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Kato Y, Kojima T, Tamaoki A, Ichikawa K, Tamura K, Ichikawa K. Refractive Prediction Error in Cataract Surgery Using an Optical Biometer Equipped with Anterior-Segment Optical Coherence Tomography. J Cataract Refract Surg 2021; 48:429-434. [PMID: 34417778 DOI: 10.1097/j.jcrs.0000000000000781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 08/13/2021] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate refractive error after cataract surgery using an optical biometer equipped with anterior-segment optical coherence tomography (AS-OCT). SETTING Chukyo Eye Clinic, Nagoya, Japan. DESIGN Retrospective observational design. METHODS In total, 150 patients with cataract (150 eyes, mean age 73.4 ± 8.2 years, men 76, women 74), who underwent measurement of parameters with the anterior-segment OCT scanners ANTERIONTM (AS-OCTB) and IOL Master 700 (OCTB) before cataract surgery, were enrolled in the study. Refractive prediction error was compared between the two devices using the SRK/T, Haigis, and Barrett UII formulas for IOL power calculation. RESULTS There were significant differences between AS-OCTB and OCTB in axial length, mean corneal refractive power, anterior chamber depth, lens thickness, and corneal diameter. In the SRK/T formula, the arithmetic means of refractive prediction errors for AS-OCTB and OCTB were -0.06 ± 0.46 D and 0.02 ± 0.42 D, respectively. In the Haigis formula, the arithmetic means of refractive prediction errors for AS-OCTB and OCTB were -0.23 ± 0.40 D and -0.08 ± 0.35 D, respectively. In the Barrett UII formula, the arithmetic means of refractive prediction errors for AS-OCTB and OCTB were -0.02 ± 0.38 D and 0.11 ± 0.36 D, respectively. AS-OCTB showed significantly larger refractive prediction error toward myopia than OCTB in all three formulas (P <0.0001). CONCLUSION The refractive prediction error using AS-OCTB showed a small difference from that using OCTB. While clinically comparable, the two methods could drive meaningful differences in IOL selection.
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Affiliation(s)
- Yukihito Kato
- Chukyo Eye Clinic, Nagoya, Japan Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan Department of Ophthalmology, Japan Community Healthcare Organization, Chukyo Hospital, Nagoya, Japan
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Mini-Scleral Lenses for Correction of Refractive Errors After Radial Keratotomy. Eye Contact Lens 2018; 44 Suppl 2:S164-S168. [DOI: 10.1097/icl.0000000000000437] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Background The topography of corneas after penetrating keratoplasty is highly variable. We classify the topography into five groups. Methods We performed videokeratography on 45 clear compact penetrating keratoplasties, with all sutures removed. Three ophthalmologists classified the keratographs independently into five previously defined topographic groups, based on the pattern of the normalized color-coded videokeratograph. Results The five topographic patterns included: prolate bow tie, 14 (30%); oblate bow tie, 14 (30%); mixed prolate and oblate bow tie, 8 (17%); asymmetric, 3 (9%); and steep/flat, 6 (14%). The three ophthalmologists agreed in their initial classification in 87% of the cases and after discussion, in 96%. Conclusion The topography of the cornea after penetrating keratoplasty can be classified into five qualitative groups by trained observers, with good clinical reliability.
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Affiliation(s)
- O Ibrahim
- Department of Ophthalmology, Emory University, Atlanta, Georgia, USA
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Geggel HS. Intraocular Lens Power Selection after Radial Keratotomy: Topography, Manual, and IOLMaster Keratometry Results Using Haigis Formulas. Ophthalmology 2015; 122:897-902. [PMID: 25601534 DOI: 10.1016/j.ophtha.2014.12.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To compare final spherical equivalent (SE) refractions in patients who previously underwent radial keratotomy (RK) undergoing routine cataract surgery using keratometry (K) values from the Tomey (Topographic Modeling System [TMS]; Tomey Corp., Phoenix, AZ) Placido topographer, manual keratometer, and IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) keratometer using the Haigis formulas. DESIGN Retrospective case series. SUBJECTS A total of 26 RK eyes (20 patients) with a minimum of 3 months postoperative follow-up. METHODS The following K values were evaluated: TMS topography (flattest K within first 9 rings, average K, minimum K), manual K, IOLMaster K. The final refractive goal was -0.50 diopters (D) for all eyes. The Haigis formula with target refraction -0.50 D was used. In addition, because of observed hyperopic overcorrections, IOLMaster K with the Haigis formula set to -1.00 D but with a final refractive goal of -0.50 D was also tested. The Haigis-L formula using IOLMaster K values was separately evaluated. MAIN OUTCOME MEASURES Mean final SE refraction, percent final SE within ideal (-0.12 to -1.00 D), acceptable (0.25 to -1.50 D), or unacceptable (<-1.50 or >0.25 D) range and within ±0.50 D and ±1.00 D of the intended result. RESULTS Best results with minimal overcorrections were achieved with TMS flattest K (mean -0.68±0.60 D, 73% within ±0.50 D, and 88% within ±1.00 D of the surgical goal) and IOLMaster K set for target -1.00 D (mean -0.66±0.61 D, 69% within ±0.50 D, and 88% within ±1.00 D of the surgical goal). Other values produced more hyperopic (manual, IOLMaster K set for target -0.50 D, average topography) or higher myopic (minimum topography, Haigis-L) results. CONCLUSIONS For simplicity, using the IOLMaster K values combined with the Haigis formula set for target refraction -1.00 D produces acceptable results aiming for -0.50 D final SE refractions in former RK patients undergoing routine cataract surgery.
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Corneal Topographic Analysis of Patients With Mooren Ulcer Using 3-Dimensional Anterior Segment Optical Coherence Tomography. Cornea 2015; 34:54-9. [DOI: 10.1097/ico.0000000000000237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Hayashi K, Hayashi H. Long-term changes in corneal surface configuration after penetrating keratoplasty. Am J Ophthalmol 2006; 141:241-247. [PMID: 16458675 DOI: 10.1016/j.ajo.2005.08.062] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 08/25/2005] [Accepted: 08/25/2005] [Indexed: 11/23/2022]
Abstract
PURPOSE To examine the long-term longitudinal changes in corneal surface configuration as determined by Fourier series harmonic analysis of videokeratography data and of visual acuity and refraction after penetrating keratoplasty (PK). DESIGN Interventional case series. METHODS One hundred thirty eyes of 130 consecutive patients who were scheduled for PK using 16 interrupted 10-0 nylon sutures were recruited. Spherical equivalent power, regular astigmatism component, irregular astigmatism (asymmetry and higher-order irregularity) component of the central cornea as determined by Fourier analysis of videokeragraphic data, spectacle-corrected visual acuity, and spherical equivalent were examined at 1 week, and at 1, 3, 6, 9, 12, 18, and 24 months after PK. RESULTS Spherical equivalent power increased considerably for up to 1 month after PK, but thereafter showed no further appreciable change up to the final follow-up at 24 months. The regular astigmatism component decreased markedly for up to 6 months after PK, while the total irregular astigmatism (sum of the asymmetry and higher-order irregularity) component decreased considerably up to approximately 3 months, and then these showed no further relevant change for up to 24 months. Spectacle-corrected visual acuity also improved markedly until approximately 3 months after PK, after which it was virtually stable. Furthermore, important correlations were found between regular and irregular astigmatism and the spectacle-corrected visual acuity. CONCLUSIONS Corneal surface configuration after PK appears to be stable by approximately 6 months after PK, concurrent with postkeratoplasty stabilization of visual acuity.
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Affiliation(s)
- Ken Hayashi
- Hayashi Eye Hospital, and the Department of Ophthalmology, School of Medicine, Fukuoka University, Japan.
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Sharma V, Sharma N, Vajpayee RB, Titiyal JS, Sinha R. Study of corneal topographic patterns with single continuous suturing techniques in penetrating keratoplasty. Cornea 2003; 22:5-9. [PMID: 12502939 DOI: 10.1097/00003226-200301000-00002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To study the corneal topographic patterns following three different types of single continuous suturing techniques in penetrating keratoplasty. METHODS One hundred forty-eight maps obtained from 40 patients who underwent penetrating keratoplasty with single continuous suturing were retrospectively analyzed at a tertiary eye care center. The videokeratograph maps were obtained on the Eye Sys System 2000 at 1, 3, and 6 months after surgery. Suture adjustment was done for cases with astigmatism greater than 3 diopters, and maps were also obtained after suture adjustment. The maps were classified according to the corneal profile and the astigmatic pattern seen in the topographic maps. RESULTS Combined prolate patterns were seen most frequently, and their proportion was significantly higher at 1 month ( p= 0.009), 3 months ( p= 0.0004), and 6 months ( p= 0.0008). The simulated keratometric astigmatism was significantly higher in the prolate group compared with the other groups at 1 month ( p= 0.0021). However, all the topographic patterns showed comparable magnitude of astigmatism after suture adjustment and at 3 and 6 months. The antitorque suturing technique showed a higher proportion of prolate maps compared with the other suturing techniques. CONCLUSIONS Prolate patterns of the cornea are the most frequently seen patterns after single continuous suturing, which is the normal physiological pattern of the cornea. The initial astigmatism is higher in the prolate pattern, which can be successfully reduced with suture adjustment.
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Affiliation(s)
- Vidushi Sharma
- Dr. Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
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Maeda N, Sato S, Watanabe H, Inoue Y, Fujikado T, Shimomura Y, Tano Y. Prediction of letter contrast sensitivity using videokeratographic indices. Am J Ophthalmol 2000; 129:759-63. [PMID: 10926985 DOI: 10.1016/s0002-9394(00)00380-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To analyze the relationship between corneal topography and letter contrast sensitivity. METHOD Experiments were conducted on 59 eyes of 51 patients who had best spectacle-corrected visual acuity of 20/20 or better and no ocular pathology except for the corneal shape. Thirty-nine eyes had an abnormal topographic pattern resulting from keratoconus, and the other 20 eyes showed a normal topographic pattern. Videokeratography was performed with the TMS-2 videokeratoscope, and the surface regularity index, surface asymmetry index, and coefficient of variation of power were obtained for each subject. Letter contrast sensitivity was measured with the CSV-1000LV with spectacle correction. The correlation between the number of correct letters and topographic indices was calculated. RESULTS The abnormal topography group had a significantly greater loss of letter contrast sensitivity (median = 20 letters) than the normal control (median = 23 letters; P =.0001). There were statistically significant correlations between number of correct letters and the coefficient of variation of power (r = -.77; P =. 001), number of correct letters and surface regularity index (r = -. 76, P =.001), and the number of correct letters and surface asymmetry index (r = -.64; P =.001). The linear regression equation between number of correct letters and the coefficient of variation of power was the number of correct letters = -0.05 x the coefficient of variation of power + 23.2. CONCLUSIONS Our results suggest that subtle visual deteriorations, which are barely detected by contrast sensitivity testing, can be predicted objectively by the corneal topographic indices.
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Affiliation(s)
- N Maeda
- Department of Ophthalmology, Osaka University Medical School, Suita, Japan.
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Brahma A, Ridgway A, Tullo A, Boulton M, Ireland G, Bagley S, Carrington L. Centration of donor trephination in human corneal transplantation. Cornea 2000; 19:325-8. [PMID: 10832692 DOI: 10.1097/00003226-200005000-00013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To develop and evaluate a new method to quantify centration of the trephined donor cornea relative to the limbus. METHODS After human donor corneas were trephined for penetrating keratoplasty, the remaining corneoscleral discs were stained and subjected to image analysis. The centration of the excised donor cornea relative to the limbus was calculated by measuring their centroids from the "captured" images. RESULTS Fifty-two corneoscleral discs were analyzed. The average deviation from the centre was 0.32 mm (SD, 0.18 mm). Neither surgeon nor the type of trephine significantly influenced the mean centroid deviation. CONCLUSION We have developed and evaluated a method to quantify centration of human donor cornea. In a small series, decentration did not correlate significantly with either the surgeon or the trephine.
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Affiliation(s)
- A Brahma
- School of Biological Sciences, Manchester University, Royal Eye Hospital, UK
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Karabatsas CH, Cook SD, Sparrow JM. Proposed classification for topographic patterns seen after penetrating keratoplasty. Br J Ophthalmol 1999; 83:403-9. [PMID: 10434860 PMCID: PMC1722997 DOI: 10.1136/bjo.83.4.403] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIMS To create a clinically useful classification for post-keratoplasty corneas based on corneal topography. METHODS A total of 360 topographic maps obtained with the TMS-1, from 95 eyes that had undergone penetrating keratoplasty (PKP), were reviewed independently by two examiners in a masked fashion, and were categorised according to a proposed classification scheme. RESULTS A high interobserver agreement (88% in the first categorisation) was achieved. At 12 months post-PKP, a regular astigmatic pattern was observed in 20/85 cases (24%). This was subclassified as oval in three cases (4%), oblate symmetric bow tie in six cases (7%), prolate asymmetric bow tie in six cases (7%), and oblate asymmetric bow tie in five cases (6%). An irregular astigmatic pattern was observed in 61/85 cases (72%), subclassified as prolate irregular in five cases (6%), oblate irregular in four cases (5%), mixed in seven cases (8%), steep/flat in 11 cases (13%), localised steepness in 16 cases (19%), and triple pattern in three cases (4%). Regular astigmatic patterns were associated with significantly higher astigmatism measurements. The surface asymmetry index was significantly lower in the regular astigmatic patterns. CONCLUSIONS In post-PKP corneas, the prevalence of irregular astigmatism is about double that of regular astigmatism, with a trend for increase of the irregular patterns over time.
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Maeda N, Klyce SD, Tano Y. Detection and classification of mild irregular astigmatism in patients with good visual acuity. Surv Ophthalmol 1998; 43:53-8. [PMID: 9716193 DOI: 10.1016/s0039-6257(98)00006-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Videokeratography has been available for a decade, and this test is essential for determining the presence and type of irregular corneal astigmatism. Three eyes diagnosed with myopic astigmatism and considered good candidates for refractive surgery with conventional examination were studied. Color-coded maps with videokeratography showed regular astigmatism in one eye and the existence of irregular astigmatism in two eyes. Videokeratography showed that one of these eyes had a keratoconus suspect pattern and the second showed a pattern consistent with pellucid marginal degeneration. Videokeratography can detect and classify irregular astigmatism in cases where routine examination shows no abnormal findings.
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Affiliation(s)
- N Maeda
- Department of Ophthalmology, Osaka University Medical School, Yamadaoka, Suita, Japan
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Becker HH, Eisenberg DL, Wang N, Steinert RF, Schuman JS. Radial keratotomy increases outflow facility in the porcine eye in vitro. Curr Eye Res 1997; 16:1193-7. [PMID: 9426950 DOI: 10.1076/ceyr.16.12.1193.5027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE To investigate the biomechanical effect induced by radial keratotomy on outflow facility in paired, enucleated whole porcine eyes. METHODS Freshly enucleated porcine eyes were perfused at a constant pressure of 10 mm Hg. Radial keratotomy (RK), with a 3.5 mm central clear zone and eight radial incisions, was performed using a diamond knife with the blade length set at 100% of the paracentral corneal thickness, as measured by pachymetry. The fellow eye of each pair received sham RK as a control. RESULTS Seven pairs of eyes were perfused (RK group n = 7, control n = 7). There was no significant difference in the mean baseline of outflow facility between the paired experimental and control eyes preoperatively (p = 0.5). After RK, outflow facility increased by 46% (p < 0.001) in the treatment group, compared to a 7% (p < 0.04) increase in the control group, resulting in a 39% increase in outflow facility attributed to RK (p < 0.001). CONCLUSIONS Radial keratotomy produced a statistically significant acute increase in outflow facility in freshly enucleated porcine eyes. We believe that this increase results from steepening of the peripheral corneal curvature and the concomitant stretching of the iridocorneal angle. Further studies are needed to evaluate this effect in human eyes and in vivo.
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Affiliation(s)
- H H Becker
- New England Eye Center, New England Medical Center, Tufts University School of Medicine, Boston, MA, USA
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Dierick HG, Van Mellaert CE, Missotten L. Topography of Rabbit Corneas after Photorefractive Keratectomy for Hyperopia Using Airborne Rotational Masks. J Refract Surg 1996; 12:774-82. [PMID: 8970024 DOI: 10.3928/1081-597x-19961101-09] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To determine the long-term outcome of photorefractive keratectomy (PRK) for hyperopia on the rabbit cornea using ablation profiles with a smooth transition zone. METHODS Two profiles were ablated by means of an excimer laser and rotational masks, each profile on four rabbit eyes. Corrections of +10 diopters (D) were planned in all operations. The right eye was treated with a 4-mm optical zone and a 2-mm transition zone (4-mm/8-mm profile), the left eye with a 4-mm ablation and a 1-mm transition zone (4-mm/6-mm profile). Corneal topography was measured with an EyeSys videokeratoscope at 3, 10, 20, 30, 40, 50, 65, 75 and 120 weeks postoperatively. RESULTS After more than 2 years the axial power-not corrected for the physiologic flattening of the corneas-showed a residual steepening of +3.60 (+/-3.90) D for the right eyes and +3.9 (+/-2.8) D for the left eyes. The diameter of the topographic optical zone was equal to or smaller than the innermost mire. The power started to decrease paracentrally, giving the profile graph of the power a characteristic peak pattern. The flat transition zone, typical of PRK for hyperopia, could be recognized on the Placido images as a characteristic broadening of the midperipheral rings. The axial power map and the power profile did not show this flattening in the transition zone. CONCLUSION A steepening of the central cornea by PRK is possible. The diameter of the topographic optical zone of homogeneous power is smaller than induced, increasing considerably the asphericity of the central cornea. The 4-mm/8-mm ablation profiles did not give a larger diameter topographic optical zone nor less regression than the 4-mm/6-mm ablation profiles. The videokeratoscope makes errors in measuring axial power of mixed convex-concave surfaces.
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Affiliation(s)
- H G Dierick
- Excimer Study Group, St Vicentius Ziekenhuis, Antwerpen, Belgium
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Harto MA, Maldonado MJ, Cisneros AL, Perez-Torregrosa VT, Menezo JL. Comparison of Intersecting Trapezoidal Keratotomy and Arcuate Transverse Keratotomy in the Correction of High Astigmatism. J Refract Surg 1996; 12:585-94. [PMID: 8871859 DOI: 10.3928/1081-597x-19960701-10] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND High astigmatism can be corrected using trapezoidal or arcuate transverse keratotomies. Videokeratography enables qualitative evaluation of the corneal topography. METHODS Fifty-five eyes of 41 patients presenting with high astigmatism after penetrating keratoplasty or naturally occurring astigmatism (mean, 6.29 diopters [D]; range, 3.00 to 16.00 D) underwent correction using either intersecting trapezoidal or arcuate transverse keratotomies. Corneal topographic maps were analyzed and classified into keratographic patterns. Mean follow up was 3 years (range, 1 to 6 years). RESULTS The mean net decrease in refractive astigmatism was 3.60 D (52.7% reduction). The flattening/steepening ratio was on average higher for intersecting trapezoidal keratotomy (7.26 for astigmatism after penetrating keratoplasty and 8.31 for naturally occurring astigmatism) than for arcuate transverse keratotomy (.98 in astigmatism after penetrating keratoplasty and 1.76 in naturally occurring astigmatism). Accordingly, intersecting trapezoidal keratotomy tended to produce a hyperopic shift in the spherical equivalent refraction (mean hyperopic shift, 2.65 and .56 D, respectively). The mean vector-corrected change of refractive astigmatism after intersecting trapezoidal keratotomy was 88.8% in naturally occurring (n = 21 eyes) and 70.3% in penetrating keratoplasty astigmatism (n = 13). Arcuate transverse incisions corrected on average 79.9% of naturally occurring (n = 13) and 60.8% of penetrating keratoplasty astigmatism (n = 8). Videokeratography showed the asymmetric bowtie pattern as the most frequent pattern for both procedures. Intersecting trapezoidal keratotomy was characterized by relatively higher incidences of polygonal and irregular patterns. Arcuate transverse incisions caused less wound healing defects and glare than intersecting trapezoidal keratotomy. CONCLUSIONS Both intersecting trapezoidal keratotomy and arcuate transverse incisions effectively reduced high naturally occurring astigmatism and astigmatism after penetrating keratoplasty. However, greater corneal surface irregularity and more complications were seen following intersecting trapezoidal keratotomy. Trapezoidal keratotomy should not be used unless a large decrease of myopia is needed, and then a nonintersecting technique is preferable.
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Affiliation(s)
- M A Harto
- Department of Ophthalmology, La Fe University Hospital, Valencia, Spain
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Celikkol L, Pavlopoulos G, Weinstein B, Celikkol G, Feldman ST. Calculation of intraocular lens power after radial keratotomy with computerized videokeratography. Am J Ophthalmol 1995; 120:739-50. [PMID: 8540547 DOI: 10.1016/s0002-9394(14)72727-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
PURPOSE Because standard methods to determine intraocular lens power are not adequate in eyes that have had radial keratotomy, we undertook this study to evaluate the corneal power derived from computerized videokeratography for use in intraocular lens power calculations. METHODS We examined four eyes of three patients who had radial keratotomy and who underwent phacoemulsification cataract surgery with implantation of a posterior chamber intraocular lens. We used a computerized videokeratography-derived corneal curvature value in the Holladay formula for intraocular lens calculations. We determined the ideal intraocular lens power and the keratometric value that would have led to the ideal intraocular lens power from the postoperative refraction at 6.1 +/- 1.1 months after cataract extraction. The ideal keratometric value was compared with the keratometric values derived from computerized videokeratography, standard keratometry, contact lens overrefraction, and refractions before and after radial keratotomy. RESULTS The postoperative refraction at approximately six months averaged -0.32 +/- 0.63 diopter (range, -0.88 to +0.75 diopter) different than the aim. The mean power in ring 3, which was the closest keratometric value to the ideal, disclosed only 0.09 +/- 0.73 diopter and -0.10 +/- 0.72 diopter of deviation from the ideal keratometric and intraocular lens powers, respectively. One to two weeks after phacoemulsification cataract surgery with implantation of a posterior chamber intraocular lens, the videokeratographic differential map disclosed steepening at the wound site with variable regression by six months in all patients. CONCLUSION Results suggest that, after radial keratotomy, using the keratometric value derived from computerized videokeratography in intraocular lens calculations is more accurate than using keratometric values measured by routine methods.
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Affiliation(s)
- L Celikkol
- Department of Ophthalmology, University of California, School of Medicine, San Diego, La Jolla 92093-0684, USA
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Cohen KL, Tripoli NK, Holmgren DE, Coggins JM. Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope. Am J Ophthalmol 1995; 119:723-32. [PMID: 7785685 DOI: 10.1016/s0002-9394(14)72776-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PURPOSE The two purposes of this study were (a) to assess the accuracy with which a keratoscope, the Topographic Modeling System (TMS-1), calculated the heights and powers of rotationally symmetric, radially aspheric test surfaces and (b) to determine whether the TMS-1 used an axial solution for radius of curvature to determine the power of a sphere that would produce the same semichord as would the test surface on a keratograph. METHODS The TMS-1 heights and powers were studied for four test surfaces that had radial profiles similar to those of normal corneas. The powers of the surfaces were calculated from the local radius of curvature derived from the surfaces' manufacturing formulas. The heights and powers that would result from an axial solution were calculated in a TMS-1 simulator. TMS-1 data were compared with data from the surfaces' formulas and with data from the simulation. RESULTS The TMS-1 data were almost identical to the heights and powers calculated from the simulated axial solution. The TMS-1 data were similar to the heights and powers calculated from the mathematical formulas from the apex to 2 mm from the apex but differed by up to 85 microns of height and 10 diopters of power in the periphery. CONCLUSIONS The TMS-1 appeared to use the axial solution that does not calculate power from local radius of curvature. Clinicians should use caution when inferring corneal shape from power maps based on an axial solution, especially outside the central 2-mm radius of a normal cornea, because such power does not depict corneal curvature.
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Affiliation(s)
- K L Cohen
- Department of Ophthalmology, University of North Carolina at Chapel Hill, USA
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Dana MR, Viana MA, Mori MT, Chandler JW, McMahon TT. Dynamic shifts in corneal topography after radial and transverse keratotomy. Ophthalmology 1994; 101:1818-26. [PMID: 7800363 DOI: 10.1016/s0161-6420(94)31095-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
PURPOSE The authors aimed to quantitate the dynamic patterns of change in corneal topography after multistaged radial and transverse keratotomy using digitized video-keratography. METHODS Single and paired radial and transverse keratotomies, with videokeratoscopy between each stage and at the end of the procedure, were performed on fresh animal cadaver eyes using an artificial orbit system. RESULTS All incisions led to central flattening. A single radial keratotomy caused flattening adjacent to the incision, and steepening 180 degrees away. A paired radial keratotomy caused increased flattening in the meridian of the incisions, and less flattening 90 degrees away. A single transverse incision caused steepening adjacent to the incision and diffuse flattening elsewhere. A paired transverse incision caused flattening near the optical center along the meridian bisecting the incisions and steepening 90 degrees away. CONCLUSION The authors have demonstrated that computerized videokeratography can be used successfully to systematically quantitate dioptric shifts in multiple hemimeridians and measurement zone diameters after refractive surgery.
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Affiliation(s)
- M R Dana
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, UIC Eye Center 60612
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Binder PS. Radial Keratotomy and Excimer Laser Photorefractive Keratectomy for the Correction of Myopia. J Refract Surg 1994. [DOI: 10.3928/1081-597x-19940701-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Affiliation(s)
- D V Gangadhar
- Department of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston 02114
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Charpentier DY, Nguyen-Khoa JL, Duplessix M, Colin J, Denis P. Radial Thermokeratoplasty Is Inadequate for Overcorrection Following Radial Keratotomy. J Refract Surg 1994. [DOI: 10.3928/1081-597x-19940101-08] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Saragoussi JJ, Pouliquen YJM. Does the Progressive Increasing Effect of Radial Keratotomy (Hyperopic Shift) Correlate With Undetected Early Keratoconus? J Refract Surg 1994. [DOI: 10.3928/1081-597x-19940101-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Sastry SM, Sperduto RD, Waring GO, Remaley NA, Lynn MJ, Blanco E, Miller DN. Radial Keratotomy Does Not Affect Intraocular Pressure. J Refract Surg 1993. [DOI: 10.3928/1081-597x-19931101-10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Khong AM, Mannis MJ, Plotnik RD, Johnson CA. Computerized topographic analysis of the healing graft after penetrating keratoplasty for keratoconus. Am J Ophthalmol 1993; 115:209-15. [PMID: 8430730 DOI: 10.1016/s0002-9394(14)73925-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
After penetrating keratoplasty, visual rehabilitation can be slow and is largely a function of corneal surface configuration. Computerized topographic analysis allows the detailed study of corneal surface factors that determine the optical function of the graft. We performed a prospective, longitudinal study of eight patients with keratoconus by using computerized topographic analysis to determine the rate and pattern of postoperative surface normalization and stabilization. Study data included Snellen visual acuity, contrast sensitivity function, central keratometry, photokeratoscopy, and computerized topographic analysis. Data were collected preoperatively and at one week, one month, two months, three months, and six months postoperatively. Results demonstrate that the greatest configurational changes both topographically and functionally occur in the first month after keratoplasty. The computer-generated surface asymmetry index and the surface regularity index correlated well with improvement in Snellen visual acuity measurements. Contrast sensitivity function was depressed initially but improved to well above preoperative values by one month postoperatively and paralleled the improvement in the surface indices and visual acuity. The axis of astigmatism stabilized by one month postoperatively. Our data indicate that topographic analysis provides a good indication of the rate and course of optical stabilization during the early healing process after keratoplasty and correlates well with visual function in the otherwise normal eye.
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Affiliation(s)
- A M Khong
- Department of Ophthalmology, University of California, Davis, Sacramento
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Russell GE, Bergmanson JPG, Barbeito R, Cross WD. Differences Between Objective and Subjective Refractions After Radial Keratotomy. J Refract Surg 1992. [DOI: 10.3928/1081-597x-19920701-09] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Rosen WJ, Mannis M, Brandt JD. The Effect of Trabeculectomy on Corneal Topography. Ophthalmic Surg Lasers Imaging Retina 1992. [DOI: 10.3928/1542-8877-19920601-07] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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