Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia.

PURPOSE: To evaluate and compare the recovery of postoperative corneal sensitivity after laser in situ keratomileusis and photorefractive keratectomy for the correction of low myopia. METHODS: In a prospective study, 17 consecutive eyes (17 patients) underwent laser in situ keratomileusis to correct myopia ranging from -3.25 to -6.75 diopters, and another 18 consecutive eyes (18 patients) underwent photorefractive keratectomy to correct myopia from -3.12 to -7.00 diopters. Corneal sensitivity was tested preoperatively and 1 week and 1, 3, and 6 months postoperatively using the Cochet-Bonnet esthesiometer. Corneal sensitivity was tested at the center of the cornea, and in four additional central points 2 mm from the corneal center (nasal, inferior, temporal, and superior). RESULTS: Corneal sensitivity after laser in situ keratomileusis was reduced at the ablated zone during the first 3 months after surgery (Wilcoxon rank sum test, P < .05), and only after 6 months it returned to its preoperative values. However, corneal sensitivity recovered its preoperative values 1 month after photorefractive keratectomy (Wilcoxon rank sum test, P > .05), except for the central corneal point, where 3 months were required. Comparing both groups, corneal sensitivity was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months (Mann-Whitney test, P < .05), except for the nasal central point, although no differences were found between both groups at 6 months (P > .05). CONCLUSIONS: In the correction of low myopia, corneal sensitivity at the ablated zone was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months after surgery. Only after 6 months were corneal sensitivity values similar in both groups.

Nocardial keratitis after laser in situ keratomileusis.

PURPOSE AND METHODS: Corneal interface central nodules appeared in a patient who underwent uncomplicated laser in situ keratomileusis (LASIK) retreatment for residual myopia. RESULTS/CONCLUSIONS: Nocardia asteroides keratitis was confirmed by microbiologic studies, which guided treatment. Six months after the appearance of the keratitis, the patient's uncorrected visual acuity was 20/45, and spectacle-corrected visual acuity was 20/40. The postoperative refraction was +0.75 -0.75 X 95 degrees, and slit-lamp examination revealed a clear cornea with a mild rounded scar in the central area. Night halos and starbursts were the main complaints in this patient. The immediate management of lifting the corneal flap for stromal bed scraping, fast microbial identification, and proper treatment was the key for the results in this patient.

Corneal wound healing after laser in situ keratomileusis in rabbits.

BACKGROUND: The aim of this study was to characterize the cell biology of wound healing in rabbit corneas subjected to laser in situ keratomileusis (LASIK). METHODS: Rabbit corneas underwent LASIK with various multizone photoablations or only a lamellar keratotomy followed by repositioning of the flap. We looked for indications for an active wound healing process. Immunohistochemistry for the extradomain A cellular fibronectin (EDA-cFn) or tenascin (Tn) and routine histology were examined. RESULTS: Four days after LASIK or lamellar keratotomy followed by repositioning of the flap, epithelial plugs and prominent keratocytes as well as Tn and EDA-cFn immunoreactions-indicative of a wound-healing process-appeared in the wound margins. Epithelial plugs were less conspicous, and prominent, presumably activated, keratocytes were no longer identified at the wound margin at 2.5 and 5 months after wounding. However, EDA-cFn and Tn immunoreactivities could still be observed. Only the stromal cells located in the periphery of the flap and in relatively close contact with the epithelium were surrounded by scar tissue expressing immunoreactivity for EDA-cFn or Tn. The central corneal stroma was devoid of scar tissue. CONCLUSION: Results indicate that the wound healing reaction after LASIK takes place only at the periphery of the microkeratome wound, leaving the central optical zone clear.

Contrast sensitivity after laser in situ keratomileusis.

PURPOSE: To evaluate the effect on contrast sensitivity function of laser in situ keratomileusis (LASIK) for the correction of myopia. SETTING: Alicante Institute of Ophthalmology, University of Alicante, Spain. METHODS: Fourteen eyes of 10 patients had LASIK to correct myopia ranging from 6.00 to 19.50 diopters (D). Mean preoperative myopia was 10.39 D +/- 3.69 (SD). Contrast sensitivity was tested preoperatively and 1, 3, and 6 months postoperatively using the CVS-1000E contrast sensitivity unit (VectorVision). RESULTS: Contrast sensitivity decreased 1 month postoperatively; the decrease was significant only at the low and intermediate spatial frequencies of 3 and 6 cycles per degree (cpd) (P = .034 and .030, respectively). Starting from the first month, there was rapid recovery of contrast sensitivity and at the third month, no statistically significant decrease at all spatial frequencies. Six months after surgery, there was an increase in contrast sensitivity values at 3, 12, and 18 cpd, although the changes were not significant. CONCLUSION: Although LASIK decreased contrast sensitivity values at low and intermediate spatial frequencies for 1 month after surgery, these values rapidly returned to the preoperative values at 3 months. The improvement at certain frequencies at 6 months suggests that LASIK can improve the quality of vision in eyes with moderate and high myopia.

Efficacy of synthetic and biological bioadhesives in scleral tunnel phacoemulsification in eyes with high myopia.

PURPOSE: To study the efficacy of a synthetic (cyanoacrylate) and a biological (fibrinogen) bioadhesive in sealing scleral tunnel incisions in cataract surgery. SETTING: Private institution with academic orientation. METHODS: This controlled clinical study comprised 126 eyes with high myopia (axial length > 28.0 mm) divided into three groups based on method of incision closure 10-1 nylon anchor suture; cyanoacrylate (Histoacryl); fibrinogen (Tissucol). Phacoemulsification was done through a double-valved scleral tunnel incision with an 8.0 mm arc. In all eyes, a hyperconcave, 7.0 mm optic, posterior chamber intraocular lens was implanted. RESULTS: Mean induced astigmatism at 12 weeks was 0.18 diopter (D) in the suture group, 0.50 D in the cyanoacrylate group, and 0.43 D in the fibrinogen group. The difference between the bioadhesive groups and the suture group was not significant. A mild inflammatory reaction occurred in the cyanoacrylate group. In the fibrinogen group, 3 eyes developed postoperative hypotony requiring reclosing of the incision with sutures and 5 eyes developed intraoperative hypotony requiring suture closure. These eyes were not included in the refractive analysis. These complications led to the suspension of the fibrinogen portion of the study after uneventful use of the bioadhesive in 26 eyes. CONCLUSION: The results of this study indicate that bioadhesives, especially synthetic ones such as cyanoacrylate, are an effective alternative to sutures in scleral tunnel cataract surgery. Future improvements in bioadhesives could extend their application to other ocular incision types.

Corneal endothelial changes after laser in situ keratomileusis.

PURPOSE: To ascertain whether 193 nm excimer laser in situ keratomileusis (LASIK) to correct high myopia causes in vivo changes in the human corneal endothelium 3 and 6 months after surgery. SETTING: Alicante Institute of Ophthalmology, University of Alicante, Spain. METHODS: Preoperative and serial postoperative specular microscopy of the central corneal endothelium was done in 33 eyes of 19 patients (Group 1) with a mean age of 34.3 years +/- 10.6 (SD) (range 20 to 60 years) who had LASIK to correct myopia of between 8.25 and 18.50 diopters (D) (mean 11.90 +/- 2.20 D). Twelve patients (20 eyes) were contact lens wearers (Group 2), and 7 (13 eyes) had never worn contact lenses (Group 3). The central endothelium was analyzed for several parameters including cell density, coefficient of variation in cell size, and hexagonality. The data obtained before surgery were compared with those obtained after surgery in all groups. RESULTS: There was no significant difference in age, sex, and preoperative myopia between Groups 2 and 3. In Group 1, mean cell density was significantly higher (3.5%) 6 months after surgery (P = .017) and the coefficient of variation decreased 3 and 6 months after surgery (P < .001); no significant changes were noted in the percentage of hexagonal cells. In Group 2, there was a significant increase in cell density (4.8%) 6 months after surgery (P = .010) and the coefficient of variation decreased at 3 and 6 months after surgery (P < .001); the hexagonality did not change postoperatively. In Group 3, there were no significant differences between preoperative and postoperative mean cell density, coefficient of variation, or hexagonality. CONCLUSION: Laser in situ keratomileusis caused no damage to the central corneal endothelium. Postoperative improvements in the endothelial cell density and the coefficient of variation in cell size values were related to the discontinuance of contact lens use after surgery.

Subclinical inflammation after laser in situ keratomileusis.

PURPOSE: To determine whether laser in situ keratomileusis (LASIK) for the correction of myopia induces an anterior chamber inflammatory response measurable with laser flare-cell photometry. SETTING: Instituto Oftalmológico de Alicante, University of Alicante. Alicante, Spain. METHODS: Twenty eyes in 20 patients had LASIK to correct myopia ranging from 2.50 to 15.00 diopters (D) (mean -8.94 +/- 3.25 [SD]). Anterior chamber inflammation was measured preoperatively and 1, 3, 7, and 15 days and 1 and 3 months postoperatively using the flare mode of a laser flare-cell meter. All eyes received topical fluorometholone 0.1% drops for 2 weeks postoperatively. RESULTS: Anterior chamber flare values at 1 and 3 days and 1 week postoperatively were not significantly different from those found preoperatively. However, a significant decrease was found at 2 weeks and 1 month (P < .01 and P < .05, respectively). Flare values returned to their preoperative levels at 3 months. No significant correlations between postoperative flare values and depth of ablation were found. CONCLUSION: In this study. LASIK did not induce an inflammatory response in the anterior chamber in the myopic eye.

[New bioadhesive ADAL-1: determination of its tensile strength to join muscle tissue to sclera]. / Nuevo adhesivo ADAL-1: determinación de su fuerza tensil en la unión de tejido muscular y esclera.

PURPOSE: To quantify tensile force to separate the adhesive joint between muscle and sclera obtained by the ADAL-1 adhesive. METHODS: Strabismus surgery including over the Superior Recti was performed. 4 different groups (5 eyes each) were included in this study on New Zealand albino rabbits and lamb eyes. We used Dexon 6/0 suture as control group. We evaluated the tensile force by means of a dynamometer in two periods of time. First, we evaluated just after the adhesion (groups I and II), and after 7 days of the adhesion (groups III and IV). RESULTS: By statistical supported methods SPSS 6.0. The tensile force in group I was: X=1.23 +/- 0.17 Newtons. In group II was X=0.793+/-0.02. In group III the tensile force was: X=1.01+/-0.17 and in group IV was X=0.89+/-0.09 Newtons. There was a significant difference between the two groups: suture and ADAL-l, just immediately after the adhesion. (P=0.004). There was no significant difference between the suture and ADAL-1 adhesive group, one week after the adhesion. CONCLUSIONS: The joint between sclera and muscle by the ADAL-1 adhesive is as resistant as Dexon 6/0 suture group to the traction force one week after surgery.

Retreatment after laser in situ keratomileusis.

OBJECTIVE: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) retreatment for correcting residual myopia. DESIGN: Retrospective noncomparative case series. PARTICIPANTS AND INTERVENTION: Fifty-nine consecutive eyes (43 patients) underwent LASIK retreatment at 3 or 6 months after the primary LASIK procedure. Lifting the corneal flap and reablating the stromal bed with a VISX 20/20 excimer laser was the procedure used for LASIK enhancement. MAIN OUTCOME MEASURES: The following parameters were studied before and after retreatment: visual acuity, refraction, videokeratography, applanation tonometry, and corneal thickness. Complications after LASIK enhancement also were evaluated. Follow-up was 12 months. RESULTS: Before retreatment, only 3.38% of eyes (2 of 59) had an uncorrected visual acuity of 0.5 (20/40) or better, and after retreatment, this percentage increased to 60% (30 of 50) at 6 months and 61.8% (34 of 55) at 12 months. After reoperation, mean best-corrected visual acuity improved by half a line over the values before retreatment. The preretreatment refraction of -2.92 +/- 1.22 diopters (D) (mean +/- standard deviation) decreased significantly to -0.44 +/- 0.80 D at 6 months and to -0.61 +/- 0.82 D at 12 months (P < 0.001). In 82% of eyes (41 of 50) at 6 months and 81.8% (45 of 55) at 12 months, the spherical equivalent was within 1.00 D of emmetropia. There was a significant regression of effect (0.38 D) between 3 and 12 months (P < 0.01). Postretreatment refraction was related to the original refraction before the primary LASIK, the preretreatment refraction, and the ablation diameter used. Although no vision-threatening complications were found, epithelial ingrowth and flap melting were more common after than before LASIK retreatment, with 31% of eyes at 12 months with epithelial ingrowth and 10.9% with flap melting. However, LASIK enhancement improved decentration and night-vision problems. CONCLUSIONS: LASIK retreatment was an effective and predictable procedure for correcting residual myopia. Epithelial ingrowth and flap melting were more frequent after than before LASIK retreatment, whereas decentration and night-vision symptoms improved.

Recovery of corneal nerve morphology following laser in situ keratomileusis.

Morphological changes in the corneal nerves after laser in situ keratomileusis (LASIK) were investigated and the changes were compared with those observed after creation of the keratectomy flap without subsequent photoablation. After creating the hinged flap, a multizone excimer laser photoablation (myopic correction from 6.00 to 6.66 D; diameter 6 mm) was performed on 27 rabbit corneas. Seven of these 27 rabbits received an automated keratectomy without laser photoablation on the fellow eye. A histochemical acetylcholinesterase reaction was used to demonstrate the changes in the morphology of the corneal nerves 3 days, 2.5 and 5 months after the operations. In all specimens the deepest stromal nerve bundles showed normal morphology. Cut nerve trunks were found at the wound margins and at the level of the flap interphase in the stromal bed. At 3 days, both epithelial and basal epithelial/subepithelial nerves were found at the hinge of the flap but the rest of the flap showed a major loss of epithelial, basal epithelial/subepithelial and superficial stromal nerves. A few new regenerating thin nerve fibers were found to emerge from the cut stromal nerve trunks. They appeared to pass the wound margin into the flap area below the epithelium. At 2.5 and 5 months an increasing number of regenerating nerve leashes were observed to emerge from the cut stromal nerve trunks. They appeared to send anastomosing fibers among the neighboring stromal nerves. By this time the epithelial, basal epithelial/subepithelial and anterior stromal innervation had gained an almost normal nerve density and architecture. In the corneas with the flap only, the epithelial innervation was slightly better spared in the center of the flap, and the stromal changes were somewhat less prominent compared with the LASIK corneas.

Nuevo adhesivo Adal-1®: Determinación de su fuerza tensil en la unión de tejido muscular y esclera / New bioadhesive adal-1®: determination of its tensile strength to join muscle tissue to sclera

Objetivo: Medir de forma cuantitativa la fuerza tensil que se debe realizar para separar el músculo unido a esclera mediante el adhesivo ADAL-1®.Métodos: En cirugía de estrabismo, con sección del músculo recto superior. Se han realizado 4 grupos distintos (5 ojos cada uno), utilizando el conejo albino de raza neozelandesa, y ojos de cordero cadáver. Se ha utilizado la sutura Dexon® 6/0 como grupo control. Se ha valorado la fuerza tensil mediante un dinamómetro, en 2 tiempos: 1.º Tiempo inmediato tras la adhesión (grupos I y II), 2.º a los 7 días de la adhesión (grupos III y IV).Resultados: Evaluados mediante el paquete informático SPSS 6.0. El valor medio de la fuerza tensil en el grupo I, fue, de X=1,23ñ0,17 Newtons. En el grupo II una media de X=0,793ñ0,02. En el grupo III, X=1,01ñ0,17, mientras que en el grupo IV, la media fue, de X=0,89ñ0,09 Newtons. Existiendo diferencias estadísticamente significativas entre los grupos I y II, con una P=0,004. No existiendo diferencias estadísticamente significativas entre los grupos III y IV con una P=0,129.Conclusiones: La unión entre la esclera y el músculo realizada con el adhesivo ADAL-1®, es tan resistente a la tracción como la realizada con la sutura Dexon® 6/0 (AU)

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