Intraocular lens exchange on day one after surgery.
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Aged↗
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Results for “Hyperopia”
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Results in patients with high and low power intraocular lenses.
Seventy patients who received lens implants of unusually high or low power were studied retrospectively. There were 36 myopes and 34 hyperopes. All were followed a minimum of two years. Although both groups of patients presented technical problems at surgery, the visual acuity and general results were good.
Humans↗
Polysulfone corneal lenses.
Polysulfone is a thermoplastic compound first synthesized in 1965. A unique characteristic of polysulfone is its high refractive index (1.633), which allows very thin optical lenses to be manufactured. Over the last five years, D. Peter Choyce has surgically implanted over 40 polysulfone lenses into eyes of his patients. Analysis of his data indicates that polysulfone intraocular lenses are capable of correcting large refractive errors. Based on his work, a multicenter study was undertaken to evaluate the safety and efficacy of polysulfone as an intracorneal lens material in laboratory models. Four monkeys, eight baboons, and 24 cats were used as laboratory models; 5.0-mm to 6.0-mm diameter hyperopic (+28.5 diopter) and myopic (-17.0 and -25.5 diopter) lenses were surgically implanted within the corneal stroma in one eye of each of the laboratory models while a sham lamellar dissection was performed in the other eye. One hundred percent (4/4) of monkey eyes, 12.5% (1/8) of baboon eyes, and 70.0% (18/24) of cat eyes maintained clear media by ophthalmoscopic examination at follow-ups ranging from three to six months. Complications included both visually and nonvisually significant interface opacities, lens extrusion, anterior corneal necrosis, refractile particles, and epithelial thinning.
Animals↗
Experience with hexagonal keratotomy.
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Cornea↗
Investigation of unwanted images caused by intraocular lenses.
A widely circulated paper by IOLAB Corporation describing unwanted images inadvertently presented various images that could not exist with a centered intraocular lens as was claimed in the study. I repeated the IOLAB experiments and found that artifacts within the Gullstrand eye model, which was used in the IOLAB study, were the cause of these images. I also found that a myopic eye will see a collimated light or point source as a mottled cluster of bright spots which can be simulated, in an eye model, by a faceted corneal lens. From this observation, I learned that people can see their own cataracts when looking at a distant light.
Adolescent↗
Effectiveness of intraocular lens calculation in high ametropia.
The error in prediction of emmetropic intraocular lens power or postoperative refractive error after lens implantation was analyzed in three groups of eyes after posterior chamber lens implantation. Regression line calculation with the SRK equation or with a group-specific regression was compared with theoretical calculations in unselected, long myopic and short hyperopic eyes. The cut-off length was below 22.0 mm for the short eyes and above 25.9 mm for the long eyes. In the unselected and hyperopic group, there was only a small difference in mean error and error variance when the three calculation methods were compared. In the high myopic group, the range of error increased in all methods. The worst results were obtained with the standard SRK equation because the slope of the regression line in myopic eyes differs from the classical regression line calculated on an average population of implants. Lens calculation in high myopic eyes should therefore be performed with a specific regression line or by theoretical calculation.
Humans↗
Evolution of excimer laser corneal surgery.
Interest in the potential of the excimer laser for refractive surgery was generated by a series of experiments performed in IBM's T.J. Watson laboratories. The development of photoablative decomposition was applied to corneas with immediate implication for corneal refractive control. Scientific investigations demonstrated that submicron erosion ablation of material was possible without damage to remaining tissues. After refinement of the beam and analysis of thresholds, we subsequently demonstrated that healing of large ablated areas in rabbits and then primate eyes would occur without scar formation or loss of transparency. This prompted a number of commercial efforts to develop this device for both refractive and general corneal surgical applications. The early clinical investigations show that a predictable refractive change could be induced in a cornea and this change was stable over many months. Furthermore, the transparency of the cornea was unimpaired. These favorable early results have led to a number of clinical investigations of excimer laser corneal surgery including refractive keratectomy, a direct laser keratomileusis.
Animals↗
Hyperopic shift after refractive keratotomy using the Casebeer System.
PURPOSE: To determine the degree of hyperopic shift following refractive keratotomy. SETTING: The Werblin Center, Princeton, West Virginia. METHODS: The results of 241 consecutive radial/astigmatic keratotomy procedures in 128 patients were studied. All procedures were performed using Casebeer nomograms. Refractive follow-up information was obtained for 78% of patients at 3 months (range 1 to 6 months), 1 year (range 6 to 21 months), and 3 years (range 30 to 44 months). RESULTS: Overall, the amount of hyperopic change decreased significantly (P < .05) during the 3 year period, from + 0.34 diopters (D) per year to + 0.12 D per year. Eyes with more than 6.0 D of preoperative intended correction were more unstable (+ 0.49 D in the first year and + 0.44 D in the second and third years) than eyes with less than 5.0 D (+ 0.27 D and + 0.05, respectively). CONCLUSION: Because the average magnitude of the hyperopic shift was + 0.6 D in the first 3 years after surgery, a slight undercorrection, -0.5 D to -0.7 D, should be the refractive endpoint for primary and enhanced refractive keratotomy surgery.
Follow-Up Studies↗
Modified intraocular lens power formula in polypseudophakia.
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Adult↗
Preventing overcorrection and microperforations with RK.
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Cornea↗
Excimer laser correction of high astigmatism after keratoplasty.
PURPOSE: To assess the effectiveness of excimer laser correction of high astigmatism after keratoplasty. SETTING: Kiel University Eye Hospital, Kiel, Germany. METHODS: In a prospective study, we treated high astigmatism in 16 patients using a 193 nm excimer laser with a rotating mask system to make a toric ablation. Thirteen patients had postkeratoplasty astigmatism, 3, idiopathic natural astigmatism. Preoperative refractive cylinder ranged from 3.0 to 9.0 diopters (D). Minimum follow-up was 6 months. RESULTS: Mean uncorrected visual acuity increased by 3.3 lines in 13 patients. Best corrected visual acuity decreased by no more than two lines in 6 patients and improved by at least one line in 6 patients. Mean cylindrical reduction was 2.8 D. Haze was classified from 0.5 to 2.0. CONCLUSIONS: In this study, the excimer laser technique effectively reduced high corneal astigmatism. The main problems incurred were development of a hyperopic shift and, in some patients, an uncertain refractive outcome. Reasons for inadequate correction of postkeratoplasty astigmatism included a slightly decentered mask and irregular astigmatism from the circular scar.
Adolescent↗
Predicted and actual refraction after intraocular lens implantation in eyes with silicone oil.
OBJECTIVE: To determine the difference between the predicted and postoperative refraction in eyes with silicone oil that had extracapsular cataract extraction (ECCE), and intraocular lens (IOL) implantation. SETTING: Ophthalmology department providing primary, secondary, and tertiary care in central Israel. METHODS: Eight patients with silicone-oil-filled eyes following vitreoretinal procedures had ECCE and IOL implantation. The IOL power calculation was performed with the modified SRK II, the SRK/T, and the Holladay emmetropia/ametropia formulas, using the axial length of the eye, measured prior to the silicone oil injection, and the keratometric readings. The predicted and postoperative refractions were compared. RESULTS: The postoperative refraction was more hyperopic than predicted by an average of 4.08 diopters (D) for the SRK II formula, 3.91 D for the SRK/T formula, and 4.01 D for the Holladay emmetropia/ametropia formula. Removing the silicone oil from two eyes several months after cataract extraction reduced the deviation from the predicted refraction to 0.25 and 0.80 D. CONCLUSION: The presence of silicone oil in the vitreous space induces a hyperopic shift in eyes having ECCE and IOL implantation. This hyperopic shift should be considered when calculating the IOL power if a long-term tamponade with the oil is planned. If the silicone oil is to be removed shortly after the cataract extraction, the IOL power should be calculated solely from the formula.
Adult↗
Treatment of hyperopic astigmatism.
PURPOSE: To analyze the results after laser-assisted in situ keratomileusis (LASIK) treatment for positive cylinder at the flattest meridian. SETTING: Instituto de la Visión, Buenos Aires, Argentina. METHODS: A prospective, nonrandomized study was conducted. Patients were divided into three groups: (1) simple hyperopic astigmatism (SHA); 15 eyes with a mean preoperative cylinder of +3.37 diopters (D) +/- 1.62 (SD); compound hyperopic astigmatism (CHA); 75 eyes with a mean preoperative cylinder of +3.34 +/- 1.39 D; (3) mixed astigmatism (MA); 73 eyes with a mean preoperative cylinder of +3.45 +/- 2.15 D. In all eyes, treatment of the cylinder was performed at the flattest meridian by LASIK using the Chiron-Technolas Keracor 116/117 laser. The following parameters were analyzed over time: uncorrected visual acuity; best corrected visual acuity; correction of the spherical equivalent and the cylinder; lines of visual acuity gained and lost. RESULTS: Six months after the procedure, refractive cylinder was reduced to +0.58 +/- 1.22 D in the SHA group, +0.12 +/- 1.23 D in the CHA group, and -0.11 +/- 1.28 D in the MA group. Uncorrected visual acuities were 20/20 or 20/25 in 66.7, 60.4, and 76.5% of the groups, respectively. CONCLUSIONS: Use of the LASIK technique with the Keracor laser to treat positive cylinder at the flattest meridian corrected simple and compound hyperopic astigmatism and mixed astigmatism with good predictability and safety. This treatment has not produced a hyperopic refractive change at the opposite meridian.
Adult↗
Diode laser thermokeratoplasty: application strategy and dosimetry.
PURPOSE: To investigate suitable application parameters for efficient hyperopic correction by laser thermokeratoplasty (LTK) using mid-infrared laser diodes. SETTING: Medical Laser Center Lübeck, Lübeck, Germany. METHOD: A tunable continuous-wave laser diode in the spectral range between 1.845 and 1.871 microns was used. Transmitted by waveguides, the laser energy was used to induce coagulations on freshly enucleated porcine eyes to increase corneal curvature. The coagulations were equidistantly applied by a fiber-cornea contact and a noncontact focusing device that were adjusted on a ring concentric to the corneal apex. Different laser parameters and application geometries were evaluated. Refractive changes were measured by computer-assisted corneal topography before and after treatment. Polarization light microscopy and temperature calculations were used to analyze the coagulations. RESULTS: Because of the tunability of the laser diode, the influence of the corneal absorption coefficient (between 0.9 and 1.6 mm-1) on the refractive change could be measured. A laser power between 125 and 200 mW was adequate to achieve refractive changes up to 10.0 diopters. In the preferable focusing device, the refractive change increased almost logarithmically with the irradiation time up to 15 seconds. The number of coagulations on a fixed application ring showed no significant influence on refractive change; however, it showed an almost linear decrease with increasing ring diameter from 5.0 to 10.0 mm. Histological analysis revealed 3 stages of thermal damage. CONCLUSION: Diode LTK provided defined and uniform coagulations when using a well-adapted focusing device, resulting in sufficient refractive change. The results indicate that diode LTK is superior to pulsed holmium LTK.
Absorption↗
Intraocular pressure measurement following hyperopic LASIK.
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Adult↗
Pseudo-Fleischer ring after hyperopic laser in situ keratomileusis.
A 37-year-old woman had bilateral hyperopic laser in situ keratomileusis (LASIK). Six months postoperatively, an epithelial pigmentation ring pattern was identified on both corneas. The appearance of the ring pattern was similar to the iron deposits of the Fleischer ring of keratoconus. While corneal iron deposits in various patterns have been reported after other forms of ocular therapeutic and refractive surgery, this is the first report of the association between hyperopic LASIK and a corneal iron line, which we have called the "pseudo-Fleischer ring."
Adult↗
Contact zone of piggyback acrylic intraocular lenses.
In a hyperopic cataract patient, surgery was performed with implantation of 2 foldable, acrylic, posterior chamber intraocular lenses (IOLs) in the bag. The IOLs showed a central contact zone during surgery. This contact zone remained after surgery and was documented 2 months postoperatively. The contact zone may induce multifocality similar to that seen with multifocal IOLs.
Acrylic Resins↗