Diamond Blade Research Articles

Radial keratotomy for the purpose of reducing glasses power in high myopia.

Anterior radial keratotomy for high myopia (over-6.25 diopter) to reduce refractive error was not able to dispense with glasses or contact lenses due to the high myopia itself. However patients could see objects well and were free of dizziness while wearing glasses of relatively reduced power. We performed anterior radial keratotomies on 83 high myopic and/or astigmatic eyes of 47 patients at Kangnam St. Mary's Hospital between May 1990 and Mar. 1991. Eight radial incisions with a diamond blade were performed and the Ruiz technique was added for astigmatism of over 2.0 diopters. The depth of incision was 90 to 95% of corneal thickness and the optical zone was 3mm in diameter. Patients were followed up on postoperative 7 days. 1 month, 3 months, 6 months, 1 year and thereafter. Uncorrected visual acuity of 20/40 or better after radial keratotomy could be obtained in 19.6% of high myopic eyes. A mean reduction of the spherical equivalent cycloplegic refraction of 5.13 diopters and a keratometric reading of 3.89 diopters after radial keratotomy were observed. About 90% of patients were satisfied with their visual outcome with reduced refractive power glasses. We recommend radial keratotomy for high myopic patients to reduce the refractive power and to help them enjoy a more comfortable life.

Evolving techniques of cataract surgery: Continuous Curvilinear Capsulorhexis, down-slope sculpting, and nucleofractis.

evelopment of phacoemulsification by Dr D Charles Kelman in the 1960s spawned a new era in extracapsular cataract Since that time, use of phacoemulsification in ophthalmic surgery continues to grow because of its inherent benefits to the patient. The development of the Continuous Curvilinear Capsulorhexis (CCC) technique, “down-slope’’ sculpting, in situ Divide-and-Conquer Nucleofractis (DCN) phacoemulsification, and selfsealing wounds are among the latest advances in small-incision surgery with posterior chamber in-the-bag intraocular lens (IOL) implantation. The growing trend towards a self-sealing wound with an anterior corneal entry technique has had a profound effect on many facets of cataract surgery in recent years. My current technique is a frown-shaped incision with the nearest part approximately 2.5 mm from the conjunctival reflection (Fig 1). A diamond blade is preferred, because it cuts with exquisite sharpness and has less tendency to bunch up the tissue to go too anteriorly or posteriorly. The blade requires very little traction or fixation because it cuts so cleanly and easily. Interestingly, the incision does not require a long internal corneal flap, only one approximately 1.0 mm to 1.5 mm long. If made properly, probably 1 or 2 mm from the trabecular meshwork, a self-sealing wound is easily accom

Three versus four radial keratotomy incisions

Radial keratotomy (RK) is currently performed with four or eight semi-radial incisions. To evaluate the effect of a theoretically more stable three-incision RK pattern, centripetal incisions were made in 16 human donor eyes (eight pairs), using a double-edged diamond blade set to 90% of central pachymetry and a 3.5 mm optical clear zone. Intraocular pressure was maintained at 15 mm Hg during surgery and while keratometry readings were made. One randomly selected eye of each pair had three radial incisions made at 12, 4 and 8 o'clock; the other eye had four radial incisions at 12, 3, 6, and 9 o'clock. Corneal flattening was 6.08 diopters (D) with four incisions and 4.84 D with three incisions (P < .05). Astigmatism increased 0.44 D and 0.69 D, respectively (P>.1). Histologically measured mean incision depth (77.4%) did not differ significantly between the groups (P>.1). This study shows that 80% of the effect of a fourincision RK pattern can be obtained with a theoretically more stable three-incision pattern.

The effects of notch width on the SENB toughness for oxide ceramics

The fracture toughness of a range of oxide ceramics, namely aluminas with various grain sizes, Y 2 O 3 -stabilized tetragonal zirconia polycrystals (Y-TZP), MgO-partially stabilized zirconias (Mg-PSZ) and zirconia-toughened ceramics (ZTC), has been measured by the single edge notch beam (SENB) technique using machined notches of varying widths from 150 to 1800 μm. It was found that the response of each material was critically dependent on its microstructure. Experimental results show that where ‘dynamic’ toughening mechanisms occur, such as transformation toughening, SENB toughness depends strongly on the notch width. For example, the SENB toughness of Y 2 O 3 -stabilized tetragonal zirconia polycrystals and MgO-partially stabilized zirconia ceramics, which are typical of transformation toughened ceramics, increases significantly with increasing notch width when the notch width is less than 1 mm. A further increase in the notch width results in only a slight increase in the SENB toughness. Zirconia-toughened alumina (ZTA) ceramics show similar behaviour, although the increase in SENB toughness is smaller than that for Y-TZP ceramics. The notch width dependence of SENB toughness for the transformation toughened ceramics is related to the transformation zone at the notch tip, induced by diamond blade machining. In contrast, the SENB toughness of alumina ceramics shows very little response to the variation in notch width. A discussion on the relationships between SENB toughness values measured and the operative toughening mechanisms is presented. Die Bruchzähigkeit einer Reihe verschiedener oxidischer Keramiken, nämlich von Aluminiumoxid mit verschiedenen Korngrößen, von polykristallinem Y 2 O 3 -stabilisiertem Zirkoniumoxid (Y-TZP), von MgO-partiell-stabilisiertem Zirkoniumoxid (Mg-PSZ) und von Zirkoniumoxid-verstärkten Keramiken (ZTC) wurde an einseitig gekerbten Biegebruchstäbchen (SENB) gemessen, wobei vorher jeweils verschiedene Kerbweiten von 150 bis 1800 μm eingearbeitet wurden. Es konnte gezeigt werden, daß das Materialverhalten sehr empfindlich vom Gefüge abhängt. Die experimentellen Ergebnisse zeigen, daß für den Fall der ‘dynamischen’ zähigkeitssteigernden Mechanismen, wie zum Beispiel Zähigkeitserhöhung durch Umwandlungen, die Kerbbiegebruchzähigkeit stark von der Kerbweite abhängt. So nimmt die Kerbbiegebruchzähigkeit von polykristallinem Y 2 O 3 -stabilisiertem Zirkoniumoxid und von mittels MgO-partiell-stabilisiertem Zirkoniumoxid, zwei typischen Vertretern für die Zähigkeitssteigerung durch Umwandlung, drastisch mit zunehmender Kerbweite zu, wenn die Kerbweite geringer als 1 mm ist. Eine weitere Vergrößerung der Kerbweite führt nur zu einer geringen Kerbbiegebruchzähigkeitssteigerung. Zirkoniumoxid-verstärktes Aluminiumoxid (ZTA) zeigt ein ähnliches Verhalten, obgleich die Zähigkeitssteigerung geringer ausfällt als für die Y-TZP-Keramiken. La résistance à la fracture d'une série de céramiques à base d'oxydes, comme de l'alumine ayant une taille de grain variable, de la zircone polycristalline tétragonale stabilisée par Y 2 O 3 (Y-TZP), de la zircone stabilisée partiellement par MgO (Mg-PSZ), et des céramiques renforcées par de la zircone (ZTC), a été mesurée par flexion trois points entaillée (SENB) avec des entailles faite mécaniquement et de largeur varient entre 150 et 1800 μm. On a constaté que la réponse de chaque matériau dépend essentiellement de sa microstructure. Les résultats expérimentaux montrent que lorsque le mécanisme de renforcement ‘dynamique’ se produit, comme le renforcement par transformation de phases, la résistance SNEB dépend particulièrement de la largeur de l'encoche. Par exemple la résistance SNEB de la zircone polycristalline tétragonale stabilisée par Y 2 O 3 et de la zircone stabilisée partiellement par MgO, qui sont typiquement des céramiques qui se renforcent par transformation de phases, augmente de manière significative avec l'augmentation de la largeur de l'encoche quand celle ci reste inférieure à 1 mm. Une augmentation plus importante de la largeur de l'encoche n'amène qu'une faible augmentation de la résistance SENB. Des céramiques à base d'alumine renforcées par de la zircone (ZTA) montrent un comportement similaire, bien que l'augmentation de la résistance SENB est plus petite pour les céramiques Y-TZP. La dépendance de la résistance SENB par rapport à la largeur de l'encoche pour les céramiques renforcées par transformation de phase est reliée à la zone transformation à la pointe de l'encoche, produite par usinage avec une lame de diamant. A l'opposé la résistance SENB des céramiques à base d'alumine est peu influencée par la variation de la largeur de l'encoche. La relation entre les valeurs mesurées de la résistance SENB et les mécanismes intervenant lors du renforcement est discutée.

Improved Method for Sectioning Pectoral Spines of Catfish for Age Determination

ABSTRACT A modified low-speed saw provided fast and precise sectioning of catfish pectoral spines for use in aging studies. In one hour, 10–15 spines can be sectioned, the sections mounted, and the annuli counted. Two methods commonly used to section ictalurid pectoral spines are (1) acid decalcification, followed by the use of a razor blade or microtome to slice the softened spines, and (2) cutting hard spines with electric saws. Decalcifying methods are time-consuming, and we had difficulty attaining the proper spine consistency for sectioning when we used decalcification techniques. Electric saws with toothed blades tended to obliterate the first-year annulus at the periphery of the central lumen on spines of channel catfish (Scholl 1968). A low speed saw equipped with two, thin parallel diamond blades was used to section fish fin rays and spines (Shepard and Nichy 1984), but drawbacks are that the preparation is time-consuming and the blades tend to warp. We used a low speed saw with a thick (0.3 mm),...

Effect of Radial Keratotomy Incision Direction on Wound Depth

The majority of ophthalmic surgeons who perform radial keratotomy make incisions from the optical clear zone to the limbus (downhill; centrifugal), instead of from the limbus to the optical clear zone (uphill; centripetal). To compare the efficacy of these techniques, one surgeon performed keratotomy incisions in 10 eyes of 5 monkeys using the same double-edged diamond blade set to 80% of central pachometry. Four or eight centrifugal (downhill) and centripetal (uphill) incisions were made in each eye. Achieved incision depth was measured by light microscopy 2.5 to 8 months postoperative. Downhill incision depth averaged 46% (range 38% to 61%), whereas uphill incision depth averaged 74% (range 53% to 87%) (P less than .0005). In both groups, incision deviation from the perpendicular (lateral tilt error) was greatest adjacent to the optical clear zone (P less than .01). These differences may be explained by tilt error (forward or backward) or by the perpendicular front cutting action of a vertical blade being more effective than the angled blade.

Scanning Electron Microscopy of Corneal Incisions Using Steel, Diamond, and Sapphire Blades

In order to compare the wound morphology they produce, we used steel (Myocure), diamond (CILCO DK 121), and sapphire (Katena K2-6500) blades, to make parallel linear incisions, 500 microns deep, in 12 fresh enucleated porcine eyes. There was no discernible difference among the blades in terms of either the morphology of the collagen lamellae of the sides or the depth of the incisions produced. The major differences in the cuts produced were attributable primarily to the differences in the footplates.

Clinicopathologic Study of Healing Excimer Laser Radial Excisions

Four radial linear excisions were created by an argon fluoride (193 nm) excimer laser in the edematous cornea of a blind eye of a diabetic human patient. Partial thickness corneal trephinations were performed at 3, 7, and 18 months after surgery for histopathologic examination. At 3 months, a wide gap in Bowman's layer permitted extension of an epithelial plug to a depth of 0.35 mm; at 7 and 18 months, the depth of the epithelial plug was decreased to 0.29 mm and 0.01 mm, respectively. With wound healing, excision width decreased and the two cut ends of Bowman's layer were almost reapposed by 18 months, suggesting wound contraction. Linear excisions with the excimer laser appear to be wider than incisions made with a diamond blade, but the pattern of wound maturation appears to be similar.

Radial Keratotomy in the 1990s and the PERK Study

When radial keratotomy was introduced into the United States, the procedure was performed using razor blade fragments whose extension was determined by sighting on a linear scale block; up to 24 or more incisions of various length per eye were used. As with any new procedure, significant complications occurred. The technique was declared "a risky procedure of unproven long-term success."¹The Prospective Evaluation of Radial Keratotomy (PERK) Study was begun in March 1982 as a nine-center trial with 10 participating surgeons that was designed to determine the outcome of a single standardized technique for simple (no astigmatism) myopia.²About the time the PERK Study began, current surgical procedures were just being applied by the majority of radial keratotomy surgeons (diamond blades, ultrasonic measurement of corneal thickness, reduction of the length and number of incisions to ⩽16).³In this issue ofThe Journal, Waring and coworkers⁴provide

Precision cut off grinding of glass with a diamond blades.

Diamond blade are widely used for cut off grinding of hard and brittle materials. However, there are some problems to be solved in order to improve the cutting accuracy and the productivity. They are the occurrence of chipping, which results in the increase of the kerf width, and the deterioration of the cutting groove straightness. In this study, a series of cutting tests are carried out to clarify the influence of the cutting conditions on these technological problems. Practical cutting conditions, which can reduce the occurrence of chipping and improve the groove straightness are presented.

精密切断用薄刃ダイヤモンド砥石の機的的性質

Thin diamond blade is widely used for the precision slicing of electronic parts such as magnetic head. It is well known experientially that some properties of blade have a great influence on the machining characteristics of workpiece, i.e. the work damage and the blade wear.ln order to understand the relation between the properties of blade and the machining characteristics, the mechanical properties of thin diamond blade are investigated in detail through the measurements of the tensile strength, the dynamic visco-elasticity and the wear resistance of bonding material. It is found from the experiments that there are notable differences in the mechanical properties of various blades.

Comparison of the trabecular and cortical tissue moduli from human iliac crests.

The purpose of this study was to design a method to produce and test mechanically microspecimens of trabecular and cortical tissue from human iliac crests, and compare their measured moduli. Rectangular beam specimens were prepared on a low-speed diamond blade saw and a miniature milling machine. The final specimen dimensions ranged from approximately 50-200 microns for base and height. The modulus of each specimen was measured using three-point bending tests across a span length of 1.04 mm and performed at a constant rate of displacement. A subset of specimens was recovered for a radiographic estimation of degree of mineralization. The results showed the mean trabecular tissue modulus of all iliac crest specimens to be 3.81 GPa, whereas cortical tissue specimens averaged 4.89 GPa. This was a significant difference according to a two-way analysis of variance that controlled for differences between donors. No strong correlations were found between modulus and mineral density. Future investigations that consider other microstructural characteristics and their contributions to modulus, and specimen size effects, are indicated.

From flintstone to diamond blade: a new multifunctional instrument for use in coronary surgery.

We report on the development and clinical application of a diamond surgical knife specially designed for the preparation, initial incision, and bidirectional enlargement of coronary arteries. The ergonomic design of the knife enables the performance of all the necessary steps in a coronary incision with a single instrument and obviates the need for different shaped knives and scissors during preparation. The lasting sharpness of the diamond blade results in a far cleaner, less traumatic, cutting edge as can be demonstrated by scanning electron micrographs of incised coronary walls after the use of various types of coronary knives and scissors.

Treatment of symptomatic peripheral atherosclerotic disease with a rotational atherectomy device

Narrowings 70 to 90% in diameter in 3 iliac, 4 superficial femoral and 2 popliteal arteries were crossed and atherectomized successfully in 6 patients using the Squibb Rotablator TM under angiographic guidance during surgical bypass procedures on these arteries. The Rotablator consists of a 1.25 to 4.5 mm diameter oblong burr with tiny diamond blades mounted on a flexible shaft, which tracks over a spring-tip guidewire and rotates at speeds > 120,000 rpm. All stenoses were reduced to ≤50% of the normal luminal diameter. No significant complications occurred. Of the 6 patients having the atherectomy procedure, 5 were reevaluated by duplex Doppler measurements 1.5 to 5.5 (mean 3.5) months after atherectomy and found to be patent with only mild residual flow disturbance. Repeat follow-up by angiography after a mean of 5.2 months, however, showed only 3 (37%) of the atherectomized segments in 3 patients to still be patent. All were symptomatically improved. Of the effluent particles analyzed, 90% were < 8 microns in size, while only 5% reached 250 microns. With improvements in technique, the largest particles were 150 to 180 microns, constituting only 1.4% of effluent debris. Samples of the effluent from 2 patients were injected in vivo into the left coronary system of 2 pigs. There were no acute hemodynamic or electrocardiographic complications or pathologic evidence of muscle necrosis or vascular thrombosis 18 to 48 hours later. These preliminary results with respect to feasibility and safety of the Rotablator are promising.

Transverse astigmatic keratotomy combined with phacoemulsihcation and intraocular lens implantation

Transverse astigmatic keratotomy is a surgical technique to correct preoperative corneal astigmatism during cataract surgery. The operative technique is described and the results of my first 40 cases are reviewed. The average keratometric astigmatism for this group before surgery was 2.6 diopters (D). The average reduction in astigmatism was 1.5 D, which yielded a final residual average astigmatism of 1.1 D after surgery. Cases of substantial astigmatism showed the most improvement. Less improvement was seen in cases of minimal preoperative astigmatism. No increase in net keratometric astigmatism was seen in any of the eyes studied. Minor complications were limited to several small corneal abrasions created by the frontcutting diamond blade and one late temporary wound dehiscence. The only serious complication was one case of corneal macroperforation. Recommendations for handling this complication and future high astigmatism cases are given.

Radial keratotomy: Analysis of efficacy and predictability in 1,058 consecutive cases Part I: Efficacy

Effectiveness and predictability of anterior radial keratotomy to correct myopia and astigmatism or astigmatism alone were evaluated in 1,058 consecutive surgeries. The surgical technique consisted of retrobulbar anesthetic injection, topical anesthetic, from four to 32 radial incisions with a diamond blade, cutting from the optic zone to the limbus, optical clear zone diameter from 2.75 mm to 5.00 mm, longitudinal or tangential incisions, if necessary, to correct astigmatism, and bilateral surgery at the same sitting in 72% of cases. There were 816 of 1,018 subjects (80.2%) between ± 1 diopter (D) of emmetropia following surgery; 86.1% of 1,003 eyes were 20/40 or better uncorrected postoperatively; mean astigmatism was reduced from 0.97 D preoperatively to 0.66 D postoperatively. Sixty-seven eyes (6.3%) had microperforations; seven (0.7%) had macroperforations requiring a suture. The mean change in refraction for patients with and without perforations was 5.43 D and 4.20 D, respectively.

Stability of Refraction Following Radial Keratotomy over 4 Years

ABSTRACT: The mean spherical equivalents of 43 eyes treated by radial keratotomy between 1980 and 1982 were compared by a repeated analysis of variance across 4 years. There was no significant increase in hyperopia between the first and fourth years. The changes in mean spherical equivalency stabilized after the first year of surgery. The eyes demonstrated substantial reductions in myopia 1 year after surgery. Furthermore, there was no difference in the mean spherical equivalents achieved by the 31 procedures performed with carbon steel blades as opposed to the 12 procedures performed with diamond blades during any of the follow-up years.

Hornhauttrepanation bei perforierender Keratoplastik: Untersuchung über den Grad der (Un-)Genauigkeit und Darstellung eines neuen Trepans

The accuracy of corneal trephination with a Franceschetti trephine was investigated on Duragel contact lenses. A modified 7.3 mm Crock trephine (Brit. J. Ophthal. 62 [1978] 74-80) with a rotating diamond blade fitted was compared with the above-mentioned method. Trephination of Duragel lenses from the convex side yielded diameters either larger or smaller than 7 mm. With one exception trephination from the concave side produced disks smaller than 7 mm. All Duragel disks had an elliptical configuration after trephination with the Franceschetti trephine. Trephination with the modified Crock trephine yielded disks with diameters close to 7.3 mm in all meridians.

Endothelial damage in monkeys after radial keratotomy performed with a diamond blade.

Anterior radial keratotomy was performed with a diamond blade in ten rhesus monkey eyes. Results were compared with those of a previous study in which a metal blade was used. Histologic assessment showed endothelial degeneration, but fewer edematous endothelial cells, than in the previous study. Specular microscopy demonstrated statistically significant endothelial cell losses (7.99%), when preoperative and three-month postoperative values were compared. Autoradiography showed little cell division in the endothelial cell layer. Cell loss seemed to be repaired mainly by the spreading of neighboring cells. Endothelial cell division is also limited in humans, and the cumulative loss of cells due to surgical trauma combined with continuous damage-related losses and later age-related reductions in cell numbers could produce corneal decompensation in some patients years after radial keratotomy.

Analysis of Incision Depth Following Experimental Radial Keratotomy

Eight-incision radial keratotomy was performed on a series of cadaver eyes using ultrasonic pachymetry and both metal and diamond blades. There were no statistically significant differences in mean corneal flattening (approximately 9.5 diopters) obtained with either the diamond or metal blades. Short diamond knife incisions produced less flattening that was statistically significant (5.8 diopters). Histologic analysis of incision depth revealed similar results with both the diamond (84%) and metal (86%) blades.