Penetrating and Intrastromal Corneal Arcuate Incisions in Rabbit and Human Cadaver Eyes: Manual Diamond Blade and Femtosecond Laser-Created Incisions.

OBJECTIVES: To compare morphologic differences between freehand diamond or femtosecond laser-assisted penetrating and intrastromal arcuate incisions. METHODS: Freehand diamond blade, corneal arcuate incisions (180° apart, 60° arc lengths) and 150 kHz femtosecond laser (80% scheimpflug pachymetry depth corneal thickness) arcuate incisions were performed in rabbits. Intrastromal arcuate incisions (100 µm above Descemet's membrane, 100 µm below epithelium) were performed in rabbit corneas (energy 1.2 µJ, spot line separation 3 × 3 µm, 90° side cut angle). Eyes were examined by slit lamp and light microscopy up to 47 days post-procedure. Freehand diamond blade penetrating incisions, and femtosecond laser penetrating and intrastromal arcuate incisions (energy 1.8 µJ, spot line separation 2 × 2 µm) were performed in cadaver eyes. Optical coherence tomography was performed immediately after surgery and the corneas were fixed for light scanning and transmission electron microscopy. RESULTS: The rabbit model showed anterior stromal inflammation with epithelial hyperplasia in penetrating blade and laser penetrating wounds. The laser intrastromal and penetrating incisions showed localized constriction of the stromal layers of the cornea near the wound. In cadaver eyes, penetrating wound morphology was similar between blade and laser whereas intrastromal wounds did not affect the cornea above or below incisions. CONCLUSION: Penetrating femtosecond laser arcuate incisions have more predictable and controlled outcomes shown by less post-operative scarring than incisions performed with a diamond blade. Intrastromal incisions do not affect uncut corneal layers as demonstrated by histopathology. The femtosecond laser has significant advantages in its ability to make intrastromal incisions which are not achievable by traditional freehand or mechanical diamond blades.

Mechanized astigmatic arcuate keratotomy with the Hanna arcitome for astigmatism after keratoplasty.

PURPOSE: To report the results of correction of post-keratoplasty astigmatism by arcuate keratotomy performed with the Hanna arcitome (Moria). SETTING: Service 5, Hôpital des 15-20, Paris VI University, Paris, France. METHODS: Forty eyes operated on for post-keratoplasty astigmatism using the Hanna arcitome were retrospectively studied. Paired symmetrical arcuate keratotomies were performed on the graft button. Mean follow-up was 10.8 months +/- 11.2 (SD). Outcome measures included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and subjective refraction. For statistical analysis, visual acuity data were transformed into logMAR units. The refractive data were analyzed using the Alpins method. RESULTS: By a mean of 10.8 +/- 11.2 months after surgery, the UCVA had improved a mean of 0.28 +/- 0.46 lines, which was significant (P = .013). The BSCVA remained stable. The mean subjective cylinder was 8.84 +/- 3.00 diopters (D) preoperatively and 4.88 +/- 2.50 D postoperatively (P<.001). The changes in postoperative subjective cylinder values correlated with preoperative cylinder values (r(s) = 0.584; P<.0001). The subjective axis was modified by 20 degrees or less in 27 eyes (67.5%). The mean surgically induced astigmatism was 8.07 +/- 3.83 D and the mean correction index, 0.96 +/- 0.46. One microperforation occurred and required suturing. Incisions were off center in 1 case, and 2 patients had an allograft rejection after the procedure. CONCLUSIONS: Arcuate keratotomy performed with the Hanna arcitome was effective in reducing post-keratoplasty astigmatism. The device enabled safer, easier arcuate incisions than with manual techniques. However, predictability and efficacy could be improved by a more accurate nomogram.

Refractive outcomes after arcuate keratotomy using the Terry astigmatome.

PURPOSE: To investigate the refractive outcomes after arcuate keratotomy for astigmatism. SETTING: Uludag University, Faculty of Medicine, Department of Ophthalmology, Bursa, Turkey. METHOD: Sixteen eyes of 11 patients with astigmatism had arcuate keratotomy using the Terry astigmatome. The mean age of the patients was 36 years +/- 10 (SD). All patients received preoperative and postoperative ophthalmic examinations consisting of best spectacle-corrected (BSCVA) and uncorrected (UCVA) visual acuities, corneal topography, and ultrasonic pachymetry. Surgery was performed using topical anesthesia of oxybuprocaine 0.1% eyedrops. The Terry astigmatome was selected by the mean paracentral (estimated incision area) corneal thickness. All patients received topical ofloxacin 0.3% and topical diclofenac 0.1% eyedrops postoperatively. RESULTS: The mean corneal astigmatism was -4.0 +/- 1.1 diopters (D) (range -2.2 to -6.0 D) preoperatively and -1.8 +/- 0.8 D (range -0.6 to -3.0 D) postoperatively. The mean surgically induced corneal astigmatism was 2.5 +/- 0.6 D. The mean UCVA (logMAR) was 0.74 +/- 0.25 preoperatively and 0.18 +/- 0.23 1 week postoperatively, and the mean BSCVA (logMAR) was 0.19 +/- 0.24 and 0.19 +/- 0.23, respectively. There were no intraoperative or postoperative complications. CONCLUSION: Arcuate keratotomy using the Terry astigmatome was a safe and reliable treatment for corneal astigmatism.

The suction bridge for radial keratotomy may avoid late hyperopic shift.

BACKGROUND: Radial keratotomy may induce late hyperopic shift. We present data on 140 consecutive eyes with a follow-up of up to 3 years that underwent radial keratotomy with the RK suction bridge. METHODS: We conducted a retrospective study of 140 consecutive eyes that had radial keratotomy between 1987 and 1994. Mean preoperative spherical equivalent was -5.21 D (range -2.00 to -9.75 D). All operations were performed by one surgeon (JHK) with the RK suction bridge. A suction ring maintaining physiological intraocular pressure immobilized the eye and left a peripheral rim of uncut cornea. The ring incorporated an eccentric bridge that guided the radial keratotomy knife. The knife setting was 90% of the central corneal thickness, measured by pachymetry. Spherical equivalent refraction and spectacle corrected visual acuity were measured at 1 week, 1, 3, 6 months, 1 year, and 3 years after radial keratotomy. RESULTS: The mean preoperative spherical equivalent refraction of -5.21 D dropped to -0.43 D at 1 week (n = 136), -0.71D at 1 month (n = 120), -0.85 D at 3 months (n = 95), -0.74 D at 6 months (n = 73), -0.77 D at 12 months (n = 79), and -0.85 D at 3 years (n = 67). Compared to 1 month spherical equivalent, at 3 years three eyes (4.4%) had moved > = or 1.00 D toward hyperopia. One eye (1.4%) shifted by 1.25 D. Paired t-tests of mean spherical equivalent refraction did not reveal significant shifts toward hyperopia. Mean preoperative spectacle-corrected visual acuity was slightly diminished at 1 week and was equal or better thereafter. CONCLUSIONS: Our 3-year data suggest that a late hyperopic shift following radial keratotomy may be prevented if an intact peripheral rim is maintained and cutting depth does not exceed 90% of the lowest corneal thickness.

Improved technique of circular keratotomy for the correction of corneal astigmatism.

BACKGROUND: Based on Gauss' law governing the comparison of hyperbaric pressure in the eye and atmospheric pressure, the authors present a procedure to correct astigmatism. The present paper describes an improvement of a technique for circular keratotomy that was published previously. METHODS: We present data on a consecutive series of 32 eyes with a mean corneal astigmatism of 4.66 diopters (D) (range -2.25 to -6.00 D) with a variety of clinical diagnoses. The astigmatic cornea was trephined with a diameter of 7 mm and a depth of 300 microns. After deepening of the trephination with a diamond knife to 550 microns over the steeper semimeridians, the intraocular pressure created a rounding of the cornea. The amount of astigmatic correction and extent of deepening were controlled intraoperatively with a keratoscope. No sutures were placed. RESULTS: In 32 consecutive eyes, corrections were between 50 and 90% of the initial cylindrical values after 1 week to 1 month. In 29 eyes (91%), the results obtained remained stable during a 1-year follow-up; in two eyes (6%), the 1-month results worsened by more than 1.00 D and in one eye (3%), results improved by more than 1.00 D. There were no complications during or after surgery. Wound gaping resulting in epithelial plugs did not occur. No patient lost one or more lines of spectacle-corrected visual acuity, but 13 eyes (40%) gained one or more lines. CONCLUSION: The technique of correcting corneal astigmatism by trephining to a depth of 300 microns, with deepening of the wound to 550 microns along the steep meridian and using no sutures can correct up to 10.00 D of astigmatism with reasonable stability.

Ultrasound biomicroscopy of tangential keratotomy incision depth after penetrating keratoplasty.

PURPOSE: To assess the accuracy and reproducibility of using ultrasound biomicroscopy to measure corneal refractive incisions in vivo. SETTINGS: Department of Ophthalmology, University of Vienna, Austria. METHODS: Ultrasound biomicroscopy was performed in five eyes of five patients who had previous tangential keratotomy for high postkeratoplasty astigmatism. Depth of the incision scar was documented, and the measurements were compared with those obtained preoperatively by ultrasound pachymetry readings of the corneal thickness and with the settings of the diamond knife blade. RESULTS: The measured depths reached 84.7% +/- 12.9 (SD) of corneal thickness compared with the intended 89.1 +/- 6.7% depth of incision. The relation between knife setting and achieved depth was 95.3 +/- 15.9%. CONCLUSION: Ultrasound biomicroscopy provided high-quality images of the incision scars, accurately measuring actual incision depth in vivo. It may become a clinically useful tool for the refractive surgeon as it contributes to the predictability and accuracy of keratorefractive procedures.

Calibration of trephine blade depth.

PURPOSE: To assess the accuracy and precision of the Barron radial vacuum trephine as an instrument for corneal lamellar dissection. METHODS: We describe a practical method to calibrate individual trephines prior to lamellar corneal procedures using the calibration microscope designed for diamond knives. RESULTS: We observed that one turn (360 degrees) of the trephine produced a mean blade displacement of 0.25 mm. However, individual trephines demonstrated a significant range of variability. CONCLUSION: For highly accurate trephination, it is useful to calibrate each individual trephine using the calibration microscope.

Precisäo e reprodutibilidade da videoceratografia / Accuracy and reproducibility of videokeratography

Avaliou-se a precisäo e a reprodutibilidade do sistema EyeSys de videoceratografia numa superfície esférica plástica (42,50 D) e em 58 córneas de 58 pacientes divididos em quatro grupos: 30 córneas normais, 10 córneas pós-certotomia radial, 8 córneas pós-excimer laser e 10 córneas com ceratocone. O método de análise incluiu, para os cálculos da precisäo e reprodutibilidade, todos os pontos de medida das superfícies de estudo. O sistema EyeSys apresentou, na superfície esférica, uma precisäo de 95 por cento das medidas com desvio <0,25 D e níveis de reprodutibilidade maiores na regiäo central (média de 0,0295D) que na regiäo periférica (média de 0,0962D). As córneas normais, pós-ceratotomia radial e pós-eximer laser apresentaram níveis semelhantes, nas regiöes central e periférica. A reprodutibilidade no ceratocone foi menor que nos demais grupos (p<0,05), tanto na regiäo central como na periférica. Nos quatro grupos, a reprodutibilidade foi maior na regiäo central da córnea (p<0,05). O sistema EyeSys parece proporcionar informaçöes clinicamente úteis a respeito da topografia corneana, particularmente na regiäo central

New technique for studying incision depth in experimental radial keratotomy.

Older techniques of analyzing incision depth in incisional keratotomy consist of serial transverse sections taken at various points along the incision. Information as to shape and depth of the incision are reconstructed from these sections. We describe a new method for studying the incision depth and profile along the entire incision length.

Arcuate transverse keratotomy with a mechanical arcutome based on videokeratography.

Corneal topographic hardware was used to develop software analysis for configuration and localization of relaxing astigmatic arcuate incisions. The software is based on the assessment of the results of corneal topographic measurements, performed by the EyeSys Corneal Analysis System. Data assessment includes: A) plotting the dioptric power curves along the circular zones that may be considered appropriate for the placement of arcuate cuts; B) determination of the astigmatic axes position in each selected arc; and C) finding the position of points with the mean dioptric power value between the neighboring astigmatic axes which determine the proposed placement of the arcuate incisions. The new instrument developed for arcuate astigmatic keratotomy includes the algorithm for incision(s) disposition, the software, and the arcutome.

Refractive keratotomy using a footplateless knife.

This article describes a diamond knife designed for safer, more precise extension of pre-existing refractive keratotomy incisions. The knife has a blade with a sharp vertical cutting edge whose progress is limited by a dull safety stop. The stop prevents extension of a wound by more than 500 microns at one time, minimizing the possibility of overextending the keratotomy incision into the optical zone. Because it requires no footplate, the knife improves visibility, allowing for more precise surgery.

[Infectious corneal ulcers--once with endophthalmitis--after photorefractive keratotomy with disposable contact lens]. / Infektiöse Hornhautgeschwüre--einmal mit Endophthalmitis--nach PRK mit Einmalkontaktlinse.

BACKGROUND: Infections of the cornea with or without involvement of intraocular tissues are severe complications after photorefractive keratectomy. We report on three cases with ulcerative keratitis and one case with severe endophthalmitis, which developed some days after laser treatment. PATIENTS AND METHODS: After 39 photo-therapeutic and 118 photo-refractive treatments without complications four young treated persons suffered from corneal infiltrations. Three of them developed severe corneal ulcerations, one a severe endophthalmitis. We used the laser machine of the company Schwind (193 nm wavelength, repetition rate 10 Hz, fluence 180-200 mJ/cm2). One part of the treatment which all patients had in common was the application of a disposable contact lens postoperatively, which was worn overnight. THERAPY AND FOLLOW-UP: Because all three patients with ulcerations revealed hyphen of fungi in their corneal-scratch material they were treated with antifungal agents locally and systemically. Due to the local and temporal connection the patient with the endophthalmitis was treated with antifungal agents, too. All corneal ulcerations healed with scars similar to a haze graded 3 to 4, the eye with the endophthalmitis healed almost completely. CONCLUSION: Probably the use of disposable contact lenses postoperatively, especially the overnight wear, during an extremely hot and humid summer lead to the described severe infections of the eyes after the "traumatisation" of the cornea by the excimer laser. A known higher concentration of Aspergillus in the air due to renovations of buildings in the clinical area might have been an additional negative effect. The avoidance of the use of disposable contact lenses postoperatively, especially the overnight wear, is emphasized.

New technique for knife and radial keratotomy.

BACKGROUND: Radial keratotomy is the most popular method of surgical correction of myopia, but requires further improvements. This study presents a new knife design for radial keratotomy. METHODS: Radial keratotomy was performed on 120 eyes of 60 patients with myopia. We utilized two diamond knife designs. The new knife allows a surgeon to perform corneal incisions of varying programmed depth with one movement of the hand, deeper at the limbus. As a control, we used the standard Fyodorov knife. One eye was operated on with one type of knife, the other eye with the other type. The number of incisions was the same with both techniques. RESULTS: After a 2-year follow up of the group of eyes operated on with the new knife, the mean keratometric power changed from 43.20 diopters (D) to 39.30 D, and the mean amount of myopia from -4.37 to -0.32 D. In the group of eyes operated on with the standard knife, the mean keratometric power changed from 43.20 to 39.50 D, and the mean amount of myopia from -4.36 to -0.40 D. CONCLUSIONS: The final refractive effect of the new knife was equal to that of standard knives. However, the new knife was more convenient: duration of surgery was shorter, and there was no need to change the length of the blade to deepen the incisions during surgery.

Mechanical methods in refractive corneal surgery.

Over the past decade, keratorefractive surgery has moved into the mainstream of ophthalmology as improved instrumentation and newer techniques have evolved. These new aspects increase the safety and effectiveness of the various keratorefractive procedures. The introduction of new techniques and knife designs has led to improved results with radial keratotomy. The newly developed arcuate keratome purportedly offers the possibility of improving the predictability of arcuate keratotomy. Keratomileusis and epikeratoplasty have been successful for some difficult refractive states, such as aphakia and high myopia. Intracorneal lenses are showing promise in correcting high refractive errors and may offer an alternative to the more technically challenging lamellar procedures performed for correcting these conditions. Intrastromal ring implants are early in their clinical testing, but may provide an alternative to radial keratotomy for correcting myopia. The predictability, effectiveness, safety, and stability are far from perfect for current procedures, but recent results are encouraging.