Biomedical subjects
Publications and source records attributed to G van Rij.
Bandage contact lenses can be used following keratoplasty to protect the ocular surface and promote epithelial healing. Rigid gas permeable contact lenses are indicated to correct irregular astigmatism and anisometropia. The Rotterdam Eye Hospital fit 77 keratoplasty patients with contact lenses following their surgery. The methods of fitting contact lenses over the irregular or highly astigmatic surface of a graft are discussed.
In 107 HLA-A- and HLA-B-matched corneal transplantations performed in high-risk patients, the 3-year graft survival was 60.5%. The criteria used for the definition of high risk were vascularization of the recipient cornea and/or one or more previous failed grafts; they were also the indications for HLA typing and matching. Donor/recipient compatibility was defined by the presence of only 0 or 1 HLA-A or HLA-B mismatches. When non-immunological factors leading to graft failure were excluded, the 3-year survival was 76.3%. During that follow-up period, a total of 33 grafts failed; in 13 cases, the cause was allograft rejection. When only first transplants were considered, a 3-year graft survival of 81.0% was observed. Retrospective DR typing was possible in 33 cases. Because only three graft rejections occurred in that group, we were unable to assess the importance of DR compatibility on the survival of corneal allografts.
The refractive predictability of myopic hydrogel intracorneal lenses made of lidofilcon A was evaluated in 24 monkey eyes following a microkeratome dissection. All eyes were examined monthly for refractive alteration and clinical appearance during a follow-up period of 7 to 33 months. The refractive yield was measured by retinoscopy and found to be a function of the implant depth. The mean +/- SD percent of the desired correction achieved averaged 70% +/- 24% at a 36% to 60% depth (n = 8), 54% +/- 22% at a 61% to 79% depth (n = 7), and 12% +/- 14% in implants deeper than at a 79% depth (n = 9). For eyes with implants at a 36% to 60% depth, the predicted vs achieved refractive alteration yielded a correlation coefficient of .97 (88% within +/- 3 diopters of the correlation). The refractive outcome remained stable throughout 7 months of follow-up, whereas deeply placed lenses (greater than or equal to 80%) exhibited significant regression in power during this time.
We retrospectively evaluated 41 corneal wedge resections, performed for the correction of high astigmatism in 40 patients who were spectacle and contact lens intolerant. Keratometric astigmatism decreased from an average of 11.7 diopters (range 5 to 22.5 D) preoperatively to 3.5 diopters (range 0 to 10 D) postoperatively, representing a mean reduction of 8.2 D (range 0 to 16.5), or 70%. The length of follow-up averaged 11 months. Twenty-five, 15 and 9 cases had a follow-up of at least 3, 5 and 10 years, respectively. In 16 cases the keratometry readings remained stable over the years. However, in 1 case of Fuchs' endothelial dystrophy (follow-up 13 years) and 5 cases of keratoconus (follow-up 3, 4, 12, 13 and 14 years) the astigmatism gradually increased during the various follow-up periods. In 3 other cases the astigmatism gradually decreased over the years. Corneal wedge resection is an effective technique for managing high corneal astigmatism. The results remain stable over the years except in some patients with keratoconus.
In 32 patients with long-term contact lens wear (up to 19 years), deep whitish opacities directly adjacent to Descemet's membrane were seen in the central part of the cornea. These opacities were seen in soft hydroxyethylmethacrylate (HEMA) as well as in hard (polymethylmethacrylate, PMMA) contact lens wear. These conditions could reduce visual acuity. When contact lens wear was discontinued or when the HEMA or PMMA lenses were replaced by gas-permeable rigid lenses, the lesions gradually diminished and resolved completely in most patients. One possible cause of these opacities is an allergic reaction to thimerosal. Another possible cause is chronic anoxia of the corneal stroma and endothelium. Endothelial cell density was not abnormal, but there was a marked polymegethism of the endothelium as a sign of endothelial stress.
Corneal astigmatism can be treated optically or surgically. First, we try to manage the astigmatism with glasses or contact-lenses. If it cannot be managed successfully with optical devices, a surgical approach may be indicated. Corneal wedge resections and relaxing incisions can be effective. The wedge resection is the more difficult procedure with reasonably predictable results. In recent years corneal relaxing incision has gained popularity because it is a simple technique with fairly rapid visual rehabilitation. However, the correction result is quite unpredictable. We try to evaluate the factor that created the astigmatism. The steep and flat corneal meridian are identified with keratoscopy, and the correction is performed at the end of the corneal meridian causing the astigmatism. The technique and results are discussed.
Hyperopic hydrogel intracorneal lenses were successfully implanted into 27 of 33 primate eyes. All eyes were evaluated preoperatively and postoperatively at monthly intervals for clinical appearance and refractive alteration. In a preliminary surgical series, several factors, such as tight sutures and implant design, resulted in a poor refractive yield. The final surgical series used a microkeratome with a pediatric microkeratome ring for smooth interface cuts, interrupted suturing with sufficient tension to align the wound without compression, a suture through the lens to prevent its dislocation, and intraoperative keratometry to reduce postoperative cylinder. The predicted vs measured refractive alteration for a range of 6 to 20 diopters had a correlation coefficient of .95. Keratometry changes correlated to the refractive changes with a coefficient of .97 but understand the change in refraction created by the surgery.
A questionnaire was sent round to the 200 members of the Netherlands Intraocular Implant Club (NIOIC), in which they were asked about the policy followed in 1988 with regard to anticoagulant therapy (ACT) and the use of aspirin before and after cataract surgery. Ninety-nine formulas were returned, of which ninety-two were suitable for analysis. It appeared that 62% of the eye surgeons stopped ACT, whereas only 33% stopped the use of aspirin. After stopping ACT nine, in some cases serious, systemic complications arose. The continuation of ACT led to 3 ocular complications. It would appear that continuation of ACT and the use of aspirin is to be recommended.
We report on 29 consecutive patients with pseudophakic bullous keratopathy who underwent in one eye penetrating keratoplasty with an exchange of the original intraocular lens for a Pearce tripod posterior chamber lens, and who were available for a follow up of at least 12 months. The average interval between cataract extraction with lens implantation and the appearance of bullous keratopathy was five and a half years (range 10 months to 16 years). The mean follow-up period after penetrating keratoplasty was 36 months (range 12 to 56 months). The corneal graft remained clear in 22 (76%) eyes. One year after the operation 45% of the eyes had a vision of 20/40 or better, and 20% had visual acuities between 20/40 and 20/100. The remaining 31% had a vision of 20/100 or less (one unknown). Nine eyes (31%) had cystoid macular oedema or macular degeneration. 45% of the eyes had a refraction within approximately 2 dioptres of emmetropia. In patients with pseudophakic corneal oedema we continue to exchange the intraocular lens by a Pearce tripod posterior chamber lens sutured to the iris when it is necessary to remove the lens.
Keratometry, retinoscopy, horizontal diameter, and pachymetry were measured in adult and infant rhesus monkeys (Macaca mulatta). The adult monkeys had a mean corneal thickness of 0.47 +/- 0.03 mm (+/- standard deviation), corneal diameters of 10.6 +/- 0.5 mm, keratometry values of 51.90 +/- 1.61 diopters, and subjective refractions of 0.48 +/- 2.36 diopters. Female adult monkeys had smaller corneal diameters by 0.06 mm (P = .02) and steeper corneas by 0.77 diopters (P = .04). Infant female monkeys also had steeper corneas by 2.37 diopters (P = .05). No significant differences were found between right and left eyes in either adult or infant monkeys.
In this laboratory study, we used five different corneal trephines on 60 fresh human donor eyes with controlled intraocular pressure to study the variation in the size and shape of the trephine openings. With all trephines, the average diameter of the button was larger than the diameter of the trephine at the epithelial side (mean difference, 0.21 mm; range, 0.06 to 0.35 mm) and the endothelial side (mean difference, 0.42 mm; range, 0.13 to 0.79 mm), presumably because the corneal tissue protruded into the trephine during cutting. The trephines that produced the most uniform opening were a nondisposable suction trephine and a freestanding disposable blade, but they caused some undercutting.
We performed 32 hydrogel keratophakia procedures in rhesus monkey corneas. Surgery was technically successful in 20 eyes. Toxic stromal keratitis occurred in five eyes because of impurities on the lenticules. Fibrosis appeared around the implant in five eyes. Two eyes showed aseptic necrosis of the inferior cornea with extrusion of the implant, attributed to exposure keratitis. Complications during surgery included faulty microkeratome incisions (three eyes) and epithelial implantation in the lamellar bed (one eye). Three lenticules decentered, one extruding through the wound, probably because the monkeys rubbed their eyes excessively. Nine of the 11 eyes with postoperative refraction data showed overcorrection or undercorrection of more than 1.00 diopter. Most of these complications could have been prevented by better technique, design, and manufacture of the lenticule or cooperation of the subjects.
We used the pig eye as an experimental model. The corneas of 51 whole eyes were trephined in a laboratory setting, using three different techniques to compare the variations in the trephine openings. Since it is difficult to assess the diameter of the hole created by trephination, we measured both the epithelial and endothelial diameters, as well as the angle between the epithelial surface and the cut of the excised corneal button, since these dimensions reflect the true shape of the hole. Trephination with either a free-standing trephine blade without a handle or with a motor-driven instrument gave the same results. However, our findings showed that the results obtained using a trephine in a holder--as is commonly used in clinical practice--were statistically significantly inferior.
Radial interrupted nylon sutures were placed in the corneas of fourteen human donor eyes, in a laboratory setting, to produce a reversible surgical correction of myopia. Significant corneal flattening was achieved when a small optical zone (4-5 mm) was left free but not with a larger optical zone. It may be possible that radial sutures have a permanent flattening effect when the sutures are left in place and keep their tensile strength.
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Patients with raised intraocular pressure often have lower tension during hospital admissions than on out-patient measurement, even though the therapy is the same. A prospective study on 18 volunteers and 10 glaucoma patients was set up to find out whether oxybuprocaine eyedrops or repeated applanation tonometry could have anything to do with this. The tension was measured at least 3 times a day with the non-contact tonometer (NCT). In the case of the volunteers oxybuprocaine was instilled into the eye 3 times a day for one week. In the case of the patients the tension in one eye was measured with the Goldmann tonometer on several days after the application of oxybuprocaine drops. No reduction in intraocular pressure was found during the observation period, nor was there an obvious difference between the test eyes and the control eyes. In hospital, patients had at 11 o'clock in the morning intraocular pressure which was on the average 2.2 +/- 1.5 mmHg lower than that measured at out-patient checks, in spite of receiving the same therapy.
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High water content hydrogels can be made with water and solute permeabilities comparable to those of the corneal stroma, thus making them feasible as intrastromal implants for refractive keratoplasty. The materials have been shown to be compatible with the cornea tissue, but for a lenticule of hydrogel to be effective in a refractive keratoplasty procedure it must alter the anterior curvature of the cornea. In this investigation hydrogel lenticules were implanted by a free-hand pocket dissection in eight Macaca mulatta (rhesus) and two Macaca nemestrina (pigtail) primate eyes. The results of pre- and postoperative keratometry and subjective retinoscopy as well as biomicroscopy were recorded. The alteration in refractive power was calculated in relation to the hydrogel lenticule parameters such as base curve, refractive index, etc. The corneal refractive change had a yield of +3 +/- 27% (+/- SD). The central keratometric change had a yield of +6 +/- 16%. The hydrogel plus power lenticule implanted in a free-hand intrastromal pocket created no significant steepening of the anterior cornea surface and therefore little change in refraction.