bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgical Correction of Hyperopia Following Radial Keratotomy
Authors: Damiano Richard E , Forstot S Lance , Dukes Debra K
Published: April 2021

ABSTRACT

Background: No effective treatment for hyperopia following radial keratotomy has been described. A new surgical technique of two purse-string intrastromal sutures was investigated for correction of this hyperopia.

Methods: Eighteen radial keratotomy patients who were unhappy with uncorrected vision and who were unsatisfied with contact lens or spectacle correction, after informed consent, underwent corneal suturing. The 19 hyperopic eyes included 5 original overcorrections, 5 overcorrections after reoperation, and 9 progressive hyperopes. The refractive error ranged from +1.25 to +5.75 diopters spherical equivalent (mean +3.47 D). Presuturing uncorrected visual acuity ranged from 20/50 to 20/400 with 11 eyes (58%) 20/100 or worse.

Results: The follow up after double purse-string suturing averaged 24 months (range, 12 to 47 months). All patients had follow up of at least 1 year; 14 patients (74%) had follow up of 2 years or more. The change in refractive spherical equivalent following surgery averaged -3.30 D (range, -1.00 to -7.50 D). The steepening in average keratometry was 4.10 D (range, 1.00 to 8.00 D). The refraction after suturing averaged -1.12 D (range, +2.50 to -3.50 D). Uncorrected visual acuity after suturing was 20/40 or better in 14 eyes (74%), and 20/50 to 20/80 in 5 eyes (36%). There were no significant intraoperative, early or late postoperative complications. Seventeen eyes were either the same or gained 1 line of acuity; 2 eyes gained 2 lines of acuity; no eyes lost any lines of refractive Snellen acuity.

Conclusions: The placement of two purse-string intrastromal sutures appears to provide significant steepening of the central cornea following excessive flattening after radial keratotomy. The steepening effect appears to remain stable with greater than 1-year follow up. This surgical technique offers an alternative to symptomatic hyperopic postradial keratotomy patients who cannot be corrected with spectacles or contact lenses. (Refract Corneal Surg 1992;8:75-79.)
Suturing in Lamellar Surgery: The BRA-Technique
Authors: Guimaräes Ricardo Q , Rowsey J James , Guimaräes Márcia F Reis , Reis Pedro P Leite , Castro Raul Damásio R , Tirado Breno R
Published: April 2021

ABSTRACT

Background: The principle of refractive corneal lamellar surgery rests on the modification of corneal shape after the removal of a superficial disk with a microkeratome. The 150-µm-thick disk is easily torn, rotated or decentered by the traditional eight-bite running suture, producing irregular astigmatism which is the major cause of visual deficit after these procedures.

Methods: We propose a new suture technique, designated the BRA suture, which we have used in more than 300 cases of various types of refractive corneal lamellar procedures. Based on the overlay concept, the suture is anchored in four points of the nonoperated corneal periphery.

Results: With this technique, the iatrogenic irregular astigmatism induced by the suture has been eliminated and corneal scars significantly reduced. This suture also decreases surgical time, accelerates visual recovery, and increases patient comfort due to its early removal.

Conclusions: We consider this the ideal suture for refractive corneal lamellar surgery due to its effectiveness, simplicity, and safety. (Refract Corneal Surg 1992;8:84-87.)
The PAR Technology Corneal Topography System
Authors: Belin Michael W , Litoff David , Strods Salvins J , Winn Steven S , Smith Richard S
Published: April 2021

ABSTRACT

Background: Computer-assisted videokeratography has emerged as a useful clinical and research tool. All of the currently available commercial units utilize a modified placido disk image and require a smooth reflective surface. The PAR Technology Corneal Topography System (PAR CTS) is a prototype of a new computer-assisted corneal imaging device. The system produces a true topographic map (elevation map) by analyzing a projected grid on the corneal surface, as opposed to a placido disk reflection, and utilizes the technique of raster photogrammetry to define elevation points on the corneal surface. Because the system defines elevation points, not curvature, mathematical modeling is easily accomplished. Current software displays include a true topographic map, a spherical subtraction map in both relative and absolute scales, and a meridian analysis that is adapted to display refractive photoablative surgery.

Methods: We evaluated the accuracy of this device by analyzing three calibrated test spheres (55.76, 42.21, and 33.55 diopters). The test spheres were steel balls coated with a thin white silicone polyester coating that was necessary for grid projection. The test spheres were measured by a Taylor-Hobson contact profilometer possessing submicron accuracy. To determine the reproducibility of the system, three investigators measured three noncalibrated balls (20 mm, 18 mm, and 12 mm). The optical system was purposely decentered and refocused after each reading.

Results: Utilizing the CTS custom optics, system accuracy at the 8-millimeter test area was 0.03 (SD 0.03), 0.00, (SD 0.02), and 0.07 (SD 0.01) D respectively. Smaller diameter test areas resulted in a predicted loss of accuracy. Maximum intraobserver variability was 0.09, 0.06, and 0.11 D respectively, and maximum interobserver variability measured 0.18, 0.12, and 0.16 D.

Conclusions: These data demonstrate that the PAR CTS is both highly accurate and reproducible in determining topography of spheres that approximate the curvature of the human cornea. (Refract Corneal Surg 1992;8:88-96.)
Introduction to Biomechanics of the Cornea
Authors: Buzard Kurt A
Published: April 2021

ABSTRACT

Background: As refractive procedures involving the cornea have proliferated, concerns over the long-term stability and predictability of these procedures have occupied a more prominent role.

Methods: Procedures and principles of mechanical engineering to mathematically model the cornea can provide valuable insight into the biomechanics of the cornea, and this approach can be used to predict corneal behavior. In order to utilize these advanced methods, some basic knowledge concerning limitations, assumptions, and techniques regarding the finite element method is needed. The principles of mechanical measurement of deformable bodies are discussed, as are the quantities stress, strain, Poisson's ratio, and creep as they are measured and used in the modeling of biologic systems. The finite element modeling procedure is discussed in a simplified geometric system.

Conclusions: While work remains to be done in this area, it is seen that useful and predictive models can be created which significantly improve our understanding and predictability of corneal procedures. (Refract Corneal Surg 1992;8:127-138.)
Computer Simulation of Arcuate Keratotomy for Astigmatism
Authors: Hanna Khalil D , Jouve Francois E , Waring George O , Ciarlet Philippe G
Published: April 2021

ABSTRACT

Background: The development of refractive corneal surgery involves numerous attempts to isolate the effect of individual factors on surgical outcome. Computer simulation of refractive keratotomy allows the surgeon to alter variables of the technique and to isolate the effect of specific factors independent of other factors, something that cannot easily be done in any of the currently available experimental models.

Methods: We used the finite element numerical method to construct a mathematical model of the eye. The model analyzed stress-strain relationships in the normal corneoscleral shell and after astigmatic surgery. The model made the following assumptions: an axisymmetric eye, an idealized aspheric anterior corneal surface, transversal isotropy of the cornea, nonlinear strain tensor for large displacements, and near incompressibility of the corneoscleral shell. The eye was assumed to be fixed at the level of the optic nerve. The model described the acute elastic response of the eye to corneal surgery.

Results: We analyzed the effect of paired transverse arcuate corneal incisions for the correction of astigmatism. We evaluated the following incision variables and their effect on change in curvature of the incised and unincised meridians: length (longer, more steepening of unincised meridian), distance from the center of the cornea (farther, less flattening of incised meridian), depth (deeper, more effect), and the initial amount of astigmatism (small effect).

Conclusions: Our finite element computer model gives reasonably accurate information about the relative effects of different surgical variables, and demonstrates the feasibility of using nonlinear, anisotropic assumptions in the construction of such a computer model. Comparison of these computer-generated results to clinically achieved results may help refine the computer model. (Refract Corneal Surg 1992;8:152-163.)
Combined Transverse and Interrupted Radial Keratotomy for Compound Myopic Astigmatism
Authors: Lipshitz Isaac , Mayron Yoram , Loewenstein Anat
Published: April 2021

ABSTRACT

BACKGROUND: A variety of patterns of keratotomy are used to correct naturally occurring astigmatism. We evaluated straight transverse incisions with interrupted radial incisions (jump radiais).

METHODS: In 32 human eyes with naturally occurring astigmatism, we used straight transverse incisions with interrupted radial incisions, with or without additional radial keratotomy, to correct compound myopic astigmatism. The range of preoperative refractive astigmatism was 1.00 to 3.50 D.

RESULTS: The mean follow-up time was 15 months (range, 12 to 16 months). The average surgically corrected astigmatism was 1 .55 ± 0.29 D. Eightyseven percent of the eyes achieved less than 1 .00 D of astigmatism, and the remaining four eyes retained 1 .00 to 1 .25 D of astigmatism.

CONCLUSION: Combined transverse and interrupted radial incisions are effective in correcting naturally occurring astigmatism. [Refract Corneal Surg 1992;8:280-285.)

RÉSUMÉ

INTRODUCTION. Différentes variétés de kératotomie ont été utilisées dans le traitement de l'astigmatisme myopique congénital. Nous avons évalué l'effet des incisions transverses associées à des incisions radiaires discontinues.

METHODES. Nous avons réalisé des incisions transverses droites associées à des incisions radiaires discontinues dan le traitement de l'astigmatisme congenital de 32 yeux. Des incisions radiaires transverses ont été réalisées si nécessaire pour traiter l'élément myopique de l'astigmatisme.

RESULTATS. Le recul moyen était de 15 mois (12 à 18 mois). La correction chirurgicale de l'astigmatisme était de 1.55 ± 0.29 D. 87% des yeux étaient corrigés à moins de 1 .00 D, seuls 4 yeux étaient entre 1.00 et 1.25 D.

CONCLUSION. L'association incision radiaire discontinue et transverse est efficace dans la correction de l'astigmatisme congénital. (Translated by Jean Marc Legeais, MD, Paris, France.)

SOMMARIO

PREMESSA. Una varietà di modelli di cheratotomia sono usati per correggere l'astigmatismo congenito (primario); noi abbiamo valutato le incisioni rette trasverse con incisioni radiali interrotte (radiali a salto).

METODI. In 32 occhi con astigmatismo congenito abbiamo usato le incisioni rette trasverse con incisioni radiali interrotte con o senza tagli radiali addizionali per correggere astigmatismo miopico composto. L'estensione dell'astigmatismo preoperatorio era fra 1 .00 a 3.50 diotric.

RESULTATI. Il follow up medio era di 15 mesi (da un minimo di 12 ad un massimo di 18 mesi). L'astigmatismo medio corretto chirurgicamente era 1 .55 ± 0.29 D. L'87% degli occhi ha ottenuto meno di 1 .00 D di astigmatism ed il rimanente 4 occhi ha mantenuto da 1 .00 a 1 .23 D di astigmatismo.

CONCLUSIONI. Le incisioni trasverse combinate alle radiali interrotte sono efficaci nel correggere l'astigmatismo congenito. (Translated by Lucio Buratto, MD, Milan, Italy.)
A Granny-Style Slip Knot for Use in Eye Surgery
Authors: Harris David J , Waring George O
Published: April 2021

ABSTRACT

An adjustable knot for use in ocular surgery is described herein. The first part of the knot is a granny knot, which allows tension to be adjusted. The advantages of this knot are: 1 ) ease of tying; 2) adjustability; and 3) small size of the knot. [Refract Corneal Surg 1992;8:396-398.)
Intrastromal Photorefractive Keratectomy With a New Optically Coupled Laser Probe
Authors: Taboada J , Poirier Robert H , Yee R W , Tio F O
Published: April 2021

ABSTRACT

BACKGROUND: Intrastromal photorefractive keratectomy is a new procedure in which compact linear or area regions of the corneal stroma can be vacuolized, yielding changes in corneal curvature.

METHODS: Diffraction-limited 1064- nanometer light pulses from a high rep rate Q-switched NdYAG laser were coupled through novel means into a probe with index-matched optical contact with the cornea. The resulting extremely reduced focal region initiated a plasma point that was free of shock front effects where tissue was reduced to liquid. This probe process was applied to the corneas of eye-bank eyes, and to living rabbit and primate eyes. The refractive effects were evaluated with slit-lamp microscopy, keratoscopy, light and electron microscopy.

RESULTS: Refractive effects similar to refractive keratotomy were observed immediately after treatment. Intrastromal highly localized vacuolized regions were observed at the depth of focus with variability of only 20 µm. The plasma point vacuoles were about 100 pm in diameter. Stromal material that occupied the vacuole space appeared completely reduced to liquid. The transition region between vacuole and normal tissue was less than 0.5 µm. The treatment vacuoles disappeared to the unaided eye 24 to 48 hours after treatment.

CONCLUSIONS: Corneal refractive power can be achieved with intrastromal keratectomy. (Refract Corneal Surg 1992;8:399-402.)
Iowa PK Press for Donor Corneas-A Comparative Study of Donor Corneal Shape
Authors: Vrabec Michael P , Krachmer Jay H , Florakis George J
Published: April 2021

ABSTRACT

BACKGROUND: A new cornea press for cutting donor corneal buttons from the endothelial side, the Iowa PK Press, is described. Major modifications of the Bourne Press include a springactivated piston without lateral sway, a centering device for a Teflon® cutting pad, and the ability to accommodate a wider range of trephine sizes (6.2 mm to 10.0 mm).

METHODS: The Iowa PK Press was compared with the Bourne Corneal Press and trephination by hand in a series of 15 donor cornea trephinations. Measurements taken from photographs of the buttons included endothelial diameter, epithelial diameter, and edge angles.

RESULTS: The Iowa PK press cut buttons that had a slightly larger epithelial and endothelial diameter when compared to hand trephination (p < .05, analysis of variance) with less undercutting of the endothelial surface. There was no statistically significant difference in epithelial and endothelial diameters, eccentricity, or edge angles between the two presses.

CONCLUSIONS: The Iowa PK Press is more versatile than the Bourne Press in terms of the potential range of diameter of corneal buttons that can be created. [Refract Corneal Surg 1992;8:475-477.)

RESUME

INTRODUCTION: Une nouvelle presse de la cornée servant à couper les greffons cornéens du côté endotheliale est décrit. D'importants modifications ont été apportées à la presse selon Bourne, mensionnons notamment le piston à ressort sans balacement latéral, l'appareil à centrer pour coussinet à couper en Teflon®, et la possibilité d'une plus grande variation de la taille de trépans (6.2 mm à 10.0 mm).

MÉTHODES: La presse à greffe transfixiante selon Iowa fut comparée à la presse cornéenne de Bourne et à la trépanation à main levée en 15 trépanations de cornées données. Plusieurs mesures dont celles du diamètre endothelial, du diamètre epithelial, de l'angle du bord du bouton ont été prises à partir de photos de greffons.

RÉSULTATS: La presse à greffe transfixante d'Iowa permettait d'obtenir des greffons à diamètres épithéliaux plus grands que ceux trépanés à la main (p < .5 analyse de variance) et ce, en minant moins la surface endotheliale. La comparaison entre les deux presses n'a pas démontré des différences statistiquement significatives en ce qui a trait au diamètre endothelial ou epithelial, à l'excentricité, et à l'angle du bord du greffon.

CONCLUSION: La variation des diamètres des grefoons cornéens nous permet de constater que la presse à greffe transfixiante selon Iowa, est plus souple que la presse salon Bourne.

SOMMARIO

PREMESSA: Viene descritto un nuovo trapano corneale per donatore, lo "Iowa PK Press," per tagliare il lembo IaIIa parte endoteliale. Le maggiori modifiche rispetto al "Bourne Press" consistono in un pistone attivato da una spirale privo di movimenti di lateralìtà, un sistema di centraggio per una superficie d'appoggio in Teflon® e la possibilità di utilizzare un più ampio range di dimensioni del trapano (da 6.2 mm a 10.0 mm).
Long-Term Endothelial Cell Loss Following Phacoemulsification: Model for Evaluating Endothelial Damage After Intraocular Surgery
Authors: Werblin Theodore P
Published: April 2021

ABSTRACT

BACKGROUND: Newer concepts of phakic intraocular lens (IOL) surgery present concerns as to their long-term deleterious effect on the endothelium. We examine the behavior of the endothelium for up to 6 years following uneventful phacoemulsification surgery, to establish a baseline for what might be an acceptable level of endothelial cell loss due to intraocular surgical trauma.

METHODS: Ninety-three eyes undergoing phacoemulsification surgery who had multiple endothelial specular microscopy examinations for up to 6 years were examined. Central endothelial specular photomicrographs were analyzed in all cases and the percent of endothelial cell loss as a function of time was calculated. Cell density calculations were corrected for the normal endothelial cell loss as a function of age.

RESULTS: Routine uncomplicated phacoemulsification surgery demonstrated a 9% endothelial cell loss 1 year postoperatively. This is in marked contrast to the 16% average endothelial cell loss cited in the literature after phakic AC-IOL surgery. In general, anterior chamber IOL surgery following cataract removal compares unfavorably to posterior chamber IOL insertion long term (20% cell loss versus 12% cell loss).

CONCLUSIONS: A model is proposed to look at the rate of endothelial cell loss that would be significant enough to create the threat for corneal edema long term following refractive intraocular surgery in young patients. Suggestions for critical comparisons between the observed endothelial aging seen with phakic IOLs and values for more routine IOL surgery are proposed to predict the long-term threat for endothelial cell loss and corneal decompensation, which might result many years after phakic refractive IOL surgery. [Refract Corneal Surg 1993;9:29-35.)

RÉSUMÉ

INTRODUCTION: Les effets secondaires endothéliaux suivant l'implantation de lentille infraoculaire chez les yeux phaques méritent consideration. Afin d'établir un niveau passable de perte de !'endothelium suivant la chirurgie intra-oculaire, nous avons suivi à long échéance l'endothelium apès la phacoemulsification noncompliquée.

METHODES: Nous avons examiné 93 patients qui ont subi la phacoemulsification et qui ont subi de nombreuses examens à la microscopic speculate jusqu'à 6 ans post-opératoire. Les photos de la microscopie speculaire de !'endothelium centrale furent analysés dans tous les cas et le pourcentage de perte des cellules endotheliales avec le temps fut calculé. Les calculations furent corrigées avec la perte normale des cellules en fonction du viellissement.

RÉSULTATS: Nous avons observé la perte de 9% des cellules endotheliales 1 année après la phacoemulsification noncompliquée, par contraste au chiffre publiée de 16% après l'implantation de LIO chez les yeux phaques. On a observé une perte de 20% après l'implantation de LIO dans la chambre antérieure suivant l'extraction de cataracte, par contraste à 12% avec une lentille postérieure.
Multifocal Effect of Against-the-Rule Myopic Astigmatism in Pseudophakic Eyes
Authors: Verzella Franco , Calossi Antonio
Published: April 2021

ABSTRACT

BACKGROUND: In monofocal intraocular lens (IOL) implants we can sometimes obtain a certain degree of pseudoaccommodation. The use of a slight myopic astigmatism is proposed for postoperative refraction to achieve a significant increase in the depth of field and to reestablish a certain degree of pseudoaccommodation in Pseudophakie eyes.

METHODS: Eighty-one eyes with against-therule myopic astigmatism were evaluated in 50 patients who underwent IOL implant surgery. We selected patients with corrected monocular visual acuity greater than or equal to 20/30 and with a refraction ranging from + 0.50 to - 1 .25 diopters sph, from -0.50 to -2.75 D cyl, ax from 55° to 140°.

RESULTS: Monocular uncorrected distance visual acuity in 68% of eyes was 20/40 or better, while binocular uncorrected distance visual acuity in 84% of eyes was 20/40 or better and in 66% of eyes was 20/30 or better. Monocular uncorrected near visual acuity in 67% of eyes was J3 or better, while binocular uncorrected near visual acuity in 82% of eyes was J3 or better and in 68% was J2 or better.

Sixty-four percent of patients never wear glasses for distance, while 34% use them occasionally and only 2% always wear them.

Fifty-four percent of patients never wear glasses for near, 32% use them occasionally, while 14% always wear them.

CONCLUSION: These data show that with a low against-the-rule simple myopic astigmatism (about -1.50 D cyl x 90) we can often offer Pseudophakie patients a rewarding independence from glasses both for distant and near vision. (Refract Corneal Surg 1993;9:58-61.)

RÉSUMÉ

INTRODUCTION: Avec la lentille intraoculalre monofocal nous pouvons parfois observer un certain degré de pseudoaccommodation. Nous proposons l'utilisation d'un faible astigmatisme myopique en réfraction postopératoire afin d'augmenter le profondeur de champ et d'établir une certaine pseudoaccommodation chez les yeux pseudophakes.

MÉTHODES: Nous avons évalué 81 oeils avec astigmatisme inverse chez 50 patients qui avaient subi l'implantation d'une lentille intraoculaire (LIO). Nous avons choisi les patients avec une acuité visuelle monoculaire corrigée d'au moins 20/30 (6.7/ 10e), et avec une réfraction sphérique variant entre + 0.50 et - 1 .25 D, une réfraction cylindrique variant entre -0.50 et -2.75 D, et axiqle variant entre 55° et 140°.

RÉSULTATS: L'acuité visuelle monoculaire noncorrigée de loin dans 68% des cas fut d'au moins 20/40 (5/ 10e) tandis que l'acuité binoculaire noncorrigée de loin dans 84% des cas fut d'au moins 20/40 (5/ 10e) et dans 66% des cas fut d'au moins 20/30 (6.7/ 10e). L'acuité visuelle monoculaire de près et non-corrigée dans 67% des cas fut d'au moins J3, tandis que l'acuité visuelle binoculaire de près et non-corrigée dans 82% des cas fut d'au moins J3 et dans 68% des cas fut d'au moins J2.

64% des patients ne portent jamais des lunettes pour voir de loin, tandis que 34% en portent à l'occasion et seulement 2% en portent continuellement.
Achromobacter Xylosoxidans Keratitis Following Penetrating Keratoplasty
Authors: Siganos Dimitrios S , Tselentis Ioannis G , Papatzanaki Maria E , Tsilimbaris Miltiadis K , Pallikaris Ioannis G
Published: April 2021

ABSTRACT

BACKGROUND: Achromobacter xylosoxidans is a bacterium not previously reported in a corneal infection. We present a case of infectious keratitis caused by this organism, occurring 1 month following penetrating keratoplasty.

METHODS: Identification of the organism was accomplished by staining, culture, and sensitivity testing of the corneal scraping obtained from the involved area. The infection responded to subconjunctival ticarcillin, piperacillin eye drops, and I.V. azlocillin.

RESULTS: Complete healing with a resultant corneal opacity involving mostly the anterior and middle stroma was achieved 1 month later.

CONCLUSIONS: A. xylosoxidans should be considered as a potential pathogen in instances of early postkeratoplasty infectious keratitis. [Refract Corneal Surg 1992;8;71-73.)
Cryolathe Keratomileusis for Correction of Myopia of 4.00 to 8.00 Diopters
Authors: Polit Fernando , Ibrahim Osama , El Maghraby Akef , Salah Tarek
Published: April 2021

ABSTRACT

BACKGROUND: During the last decade, new refractive surgery procedures have been introduced; older techniques have been modified or even abandoned. Cryolathe myopic keratomileusis has been in clinical use for approximately 30 years. In this retrospective study, we present our experience in applying this technique for the correction of 4.00 to 6.00 diopters of myopia.

METHODS: Autoplastic cryolathe keratomileusis was performed on 61 eyes of 44 patients who were at least 18 years of age, with a preoperative myopia of 8.00 D or less, and 4.00 D or less of astigmatism. The surgical technique used the Barraquer microkeratome and cryolathe. The mean postoperative observation period was 28 months (range, 12 to 73 months).

RESULTS: The mean preoperative spherical equivalent refraction was -5.95 ± 1.14 D (range, -4.25 to -8.00 D). After a mean follow up of 28 months, the mean postoperative spherical equivalent refraction was -0.91 ± 1.49 D (range, +2.00 to -7.75 D). At the end of follow up, 37 eyes (60.7%) were within ±1.00 D of emmetropia and 44 eyes (72.1%) achieved 20/40 or better uncorrected visual acuity. Complications included corneal ectasia in one eye (1.6%) and epithelial inclusions of the interface in another eye (1.6%). Irregular astigmatism was not a major problem, occurring in only two eyes (3.3%).

CONCLUSIONS: Cryolathe keratomileusis is a proven and feasible technique for correcting moderate to high amounts of myopia in properly selected patients; there is a low incidence of vision -threatening complications. Refract Corneal Surg 1993;9:259-267.)

RÉSUMÉ

INTRODUCTION: Pendant la dernière décade de nouvelles chirurgies réfractives ont été introduites; les méthodes précédentes ont été modifiées ou abandonnées. Le keratomileusis myopique reste parmi les techniques opératoires qui ont duré pendant des années. Dans cette étude rétrospective nous présentons notre expérience avec cette technique pour correction de la myopie entre quatre et huit dioptries.

MÉTHODES: Le keratomileusis autoplastique au cryo-tour fut réalisé sur 61 yeux de 44 patients âgés d'au moins 18 ans et affectés d'une myopie préopératoire jusqu'à 8,00 dioptries avec astigmatisme égale ou inférieur à 4,00 dioptries. Il s'agit du microkératome de Barraquer et le cryo-tour. Le suivi post- opératoire moyen fut de 28 mois (écarts 12 à 73 mois).

RÉSULTATS: Le moyen équivalent sphérique de la réfraction préopératoire fut -5,95 ± 1,14 D (écarts -4,25 à -8,00). Après le suivi postopératoire moyen de 28 mois l'équivalent sphérique fut -0,91 ± -1,49 D (écarts +2,00 à -7,75 D). Finalement, 37 yeux (60,7%) étaient entre ± 1,00 D de l'emmetropie et 44 yeux (72.1%) ont réalisés une meilleure acuité visuelle noncorrigée d'au moins 20/40. Les complications comprenaient l'ectasie cornéene chez un oeil (1 ,6%) et les inclusions epitheliales dans l'interface chez un autre (1,6%). L'astigmatisme irregulier n'était pas un grand problème, arrivant chez seulement deux yeux (3,3%).
Topical Diclofenac in the Treatment of Ocular Pain After Excimer Photorefractive Keratectomy
Authors: Sher Neal A , Frantz Jonathan M , Talley Audrey , Parker Paula , Lane Steven S , Ostrov Charles , Carpel Emmett , Doughman Donald , DeMarchi Janet , Lindstrom Richard
Published: April 2021

ABSTRACT

BACKGROUND: Following excimer laser photorefractive keratectomy, patients experience significant ocular pain until corneal reepithelialization. Despite the use of cold compresses, bandage soft contact lenses, cycloplegics, narcotics, and topical corticosteroids, the pain has not been adequately controlled in many patients.

METHODS: A randomized, double-masked, parallel-group study of diclofenac sodium 0.1% ophthalmic solution and its placebo vehicle was evaluated. Patients undergoing excimer myopic photorefractive keratectomy on their second eye were admitted overnight. Postoperative procedures included two drops of diclofenac or placebo immediately after surgery and then qid until reepithelialization, topical tobramycin (qid), 0.1% fluorometholone (q2h), cycloplegics, and a disposable soft contact lens. Thirty-two patients (diclofenac= 16, placebo= 16) were evaluated from + 30 minutes to +96 hours by several types of questionnaires.

RESULTS: Most patients who received placebo experienced pain, starting within 1 hour, peaking at 4 to 6 hours and lasting 36 to 48 hours. The diclofenac-treated patients rarely experienced the early peak in pain, had less pain overall until 72 hours postoperatively, and experienced significantly less photophobia and burning/stinging. Significantly fewer patients on diclofenac required oral narcotics. Three patients (diclofenac =2, placebo= 1) developed corneal infiltrates, the etiology of which is not known. In a separate study we conducted, there was no difference in epithelial healing times between the diclofenac-treated eyes and those not receiving the drug.

CONCLUSIONS: Diclofenac appears to significantly reduce the ocular pain following excimer photorefractive keratectomy. (Refract Corneal Surg. 1993;9:425-436.)

RÉSUMÉ

INTRODUCTION: Les patients éprouvent une douleur oculaire significative après la kératectomie photorefractive au laser excimer jusqu'à la ré-epithélialisation cornéenne. Malgré l'emploi de compresses froides, le port de lentilles de contact, la cycloplégle, l'utilisation de narcotiques, et de corticoïdes, la douleur ne fut pas contrôlée chez un grand nombre de patients.
Time-Delayed, Two-Step Excimer Laser Photorefractive Keratectomy to Correct High Myopia
Authors: Förster Werner
Published: April 2021

ABSTRACT

BACKGROUND: Besides scarring, undercorrection is an important complication of photorefractive keratectomy in myopes over 10.00 diopters.

METHODS: We performed a two-step, timedelayed photorefractive keratectomy with two different ablation zone diameters in a 24-year-old female with amblyopia to correct a total myopic refraction error of - 10.75 D. In the first session, a simple myopic correction of -6.50 D with a 5millimeter ablation zone was performed, and 6 months later, a second myopic correction of -4.00 D with a 6.5-millimeter ablation zone was performed.

RESULTS: Four months after the second photorefractive keratectomy with an ablation zone of 6.5 mm, the refraction was +0.75 - 2.25 × 40° and stayed constant for 2 more months. After the second treatment, an initial increase in corneal haze was seen, but after 4 months, the corneal haze did not exceed the status before the second treatment.

CONCLUSION: A planned two-step, timedelayed photorefractive keratectomy with a larger second ablation zone is a possible approach to overcoming the problem of undercorrection and regression in high myopia. (Refract Corneal Surg. 1993;9:465-467.)
Intrastromal Corneal Ring: 12-month Sighted Myopic Eyes
Authors: Nosé Walton , Neves Renato A , Burris Terry E , Schanzlin David J , Belfort Rubens
Published: April 2021

ABSTRACT

BACKGROUND: To evaluate the efficacy, predictability, and stability of the refractive effect produced by the Intrastromal Corneal Ring (ICR®), the authors completed a 12-month study on 10 myopic eyes.

METHODS: Ten patients with preoperative refractive errors ranging from -2.63 diopters (D) to -4.25 D (mean, -3.30 D) participated in the study. The attempted correction was -2.50 D for a 7.0-mm diameter, 0.3-mm thick ICR. One eye of each patient received an ICR.

RESULTS: The average change in spherical equivalent at 12 months was -2.25 D (SD 0.54 D; range, -1.62 to -3.25 D). All patients maintained a spectacle-corrected visual acuity of 20/20 or better during the 12-month study period, with the exception of patient no. 6 who saw 20/30 at the 6-month examination. Her spectacle-corrected visual acuity returned to 20/20 a few days after the ICR was explanted and remained stable throughout the study. Uncorrected visual acuity had improved to 20/40 or better in all patients on postoperative day 1 and remained in this range for the 9 eyes (90%) during the 12 months of follow up. At postoperative month 12, 9 of 9 eyes (100%) had an uncorrected visual acuity of 20/40 or better with 3 of 9 eyes (33%) seeing 20/20 or better. The remaining patient, no. 6, experienced a tear in Descemet's membrane during the procedure and required explantation of the ring after 6 months due to induced astigmatism and deterioration of uncorrected visual acuity. Two patients developed infiltrates that resolved with the use of antibiotics. The most common postoperative ocular findings were peripheral corneal haze in all eyes that diminished over time, minute lamellar channel deposits (7 of 10 eyes, 70%), deep stromal neovascularization (5 of 10 eyes, 50%), and pannus (5 of 10 eyes, 50%).

CONCLUSION: This preliminary study shows that implantation of an intrastromal corneal ring of this dimension (0.3-mm thick) can reduce approximately 1.50 to 3.00 D of myopia and maintain spectacle-corrected visual acuity. [J Refract Surg. 1996;12:20-28.]
Comparison of 5-mm and 6-mm Ablation Zones in Photorefractive Keratectomy for Myopia
Authors: Kalski Richard S , Sutton Gerard , Bin Yu , Lawless Michael A , Rogers Christopher
Published: April 2021

ABSTRACT

BACKGROUND: Variation in ablation zone diameter may alter visual acuity and/or refractive effect in photorefractive keratectomy. Despite theoretical benefits of using a smaller diameter ablation zone, clinical studies suggest that a larger ablation zone may decrease problems associated with photorefractive keratectomy.

METHODS: The results of our initial 34 consecutive eyes treated with a 5-mm diameter ablation zone using a Summit Technology ExciMed UV200LA excimer laser were compared retrospectively to our initial 34 consecutive eyes treated with a 6-mm diameter ablation zone using a Summit OmniMed excimer laser. Eyes had a spherical equivalent refraction between -1.00 and -6.00 diopters (D) and astigmatism less than 1.00 D. Patients were followed for a minimum of 6 months.

RESULTS: Eyes treated with a 6-mm ablation zone had less hyperopia and a spherical equivalent refraction closer to emmetropia at 1, 2, and 3 months (P=0.001). Eyes treated with a 6-mm ablation zone had better uncorrected visual acuity at 1 and 2 months (P=0.001). Less subepithelial haze was noted at 2 months (P=0.01) and 3 months (P=0.002) in the 6-mm group. At 6 months postoperatively, 30 of 32 eyes (94%) treated with a 6-mm ablation zone had a spherical equivalent refraction within 0.50 D of emmetropia, and all 32 eyes (100%) were within 1.00 D of emmetropia; in the 5-mm ablation zone group, 28 of 34 eyes (80%) were within 0.50 D and 29 (85%) were within 1.00 D of emmetropia. Patients treated with a 6-mm ablation zone complained less of night halos and had fewer differences between night and day vision.

CONCLUSIONS: In this study of myopia of -1.00 D to -6.00 D, eyes treated with a 6-mm ablation zone achieve a more rapid visual recovery with less variation in refractive outcome and less adverse effects than those treated with a 5-mm ablation zone. [J Refract Surg. 1996;12:61-67.]
Comparison of the Standard Combined (Bidirectional) Radial Keratotomy Technique With the Undercut Technique in Human Donor Eyes
Authors: Parks Ross , Quantock Andrew J , Assil Kerry K
Published: April 2021

ABSTRACT

BACKGROUND: We evaluated the efficacy of a new radial keratotomy technique, using a diamond designed to undermine the central clear zone without incising superficial stroma.

METHODS: An 8-incision radial keratotomy at a 3-mm central clear zone was performed on nine pairs of human donor globes. One eye of each pair was incised using the standard combined (bidirectional) technique diamond and the contralateral eye, using the undercut bidirectional technique diamond. Paired t-tests were used to compare changes in central corneal curvature between these two groups. Microscopic analysis of incision morphology was performed on four eyes.

RESULTS: Corneal topography at the 1-, 3-, and 5-mm annular zones revealed corneal flattening of 7.70 ± 1.50 diopters (D), 6.70 ± 1.30 D, and 5.10 ± 1.00 D, respectively, in the undercut bidirectional technique group versus 6.20 ± 1.70 D, 5.30 ± 1.50 D, and 4.00 ± 1.20 D, respectively, in the standard bidirectional technique group (P <0.01 for each annular zone). Light microscopy (serial sections) revealed an average incision depth of 80.9 ± 3.9% in the undercut bidirectional technique group versus 72.7 ± 4.5% in the combined group (P <0.01). The undercut bidirectional technique incisions undermined the central clear zone for a distance of approximately 350 µm compared to about 140 µm for the standard bidirectional incisions.

CONCLUSIONS: In the human cadaver eye, the undercut technique of radial keratotomy provided greater flattening than the standard bidirectional technique. The greater amount of flattening may result from greater central extension of the undercut incisions beneath the central clear zone, from greater incision depth, or from a combination of both factors. [J Refract Surg. 1996;12:77-85.]
Bacterial Keratitis Following Phototherapeutic Keratectomy
Authors: Al-Rajhi Ali A , Wagoner Michael D , Badr Ihsan A , Al-Saif Abdulrazzaq , Mahmood Muneera
Published: April 2021

ABSTRACT

BACKGROUND: Phototherapeutic keratectomy (PTK) is effective in the treatment of many superficial corneal disorders. The incidence of bacterial keratitis following PTK has not been assessed in a large, prospective clinical trial.

METHODS: We report three cases of bacterial keratitis that occurred in a prospective study of 258 consecutive PTK procedures at King Khaled Eye Specialist Hospital.

RESULTS: Three (1.2%) of 258 eyes developed bacterial keratitis during a period of follow up ranging from 1 to 24 months. All three cases were in 183 eyes (1.6%) with a diagnosis of climatic droplet keratopathy, while no cases were observed in 75 eyes with other anterior corneal disorders. Gram-positive species (Streptococcus pneumonia in two, coagulase-negative Staphylococcus in one) were the predominant species isolated from all three cases. Two of the cases were polybacterial. The final visual outcomes ranged from 20/125 to 20/400.

CONCLUSIONS: The risk of bacterial keratitis following treatment of superficial corneal disorders with PTK is low but its occurrence may adversely affect the final visual outcome. [J Refract Surg. 1996;12:123-127.]
Communicating With Keratography
Authors: Grimm Bradford B
Published: April 2021

ABSTRACT

BACKGROUND: Videokeratographic images are important in understanding the corneal topographic changes made by refractive surgery. These images are often poorly presented and cluttered with unnecessary, distracting information.

METHODS: A simple method for producing better quality keratographic images, using the Computed Anatomy TMS-1 instrument and an IBM-compatible computer running Microsoft PowerPoint, is described. Scaling of the color-coded dioptric steps after refractive surgery is discussed.

RESULTS: This method yields a high-quality image, suitable for presentation or publication, and displays the corneal topography clearly and concisely.

CONCLUSION: High-quality videokeratographic images can be easily produced by computer. Modification of the image with better scaling and masking of unnecessary information enhances understanding of corneal topography. [J Refract Surg. 1996;12:156-159.]
Hyperopic Shift and Myopic Regression in a Patient 7 Years After Bilateral Refractive Keratotomy
Authors: Chavez Salvador , Celikkol Leyla , Feldman Sandy T
Published: April 2021

ABSTRACT

PURPOSE/METHODS: To report a patient who developed hyperopic progression in one eye and myopic regression in the other eye following bilateral, non-simultaneous refractive keratotomy.

RESULTS: Uncorrected visual acuity improved to 20/25 and 20/25-2 in the right and left eyes, respectively, 3 months following refractive keratotomy (one procedure in the right eye, two procedures in the left eye). The visual acuity was not stable over time and almost 8 years after surgery, uncorrected distance visual acuity was 20/40- and 20/200. The spherical equivalent refraction of the right eye progressed from -0.50 diopter (D) 3 months after surgery to +1.25 D several years later. The left eye regressed from a spherical equivalent refraction of -0.75 D 3 months after the second surgery to -2.50 D more than 7 years postoperatively. Slit-lamp microscopy disclosed deeper, opaque incisions in the hyperopic eye, and shallower and more transparent incisions in the myopic eye.

CONCLUSIONS: The shift toward hyperopia and myopia in an individual suggest that instability of the radial keratotomy wound may be related to local wound healing events that are, in part, related to incision depth. [J Refract Surg. 1996;12:160-162.]
Photorefractive Keratectomy Following Radial Keratotomy
Authors: Burnstein Yochanan , Hersh Peter S
Published: April 2021

ABSTRACT

BACKGROUND: Excimer laser photorefractive keratectomy (PRK) has been used to correct residual myopia in eyes that have had refractive keratotomy.

METHODS: Nine eyes of eight patients were studied at a mean of 13 months after PRK. Previous procedures included radial keratotomy (9 eyes) and myopic keratomileusis (1 eye). PRK was performed using a Summit Technology excimer laser with a 5.0-mm diameter ablation zone.

RESULTS: Uncorrected visual acuity improved in 7 of 9 eyes. The refractive outcome was within 1.00 diopter (D) of attempted correction for 3 of 9 eyes. Spectacle-corrected visual acuity decreased 2 or more Snellen lines in 2 of 9 eyes. Subepithelial corneal stromal haze was seen 1 month postoperatively in 6 of 8 eyes and was present in 4 of 6 eyes at 1 year. Stromal haze was associated with regression of the refractive effect of the PRK.

CONCLUSIONS: PRK in eyes with previous radial keratotomy appears to be less predictable and may be associated with greater corneal haze and regression of refractive correction than in previously unoperated eyes. Activation of stromal fibroblasts in the previous corneal incisions may cause these findings. [J Refract Surg. 1996;12:163-170.]
Cutting the Cornea With a Waterjet Keratome
Authors: Lipshitz Isaac , Bass Rephael , Loewenstein Anat
Published: April 2021

ABSTRACT

BACKGROUND: Waterjet cutting is an advanced technology. It consists of a cutting tool that uses a very thin stream of ultra-high-pressure water forced at high velocity through a very small nozzle, creating a very sharp knife. We report on the first experimental use of waterjet technology to reshape the cornea.

METHODS: The system was used in vitro on 10 bovine eyes, and in vivo on 10 albino rabbit eyes. Using the waterjet keratome (Lipshitz-Bass knife, LBK) lamellar corneal incisions were performed. Histological examinations were performed.

RESULTS: A waterjet stream was found to be capable of incising corneas at relatively low energy levels (4000 PSI). Good surface quality could be obtained, and there was no collateral damage to the remaining portion of the cornea, lens, or retina. In the in vivo experiments, the epithelium healed within 48 hours.

CONCLUSIONS: These preliminary experiments suggest that waterjet technology can be an effective instrument for reshaping the cornea. [J Refract Surg. 1996;12:184-186.]
Mathematical Simulation of Retinal Image Contrast After Photorefractive Keratectomy With a Diaphragm Mask
Authors: Ludwig Klaus , Schäffer Peter , Gross Herbert , Lasser Theo , Kampik Anselm
Published: April 2021

ABSTRACT

BACKGROUND; Photorefractive keratectomy (PRK) using a dilating diaphragm mask engraves a delicate three-dimensional staircase pattern into a formerly smooth corneal surface. The created steps are later smoothed by tear film and wound healing processes. The present study investigates, in a mathematical simulation, the effects that such staircase patterns and their smoothing may have on retinal image contrast.

METHODS: All simulations are based on the Gullstrand eye model and calculate retinal image contrast from point spread function (PSF) analysis of Gullstrand eyes treated by simulated PRK under various conditions.

RESULTS: The simulations indicate that PRK can reduce retinal contrast markedly. The most critical factor for such a reduction is the step height of the ablation pattern. With step heights below 0.4 µm, loss of contrast due to the created staircase pattern is always moderate and should be restored during early wound healing. Complete wound healing may smooth out larger step heights. Micromovements during PRK also can lead to partial loss of retinal image contrast.

CONCLUSIONS: Simulation of retinal contrast after PRK shows that step heights below 0.4 µm seem to be acceptable. A minimization of the micromovements during PRK can offset some of the reduction of retinal contrast. [J Refract Surg. 1996;12:248-253.]
Comparison of Corneal Epithelial Wound Healing After Photorefractive and Lamellar Keratectomy
Authors: Reidy James J , Jacobson Mark S , Thompson Hilary W , Beuerman Roger W , Leach David H , McDonald Marguerite B
Published: April 2021

ABSTRACT

BACKGROUND: The rate of corneal epithelial wound healing may be determined, in part, by the characteristics of the stromal surface. The excimer laser has the ability to produce a highly uniform ablated surface, which may facilitate reepithelialization after photorefractive keratectomy (PRK).

METHODS: The rate of corneal epithelial wound healing after excimer laser PRK was compared with the rate of reepithelialization after manual lamellar keratectomy. Ten rabbits received a 4-mm diameter ablation in one eye (fluence = 160 m J/cm2) and a shallow, 5-mm diameter, manual lamellar keratectomy in the contralateral eye. At 0, 4, 8, 12, 24, 36, 48, 60, and 72 hours after wounding, sodium fluorescein was instilled, and photographs were taken, converted to video images, and digitized. Wound area was calculated for each time point and converted to wound radius; the slopes of the wound radius, plotted over time, were compared to determine rates of healing. Scanning electron microscopy was performed immediately after wounding to examine surface regularity.

RESULTS: By 24 hours after wounding, corneas that had undergone PRK demonstrated a significantly faster rate of epithelial wound healing compared with eyes that underwent lamellar keratectomy (33.4±1.9 um/hr vs 27.8±1.4 um/hr, respectively, for 12 to 72 hours) (p<0.0001). Scanning electron microscopy showed greater stromal surface irregularity in the corneas that had undergone lamellar keratectomy, compared with the laser-ablated corneas.

CONCLUSIONS: This study demonstrates that the rate of epithelial wound healing is significantly faster after excimer laser PRK than after lamellar keratectomy in the rabbit. Variations in surface regularity and wound edge profile may contribute to differences in wound healing. [J Refract Surg. 1996;12:352-357.]