Corneal remodeling after SMILE for moderate and high myopia: short-term assessment of spatial changes in corneal volume and thickness.

PURPOSE: To evaluate the early corneal remodeling and its influencing factors after Small incision lenticule extraction (SMILE) for moderate and high myopia. METHODS: This was a retrospective study. Pre- and post-operative (1 week and 1, 3, 6 months) corneal volume (CV), mean keratometry (Km), and corneal thickness (CT) were measured by Scheimpflug tomography. CT at the central, thinnest point, and on concentric circles of 2, 4, and 6 mm diameter was recorded to assess corneal thickness spatial profile (CTSP) and percentage of thickness increase (PTI) in the moderate and high myopia groups, and to explore possible influencing factors. RESULTS: After SMILE, the peripheral CT decreased in the moderate myopia group and central corneal thickness (CCT) increased in the high myopia group at 1 month compared to 1 week (all P < 0.05). The CV, Km and CT were significantly increased at 3 months compared to 1 month (all P < 0.05), but there was no significant change at 6 months compared to 3 months for both groups (all P > 0.05). Patients with high myopia showed greater corneal thickness changes (△CT) and higher PTI than moderate myopia (all P < 0.05). Regression analysis revealed that in addition to refraction, peripheral PTI was negatively correlated with CCT in the moderate myopia group (4 mm: ß = -0.023, P = 0.001; 6 mm: ß = -0.050, P < 0.001), as well as in the high myopia group (4 mm: ß = -0.038, P < 0.001; 6 mm: ß = -0.094, P < 0.001). Moreover, peripheral PTI in the moderate myopia group was negatively correlated with age (4 mm: ß = -0.071, P = 0.003; 6 mm: ß = -0.162, P < 0.001). CONCLUSIONS: After SMILE, the CV, Km, and CTSP showed dynamic changes in the early stage, which stabilized after 3 months. Compared to the moderate myopia group, the high myopia group experienced slower corneal stabilization. The change in PTI at 6 months after SMILE may be related to higher preoperative refraction, thinner CCT and younger age.

Collagen XIV Is an Intrinsic Regulator of Corneal Stromal Structure and Function.

Collagen XIV is poorly characterized in the body, and the current knowledge of its function in the cornea is limited. The aim of the current study was to elucidate the role(s) of collagen XIV in regulating corneal stromal structure and function. Analysis of collagen XIV expression, temporal and spatial, was performed at different postnatal days (Ps) in wild-type C57BL/6 mouse corneal stromas and after injury. Conventional collagen XIV null mice were used to inquire the roles that collagen XIV plays in fibrillogenesis, fibril packing, and tissue mechanics. Fibril assembly and packing as well as stromal organization were evaluated using transmission electron microscopy and second harmonic generation microscopy. Atomic force microscopy was used to assess stromal stiffness. Col14a1 mRNA expression was present at P4 to P10 and decreased at P30. No immunoreactivity was noted at P150. Abnormal collagen fibril assembly with a shift toward larger-diameter fibrils and increased interfibrillar spacing in the absence of collagen XIV was found. Second harmonic generation microscopy showed impaired fibrillogenesis in the collagen XIV null stroma. Mechanical testing suggested that collagen XIV confers stiffness to stromal tissue. Expression of collagen XIV is up-regulated following injury. This study indicates that collagen XIV plays a regulatory role in corneal development and in the function of the adult cornea. The expression of collagen XIV is recapitulated during wound healing.

Multimodal ocular imaging of known and novel corneal stromal disorders in dogs.

BACKGROUND: Imaging features obtained with Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM) for corneal stromal disorders have been sparsely reported in dogs. This case report is a compilation of imaging features for three cases of different stromal disorders of the canine cornea which have not yet been reported elsewhere. CASE PRESENTATION: Lipid deposition in case 1 appeared as needle-shaped hyperreflective lines along the collagen lamellae, which correlated histologically with lipid clefts. In case 2, glycosaminoglycan accumulation by mucopolysaccharidosis type 1 caused diffuse stromal hyperreflectivity and depletion of keratocytes on IVCM and was associated with secondary corneal degeneration presumed to be calcium deposition. In case 3, posterior corneal stromal opacities in the absence of ocular inflammation were identified. Hyperreflective particles were scattered in the middle and posterior corneal stroma on FD-OCT. With IVCM, hyperreflective deposits were identified within keratocytes and the number of enlarged keratocytes containing hyperreflective deposits increased towards the posterior stroma. The bilateral, non-inflammatory nature and unique appearance with IVCM is most consistent with a posterior stromal dystrophy reminiscent of pre-Descemet corneal dystrophy described in humans. CONCLUSIONS: In vivo multimodal corneal imaging facilitated instantaneous microstructural analysis and may be valuable in the differential diagnosis of corneal stromal disorders in veterinary clinical practice. The non-specific nature of imaging findings occurs in some conditions such as mucopolysaccharidosis, thus in vivo corneal imaging should be complemented with other gold standard methods of definitive diagnosis.

[Long-term clinical and functional outcomes of high myopia correction by femtosecond laser-assisted implantation of an intrastromal ring]. / Otdalennye kliniko-funktsional'nye rezul'taty korrektsii miopii vysokoi stepeni metodom intrastromal'noi implantatsii kol'tsa s femtolazernym soprovozhdeniem.

OBJECTIVE: To analyze remote clinical and functional outcomes of correcting high myopia in patients with thin cornea by the method of femtosecond laser-assisted implantation of intracorneal implant MyoRing. MATERIAL AND METHODS: The study included 22 patients (22 eyes; the mean age of study patients was 30.2±5.37 years). Mean spherical equivalent (SE) of refraction was -11.52±1.96 D, cylindrical component (cyl) of refraction was -2.04±1.64 D, minimal pachymetry index in the center was 491.6±20 µm, corneal hysteresis (CH) amounted to 8.6±1.19 mm Hg. The average pupil diameter in mesopic conditions was 5.6±0.23 mm. All patients had a history of mild amblyopia. The follow-up period lasted 2 years. RESULTS: Two years after the surgery uncorrected visual acuity was 0.6±1.22, corrected visual acuity 0.7±0.20. Mean spherical equivalent (SE) of refraction was 0.61±1.43 D, cylindrical component of refraction was -0.13±0.5 D. Predictability of SE within ±0.5 D was recorded in 84% of cases, ±1.0 - also in 84% of cases. Index of safety was 1.16, index of efficacy - 1.0. CH was 9.5±0.03 mm Hg. Mean pachymetry at the center did not change statistically significantly after the surgery in comparison to the initial data (p=1.00). CONCLUSION: MyoRing implantation is an effective and safe method, which ensures correction of the spherical component of refraction, as well as correction of astigmatism, improvement of biomechanical properties of the cornea, and an increase in corneal hysteresis (p=0.01).

A new collagen scaffold for the improvement of corneal biomechanical properties in a rabbit model.

Although collagen based materials are widely used in corneal tissue engineering with promising results. The usage of such materials for the improvement of corneal biomechanical properties is still unclear. In this study, we aimed to investigate a new Viscoll collagen-based membrane for the improvement of corneal biomechanical characteristics.The right eyes of 15 Chinchilla rabbits were implanted with the membrane via an intrastromal pocket, with the contralateral intact eyes as controls. At 7, 30, 90, and 180 days post-surgery, the rabbits underwent anterior segment optical coherence topography, clinical examination, and slit-lamp microscopy. Additionally, the corneal samples also underwent histological examination followed by the assessment of the biomechanical characteristics of four treated and non-treated corneas at 30, 90, and 180 days, including keratometry at 180 days, post operation. Data are presented as means ± confidence intervals with a 95% confidence level. All the operated corneas retained their transparency throughout the study. Implantation approximately doubled the central corneal thickness. Corneas became stronger by approximately 87% between 1 and 6 months after surgery (maximum fracture load, 13.3 ± 0.8 and 24.9 ± 1.4 N, respectively), and their elasticity increased by approximately 27% over the same time frame (maximum slope of the elastic region of the stress-strain curve, 11.5 ± 0.2 and 14.6 ± 1.4 N/mm respectively). We have thus proposed a new method to increase corneal thickness and strengthen the corneal tissues while preserving their transparency and demonstrated its safety and efficacy in a rabbit model over 6 months. This may be a suitable alternative to the existing corneal collagen crosslinking procedure.

Case Report: Double Intrastromal Corneal Ring Segment and Posterior Chamber Phakic Intraocular Lens Implantation.

SIGNIFICANCE: Keratoconus can manifest asymmetrically, affecting binocularity and becoming a refractive problem that is sometimes complex to solve. We propose a therapeutic approach for correction of keratoconus based on parallel implantation of a second intrastromal corneal ring segment (ICRS). PURPOSE: This study aimed to improve the refractive status of a patient affected with advanced bilateral keratoconus using implantation of a second ICRS and a phakic intraocular lens. CASE REPORT: A 44-year-old man came to our clinic requesting a refractive solution for his visual impairment. He had been diagnosed with bilateral severe keratoconus categorized by the Amsler-Krumeich classification scale as grade III (right eye) and grade II (left eye). He had previously undergone corneal cross-linking and implantation of ICRS (Intacs) in both eyes. Significant anisometropia was present between the eyes, and the patient also complained of poor quality of vision. We decided to implant a posterior chamber phakic collamer lens in his right eye and to insert a new ICRS (Keraring) deep and parallel to the previous one in his left eye. We aimed to prevent anisometropia in his right eye and to further regularize the affected cornea in his left eye. Refractive symmetry was achieved, and vision was optimized after surgery. CONCLUSIONS: In a patient with keratoconus, refractive surgery should be performed from a bilateral perspective. Specific cases of keratoconus can be managed by parallel implantation of a second ICRS.

Effect of Laser-assisted Subepithelial Keratectomy with Mitomycin C on Corneal Optical Density Measured with Confocal Microscopy.

SIGNIFICANCE: The development of confocal microscopy allows one to obtain high-resolution corneal images like its optical density. Some studies have evaluated the optical density with Scheimpflug cameras in the early post-operative period after photorefractive keratectomy, but no studies have evaluated the long-term evolution of optical density after surface ablation when mitomycin C is used. PURPOSE: This work aimed to study the changes in corneal optical density measured with confocal microscopy in eyes treated with laser-assisted subepithelial keratectomy (LASEK) and intraoperative mitomycin C (MMC) to correct myopia. METHODS: A study of 24 consecutive myopic eyes that underwent LASEK with 0.02% MMC and a control group of 24 healthy nontreated eyes was performed. Optical density was measured using the images by the confocal microscopy of the Heidelberg Retina Tomograph II with the Rostock Cornea Module. An analysis of confocal microscopy images was performed using the ImageJ software to obtain the optical density, in gray-scale units (GSU). The optical density of the stromal bed was evaluated 3 months, 15 months, and 3 years after surgery and was compared with the optical density at the equivalent depth of the stroma in controls. RESULTS: The mean values of optical density for the LASEK group were 81.7 ± 9.7, 78.6 ± 11.7, and 73.6 ± 18.7 GSU at 3 months, 15 months, and 3 years, respectively, and it was 61.8 ± 8.2 GSU for the control group. A statistically higher optical density 3 and 15 months after LASEK with MMC was found compared with controls (P < .001). No significant difference was found in optical density at 3 years post-operatively. CONCLUSIONS: Our study suggests that, after LASEK with MMC, the anterior corneal stroma has a higher optical density at 3 and 15 months post-operatively, which gradually returns to normal values 3 years after surgery.

Two-year observation of morphologic and histopathologic changes in the monkey cornea following small incision allogenic lenticule implantation.

PURPOSE: To observe the morphologic and histopathologic changes of femtosecond laser assisted small incision allogenic intrastromal lenticule implantation (AILI) in monkey corneas. METHODS: 6 healthy adult monkeys were included. One eye of two monkeys and both eyes of one monkey received femtosecond lenticule extraction with a -4.0 diopter (D) correction. Each extracted refractive donor lenticule was immediately allogeneically transplanted into a corneal stromal pocket created by a femtosecond laser in another monkey's eye. A postoperative two-year follow-up was performed with slit lamp microscopy, corneal topography, anterior segment optical coherence tomography and in vivo confocal microscopy. All eyes were enucleated for Hematoxylin-Eosin staining and transmission electron microscopy (TEM) observation. RESULTS: No complications were observed in the follow-up period. At postoperative 2 years, the corneas remained clear and the lenticules were integrated with the surrounding tissue under slit lamp microscopy. Nerve fiber regeneration was detected in the lenticule layer as observed through confocal microscopy. Corneal power was increased by 1.83 ± 1.36 D after 2 years, which was less than at 6 months (3.27 ± 1.2 D). Disordered fibers and decreased keratocytes in the implanted lenticules could be detected under light microscopy and TEM, with a clear boundary between the lenticules and the surrounding tissue. CONCLUSIONS: Small incision AILI is feasible and safe for reshaping the cornea. Corneal healing remained stable while refraction showed a moderate regression within postoperative 2 years.

Investigation of predictability and influence factors of the achieved lenticule thickness in small incision lenticule extraction.

BACKGROUND: To evaluate the differences between the predicted and achieved lenticule thickness (ΔLT) after small incision lenticule extraction (SMILE) surgery and investigate relationships between ΔLT and predicted lenticule thickness in SMILE. METHODS: A total of 184 eyes from 184 consecutive patients who underwent SMILE were included in this prospective study. One eye for each patient was randomly selected and included for statistical analysis. To achieve emmetropia, nomogram adds 10% correction of spherical refractive. An ultrasound pachymetry measurement and Scheimpflug camera corneal topography were obtained before and at 3 months after SMILE. The achieved lenticule thickness was calculated by comparing the preoperative examinations with postoperative examinations using ultrasound pachymetry and Pentacam software measurements. The pupil center and corneal vertex were selected as the 2 locations for measurement calculation on Pentacam. Analysis of variance (ANOVA) was performed to compare mean pachymetry values using different instruments. Linear regression analyses were performed between the VisuMax readout lenticule thicknesses and the measured maximum corneal change, between ΔLT and predicted lenticule thickness. RESULTS: On average, the achieved lenticule thickness measured with ultrasound pachymetry was 13.02 ± 8.87 µm thinner than the predicted lenticule thickness. The proportion of ΔLT in predicted values is 11.9% (ultrasound) and about 15% (Pentacam). Linear regression analysis showed significant relationships between the predicted and each achieved lenticule thickness. Each ΔLT was significantly related to predicted lenticule thickness (ultrasound: R2 = 0.242; pupil center from Pentacam: R2 = 0.230). CONCLUSIONS: An overestimation of achieved lenticule thickness was evident in this study which may exclude eligible SMILE patient. Also, our results showed that 10% increase of spherical refractive correction in the nomogram is appropriate. Furthermore, clinicians should subtract 10% of the predicted lenticule thickness to calculate the residual corneal stroma bed thickness.

Anterior segment optical coherence tomography imaging in peripheral ulcerative keratitis, a corneal structural description.

BACKGROUND: Anterior segment optical coherence tomography (AS OCT) is a helpful tool used to diagnose and manage many corneal conditions, but its use has not been reported in case of peripheral ulcerative keratitis (PUK). The aim of this study is to describe AS OCT findings in cases of PUK. METHODS: Retrospective observational case series of six eyes presenting with a PUK and proven systemic vasculitis. Clinical course, slit lamp photographs, and AS OCT findings were the main outcomes. RESULTS: The AS OCT findings were found to correlate with the ocular disease's level of activity. In the acute stage, an absence of corneal epithelium, a scrambled appearance of the anterior stroma and a heterogeneous stromal reflectivity were observed. During the reduction of disease level activity, an irregular hyporeflective epithelium, a smoother anterior stroma, and a homogenous hyperreflective stroma were seen. At the healed stage, a filling of the corneal defect by a hyporeflective thick epithelium, the persistence of the hyperreflective underlying stroma, and a demarcation line were observed. The mean total corneal thickness at last follow-up was significantly thicker (509 ± 147 µm) compared with the mean corneal thickness at onset (408 ± 131 µm; P = 0.03). CONCLUSIONS: AS OCT provides an assessment of structural changes occurring in PUK, useful for its diagnosis and monitoring.

Corneal tissue properties following scleral lens wear using Scheimpflug imaging.

PURPOSE: To investigate the effect of short-term scleral lens wear on the corneal stroma at a macroscopic (thickness) and microscopic (within tissue) level, including regional variations. METHODS: Fourteen young, healthy participants wore a rotationally symmetric, 16.5 mm diameter, scleral lens for 8 h. Scheimpflug images were captured before, and immediately after, lens wear, and also on a second day (without lens wear) to quantify natural corneal diurnal variations. After corneal segmentation, pixel intensities of the stromal tissue were statistically modelled using a Weibull probability density function from which parameters α and ß were derived. RESULTS: Both α and ß parameters increased significantly following scleral lens wear (by 5.7 ± 10% and 6.5 ± 6.5%, respectively, both p < 0.01). Corneal thickness also increased slightly following lens wear (mean increase 0.49 ± 1.77%, p = 0.01); however, the change in α and ß parameters did not correlate with the magnitude of corneal swelling. On the control day, small but significant corneal thinning was observed (-0.82 ± 1.1%, p = 0.03), while α and ß parameters remained stable. Both microparameters varied significantly across the cornea, with α decreasing (-15.4 ± 0.7%) and ß increasing towards the periphery (+4.4 ± 2.6%) (both p < 0.001). CONCLUSION: Corneal microparameters α and ß varied regionally across the cornea and displayed a statistically significant increase following short-term scleral lens wear, but remained stable between morning and evening measurements taken during a control day without lens wear. These corneal microparameters may be a useful metric to quantify subclinical corneal changes associated with low level hypoxia.

Ocular phenotypic consequences of a single copy deletion of the Yap1 gene (Yap1 +/-) in mice.

Purpose: To identify the effects of a single copy deletion of Yap1 (Yap1 +/-) in the mouse eye, the ocular phenotypic consequences of Yap1 +/- were determined in detail. Methods: Complete ophthalmic examinations, as well as corneal esthesiometry, the phenol red thread test, intraocular pressure, and Fourier-domain optical coherence tomography were performed on Yap1 +/- and age-matched wild-type (WT) mice between eyelid opening (2 weeks after birth) and adulthood (2 months and 1 year after birth). Following euthanasia, enucleated eyes were characterized histologically. Results: Microphthalmia with small palpebral fissures, corneal fibrosis, and reduced corneal sensation were common findings in the Yap1 +/- mice. Generalized corneal fibrosis precluded clinical examination of the posterior structures. Histologically, thinning and keratinization of the corneal epithelium were observed in the Yap1 +/- mice in comparison with the WT mice. Distorted collagen fiber arrangement and hypercellularity of keratocytes were observed in the stroma. Descemet's membrane was extremely thin and lacked an endothelial layer in the Yap1 +/- mice. The iris was adherent to the posterior cornea along most of its surface creating a distorted contour. Most of the Yap1 +/- eyes were microphakic with swollen fibers and bladder cells. The retinas of the Yap1 +/- mice were normal at 2 weeks and 2 months of age, but the presence of retinal abnormalities, including retinoschisis and detachment, was markedly increased in the Yap1 +/- mice at 1 year of age. Conclusions: The results show that the heterozygous deletion of the Yap1 gene in mice leads to complex ocular abnormalities, including microphthalmia, corneal fibrosis, anterior segment dysgenesis, and cataract.

Endogenous fluorescence can differentiate the keratoconic cornea.

The purpose of the study was to investigate the endogenous fluorescence of the keratoconic cornea in order to analyze changes in the spectra due to the keratoconic stroma abnormalities. Twenty-two corneal buttons obtained from patients with keratoconus (KC, N = 22) at the time of penetrating keratoplasty were used. As a reference, twelve normal corneas (N = 12): ten from the Eye Bank and two from enucleated eyes due to choroidal melanoma were used. The fluorescence excitation/emission matrices (EEM) in the ranges of 250-400/260-600 nm were recorded. Healthy cornea, keratoconic cornea and sclera showed three main EEM bands, which correspond to the following fluorophores: tryptophan residues in the proteoglycan fraction of corneal/scleral stromas, naturally occurring collagen cross-links and the NAD(P)H fraction present in the metabolically active cells. Relative intensity factors S1, S2 and S3 describing the contribution of each kind of fluorophore to the total fluorescence of the tissue were calculated. Normal and keratoconic corneas show qualitatively similar fluorescence matrices, but the statistically significant differences in the mean values of the S1, S2 and S3 parameters for the KC and normal corneas were observed indicating changes in contribution of different fluorophores to the whole fluorescence of the tissue. Moreover, differences between multidimensional distribution of the relative intensity factors S1, S2 and S3 between these groups were demonstrated (p < 0.001). In conclusions: Differences in the relative intensity factors calculated on a basis of the fluorescence spectra can correspond to the changes found in the KC stroma regarding natural collagen cross-links and the proteoglycan fraction. These parameters well differentiate the KC and normal corneas that could serve as an additional tool for the keratoconus characterization.

Intravital multiphoton microscopic imaging platform for ocular surface imaging.

The purpose of this study is to provide an intravital noninvasive multiphoton microscopic platform for long-term ocular imaging in transgenic fluorescent mice with subcellular resolution. A multiphoton microscopic system with tunable laser output was employed. We designed a mouse holder incorporated with stereotaxic motorized stage for in vivo three-dimensional imaging of ocular surface in 3 transgenic mouse line with fluorescent protein (FP) expression to visualize distinct structures. With our imaging platform and the expression of FPs, we obtained the three-dimensional images across the whole cornea from epithelium to endothelium and in conjunctiva with subcellular resolution in vivo. Specified EGFP expression in corneal epithelium of K5-H2B-EGFP mice helped to identify both corneal and limbal epithelial cells while ubiquitous nuclear FP expression in R26R-GR mice allowed us to visualized nuclei of all cell types. Universal membrane-localized FP in mT/mG mice outlined all cell boundaries, nerve fibers, and capillaries. The simultaneously collected second harmonic generation signals from collagenous stroma provided architectural contrast. Time-lapsed recording enabled monitoring the mitotic activity of corneal epithelial cells and limbal epithelial cells. We developed an intravital multiphoton microscopic stereotaxic imaging platform and showed that, by incorporating FP-expressing transgenic mice, this platform enables in vivo 4-dimensional ophthalmic study at subcellular resolution.

Evaluation of disk halo size after small incision lenticule extraction (SMILE).

PURPOSE: To investigate changes in objective disk halo size produced by a glare source after small incision lenticule extraction (SMILE) for myopia correction. METHODS: This prospective clinical study included 45 right eyes of 45 patients with a mean age of 25.40 ± 5.06 years and mean spherical equivalent (SE) of - 6.08 ± 1.90 diopters. Disk halo size was measured with a vision monitor before surgery and at postoperative 1 week and 3 months. Other information was collected, including age, SE, lenticule thickness, lenticule diameter, dark pupil, and pupillary response to light parameters (initial diameter; amplitude, latency, duration, and velocity of contraction; latency, duration, and velocity of dilation; and maximum, minimum, and average pupil size). RESULTS: Compared to preoperative values, disk halo size increased significantly at postoperative 1 week (P = 0.026) and returned to baseline at postoperative 3 months (P = 0.349). Preoperative disk halo size significantly correlated with SE (r = - 0.346, P = 0.020), minimum pupil size (r = 0.365, P = 0.014), and average pupil size (r = 0.310, P = 0.038). Disk halo size at postoperative 1 week was significantly correlated with age (r = 0.324, P = 0.030) and minimum pupil size (r = 0.297, P = 0.047). Disk halo size at postoperative 3 months was significantly correlated with lenticule diameter (r = - 0.362, P = 0.015), initial diameter (r = 0.311, P = 0.037), maximum pupil size (r = 0.312, P = 0.037), minimum pupil size (r = 0.440, P = 0.002), and average pupil size (r = 0.373, P = 0.012). CONCLUSIONS: After SMILE, disk halo size demonstrated a temporary increase and then returned to baseline.

Deep blue dot corneal degeneration: confocal characteristics.

PURPOSE: To discuss the clinical features, differential diagnosis and the novel confocal microscopic findings noted in the rare 'deep blue dot corneal degeneration'. METHODS: Observational case report. RESULTS: Slit-lamp biomicroscopic examination revealed bilateral, numerous, circular to oval discrete blue opacities at the level of deep stroma and fine grey linear opacities at the level of mid to deep stroma. Confocal microscopy demonstrated two types of corresponding hyper-reflective extracellular lesions: oval deposit-like, most concentrated at a depth of 430-480 µ and needle-like at the depth 330-370 µ. CONCLUSIONS: Deep blue dot corneal degeneration is a rare entity where blue deposits of amyloid are seen in the deep corneal stroma. It should be considered as a differential diagnosis when an old-aged person presents with good vision and the above mentioned findings.

Small-incision lenticule addition in ex vivo model of ectatic human corneas.

PURPOSE: To investigate the feasibility of intrastromal lenticule insertion to restore corneal shape in a model of ectatic human cornea. METHODS: For this experimental ex vivo study on 34 human corneas unsuitable for transplantation, 17 corneas were thinned by decentralized posterior excimer laser ablation to 200 µm thickness and 6.5 mm diameter and then inflated up to 100 mm Hg to expose the ectasias (recipient corneas). Pachimetry and topography were obtained. Stromal lenticules of the same diameter and thickness as the ectasias were shaped with a femtosecond laser from the remaining 17 donor corneas. An intrastromal pocket was created with femtosecond laser within the ectatic recipient corneas and the donor lenticule was inserted inside it. Changes in corneal architecture and profile were evaluated by means of corneal topography and anterior segment optical coherence tomography. RESULTS: All stromal lenticules were successfully implanted. Tomography confirmed regularity of the lenticule profile within the stromal pocket. Corneal thickness was significantly increased after the procedure (P < 0.0001). Maximal posterior elevation from the best-fitted toric ellipsoid was significantly reduced (P < 0.0001). Significant flattening of posterior K1 and K2 was also obtained (P = 0.041 and P = 0.004, respectively). Anterior and posterior astigmatism, anterior and posterior asphericity, and spherical aberration did not differ significantly after the procedure. CONCLUSIONS: Femtosecond laser-assisted stromal lenticule addition is feasible for restoring corneal thickness to an ectatic area and for regularizing posterior corneal elevation. The technique opens new perspectives for the treatment of corneal ectasias.

Corneal remodeling and spatial profiles following small incision lenticule extraction.

PURPOSE: To evaluate the three-dimensional corneal spatial profiles following small incision lenticule extraction (SMILE) based on corneal asphericity, thickness, and volume. MATERIALS AND METHODS: Eighty-three eyes in 83 patients who underwent SMILE were examined before and 1 and 6 months after surgery. The asphericity of the anterior and posterior corneal surfaces was analyzed. Corneal volume (CV) was measured in corneal regions measuring 3.0 mm, 5.0 mm, and 7.0 mm in diameter. Mean corneal thickness (CT) values were acquired at the apex (0.0 mm) and in four concentric radial zones from the apex (with diameters of 2.0, 4.0, 6.0, and 8.0 mm). RESULTS: The mean anterior Q value increased from - 0.32 preoperatively to 0.67 at 1 month and 0.62 at 6 months postoperatively. The mean posterior Q value decreased from - 0.30 preoperatively to - 0.26 at 1 month and to - 0.25 at 6 months postoperatively. The CV increased by 0.05 ± 0.06 mm3 (1.40%), 0.06 ± 0.11 mm3 (0.83%), and 0.09 ± 0.17 mm3 (0.73%) along the radial zones with respective diameters of 3.0 mm, 5.0 mm, and 7.0 mm. The CT increased by 6.02 ± 6.48 µm (1.36%) at the apex and then decreased with increasing distance from the center, i.e., to 5.52 ± 6.31 µm (1.20%) at 2.0 mm, 4.72 ± 6.55 µm (0.92%) at 4.0 mm, 4.47 ± 7.86 µm (0.75%) at 6.0 mm, and 4.86 ± 10.31 µm (0.70%) at 8.0 mm. No correlations were observed between changes in CV and CT and refractive fluctuation between 1 month and 6 months postoperatively. CONCLUSIONS: The corneal profile displayed a less oblate shift on the anterior surface; however, the posterior surface showed a slight backward shift during the postoperative period. The CV and CT steadily increased after surgery and mainly within the operative zones. Refraction remained stable postoperatively and was not affected by the corneal remodeling.

Epithelial map-guided anterior stromal micropuncture for the treatment of recurrent corneal erosion syndrome.

PURPOSE: To introduce the use of corneal epithelial mapping by anterior segment optical coherence tomography (AS-OCT) as an ancillary testing for the identification of areas of loose epithelial adherence in recurrent corneal erosion syndrome (RCES), and the subsequent treatment of the latter with anterior stromal puncture (ASP). METHODS: Five patients were presented with RCES following traumatic corneal abrasions. Following resolution of acute episodes, AS-OCT epithelial mapping was performed revealing in all patients an area of increased epithelial thickness (hot spot) corresponding to the site of loose attachment of the epithelium to the epithelial basement membrane. ASP to the area of epithelial thickening, as delineated by the epithelial map, was performed. RESULTS: To date, none of the patients has shown any signs of disease recurrence over a period ranging from 6 to 20 months following the application of epithelial map-guided ASP. CONCLUSIONS: AS-OCT epithelial mapping can reveal the exact area of loose epithelial adherence in RCES. Hence, epithelial mapping can delineate the target area for treatment with ASP and may decrease the high failure rates of ASP.

Morphological analysis of corneal findings modifications after death: A preliminary OCT study on an animal model.

The aim of this work was to describe, for the first time, the morphological modifications, in a three-dimensional mode, of the central cornea at different intervals since death. The study design involved the analysis of 30 eyes (15 heads) of female, adult sheep (>2 years) sacrificed at a local slaughterhouse. The eyes, after animal decapitation, were examined in situ, without enucleation. Ocular globes were stored at well-known temperature (within a range of 12-22 °C) and humidity (within a range of 50-60%). The instrumental analysis was executed using a portable spectral-domain OCT (SD-OCT) system (iVue SD-OCT, Optovue Inc, Fremont, CA) calibrated to the corneal mode. OCT imaging was performed at different time-points since death. Pachymetric map, morphological and ultrastructural analysis (epithelium, stroma, and endothelium), were performed for each time-point. After an initial thinning of tissues and an enhancement of epithelial reflectivity, stromal thickness increased from the 2nd up to the 6th hour. Subsequently, a new trend incorneal thinning was observed in association with the appearance ofone or more demarcation lines between the anterior andposterior stroma. After the 12th hour, a recurrence of corneal swelling was detected in association with thedelamination of stromal tissue. Since the 24th hour, the epithelium disappeared in 50% of cases and the anterior chamberdepth progressively decreased. At the 48th hour, various ocular structures showed the onset of putrefaction processes, such as theappearance of hyper-reflective dots in anterior chamber, iridocorneal contact, and the massive vacuolization of theposterior stroma until the total delamination. The portable OCT system is a useful approach for in situ postmortem corneal examination, and it may be potentially applied for the selection of donor cornea in transplantology and for the determination of post-mortem intervals in forensic medicine.