Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography

Posted Posted in cornea, lasik

 flying spot, laser, transepithelial, phototherapeutic keratectomy, optical coherence tomography

J Cataract Refract Surg. 2017 Apr;43(4):525-536. doi: 10.1016/j.jcrs.2017.03.004.

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography.

Abstract

PURPOSE:

To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings.

SETTING:

Casey Eye Institute, Portland, Oregon, USA.

DESIGN:

Prospective nonrandomized case series.

METHODS:

Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models.

RESULTS:

Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity and corrected distance visual acuity were significantly improved (P < .01) by 3.7 Snellen lines and 2.0 Snellen lines, respectively, to a mean of 20/41.2 and 20/22.0, respectively. Achieved laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer’s nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases.

CONCLUSIONS:

The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation.

Modern laser in situ keratomileusis outcomes.

Posted Posted in lasik
Modern, lasik, keratomileusis, outcomes
J Cataract Refract Surg. 2016 Aug;42(8):1224-34. doi: 10.1016/j.jcrs.2016.07.012.

Modern laser in situ keratomileusis outcomes.

Abstract

Laser in situ keratomileusis (LASIK) articles published between 2008 and 2015 that contain clinical outcomes data were reviewed and graded for quality, impression, and potential bias. All 97 relevant articles (representing 67 893 eyes) provided a positive or neutral impression of LASIK. Industry bias was not evident. The aggregate loss of 2 or more lines of corrected distance visual acuity was 0.61% (359/58 653). The overall percentage of eyes with uncorrected distance visual acuity better than 20/40 was 99.5% (59 503/59 825). The spherical equivalent refraction was within ±1.0 diopter (D) of the target refraction in 98.6% (59 476/60 329) of eyes, with 90.9% (59 954/65 974) within ±0.5 D. In studies reporting patient satisfaction, 1.2% (129/9726) of patients were dissatisfied with LASIK. Aggregate outcomes appear better than those reported in summaries of the safety and effectiveness of earlier laser refractive surgery systems approved by the U.S. Food and Drug Administration. Modern results support the safety, efficacy, and patient satisfaction of the procedure.

J Cataract Refract Surg. 2016 Aug;42(8):1224-34. doi: 10.1016/j.jcrs.2016.07.012.

Modern laser in situ keratomileusis outcomes.

Abstract

Laser in situ keratomileusis (LASIK) articles published between 2008 and 2015 that contain clinical outcomes data were reviewed and graded for quality, impression, and potential bias. All 97 relevant articles (representing 67 893 eyes) provided a positive or neutral impression of LASIK. Industry bias was not evident. The aggregate loss of 2 or more lines of corrected distance visual acuity was 0.61% (359/58 653). The overall percentage of eyes with uncorrected distance visual acuity better than 20/40 was 99.5% (59 503/59 825). The spherical equivalent refraction was within ±1.0 diopter (D) of the target refraction in 98.6% (59 476/60 329) of eyes, with 90.9% (59 954/65 974) within ±0.5 D. In studies reporting patient satisfaction, 1.2% (129/9726) of patients were dissatisfied with LASIK. Aggregate outcomes appear better than those reported in summaries of the safety and effectiveness of earlier laser refractive surgery systems approved by the U.S. Food and Drug Administration. Modern results support the safety, efficacy, and patient satisfaction of the procedure.

Effect of Anisometropia on the Predictability and Accuracy of Refractive Surgery

Posted Posted in lasik
Anisometropia,Predictability,Accuracy,lasik, Refractive Surgery
Cornea. 2016 Jul 27. [Epub ahead of print]

Effect of Anisometropia on the Predictability and Accuracy of Refractive Surgery.

Abstract

PURPOSE:

To evaluate the predictability and accuracy of refractive surgery among adults with myopic anisometropia.

METHODS:

Consecutive cases of myopic eyes that underwent bilateral laser-assisted in situ keratomileusis (LASIK) or bilateral photorefractive keratectomy (PRK) during a 12-year period in a single center were included. Myopic anisometropia was defined as a difference greater than 1.5 D in spherical equivalent between eyes preoperative.

RESULTS:

A total of 10,046 paired, operated nonamblyopic eyes of 5023 patients were analyzed. Of these, 472 eyes of 236 (4.7%) patients had myopic anisometropia without amblyopia, and 9574 eyes of 4787 patients served as isometropic controls. After refractive surgery, in the anisometropic group the more myopic eye was corrected by +0.47 ± 0.78 (D) more than the contralateral eye (P < 0.0001). Relative to the target refraction, the more myopic eye was overcorrected by 0.21 ± 0.79 D compared with an undercorrection of 0.16 ± 0.60 D in the less myopic contralateral eye (P < 0.0001) and compared with an undercorrection of 0.15 ± 0.62 D in the isometropic controls (P < 0.0001). Additionally, the variability in the correction of the more myopic eyes was significantly higher compared with the less myopic contralateral eyes and isometropic controls (P < 0.0001). These trends were evident both in PRK and LASIK treatments. The effect of anisometropia was found to be independent of the magnitude of preoperative myopia or surgeon identity.

CONCLUSIONS:

The more myopic eye of anisometropes undergoing refractive surgery has lower predictability and accuracy and tends to be overcorrected, whereas the less myopic eye has outcome similar to isometropic controls. These results suggest that refractive surgery nomograms should take into account anisometropia.

Globe Rupture of a Post-LASIK Keratectasia Eye From Blunt Trauma

Posted Posted in lasik
Cornea. 2016 Jul 27. [Epub ahead of print]

Globe Rupture of a Post-LASIK Keratectasia Eye From Blunt Trauma.

Abstract

PURPOSE:

To report a case of globe rupture in a patient with post-laser in situ keratomileusis (LASIK) ectasia after blunt trauma.

METHODS:

Observational case report.

RESULTS:

A 42-year-old man with a history of post-LASIK ectasia sustained paracentral corneal rupture secondary to blunt trauma from a fist to his left eye (OS). Slit-lamp examination revealed rupture in the posterior stroma (inferior paracentral) of the OS with an overlying intact LASIKflap; however, the inferior edges of the LASIK flap were Seidel positive. The anterior chamber was flat. Although he was initially managed with cyanoacrylate glue and abandage contact lens, the patient eventually required tectonic penetrating keratoplasty. The postoperative course was unremarkable, and over 1 year later, the visual acuity OS was 20/25 with -7.50 + 2.00 × 0.50.

CONCLUSIONS:

Globe rupture from blunt trauma has not been shown to be more common in patients with a history of LASIK. Although blunt trauma to the post-LASIK globe would generally incur a similar risk of rupture to that of the normal eye, keratectasia after LASIK may predispose the globe to rupture.

Abstract

PURPOSE:

To report a case of globe rupture in a patient with post-laser in situ keratomileusis (LASIK) ectasia after blunt trauma.

METHODS:

Observational case report.

RESULTS:

A 42-year-old man with a history of post-LASIK ectasia sustained paracentral corneal rupture secondary to blunt trauma from a fist to his left eye (OS). Slit-lamp examination revealed rupture in the posterior stroma (inferior paracentral) of the OS with an overlying intact LASIKflap; however, the inferior edges of the LASIK flap were Seidel positive. The anterior chamber was flat. Although he was initially managed with cyanoacrylate glue and abandage contact lens, the patient eventually required tectonic penetrating keratoplasty. The postoperative course was unremarkable, and over 1 year later, the visual acuity OS was 20/25 with -7.50 + 2.00 × 0.50.

CONCLUSIONS:

Globe rupture from blunt trauma has not been shown to be more common in patients with a history of LASIK. Although blunt trauma to the post-LASIK globe would generally incur a similar risk of rupture to that of the normal eye, keratectasia after LASIK may predispose the globe to rupture.

Femtosecond laser-assisted in situ keratomileusis multifocal ablation profile using a mini-monovision approach for presbyopic patients with hyperopia.

Posted Posted in lasik

Femto LASIK; hyperopia; presbyLasik; presbyopia; visual acuity

Clin Ophthalmol. 2016 Jul 14;10:1245-56. doi: 10.2147/OPTH.S102008. eCollection 2016.
Femtosecond laser-assisted in situ keratomileusis multifocal ablation profile using a mini-monovision approach for presbyopic patients with hyperopia.
Vastardis I1, Pajic-Eggspühler B1, Müller J2, Cvejic Z3, Pajic B4.
Author information
Abstract
PURPOSE:
To report the visual outcomes of the femtosecond laser-assisted multifocal aspheric corneal ablation profile using a mini-monovision approach and to evaluate if corneal multifocality was effective, and to report the relative benefits of this approach.
PATIENTS AND METHODS:
Bilateral femtosecond laser-assisted in situ keratomileusis using a multifocal aspheric corneal ablation profile was performed on 19 hyperopic patients (38 eyes). They were divided into two groups based on eye dominance: dominant eye (DE) group targeting emmetropia and the nondominant eye (NDE) group targeting -0.5 D slight myopia. The uncorrected distance visual acuity (UDVA), uncorrected intermediate visual acuity (UIVA), uncorrected near visual acuity (UNVA), and retreatment rates were reported from baseline to 6 months.
RESULTS:
The UNVA, UIVA, and UDVA improved significantly in both groups (Kruskal-Wallis test, DE and NDE: P<0.00001, P<0.000005, and P=0.00001, respectively). Corrected distance visual acuity (CDVA) baseline was better in both groups in comparison to UDVA at 6 months (Wilcoxon test, DE: P<0.001, 95% confidence interval (CI) of the median 0.0-0.0 LogMAR and 0.1000-0.1218 LogMAR and NDE: P=0.010, 95% CI of the median 0.0-0.0 LogMAR and 0.00-0.10 LogMAR). There was a significant loss of lines between CDVA baseline and UDVA at 6 months in both groups (DE group: 68% of eyes lost one line or more; NDE group: 58% of eyes lost one line or more). The corrected near visual acuity baseline compared to UNVA at 6 months was not statistically important (Wilcoxon test, DE: P=0.8125, 95% CI of the median 0.0-0.0 LogMAR and 0.0-0.0 LogMAR and NDE: P=0.82, 95% CI of the median 0.0-0.0 LogMAR and 0.0-0.0 LogMAR). The comparison among the UDVA, UIVA, and UNVA between the two groups at baseline and during all follow-ups was not statistically important. Two cases from the DE group were retreated (6%).
CONCLUSION:
Use of this multifocal aspheric corneal ablation profile in patients with hyperopic presbyopia significantly improved UDVA, UIVA, and UNVA. This improvement was due to created multifocality of the cornea. The mini-monovision seems not to affect UDVA, UIVA, and UNVA between the two groups. The retreatment rates at the 6-month evaluation were significantly less in our study when compared with other studies. This method seems to improve UDVA, UIVA, and UNVA but could result in a significant statistical difference between CDVA baseline and UDVA at 6 months that leads to loss of lines in distance vision. Despite promising results, this is a preliminary evaluation of this new profile, and a larger number of eyes are needed to verify visual outcomes, retreatment rates, and safety.
KEYWORDS:
Femto LASIK; hyperopia; presbyLasik; presbyopia; visual acuity

The assessment of the stability of the corneal structure after LASIK correction of myopia by different optical zone diameters

Posted Posted in lasik
stability,LASIK,myopia,optical zone diameters
Vojnosanit Pregl. 2016 Jun;73(6):572-6.

The assessment of the stability of the corneal structure after LASIK correction of myopia by different optical zone diameters.

Abstract

BACKGROUND/AIM:

Enlargement of optical zone (OZ) diameter during laser in situ keratomileusis (LASIK) correction of myopia postoperatively improves the optical outcome, however, it also leads to the increased stroma tissue consumption–progressive corneal thinning. The aim of this investigation was to present the possibility of safe OZ enlargement without impairing the structural stability of the cornea, while obtaining an improved optical outcome with LASIK treatment of short-sightedness.

METHODS:

Preoperative assessment of the cornea structure and prediction of the ablated stroma tissue consumption was conducted in 37 patients (74 eyes) treated for short-sightedness by means of the LASIK method. With the eyes that, according to their cornea structure, had the capacity for OZ diameter enlargement of 0.5 mm, LASIK treatment was performed within the wider OZ diameter of 7.0 mm compared to the standard 6.5 mm. The following two groups were formed, depending on the diameter of the utilized OZ: the group I (the eyes treated with the OZ 6.5 mm, n = 37) and the group II (the eyes treated with the OZ 7.0 mm, n = 37).

RESULTS:

No significant difference in the observed structural parameters of the cornea was detected between the groups of patients treated with different OZ diameters. The values of all the parameters were significantly bellow the threshold values for the development of postoperative ectasia.

CONCLUSION:

Diameter enlargement of the treated OZ, if there is a preoperative cornea capacity for such enlargement, will not impair the postoperative stability of the cornea structure, and will significantly improve the optical outcome.

PMID:
27498450

Comparison of corneal flaps created by Wavelight FS200 and Intralase FS60 femtosecond lasers.

Posted Posted in lasik
Fourier,optical coherence tomography,Intralase FS60, Wavelight FS200, femtosecond laser,flap, Lasik
Int J Ophthalmol. 2016 Jul 18;9(7):1006-10. doi: 10.18240/ijo.2016.07.12. eCollection 2016.

Comparison of corneal flaps created by Wavelight FS200 and Intralase FS60 femtosecond lasers.

Abstract

AIM:

To assess and compare the morphology of corneal flaps created by the Wavelight FS200 and Intralase FS60 femtosecond lasers in laser in situ keratomileusis (LASIK).

METHODS:

Four hundred eyes of 200 patients were enrolled in this study and divided into Wavelight FS200 groups (200 eyes) and Intralase FS60 groups (200 eyes). Fourier-domain optical coherence tomography (RTVue OCT) was used to measure the corneal flap thickness of 36 specified measurements on each flap one week after surgery. Results were used to analyze the regularity, uniformity and accuracy of the two types ofLASIK flaps.

RESULTS:

The mean thickness of corneal flap and central flap was 105.71±4.72 µm and 105.39±4.50 µm in Wavelight FS200 group and 109.78±11.42 µm and 109.15 ±11.59 µm in Intralase FS60 group, respectively. The flaps made with the Wavelight FS200 femtosecond laser were thinner than those created by the Intralase FS60 femtosecond laser (P=0.000). Corneal flaps in the 2 groups were uniform and regular, showing an almost planar configuration. But the Wavelight FS200 group has more predictability and uniformity of flap creation. The mean deviation between achieved and attempted flap thickness was smaller in the Wavelight FS200 group than that in the Intralase FS60 group, which were 5.18±3.71 µm and 8.68±7.42 µm respectively. The deviation of more than 20 µm was 0.2% measurements in Wavelight FS200 group and 8.29% measurements in Intralase FS60 group.

CONCLUSION:

The morphologies of flaps created by Wavelight FS200 are more uniform and thinner than those created by Intralase FS60.

KEYWORDS:

Fourier-domain optical coherence tomography; Intralase FS60; Wavelight FS200; femtosecond laser; flap; laser in situ keratomileusis

Combining Placido and Corneal Wavefront Data for the Detection of Forme Fruste Keratoconus

Posted Posted in lasik
Placido Ring,Wavefront Analysis, Detection ,Forme Fruste Keratoconus
J Refract Surg. 2016 Aug 1;32(8):510-6. doi: 10.3928/1081597X-20160523-01.

Combining Placido and Corneal Wavefront Data for the Detection of Forme Fruste Keratoconus.

Abstract

PURPOSE:

To evaluate the accuracy of a new objective method based on Placido disk-derived data for the detection of eyes at risk of ectasia.

METHODS:

One hundred nineteen eyes of 176 patients were included and separated into two groups, normal and forme fruste keratoconus (FFKC), using automated corneal classification software. Normal eyes (n = 114) were classified as negative for keratoconus and keratoconus suspect and had undergone LASIK with unremarkable follow-up for 4 years. The FFKC group was composed of 62 topographically normal eyes of patients with keratoconus in the fellow eye. Anterior topographic parameters, obtained from specular topography using Placido-based indices and corneal wavefront Zernike coefficients, were compared between groups. Receiver operating characteristic (ROC) curves were used to identify cut-off points in discriminating between keratoconic and normal eyes. Validation was performed on an external group of eyes.

RESULTS:

A discriminant function was built combining four corneal wavefront variables and four Placido variables. The area under the receiver operating characteristic was 0.970 with this eight-variable model. The validation of this function had 63% sensitivity for detecting FFKC and 100% sensitivity for detecting keratoconus, with a specificity of 82%.

CONCLUSIONS:

Indices generated from corneal wavefront and Placido measurements can assist in identifying early or mild forms of keratoconus undetected by a Placido-based neural network program. [J Refract Surg. 2016;32(8):510-516.].

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration

Posted Posted in lasik
microkeratome, incision,laser ablation, wave aberration
Am J Ophthalmol. 2003 Aug;136(2):327-37.

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration.

Abstract

PURPOSE:

To study the optical changes induced by the microkeratome cut, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ keratomileusis (LASIK) eyes.

DESIGN:

Prospective randomized clinical trial.

METHODS:

A Hansatome microkeratome was used to cut a corneal flap in one eye (study eye) of 17 normal myopic patients and a subsequentlaser ablation was performed 2 months after this initial microkeratome incision. Control eyes received conventional LASIK treatments at the latter time point. The wave aberration of both the study and contralateral control eyes were measured over a 6-mm pupil with a Shack-Hartmann wavefront sensor for all preoperative, postflap cut, and postablation visits.

RESULTS:

The eye’s higher order aberrations had a small, but significant increase (P =.03) of approximately 30% 2 months after cutting a flap. No systematic changes were observed in nearly all Zernike coefficients from their preoperative levels at 2 months postflap cut. A significant difference between the study and control eyes was observed for one trefoil mode, Z(3)(3) (P =.04).

CONCLUSIONS:

There was a wide variation in the response of individual Zernike modes across patients after cutting a flap. The majority of spherical aberration induced by the LASIK procedure seems to be due to the laser ablation and not the microkeratome cut. In addition, the total and higher order root mean square of wavefront errors were nearly identical for both the study and control eyes 3-months after the laser ablation, indicating that a procedure in which the incision and the ablation are separated in time to better control aberrations does not compromise the outcome of a conventional LASIK treatment.

Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE).

Posted Posted in lasik
Wound healing,hyperopic,small incision lenticule extraction,SMILE
Sci Rep. 2016 Jul 15;6:29802. doi: 10.1038/srep29802.

Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE).

Abstract

Refractive surgical treatment of hyperopia still remains a challenge for refractive surgeons. A new nomogram of small incision lenticule extraction (SMILE) procedure has recently been developed for the treatment of hyperopia. In the present study, we aimed to evaluate the wound healing and inflammatory responses of this new nomogram (hyperopic-SMILE), and compared them to those of hyperopic-laser-assisted in situ keratomileusis(LASIK), using a rabbit model. A total of 26 rabbits were used, and slit lamp biomicroscopy, autorefractor/keratometer, intraocular pressure measurement, anterior segment optical coherence tomography, corneal topography, and in vivo confocal microscopy examinations were performed during the study period of 4 weeks. The corneas were then harvested and subject to immunofluorescence of markers for inflammation (CD11b), wound healing (fibronectin) and keratocyte response (HSP47). The lenticule ultrastructual changes were also analyzed by transmission electron microscopy. Out results showed that hyperopic-SMILE effectively steepened the cornea. Compared to hyperopic-LASIK, hyperopic-SMILE had less postoperative wound healing response and stromal interface reaction, especially in higher refractive correction. However, compared to myopic-SMILE, hyperopic-SMILE resulted in more central deranged collagen fibrils. These results provide more perspective into this new treatment option for hyperopia, and evidence for future laser nomogram modification