Haigis公式预测准分子激光原位角膜磨镶术术后人工晶状体度数的准确性

目的评价Haigis公式预测准分子激光原位角膜磨镶术（laser in situ keratomileusis,LASIK）术后的人工晶状体度数的准确性。方法通过理论性计算,比较不同公式的LASIK手术前后等效人工晶状体度数的变化率。LASIK手术患者31例（59眼）,眼轴〈28mm。分别用Haigis、Holladay I、SRK/T公式计算LASIK手术前后等效人工晶状体度数的变化率,用SPSS统计软件进行统计学分析。结果Haigis、Holladay I、SRK/T公式计算LASIK手术前后等效眼屈光力的人工晶状体度数的变化率分别为1.01±0.01、0.96±0.02和0.94±0.02,三组之间两两配对t检验,P值均等于0.000。Haigis、Holladay I、SRK/T公式的LASIK手术前后等效人工晶状体度数误差在±0.5D以内的准确率分别为79.7%、11.9%和1.7%,误差在±1.0D的分别为100%、68.4%和27.1%。Haigis公式计算LASIK手术前后等效人工晶状体度数的差值随角膜屈光矫正值的增大而增大,校正公式为△D=-0.267-0.114×△SEQSP。结论Haigis公式是比较适合于LASIK术后白内障的人工晶状体计算公式,与Holladay I和SRK/T公式相比,具有较好的准确性。     

Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis

PURPOSE: To study the accuracy and predictability of intraocular lens (IOL) power calculation in eyes that had laser in situ keratomileusis (LASIK). SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHODS: Refractive outcomes in 6 cataract surgery and lensectomy eyes after previous LASIK were analyzed retrospectively. Target refractions based on measured and refraction-derived keratometric values were compared with postoperative achieved refractions. Differences between target refractions calculated using 5 IOL formulas and 2 A-constants and achieved refractions were also compared. RESULTS: The refractive error of IOL power calculation in postoperative LASIK eyes was significantly reduced when refraction-derived keratometric values were used for IOL power calculation. Persistent residual hyperopia still occurred in some cases; this was corrected by hyperopic LASIK. Refractive results appeared more accurate and predictable when the Holladay 2 or Binkhorst 2 formula was used for IOL power calculation. CONCLUSION: Hyperopic error after cataract surgery in post-LASIK eyes was significantly reduced by using refraction-derived keratometric values for IOL power calculation. Persistent hyperopic error was corrected by hyperopic LASIK.     

Correcting the corneal power measurements for intraocular lens power calculations after myopic laser in situ keratomileusis

PURPOSE: To describe and evaluate a refraction-derived method and a clinically derived method to calculate the correct corneal power for intraocular lens (IOL) power calculations after laser in situ keratomileusis (LASIK) and to compare the results to the commonly used history-derived method. DESIGN: Interventional case series. METHODS: Retrospective analysis of consecutive cases from clinical practice. Two hundred randomly selected eyes from 200 patients were evaluated before and after LASIK surgery. For each patient, we established the pre-LASIK and post-LASIK spectacle refraction, the pre-LASIK (Kpre) and post-LASIK K readings (Kpost). We then calculated for each case the pre- and post-LASIK refraction at the corneal plane and the amount of correction obtained by the refractive surgery (CRc). The cases were divided into two groups. Group I was used to derive the two formulas. The K values were calculated using the history-derived method (Kc.hd) in which Kc.hd = Kpre - CRc. Kc.hd was compared with Kpost. The average difference was 0.23 diopters for every diopter of myopia corrected. This value was used to calculate the corneal power using the refraction-derived method (Kc.rd) where Kc.rd = Kpost -0.23CRc. A regression equation was used to develop a clinically derived method (Kc.cd) where Kc.cd = 1.14Kpost -6.8. The values obtained with the two methods were compared with the Kc.hd values in group II to validate the results. RESULTS: Both Kc.rd and Kc.cd values correlated highly with Kc.hd when plotted on a scattergram (P <.001), and there was no statistically significant difference between the mean keratometric values (P >.5). CONCLUSIONS: The corneal power measurements for intraocular lens power calculations after LASIK need to be corrected to avoid hypermetropia after cataract surgery by either the history-derived method, the refraction-derived method, or the clinically derived method.     

Accurate intraocular lens power calculation after myopic laser in situ keratomileusis, bypassing corneal power

PURPOSE: To describe a novel method for calculating intraocular lens (IOL) power after myopic laser in situ keratomileusis (LASIK) without using the inaccuracies of the post-LASIK corneal power. SETTING: Department of Ophthalmology, Wake Forest University Eye Center, Wake Forest University School of Medicine, Winston Salem, North Carolina, USA. METHODS: This retrospective chart review comprised 9 eyes of 9 patients who had phacoemulsification after LASIK using our method for IOL calculation. This new method assumes the patient never had myopic LASIK to calculate IOL power and then targets the IOL at the pre-LASIK amount of myopia. The pre-LASIK keratometry values, pre-LASIK manifest refraction, and the current axial length are placed in the Holladay formula, bypassing the post-LASIK corneal power. In theory, assuming that the patient had satisfactory LASIK results, the correct IOL can then be determined. RESULTS: The mean spherical equivalent postoperative refraction was +0.03 diopter (D) +/- 0.42 (SD) (range -0.625 to +0.75 D). In all 9 eyes, our method consistently chose the most accurate and precise IOL compared with other methods. CONCLUSIONS: The new method of calculating IOL power after LASIK provided excellent results and the most accurate and precise results to date.     

Intraocular lens power calculations after laser in situ keratomileusis

PURPOSE: To compare the accuracy of several techniques for calculating intraocular lens (IOL) power after laser in situ keratomileusis (LASIK). METHODS: Retrospective review of 10 eyes from nine patients undergoing phacoemulsification after LASIK. Corneal power (K) was measured by manual keratometry (MK), refractive history (RH), contact lens overrefraction (CTL), videokeratography (VK), and an average of the refractive history and contact lens methods (AVG 2). Results were compared with the back-calculated K value generated by the Holladay IOL Consultant program. Age-matched patients undergoing phacoemulsification without previous refractive surgery served as controls. RESULTS: Mean spherical equivalent postoperative refraction was +0.21 diopter (D) (SD, 1.54; range, -2.25 to +2.25 D) for patients undergoing cataract extraction after LASIK versus -0.56 D (SD, 0.66; range, -2.375 to +0.5 D; p= 0.16) for controls. Thirty percent of cases versus 90% of controls were within 1 D ( p= 0.002) of emmetropia. Forty percent of cases versus no controls were more than 1 D hyperopic ( p= 0.08). The mean differences for each method compared with the back-calculated K values were MK, +0.82 D; VK, +1.24 D; RH, -0.76 D; CTL, +0.91 D; AVG 2, +0.08 D. The mean absolute deviations from the back-calculated K values were MK, 1.91 D; VK, 2.01 D; RH, 1.68 D; CTL, 1.62 D; AVG 2, 1.42 D. CONCLUSION: Significant refractive errors occurred with each of the methods investigated for determining IOL power after LASIK. RH, CL, or AVG 2 provided the most accurate results.     

No-history method of intraocular lens power calculation for cataract surgery after myopic laser in situ keratomileusis

PURPOSE: To prospectively evaluate the no-history method for intraocular lens (IOL) power calculation in 15 cataractous eyes that had previous myopic laser in situ keratomileusis (LASIK) and for which the pre-LASIK K-readings were not available. SETTING: Private practice, Lynwood, California, USA. METHODS: The predicted IOL power was calculated in each case. Also calculated were the mean arithmetic and absolute IOL predictor errors, range of the prediction errors, and number of eyes in which the error was within +/-1.00 diopter (D). RESULTS: The mean arithmetic IOL prediction error was -0.003 D +/- 0.63 (SD), and the mean absolute IOL prediction error was 0.55 +/- 0.31 D (range -0.89 to +1.05 D). Fourteen eyes (93.3%) were within +/-1.00 D. The results of the Shammas post-LASIK formula compared favorably to the results obtained with the optimized Holladay 1 (P = .42), Hoffer Q (P = .25), Haigis (P = .30), and Holladay 2 (P = .19) formulas and were better than the results obtained with the optimized SRK/T formula (P = .0005). CONCLUSION: The no-history method is a viable alternative for IOL power calculation after myopic LASIK when the refractive surgery data are not available.     

Phakic toric intraocular lens implantation after flap decentration in laser in situ keratomileusis

We describe a patient with flap decentration after laser in situ keratomileusis (LASIK) and subsequent phakic toric intraocular lens (IOL) implantation. A 19-year-old man with mixed astigmatism had LASIK in the left eye complicated by flap decentration. Laser ablation was abandoned and implantation of a phakic toric IOL was done. Ten months after IOL implantation, the uncorrected visual acuity in the left eye was 20/25 and best corrected visual acuity was 20/20 with +0.25 -0.50 x 90. Simulated keratometry values were 44.30@150 and 42.00@60 before LASIK and 45.00@150 and 41.90@60 after IOL implantation. Phakic toric IOL implantation may be adequate treatment for flap decentration after LASIK in cases of mixed astigmatism.     

Keratometry for intraocular lens power calculation using Orbscan II in eyes with laser in situ keratomileusis

PURPOSE: To compare the results of comeal keratometry after laser in situ keratomileusis (LASIK) obtained by the Gaussian optics formula and the clinical history method. METHODS: Sixty-one consecutive patients (121 eyes) who had undergone LASIK were recruited in this retrospective case-controlled study. The K-value obtained from the Gaussian optics formula (CalK) based on postoperative corneal topography by Orbscan II (Bausch & Lomb, Rochester, NY) and ultrasound pachymetry was compared with that obtained from the clinical history method (estK). Keratometry measured by these two methods was compared using the paired sample t test and Pearson correlation coefficient. RESULTS: A high correlation was noted between K-value obtained by the clinical history method and the Gaussian optics formula (R = 0.97, P < .001). The mean difference between the two methods is 0.13 diopters (P = .06). CONCLUSIONS: K reading derived from the Gaussian optics formula correlated closely to that obtained from the clinical history method and would be especially useful in patients with no preoperative LASIK treatment data.     

Reduction in intraocular pressure after laser in situ keratomileusis

PURPOSE: To investigate whether intraocular pressure (IOP) measured on the nasal side is affected after laser in situ keratomileusis (LASIK). SETTING: The Glaucoma Service, Dr. Hong's Eye Clinic, Seoul, Korea. METHODS: In 83 patients, IOP was prospectively measured with the Goldmann tonometer at the central (Tcenter) and nasal (Tnasal) areas of the cornea before and after LASIK. The Tcenter and Tnasal IOP between baseline and 1, 3, and 6 months postoperatively was compared. The correlation between ablation depth, amount of treatment, refractive change, and change in central corneal thickness and Tcenter change was evaluated. RESULTS: Six months after LASIK, Tcenter IOP decreased 3.9 mm Hg (25.2%) and Tnasal IOP decreased 2.0 mm Hg (12.7%) (P < .001, P = .02, respectively). The Tnasal measurement was 1.8 mm Hg higher than the Tcenter measurement (P < .001). Significant correlation between each corneal parameter and the Tcenter reduction at 1 month did not continue to 6 months (P > .05). CONCLUSION: At each follow-up, Tnasal IOP was statistically lower than at baseline, although the reduction was not as great as that of Tcenter IOP. A 2 to 3 mm Hg drop in Tnasal up to 6 months after LASIK should be expected. An alternative would be to measure IOP with the Tono-Pen on the nasal side to fit the tip to the relatively unchanged nasal side of the cornea.     

Changes in intraocular pressure after laser in situ keratomileusis

PURPOSE: To evaluate changes in intraocular pressure (IOP) measurements by Goldmann applanation tonometry after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the accuracy of Goldmann applanation tonometry measurements after LASIK in these eyes. METHODS: LASIK was performed on 166 eyes of 93 patients for correction of myopia and myopic astigmatism. Intraocular pressure was measured by Goldmann applanation tonometry at the central and temporal parts of the cornea before and at 1, 3, 6, and 12 months after LASIK. The amount of change in IOP was computed and its relation to different variables was evaluated by regression analysis. RESULTS: Intraocular pressure measured at the center of the cornea was reduced by a mean of 3.69 +/- 1.63 mmHg after LASIK. Multiple regression analysis showed that the decrease in IOP was related to the preoperative IOP and the change in central corneal thickness after LASIK. Measurements of IOP at the temporal part of the cornea were also reduced by a mean of 2.39 +/- 1.71 mmHg. There was wide variability in the amount of difference between the temporal and central measurements after LASIK (temporal measurements were higher than central by 0 to +4 mmHg). CONCLUSION: LASIK for myopia produced underestimation of IOP measured by Goldmann applanation tonometry at the central part of the cornea by a mean of 3.69 +/- 1.63 mmHg. The decrease of IOP was related to preoperative IOP and the change in central corneal thickness after LASIK. Temporal Goldmann applanation tonometry measurements, although decreased after LASIK, were less reliable.     

LASIK术后白内障手术植入的人工晶状体屈光度的预测

目的探讨LASIK术后,不同公式及不同的测算方法预测所需人工晶状体（IOL）屈光度的准确性。方法对27例近视（52眼）于LASIK手术前、后分别应用SRKⅡ公式、SRK／T公式、Holladay公式和Haigis公式计算将术眼矫正至正视眼所需的IOL屈光度,并应用F值计算与术眼原晶状体屈光力等值的IOL屈光度。并且术后应用OrbscanⅡ角膜地形图、IOLMaster测量获得的K值和临床病史法计算出的K值分别代人上述4种公式计算IOL屈光度。应用SPSS统计软件对数据进行统计学分析。结果低度近视者4种公式计算结果手术前、后比较,差异均无统计学意义（P〉0．05）;中、高度近视者4种公式计算结果LASIK术后均小于术前,差异有统计学意义（P〈0．01）,其中Haigis公式差值最小。中、低度近视者,LASIK术后OrbscanⅡ角膜地形图测量所得的K值与临床病史法获得的K值分别代人不同公式计算出的IOL屈光度比较,差异均无统计学意义（P〉0．05）;高度近视者,这两种方法获得的K值分别代人SRKⅡ、SRK／T、Haigis公式计算出的IOL屈光度比较,差异均有统计学意义（P〈0．05）,临床病史法相对较准确。结论对于中高度近视,LASIK手术后应用现有的IOL屈光度计算公式,其结果均偏小,但Haigis公式优于其他公式。对于高度近视最好选择临床病史法获得角膜K值。     

Photorefractive keratectomy or laser in situ keratomileusis for residual refractive error after phakic intraocular lens implantation

PURPOSE: To evaluate the results of combining phakic posterior chamber intraocular lens (IOL) implantation and excimer corneal surgery to treat high myopia or myopia with astigmatism. SETTING: Service d'Ophtalmologie, H?pital Purpan, University of Toulouse, Toulouse, France. METHODS: Thirty-two eyes of 28 patients with extreme myopia or myopia combined with astigmatism were treated by implantation of a phakic posterior chamber IOL. Residual refractive errors were treated no earlier than 6 weeks after IOL implantation by photorefractive keratectomy (PRK) in eyes with low refractive errors or by laser in situ keratomileusis (LASIK) in eyes with higher residual refractive errors. RESULTS: The mean preoperative spherical equivalent (SE) refraction was -18.7 diopters (D). The refractive astigmatism ranged from 0 to 3.5 D. After excimer laser treatment, the SE refraction ranged from -0.5 to -2.5 D and the refractive astigmatism, from 0 to 1.5 D in the PRK group. In the LASIK group, spherical ametropia ranged from -1.5 to +1.5 D and astigmatism, from 0 to 1.0 D. After excimer laser treatment, the uncorrected visual acuity improved in all eyes but a loss of 1 line of the corrected vision after IOL implantation occurred in 22.2% of PRK-treated eyes and in 13.6% of LASIK-treated eyes. CONCLUSIONS: Bioptic treatment of extreme myopia and myopia associated with astigmatism appears to be safer and more predictable than other methods of treatment.