Journal of refractive and corneal surgery

Publisher: International Society of Refractive Keratoplasty


Discontinued in 1994. Continued by the Journal of Refractive Surgery (1995) (1081-597X).

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    Journal of refractive and corneal surgery
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Publications in this journal

  • Journal of refractive and corneal surgery 01/1998; 10(4):466.
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    ABSTRACT: Refractive error is assessed in the seated position while keratorefractive procedures are performed in the supine position. Since position-induced ocular torsion could yield suboptimal results from improper axis alignment, this study was undertaken to ascertain whether ocular cyclotorsion occurs when a subject moves from a seated to supine position. Fifty eyes of 29 subjects with refractive cylinder greater than 0.50 diopters were enrolled. Refraction was done with a phoropter and the correction was placed in a trial frame using plus cylinder. Astigmatic axis was determined in the seated and supine positions for 32 eyes by utilizing the "rocking the cylinder" technique and for 32 eyes using the Jackson cross cylinder. Both techniques were used for 14 eyes. No statistically-significant difference for cylinder axis measured in the seated versus supine position was observed using the rocking the cylinder (4.3 degrees standard deviation [SD], 3.5 degrees, range 0 degrees to 13 degrees, p = NS) or the Jackson cross cylinder methods (2.3 degrees, SD, 1.9 degrees, range 0 degrees to 7 degrees, p = NS). Approximately 25% of eyes had a change in axis of 7 degrees to 16 degrees. These data suggest that the cylinder axis does not change significantly or predictably when most subjects move from the seated to supine position. The Jackson cross cylinder method seems more accurate and reproducible than the rocking the cylinder technique in determination of astigmatic axis under these circumstances.
    Journal of refractive and corneal surgery 01/1994; 10(6):615-20.
  • Journal of refractive and corneal surgery 01/1994; 10(2):83-6.
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    ABSTRACT: Most excimer laser refractive procedures use a computer driven mechanical diaphragm to shape the laser beam. Studies are currently underway using an ablatable polymethylmethacrylate (PMMA) mask to transfer a new spherical or toric curve to the cornea for the correction of myopia and astigmatism; it may leave a smoother corneal surface than diaphragm procedures. As part of a Phase IIb FDA clinical study, 25 eyes of 25 patients underwent excimer laser photorefractive keratectomy using a hand held ablatable mask. Fifteen eyes had attempted spherical corrections of up to 6.00 diopters (D) and 10 had toric corrections of up to 6.00 D of sphere and 2.75 D of astigmatism. Seventy-four percent of all eyes achieved uncorrected visual acuity of 20/40 or better--86% in the spherical group and 63% in the astigmatism group. Sixty-nine percent of eyes were within +/- 1 D of the attempted correction. In eyes treated for astigmatism, mean astigmatism decreased from 1.48 D preoperatively to 0.86 D postoperatively. Approximately one half of the eyes treated for astigmatism had a decrease in cylinder of more than 0.5 D. One eye lost 2 Snellen lines of best spherical corrected visual acuity. Video keratography showed toric ablations to result in an elliptical optical zone. Analysis of centration of the procedure showed 66% of ablations centered within 1.0 mm of the center of the pupil aperture. The ablatable mask represents a promising modality for the treatment of eyes with both myopia and myopic astigmatism.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S250-4.
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    ABSTRACT: Photorefractive keratectomy (PRK) requires a careful pharmacologic regimen during the postoperative period to reduce corneal haze and refractive myopic regression. Noncorticosteroidal anti-inflammatory drugs limit postablative corneal inflammation without the complications that may occur during corticosteroid treatment. Twenty consecutive eyes of 10 patients with attempted correction ranging from 4.00 to 9.00 D of myopia were studied. During the postoperative period, corticosteroid drops (dexamethasone 0.1%) were instilled in the first eye of each patient, and the second eye was treated with diclofenac sodium ophthalmic solution 0.1% (Voltaren). Follow-up was 12 months after surgery. Corneal haze and refraction were studied. Six of the 10 eyes treated with noncorticosteroidal anti-inflammatory drugs did not show any significant difference in corneal haze and refractive evolution compared to the contralateral eyes treated with corticosteroids. Two eyes (20%) showed less corneal haze and more refractive stability than the contralateral eyes. In two eyes (20%), we observed similar corneal haze but more refractive regression than in the contralateral eyes. Eyes treated with topical diclofenac sodium had a similar postoperative course as those treated with corticosteroids, but without the adverse effects of corticosteroids. Topical nonsteroidal anti-inflammatory drugs are represented by diclofenac (Voltaren), which has significant ocular penetration. This permits reduction of the possibility of general and ocular complications that frequently occur with corticosteroids. The aim of this study was to evaluate the efficacy of topical nonsteroidal antiinflammatory drugs vs. corticosteroidal eyedrops after photorefractive keratectomy (PRK) to reduce moderate and high myopia.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S287-9.
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    ABSTRACT: The Summit Technology erodible mask treatment of astigmatism does not alter the keratometric astigmatism significantly, even though the refractive astigmatism appears to improve by about 50%. Myopia is satisfactorily treated with the erodible mask, but there is slightly more undercorrection compared to photorefractive keratectomy (PRK) using an expanding diaphragm. Increasing the minus power in ordering the mask cylinder improves the myopia result, but not the keratometric astigmatism result. The following factors do not influence the keratometric astigmatism result: 1) The type of astigmatism (with-, against-the-rule, or oblique); 2) The initial keratometry readings; and 3) The time from the commencement of epithelial removal to laser treatment.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S239-45.
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    ABSTRACT: Thermal shrinkage of stromal collagen is known to produce changes in the corneal curvature. We designed a novel, noncontact laser beam delivery system to perform laser photothermal keratoplasty. The instrument consisted of a pulsed holmium:YAG laser (2.10-micrometer wavelength, 250-microsecond pulse width, 5-hertz repetition rate) coupled via a monofilament fiber to a common slit-lamp microscope equipped with a polyprism, an adjustable mask, and a projection lens. The system projected an 8-spot annular pattern of infrared laser energy on the cornea to achieve a thermal profile within the stroma and to attain controlled, predictable collagen shrinkage. The system produced treatment patterns of 8 to 32 spots of 150 to 600 microns diameter in concentric rings, continuously adjustable between 3 and 7 mm. The versatility of the system in creating different treatment patterns was tested on thermal paper and human cadaver eyes. A uniform beam profile and different treatment patterns for myopia, hyperopia, and astigmatism were obtained. Myopic correction of 6.00 diopters was demonstrated on cadaver eyes. Corneal topography documented corneal flattening (> 6.00 D) with the following treatment parameters: each spot size on the cornea = 300 microns, radiant exposure of each spot = 18.0 J/cm2, number of pulses = 1, diameter of the treatment ring = 3 mm. Noncontact slit-lamp microscope laser delivery system for laser photothermal keratoplasty provides flexible and precise selection of laser treatment parameters. It may improve the efficacy of the procedure.
    Journal of refractive and corneal surgery 01/1994; 10(5):511-8.
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    ABSTRACT: We analyzed the data from 1821 patients (2920 eyes) who received photorefractive keratectomy (PRK) to investigate the postoperative complications which cause a significant decrease in visual acuity. A corneal haze of grade 2 or more developed in 9 patients (11 eyes, 0.38%) and corticosteroid-induced ocular hypertension occurred in 3 patients (4 eyes, 0.14%). Three patients (4 eyes) who had corneal haze of grade 2 or more underwent repeated photorefractive keratectomy and one patient (2 eyes) with steroid-induced ocular hypertension underwent trabeculectomies. A decrease of best spectacle corrected visual acuity of two lines or more was detected in 7 patients (8 eyes, 0.27%), caused by irregular astigmatism, steroid-induced cataract, incidental choroidal neovascular membrane, and an unknown origin. Good predictability and stabilization after photorefractive keratectomy was maintained at the 2 year follow-up. However, some subjective symptoms were reported by many patients and some complications occurred in a minority of eyes despite the excellent visual outcome in a large majority.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S226-30.
  • Journal of refractive and corneal surgery 01/1994; 10(5):587-8.
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    ABSTRACT: Single and double deepening of the peripheral part of radial keratotomy incisions are used to increase the refractive effect. Single peripheral deepening was performed in 52 eyes of 36 patients and double peripheral deepening in 19 eyes of 14 patients who received radial keratotomy. In the single peripheral deepening group, the mean change in refractive power was 4.01 diopters (D); 53.8% of eyes were within +/- 1.00 D of emmetropia; residual myopia was greater than -1.00 D in 46.2% of eyes; 65.4% of eyes achieved an uncorrected visual acuity greater than or equal to 20/40. In the double peripheral deepening group, the mean change in refractive power was 5.07 D; 52.6% of eyes wee within +/- 1.00 D of emmetropia; residual myopia was greater than -1.00 D in 47.4% of eyes; 89.4% of eyes achieved an uncorrected visual acuity greater than 20/40. The difference in mean dioptric change between the standard radial keratotomy groups and the single and double peripheral deepening groups was 0.53 D and 0.47 D, respectively. Considering the limited additional dioptric change compared with the standard radial keratotomy surgical technique and the increased rate of complications, we think that peripheral deepening in radial keratotomy should be avoided.
    Journal of refractive and corneal surgery 01/1994; 10(6):621-4.
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    ABSTRACT: Photorefractive keratectomy (PRK) was performed on 98 consecutive normal myopic eyes with the Summit OmniMed laser System. The minimum follow-up was 3 months and 31 were followed for 6 months. Preoperative myopia ranged from -1.25 to -12.00 D. The myopic eyes were divided into 4 groups according to the amount of myopia: group 1 (-1.25 to -3.00 D), 17 eyes; group 2 (-3.12 to -6.00 D), 42 eyes; group 3 (-6.12 to -9.00 D), 29 eyes and group 4 (> 9.00 D), 10 eyes. In group 1 mean uncorrected visual acuity was 0.87 at 3 months, 1.0 at 6 months and all of the eyes were within 0.50 D of the attempted correction. In group 2 mean uncorrected visual acuity was 0.76 at 3 months, 0.87 at 6 months and 92.3% of the eyes were within 0.50 D of the attempted correction. In group 3 mean uncorrected visual acuity was 0.65 and 0.66 at 3 and 6 months respectively and 77.8% of eyes were within 0.50 D of the attempted refractive correction. In group 4, mean uncorrected visual acuity was 0.46 and 0.7 at 3 and 6 months, respectively, and 100% were within 0.50 D of the attempted correction. Two eyes lost 2 lines and 4 eyes gained 2 or more lines of their preoperative best spectacle corrected visual acuity. Three eyes exhibited steroid induced rise in intraocular pressure that was controlled with topical timolol. No serious complications occurred. Despite the short follow-up, photorefractive keratectomy with the 193 nm excimer laser appears to be an effective and safe treatment for the correction of myopia.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S231-4.
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    ABSTRACT: Photoablation in the infrared (IR) is an option for future refractive and corneal surgery; its basic principles have not yet been investigated systematically. For the first time, the free electron laser allows the dynamic study of photoablation over a wide range of wavelengths with variable combinations of pulselength and energy. The goal of this study is to use the free electron laser as a tool to describe photoablation in the IR quantitatively. We studied the function of wavelength as it is related to target material spectroscopy and the effects of corneal hydration and the pulse repetition rate. Surface absorption spectroscopy of the human cornea and of gelatin as a proven model of the cornea was performed between 2.7 and 6.7 microns. Gelatin probes of well-defined thickness (140 +/- 5 microns) and controlled hydration (wet/dry weight 1 to 4.5) served as target material. Photoablation was performed with the Vanderbilt University free electron laser (Nashville, Tenn) in September 1992 at a fluence of 1.27 J/cm2, and a macropulse of 4 microseconds, composed of 2 ps micropulses at a 2.9 GHz pulse repetition rate. Wavelength was tunable between 2.7 and 6.7 microns at stable beam profiles. Ablation experiments were performed as a function of energy, hydration, and pulse repetition rate. Ablation rates were assessed by a) perforation experiments, and b) direct measurements using confocal laser topometry (UBM, Ettlingen, FRG). Ablation rate, assessed by perforation experiments and topometry, correlated well with the corresponding measured absorbencies of the target material: maximal ablation rate at maximal target absorption, around the 3- and 6-micrometer water absorption bands. The ablation threshold at 6.2 microns was 0.7 +/- 0.05 J/cm2 (perforation) and 0.55 +/- 0.08 J/cm2 for depth measurements. Ablation rate as a function of hydration increased to 2.3 (wet/dry weight) with a decrease for higher hydrations. Ablation rate as a function of the pulse repetition rate showed an increase of up to 20 Hz, where it was found to be 60% higher. The first systematic use of free electron laser technology positively correlated ablation efficiency with target material absorption, thus identifying a "new" promising wavelength at around 6.2 microns for materials with a high water content such as corneal tissue.
    Journal of refractive and corneal surgery 01/1994; 10(4):433-8.
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    ABSTRACT: To ensure optimal performance, it is imperative to properly maintain the condition of ophthalmic diamond scalpels. Refractive surgeons are often confronted with conflicting cleaning recommendations from manufacturers. The problem encountered is to maximize cleaning while minimizing trauma to the diamond to maintain its longevity. The author describes a flexible graded approach to cleaning and maintaining diamond scalpels. The principle of this approach was the development of four successive levels of cleaning based on an increasing risk of trauma to the diamond: Level I--irrigation with distilled water, Level II--hydrogen peroxide or enzyme cleaning, Level III--ultrasonic and detergent cleaning, and Level IV--mechanical styrofoam block cleaning. The protocol was performed prospectively on 50 consecutive radial keratotomy cases, inspecting the blade microscopically after each cleaning step, and determining the level at which cleanliness of the blade was achieved. The effectiveness (clean/dirty) of each cleaning level was evaluated by the author and an experienced surgical assistant. The difficulty in accurately measuring the amount of debris and the force necessary to remove it, limited the judgments made to subjective observation. Only 2 of 50 blades were cleaned at Level I, while 41 of 48 at Level III, and 7 of 7 at Level IV. A multi-leveled systematic process for cleaning maintenance appears most effective for maximal performance and longevity of diamond scalpels used for refractive keratotomy surgery.
    Journal of refractive and corneal surgery 01/1994; 10(5):582-6.
  • Journal of refractive and corneal surgery 01/1994; 10(4):468.
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    ABSTRACT: Cyanoacrylate adhesive has been used to treat corneal perforations and stromal melting disorders. We examined the efficacy of aerosolization as a means of applying cyanoacrylate to the cornea. Central corneal perforations were created with a 1-millimeter trephine in cadaver eyes. A small amount of N-butyl cyanoacrylate was delivered to the perforation site via aerosol. Experiments were also conducted with cadaver eyes which had received lamellar keratectomies to stimulate corneal thinning disorders. Adequate seal of the 1-millimeter perforation was achieved following aerosol application of cyanoacrylate adhesive. In experiments conducted with eyes which had been perforated and those which received lamellar keratectomies, smooth anterior surface contours were achieved using the aerosol technique. Aerosolization may be an effective method of applying cyanoacrylate adhesive.
    Journal of refractive and corneal surgery 01/1994; 10(2):149-50.
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    ABSTRACT: The vulnerability of the ocular coat to trauma following radial keratotomy is an issue of concern to both patients and physicians. Herein, we report two cases of eyes which were exposed to severe trauma after previously undergoing radial keratotomy procedures. In the first case, a woman sustained multiple facial bone fractures in a fatal airplane crash. In the second case, a man was involved in a case of blunt ocular trauma involving a high velocity racquetball. Rupture of the ocular coat did not occur in either case.
    Journal of refractive and corneal surgery 01/1994; 10(1):31-3.
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    ABSTRACT: Studies of corneal power changes resulting from photorefractive keratectomy generally rely on keratometer or videokeratograph measurements. These instruments convert corneal radius of curvatures values to optical powers by means of the single refracting surface formula, which incorporates an index of refraction value of 1.3375. This index approximates that of the tears but not the 1.376 index of the corneal epithelium or stroma. A hypothetical optical model was used to determine the most appropriate index to be chosen with respect to corneal power calculations relative to photorefractive keratectomy. The contribution of each refractive element in the tear lens-corneal surface to the total power of the eye was calculated in order to identify which index of refraction was most appropriate for the corneal power calculation. The outer tear surface has significant optical power but the tear layer as a whole has nearly zero power due to the offsetting negative power of the posterior test surface. There is no significant difference in the effective power of light leaving the corneal anterior surface when considered with or without the tear layer. Photorefractive keratectomy changes the epithelium and anterior surface of the corneal stroma, but does not affect the posterior stroma or other ocular media. Hence the refractive index for the corneal epithelium or stroma of 1.376 should be used in converting radius to optical power values. The error in assuming a corneal index of 1.3375 is a constant proportion equal to 11.4% of the corneal power reading. Photorefractive keratectomy presents a situation in which the actual corneal refractive index of 1.376 should be used for correct corneal radius to power conversions. This may be accomplished by changing the index value in the instrument algorithm for keratometry and videokeratography to 1.376 or by adding a correction factor of either 11.4% of the regular reading to its value or multiplying by the factor 1.114. In other applications of keratometry or videokeratography, the index 1.3375 may be more appropriate.
    Journal of refractive and corneal surgery 01/1994; 10(2):125-8.
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    ABSTRACT: Astigmatism following photorefractive keratectomy for myopia has been reported as stable as early as 2 to 3 months. The authors report 36 out of 60 consecutive eyes with variations in the cylindrical component of their refraction at 6 months after laser treatment. A standard photorefractive keratectomy was carried out on 60 consecutive eyes in 52 patients over a 7-month period. The manifest refraction of these eyes was followed for 6 months. Thirty-six eyes demonstrated a change in the cylindrical element of their refraction manifested as a change in cylinder power or axis, or both. The mean pretreatment cylinder power in the group that underwent a change in the cylindrical element was significantly higher than the mean of the group where this did not take place. The mean cylinder power change was 0.75 diopters (D) and in 9 eyes this change was 1.00 D or more. The corrected and uncorrected postoperative visual acuities were the same in the two groups. This observation implies meridional variability in the healing process of the anterior cornea following photorefractive keratectomy.
    Journal of refractive and corneal surgery 01/1994; 10(5):540-4.
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    ABSTRACT: Noncontact laser photothermal keratoplasty may provide a new alternative for the treatment of myopia, hyperopia, and astigmatism. The purpose of this article is to study the refractive effect that laser photoablation keratoplasty is capable of producing on a normal human cadaver cornea, including the relationship between the keratometric changes and laser treatment parameters. The human cadaver eyes were treated with a holmium laser (pulsed Ho:YAG, 2.10 microns, 250 microseconds) coupled to a maskable, polyprismatic delivery system mounted on either an optical bench or a slit-lamp microscope. Using a topographic videokeratography system, we first investigated the refractive effect that noncontact laser photothermal keratoplasty would produce on a normal cadaver cornea. We then studied the keratometric changes produced by different radiant exposure levels at a fixed treatment pattern, as well as by different treatment patterns at a fixed radiant exposure level. Finally, we studied the possible therapeutic application of laser photothermal keratoplasty for correcting high postoperative astigmatism on a cadaver eye model. For the single-pulse 3-millimeter ring of eight-spot treatment, the keratometric power of the cornea initially increased with the radiant exposure and peaked at 26 J/cm2. The refractive effect was increased by projecting an additional set of eight spots equidistant between the first eight spots on the same diameter ring. Eighteen J/cm2 was the minimal radiant exposure required to produce consistent and predictable keratometric changes. The corneas were flattened using treatment patterns smaller than or equal to 3 mm in diameter and steepened using treatment patterns larger than or equal to 5 mm in diameter. A transition zone between 4 and 5 mm was observed in which minimal and unpredictable keratometric changes of the central cornea occurred. The surgically-induced astigmatism (> 10.00 D) was corrected by progressive laser photothermal keratoplasty treatments. Laser photothermal keratoplasty can acutely steepen and flatten the cornea in human cadaver eyes.
    Journal of refractive and corneal surgery 01/1994; 10(5):519-28.
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    ABSTRACT: Photorefractive keratectomy (PRK) using the current erodible mask technique is difficult to perform, because of the stringent requirements in the alignment of the eye to the mask and in the centration of the mask under the laser beam. The surgeon has to manually control the eye-cup over 5 degrees of freedom. If not accurately done this may lead to decentration of the ablation and bring about technical problems during treatment. The aim of this study was to find a way to improve and simplify the erodible mask procedure. We used a modified non-contact mask eye-cup with a rigid mechanical support to obtain a precise and reliable positioning in space of the mask itself. Eye centration over the pupillary aperture was obtained with conventional patient fixation on the reference aiming light, coaxial to the laser beam path, and controlled using two He-Ne beams aimed at the corneal apex. Good reliability was demonstrated in the first 22 eyes operated on using this technique. All the masks were ablated with good centration of the laser beam over the polymethylmethacrylate (PMMA) button, and all the treatments were satisfactorily centered over the pupillary aperture. No complications or side effects were encountered during the treatments. Compared to the conventional erodible mask procedure, this technique proved much faster to perform, was more comfortable for both patient and surgeon, and was technically easier for the operator.
    Journal of refractive and corneal surgery 01/1994; 10(2 Suppl):S246-9.

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