predictable refractive results in patients with high-risk aphakia. Limitations of the procedure are uneven microkeratome resections, loss of best-corrected visual acuity, and irregular astigmatism in some patients. Although these data show good evidence of biocompatibility of the implant material, technical surgical progress is needed to advance this procedure into clinical therapeutic practice.

Adult↗

PubMed1995

Toxic keratopathy due to the accidental use of chlorhexidine, cetrimide and cialit.

Due to economical reasons some ophthalmologists are using an irrigating solution made by the hospital pharmacy instead of the commercially available solutions. These irrigating solutions come in bottles which are identical to the ones used for other solutions. During the last three years bottles were accidentally mixed up five times. Consequently, bottles containing solutions such as chlorhexidine, cetrimide, chlorhexidine/centrimide and cialit solutions were used during cataract surgery. This resulted in immediate corneal edema which, in its turn resulted in a bullous keratopathy. Four patients underwent a penetrating keratoplasty. In one patient the cornea was covered with a conjunctival flap. Light microscopy of the corneas included epithelial edema, loss of keratocytes, and a disrupted and sometimes absent endothelial cell layer.

Aged↗

PubMed1995

Morphometric analysis of the corneal endothelium with three different specular microscopes.

The morphometry of the central corneal endothelium of 10 eyes in 10 subjects was analyzed with three different specular microscopes. Computer-assisted analysis was performed with only two microscopes (Zeiss and Keeler Konan sp 3300) because the third microscope (Topcon sp 1000) could not be adapted to our computerized system. With this Topcon microscope a grid with standard densities was used to compare the images with, in addition, we also performed manual cell counting on the same Topcon images. The coefficient of variation of the cell analysis of three different images per cornea with the four methods varied between 3.4 and 4.7 percent. One-way analysis of variance showed a significant difference between the Zeiss and the other microscopes. So only the Keeler Konan and the Topcon microscopes could be used interchangeably. The computerized image analysis permitted also an evaluation of the hexagonality. The results of polygonality were not significantly different between the Zeiss and the Keeler Konan. For clinical purposes the Topcon specular microscope is more advantageous than the other two methods, since it is the most rapid way to record and analyze specular images. But for more precise measurements an image processing system is indispensable.

Adult↗

PubMed1995

Measurement of visual acuity with two different charts; a comparison of results and repeatability in patients with cataract.

PURPOSE: To compare two different optotypes to measure visual acuity. METHODS: Experiment 1: Fifty patients with moderate cataracts were asked to read a chart consisting of letters of the alphabet (Sloan letters) first and a chart comprising Landolt's broken rings afterwards. Experiment 2: Half of patients were instructed to repeat the reading with a second letter chart, the other half was instructed to read the chart with the broken rings again. RESULTS AND CONCLUSIONS: Experiment 1: It was found that with the letter chart more optotypes (two to four) were recognized than with the broken ring chart. The different result of visual acuity measurement with the two optotypes is irrespective of the visual acuity. Experiment 2: The re-read instruction revealed that the measurements were reproduced equally for both charts.

Cataract↗

PubMed1993

Automated video image morphometry of the corneal endothelium.

The central corneal endothelium of 13 eyes in 13 subjects was visualized with a non-contact specular microscope. This report describes the computer-assisted morphometric analysis of enhanced digitized images, using a direct input by means of a frame grabber. The output consisted of mean cell area, cell density, frequency distribution of the individual cell area, and cell polygonality. Results showed that the mean coefficient of variation of images analyzed three times consecutively was 0.95 percent. The cell analysis of three different images of the same subject was accurate, with a mean coefficient of variation of 4.2 percent.

Adult↗

PubMed1993

Assessment of the long-term corneal response to hydrogel intrastromal lenses implanted in monkey eyes for up to five years.

The biocompatibility of hydrogel intracorneal lenses (ICLs) implanted in monkey eyes was evaluated for periods ranging up to five years. Seventy-three plus or minus powered ICLs made of Lidofilcon A (68% water) or Lidofilcon B (79% water) were implanted following lamellar dissection with a microkeratome. Ten sham surgical procedures were performed without ICL implantation as controls. Eyes were followed for up to five years by slitlamp biomicroscopy and specular microscopy. Light and transmission electron microscopic evaluations of enucleated eyes were performed at various intervals. Minimal tissue reaction was noted; both hydrogel materials appeared to be equally well tolerated. Failures usually occurred as a result of microkeratome problems encountered during surgery. Histopathological changes to the cornea included epithelial thinning anterior to the thickest portion of the ICL, fibroblastic activity along the ICL-stromal interface, and deposition of an amorphous extracellular material adjacent to the ICL. These observations did not appear to be clinically significant as the eyes were quiet by slitlamp examination. Removal of three ICLs eight to ten months prior to enucleation restored the normal histological characteristics of the cornea. The endothelial cell density of ICL-implanted eyes decreased by 4.3% (n = 17) six months after surgery but remained stable thereafter. The variation in endothelial cell area and percentage of hexagonal cells did not change over 50 months. The results appear to demonstrate that high water content synthetic ICLs can be well tolerated in the monkey cornea for up to five years.

Animals↗

PubMed1993

Analysis of corneal aldehyde dehydrogenase patterns in pathologic corneas.

In this study we investigated the properties of corneal aldehyde dehydrogenase (ALDH) in keratoconus corneas using various electrophoretic techniques combined with immunochemical and zymographic identification. Normal corneas and other pathologic corneal buttons obtained during keratoplastic surgery were used as a control. A significant (p < 0.001) lower enzymatic activity was found in keratoconus epithelial extracts (3.1 +/- 2.1 IU/mg protein) compared with normal controls (5.5 +/- 2.6 IU/mg protein), whereas no significant differences were observed in the stromal and endothelial extracts. No significant differences were observed for the corneal ALDH thermolability behavior, nor did any marked changes occur in the position of the 54- and 88-kDa species when comparing the pathologic corneas and normal controls. On the other hand, isoelectric focusing analysis showed a different pattern for the pathologic corneas as compared with controls. Moreover, native-polyacrylamide gel electrophoresis analysis showed that normal corneas exhibit three bands, whereas keratoconus and other pathologic corneas only show two bands. The shift from the three-band pattern to the two-band pattern could be reproduced in vitro using reducing agents, such as glutathione.

Adolescent↗

PubMed1993

Effect of blade configuration, knife action, and intraocular pressure on keratotomy incision depth and shape.

For the same diamond blade extension, uphill (centripetal) radial keratotomy incision direction achieves greater depth and consequently greater refractive effect than downhill (centrifugal) incisions. To determine which factors may account for this difference, two uphill and two downhill incisions were made with a double-edged diamond blade set to 90% central pachometry in 26 human donor eyes at 15 or 60 mm Hg. Uphill incisions made with the perpendicular blade had greater mean incision depth than downhill incisions made with the oblique blade at 15 mm Hg (83.6 +/- 3.9% and 68.2 +/- 5.2%) (p < 0.0005) and at 60 mm Hg (86.3 +/- 3.1% and 79.7 +/- 1.7%) (p < 0.0005). Uphill and downhill incisions both made with the perpendicular blade had equal depth (85.4 +/- 4.9% and 83.7 +/- 3.5%) (p > 0.1). The perpendicular blade edge created a straight, and the oblique edge an S- or J-shaped, histological incision configuration. Corneal profile pictures taken during each incision showed the knife to tilt opposite of the incision direction and to move at a constant angle to the limbal plane, producing a smaller optical clear zone (OCZ) in the posterior stroma than intended with uphill incisions. Greater refractive effect with uphill incisions may be explained by the perpendicular blade being more effective in incising corneal lamellae, and the creation of a smaller posterior OCZ. Intraocular pressure variations during surgery may affect achieved incision depth of downhill, but not of uphill, incisions.

Aged↗

PubMed1992

Clinical comparison of grafts stored in McCarey-Kaufman medium at 4 degrees C and in corneal organ culture at 31 degrees C.

Twenty-eight paired human corneas were preserved in minimal essential medium at 31 degrees C and in McCarey-Kaufman medium at 4 degrees C. These grafts were then transplanted in pairs of patients with keratoconus who were age matched as closely as possible. These pairs received donor corneas from the same donor, so for each pair the donor age and time from death to preservation were the same. Visual acuity, central corneal thickness, and endothelial cell counts were compared. During the 1- to 2-year study period, no statistically significant difference in visual acuity, corneal thickness, or endothelial cell density was found between grafts stored in minimal essential medium and those stored in McCarey-Kaufman medium.

Adolescent↗

PubMed1992

Three versus four radial keratotomy incisions.

Radial keratotomy (RK) is currently performed with four or eight semi-radial incisions. To evaluate the effect of a theoretically more stable three-incision RK pattern, centripetal incisions were made in 16 human donor eyes (eight pairs), using a double-edged diamond blade set to 90% of central pachymetry and a 3.5 mm optical clear zone. Intraocular pressure was maintained at 15 mm Hg during surgery and while keratometry readings were made. One randomly selected eye of each pair had three radial incisions made at 12, 4 and 8 o'clock; the other eye had four radial incisions at 12, 3, 6, and 9 o'clock. Corneal flattening was 6.08 diopters (D) with four incisions and 4.84 D with three incisions (P less than .05). Astigmatism increased 0.44 D and 0.69 D, respectively (P greater than .1). Histologically measured mean incision depth (77.4%) did not differ significantly between the groups (P greater than .1). This study shows that 80% of the effect of a four-incision RK pattern can be obtained with a theoretically more stable three-incision pattern.

Aged↗

PubMed1991

Lens reflectometry with a CCD video camera and computer image analysis.

Lens reflectometry is a useful method of determining the back scatter of light from the cataractous lens. Making use of normal programmes, the personal computer can be used for the quantitative determination of the lens reflex, as seen in the slit-lamp image. If three different images of the same eye are compared, it appears that the mean variation in the back-scatter readings made by our method is 8.3%.

Aged↗

PubMed1991

Clinical evaluation of two non-contact tonometers.

The precision and speed of two non-contact tonometers were examined and compared. The Goldmann applanation tonometer was used as the standard for precision. On the average the results obtained with the non-contact tonometers were not significantly different from those obtained with the Goldmann tonometer. The variation in the values obtained with the non-contact tonometers was greater. The speed of measurement differed between the two non-contact tonometers.

Evaluation Studies as Topic↗