To evaluate the long-term corneal endothelial cell density (ECD) and outcomes after iris-fixated aphakic intraocular lens (IOL) implantation in children after bilateral congenital or juvenile ...cataract extraction and to compare the outcomes with data in the literature.
Academic Medical Centre, Amsterdam, The Netherlands.
Case series.
This retrospective study evaluated the charts and endothelial photographs of children who had Artisan aphakic IOL implantation. The main outcome measure was the ECD at the last follow-up visit.
The mean age of the 10 patients (20 eyes) at IOL implantation was 7.4 years (range 4.3 to 11.1 years) and at the last follow-up, 19.6 years (range 14.3 to 26.6 years). After a mean follow-up of 12.3 years (range 10.0 to 15.6 years), the mean ECD was 2702 cells/mm(2) (range 1382 to 3974 cells/mm(2)). Although this is comparable to the mean normal endothelial cell counts in this age group reported in the literature, a wider range of ECD was found in the current study.
The mean corneal ECD after more then 10 years of follow-up was comparable to the mean normal ECD for this age group reported in the literature. The high standard deviation of the mean ECD in the current study highlights the importance of prospective studies on the ECD after iris-fixated aphakic IOL implantation in young patients.
We report 2 patients who had radial keratotomy (RK) to correct myopia. The first patient developed a postoperative hyperopic shift and cataract. Nine years post RK, she had intracapsular cataract ...extraction and implantation of an Artisan aphakic intraocular lens (IOL). Twenty years post RK, hyperopia and astigmatism progressed to +7.0 -5.75 x 100 with a best corrected visual acuity (BCVA) of 20/20. Due to contact lens intolerance, the Artisan aphakic IOL was exchanged for an Artisan toric aphakic IOL. Three months later, the BCVA was 20/20 with +1.0 -0.50 x 130. The second patient demonstrated residual myopic astigmatism 6 years after bilateral RK and had become contact-lens intolerant. An Artisan toric phakic IOL was implanted in both eyes. Four months later, the BCVA was 20/25 with a refraction of +0.25 -1.0 x 135 and 20/20 with a refraction of -1.0 x 40. Both patients were satisfied with the visual outcomes.
We present two patients with Marfan syndrome and bilateral crystalline lens dislocation who underwent bilateral lens extraction and Artisan aphakia intraocular lens (IOL) implantation. With ...a follow-up of more than 12 years, we found a good visual outcome, no serious IOL-related complications, and endothelial cell densities within the expected range for eyes without cataract surgery.
Starting from the Smoothed Particle Hydrodynamics method (SPH), we propose an alternative way to solve flow problems at a very low Reynolds number. The method is based on an explicit drop out of the ...inertial terms in the normal SPH equations, and solves the coupled system to find the velocities of the particles using the conjugate gradient method. The method will be called NSPH which refers to the non-inertial character of the equations. Whereas the time-step in standard SPH formulations for low Reynolds numbers is linearly restricted by the inverse of the viscosity and quadratically by the particle resolution, the stability of the NSPH solution benefits from a higher viscosity and is independent of the particle resolution. Since this method allows for a much higher time-step, it solves creeping flow problems with a high resolution and a long timescale up to three orders of magnitude faster than SPH. In this paper, we compare the accuracy and capabilities of the new NSPH method to canonical SPH solutions considering a number of standard problems in fluid dynamics. In addition, we show that NSPH is capable of modeling more complex physical phenomena such as the motion of a red blood cell in plasma.
The excitation function and momentum distribution of η′ mesons have been measured in photon induced reactions on 12C in the energy range of 1250–2600 MeV. The experiment was performed with tagged ...photon beams from the ELSA electron accelerator using the Crystal Barrel and TAPS detectors. The data are compared to model calculations to extract information on the sign and magnitude of the real part of the η′-nucleus potential. Within the model, the comparison indicates an attractive potential of −(37±10(stat)±10(syst)) MeV depth at normal nuclear matter density. Since the modulus of this depth is larger than the modulus of the imaginary part of the η′-nucleus potential of −(10±2.5) MeV, determined by transparency ratio measurements, a search for resolved η′-bound states appears promising.
To describe the refractive results of cataract surgery after photorefractive keratectomy (PRK) for patients with myopia, and to find a more accurate method to predict intraocular lens (IOL) power in ...these cases.
Nonrandomized, retrospective clinical study.
Nine patients (15 eyes) who underwent cataract surgery after prior PRK to correct myopia were identified. The medical records of both the laser and cataract surgery centers were reviewed.
Eight different keratometric values (K values; measured or calculated) were entered into 3 different IOL calculation formulas: SRK/T, Holladay 1, and Hoffer Q. The actual biometry and IOL parameters were used to predict postoperative refraction, which was compared with the actual refractive outcome. Also, the relative underestimation of the refractive change in corneal dioptric power by keratometry after PRK was calculated.
In 7 of 15 eyes, IOL exchange or piggybacking was performed because of hyperopia. Retrospectively, the most accurate K value for IOL calculation was found to be the pre-PRK K value corrected by the spectacle plane change in refraction. Use of the Hoffer Q formula would have avoided postoperative hyperopia in more cases than the other formulas. The mean underestimation of the change in corneal power after PRK varied from 42% to 74%, depending on the method of calculation.
The predictability of IOL calculation for cataract surgery after PRK can be improved by using a corrected, refraction-derived K value instead of the measured, preoperative K value.
Low gas-permeable contact lens wear of polymethyl methacrylate or hydroxyethyl methacrylate material is known to cause morphologic abnormalities in the corneal endothelial cell layer. These lenses ...were widely prescribed and successfully worn until their use was actively discouraged in the late 1980s and early 1990s. This study was designed to investigate whether discontinuation of low gas-permeable contact lens wear leads to an improvement of corneal endothelial cell morphology.
At the time of discontinuation and at least 5 years after discontinuation of low gas-permeable contact lens wear, noncontact specular photographs of the central corneal endothelium were made in 66 patients (14 male and 52 female, mean age 37.7 +/- 8.4, range 24.6-69.0). By computer analysis of endothelial photographs, parameters for polymegethism and pleomorphism were calculated, as well as cell density.
Mean follow-up time between photographs was 6.8 years (SD 1.1). Sixty-one patients were refitted with rigid high gas-permeable contact lenses or high-water-content soft lenses, and 5 patients switched to spectacle wear. A small but significant recovery of the corneal endothelial cell morphology was found for the mean coefficient of variation of cell area, from 37.5 to 35.7 (P = 0.022), and for the coefficient of variation of the number of sides, from 13.1 to 12.4 (P = 0.004). The mean percentage of hexagonal cells increased from 54.2 to 56.2 (P = 0.013). Although the corneal endothelial cell morphology improved significantly on cessation of LGP contact lens wear, the values did not return to levels observed in normal, non-contact lens wearing individuals. During follow-up, the mean endothelial cell density decreased significantly (P = 0.001) from 2994 to 2890 (a 3.5% cell loss in 6.8 years), which is similar to the known normal age-related cell loss of 0.6% per year in non-contact lens wearing healthy individuals.
Endothelial polymegethism and pleomorphism caused by PMMA or HEMA contact lens wear is partly reversible.
To introduce a new model describing human in vivo corneal deswelling after hypoxic contact lens wear, based on a damped harmonic oscillator, which can describe an overshoot in corneal deswelling, to ...compare this new model with the currently used exponential model, and also to test whether a diurnal variation in baseline corneal thickness exists that would have to be taken into consideration when calculating corneal deswelling curves.
In nine healthy young adults, corneal thickness was measured every 30 minutes for 11.5 hours on average using modified optical pachometry (natural test). On another day, corneal deswelling was monitored for 11.1 hours on average after 2 hours of hypoxic contact lens wear (stress test). The damped harmonic oscillator model and the exponential model were used to calculate best-fitting deswelling curves. Natural test data were analyzed for the presence of a trend. Goodness of fit of the curves to the experimental data was analyzed using the F test.
In 82% of the deswelling curves the new damped harmonic oscillator model provided a better fit to the data than the exponential model (P < 0.05). An average overshoot in corneal thickness recovery of 5 microm (range, 0-11 microm) was found. In 50% of the natural tests significant trends were found, without any consistent similarities. The overshoot could not be explained by these trends.
The new damped harmonic oscillator model describes corneal deswelling after hypoxic contact lens wear more accurately than the exponential model. No consistent diurnal variation could be demonstrated.
To identify risk factors for rebubbling, and early graft failure after Descemet membrane endothelial keratoplasty (DMEK).
In this prospective registry study, all consecutive DMEK procedures ...registered in the Netherlands Organ Transplant Registry were assessed (n=752). Univariable and multivariable analysis was performed using logistic regression. The effect of rebubbling on endothelial cell density was analysed using a linear mixed model.
144 of 752 (19%) eyes underwent rebubbling. Rebubbling was successful in 101 eyes (70%). In eyes that underwent rebubbling, the graft failure rate was significantly higher than eyes that did not undergo rebubbling (30% vs 9%, respectively; OR: 4.28, 95% CI 2.72 to 6.73, p<0.001). In multivariable analysis, independent risk factors for rebubbling were surgical complication (OR: 2.28, 95% CI 1.20 to 4.33, p=0.012) and older recipient age (OR: 1.04 (per increase of 1 year), 95% CI 1.01 to 1.07, p=0.003). Risk factors for developing graft failure within 3 months were transplant before 2016 (OR: 3.32, 95% CI 1.87 to 5.90, p<0.001), and surgical complication (OR: 2.93, 95% CI 1.42 to 6.04, p=0.004). Throughout the study period, rebubbling and early graft failure were inversely related. Eyes that underwent rebubbling showed significantly lower endothelial cell densities at 3, 6 and 12 months compared with eyes that did not undergo rebubbling (all p<0.001).
This Dutch registry study identified independent risk factors for DMEK graft detachment leading to rebubbling, namely recipient age and surgical complication, and early graft failure, namely transplantation before 2016 and surgical complication. Rebubbling was associated with significantly higher endothelial cell loss in the first year after surgery.
To examine whether corneal hydration control is impaired in corneas with endothelial morphologic changes (increased variation in cell size and cell angularity) due to long-term low gas-permeable ...contact lens wear.
Twenty-one long-term wearers of low gas-permeable contact lenses (mean age, 41 years +/- 8 SD) and 18 age-matched controls (mean age, 42 years +/- 8 SD) were studied. To assess endothelial morphology, endothelial photographs were taken, enlarged 400X, scanned into a computer, and evaluated. Hydration control was assessed by a corneal stress test. Corneal swelling was induced by applying low gas-permeable soft contact lenses for 2 hours during eye closure. After the lenses were removed, the rate of deswelling was determined using optic pachometry.
Morphologic analysis of the endothelial photographs showed a significant increase of polymegethism (P < 0.01) and pleomorphism (P < 0.01) in the group wearing contact lenses compared with the control group. The percentage of recovery of corneal thickness per hour (PRPH) from induced swelling proved to be significantly lower (P = 0.03) and the induced swelling proved to be significantly lower (P < 0.01) in the group wearing contact lenses than in the control group. Multiple regression analysis showed that the PRPH decreased as the morphologic alterations increased. However, this trend appeared not to be significant at the 5% level. A significant relationship was found between morphologic parameters and induced swelling, indicating that induced swelling decreased as the morphologic alterations increased.
The results of this study indicate that increased endothelial polymegethism and pleomorphism may be accompanied by a decreased corneal hydration control in people who wear contact lenses.
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