Importance of reporting the complications of refractive surgery.
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Cornea↗
Biomedical subjects
T Kohnen
Publications and source records attributed to T Kohnen.
Intraocular recombinant tissue-plasminogen activator fibrinolysis of fibrin formation after cataract surgery in children.
PURPOSE: To evaluate the efficacy and safety of intracameral recombinant tissue plasminogen activator (rt-PA) application for fibrinolysis of fibrin formation after cataract surgery in children. SETTING: Johann Wolfgang Goethe-University, Department of Ophthalmology, Frankfurt am Main, Germany. METHODS: This study comprised 11 eyes of 10 patients aged 3 to 13 years (mean 7.2 +/- 3.68 [SD]) who developed severe fibrin formation after cataract surgery and IOL implantation despite intensive topical steroid therapy. Under general anesthesia, fibrinolysis was performed with 10 micrograms of rt-PA 7.18 +/- 2.04 days after intraocular surgery. Follow-up included slitlamp examination, tonometry, visual acuity testing, and-ophthalmoscopy. Anterior chamber flare measurements could be performed in 6 eyes. RESULTS: Complete resolution of fibrin formations occurred in 90% of the patients in these cases, no recurrent fibrinous reaction or adverse effects were noted. In 2 eyes of the same patient with a history of juvenile rheumatoid arthritis and chronic uveitis, fibrin clot dissolution was incomplete. A recurrent fibrinous formation could be observed after 2 and 4 weeks, respectively. A beginning band keratopathy excluding the central and limbal cornea was noted after 6 and 8 weeks, respectively. CONCLUSION: Intraocular application of rt-PA appears to be a safe and efficacious therapeutic approach in the management of severe fibrinous reactions after pediatric cataract surgery.
Adolescent↗
Experimental and clinical evaluation of incision size and shape following forceps and injector implantation of a three-piece high-refractive-index silicone intraocular lens.
BACKGROUND: Previous studies have demonstrated that incision sizes required for insertion of various foldable intraocular lenses (IOLs) vary according to the IOL/inserter combination. The purpose of this study was to compare incision sizes and wound shape for both forceps and injector implantation of high-refractive-index silicone IOLs. METHODS: In fresh human cadaver eyes, limbal corneal tunnel incisions were created, and 12 foldable high-refractive-index silicone (dimethyldiphenylsiloxane) IOLs were inserted in a randomized fashion using either a forceps or an injector. Using incision calipers, internal and external measurements of the tunnel incisions were obtained before and after IOL insertion. Scanning electron microscopy (SEM) was performed on selected corneas following IOL insertion. Additionally, in 12 cataract procedures, the incision sizes following forceps or injector implantation were evaluated intraoperatively. RESULTS: In the experimental setting, the external and internal tunnel widths (in mm) before insertion were 3.05 mm (+/-0.07) and 3.02 mm (+/-0.03), respectively, with the forceps and 3.06 mm (+/-0.04) and 3.01 mm (+/-0.04) with the injector. Following IOL implantation, the external and internal incision sizes were 3.33 mm (+/-0.07) and 3.33 mm (+/-0.04) with the forceps and 3.32 mm (+/-0.08) and 3.33 mm (+/-0.07) with the injector. SEM showed tearing of corneal structures after implantation through the smallest possible incisions with both devices. In the clinical study, the incision sizes before and after implantation were 3.23 mm (+/-0.10) and 3.36 mm (+/-0.06) with the forceps and 3.11 mm (+/-0.08) and 3.21 mm (+/-0.10) with the injector. CONCLUSIONS: This study confirms that high-refractive-index silicone IOLs provide one of the smallest currently achievable incisions before and after IOL implantation. In clinical use, the new injector reduces the mean incision size required by approximately 0.1 mm.
Aged↗
Complications and complication management with foldable intraocular intraocular lenses.
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Humans↗
Axial, instantaneous, and refractive formulas in computerized videokeratography of normal corneas.
PURPOSE: To compare the values for corneal power determined by the axial, instantaneous and refractive formulas when imaging normal human corneas using computerized videokeratography. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. METHODS: This prospective clinical trial involved 60 corneas of 30 normal volunteers. Computerized videokeratography was performed to determine corneal power at the center and the 1, 3, 5, and 7 mm zones using the 3 formulas. RESULTS: Mean central corneal power was 42.86 diopters (D) with each of the formulas. The mean corneal powers for the axial, instantaneous, and refractive formulas were 43.09, 43.21, and 42.98 D at the 1 mm zone; 43.10, 42.92, and 43.46 D at the 3 mm zone; 42.75, 41.63, and 44.02 at the 5 mm zone; 42.21, 40.30, and 44.79 D at the 7 mm zone, respectively. The differences among powers for the 3 formulas at the 3, 5, and 7 mm zones were statistically significant (P < .01). CONCLUSION: In normal corneas, clinically significant differences exist in the corneal power values calculated by the axial, instantaneous, and refractive formulas.
Adolescent↗
Advances in the surgical correction of hyperopia.
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Cornea↗
Radial and staggered treatment patterns to correct hyperopia using noncontact holmium:YAG laser thermal keratoplasty.
PURPOSE: To compare the effects of two treatment patterns in the correction of hyperopia by noncontact holmium:YAG laser thermal keratoplasty (LTK). SETTING: Divisione Oculistica, Ospedale S. Gerardo, Monza, Italy. METHODS: Using two treatment patterns, we performed noncontact LTK in one session in 16 eyes of 8 patients with isometropic hyperopic refractive errors; mean preoperative subjective cycloplegic refraction was +4.90 diopters (D) +/- 1.17 (SD). The treatment consisted of 24 spots in three concentric rings of eight spots each; ring diameters were 6.0, 7.0, and 8.0 mm, respectively. Each spot received seven pulses of laser energy at 30 mJ/pulse. We treated one eye of each patient with a radial pattern (the spots of the three rings aligned on the eight semimeridians) and the fellow eye with a staggered pattern (the spots of the contiguous rings at 22.5 degrees from each other). Follow-up at 1, 15, 30, 90, 180, and 360 days included subjective cycloplegic refraction, uncorrected (UCVA) and spectacle-corrected visual acuity (SCVA), computerized videokeratography (CVK), and Scheimpflug camera examination. RESULTS: One year postoperatively, the mean subjective cycloplegic refraction was +2.75 +/- 1.6 D in the eyes treated with the radial pattern and +3.40 +/- 1.6 D in those treated with the staggered pattern; the mean change in subjective cycloplegic refraction was 2.15 and 1.50 D, respectively. Mean UCVA improved by five lines in the radial group and by four lines in the staggered group. Mean SCVA returned to preoperative levels by day 15 in the radial group and at 1 year in the staggered group; at 1 year, SCVA improved by one line in the radial group and remained unchanged in the staggered group. No eye lost one or more lines of SCVA. Refractive astigmatism was essentially unchanged in both groups. Scheimpflug photography and CVK indicated larger and more uniform corrected zones in the radial group. CONCLUSIONS: Radial and staggered patterns effectively corrected low hyperopia, although both were subject to a certain amount of regression. The radial pattern produced faster postoperative recovery of SCVA and demonstrated greater refractive stability.
Adult↗
Effect of heparin in irrigating solution on inflammation following small incision cataract surgery.
PURPOSE: To study the effect of heparin-sodium added to the irrigating solution on postoperative inflammation in patients having cataract surgery. SETTING: Department of Ophthalmology, University of Giessen, Giessen, Germany. METHODS: Seventy-two patients having phacoemulsification with posterior chamber intraocular lens (IOL) implantation were randomly assigned to receive regular irrigating solution or solution with heparin-sodium (final diluted concentration 10 IU/mL). In half the patients, poly(methyl methacrylate) (PMMA) IOLs were implanted and in half, foldable silicone IOLs. The patients were examined preoperatively, on days 1 and 3, and 1 year postoperatively. Postoperative inflammation was objectively evaluated by measurement of flare and cells using laser flare-cell photometry. RESULTS: The mean postoperative flare values were significantly lower in the groups with additional heparin-sodium at days 1 and 3 (P < . 01). Flare values were not significantly different 1 year postoperatively. Cell values for the heparin-treated groups were lower, but the difference did not reach statistical significance. Flare and cells values for the two IOL materials were not significantly different during the entire follow-up. CONCLUSION: Heparin-sodium added to the infusion solution during small incision cataract surgery reduced inflammation in the early postoperative period.
Aged↗
Format for reporting refractive surgical data.
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Data Collection↗
Refractive aspects of cataract surgery.
The refractive aspects of cataract or lens surgery has formed a new field of operations. To reduce astigmatism and high myopia, surgeons are looking into alternatives and using various incision techniques as well as phakic intraocular lenses or clear lens extraction to achieve emmetropia. High hyperopia with short axial length and high required intraocular lens power are corrected by piggyback intraocular lens implantation. The use of multifocal intraocular lenses compensates for the loss of accommodation after lens extraction.
Astigmatism↗
Hyperopia correction by noncontact holmium: YAG laser thermal keratoplasty: five-pulse treatments with 1-year follow-up.
BACKGROUND: Previous noncontact holmium (Ho): YAG laser thermal keratoplasty (LTK) studies on correction of low to moderate hyperopia have used treatment algorithms based on ten-pulse, variable-pulse-energy treatment parameters. The purpose of this study was to evaluate the safety, effectiveness, and stability of new five-pulse, constant-pulse-energy treatment parameters for noncontact Ho:YAG LTK. METHODS: Thirty-nine hyperopic patient eyes [up to +4.75 diopters (D) refractive error] were treated using simultaneous noncontact delivery of Ho:YAG laser energy (Sunrise) with two symmetrical octagonal rings of eight spots per ring and radial spot patterns on centerline diameters of 5 and 6 mm (group A), 6 and 7 mm (group B), or 6.5 and 7.5 mm (group C). Each ring of spots received five pulses of laser light at 5 Hz pulse repetition frequency and a fixed pulse energy of 240 mJ. Thirty of the 39 patient eyes (77%) had 1-year follow-up exams. RESULTS: At 1 year, the mean Snellen uncorrected distance visual acuity lines gained was 3.7 +/- 0.5/6.8 +/- 2.7/5.3 +/- 3.3 for groups A, B, and C. The mean changes in subjective manifest refraction (spherical equivalent) were -2.08 +/- 1.13 D, -1.83 +/- 0.88 D, -1.22 +/- 0.88 D for groups A, B, and C respectively. None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. There were no clinically significant complications in any patient. CONCLUSION: This clinical study indicates that five-pulse noncontact LTK treatments of low hyperopia are safe and effective. The stability has to be confirmed with longer follow-up.
Adult↗
[Assessment of refractive difference after photorefractive keratectomy. A comparison between keratometry and computer-assisted video keratography].
UNLABELLED: The purpose of this study was to determine which corneal curvature values most closely correlated to change in subjective manifest refraction following excimer laser photorefractive keratectomy (PRK). METHODS: Excimer laser PRK was performed on ten eyes of ten patients (mean age: 37.3 years). Preoperative refractive errors ranged from -2.25 to -8.75 diopters. Preoperatively and 1 month postoperatively, we determined the spherical equivalent of the manifest refraction (corrected for a 12 mm vertex distance) and measured corneal power using standard keratometry (Bausch and Lomb keratometer) and computerized videokeratography (EyeSys Corneal Analysis System). We collected five corneal values: standard keratometry, videokeratography-derived simulated keratometric readings calculated using the axial, instantaneous and refractive formulas, and corneal refractive power over the central 3-mm zone (effective refractive power); apart from the traditional refractive index of the cornea (n = 1.3375), we used the refractive value of the anterior corneal stroma (n = 1.376). For each of the five corneal values, we subtracted the change in corneal power from the change in manifest refraction and calculated the means and standard deviations. RESULTS: The mean differences between the refraction and the corneal values for a refractive index of 1.3375/1.376 were: 0.89 +/- 0.54*/1.26 +/- 0.59* for standard keratometry; 1.64 +/- 0.75*/1.37 +/- 0.7*, 4.03 +/- 1.86*/ 3.86 +/- 1.87*, and 1.16 +/- 0.76*/0.91 +/- 0.74* for the axial, instantaneous, and refractive videokeratography values, respectively; and 0.83 +/- 1.03*/0.39 +/- 1.08 for the effective refractive power (*,p < 0.05). CONCLUSIONS: In our series, only the values for the effective refractive power, calculated with the refractive Index of the anterior stroma of the cornea, were not statistically different from the change in manifest refraction.
Adult↗
Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty: U.S. phase IIA clinical study with 2-year follow-up.
PURPOSE: This study was performed to determine the long-term efficacy, safety, and stability of noncontact holmium:yttrium aluminum garnet (Ho:YAG) laser thermal keratoplasty (LTK) for correction of low-to-moderate hyperopia. METHODS: The authors treated 1 eye each of 28 patients for correction of low-to-moderate hyperopia (up to +3.88 diopters [D] refractive error) using the Sun 1000 Corneal Shaping System (Sunrise Technologies, Inc., Fremont, CA). Treatments were performed with one or two rings of eight spots per ring with centerline diameters of 6 mm (one ring) or 6 and 7 mm (two rings), ten pulses of laser light at 5-Hz pulse repetition frequency, and pulse energies ranging from 208 to 242 mJ. Follow-up was 2 years. RESULTS: At 2 years after surgery, uncorrected distance visual acuity was improved by 1 or more lines of Snellen visual acuity in 19 (73%) of 26 of the treated eyes. The mean lines gained was 2.5 +/- 2.2/3.3 +/- 2.7 for one- and two-ring treatment groups, respectively. The mean change in spherical equivalent of the subjective manifest refraction was -0.53 +/- 0.33 D/-1.48 +/- 0.58 D for one- and two-ring treatment groups. Regression between 1 and 2 years was 0.01 D and 0.16 D, respectively. In the one-ring treatment group (18 eyes), 13 eyes (72%) had refractive corrections (range, -0.38 to -1.13 D), and 5 eyes (29%) were unchanged (within +0.25 D) relative to their preoperative measurements. In the two-ring treatment group, all eight eyes (100%) had reductions in their hyperopia (range of corrections, -0.38 to -2.25 D). None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. There were no sight-threatening complications. CONCLUSIONS: This initial U.S. clinical study indicates that noncontact laser thermal keratoplasty treatment of low hyperopia is safe and produces modest but persistent corrections with 2-year follow-up. Expanded studies of this treatment method are warranted.
Adult↗
Lensification of the posterior corneal surface. An unusual proliferation of lens epithelial cells.
BACKGROUND: Abnormal proliferation of lens epithelial cells occurs in a variety of situations, such as anterior and posterior subcapsular cataracts and secondary cataract formation. The purpose of this report is to document an unusual occurrence of diffuse proliferation of lens epithelium and capsule along the posterior corneal surface. METHODS: The authors performed penetrating keratoplasty to remove an edematous and scarred cornea is a 19-year-old Indian man. Three years previously, the patient had undergone penetrating keratoplasty and extracapsular cataract extraction to treat a nonhealing corneal ulcer. The keratectomy specimen was processed for conventional light microscopy. Five-micrometer sections were stained with hematoxylin-eosin and the periodic acid-Schiff methods. RESULTS: Intraoperatively, the eye was found to be aphakic with an intact posterior capsule. The iris tissue consisted of fibrotic, pigmented remnants adherent to the peripheral cornea for 360 degrees, closing the angle and capsular fornix. Histologically, cataractous lens material including proliferated lens epithelial cells and capsule diffusely lined the posterior corneal surface along a thick retrocorneal fibrous membrane. CONCLUSIONS: This case represents a new category of lens epithelial cell proliferation or migration or both that covers entirely the posterior corneal surface. The authors believe the term lensification is appropriate for the condition described herein.
Adult↗
Incision sizes for foldable intraocular lenses.
OBJECTIVE: The purpose of the study is to determine the minimal incision sizes required for implantation of a variety of different foldable intraocular lenses (IOLs) and to evaluate the effect of incision size on tissue damage. DESIGN: Randomized experimental study. PARTICIPANTS: Sixty-nine fresh human cadaveric eyes: 15 (pilot study), 48 (main study), and 6 (scanning electron microscopy study). INTERVENTION: Implantation of foldable IOLs into cadaveric eyes. MAIN OUTCOME MEASURES: In 48 fresh human cadaveric eyes, limbal corneal tunnel incisions were made, and in a randomized fashion, 8 different foldable IOLs of 20.5 diopters (D) were inserted: 4 silicone (SI-30NB, Allergan Medical Optics, Irvine, CA; C10UB, Chiron Ophthalmics, Inc, Irvine, CA; LI41U, IOLAB, Chiron Ophthalmics, Inc, Irvine, CA; AA-4203, Staar Surgical Company, Monrovia, CA); two soft acrylic (MA60BM and MA30BA, both Alcon Laboratories, Inc, Ft. Worth, TX); and two hydrogel models (SH30BC, Alcon; H60M, Storz Ophthalmics, Inc, St. Louis, MO). For each IOL model, six insertions were performed with a recommended implantation device. Using calipers, the authors measured internal and external incision sizes before and after insertion. Scanning electron microscopy was performed on selected incisions in six additional human cadaveric eyes. RESULTS: Incision sizes after insertion ranged from 3.2 to 3.8 mm. The smallest incisions permitting IOL insertion were associated with the injectors. However, these incisions enlarged after insertion by approximately 11% and then were similar to the incision sizes after forceps insertion of the high-refractive-index silicone, the 5.5-mm optic acrylic, and the one-piece hydrogel IOL. The largest incisions were associated with the 6-mm acrylic IOL and the three-piece silicone IOL with a lower refractive index. The scanning electron microscopy showed tearing of corneal tissue after implantation through the smallest incision; this was more pronounced with injectors than with forceps. CONCLUSIONS: Corneal tunnel incisions enlarged up to 11% after insertion of foldable IOLs through the smallest possible incision. With current technology, the smallest postinsertion incision size of a 20.5-D foldable IOL is 3.2 mm.
Cadaver↗
Corneal endothelium: an important structure for cataract and refractive procedures.
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Adult↗
Changes in computerized videokeratography induced by artificial tears.
PURPOSE: To analyze the effect of several standard artificial tear preparations on computerized videokeratographic measurements. SETTING: Cullen Eye Insitute, Baylor College of Medicine, Department of Ophthalmology, Houston, Texas, USA. METHODS: We evaluated one eye each in 18 normal volunteers. Using the EyeSys Corneal Analysis System (EyeSys Technologies), we obtained corneal topographic measurements at baseline and 0.5, 1, 2, 3, 4, 5, 6, 8, and 10 minutes after instillation of the following preparations: balanced salt solution, Tears Naturale II, Tears Naturale Free, Cellufresh, Celluvisc, HypoTears, and HypoTears PF. We analyzed changes in curvature of the keratographic rings at radii 1 to 5 mm and changes in keratometric-equivalent astigmatic power and meridian. RESULTS: All preparations except HypoTears and Tears Naturale II induced statistically significant, time-dependent changes in mean corneal power in the central 5 mm corneal zone compared with baseline measurements (P < .05). The relationship between change in dioptric power over time varied with preparation type and was nonlinear in nature. In all cases, the mean induced change was < or = 0.5 diopter. Except for Celluvisc, tear administration produced minimal changes in the values of corneal astigmatic power or meridian. CONCLUSION: When performing serial measurements of mean corneal power, the greatest consistency was achieved with no tears or with instillation of HypoTears or Tears Naturale II.
Astigmatism↗
New caliper for small incision cataract surgery.
In cataract surgery, incision size determines various factors such as wound stability, corneal curvature changes, postoperative induced astigmatism, and visual rehabilitation. A mechanical caliper has been developed for experimental and clinical studies of incision sizes ranging between 1.0 and 6.0 mm. The caliper has a screw that allows measurements in 0.1 mm steps. The device is produced for two ranges: 2.0 to 4.0 mm and 1.0 to 6.0 mm. The precision of 0.1 mm was confirmed with a vernier caliper in a cadaver eye study. Unlike gauges that determine incision size by trial and error and a combined system of internal and vernier calipers, only one measurement is necessary with this caliper.
Astigmatism↗