Biomedical subjects

T Kohnen

Publications and source records attributed to T Kohnen.

90 records · Page 5Linked to original sources

PubMed1996

Computerized videokeratography and keratometry in determining intraocular lens calculations.

PURPOSE: To compare the accuracy of standard keratometry and computerized videokeratography (CVK) in determining intraocular lens (IOL) power calculations. METHODS: Using the EyeSys Corneal Analysis System, we prospectively obtained CVK maps on 75 eyes of 69 patients scheduled to have phacoemulsification with implantation of a posterior chamber intraocular lens. Using manifest refraction obtained at 6 weeks postoperatively, we optimized the calculations for the Hoffer Q, Holladay, and SRK/T formulas for standard keratometric and the following six CVK values: average curvatures at the 1 mm, 2 mm, and 3 mm zones, the keratometric equivalent at the 3 mm zone, and the Stiles-Crawford weighted averages over the 3 mm and 6 mm zones. The accuracy of these parameters was determined by calculating the mean absolute error and percentage of patients with accuracy within < or = 0.5 diopter (D), < or = 1.0 D, and < or = 2.0 D. RESULTS: Keratometrically derived data were slightly more accurate than the CVK-derived values. The average difference in mean absolute error between the keratometric and CVK values was 0.13 D for the Hoffer Q formula, 0.11 D for the Holladay, and 0.08 D for the SRK/T. CONCLUSIONS: In this population of patients, we found the CVK-derived corneal curvature values to be slightly less accurate than standard keratometry in predicting IOL power. However, CVK provides important corneal curvature data for IOL calculations in patients with abnormal or surgically altered corneal surfaces.

Anthropometry↗

PubMed1996

Methods to control astigmatism in cataract surgery.

The correction of astigmatism during cataract surgery has evolved due to recent basic and clinical studies. To control surgically induced astigmatism, the surgeon has many options, including varying incision parameters, astigmatic keratotomy, scleral flap recession and resection, toric intraocular lens implantation, and modifying postoperative medical treatment. The recent literature is reviewed, and our current approach for cataract surgery is discussed.

Astigmatism↗

PubMed1996

Corneal topographic changes and induced astigmatism resulting from superior and temporal scleral pocket incisions.

BACKGROUND AND OBJECTIVE: To determine the corneal topographic changes that are induced by superior and temporal 5-mm scleral pocket incisions. PATIENTS AND METHODS: The authors retrospectively reviewed the records of 43 patients who underwent phacoemulsification with posterior chamber lens implantation through unsutured 5-mm scleral pocket incisions, 24 superiorly and 19 temporally. Corneal curvature was measured using computerized videokeratography, and the induced astigmatism was calculated with the Holladay-Cravy-Koch formula. RESULTS: At 4 to 6 weeks, postoperatively there was mild flattening along with the meridian of the incision in both groups. The change was greater with the superior incisions, but the differences between the groups were not statistically significant. Surgically induced astigmatism was 0.7 D (+/-0.1 D) in the eyes that received superior incisions, and 0.3 D (+/-0.1 D) in the eyes that received temporal incisions; this difference was statistically significant (P < .03). CONCLUSIONS: At 4 to 6 weeks postoperatively, temporal 5.0-mm scleral pocket incisions provide more stable postoperative topography than do superior scleral pocket incisions.

Adult↗

PubMed1996

Secondary cataract formation following pediatric intraocular lens implantation: 6-month results.

Secondary membrane formation is the most common complication of posterior chamber intraocular lens (PC IOL) implantation in children. The purpose of this study was to determine the effect of various methods of managing the posterior capsule and anterior vitreous on the rate of posterior capsular opacification in children implanted with PC IOLs. We retrospectively studied 16 eyes of 12 children (age 1.5-12 years) implanted with PC IOLs; the follow-up period was at least 6 months. The posterior capsule and anterior vitreous were managed in a variety of ways: in 5 eyes the posterior capsule was left intact, and 11 eyes underwent posterior capsulorehexis (PCCC)-6 cases without and 5 cases with anterior vitrectomy. In two eyes of each of the last two groups, posterior optic capture was performed. Visually significant secondary cataract developed in all five eyes with intact posterior capsules and in the four eyes that had undergone PCCC without vitrectomy and without posterior optic capture. The optical axis remained clear in all eyes that had undergone vitrectomy and in all eyes treated with posterior optic capture. Each procedure, posterior optic capture and anterior vitrectomy appears to be effective in preventing or delaying posterior opacification in lens implantation in infants and children. However, a longterm follow-up is required to determine the efficacy and safety of these two approaches.

Cataract↗

PubMed1996

Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty. United States phase IIA clinical study with a 1-year follow-up.

PURPOSE: This study was performed to evaluate the safety and effectiveness of noncontact holmium: YAG (Ho:YAG) laser thermal keratoplasty (LTK) for correcting low to moderate hyperopia. METHODS: Twenty-eight patients were treated unilaterally to correct low to moderate hyperopia (up to +3.88 diopters [D] refractive error) using simultaneous noncontact delivery of Ho:YAG laser energy. Treatment parameters included one or two symmetric octagonal rings of eight spots per ring with centerline diameters of 6 mm (1 ring) or 6 and 7 mm (2 rings), ten pulses of laser light at 5-Hz pulse repetition frequency, and variable pulse energy, ranging from 208 to 242 mJ. Follow-up was 1 year in 26 (93%) of the 28 patients. RESULTS: At 1 year postoperatively, uncorrected distance visual acuity was improved in all patients. The mean change in subjective manifest refraction (+/- spherical equivalent [SE]) was -0.55 +/- 0.33 D and -1.64 +/- 0.61 D for one and two-ring treatment groups, respectively, with good stability in the refractive change after approximately 6 months. In the one-ring treatment group (17 eyes), refractive corrections of -0.50 to -1.13 D were achieved in ten eyes (59%), and seven eyes (41%) were unchanged (within +/- 0.25 D) relative to their preoperative measurements. In the two-ring treatment group, all eight eyes (100%) had substantial refractive corrections (range, -0.75 to -2.50 D). Mean induced refractive astigmatism was 0.25 +/- 0.29 D and 0.47 +/- 0.53 D for one- and two-ring treatments, respectively. None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. These was no clinically significant change in endothelial cell density with respect to preoperative values. Glare and contrast sensitivity testing indicate that peripheral corneal opacities produced by LTK do not degrade vision. The amount of refractive change in each group was correlated with the amount of laser pulse energy. CONCLUSIONS: This initial United States clinical study with 1-year follow-up indicates that noncontact LTK treatment of low hyperopia is safe and effective, providing persistent, though modest, refractive corrections in 59% of the one-ring group and larger, persistent, refractive corrections in 100% of the two-ring group.

Adult↗

PubMed1995

Comparison of the induced astigmatism after temporal clear corneal tunnel incisions of different sizes.

A prospective, randomized study compared the surgically induced astigmatism after 3.5 mm, 4.0 mm, and 5.0 mm temporal corneal tunnel incisions over six months. We studied 60 eyes of 60 patients who had phacoemulsification through a two-step clear corneal tunnel incision and implantation of one of three posterior chamber intraocular lenses (IOLs). Patients were divided into three groups of 20 each: Group A, cartridge injection of a foldable plate-haptic silicone IOL through a 3.5 mm self-sealing incision; Group B, cartridge injection of a disc silicone IOL through a 4.0 mm self-sealing incision; Group C, 5.0 mm optic poly(methyl methacrylate) IOL through a 5.0 mm incision with one radial suture. Corneal topography data were obtained using a computerized videokeratographic analysis system preoperatively and one week and six months postoperatively. Vector analysis was performed to calculate the surgically induced astigmatism. After the first postoperative week, mean induced astigmatism was 0.63 diopters (D) (+/- 0.41) in Group A, 0.64 D (+/- 0.35) in Group B, and 0.91 D (+/- 0.77) in Group C. After six months, it was 0.37 D (+/- 0.14) in Group A, 0.56 D (+/- 0.34) in Group B, and 0.70 D (+/- 0.50) in Group C. Surgically induced astigmatism was significantly lower in Group A than in Group B (P < .05) and Group C (P < .005) after six months. Vector analysis demonstrated that temporal corneal tunnel incisions induced clinically minimal astigmatism over six months postoperatively depending on incision size.

Aged↗

PubMed1995

[Postoperative intraocular pressure in the first days after intraocular administration of hyaluronic acid solution with different viscosities].

BACKGROUND: Viscoelastic substances are used in anterior segment surgery to reduce tissue trauma and endothelial cell loss and to serve as space maintainer. Healon GV (approximately greater viscosity), a hyaluronic acid product with a ten times higher viscosity than Healon, is utilized in complicated procedures (vitreous pressure, flat anterior chamber, congenital cataracts, etc.) and often in phacoemulsification. Intraocular pressure (IOP) rise following incomplete removal is a known problem. MATERIALS AND METHODS: A prospective randomized study was performed to evaluate the IOP following cataract surgery with Healon or Healon GV and different removal times (RT). Forty patients (forty eyes) having uncomplicated phacoemulsification with foldable silicone posterior chamber lens implantation and identical viscoelastic removal technique were assigned to four groups: Healon with 20 or 40 seconds (sec.) RT, Healon GV with 20 or 40 sec. RT. All surgeries were performed by the same surgeon using the same technique especially for the removal of the viscoelastic. All patients had an identical pre- and postoperative medication. Intraocular pressures were obtained using Goldman's applanation tonometry preoperatively, six, 24, 36, and 48 hours postoperatively. RESULTS: The IOP follow-up showed no significant difference between the two viscoelastic substances and the two different removal times of 20 and 40 sec. (t-test). In four patients (two of the Healon-groups, two of the Healon GV-groups) the IOP required treatment. On the second postoperative day, the same four patients showed IOP lower than 22 mm Hg. The highest mean-IOP (mm Hg) in both Healon-groups was obtained at 24 hours postoperatively: 18.5 +/- 3.9 SD (Healon); 17.3 +/- 5.9 SD (Healon GV). CONCLUSION: The incidence of postoperative rise in IOP using high viscosity hyaluronic acid (Healon GV) can be minimized by the applied removal technique. Both viscoelastics-despite of higher molecular weight and viscosity-can be removed equally from the anterior chamber following phacoemulsification and posterior chamber lens implantation utilizing IOP as a parameter in vivo.

Aged↗

PubMed1995

[Congenital familial cornea plana with ptosis, peripheral sclerocornea and conjunctival xerosis].

BACKGROUND: Cornea plana is an extremely rare, congenital hereditary malformation of the corneo-scleral shape. The curvatures of cornea and sclera are nearly equal with an indistinct limbus. In addition to the flatness, there is a peripheral sclerocornea that produces a pseudomicrocornea. The low corneal refraction and the short anterior segment often result in hyperopia. Myopia is also described. Usually the posterior segment is not involved. MATERIALS AND METHODS: A young man of 22 years, his three- and five-year-old sons, and his newborn daughter showed this hereditary abnormality of the cornea. In this uncommon anomaly we measured corneal curvature, refraction, diameter and in three of the four patients echographical length of the bulbi. RESULTS: The family showed an autosomal dominant inheritance of the cornea plana. The corneal refraction was less than 32 diopters. The scleral encroachment caused an oval cornea measuring horizontally between 5 and 6.5 mm, vertically 4 to 5 mm. Additionally a pseudoblepharoptosis and a conjunctival xerosis of the father and his sons was observed, which is not regularly found. A-scan measuring of the bulbi revealed age-related normal values. CONCLUSIONS: There is no evidence for progression of this anomaly during life. No therapeutical consequences are necessary. To preserve a satisfactory function a conscientious orthoptical maintainance should be guaranteed.

Adult↗

PubMed1995

[Surface quality of flexible silicone intraocular lenses. A scanning electron microscopy study].

BACKGROUND: Soft intraocular lenses (IOLs) have been developed to be folded during insertion to allow implantation through a small incision. The surface of the IOL is of great importance in postoperative inflammation and long-term acceptance of the implant. Rough and sharp edges can damage delicate intraocular tissues. The purpose of this study was to analyze new, foldable silicone IOLs for surface quality prior to and following folding. MATERIALS AND METHODS: Eleven silicone IOLs of different types were included in this study (four one-piece plate-haptic silicone IOLs and seven three-piece silicone IOLs with polypropylene, PMMA or polyimid haptics). We performed scanning electron microscopy on brand-new IOLs prior to and following folding either with forceps or inserter. Special attention was given to the silicone optic surface, optic edges, haptic-optic junctions and the haptic itself. Photographs were taken at 5-350 times magnification. RESULTS: All IOLS demonstrated a smooth and homogeneous optic surface at low magnification. At high-power magnification (X 350), distinctive surface patterns were evident in some IOLs, which turned out to be artefacts. The edge finish showed surplus silicone material and molding flash in six of 11 IOLs. Positioning holes of the 4 plate-haptic IOLs were, except in one IOL, rounded and not rough. Photographs of the haptic-optic junctions revealed surplus material or clefts between the haptic and optic in six of the 7 three-piece IOLs; the loop ends of two IOLs showed a roughened or irregular surface. We did not detect any IOL changes produced by folding. CONCLUSIONS: The silicone IOLs tested demonstrated generally acceptable surface properties, but most IOLs had regional surface irregularities of varying magnitude. The clinical impact of these remains to be established, but surplus material or surface defects might result in deposition of inflammatory cells, protein or microorganisms and synechia formation. Folding of the IOLs did not produce superficial defects.

Cataract Extraction↗

PubMed1995

[Alterations of heparin coating on intraocular lenses caused by implantation instruments].

BACKGROUND: In the last years heparin surface-modified intraocular lenses (HSM IOLs) were used for special indications like uveitis, synechia, congenital cataract or pseudoexfoliation syndrome. A monolayer of heparin molecules on the surface of PMMA-IOLs causes a reduced postoperative inflammatory reaction and produces a higher long-term biocompatibility than PMMA-IOLs without surface-modification. The study was designed to evaluate the possible damage of this heparin-monolayer on the PMMA-IOL by different metallic implantation forceps and different grasp-pressure. MATERIALS AND METHODS: Different implantation instruments were used to grasp HSM and conventional PMMA-IOLS. We designed a new device to generate and measure the pressure by the implantation forceps on the IOL in online-mode. After staining the heparin-monolayer with toluidin blue the surface alterations on the intraocular lenses were examined for surface alterations, especially of the heparin-monolayer, by light and scanning electron microscopy subsequently. RESULTS: Implant forceps produced defects of the heparin layer and the PMMA-material. Each implantation forceps induced a specific pattern of destructed heparin surface in the grasp area. These defects showed high correlation with the pressure and the morphology of the forceps as shown by light and scanning electron microscopy. CONCLUSIONS: Mechanical irritation during the implantation procedure destroyed the heparin layer on PMMA-IOLs in the grasp-area. Clinical consequences are not yet known, but possible. An instrument with rounded, soft and smooth grasp-surface is required for implantation of HSM IOLs to avoid surface alterations, so that the patients get maximum profit by the heparin-modification.

Cataract Extraction↗

PubMed1995

[Endothelial cell loss after phacoemulsification and 3.5 vs. 5 mm corneal tunnel incision].

This prospective study was performed to compare the central endothelial cell loss (ECL) after phacoemulsification and 3.5 with 5 mm temporal clear-corneal incision. Moreover, the influence of ultrasound time and power on postoperative endothelial cell density was evaluated. PATIENTS AND METHODS. Sixty-two patients (age 71 +/- 7.7 years) without corneal pathology were operated by phacoemulsification (Storz, Premiere) with a temporal, self-sealing, two-step clear-corneal incision followed by posterior chamber IOL implantation under viscoelastic (1% sodium hyal-uronate). Thirty-one one-piece plate-haptic foldable silicone IOLs (Chiron C10; Staar Surgical AA-4203) were implanted by an injector through a 3.5 mm incision (group A). The other 31 PMMA IOLs (Pharmacia 809P) were implanted through a 5 mm incision (group B). One surgeon performed all operations with the same technique (bimanual phacoemulsification in the capsular bag). Sutureless wound closure was performed in group A, while the wounds in patients of group B were closed with a single radial stitch. The central endothelial cell counts were recorded preoperatively, on days 2-5 and 6 months postoperatively using contact specular microscopy. RESULTS. The collective data revealed a cell loss of 7.9% (+/- 4.1 SD) on days 2-5 postoperatively and 6.7% (+/- 2.9) after 6 months. A direct linear relationship was found to exist between ultrasound time (UT) and ECL. In group A (7 patients) the ECL slightly increased from 3.5% in the first week postoperatively to 3.8% after 6 months, operated under UT < or = 1 min 30 sec. The ECL decreased from 8.2% to 6.4% after 6 months in group A (19 patients), operated under UT of 1 min 30 sec, and from 10.8% to 8.9% under UT of 2 min 31 sec-3 min 30 sec (5 patients). The ECL in group B decreased from 6.3% in the first postoperative week to 5.4% 6 months postoperatively, operated under UT < or = 1 min 30 sec (10 patients), from 8.1% to 7%, operated under UT of 1 min 31 sec-2 min 30 sec (14 patients), and from 11.2% to 10.4% under UT of 2 min 31 sec-3 min 30 sec (7 patients). CONCLUSION. Endothelial cell loss of 6.7% after phacoemulsification through a temporal clear-corneal incision compares favorably with other series in which cell loss was determined following cataract surgery with or without IOL implantation. Phacoemulsification and 3.5 mm clear-corneal incision evoked less ECL of 6.2% compared with phacoemulsification and 5 mm clear-corneal incision with ECL of 7.3% after 6 months.

Aged↗

PubMed1995

[Effects of Nd:YAG microexplosions on heparin-coated PMMA intraocular lenses].

UNLABELLED: Surface modification of intraocular lenses (IOL) have improved the quality of cataract surgery. Heparin surface-modified (HSM) IOL are implanted for special indications (e.g., recurrent uveitis, cataract surgery for children, preoperative synechia) because of decreased postoperative inflammatory reactions and higher long-term biocompatibility. Nevertheless, secondary cataract, precipitates and fibrinous membranes appear. The YAG laser is used for treatment. METHODS: PMMA intraocular lenses with or without a heparin monolayer were exposed to Nd:YAG laser. The experiment was performed under BSS using different energy levels and distances to the IOL. The heparin monolayer was stained with toluidin blue. Subsequently, the surface of the intraocular lenses was examined with light and scanning electron microscopy. RESULTS: The YAG laser marks of HSM IOL and PMMA IOL showed no morphological differences. Microexplosions and pressure waves of the Nd:YAG laser cleared parts of the heparin monolayer in the area of the laser spots dependent on energy distance to the IOL. Even "breakdown" behind the HSM IOL without any PMMA lesion shown circular destruction of the heparin monolayer. CONCLUSIONS: The heparin surface defect of HSM IOL after YAG laser treatment should be taken into consideration, because a decreased heparin effect in vivo could be possible.

Heparin↗

PubMed1995

[The anti-inflammatory effect of heparin-containing infusion solutions during phacoemulsification].

UNLABELLED: The use of heparin prevented postoperative intraocular fibrin-clot formation in the rabbit after vitrectomy and cyclocryotherapy. A low rate of postoperative intraocular inflammation was observed in our patients receiving phacoemulsification with heparin infusion solution (slit-lamp examination). To verify this effect a randomized, prospective study was performed using laser-flare cell photometry (LFCP) for measuring protein concentration in the anterior chamber. PATIENTS AND METHODS: Seventy-two patients (49-87 years of age) were randomly assigned to one of the following two surgical groups (temporal clear corneal tunnel incision with phacoemulsification): group A: foldable silicone IOL (Chiron C10), no stitch (3.5 mm incision); group B: PMMA-IOL (Pharmacia 809P) with one radial suture (5 mm incision). Fifty percent of the patients in each group received, in addition to the regular phaco infusion, 1 ml of heparin sodium (-H = without heparin; +H = with heparin). Aqueous flare was measured preoperatively as well as on days 1 and 3 following phaco + IOL with LFCP (Modell FC-1000; Kowa Company). RESULTS: In group A1 (-H) or B1 (-H) the mean flare values (in photon counts/ms) increased from a preoperative value of 7.0 +/- 1.7 (mean +/- SD) or 6.9 +/- 1.2 to 20.2 +/- 3.1 or 20.1 +/- 3.0 on the 1st postoperative day, whereas they decreased again to 13.8 +/- 2.9 or 14.8 +/- 3.1 on day 3 following surgery. In groups with heparin sodium A2(+H) and B2(+H) the flare values only increased from 7.2 +/- 1.3 or 7.1 +/- 1.3 to 12.9 +/- 4.0 or 13.8 +/- 3.8 on day 1, and decreased to 8.0 +/- 2.8 or 8.8 +/- 3.0 on the 3rd postoperative day. The mean postoperative flare values were significantly lower in the groups with additional heparin (p < 0.01). CONCLUSIONS: Heparin sodium in the infusion solution during small incision cataract surgery showed an antiinflammatory effect in the early postoperative period. There was no significant difference between the two IOL materials.

Aged↗

PubMed1994

[Systemic complications and side effects of retrobulbar anesthesia in risk patients].

BACKGROUND: Serious systemic complications with possibly lethal exit after retrobulbar anesthesia have been reported. The present study was performed to evaluate the incidence of complications after anesthesia in risk patients with pre-existing diseases. 2.8% of 3000 cataract operations in our department during October 1991 to April 1993 were performed under general anesthesia, 97.2% under local anesthesia. PATIENTS AND METHODS: 1000 anesthesia protocols of these cataract operations under retrobulbar anesthesia and facial block with anesthesia stand-by were analyzed retrospectively. After retrobulbar injection in Atkinson technique we performed a modified O'Brien facial block. The patients were assigned to five different risk groups on the basis of a special point system. RESULTS: The mean age of the patients increased with the risk group from 60.4 years in group 1 to 77.1 years in group 5. Cardiovascular, pulmonary and general risk factors appeared more frequently in the groups of higher risk. The frequency of cardiovascular complications was dependent on affiliation to risk group. The percentual frequency of cardiovascular complications increased from 1.7% in risk group 1 to 7.7% in risk group 5. Decrease of heart rate or blood pressure of more than 30%, or in combination, with the necessity of medical treatment occurred absolutely and relatively most frequently. The frequency of cardiovascular complications amounted 2.2% in the mean. Life-threatening complications with the need of endotracheal intubation or other occurred in 0.1%. CONCLUSION: The relatively high total frequency of systemic complications of 2.4% is related with age and preexisting diseases. The results underline the necessity of anesthesia stand-by in risk patients with the essential requirements for treatment of typical complications.

Aged↗

PubMedDate not supplied

Long-term endothelial cell loss following phacoemulsification through a temporal clear corneal incision.

PURPOSE: To evaluate central endothelial cell loss (ECL) following clear corneal cataract surgery using two different incision sizes and the effect of ultrasound time (UST) and power on postoperative ECL and various cell parameters. METHODS: Fifty-eight patients had phacoemulsification through temporal, two-step clear corneal tunnel incisions. In Group A (n = 28), a one-piece, plate-haptic foldable silicone intraocular lens (IOL) was implanted through a 3.5 mm sutureless incision. In Group B (n = 30), a poly(methyl methacrylate) IOL was implanted through a 5.0 mm incision with one radial suture. The central endothelial cell counts were recorded preoperatively and postoperatively at 2 to 5 days, after 6 months, and after 1 year. Color-coded, computer-assisted specular microscopy was used for special cell analysis after 1 year. RESULTS: Collective data showed an ECL of 7.9 +/- 4.1% (mean +/- standard deviation) at 2 to 5 days postoperatively, 6.7 +/- 2.9% after 6 months, and 7.3 +/- 3.3% after 1 year. A direct linear relationship was found between ECL and UST and power: ECL increased as UST and power increased. After 1 year, ECL in Group A was 4.2% with UST < or = 11/2 minutes, 6.7% with UST > 11/2 to 21/2 min, and 9.6% with UST > 21/2 to 31/2 min; in Group B it was 6.0%, 7.5%, and 11.4%, respectively. Specular microscopy showed normal, age-related cell parameters 1 year postoperatively. CONCLUSIONS: Phacoemulsification with 3.5 mm clear corneal incisions produced slightly less ECL (6.7%) than phacoemulsification with 5.0 mm incisions (7.9%). Total ECL of 7.3% at 1 year postoperatively compared favorably with ECL rates of other cataract extraction methods.

Aged↗

PubMedDate not supplied

Silicone-covered forceps for rigid intraocular lens implantation.

Metal implantation forceps can damage the surface of poly(methyl methacrylate) and heparin-surface-modified intraocular lenses (IOLs) during insertion. A new implantation forceps with silicone sleeves covering the tips has been successfully used during IOL implantation. Scanning electron microscopic studies showed that the silicone sleeves prevent forceps-induced IOL surface defects.

Biocompatible Materials↗

PubMedDate not supplied

Histologic changes and wound healing response following 10-pulse noncontact holmium:YAG laser thermal keratoplasty.

BACKGROUND: Noncontact holmium:YAG laser thermal keratoplasty (Ho:YAG LTK) is a promising new technology for correction of hyperopia and astigmatism. We studied the acute histologic changes and wound healing response following Ho:YAG LTK performed with treatment parameters encompassing those used in clinical studies. METHODS: We performed 10-pulse noncontact Ho:YAG LTK on three human corneas 1 day before their removal at penetrating keratoplasty and on six New Zealand white rabbit corneas followed for up to 3 months. Tissues were studied with light and transmission electron microscopy and immunohistochemistry. RESULTS: The amount of acute tissue injury increased according to the pulse radiant energy. In human corneas, changes in the irradiated zones included epithelial cell injury and death, loss of fine filamentous structure in Bowman's layer, disruption of stromal lamellae, and keratocyte injury and death. In the rabbit corneas, similar acute changes were noted. By 3 weeks, epithelial hyperplasia and stromal contraction were present. Wound healing in the rabbits included repair of the epithelial attachment complex, keratocyte activation, synthesis of type I collagen, partial restoration of stromal keratan sulfate and type VI collagen, and retrocorneal membrane formation. CONCLUSIONS: Noncontact Ho:YAG LTK produces acute epithelial and stromal tissue changes and in rabbit corneas stimulates a brisk wound healing response.

Animals↗

PubMedDate not supplied

Confocal microscopic imaging of reticular folds in a laser in situ keratomileusis flap.

PURPOSE: To report the clinical and confocal microscopic characteristics of reticular folds (mudcracks) in a cornea after laser in situ keratomileusis (LASIK). METHODS: A 30-year-old male showed reticular flap folds on slit-lamp examination 1 week after LASIK. In addition to slit-lamp biomicroscopy, confocal in vivo microscopy was performed. RESULTS: Examination with a confocal white-light slit-scanning microscope revealed distinct folds of Bowman's layer and underlying microfolds throughout the flap stroma. After flap re-lifting, no changes could be determined, either clinically or by confocal microscopy. At 12 months following the procedure, best spectacle-corrected visual acuity was slightly improved, but the folds, as imaged by confocal microscopy, still persisted. CONCLUSIONS: In the present case, reticular folds after LASIK involved the entire thickness of the flap. Simple flap lifting was not sufficient for smoothing out the folds.

Adult↗