[Rebound tonometry with sterilized probes]

BACKGROUND

Intraoperative measurement of intraocular pressure (IOP) opens up possibilities to investigate the influence of IOP on the stability of the eyeball during the performance of surgical maneuvers. Few techniques have been described, none of which are commercially available. This study investigated the use of sterilized probes for rebound tonometry, which could be used intraoperatively.

MATERIAL AND METHODS

Tonometry was performed on 30 eyes using a noncontact tonometer and rebound tonometry with the iCare 100 and iCare 200 (iCare Finland Oy, Vantaa, Finland) in a sitting and in a supine position. When performing rebound tonometry probes from the package were used sequentially with sterilized probes. The comparability of sterilized and nonsterilized probes was investigated using different rebound tonometers and different settings.

RESULTS

Measurements on a sitting subject were comparable with sterilized and nonsterilized probes. Statistically significant comparability was also found in a supine position. Measurements with identically sterilized probes on identically positioned subjects were comparable with iCare 100 und iCare 200 (T2 vs. T4, p = 0.003 und T3 vs. T5 p < 0.001). The comparison of measurements of the original probe with the sterilized probe in a sitting and in a supine position were possible with statistical significance (p < 0.005). Measuring with the iCare 200 in a sitting position showed a slightly lower IOP with the sterilized probe with the difference being statistically significant.

DISCUSSION

Single autoclaving does not alter the probes' ability to measure IOP.

CONCLUSION

The use of probes which have been sterilized according to the regulations for other surgical instruments opens up new possibilities for the intraoperative measurement of IOP. This facilitates the use in scientific studies on surgical techniques. In the postoperative period the use of sterilized probes can reduce the risk of infection.

The impact of perinatal brain injury on retinal nerve fiber layer thickness and optic nerve head parameters of premature children

PURPOSE

This study aims to evaluate the impact of birth weight (BW), gestational age (GA), retinopathy of prematurity (ROP), and perinatal brain injury (PBI) on optic nerve head (ONH) parameters and nerve fiber layer thickness (RNFLT) in preterm children.

METHODS

ONH parameters and RNFLT were examined prospectively in 5-15-year-old preterm and full-term children with RTVue-100 OCT (Optovue, USA). The parameters of the two groups were compared and possible influences of BW, GA, ROP, and PBI analyzed in preterm children.

RESULTS

In total, 51 full-term and 55 preterm children were included. The mean age was 9.98 ± 3.4 years in full-term and 10.0 ± 2.5 years in preterm children. The mean GA in preterm children was 29.6 ± 3.8 weeks with a BW of 1523 ± 732 g. RNFLT was significantly lower in preterm than in full-term children in all but temporal quadrants. Cup area, volume, cup/disc area ratio, and horizontal cup/disc ratio (CDR) were significantly larger and rim area significantly thinner in preterm children. GA was positively correlated with superior, nasal, and overall RNFLT and negatively correlated with cup area, volume, and horizontal CDR. ROP stage correlated negatively with superior and nasal RNFLT. PBI was the only significant predicting factor for RNFL thinning in all but temporal quadrant in multiple regression analysis. Preterm children with PBI had a significantly larger optic cup (CDR 0.70 ± 0.33 vs. 0.37 ± 0.27) and thinner optic rim.

CONCLUSION

PBI correlated strongest with RNFL thinning, a thinner optic rim, and a larger optic cup in preterm children and should be evaluated in each patient to prevent incorrect diagnosis like glaucoma.

Iatrogenic Keratectasia after Refractive Surgery - Causes, Prophylaxis, Therapy

Iatrogenic keratectasia is induced thinning and protrusion of the cornea after laser refractive surgery. Known risk factors include an excessively thin postoperative residual stromal bed, a thicker flap, or preoperatively undetected evidence of preexisting subclinical keratoconus. The rate of post-refractive ectasia in eyes without identifiable preoperative risk factors is 20 per 100 000 eyes for photorefractive keratectomy, 90 per 100 000 eyes for laser in situ keratomileusis, and 11 per 100 000 eyes for small incision lenticule extraction. Traditional screening tools for preoperative risk include the ectasia risk score system and percentage of tissue alteration. More recent methods include corneal elastography and epithelial mapping, in addition to Artificial Intelligence methods for data analysis. Therapy includes contact lenses, cross-linking, implantation of intracorneal ring segments, penetrating or lamellar keratoplasty, and, in early studies, implantation of corneal lenticules.

Comparison of intraocular lens power calculation formulas with and without total keratometry and ray tracing in patients with previous myopic SMILE

PURPOSE

To evaluate the prediction error (PE) variance and absolute median PE of different intraocular lens (IOL) calculation formulas including last-generation formulas such as Barrett True-K with K, Okulix and total keratometry (TK)-based calculations with Haigis, and Barrett True-K in a simulation model in post-small-incision lenticule extraction (SMILE) eyes.

SETTINGS

Department of Ophthalmology, University Hospital Marburg, Marburg, Germany.

DESIGN

Prospective study.

METHODS

Preoperative measurements included IOL power calculation before and after SMILE surgery. The target refraction was set to be the lowest myopic refractive error in pre-SMILE eyes. The IOL power targeting at the lowest myopic refractive error in pre-SMILE eyes was selected for the post-SMILE IOL calculation of the same eye. The difference between the predicted refraction of pre- and post-SMILE eyes with the same IOL power was defined as IOL difference. The refractive change induced by SMILE was defined as the difference between preoperative and postoperative manifest refraction.

RESULTS

98 eyes from 49 patients underwent bilateral myopic SMILE. The PE variance of Okulix was not significantly different compared with Barrett True-K with TK ( P = .471). The SDs of the mean PEs were ±0.413 D (Haigis-TK), ±0.453 D (Okulix), ±0.471 D (Barrett True-K with TK), ±0.556 D (Haigis-L), and ±0.576 D (Barrett True-K with K). The mean absolute PE was 0.340 D, 0.353 D, 0.404 D, 0.511 D, and 0.715 D for Haigis-TK, Okulix, Barrett True-K with TK, Barrett True-K with K, and Haigis-L, respectively. The highest percentage of eyes within ±0.50 D was achieved by Okulix, followed by Haigis-TK, Barrett True-K with TK, Barrett True-K with K, and Haigis-L.

CONCLUSIONS

Results suggest that Haigis in combination with TK, Okulix, and Barrett True-K with and without TK offer good options for accurate IOL power calculation after SMILE. Haigis-L showed a tendency for myopic shift in eyes after previous SMILE.

Long-term surgical outcomes of two different Ahmed Valve implantation techniques in refractory glaucoma: Scleral flap vs scleral tunnel

PURPOSE

To compare the outcomes and complications of the partial-thickness scleral flap technique to the long scleral tunnel technique in patients who underwent mitomycin C (MMC)-augmented Ahmed glaucoma valve (AGV) implantation.

PATIENTS AND METHODS

In this retrospective study, we reviewed 139 eyes of 137 patients with refractory glaucoma who underwent AGV-Model FP7 implantation. The eyes were divided into the scleral flap group (n = 74) and the scleral tunnel group (n = 65).

RESULTS

The mean follow-up was 57.91 ± 18.18 months for the flap and 61.18 ± 15.13 months for the tunnel group (p = 0.2499). The postoperative intraocular pressure (IOP) at 1 to 6 years was significantly lower than the baseline IOP in each group (p < 0.001). The average number of postoperative glaucoma medications decreased in the tunnel group (p = 0.0001) and in the flap group (p = 0.6194) compared to baseline. No statistically significant differences in postoperative visual acuity (p = 0.6396) and cumulative success (p = 0.054) were noted between the two groups. Conjunctival erosion or tube migration only occurred in the flap group. Significantly more reoperations were performed in the flap than in the tunnel group (p = 0.048).

CONCLUSIONS

Both MMC-augmented AGV tube implantation methods lowered IOP. The flap technique was associated with higher rates of postoperative serious complications and more reoperations than the tunnel technique. Previous glaucoma surgery and the technique used to implant the surgical tube proved to be significant risk factors for conjunctival erosion.

SMILE for Hyperopia With and Without Astigmatism: Results of a Prospective Multicenter 12-Month Study

PURPOSE

To investigate the safety and effectiveness of small incision lenticule extraction (SMILE) in patients who have hyperopia with or without astigmatism.

METHODS

This was a prospective multicenter trial including 374 eyes of 199 patients treated by SMILE for hyperopia using the VisuMax femtosecond laser (Carl Zeiss Meditec AG). Inclusion criteria were sphere up to +6.00 diopters (D), cylinder up to 5.00 D, and maximum hyperopic meridian up to +7.00 D, with preoperative corrected distance visual acuity (CDVA) of 20/25 or better. The optical zone was 6.3 mm with a transition zone of 2 mm. The minimum lenticule thickness was set at 25 µm in the center and at 10 µm at the edge. Patients were examined at 1 day, 1 week, and 1, 3, 6, 9, and 12 months after surgery. Standard refractive surgery outcomes analysis was performed.

RESULTS

The preoperative spherical equivalent was +3.20 ± 1.48 D (range: +0.25 to +6.50 D). At the 12-month follow-up visit, 81% of eyes treated were within ±0.50 D and 93% of eyes were within ±1.00 D of intended correction. A total of 1.2% of eyes lost two or more lines of CDVA at the 12-month follow-up visit, and 83% were at least 20/20, corresponding to a safety index of 1.005 at 12 months. Of the 219 eyes with plano target, 68.8% had an uncorrected distance visual acuity of 20/20 or better and 88% were at least 20/25 uncorrected at 12 months. There were no statistically significant changes in contrast sensitivity.

CONCLUSIONS

SMILE was found to be an effective treatment method for the correction of compound hyperopic astigmatism, demonstrating a high level of efficacy, predictability, safety, and stability. [J Refract Surg. 2022;38(12):760-769.].

Twelve-year global publications on small incision lenticule extraction: A bibliometric analysis

Purpose

To analyze the development process of small incision lenticule extraction (SMILE) surgery in a 12-year period.

Methods

We conducted a literature search for SMILE research from 2011 to 2022 using the Science Citation Index Expanded (SCIE) of the Web of Science Core Collection (WoSCC). The VOS viewer, and CiteSpace software were used to perform the bibliometric analysis. Publication language, annual growth trend, countries/regions and institutions, journals, keywords, references, and citation bursts were analyzed.

Results

A total of 731 publications from 2011 to 2022 were retrieved. Annual publication records grew from two to more than 100 during this period. China had the highest number of publications (n = 326). Sixty-five keywords that appeared more than four times were classified into six clusters: femtosecond laser technology, dry eye, biomechanics, visual quality, complications, and hyperopia.

Conclusion

The number of literatures has been growing rapidly in the past 12 years. Our study provides a deep insight into publications on SMILE for researchers and clinicians with bibliometric analysis for the first time.

Corneal opacities after small-incision lenticule extraction

A 36-year-old woman was referred to our clinic in October 2021 with suboptimal vision at intermediate and near distances and halos and photophobia after a small-incision lenticule extraction (SMILE) in December 2019. The patient needs to increase font size of her computer to 150% to read text, but images still appear blurred. She indicates that sunglasses seem to improve her contrast. Preoperatively, her refractive error was -2.5 diopters (D) and -2.25 D for right and left eyes. The optical zone size of the SMILE procedure was 6.8 mm. There is no further information available on the peroperative course of the SMILE procedure. Her uncorrected distance visual acuity (UDVA) is 20/20 in both eyes and does not improve with correction. The Schirmer tear test is 14 to 13 mm. Slitlamp biomicroscopy of the right eye and the left eye reveals hyperreflective small opacities in the anterior one-third of the corneal stroma ( Figures 1 and 2JOURNAL/jcrs/04.03/02158034-202209000-00021/figure1/v/2022-08-29T115553Z/r/image-tiffJOURNAL/jcrs/04.03/02158034-202209000-00021/figure2/v/2022-08-29T115553Z/r/image-tiff ). No other abnormalities are seen. The scotopic pupil sizes are 6.41 and 6.73 mm. Straylight measurements are within normal limits. Higher-order aberrations (HOAs) measure for the right eye (6.03 mm pupil) 0.818 μm and for the left eye (6.17 mm pupil) 0.560 μm. The corneal Scheimpflug tomography quad maps for both eyes are shown in Supplemental Figures 1 and 2 ( http://links.lww.com/JRS/A663 , http://links.lww.com/JRS/A664 ). What is your diagnosis or are additional diagnostic methodologies needed to establish a diagnosis? What is your treatment advice for this patient?

Corneal Remodeling After Myopic SMILE Versus FS-LASIK: A Spatial Analysis of Short- and Mid-Term Corneal Thickness, Volume, and Shape Changes

PURPOSE

To evaluate the short- and mid-term changes of corneal thickness spatial profile (CTSP), corneal volume distribution (CVD), and corneal asphericity after small-incision lenticule extraction (SMILE) for correction of myopia and astigmatism and compare the results with femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).

METHOD

Thirty eyes of 18 patients who underwent SMILE were compared with a group of 30 eyes of 16 patients who underwent FS-LASIK. The groups were matched for preoperative central corneal thickness and lenticule thickness/ablation depth. Scheimpflug corneal tomography was performed preoperatively and postoperatively at 2 months and 3 years. The CTSP was evaluated on 4 concentric rings (2, 4, 6, and 8 mm). The CVD was evaluated at 3 concentric zones (3, 5, and 7 mm). Changes in the anterior and posterior asphericity at a 6-mm zone were also evaluated.

RESULTS

Between the 2-month and 3-year examination, the CTSP showed a similar increase for both groups at all measured points and rings ( P ≥ 0.168). The CVD also showed a similar increase for both groups at all measured zones ( P ≥ 0.278). The anterior corneal asphericity remained stable after SMILE (2-mo Q = 0.46 ± 0.27; 3-yr Q = 0.45 ± 0.27; P = 0.711) but decreased significantly after FS-LASIK (2-mo Q = 0.52 ± 0.47; 3-yr Q = 0.47 ± 0.44; P = 0.028). Similarly, the posterior corneal asphericity remained stable after SMILE (2-mo Q = -0.11 ± 0.15; 3-yr Q = -0.11 ± 0.13; P = 0.902) but decreased significantly after FS-LASIK (2-mo Q = -0.13 ± 0.14; 3-yr Q = -0.16 ± 0.15; P = 0.034).

CONCLUSIONS

CTSP and CVD between the 2-month and 3-year examination showed a similar increase after SMILE and FS-LASIK. During the postoperative course, the anterior and posterior corneal asphericity remained more stable after SMILE compared with FS-LASIK.

Five-year follow-up of corneal morphology and corneal refractive power changes after uneventful DMEK

PURPOSE

To investigate changes of corneal thickness spatial profile (CTSP), corneal volume (CV) distribution, and total corneal refractive power (TCRP) over a course of 60 months after uneventful Descemet membrane endothelial keratoplasty (DMEK).

METHODS

In our prospective, comparative study, sixty DMEK cases without intraoperative and postoperative complications and with complete 60-month follow-up were included (group 1). CTSP at corneal apex (CCT) and at 2 mm, 4 mm, 6 mm, and 8 mm rings, CV in 3 mm, 5 mm, 7 mm, and 10 mm zones, and TCRF in 2 mm, 4 mm 6 mm, and 8 mm zones were evaluated preoperatively and at 3, 6, 12, 24, and 60 months postoperatively. The 60-month results were compared to an age-matched group of uncomplicated pseudophakic eyes (group 2; n = 20).

RESULTS

The CCT and CTSP at 2, 4, and 6 mm increased significantly at 60 months compared to 3-month outcomes (P < 0.001). Similarly, CV increased significantly in 3 mm, 5 mm, and 7 mm zones at 60 months compared to 3 months outcomes (P < 0.001). The TCRP showed in all zones a significant decrease at 3 months (P < 0.001) followed by a continuous and significant increase at 60 months (P < 0.001). The 60-month CCT and CTSP at 2 mm were similar to group 2 (P ≥ 0.094).

CONCLUSION

Sixty months after uneventful DMEK, CT within the central 2 mm zone and CV at 3 mm zone were similar to uncomplicated pseudophakic eyes. A continuous and statistically significant increase of TCRP was observed in all measured zones after the 3-month examination.

Hyperopic SMILE Versus FS-LASIK: A Biomechanical Comparison in Human Fellow Corneas

PURPOSE

To investigate the biomechanical properties of ex vivo human paired corneas after hyperopic correction via cap-based versus flap-based laser-assisted refractive surgery.

METHODS

In this prospective experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. The pachymetry was performed in each eye just before the laser procedure. Corneas from the right eye were treated with small incision lenticule extraction (SMILE), whereas corneas from the left eye of the same donor were treated with femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). All corneas were subjected to a refractive correction of +6.00 diopters (D) sphere with a 6.5-mm zone under a 120-µm cap (SMILE) or a 7-mm zone under a 110-µm flap (FS-LASIK). For two-dimensional biomechanical measurements, the corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 seconds) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%.

RESULTS

In stress-strain measurements, the effective elastic modulus was not significantly different (P > .311) between SMILE (13.5 ± 12.8 MPa) and FS-LASIK (7.56 ± 17.9 MPa). In stress-relaxation measurements, the remaining stress was not significantly different (P = .841) between SMILE (124 ± 20 kPa) and FS-LASIK (126 ± 21 kPa).

CONCLUSIONS

Unlike myopic correction, after hyperopic correction the cap-based procedure (SMILE) and the flap-based technique (FS-LASIK) may be considered equivalent in terms of biomechanical stability when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2021;37(12):810-815.].

Patient-Reported Quality of Life and Satisfaction After Refractive Lens Extraction Using a Diffractive Trifocal IOL: A Multicenter Retrospective Cohort Study

PURPOSE

To assess patient satisfaction and quality of life after refractive lens exchange with a trifocal intraocular lens (IOL).

METHODS

Consecutive patients who underwent refractive lens exchange with the AT LISA tri or AT LISA tri toric IOL (Carl Zeiss Meditec AG) at one of five surgical centers were surveyed for their quality of life and satisfaction after surgery using a standardized questionnaire. Patient responses were compared to patient characteristics such as age, sex, axial lengths, and preoperative refraction.

RESULTS

A total of 102 patients with 204 treated eyes were included in the analysis. The mean age was 54.6 ± 5.2 years. A total of 172 eyes were hypermetropic, 3 were emmetropic, and 25 were myopic, with a mean preoperative refractive error of 0.93 ± 2.17 diopters. Reported postoperative satisfaction was as follows: 81.4% stated that their expectations were completely met and 17.6% stated that they were partially met. Self-reported refractive error quality of life improved significantly in all queried areas of life. Most frequently reported postoperative limitations were driving at night and driving in bad weather conditions. Halos were reported by 91 (90.1%) patients.

CONCLUSIONS

Patient satisfaction and self-reported quality of life after refractive lens exchange with the AT LISA tri or AT LISA tri toric IOL was high. Glare and halos remain the only significant drawback of the procedure, leading to 40% of patients experiencing difficulties in night driving. Preoperative communication of these drawbacks is obligatory to avoid postoperative disappointment. [J Refract Surg. 2021;37(11):768-774.].

Nighttime Symptoms After Monocular SMILE: A Contralateral Eye Study

Introduction

To investigate nighttime symptoms in patients with myopic anisometropia after monocular small incision lenticule extraction (SMILE) surgery.

Methods

Thirty-six patients who had undergone monocular SMILE more than 6 months previously were recruited at the Eye & ENT Hospital of Fudan University. The average age at surgery was 25.4 ± 6.1 years. Preoperative spherical equivalent (SE) was −3.77 ± 1.56 D in SMILE-treated eyes and −0.08 ± 0.66 D in unoperated eyes. Main measurements included uncorrected and corrected distance visual acuity, manifest refraction, halo radius, contrast sensitivity, nighttime symptoms, and patient satisfaction.

Results

The mean follow-up time was 13.9 ± 3.4 months. The efficacy and safety indexes were 1.18 and 1.28, respectively. The halo radius was not significantly different between SMILE-treated and unoperated eyes under luminance conditions of 1, 5, and 100 cd/m² (P = 0.055). No significant differences were observed in contrast sensitivity at all spatial frequencies between eyes under both uncorrected and corrected conditions (all P > 0.05). None of the patients reported moderate or severe symptoms at night. Mild symptoms (glare, halo, starburst) were reported and binocularly equal in 13 patients, whereas four patients reported better night vision in SMILE-treated eyes than unoperated eyes, and one of them experienced mild night vision disturbance. The overall satisfaction score was 9.39 ± 0.80.

Conclusions

The disk halo size and contrast sensitivity in SMILE-treated eyes were similar to those in unoperated eyes, and nighttime symptoms almost completely resolved after SMILE.

Secondary DMEK following failed primary DMEK

PURPOSE

To report the outcomes of secondary Descemet Membrane Endothelial Keratoplasty (DMEK) performed for failed primary DMEK.

METHODS

The medical records of all patients undergoing secondary DMEK due to failure of primary DMEK were reviewed. Reasons for failure were sought and best-corrected visual acuity (BCVA), endothelial cell density (ECD) and complications of secondary DMEK were evaluated.

RESULTS

A total of 10 cases undergoing secondary DMEK following failed primary DMEK were identified. Presumed reasons for failure included donor ECD ≤ 2300 cells/mm² (n = 4), difficulty during graft preparation (n = 2), graft detachment (n = 2), acute angle closure due to retroiridal air dislocation (n = 1), inverse graft positioning (n = 1) and phacoemulsification (n = 1). Eyes with low visual potential were not excluded from the study group. We should note that one patient (case no7) had both low ECD and graft detachment as reasons for failure and as a result he is counted twice. Median BCVA (decimal fraction) increased from 0.1 (range, 0.01; 0.3) to 0.5 (0.05; 1.0) at one month and remained stable thereafter. A BCVA of 0.5 or higher was achieved in 7 cases at the final follow-up. Mean ECD fell from 2628 ± 284 cells/mm² to 1391 ± 252cells/mm² at 6 months (47% reduction) and 959 ± 225cells/mm² at 24 months (64% reduction) (P ≤ 0.028). Complications included the incomplete removal of the primary graft and mild iris bleeding, decompensation of a preexisting primary open-angle glaucoma and retroiridal air dislocation.

CONCLUSIONS

Apart from low donor ECD, surgical challenges, i.e., difficulty with graft preparation, inverse graft positioning, and retroiridal air dislocation, were main reasons for failure of primary DMEK. Secondary DMEK showed a good safety profile and reasonable visual outcomes.

The impact of vitrectomy on outcomes achieved with 0.19 mg fluocinolone acetonide implant in patients with diabetic macular edema

BACKGROUND

There is a lack of consensus on the use of intravitreal corticosteroid therapies in patients with diabetic macular edema (DME) and prior vitrectomized eyes in clinical practice.

METHODS

Retro-IDEAL was a 3-year retrospective, multicenter study in patients with chronic DME (i.e. DME that persists or recurs despite treatment) treated with ILUVIEN® (0.2 µg daily fluocinolone acetonide intravitreal implant), who had suboptimal outcomes with first-line vascular endothelial growth-factor inhibitors and other DME therapies.

RESULTS

A total of 81 eyes (63 patients) were included of which 39 eyes had undergone prior vitrectomy (PV group) while 42 eyes had not undergone prior vitrectomy (NPV). Baseline characteristics were balanced; however, more patients had proliferative diabetic retinopathy in the PV group vs. the NPV group (21.62% vs 9.38%, respectively). Over 36 months, mean visual acuity (VA) increased in both groups with a tendency for more ETDRS letters being gained in the NPV group (+5.33) vs. the PV group (+2.42). By month 36, central retinal thickness was reduced to ⩽300 µm in two-thirds of the eyes in both groups and the mean change from baseline in intraocular pressure was similar in both groups (+0.50 mmHg -0.75 mmHg; NPV and PV group).

CONCLUSIONS

These long-term data suggest that the 0.2 μg/day FAc implant is effective in both vitrectomized and non-vitrectomized patients, with a manageable safety profile, and improved VA and reduced supplemental therapies for patients with a suboptimal response to first-line DME therapies. Clinicians may consider utilizing the FAc implant earlier in the DME disease process.

Quasi-Static Optical Coherence Elastography to Characterize Human Corneal Biomechanical Properties

Purpose

Quasi-static optical coherence elastography (OCE) is an emerging technology to investigate corneal biomechanical behavior in situations similar to physiological stress conditions. Herein OCE was applied to evaluate previously inaccessible biomechanical characteristics of human corneal tissue and to study the role of Bowman's layer in corneal biomechanics.

Methods

Human corneal donor buttons (n = 23) were obtained and Descemet's membrane and endothelium were removed. In 11 corneas, Bowman's layer was ablated by a 20 µm stromal excimer laser ablation. Buttons were mounted on an artificial anterior chamber and subjected to a pressure modulation from 10 to 30 mm Hg, and back to 10 mm Hg, in steps of 1 mm Hg. At each step, a spectral-domain optical coherence tomography scan was obtained. Displacements were analyzed by optical flow tracking, and strain over the entire stromal depth was retrieved from the phase gradient of the complex interference signal.

Results

During pressure increase, corneal tissue moved upward (486–585 nm/mm Hg) but did not fully recover (Δ= 2.63 to 8.64 µm) after pressure decrease. Vertical corneal strain distribution was negative in the anterior and positive in the posterior cornea, indicating simultaneous corneal compression and expansion, respectively. Bowman's layer caused minor localized differences in corneal strain distribution.

Conclusions

Corneal strain distribution is more complex than previously assumed, with a fundamental difference in mechanical response between the anterior and posterior stroma. Clinically, OCE technology might be used to monitor the progression of corneal ectatic diseases and to determine the success of corneal cross-linking.

Similar Biomechanical Cross-linking Effect After SMILE and PRK in Human Corneas in an Ex Vivo Model for Postoperative Ectasia

PURPOSE

To evaluate the biomechanical effect of corneal cross-linking (CXL) in paired human corneas following small incision lenticule extraction (SMILE) or photorefractive keratectomy (PRK) in an ex vivo model for postoperative ectasia.

METHODS

Twenty-six paired human corneas preserved in tissue culture medium were equally divided into two groups: right and left corneas were treated with PRK and SMILE, respectively. Corneal thickness was measured in all eyes before surgery. Corneas were stretched using an extensometer with two cycles of up to 9 N (570 kPA stress), followed by accelerated CXL with irradiance of 9 mW/cm² for 10 minutes (fluence 5.4 J/cm²) in both groups. The elastic modulus was evaluated using two-dimensional stress-strain extensometry.

RESULTS

Following accelerated CXL, the ectatic cornea model showed a mean effective elastic modulus of 17.2 ± 5.3 MPa after PRK and 14.1 ± 5.0 MPa after SMILE. Although the elastic modulus in corneas previously subjected to PRK was higher, there was no significant biomechanical difference between the two groups (P = .093).

CONCLUSIONS

Under similar conditions, both experimental groups (PRK followed by CXL and SMILE followed by CXL) were characterized by similar biomechanical stability as measured experimentally on ex vivo human fellow corneas. The data suggest that, in the event of postoperative ectasia, the biomechanical improvement achieved by CXL may be similar after PRK and SMILE. [J Refract Surg. 2020;36(1):49-54].

Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: PRK Versus SMILE

PURPOSE

To investigate the biomechanical properties of the ex vivo human paired corneas after completion of photorefractive keratectomy (PRK) versus small incision lenticule extraction (SMILE) in the same donor.

METHODS

In this experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneal thickness was measured in each eye directly before laser refractive surgery. Corneas from the right eye were treated with PRK and corneas from the left eye with SMILE. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7 mm zone, using either surface ablation (PRK) or 130 µm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 seconds) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%.

RESULTS

In stress-strain measurements, the effective elastic modulus was not significantly different (P = .081) between SMILE (9.58 ± 4.26 MPa) and PRK (11.9 ± 4.90 MPa). The effect size was medium (Cohen's d = 0.58). In stress-relaxation measurements, the remaining stress was not significantly different (P = .878) between SMILE (122 ± 33 kPa) and PRK (123 ± 30 kPa).

CONCLUSIONS

The lenticule extraction procedure (SMILE) and the surface ablation technique (PRK) may be considered equivalent in terms of biomechanical stability when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2019;35(8):501-505.].

10-Year Results of FLEx Refractive Surgery

PURPOSE

To evaluate the 10-year results of femtosecond lenticule extraction (FLEx) for treatment of myopia and myopic astigmatism.

METHODS

This long-term follow-up of a prospective clinical trial was conducted at HELIOS Klinikum Erfurt and Phillips University of Marburg, Germany. In 2006, 108 eyes underwent the FLEx procedure. All patients were invited for reexamination 10 years after FLEx treatment for myopia and astigmatism. Visual acuity, objective and manifest refraction, intraocular pressure, and slit-lamp examination and side effects were documented. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity, objective and manifest refraction, and slit-lamp examination and side effects.

RESULTS

A total of 77 eyes of 40 patients of the original treatment group volunteered for a reexamination 10 years after surgery. The mean age of the patients was 45.9 years; 26 were women and 14 were men. UDVA was 0.09 ± 0.19 logMAR and CDVA was stable at -0.1 ± 0.09 logMAR. More than half of the eyes gained one or two Snellen lines, and none of the eyes lost two or more lines. Over the 10-year period, regression was 0.18 D.

CONCLUSIONS

FLEx has stable results 10 years after treatment for myopia and astigmatism. [J Refract Surg. 2019;35(11):707-711.].

Trabeculectomy offers better intraocular pressure reduction in intrapatient comparison to transscleral cyclophotocoagulation

PURPOSE

Both trabeculotomy (TE) as well as transscleral endodiode laser cyclophotocoagulation (CPC) are common approaches in glaucoma surgery. The purpose of this study was to perform an intraindividual comparison of these procedures carried out by the same surgeon in the same patient on the same day.

METHODS

An observational monocentric retrospective cohort study was conducted. Patients with a bilateral refractory open-angle glaucoma who underwent trabeculectomy in one eye and transscleral endodiode laser cyclophotocoagulation in the fellow eye simultaneously were included and followed up with over the course of 1 year.

RESULTS

Eighty-two eyes of 41 patients were included. Seventeen patients (41.5%) were men and 24 (58.5%) women. The mean age was 68.7 ± 9.5 years. The diagnosis comprised 33 (80.5%) patients with a primary open-angle glaucoma, five (12.2%) patients with pseudoexfoliation glaucoma, and three (7.3%) patients with pigment dispersion glaucoma. A reduction in intraocular pressure (IOP) was seen in both after TE (from 26.2 ± 13.2 to 10.6 ± 4.1 mmHg, 52 weeks post-treatment) as well as CPC (from 24.2 ± 9.9 to 15.0 ± 5.4 mmHg, 52 weeks post-treatment). In comparison to each other, TE was significantly more effective in lowering the IOP (10.6 ± 4.1 vs. 13.4 ± 5.0; p = 0.0030, 52 weeks post-treatment) and needed antiglaucomatous medications (0.45 ± 0.80 vs. 1.24 ± 1.13; p = 0.0009, 52 weeks post-treatment). Consistently, the achievement rate of an IOP ≤ 16 mmHg without antiglaucomatous medications was significantly higher in TE-treated eyes (65.8% vs. 31.6%; p = 0.0019). Re-interventions, including 10 secondary TEs, were commonly required in those eyes undergoing CPC, especially in younger patients.

CONCLUSIONS

Trabeculectomy was demonstrated to be more effective in reducing IOP in comparison to fellow eyes receiving CPC. In particular, in younger patients, an additional TE in the CPC-treated eyes was necessary. The outcome of those secondary TEs however was comparable to the primarily performed TEs. Our study thus supports the use of CPC as tool to control IOP, especially in the context of bilateral refractive glaucoma.

Therapy-resistant dry itchy eyes

An 8 years old male presented to our clinic with dry eye symptomes. Different therapiy attemps were made in the last few months and did not lead to any improvement. Examining this patient revealed multiple signs of vitamin A deficiency, which could confirmed by laboratory examination. The initial substitution of vitamin A led to a fast rehabilitation and a following nutrition consulting kept the patient symptom-free over 6 month follow up. Vitamin A deficiency -although rare in the developed countries- is an importent differential diagnosis of the dry eye especially in children. Vitamin A deficiency not only causes ocular manifistaion, but also general symptoms. Dietary change and initial subtitution is the key element for a fast and sustaining improvement.

Surface Ablation Versus CIRCLE for Myopic Enhancement After SMILE: A Matched Comparative Study

PURPOSE

To compare the outcomes of enhancement after small incision lenticule extraction (SMILE) using surface ablation versus the VisuMax CIRCLE option (Carl Zeiss Meditec AG, Jena, Germany), which converts the SMILE cap into a femtosecond laser-assisted laser in situ keratomileusis flap.

METHODS

The databases of the SMILE Eyes centers in Munich, Marburg, and Cologne, Germany, and Linz, Austria, were screened for eyes that had undergone enhancement using surface ablation with mitomycin C or CIRCLE. Eyes from both enhancement methods suitable for a retrospective matched analysis were identified based on pre-SMILE and pre-enhancement mean refractive spherical equivalent (MRSE), astigmatism, age, and corrected and uncorrected distance visual acuity (CDVA/UDVA). Refractive and functional outcomes were compared after a follow-up of 3 months.

RESULTS

After the application of the matching criteria on 2,803 SMILE procedures, 24 eyes (12 in each group) with a follow-up of 3 months or longer were available for analysis. Enhancement was performed after a mean 9.7 ± 7.2 (surface ablation) and 11.0 ± 4.4 (CIRCLE) months for a residual MRSE of -0.91 ± 0.55 (surface ablation) and -0.90 ± 0.61 (CIRCLE) diopters. At 3 months, residual MRSE showed comparable accuracy with -0.07 ± 0.19 (surface ablation) and 0.04 ± 0.22 (CIRCLE) diopters (P = .18). UDVA improvement was similar to a final value of 0.02 ± 0.10 (surface ablation) versus 0.03 ± 0.07 (CIRCLE) logMAR (P = .78). Only one eye in the surface ablation group and no eye in the CIRCLE group lost one line of CDVA. At 3 months, the safety (surface ablation: 1.00, CIRCLE: 1.06; P = .36) and efficacy (surface ablation: 0.95, CIRCLE: 1.03; P = .36) indices were equivalent. In terms of speed of visual recovery, at week 1 UDVA and CDVA were significantly better after CIRCLE than surface ablation (P = .008 and .002, respectively).

CONCLUSIONS

In this first study directly comparing surface ablation versus CIRCLE enhancement after SMILE, both methods yielded comparable results at 3 months. However, CIRCLE re-treated eyes showed a markedly increased speed of recovery concerning UDVA and CDVA compared to surface ablation. [J Refract Surg. 2019;35(5):294-300.].

Small Incision Lenticule Extraction for Hyperopia: 3-Month Refractive and Visual Outcomes

PURPOSE

To evaluate visual and refractive outcomes of small incision lenticule extraction (SMILE) for hyperopia.

METHODS

This prospective study of vertex-centered hyperopic SMILE used the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D) and corrected distance visual acuity (CDVA) of 20/40 or better. Lenticule parameters were 6.3- to 6.7-mm diameter, 2-mm transition zone, 30-µm minimum thickness, and 120-µm cap thickness. Standard outcomes analysis was performed for the 3-month data, including contrast sensitivity using the Functional Vision Analyzer.

RESULTS

For 93 eyes treated, 3-month data were available for 82 (88%). Attempted spherical equivalent refraction was +5.62 ± 1.20 D (range: +1.00 to +6.90 D) and cylinder was -0.91 ± 0.68 D (range: 0.00 to -3.50 D). For eyes targeted for emmetropia (n = 36), uncorrected distance visual acuity was 20/40 or better in 89%. Spherical equivalent refraction relative to target was -0.17 ± 0.85 D (range: -2.20 to +3.00 D), with 59% within ±0.50 D and 76% within ±1.00 D. There was one line loss of CDVA in 17% of eyes, and one eye lost three lines (1.2%) but recovered to one line lost at 9 months. There was no clinically significant change in contrast sensitivity.

CONCLUSIONS

Refractive and visual outcomes 3 months after SMILE for hyperopia were promising, given the high degree of hyperopia corrected and relatively reduced CDVA in this population. Undercorrection of more than 1.00 D in 5 eyes might be partly explained by latent hyperopia in these young patients. [J Refract Surg. 2019;35(1):24-30.].

Three-year results from the Retro-IDEAL study: Real-world data from diabetic macular edema (DME) patients treated with ILUVIEN® (0.19 mg fluocinolone acetonide implant)

INTRODUCTION

The Retro-IDEAL (ILUVIEN Implant for chronic DiabEtic MAcuLar edema) study is a retrospective study designed to assess real-world outcomes achieved with the ILUVIEN® (0.19 mg fluocinolone acetonide (FAc)) in patients with chronic diabetic macular edema (DME) in clinical practices in Germany.

METHODS

This study was conducted across 16 sites in Germany and involved 81 eyes (63 patients) with persistent or recurrent DME and a prior suboptimal response to a first-line intravitreal therapy (primarily anti-VEGF intravitreal therapies).

RESULTS

Patients were followed-up for 30.8 ± 11.3 months (mean ± standard deviation) and had a mean age of 68.0 ± 10.4 years. Best-recorded visual acuity (BRVA) improved by +5.5 letters at month 9 (P ⩽ 0.005, n=56; from a baseline of 49 letters) and this was maintained through to month 30 (P ⩽ 0.05, n = 42). There was a concurrent improvement in central macular thickness with a reduction from 502 µm at baseline to 338 µm at year 1 (P ⩽ 0.0001, n = 43). This effect was sustained to year 3 (i.e. 318 µm; P ⩽ 0.0001, n = 29). Mean intraocular pressure (IOP) remained constant between baseline and year 3 with a peak change of 1.9 mm Hg occurring at year 1. Elevated IOP was observed in a similar percentage of patients prior to (22.2% of cases) and following (27.2%) treatment with the FAc implant. In the majority of cases, these elevations were managed effectively with IOP medications.

CONCLUSIONS

Despite substantial amounts of prior intravitreal treatments - primarily with anti-vascular endothelial growth factor (VEGF) drugs - this real-world study showed that sustained structural and functional improvements can last for up to 3 years with a single FAc implant.

Flushing versus not flushing the interface during small-incision lenticule extraction

PURPOSE

To assess the differences in outcomes between interface flushing with a balanced salt solution after refractive lenticule removal in simultaneous uneventful bilateral small-incision lenticule extraction (SMILE).

SETTING

Six study centers in Germany.

DESIGN

Prospective case series.

METHODS

Patients with myopia or myopic astigmatism of similar magnitude in both eyes with a spherical equivalent less than or equal to 10.0 diopters (D), preoperative corrected distance visual acuity (CDVA) of 0.80 decimal or better, and anisometropia less than or equal to 2.0 D were enrolled and followed for 3 months. One eye of each patient was treated with interface flushing after dry extraction of the lenticule. Flushing was performed with 1.0 cc balanced salt solution using a single-use 27-gauge cannula. The uncorrected distance visual acuity (UDVA) at 1 day, 1 week, and 3 months; the CDVA at 3 months; and postoperative differences at the slitlamp examination were recorded. Statistical analyses were performed with logarithm of the minimum angle of resolution values using paired t tests. The P value for significance was less than 0.05.

RESULTS

The study analyzed 470 eyes. One day postoperatively, the mean UDVA was 0.81 in the non-flush group and 0.83 in the flush group (P = .110). At the last visit 3 months postoperatively, the mean UDVA was 1.04 and 1.05, respectively (P = .172). No significant differences in the rate of postoperative complications were found.

CONCLUSION

Interface irrigation with 1.0 cc of balanced salt solution after the removal of the refractive lenticule has neither advantages nor disadvantages in terms of visual recovery, postoperative complications, or final visual acuity.

Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: Femtosecond Laser-Assisted LASIK Versus SMILE

PURPOSE

To investigate the biomechanical properties of the ex vivo human cornea after flap-based versus cap-based laser refractive surgery in the same donor.

METHODS

In this experimental study, 11 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneas from the right eye were treated with femtosecond laser-assisted LASIK (FSLASIK) and corneas from the left eye with small incision lenticule extraction (SMILE). Pachymetry was measured in each eye directly before laser refractive surgery. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7-mm zone, using either a 110-μm flap (FS-LASIK) or 130-μm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 sec) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%.

RESULTS

In stress-strain measurements, the effective elastic modulus was 1.47 times higher (P = .003) after SMILE (median = 8.22 [interquartile range = 4.76] MPa) compared to FS-LASIK (median = 5.59 [inter-quartile range = 2.77] MPa). The effect size was large (r = 0.83). No significant differences (P = .658) were observed among stress-relaxation measurements, with a mean remaining stress of 181 ± 31 kPa after SMILE and 177 ± 26 kPa after FS-LASIK after relaxation.

CONCLUSIONS

Compared to a flap-based procedure such as FS-LASIK, the SMILE technique can be considered superior in terms of biomechanical stability, when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2018;34(6):419-423.].

Early visual outcomes and optical quality after femtosecond laser small-incision lenticule extraction for myopia and myopic astigmatism correction of over -10 dioptres

PURPOSE

To investigate early visual and refractive outcomes, corneal stability and optical quality after femtosecond laser small-incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism over -10 D.

METHODS

Thirty eyes (30 patients) with myopia and myopic astigmatism of over -10 D were treated with VisuMax^® femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany). Six months postoperative safety, efficacy and predictability were evaluated. Corneal Scheimpflug topography was measured preoperatively, 1 day, 3 months and 6 months postoperatively. Wavefront aberrations were measured preoperatively, 3 months and 6 months postoperatively.

RESULTS

Six months postoperatively, LogMAR uncorrected and corrected distance visual acuity (CDVA) were -0.013 ± 0.086 and -0.073 ± 0.069, respectively. 73% (97%) of eyes were within 0.5 (1) D of target refraction. No eyes lost CDVA, 43% (13 eyes) gained one line and 7% (two eyes) gained two lines. Mean corneal back curvature (KMB) and posterior central elevation (PCE) did not change significantly comparing preoperative and 6 months postoperative data (p = 0.91 and 0.77, respectively). Comparing 1 day with 6 months postoperative data, central corneal thickness (CCT), mean corneal front curvature (KMF), KMB and PCE did not change significantly (p = 0.27, 0.07, 0.52, 0.71, respectively). Total higher-order aberration (HOA), spherical aberration and coma increased significantly (p < 0.01) but trefoil remained stable (p = 0.49).

CONCLUSION

Our results indicate that SMILE can correct myopia and myopic astigmatism of over -10 D predictably. No early ectasia was observed. Long-term changes in visual quality and corneal stability require further investigation.

Endothelial keratoplasty in eyes with a retained angle-supported intraocular lens

PURPOSE

To describe the outcomes of endothelial keratoplasty (EK) for bullous keratopathy in eyes with a retained angle-supported anterior chamber intraocular lens (acIOL).

METHODS

Among 263 consecutive EK procedures, 7 DMEK and 11 DSAEK procedures were identified in eyes with an acIOL and included in the present retrospective case series. Pre- and postoperative status including ocular history, anatomical outcome and complications as well as best-corrected visual acuity was evaluated.

RESULTS

Ocular history included complicated cataract surgery (n = 11), ocular trauma (n = 4) and primary intracapsular cataract extraction (n = 3). Surgery-related complications included primary graft failure (n = 1), graft detachment (n = 1), endophthalmitis (n = 1) and allograft rejection (n = 1). A clear cornea at the final examination (14 ± 4 months) was observed in 14/18 (78%), while the visual outcome was limited due to significant ocular comorbidity in 9 out of 14 uncomplicated procedures.

CONCLUSION

The presented short-term outcomes suggest that both DMEK and DSAEK are feasible in eyes with an angle-supported acIOL yielding an acceptable graft survival rate in the first postoperative year.

Lidocaine-Assisted Xylocaine Jelly Anesthesia versus one Quadrant Sub-Tenon Infiltration for Self-Sealing Sclerocorneal Incision Routine Phacoemulsification

Purpose

To compare the effect of Xylocaine jelly and intracameral lidocaine with one quadrant instant sub-Tenon infiltration for self-sealing sclerocorneal phacoemulsification.

METHODS

One hundred patients were enrolled into a prospective randomized study, receiving either a combination of topical 2% Xylocaine jelly and 0.5 ml of intracameral 1% lidocaine or sub-Tenon infiltration with 2 ml of 2% Xylocaine on the operating table. All patients underwent a standard divide and conquer phacoemulsification procedure through a superior sclerocorneal frown incision followed by implantation of a polymethylmethacrylate intraocular lens. Intraoperative pain was indicated by the patient by squeezing the bedside nurse's hand, who allocated it to particular stages of surgery on a chart. After surgery, patients assessed the pain experienced using a 10-unit visual analogue scale.

Results

Pain was indicated on 31 occasions during the operation in the sub-Tenon group (mainly the injection itself) and 67 times in the topical group. The median overall subjective pain score was 3 in the jelly group and 0 in the sub-Tenon. Five eyes (10%) had to be converted to sub-Tenon during the surgery because of intolerable pain.

CONCLUSIONS

Whereas lidocaine supported Xylocaine jelly anesthesia provided acceptable analgesia for 90% of patients operated, sub-Tenon anesthesia proved to deliver better intraoperative comfort in all patients receiving sclerocorneal incision cataract surgery.

Comparison of Optic Disc Parameters in Hyperopic and Emmetropic Eyes of Healthy Children with HRT and OCT

Purpose To investigate, through Heidelberg retina tomography II (HRT II) and RTVue-100 optical coherence tomography (OCT), normal parameters of the optic nerve head (ONH) in highly hyperopic children, and compare these with a group of children with low hyperopia and emmetropia, as fundus examination of highly hyperopic children often shows crowding of the optic disc, which may be difficult to distinguish from mild optic disc swelling.

Patients and Methods ONH of the higher hyperopic eye was examined with HRT II and the peripapillary nerve fiber layer (RNFL) with RTVue-100, in 6 to 15-year-old full-term children with normal visual acuity and spherical equivalent ≥ + 3.0 D (hyperopic group) and < + 3.0 to − 1.0 D (emmetropic group).

Results Thirty highly hyperopic children and 33 emmetropic controls had a mean spherical equivalent of + 5.1 ± 1.5 D and a mean age of 8.4 ± 2.8 years, and + 1.0 ± 1.2 D and 9.6 ± 2.6 years, respectively. There was no significant difference in OCT-assessed RNFL thickness between the two groups. Compared to the emmetropic group, following HRT parameters were significantly smaller in the hyperopic group: Disc area (1.41 vs. 1.68 mm2, p = 0.023), cup area (0.19 vs. 0.37 mm2, p = 0.0001), cup volume (0.03 vs. 0.08 mm3, p = 0.02), cup/disc area (0.13 vs. 0.20, p = 0.006), linear cup/disc (0.33 vs. 0.42, p = 0.004), and mean cup depth (0.13 vs. 0.17 mm, p = 0.019).

Conclusion In children, ONH of highly hyperopic eyes are smaller than those of emmetropic eyes. RNFL thickness and neural rim volume are similar to emmetropic eyes. They can therefore appear more crowded.

[Refractive lenticule extraction - The ReLEx/SMILE technique : Video article]

Refractive lenticule extraction (ReLEx/SMILE) is a refractive surgical method developed by the authors in stages primarily for correction of myopia and myopic astigmatism, in which a femtosecond laser is exclusively used. In the (ReLEx/SMILE) method a refractive lenticule is generated by the femtosecond laser, which is subsequently extracted through a small incision. Opening of the corneal surface with a flap and use of an excimer laser is no longer necessary. In 2013 the method was newly assessed and classified by the Joint Commisssion for Refractive Surgery (KRC) of the Professional Association of Ophthalmologists (BVA) and the German Ophthalmological Society (DOG). This article presents the individual stages of the technique in a video and possible errors and their avoidance are explained.

Retinopathy with central oedema in an INS C94Y transgenic pig model of long-term diabetes

AIMS/HYPOTHESIS

Diabetic retinopathy is a severe complication of diabetes mellitus that often leads to blindness. Because the pathophysiology of diabetic retinopathy is not fully understood and novel therapeutic interventions require testing, there is a need for reliable animal models that mimic all the complications of diabetic retinopathy. Pig eyes share important anatomical and physiological similarities with human eyes. Previous studies have demonstrated that INS ^C94Y transgenic pigs develop a stable diabetic phenotype and ocular alterations such as cataracts. The aim of this study was to conduct an in-depth analysis of pathological changes in retinas from INS ^C94Y pigs exposed to hyperglycaemia for more than 2 years, representing a chronic diabetic condition.

METHODS

Eyes from six INS ^C94Ypigs and six age-matched control littermates were analysed via histology and immunohistochemistry. For histological analyses of retinal (layer) thickness, sections were stained with H&E or Mallory's trichrome. For comparison of protein expression patterns and vessel courses, sections were stained with different antibodies in immunohistochemistry. Observed lesions were compared with reported pathologies in human diabetic retinopathy.

RESULTS

INS ^C94Ypigs developed several signs of diabetic retinopathy similar to those seen in humans, such as intraretinal microvascular abnormalities, symptoms of proliferative diabetic retinopathy and central retinal oedema in a region that is cone rich, like the human macula.

CONCLUSIONS/INTERPRETATION

The INS ^C94Ypig is an interesting model for studying the pathophysiology of diabetic retinopathy and for testing novel therapeutic strategies.

Biomechanical Differences Between Femtosecond Lenticule Extraction (FLEx) and Small Incision Lenticule Extraction (SmILE) Tested by 2D-Extensometry in Ex Vivo Porcine Eyes

Purpose

To evaluate the biomechanical stability of ex vivo porcine corneas after femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SmILE) refractive surgeries.

Methods

Forty-five porcine eyes were equally divided into three groups: Groups 1 and 2 were treated with FLEx and SmILE procedure, respectively. Group 3 served as control. A refractive correction of -14 diopters (D) with a 7-mm zone using either a 160-μm flap (FLEx) or a 160-μm cap (SmILE) was performed. For two-dimensional (2D) elastic and viscoelastic biomechanical characterization, two testing cycles (preconditioning stress-strain curve from 1.27 to 12.5 N, stress-relaxation at 12.5 N during 120 seconds) were conducted. Young's modulus and Prony constants were calculated.

Results

At 0.8% of strain, FLEx (370 ± 36 kPa) could resist a significantly lower stress than SmILE (392 ± 19 kPa, P = 0.046) and the control group (402 ± 30 kPa, P = 0.013). Also, FLEx (46.1 ± 4.5 MPa) had a significantly lower Young's modulus than the control group (50.2 ± 3.4 MPa, P = 0.008). The Young's modulus of SmILE (48.6 ± 2.5 MPa) had values situated between untreated corneas and FLEx-treated corneas. When compared to untreated controls, the stress resistance decreased by 8.0% with FLEx and 2.5% with SmILE; Young's modulus decreased by 5.1% with FLEx and 1.04% with SmILE. With a cap-based procedure, both anterior cap and stromal bed carry the intraocular pressure, while in a flap-based procedure, only the stromal bed does.

Conclusions

Compared to flap-based procedures like FLEx, the cap-based technique SmILE can be considered superior in terms of biomechanical stability, when measured experimentally in ex vivo porcine corneas.

Small Incision Lenticule Extraction (SMILE) for Hyperopia: Optical Zone Centration

PURPOSE

To evaluate optical zone centration of hyperopic small incision lenticule extraction (SMILE).

METHODS

This prospective study of 60 consecutive hyperopic SMILE procedures used the VisuMax femtosecond laser and matched LASIK procedures with the VisuMax and MEL 80 excimer lasers (Carl Zeiss Meditec AG, Jena, Germany). Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D) and astigmatism up to 6.00 D. For SMILE, the optical zone was between 6.3 and 6.7 mm, with a 2-mm transition zone. Two LASIK control groups (6.5- and 7-mm optical zone) were generated matched for spherical equivalent treated. In SMILE, the corneal vertex of the coaxially fixating eye was aligned with the vertex of the curved contact glass. In LASIK, the treatment was centered on the coaxially sighted corneal light reflex (first Purkinje image) with the contralateral eye (Seiler method). A tangential (instantaneous) curvature preoperative to 3 months postoperative difference map was generated for each eye. A fixed grid and set of concentric circles were superimposed on the difference map to measure the offset between the optical zone center and corneal vertex (0,0), and vector analysis was used for comparative analysis.

RESULTS

Mean attempted spherical equivalent was +5.61 ± 0.96 D (range: +3.20 to +6.50 D) and mean cylinder was -0.96 ± 0.62 D (range: 0.00 to -2.75 D) in the SMILE group. Mean age was 29 ± 7 years (range: 19 to 52 years) in the SMILE group. Mean centration offset was 0.23 ± 0.15 mm (range: 0 to 0.61 mm) for the SMILE group, 0.33 ± 0.14 mm (range: 0.14 to 0.85 mm) for the 6.5-mm LASIK group, and 0.31 ± 0.19 mm (range: 0.05 to 0.85 mm) for the 7-mm LASIK group. The mean centration offset for SMILE was less than that of both LASIK groups (P < .05).

CONCLUSIONS

Optical zone centration of hyperopic SMILE was found to be similar to eye-tracker-centered hyperopic LASIK with the MEL 80 laser. [J Refract Surg. 2017;33(3):150-156.].