Preoperative Corneal Curvature Research Articles

Refraction and topographic risk factors for early myopic regression after small-incision lenticule extraction surgery.

We sought to evaluate the topographic risk factors for early myopic regression after small-incision lenticule extraction (SMILE). A retrospective case‒control study was conducted, and individuals who underwent SMILE surgery were enrolled. Among them, 406 and 14 eyes were categorized into the nonregression and regression groups, respectively. The preoperative and postoperative parameters in the two groups were collected, including spherical refraction (SE), axial length (AXL) and topographic data. A generalized linear model was adopted to analyze the difference in each parameter between the two groups. After 6months, UCVA decreased in the regression group, and SE increased in the regression group (both P < 0.05). The increase in the CCT at the thinnest point (P = 0.044), flat corneal curvature (P = 0.012) and TCRP (P = 0.001) were significantly greater in the regression group. Regarding the risk factors for myopic regression, preoperative SE, preoperative sphere power, preoperative AXL, preoperative flat corneal curvature, preoperative SA, early postoperative SE, early postoperative sphere power, early postoperative AXL and early postoperative CCT difference were significantly greater in the regression group (all P < 0.05). The SE, sphere power, AXL, preoperative flat corneal curvature, preoperative SA, and postoperative CCT difference correlate with early myopic regression after SMILE.

A Comparative Study of the Effect of Femtosecond Laser-Assisted Cataract Surgery on Corneal Astigmatism in Post-LASIK Eyes and Virgin Eyes.

To evaluate and compare the effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes. Patients who underwent femtosecond laser-assisted cataract surgery were included in the study and categorized into two groups: Group A, consisting of patients with post-LASIK eyes, and Group B, consisting of patients with virgin eyes. Visual acuity, corneal astigmatism, and surgically induced astigmatism (SIA) were evaluated. Additionally, the correlation between SIA and preoperative corneal astigmatism, mean corneal curvature, and central corneal thickness was also analyzed. A total of 168 eyes were enrolled in this study, with 62 eyes in Group A and 106 eyes in Group B. Significant differences in corneal astigmatism and SIA were observed between the two groups in the early postoperative period following cataract surgery (P<0.05). However, there was no significant difference at 6 months postoperatively (P>0.05). Corneal astigmatism demonstrated an against-The-rule shift in both groups postoperatively. No significant correlation was identified between SIA and preoperative corneal astigmatism, corneal curvature or corneal thickness. Additionally, there was no significant difference observed between the two groups in terms of uncorrected distance visual acuity (UDVA) at 6 months postoperatively. The effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes was different in the early postoperative period. However, there was no significant difference at 6 months postoperatively. The post-LASIK eyes exhibited a delayed recovery compared to the virgin eyes.

Evaluation of the Effects of Myopic Astigmatism Correction and Anterior Corneal Curvature on Functional Optical Zone After SMILE.

To evaluate the influence of different degrees of myopic astigmatism correction and preoperative anterior corneal curvature on the functional optical zone (FOZ) following small incision lenticule extraction (SMILE). In this retrospective study, 68 patients (106 eyes) treated with SMILE were grouped according to myopic astigmatism correction: control (0.00 diopters [D]), moderate astigmatism (-0.50 to -2.00 D), and high astigmatism (> -2.00 D). The FOZ was measured and compared between the three groups for 3 months. Correlations between attempted correction, anterior corneal curvature, corneal aberrations, and the FOZ were analyzed. The preoperative mean treatment spherical equivalent was comparable among the three groups. The average FOZ was 5.06 ± 0.24 mm in the control group, 5.19 ± 0.25 mm in the moderate astigmatism group, and 5.35 ± 0.20 mm in the high astigmatism group The FOZ showed statistically significant differences among the three groups (P < .001), particularly between the high astigmatism group and the other two groups (P < .001 and .018). Correlation analysis showed that the total higher order aberrations, coma, and spherical aberration change were correlated with the FOZ (P < .001). Preoperative steep keratometry, average keratometry, and corneal astigmatism were significantly correlated with the FOZ (P < .05). The correlation remained after excluding the influence of attempted correction on the FOZ (P < .05). After adjusting for other risk factors using multiple linear regression analysis, there was still a significant positive association between preoperative steep keratometry and the FOZ (P < .001). Patients with higher myopic astigmatism achieved a larger FOZ and less induced horizontal coma than the control and moderate astigmatism groups. A larger FOZ after SMILE can be achieved in eyes with steeper keratometry. [J Refract Surg. 2023;39(2):135-141.].

Optimizing intraocular lens power calculation using adjusted conventional keratometry for cataract surgery combined with Descemet membrane endothelial keratoplasty

PurposeTo evaluate the utility of intraocular lens (IOL) power calculation using adjusted conventional keratometry (K) according to postoperative posterior to preoperative anterior corneal curvature radii (PPPA) ratio for eyes with Fuch’s dystrophy undergoing cataract surgery combined with Descemet membrane endothelial keratoplasty (triple DMEK).MethodsA fictitious refractive index (FRI) was determined (Pentacam HR®) based on the PPPA ratio in 50 eyes undergoing triple DMEK. Adjusted corneal power was calculated in every eye using adjusted K values: K values determined by the IOLMaster were converted to adjusted anterior corneal radius using the mean FRI. Posterior corneal radius was calculated using the mean PPPA ratio. Adjusted corneal power was determined based on the calculated corneal radii and thick lens formula. Refractive errors calculated using the Haigis, SRK/T, and HofferQ formulae based on the adjusted corneal power were compared with those based on conventional K measurements.ResultsCalculated PPPA ratio and FRI were 0.801 and 1.3271. Mean prediction error based on conventional K was in the hyperopic direction (Haigis: 0.84D; SRK/T: 0.74D; HofferQ: 0.74D) and significantly higher (P < 0.001) than that based on adjusted corneal power (0.18D, 0.22D, and 15D, respectively).When calculated according to adjusted corneal power, the percentage of eyes with a hyperopic shift > 0.5D fell significantly from 64 to 30% (Haigis), 62 to 36% (SRK/T), and 58 to 26% (HofferQ), respectively.ConclusionIOL power calculation based on adjusted corneal power can be used to reduce the risk of a hyperopic shift after triple DMEK and provides a more accurate refractive outcome than IOL power calculation using conventional K.

Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

PurposeTo investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.MethodsThis study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.ResultsOne month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).ConclusionsOne month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

Evaluation of the effect of preoperative corneal curvature on the successful formation of the big bubble formation in deep anterior lamellar keratoplasty for keratoconus

Background New approaches have been created to raise the chances of achieving big bubble (BB) in deep anterior lamellar keratoplasty (DALK); however, the BB formation is still uncertain in all cases. Other factors likely contribute to the success of bubble formation. Aim To evaluate the effect of preoperative curvature of the cornea on the success of BB formation in DALK for keratoconus. Design A prospective, comparative, nonrandomized study. Patients and methods The study was performed on 50 keratoconus patients. We compared the data of 25 patients who had successful type-1 bubble formation versus another 25 patients in whom the bubble formation failed. Both groups were compared regarding the keratometric readings recorded from the preoperative pentacam. Results The analysis showed statistically significant lower K1, K2, and Km values in the group where BB has been successfully achieved. We also found that lower K1 value was the only significant studied factor after the multivariate analysis. Conclusion Keratoconus patients with preoperative flatter corneas have slightly higher chances for successful BB formation during DALK surgery.

Effect of pterygium excision on mean corneal curvature.

Objective: To determine the difference in mean corneal curvatures before and after pterygium excision. Study Design: Quasi-experimental study. Setting: Department of Ophthalmology, Holy Family Hospital, Rawalpindi. Period: 1st January 2015 to 1st July 2015. Material &amp; Methods: 68 patients aged between 18 to 65 years were included in the study. Patients with history of ocular trauma, ocular surgery, glaucoma, anti-glaucoma treatment, allergy to steroids, pseudo pterygium, recurrent pterygium and presence of corneal abnormalities such as, scarring that might affect the astigmatic value were excluded. All patients underwent comprehensive ophthalmic examination by slit lamp and best corrected visual acuity and keratometric values were noted. Pterygium excision was done by a single surgeon. BCVA and keratometric readings were taken again after 2 weeks of pterygium excision. Results: Mean age was 37.60 ± 11.11 years. Out of these 68 patients, 44 (64.71%) were male and 24 (35.29%) were females. Mean pre-operative corneal curvature was 2.99 ± 0.69D and post-operative corneal curvature was 1.70 ± 0.40D with P-value of &lt;0.0001 which is statistically significant. Conclusion: This study concluded that pterygium excision brings significant change in corneal curvature in patients of pterygium induced astigmatism.

Assessing the validity of corneal power estimation using conventional keratometry for intraocular lens power calculation in eyes with Fuch\u2019s dystrophy undergoing Descemet membrane endothelial keratoplasty

PurposeThe present retrospective study was designed to test the hypothesis that the postoperative posterior to preoperative anterior corneal curvature radii (PPPA) ratio in eyes with Fuch’s dystrophy undergoing Descemet membrane endothelial keratoplasty (DMEK) is significantly different to the posterior to anterior corneal curvature radii (PA) ratio in virgin eyes and therefore renders conventional keratometry (K) and the corneal power derived by it invalid for intraocular lens (IOL) power calculation.MethodsMeasurement of corneal parameters was performed using Scheimpflug imaging (Pentacam HR, Oculus, Germany). In 125 eyes with Fuch’s dystrophy undergoing DMEK, a fictitious keratometer index was calculated based on the PPPA ratio. The preoperative and postoperative keratometer indices and PA ratios were also determined. Results were compared to those obtained in a control group consisting of 125 eyes without corneal pathologies. Calculated mean ratios and keratometer indices were then used to convert the anterior corneal radius in each eye before DMEK to postoperative posterior and total corneal power. To assess the most appropriate ratio and keratometer index, predicted and measured powers were compared using Bland-Altman plots.ResultsThe PPPA ratio determined in eyes with Fuch’s dystrophy undergoing DMEK was significantly different (P < 0.001) to the PA ratio in eyes without corneal pathologies. Using the mean PA ratio (0.822) and keratometer index (1.3283), calculated with the control group data to convert the anterior corneal radius before DMEK to power, leads to a significant (P < 0.001) underestimation of postoperative posterior negative corneal power (mean difference (∆ = − 0.14D ± 0.30) and overestimation of total corneal power (∆ = − 0.45D ± 1.08). The lowest prediction errors were found using the geometric mean PPPA ratio (0.806) and corresponding keratometer index (1.3273) to predict the postoperative posterior (∆ = − 0.01 ± 0.30) and total corneal powers (∆ = − 0.32D ± 1.08).ConclusionsCorneal power estimation using conventional K for IOL power calculation is invalid in eyes with Fuch’s dystrophy undergoing DMEK. To avoid an overestimation of corneal power and minimize the risk of a postoperative hyperopic shift, conventional K for IOL power calculation should be adjusted in eyes with Fuch’s dystrophy undergoing cataract surgery combined with DMEK. The fictitious PPPA ratio and keratometer index may guide further IOL power calculation methods to achieve this.

Predictors affecting myopic regression in \u2212\u20096.0D to \u2212\u200910.0D myopia after laser-assisted subepithelial keratomileusis and laser in situ keratomileusis flap creation with femtosecond laser-assisted or mechanical microkeratome-assisted

PurposeTo investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from − 6.0D to − 10.0D myopia.MethodsThis retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries.ResultsThe study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from − 6.0D to − 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (Kmax) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01).ConclusionsThe MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (Kmax), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from − 6.0D to − 10.0D.

Observational study on the impact of corneal power on refractive status of patients after small incision lenticule extraction surgery

Objective: To observe the change of refractive status and possible influencing factors for patients with different corneal power who underwent small incision lenticule extraction (SMILE) surgery. Methods: Prospective cohort study was performed for patients who underwent small incision lenticule extraction (SMILE) surgery at Daping Hospital and Research Institute of Surgery of Third Military Medical University between January and August 2016. The patients were divided into 3 groups according to their corneal power: low curvature group (K(1)≤41.00 D), common curvature group (41.00 D<K(1) and K(2)< 46.00 D), and high curvature group (K(2) ≥ 46.00 D). Preoperative and postoperative (1 day, 1 week, 1, 3 and 6 month) ophthalmic examination results of the patients including uncorrected distance visual acuity (UCDVA), refractive status, intraocular pressure (IOP) and slip lamp microscope examination were recorded. Subjective refraction and Pentacam HR were detected at 6 month after operation so as to monitor the incidence of intraoperative and postoperative complications. The total corneal refractive power (TCRP) based on Ray Tracing technique was applied to evaluate the changes of corneal curvature before and after the surgery. Power vector analysis was applied to evaluate the refraction status based on preoperative and postoperative corneal topography. At 6 months postoperatively, Hotelling t(2) test was applied to compare the refractive status among the groups, and multiple linear regression was applied to analyze the potential influencing factors of under-correction/over-correction. Results: Fifty-four patients (108 eyes) were enrolled, among which 34 were male (68 eyes) and 20 were female (40 eyes). The 3 groups had the same sample size (18 patients and 36 eyes). The low curvature group was featured with youngest average age [(22±4) years, χ(2)=8.94, P<0.05], largest male patients proportion (15/18, χ(2)=11.20, P<0.01) and largest average pupil diameter [(3.26±0.36) mm, F=4.83, P<0.05], as compared to the other 2 groups. The incidence of severe OBL (25/36) was significantly higher in the high curvature group (χ(2)=65.06, P<0.01). All patients showed no diminution of vision and their UCDVA averaged 5.1 at 6 months postoperatively, however patients with low curvature were slightly "under-corrected" in 1-mm and 2-mm zones (Error values<0). The preoperative spherical equivalent (SE) and postoperative spherical aberration in 6-mm zone were the significant factors affecting the relationship between preoperative corneal curvature and postoperative refractive status (r=0.392, 2.745, P<0.05). Conclusions: SMILE is safe and effective for patients with both low and high curvature, but the incidence of intraoperative OBL is significantly higher in high curvature group. Patients with low curvature were slightly "under-corrected" in 1-mm and 2-mm zones, which may imply that the design of the lenticule may be aspheric and that the cornea reshaping process of younger patients may be of particular characteristics. (Chin J Ophthalmol, 2018, 54: 48-54).

Comparison of SRK/T and Haigis formulae in the prediction of refractive outcome after phacoemulsification

Purpose To compare the accuracy of SRK/T and Haigis formulae used for intraocular lens (IOL) power calculation by a partial coherence interferometer in patients undergoing phacoemulsification surgery. Patients and methods A prospective interventional clinical study included 70 eyes of 60 patients, who underwent uncomplicated phacoemulsification with IOL implantation from October 2015 to December 2017. Preoperative axial length (AL), corneal curvature (keratometry), and preoperative anterior chamber depth (preoperative ACD) were measured using Nidek AL-scan optical biometer and the IOL power was determined using both SRK/T and Haigis formulae. The difference between the predicted value and the postoperative spherical equivalent was calculated for both the formulae by the end of the follow-up (3 months postoperatively). Results The mean errors of the two formulae were SRK/T: −0.225±0.61 D and Haigis: 0.171±0.68 D; the mean absolute errors of the two formulae were 0.534±0.36 and 0.533±0.44 D, respectively. There was no statistically significant difference between the mean error of the two formulas used in the overall performance, but was significant in eyes with an AL of more than 25 mm. The proportion of patients having a prediction error within ±0.50 D of SRK/T formula (54.29%) was comparable to those of Haigis (55.71%) and the prediction errors within ±1.0 D were 87.14 and 85.71%, respectively. There is a weak correlation between the mean AL, keratometry and the Haigis–SRK/T prediction differences (r 2=0.273). Conclusion The calculation of IOL power using SRK/T and Haigis formulae resulted in an accurate postoperative refraction. In long AL subcategory, the mean absolute error of Haigis was less compared with the SRK/T formula.

Changes in Corneal Power After Descemet Stripping Automated Endothelial Keratoplasty.

To examine the optical effects of Descemet stripping automated endothelial keratoplasty (DSAEK) by evaluating changes in anterior and posterior corneal curvatures and aberrations. Eighty-three eyes treated using DSAEK combined with cataract surgery (the DSAEK group) and 41 control eyes of healthy patients (the control group) were included. Patients were examined before and 1 year after surgery with autokeratometry and Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany). The preoperative posterior corneal curvature was estimated from the anterior corneal curvature. The mean intended postoperative refraction in the DSAEK group was -0.75 ± 0.62 diopters (D), which was statistically different from the achieved refraction of +0.50 ± 0.93 D at the 1-year follow-up (P < .001). The average biometry prediction error was a hyperopic shift of +1.27 ± 0.80 D. Anterior corneal power was significantly higher before than after DSAEK with a difference of -0.63 ± 0.68 D (P = .03) correlating significantly with the hyperopic change (r(2) = 0.23, P < .01). The posterior corneal power after DSAEK showed a significant steepening of -0.69 ± 0.38 D (P < .01) from the estimated preoperative power and a difference of -0.64 ± 0.38 D (P < .01) from the posterior corneal power in the control group. The change correlated significantly with the hyperopic change (r(2) = 0.10, P < .01). The combined changes in anterior and posterior keratometry increased the correlation coefficient to r(2) = 0.34 (P < .01). Significant differences were observed for total higher-order aberrations root mean square and coma root mean square after DSAEK compared to controls. No significant changes were observed in spherical aberration. The hyperopic shift in the DSAEK group can be explained by changes in anterior and posterior corneal surfaces. Spherical aberration was not changed by DSAEK, suggesting that aspherical intraocular lenses may be implanted on the same indications as in normal cataract surgery.

Venting incisions in DSAEK: implications for astigmatism, aberrations, visual acuity, and graft detachment

To evaluate the impact of venting incisions on the best corrected visual acuity (BCVA), astigmatism, aberrations, and risk of graft detachment in Descemet stripping automated keratoplasty (DSAEK). This was a retrospective, comparative, consecutive case series of DSAEK procedures performed with (n = 266) and without (n = 110) venting incisions. Patients were treated with DSAEK for Fuchs' endothelial dystrophy at Aarhus University Hospital between 2011 and 2013. Data included preoperative keratometry and postoperative BCVA, subjective astigmatism, and Pentacam® HR tomography with corneal front surface (CFS) aberrations at 1 to 2 years of follow-up. Numbers of triple procedures (concurrent cataract surgery) and post-operative graft detachments were also noted. The venting and non-venting groups were compared by the data-means. Unpaired t-tests and Mann-Whitney tests were used for normally and non-normally distributed data, respectively. Differences in graft detachments were analyzed with Fisher's exact and Chi square test. There was no significant difference in any parameter, except the numbers of triple procedures. BCVA (logMAR) was 0.25 ± 0.18 in the venting group and 0.25 ± 0.19 in the non-venting group (p = 0.92), subjective astigmatism was -1.53 ± 0.99 diopters and -1.33 ± 0.78 diopters (p = 0.15), respectively. CFS astigmatism and higher order aberrations were statistically uniform. The relative risk (RR) of graft detachment was also uniform between the venting versus non-venting group (RR 0.72, p = 0.40), and between triple versus non-triple procedures (RR 0.71, p = 0.43). The preoperative corneal curvature had no impact on the risk of graft detachment (p = 0.74). Venting incisions in DSAEK do not significantly alter BCVA, astigmatism, CFS aberrations or reduce the risk of graft detachment in triple or non-triple procedures.

The variation in biometric parameters of cataract patients with over-long axial length before and after operation

Objective To analyze the change of biometric parameters for patients with over-long axial length after cataract surgery. Methods Twenty eyes of 15 patients, from September 2013 to Feburary 2014 in Xuanwu Hospital were recruited for this study. Phacoemulsification and IOL implantation were performed in those cataract patients. The ocular biometric parameters were recorded by optical coherence biometry (IOL Master) and ultrasound biomicroscopy (UBM) before surgery and three months after surgery. Statistical software package SPSS 17.0 was used to analyze statistically. Results Compared with the preoperative biometric parameters, the axial length shortened and the anterior chamber deepened after surgery, and the difference was statistically significant. The corneal curvature had no significant difference three months after the surgery. There was negative relationship between age and preoperative axial length. No correlation was found between age and preoperative corneal curvature or preoperative anterior chamber depth. Preoperative axial length, preoperative corneal curvature, and preoperative anterior chamber depth had no correlation between each other. There was no correlation between postoperative anterior chamber depth and preoperative axial length, or preoperative corneal curvature, or preoperative anterior chamber depth. Conclusion For cataracts with over-long axial length, the axial length shortened and the anterior chamber depth deepened after cataract surgery. The prediction of postoperative anterior chamber depth still needs to study further. Key words: Cataract; Lens, intraocular; Axial, over-long; Biometry

Two percent ethylenediaminetetraacetic acid chelation treatment for band-shaped keratopathy, without blunt scratching after removal of the corneal epithelium.

BackgroundThe purpose of this study was to assess the effectiveness of 2% ethylenediaminetetraacetic acid (EDTA) for the treatment of band-shaped keratopathy.MethodsWe studied 24 eyes of 16 patients with band-shaped keratopathy who underwent EDTA chelation treatment from April 1, 2011 to December 31, 2012. We compared preoperative and 1 month postoperative logarithm of the minimum angle of resolution (logMAR) best corrected visual acuity, intraocular pressure, and corneal curvature radius (K1, horizontal meridian; K2, vertical meridian; Km, average of K1 and K2). The Mann-Whitney U-test was used to determine the significance of differences.ResultsThere was a significant difference in preoperative and postoperative logMAR best corrected visual acuity (P=0.01). There were no significant differences in preoperative and postoperative intraocular pressure (P=0.24) or corneal curvature radius (K1, P=0.54; K2, P=0.49; Km, P=0.45).ConclusionAfter 2% EDTA chelation treatment, post-operative logMAR best corrected visual acuity improved significantly. Moreover, since there was no significant difference in corneal curvature radius, there was little influence on corneal surface form. We believe that the results of our 2% EDTA chelation treatment were comparable with results obtained with 3.75% EDTA chelation treatment in previous reports. Two percent EDTA chelation is an effective treatment for band-shaped keratopathy and a useful method for any institution.

One-Year Experience in Presbyopia Correction With Biaspheric Multifocal Central Presbyopia Laser In Situ Keratomileusis

To analyze simultaneous vision (distance and near) 1-year after biaspheric multifocal central presbyLASIK treatments for hyperopia and myopia with or without astigmatism. Patients were treated to correct distance ametropias and alleviating presbyopic symptoms simultaneously. All patients have been treated in Presby aberration-free mode using FemtoLASIK for Sphere from -7.00 to +3.25 diopters (D), astigmatism up to 3.00 D, and addition up to +2.75 D. No eye had previous corneal refractive surgery. Preoperative corneal curvature ranged between 40 and 48 D, with pachymetry thicker than 500 μm. Preoperative corrected distance visual acuity was 0.1 logarithm of the minimum angle of resolution (logMAR) or better, with near vision of 0.2 logRAD or better with addition up to +2.50 D. Sixty-six eyes treated bilaterally using PresbyMAX software were reviewed. For 31 patients (94%), 1-year follow-up was completed. At 1 year, 70% of patients achieved uncorrected distance visual acuity 0.1 logMAR or better, 84% patients obtained uncorrected near visual acuity 0.1 logRAD or better, and 83% of eyes were within 0.75 D of defocus. Postoperative mean spherical equivalent refraction was -0.47 ± 0.44 D. Stability was achieved from the 6-week follow-up. Eighty-five percent of patients achieved simultaneously uncorrected distance visual acuity 0.2 logMAR or better and uncorrected near visual acuity 0.2 logRAD or better. Patient selection and expectation management is essential to achieve patient satisfaction. Even though optically the results are predictable and good, some patients find it difficult to adapt to the compromise and others are dissatisfied by the minor loss of distance visual acuity. Certain individuals are best suited for PresbyMAX. A test with multifocal contact lenses or trial frames that creates slightly defocused images can be used to simulate postoperative visual impressions and verify patient acceptance.

3-Month experience in presbyopic correction with bi-aspheric multifocal central presbyLASIK treatments for hyperopia and myopia with or without astigmatism

PurposeTo analyze simultaneous vision (distance and near) 3-month after bi-aspheric multifocal central presbyLASIK treatments for hyperopia and myopia with or without astigmatism. MethodsRetrospective study analyzing patients that had been treated for correcting distance ametropiae and alleviating presbyopic symptoms simultaneously. All patients had been treated in Presby Aspheric mode using FemtoLASIK. No eye had previous corneal refractive surgery. Preoperative corneal curvature ranged between 40D and 48D, with pachymetry thicker than 500μm. Preoperative best distance corrected visual acuity (CDVA) was 0.1 LogMAR or better, with best corrected near vision (CNVA) of 0.2 LogRAD or better. Results66 patients treated using PresbyMAX software (SCHWIND eye-tech-solutions GmbH and Co. KG, Kleinostheim, Germany) were reviewed. For 24 patients, 3-month follow-up was completed. At 3 months, 71% of patients achieved UDVA 0.1 LogMAR or better, 79% patients obtained UNVA 0.1 LogRAD or better, and 83% of eyes were within 0.75 diopters (D) of defocus. Postoperative mean spherical equivalent refraction was −0.15±0.50D. Stability was achieved from the 6-week follow-up. 92% of patients achieved UDVA 0.2 LogMAR or better and UNVA 0.2 LogRAD or better. No statistical differences between myopes/hyperopes or between males/females were found. ConclusionsPatient selection and expectation management are essential to achieve patient satisfaction. Even though optically the results are quite predictable, some patients find it difficult to adapt to the compromise between far and near vision, and others are dissatisfied by the minor loss of distance VA.

Langzeitverlauf nach perforierender Keratoplastik bei Keratokonus – Auswirkungen von präoperativem Visus und Astigmatismus auf die funktionellen Ergebnisse

The purpose of this study was to assess the long-term functional visual results of penetrating keratoplasty for keratoconus and to assess the impact of the patient's preoperative corneal curvature and preoperative best spectacle corrected visual acuity (BCVA) on the refractive outcome. In this retrospective study 456 patients with keratoconus who received central round penetrating keratoplasty (PK) were examined 1/3/5/8/ > 9 years postoperatively. Patients were divided retrospectively into subgroups: first based on their preoperative keratometric (K-) readings: group I.1, < 50 diopters (D) (n = 21); group I.2, 50 - 60 D (n = 102); group I.3, > or = 60 D (n = 164); group I.4, irregular corneal shape with non-measurable K-reading (n = 158), group I.0 unknown preoperative K-reading (n = 58) and then based on the preoperative BCVA: group II.0 BCVA < or = 0.1 (n = 204); group II.1 BCVA > 0.1 (n = 263). The trephination was performed using the 193-nm excimer laser and the transplanted cornea was fixed by a double running cross-stitch suture. The outcome measures included keratometric central refractive equivalent (KEQ), keratometric astigmatism (AST), spherical equivalent (SEQ), refractive cylinder (CYL), best corrected visual acuity (BCVA), surface regularity index (SRI), surface asymmetry index (SAI)topographic central power equivalent (T-EQ) and topographic astigmatism (T-AST). Five/eight years postoperatively, BCVA was 0.71/0.73; KEQ was 43.4/44.4 D; SEQ -1.6/-0.8; AST was 3.4/3.6 D; CYL was 3.0/3.0 D, SRI was 0.88/0.83; SAI was 0.78 / 0.78; T-EQ was 44.5/44.9 D and T-AST was 4.0/4.2 D. The results for BCVA of patients whose preoperative BCVA measured < or = 0.1 were significantly worse than the results of patients with better preoperative BCVA. Other comparisons among the subgroups revealed no further significant differences for any parameter tested. In our study the long-term results of BCVA after penetrating keratoplasty for keratoconus seem to be quite stable (0.7). This indicates that corneal transplantation is a viable option in the clinical course of keratoconus. Furthermore, the outcome of PK for keratoconus seems to be independent of the patient's preoperative corneal curvature. In contrast, unfavourable BCVA preoperatively may be a negative predictor for the visual outcome.

Introducing a New Ratio Useful in the Estimation of Preoperative Corneal Power in Patients With Myopic LASIK Based on Postoperative Corneal Data

The aim of this study was to establish a new constant ratio for the calculation of preoperative total corneal power using postoperative corneal data alone in patients after laser in situ keratomileusis (LASIK). Preoperative anterior and posterior corneal radii from 192 pre-LASIK eyes were analyzed to derive a constant ratio in the first part of the study. In the second part of the study, with a set of post-LASIK patients (98 eyes), this ratio was used to estimate preoperative total corneal power. This estimated total corneal power was compared with the true value obtained from direct preoperative measurement. The ratio (R(roc)) between the preoperative anterior central 10-mm corneal curvature and the posterior peripheral 7- to 10-mm corneal curvature was 1.166 +/- 0.049. Estimated mean preoperative total corneal power was 43.42 +/- 2.21 D, whereas the true preoperative mean keratometric value (SimK) was 43.40 +/- 2.64 D. The mean difference was 0.02 +/- 2.65 D (P = 0.942). The pre-LASIK corneal power can be estimated using post-LASIK data together with R(roc). This will be useful in post-LASIK patients requiring cataract surgery but without the availability of pre-LASIK corneal data for the estimation of the preoperative keratometric power when the double-K technique was used to calculate the intraocular lens power.

Influence of preoperative keratometry on refractive results after laser-assisted subepithelial keratectomy to correct myopia

To study the relationship between preoperative keratometry and residual spherical equivalent (SE) after myopic laser-assisted subepithelial keratectomy (LASEK). Vissum Madrid, Madrid, Spain. This retrospective study comprised 1149 consecutive eyes that had LASEK to correct myopia. The relationship between preoperative keratometry and the 3-month postoperative SE was analyzed by linear regression. The same analysis was performed in the first decile (percentile 10) with the flattest keratometry readings, in the decile with the steepest readings, and in the quartiles with the lowest and highest preoperative myopia. Preoperatively, the mean SE was -4.59 diopters (D) +/- 2.80 (SD) (range -0.25 to -13.00 D) and the mean keratometry, 44.20 +/- 1.60 D (range 39.00 to 49.00 D). Three months postoperatively, the mean SE was +0.05 +/- 0.50 D. There was a significant (P = .04), although weak (r2 = 0.003), correlation between the mean preoperative keratometry and residual SE. Linear regression showed a positive significant correlation within each decile. The correlation was weak in the decile with the flattest corneas (115 eyes) (r2 = 0.04, P = .04) and slightly stronger in the decile with the steepest corneas (115 eyes) (r2 = 0.1, P = .001) (ie, the steeper the cornea, the greater the overcorrection). There was a weak correlation in the group with higher preoperative myopia (r2 = 0.05, P = .0003) but no correlation in the lower myopia group (P = .3). Preoperative corneal curvature did not seem to influence the spherical refractive outcomes after myopic LASEK.