Visual outcomes and patient satisfaction after presbyopic lens exchange with a diffractive multifocal intraocular lens.

PURPOSE: To investigate the visual outcomes, severity of symptoms, and patient satisfaction after refractive lens exchange (RLE) with a diffractive multifocal intraocular lens (IOL). METHODS: A nonrandomized, unmasked, retrospective chart review study was performed. Patients who underwent RLE with ZMA00 (Abbott Laboratories) were identified from a hospital database. Eyes with preoperative uncorrected distance visual acuity or corrected distance visual acuity 20/20 or better were included. The study cohort comprised 45 eyes from 29 patients. Monocular uncorrected and distance-corrected visual acuity at distance, 67 cm, and 30 cm were measured 6 months postoperatively. A patient questionnaire assessing visual symptoms (halo, night glare, and starburst) and satisfaction with visual performance was administered. RESULTS: Six months postoperatively, mean uncorrected visual acuity (logMAR) was -0.10±0.13, 0.43±0.25 at 67 m (intermediate), and 0.18±0.05 at 30 m (near). Mean distance-corrected visual acuity at these distances was -0.02±0.06, 0.40±0.21, and 0.17±0.02, respectively. Twenty-seven patients completed the questionnaire. Patients reported postoperative halos (78%), night glare (26%), and starbursts (48%). All bilateral RLE patients were spectacle-free at all distances, whereas 50% of unilateral RLE patients required spectacles postoperatively. Bilateral RLE patients with habitual spectacle use preoperatively were the most satisfied with their postoperative visual performance. CONCLUSIONS: Refractive lens exchange with the ZMA00 is an option for presbyopic correction; however, significant glare, halo, and starburst issues are subjectively reported.

Correlation Between Axial Length and Anterior Chamber Depth in Normal Eyes, Long Eyes, and Extremely Long Eyes.

PURPOSE: The objective of this study was to investigate the correlation between axial length (AL) and anterior chamber depth (ACD) in normal to long eyes and in extremely long eyes. DESIGN: This was an observational cross-sectional study in a single-center, private hospital. METHODS: Axial length and ACD data were retrieved from the intraocular lens (IOL) Master database of patients who presented for IOL or phakic lens implantation. Only left eyes were included. The correlation between AL and ACD was tested with Pearson correlation coefficient in all eyes, normal to long eyes (AL < 27.5 mm), and extremely long eyes (AL ≥ 27.5 mm). P < 0.01 was statistically significant. RESULTS: The cohort was composed of 1184 eyes of 1184 Chinese patients. The mean age was 65.8 ± 13.3 years (range, 19-98 years). The mean AL and ACD were 24.73 ± 2.48 mm (range, 20.51-36.20 mm) and 3.09 ± 0.44 mm (range, 1.95-4.68 mm), respectively. Pearson correlation coefficients in all eyes, normal to long eyes (1026 eyes, 87%), and extremely long eyes (158 eyes, 13%) were 0.56 (P < 0.001), 0.59 (P < 0.001), and -0.15 (P = 0.67), respectively. CONCLUSIONS: There was a statistically significant positive correlation between AL and ACD in normal and long eyes but not in extremely long eyes. No correlation between AL and ACD in extremely long eyes requires newer-generation IOL formulas (ACD included) to increase the accuracy of IOL implantation.

Conductive keratoplasty to treat hyperopic overcorrection after LASIK for myopia.

PURPOSE: to investigate the refractive outcomes and stability of conductive keratoplasty (CK) for retreatment of myopic LASIK overcorrection. METHODS: seven eyes (six patients) that were overcorrected after myopic LASIK by +1.00 to +2.75 diopters (D) manifest refraction spherical equivalent (MRSE) were retreated using CK. All eyes had insufficient stromal thickness for LASIK retreatment. LightTouch CK was performed at least 1 year after LASIK. Either 8 or 16 spots were applied at 7- and/or 8-mm zones on the cornea. Uncorrected distance visual acuity, manifest refraction, corrected distance visual acuity (CDVA), and postoperative complications were analyzed. RESULTS: mean MRSE after CK at last follow-up was +0.38 ± 0.52 D (range: -0.38 to +1.13 D). The change in MRSE ranged from -0.63 to -2.38 D. Mean MRSE after CK changed from -0.60 ± 2.07 D (range: -3.38 to +1.50 D) at 1 week to +0.45 ± 0.69 D (range: -0.38 to +1.38 D) at 12 months. Two eyes experienced an initial overcorrection of -2.75 D and -3.38 D, respectively, at 1 week after CK. Cylinder ≤0.75 D was induced in four eyes, whereas one eye had a 0.75-D reduction in cylinder. All eyes had CDVA of logMAR 0.10 or better. Two eyes lost one line of CDVA and no eyes lost more than one line. CONCLUSIONS: lighttouch CK retreatment for over-corrected myopic LASIK can reduce the hyperopia but produces minimal change in cylinder, and may be appropriate for eyes with insufficient stromal tissue for repeated excimer laser surgery. Early regression occurs commonly.

Intraoperative flap re-cut after vertical gas breakthrough during femtosecond laser keratectomy.

We describe the management of intraoperative vertical gas breakthrough (VGB) during femtosecond laser flap creation in 3 patients. All eyes were immediately re-cut using 2 different microkeratomes, and the laser in situ keratomileusis treatments were completed on the same day. There were no postoperative complications. Corneal abrasion might predispose to VGB. Management of VGB is effective using microkeratomes. Caution is advised during placement of the suction ring and in eyes with preexisting corneal abrasion or loose epithelium if femtosecond laser keratectomy is used. The approach in terms of direction of the microkeratome re-cut is fundamental to the safety and successful re-cut with a microkeratome.

Toric Implantable Collamer Lens for high myopic astigmatic Asian eyes.

PURPOSE: To evaluate early visual outcomes, refractive outcomes, and complications of the Toric Implantable Collamer Lens (TICL) for the correction of high myopic astigmatism in Asian eyes. DESIGN: Prospective, nonrandomized clinical study. PARTICIPANTS: Forty-four eyes of 29 patients with myopia (spherical equivalent) between 6 and 18.25 diopters (D), and 1 and 4.5 D of astigmatism. METHODS: Implantation of TICL. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), manifest refraction, best spectacle-corrected visual acuity (BSCVA), and postoperative complications. RESULTS: At 6 months postoperatively, 70.59% of eyes had 20/20 or better UCVA and 68.57% had postoperative UCVA better than or equal to preoperative BSCVA. At baseline, no eyes had refractive cylinder <1 D; however, postoperatively 77.14% of eyes had <1.00 D of refractive cylinder. The mean refractive cylinder changed from 2.64 D (+/-0.91) preoperatively to 0.59 D (+/-0.51) postoperatively. Sixty percent of eyes were within 0.50 D and 85.71% of eyes were within 1.00 D of the targeted cylinder correction. Baseline manifest refraction spherical equivalent (MRSE) changed from -13.18 D (+/-2.41) to 0.00 D (+/-0.42) postoperatively. The number of eyes within 0.50 D and 1.00 D of the predicted MRSE were 82.86% and 97.14%, respectively. A BSCVA of 20/15 occurred in 45.71% of eyes postoperatively compared with 22.86% of eyes preoperatively. A BSCVA of 20/20 or better occurred in 94.29% postoperatively compared with 77.14% preoperatively. Postoperatively, 1 eye (2.86%) lost 1 line of BSCVA and none lost >1 line of BSCVA. Thirty-one percent of eyes gained 1 line of BSCVA and 8.57% gained 2 lines of BSCVA postoperatively. Misalignment of TICL axis occurred in 2 eyes of 2 patients. CONCLUSIONS: The visual outcomes, refractive outcomes, and predictability are comparable with the United States Food and Drug Administration data on TICLs in non-Asian eyes. Safety concerns were not identified.

Evaluation of the apparent change in posterior corneal power in eyes with LASIK using Orbscan II with magnification compensation.

PURPOSE: To develop a mathematical model for the assessment of the apparent posterior corneal curvature changes after myopic keratorefractive surgery with Orbscan (Bausch & Lomb) and to assess its accuracy with clinical data. METHODS: Part 1: Postoperative and preoperative magnification ratio of the posterior corneal surface was calculated from a theoretical eye model. Changes of radius and power of the posterior corneal surface were estimated over a wide range of refractive corrections and preoperative anterior corneal power. Part 2: The measured radius of the posterior cornea by Orbscan II 3 months postoperatively was converted to a new value based on the mathematical model. Both the measured radius and corrected radius were compared with preoperative values using paired sample t test. RESULTS: Myopic correction is associated with apparent steepening of the posterior curvature. The higher the amount of correction, the more the apparent difference. A statistically significant difference was noted between preoperative and measured postoperative radius of the posterior cornea (0.35 +/- 0.16 mm, P<.01). However, no significant difference was seen between preoperative and corrected postoperative radius of the posterior cornea (0.008 +/- 0.11 mm, P=.44). CONCLUSIONS: The change of corneal magnification induced by refractive correction partly explains the apparent steepening of the posterior corneal curvature. The mathematical model effectively compensates for the error in Orbscan II in the assessment of posterior corneal curvature after LASIK.

Introducing a new ratio useful in the estimation of preoperative corneal power in patients with myopic LASIK based on postoperative corneal data.

AIM: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Measurement of LASIK flap thickness with anterior segment optical coherence tomography.

PURPOSE: To assess the interobserver variability and agreement of anterior segment optical coherence tomography (OCT) in the measurement of LASIK flap thickness, and to compare the results with intraoperative ultrasound pachymetry measurements. METHODS: Thirty-nine eyes of 20 consecutive patients undergoing LASIK with the XP microkeratome (Bausch & Lomb) and ALLEGRETTO Eye-Q laser system (WaveLight Inc) had corneal flap thickness measured with SP-100 ultrasound (Tomey Corp) intraoperatively and with OCT (Visante; Carl Zeiss Meditec Inc) postoperatively. Interobserver assessment was performed by comparing the flap thickness measurements obtained from the same scan by 2 masked, independent observers. Agreement of OCT scan was determined by assessment of 2 different scans of the same eye by the same observer. RESULTS: Mean (+/- standard deviation) flap thickness measured by ultrasound, OCT scan 1 (OCT 1-1) and scan 2 (OCT 1-2) assessed by observer 1, and OCT scan 1 (OCT 2-1) and scan 2 (OCT 2-2) assessed by observer 2 were 112.79+/-19.71, 124.69+/-17.02, 127.59+/-17.32, 130.59+/-20.34, and 133.74+/-19.70 microm, respectively. No statistically significant difference among the interobserver measurements was seen. The difference between OCT and ultrasound measurements by observers 1 and 2 was statistically significant (P<.01). Correlation among all measurements was statistically significant. Good agreement among the OCT scans was noted. CONCLUSIONS: Optical coherence tomography showed good correlation among measurements and observers for different OCT measurements in the assessment of corneal flap thickness after LASIK. However, OCT significantly overestimated flap thickness when compared to ultrasound despite a good correlation between these two modalities. Optical coherence tomography measurements should not be substituted for standad ultrasound measurements at the present time.

Posterior corneal curvature measurements with peripheral fitting zones before and after myopic LASIK using Orbscan II.

PURPOSE: To compare pre- and postoperative posterior corneal curvature measurements in peripheral fitting zones using the Orbscan II topographer in patients undergoing myopic LASIK. METHODS: Retrospective analysis of preoperative and 3-month postoperative Orbscan II data of 194 eyes that underwent myopic LASIK at a university eye center. Posterior corneal power was estimated using the peripheral 7- to 10-mm fitting zones. The pre- and postoperative values were analyzed and compared. RESULTS: The mean difference in estimated pre- and postoperative power of the posterior cornea was -0.04 +/- 0.16 diopters (P < .01). CONCLUSIONS: The difference in posterior corneal curvature measurement following myopic LASIK using the peripheral fitting zone with the Orbscan II, as compared to the preoperative values, is clinically insignificant.

Central corneal thickness measurements by ultrasound, Orbscan II, and Visante OCT after LASIK for myopia.

PURPOSE: To compare central corneal thickness measurements obtained with Orbscan II scanning slit topography, Visante optical coherence tomography (OCT), and ultrasound pachymetry in myopic eyes after LASIK. METHODS: This retrospective study included 34 consecutive patients (68 eyes) who underwent LASIK for the correction of myopia. Six months after surgery, central corneal thickness measurements were obtained using ultrasound pachymetry, Orbscan scanning slit topography, and Visante OCT. Data were analyzed using paired sample t test, Bland and Altman plot, and linear regression. RESULTS: Average postoperative central corneal thickness was 436.65+/-43.82 microm for ultrasound pachymetry, 422.84+/-51.04 microm for Orbscan (0.89 acoustic equivalent correction factor), and 422.26+/-42.46 microm for Visante. Compared to the ultrasound measurement, Orbscan and Visante measurements significantly underestimated the corneal thickness by 13.81+/-17.34 microm (P<.01) and 14.38+/-10.13 microm (P<.01), respectively. CONCLUSIONS: Both Orbscan and Visante OCT underestimated central corneal thickness compared to ultrasound pachymetry 6 months after LASIK, although measurements obtained with Visante OCT had better agreement and correlation with ultrasound pachymetry than with Orbscan.

Comparison of techniques for corneal power assessment after myopic LASIK without the use of preoperative data.

PURPOSE: To compare the accuracy of different corneal power assessment techniques that do not require preoperative information with the clinical history method. METHODS: This retrospective study analyzed 50 eyes of 50 patients using 3-month postoperative data. Net corneal powers were obtained with each of the following methods: Maloney, Wang, Sonego-Krone, Srivannaboon, Shammas, Orbscan flat axis, and Gaussian optics formula with Orbscan. Results were compared to the clinical history method using paired sample t test, Bland-Altman plots, and linear regression. RESULTS: Both the Gaussian optics formula and Wang method were not significantly different from the clinical history method. The Sonego-Krone method significantly underestimated the corneal power, whereas the Maloney, Srivannaboon, Shammas, and Orbscan flat axis methods significantly overestimated the corneal power. CONCLUSIONS: The Gaussian optics formula and Wang method yielded comparable results with the clinical history method for assessing corneal power. The Gaussian optics formula produced the smallest standard deviation.

Comparison of corneal flap thickness between primary eyes and fellow eyes using the Zyoptix XP microkeratome.

PURPOSE: To evaluate corneal flap thickness created in myopic laser in situ keratomileusis (LASIK) using the Zyoptix XP 120 microkeratome (Bausch & Lomb). SETTING: University-based eye clinic. METHODS: Corneal thickness was measured preoperatively and intraoperatively after flap creation in 62 consecutive patients (124 eyes) who had LASIK for the correction of myopia. Corneal flap thickness was calculated by subtracting stromal bed thickness from total corneal thickness. In each patient, both corneas (right followed by left) were cut by 1 the same Zyoptix XP 120 microkeratome blade at the same session. RESULTS: The mean actual flap thickness was 115.34 microm +/- 16.34 (SD) in right eyes and 104.55 +/- 14.34 mum in left eyes. The mean actual flap thickness in right eyes was not statistically significantly different from the 120 microm proposed by the manufacturer (P = .142); however, the mean actual flap thickness in left eyes was statistically significantly different from the 120 microm (P<.001). The mean flap thickness in the second eye was also statistically significantly thinner than in the first eye (P<.001). CONCLUSIONS: The corneal flaps were thinner than expected when a Zyoptix XP 120 microkeratome was used in LASIK. Although the first cuts produced thinner flaps, this difference was not statistically significant. However, the second cuts produced significantly thinner flaps.

Central corneal thickness measurements using Orbscan II, Visante, ultrasound, and Pentacam pachymetry after laser in situ keratomileusis for myopia.

PURPOSE: To compare corneal pachymetry assessment using 4 measurement methods in eyes after laser in situ keratomileusis (LASIK) for myopia. SETTING: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong SAR. METHODS: Fifty-two consecutive patients (103 eyes) who had LASIK for the correction of myopia had Orbscan II (Bausch & Lomb), Visante (Carl Zeiss Meditec), Pentacam (Oculus, Inc.), and ultrasound (US) pachymetry (Sonomed, 200P) 6 months after surgery. Data were analyzed using the paired sample t test, Bland-Altman plots, and linear regression. RESULTS: The mean postoperative pachymetry measured by US, Orbscan (0.89 acoustic factor), Pentacam, and Visante pachymetry were 438.2 microm+/-41.18 (SD), 435.17+/-49.63 microm, 430.66+/-40.23 microm, and 426.56+/-41.6 microm, respectively. Compared with the US measurement, Pentacam and Visante measurements significantly underestimated corneal thickness by a mean of 7.54+/-15.06 microm (P<.01) and 11.64+/-12.87 microm (P<.01), respectively. There was no statistically significant difference between US and Orbscan measurements. CONCLUSION: Pentacam and Visante measurements of corneal thickness 6 months after LASIK were significantly less than those obtained using Orbscan and US pachymetry, although all 4 measurement methods showed a high correlation with each other.