Stromal Rejection After SMILE for the Correction of Astigmatism After Graft

PURPOSE

To describe a case of stromal rejection in a 46-year-old man after small incision lenticule extraction (SMILE) for the correction of residual astigmatism following deep anterior lamellar keratoplasty (DALK).

METHODS

Case report.

RESULTS

Nine years after an uneventful DALK in the left eye, the patient (uncorrected distance visual acuity [UDVA] = 20/200, corrected distance visual acuity [CDVA] = 20/32, and refraction = -3.25 -4.25 × 165°) underwent SMILE using the VisuMax femtosecond laser platform (Carl Zeiss Meditec, Jena, Germany). The next day, the UDVA, CDVA, and refraction were 20/40, 20/32, and -1.25 -0.50 × 15°, respectively. One week later, the patient presented complaining of pain, photophobia, and blurred vision; at this time, there was a reduction in UDVA to 20/400 and CDVA to 20/63. With a diagnosis of stromal rejection, the patient was treated with corticosteroids (sub-Tenon injection and oral). Five months later, UDVA was 20/40, CDVA was 20/25, and refraction was -1.25 -0.75 × 90°. The graft had completely cleared.

CONCLUSIONS

SMILE can be an effective alternative for the correction of astigmatism after DALK, but the risks of inflammatory responses and graft rejection call for caution. [J Refract Surg. 2019;35(11):737-739.].

Dry Eyes After SMILE

Dry eyes is one of the most common complications after laser vision correction. Small incision lenticule extraction (SMILE) is a flapless procedure with a smaller corneal incision, less corneal nerves are transected during, making it theoretically less prone to dry eyes. Both SMILE and femtosecond-laser-assisted in situ keratomileusis (FS-LASIK) induce a transient worsening in dry eye parameters, but there is evidence showing that SMILE holds promises to have fewer negative impacts on the ocular surface parameters and allow an earlier recovery. SMILE-treated eyes may also have shown less corneal denervation and better corneal sensitivity compared with FS-LASIK eyes. This review summarizes the mechanisms of dry eyes after laser vision correction, the short-term (≤6 months) and long-term (>6 months) results in changes to dry eyes signs and symptoms, and corneal sensitivity of SMILE, as compared with FS-LASIK. Limitation of the studies and reasons accounting for their discrepancies will be discussed. Future randomized controlled trials with standardized postoperative regime are needed for better evaluation of dry eyes after SMILE.

Astigmatism Correction Using SMILE

Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.

Enhancement Options After Myopic Small-Incision Lenticule Extraction (SMILE): A Review

PURPOSE

To provide an overview of the currently available retreatment methods after myopic small-incision lenticule extraction (SMILE).

DESIGN

Systematic literature review.

METHODS

The PubMed library was searched for articles containing the terms "small-incision lenticule extraction" and "enhancement" or "retreatment". The last search was performed on May 1, 2019.

RESULTS

In contrast to laser in-situ keratomileusis (LASIK), which can be retreated by a flap relift, repeat SMILE retreatment is currently not approved and only seldomly performed. As substitutes, surface ablation, cap-to-flap conversion using the CIRCLE program in the VisuMax platform, and thin-flap LASIK have been recently established. While all options offer safety and efficacy comparable to LASIK retreatments, each has its patient-specific advantages and disadvantages. While surface ablation preserves the flap-free approach of the primary procedure, the aspect of pain and a slow visual recovery might render it less attractive as compared with CIRCLE and thin-flap LASIK which offer quick recovery, however at the price of flap creation. Besides, each retreatment method generates specific tissue responses and has a different impact on corneal biomechanics, which is strongly dependent on the previous SMILE parameters, especially the cap thickness.

CONCLUSIONS

Refractive enhancement after SMILE is currently mostly performed by surface ablation, CIRCLE cap-to-flap conversion or thin-flap LASIK, which all offer safety and efficacy comparable to LASIK retreatments. In this review, a detailed overview over each method, its technical aspects, and specific advantages and disadvantages is given.

Substance P induces fibrotic changes through activation of the RhoA/ROCK pathway in an in vitro human corneal fibrosis model

Fibrosis is characterized by hardening, overgrowth, and development of scars in various tissues as a result of faulty reparative processes, diseases, or chronic inflammation. During the fibrotic process in the corneal stroma of the eye, the resident cells called keratocytes differentiate into myofibroblasts, specialized contractile fibroblastic cells that produce excessive amounts of disorganized extracellular matrix (ECM) and pro-fibrotic components such as alpha-smooth muscle actin (α-SMA) and fibronectin. This study aimed to elucidate the role of substance P (SP), a neuropeptide that has been shown to be involved in corneal wound healing, in ECM production and fibrotic markers expression in quiescent human keratocytes, and during the onset of fibrosis in corneal fibroblasts, in an in vitro human corneal fibrosis model. We report that SP induces keratocyte contraction and upregulates gene expression of collagens I, III, and V, and fibrotic markers: α-SMA and fibronectin, in keratocytes. Using our in vitro human corneal fibrosis model, we show that SP enhances gene expression and secretion of collagens I, III, and V, and lumican. Moreover, SP upregulates gene expression and secretion of α-SMA and fibronectin, and increases contractility of corneal fibroblasts during the onset of fibrosis. Activation of the preferred SP receptor, the neurokinin-1 receptor (NK-1R), is necessary for the SP-induced pro-fibrotic changes. In addition, SP induces the pro-fibrotic changes through activation of the RhoA/ROCK pathway. Taken together, we show that SP has a pro-fibrotic effect in both quiescent human keratocytes and during the onset of fibrosis in an in vitro human corneal fibrosis model.

Development of lacrimal gland inflammation in the mouse model of herpes stromal keratitis

Herpes stromal keratitis (HSK) is a chronic immunoinflammatory condition which develops in response to recurrent herpes simplex virus-1 (HSV-1) infection of the cornea. Patients with HSK often demonstrate the concurrence of corneal desiccation and the loss of blink reflex. However, the relationship between severity of HSK, level of basal tears and inflammation of the lacrimal gland is mostly unexplored. In this study, we compared these variables in extraorbital lacrimal gland (EoLG) after corneal HSV-1 infection in the C57BL/6J mouse model. Our results showed a significant reduction in the volume of tears in infected eyes during the development of HSK. Extensive architectural damage to EoLG, presumably caused by a massive influx of interferon-gamma secreting T cells, was observed during clinical disease period of HSK. A positive correlation between the decrease in tear volume, severity of HSK and the damage to EoLG were evident in infected mice. The presence of infectious virus measured in EoLG during pre-clinical, but not clinical disease period of HSK, suggested that viral cytopathic effects are not the major contributors of extensive damage seen in EoLG. Furthermore, topical administration of lacritin peptide delayed but did not prevent the decrease in tears in HSV-1 infected mice, and had no significant effect in either reducing the severity of HSK or T cell infiltration in EoLG of infected mice. Together, our results showed an interplay between the severity of HSK, inflammation of EoLG, and the reduced level of tears after corneal HSV-1 infection.

Dynamic changes of the extracellular matrix during corneal wound healing

The extracellular matrix (ECM) confers transparency to the cornea because of the precise organization of collagen fibrils and a wide variety of proteoglycans. We monitored the corneal wound healing process after alkali burns in rabbits. We analyzed the location and expression of collagens and proteoglycans, the clinical impact, and the recovery of optical transparency. After the animals received both general and ocular topical anesthesia, the central cornea of the left eye was burned by placing an 8-mm diameter filter paper soaked in 0.5 N NaOH for 60 s. The eyes were evaluated under a surgical microscope at 1, 3, and 6 months after burning. At each time point, the clinical conditions of the burned and control corneas were observed. The arrangement of collagen fibers in the corneal stroma was visualized by Picrosirius-red staining, Gomori's silver impregnation and transmission electronic microscopy. Corneal light transmittance was also measured. Myofibroblasts presence was analyzed by immunohistochemistry. mRNA expression levels of collagen types I and III, lumican, decorin, keratocan and alpha-smooth muscle actin were determined by quantitative real-time polymerase chain reaction. One month after alkali burn, the ECM was disorganized and filled with lacunae containing different types of cells and collagen type III fibers in the wound area. Corneal opacities were present with attendant loss of light transmittance. Collagen and proteoglycan mRNA expression levels were up-regulated. After three months, wound healing progress was indicated by reduced corneal opacity, increased light transmittance, reorganization of collagen fibers and only collagen type I expression levels were at control levels. After six months, the wound area ECM morphology was similar to controls, but transmittance values remained low, denoting incomplete restoration of the stromal architecture. This multidisciplinary study of the stromal wound healing process revealed changes in corneal transmittance, collagen organization, myofibroblasts presence and ECM composition at 1, 3, and 6 months after alkali burning. Documenting wound resolution during the six-month period provided reliable information that can be used to test new therapies.

Intraoperative optical pachymetry in photorefractive keratectomy

PURPOSE

To study the effect of variables on the accuracy and reliability of the optical pachymeter built into the WaveLight EX500 excimer laser during photorefractive keratectomy (PRK).

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, USA.

DESIGN

Retrospective case series.

METHODS

A chart review of 352 eyes (181 patients) that had excimer laser PRK was performed. Programmed excimer laser residual stromal bed (RSB) measurements, optical pachymeter measurements after ablation, and Scheimpflug pachymetry measurements (Pentacam) at the 1-year follow-up were compared. Variables included ablation time, preoperative spherical equivalent (SE), 1-year SE, mitomycin-C use, operating room temperature and humidity, and programmed monovision.

RESULTS

The mean programmed RSB was 27 μm greater than the optical pachymetry post-ablation measurement (P < .001). Of patients with a 1-year follow-up, the 1-year Scheimpflug pachymetry RSB was 24 μm greater than the optical pachymetry post-ablation RSB (P < .001). Comparison of the programmed RSB with the optical pachymetry post-ablation RSB showed that the preoperative SE and ablation time had a Pearson correlation coefficient of -0.36 and 0.30, respectively (P < .001). There was no correlation between operating room temperature, humidity, or programmed monovision with these differences.

CONCLUSIONS

The RSB post-ablation values measured by optical pachymetry during PRK were significantly lower than the programmed excimer laser RSB value and 1-year Scheimpflug pachymetry RSB value. Intraoperative pachymetry during PRK underpredicted the actual long-term RSB thickness. The greater temporary drying effect associated with increased ablation time in higher myopic corrections might have caused this error.

Descemet's Membrane Modulation of Posterior Corneal Fibrosis

Purpose

The purpose of this study was to evaluate the effect of removal of Descemet's basement membrane and endothelium compared with removal of the endothelium alone on posterior corneal fibrosis.

Methods

Twelve New Zealand White rabbits were included in the study. Six eyes had removal of the Descemet's membrane-endothelial complex over the central 8 mm of the cornea. Six eyes had endothelial removal with an olive-tipped cannula over the central 8 mm of the cornea. All corneas developed stromal edema. Corneas in both groups were cryofixed in optimum cutting temperature (OCT) formula at 1 month after surgery. Immunohistochemistry (IHC) was performed for α-smooth muscle actin (SMA), keratocan, CD45, nidogen-1, vimentin, and Ki-67, and a TUNEL assay was performed to detect apoptosis.

Results

Six of six corneas that had Descemet's membrane-endothelial removal developed posterior stromal fibrosis populated with SMA+ myofibroblasts, whereas zero of six corneas that had endothelial removal alone developed fibrosis or SMA+ myofibroblasts (P < 0.01). Myofibroblasts in the fibrotic zone of corneas that had Descemet's membrane-endothelial removal were undergoing both mitosis and apoptosis at 1 month after surgery. A zone between keratocan+ keratocytes and SMA+ myofibroblasts contained keratocan-SMA-vimentin+ cells that were likely CD45- corneal fibroblasts and CD45+ fibrocytes.

Conclusions

Descemet's basement membrane has an important role in modulating posterior corneal fibrosis after injury that is analogous to the role of the epithelial basement membrane in modulating anterior corneal fibrosis after injury. Fibrotic areas had myofibroblasts undergoing mitosis and apoptosis, indicating that fibrosis is in dynamic flux.

CIRCLE Software for the Management of Retained Lenticule Tissue Following Complicated SMILE Surgery

PURPOSE

To describe the therapeutic use of CIRCLE software (Carl Zeiss Meditec, Jena, Germany) for the management of retained lenticule tissue after complicated small incision lenticule extraction (SMILE).

METHODS

Two patients were referred for consultation and treatment due to intraoperative complications during SMILE. In case 1, a black patch during laser delivery caused the lenticule to be torn irregularly from the undersurface during extraction and a sliver of it was retained in the pocket. Case 2 presented with false plane dissection and a completely retained lenticule on anterior segment optical coherence tomography. Both cases were managed using the CIRCLE software by converting the cap into a flap, thus making access to the interface possible.

RESULTS

In case 1, after lifting the flap a small sliver of tissue was found in the interface, which was dissected, following which a 20-µm phototherapeutic keratectomy was done to smooth the interface. In case 2, after lifting the flap the edge of the retained lenticule was identified by using an endoilluminator and the lenticule was separated and subsequently removed. Both cases showed significant improvement in uncorrected distance visual acuity, corrected distance visual acuity, and Objective Scatter Index score on day 1 after repair surgery.

CONCLUSIONS

CIRCLE software may be successfully used for managing retained lenticule tissue apart from performing enhancement after SMILE. [J Refract Surg. 2019;35(1):60-65.].

Collagen fiber crimping following in vivo UVA-induced corneal crosslinking

The purpose of this study was to measure collagen fiber crimping (CFC) using nonlinear optical imaging of second harmonic generated (SHG) signals to determine the effects of UVA-riboflavin induced corneal collagen crosslinking (UVA CXL) on collagen structure. Two groups, four rabbits each, were treated in the right eye with standard UVA CXL. In vivo confocal microscopy was performed at 1, 2, and 4 weeks after treatment for the first group and up to three months for the second group to measure epithelial/stromal thickness and corneal haze during recovery. Rabbits were sacrificed at one and three months, respectively, and their corneas fixed under pressure. Regions of crosslinking were identified by the presence of collagen autofluorescence (CAF) and then collagen structure was imaged using SHG microscopy. The degree of CFC was determined by measuring the percentage difference between the length of the collagen fiber and the linear distance traveled. CFC was measured in the central anterior and posterior CXL region, the peripheral non-crosslinked region in the same cornea, and the central cornea of the non-crosslinked contralateral eye. No change in corneal thickness was detected after one month, however the stromal thickness surpassed its original baseline thickness at three months by 25.9 μm. Corneal haze peaked at one month and then began to clear. Increased CAF was detected in all CXL corneas, localized to the anterior stroma and extending to 42.4 ± 3.4% and 47.7 ± 7.6% of the corneal thickness at one and three months. There was a significant (P < 0.05) reduction in CFC in the CAF region in all eyes averaging 1.007 ± 0.006 and 1.009 ± 0.005 in one and three month samples compared to 1.017 ± 0.04 and 1.016 ± 0.06 for controls. These results indicate that there is a significant reduction in collagen crimping following UVA CXL of approximately 1%. One possible explanation for this loss of crimping could be shortening of the collagen fibers over the CXL region.

Thrombospondin-1 Is Necessary for the Development and Repair of Corneal Nerves

Thrombospondin-1-deficient (TSP-1^-/-) mice are used as an animal model of Sjögren's Syndrome because they exhibit many of the symptoms associated with the autoimmune type of dry eye found in primary Sjögren's Syndrome. This type of dry eye is linked to the inflammation of the lacrimal gland, conjunctiva, and cornea, and is thought to involve dysfunction of the complex neuronal reflex arc that mediates tear production in response to noxious stimuli on the ocular surface. This study characterizes the structural and functional changes to the corneal nerves that are the afferent arm of this arc in young and older TSP-1^-/- and wild type (WT) mice. The structure and subtype of nerves were characterized by immunohistochemistry, in vivo confocal microscopy, and confocal microscopy. Cytokine expression analysis was determined by Q-PCR and the number of monocytes was measured by immunohistochemistry. We found that only the pro-inflammatory cytokine MIP-2 increased in young corneas of TSP-1^-/- compared to WT mice, but tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2) all increased in older TSP-1^-/- mouse corneas. In contrast, CD11b+ pro-inflammatory monocytes did not increase even in older mouse corneas. Calcitonin gene-related peptide (CGRP)-, but not Substance P (SubP)-containing corneal nerves decreased in older, but not younger TSP-1^-/- compared to WT mouse corneas. We conclude that CGRP-containing corneal sensory nerves exhibit distinct structural deficiencies as disease progresses in TSP-1^-/- mice, suggesting that: (1) TSP-1 is needed for the development or repair of these nerves and (2) impaired afferent corneal nerve structure and hence function may contribute to ocular surface dysfunction that develops as TSP-1^-/- mice age.

Variation of Lenticule Thickness for SMILE in Low Myopia

PURPOSE

To report the impact of increasing minimum lenticule thickness on the safety and efficacy of small incision lenticule extraction (SMILE) in low myopia up to -3.50 diopters (D).

METHODS

SMILE was performed in 76 eyes of 76 patients. Thirty-eight eyes of 38 patients with low myopia were prospectively operated on with a programmed minimum lenticule thickness of 15 to 30 μm (thicker lenticule group). Thirty-five eyes suitable for analysis were then retrospectively matched by spherical equivalent to 35 eyes operated on with a minimum standard setting of 10 μm (standard thickness group), as provided in the database of the SMILE Eyes Clinic Linz, Linz, Austria. Comparison of outcomes was performed with the Standard Graphs for Reporting Refractive Surgery and by analysis of higher order aberrations as provided by Scheimpflug imaging.

RESULTS

Apart from lenticule thickness, there was no significant difference in preoperative baseline or treatment parameters between both groups. Mean minimum lenticule thickness differed significantly (standard thickness = 10 ± 0 μm; thicker lenticule = 20 ± 5 μm; P < .0001). This also translated into a significant difference in maximum lenticule thickness (standard thickness: 54 ± 11 μm; thicker lenticule: 62 ± 8 μm; P = .0002). Mean SEQ preoperatively was -2.25 ± 0.51 (standard thickness) and -2.24 ± 0.46 (thicker lenticule) D, respectively, and changed to -0.11 ± 0.50 (standard thickness) and +0.01 ± 0.36 (thicker lenticule) D postoperatively (P < .0001 for both comparisons). Uncorrected postoperative visual acuity was -0.08 ± 0.35 (standard thickness) versus -0.10 ± 0.09 (thicker lenticule) logMAR (P = .706). After SMILE, the thicker lenticule group showed better safety (1.20 vs 1.08; P = .025) and efficacy (1.14 vs 0.96; P = .011) indices, translating into more eyes within ±0.50 D from target (91% vs 77%) and with at least 0.0 logMAR visual acuity (97% vs 86%), and fewer eyes losing one (3% vs 17%) and two (0% vs 3%) lines.

CONCLUSIONS

Increasing minimum lenticule border thickness seems to improve the safety and efficacy of SMILE in low myopia. [J Refract Surg. 2018;34(7):453-459.].

Pediatric keratoconus: a review of the literature

PURPOSE

To describe the epidemiology and prevalence, rates of progression, difference between adult and pediatric populations, and therapeutic approaches to pediatric keratoconus from documented literature.

METHODS

A literature search was done on PubMed using key words including pediatric keratoconus, children with keratoconus, adult keratoconus, penetrating keratoplasty, corneal cross-linking and intracorneal ring segments. The literature was reviewed and reported to explore the key epidemiological differences between the pediatric and adult population with regards to presentation and treatment options.

RESULTS

Pediatric keratoconus is more aggressive than adult keratoconus, which has been explained by structural differences in the cornea between both populations. High rates of progression were documented in pediatric populations. While corneal collagen cross-linking, intracorneal ring segments and penetrating keratoplasties have been used as therapies in the pediatric population, the literature overwhelmingly shows higher rates of failure and progression despite these measures as compared to adults.

CONCLUSION

Pediatric keratoconus is more aggressive than adult keratoconus, and current therapies used in adults may not be sufficient for the pediatric population.

Corneal epithelial and stromal thickness changes in myopic orthokeratology and their relationship with refractive change

Purpose

To investigate topographic changes in corneal epithelial thickness (CET) and stromal thickness following orthokeratology (OK) and to determine associated factors affecting refractive changes.

Methods

This study investigated the topographic changes in CET and stromal thickness in 60 myopic eyes that were fitted with OK lenses. CET and stromal thickness were obtained using spectral-domain optical coherence tomography (OCT) before and after OK lens wear. Changes in refractive error and corneal topography data were obtained. The correlation between refractive change and corneal thickness change, and various refractive, lens, and topographic parameters were analyzed using simple regression analysis.

Results

Mean refractive error changed by 1.75 ± 0.79 diopters (D). The mean CET of the center zone (2 mm in diameter), paracenter (2 to 5 mm annular ring: 1 to 2.5 mm from center), and mid-periphery (5 to 6 mm annular ring: 2.5 to 3 mm from center) changed by -8.4, -1.4, and +2.7 μm, respectively, after OK lens wear. There was an increase of 2.0, 3.3, and 3.9 μm, respectively, in the center, paracenter, and mid-periphery of the stroma. A larger refractive correction was associated with a flatter base curve of the lens, larger decrease in the central epithelium, and smaller treatment diameter in corneal topography.

Conclusion

OK lenses caused the central corneal epithelium to thin while the mid-peripheral epithelium and stroma became thicker. Refractive changes during OK are associated with changes in central epithelial thickness, while stromal changes did not contribute significantly.

Central Corneal Thickness Increase Due to Stromal Thickening With Diabetic Peripheral Neuropathy Severity

PURPOSE

To investigate the relationship between central corneal thickness (CCT) and diabetes disease severity among patients with diabetic peripheral neuropathy (DPN) compared with controls.

METHODS

In this cross-sectional study, 34 participants were examined. DPN status was assessed by clinical examination, nerve conduction studies, and quantitative sensory testing. All participants underwent comprehensive eye examination that included intraocular pressure measured by Goldmann applanation tonometry. CCT was measured by ultrasound pachymetry, and the thickness of corneal layers was assessed by corneal confocal microscopy. Association of CCT and DPN was examined using ANOVA.

RESULTS

Among the 34 participants, there were 9 controls, 16 patients with mild DPN, and 9 patients with severe DPN. CCT was significantly increased in the DPN groups compared with controls (P = 0.0003). Mean CCT among controls was 552.7 ± 29.2 μm compared with 583.4 ± 25.0 μm in the mild DPN group and 613.3 ± 28.8 μm in the severe DPN group. In addition, stromal thickness differed significantly between the 3 study groups (P = 0.045). Mean stromal thickness among controls was 439.5 ± 23.5 μm compared with 478.9 ± 37.5 μm in the mild DPN group and 494.5 ± 39.1 μm in the severe DPN group.

CONCLUSIONS

This study demonstrates that CCT increases with DPN severity because of an increase in stromal thickness. CCT increase associated with DPN has important clinical implications including glaucoma progression, keratoconus susceptibility, and intraocular pressure assessment and should be accounted for when evaluating patients with diabetes.

The Corneal Basement Membranes and Stromal Fibrosis

Purpose

The purpose of this review was to provide detailed insights into the pathophysiology of myofibroblast-mediated fibrosis (scarring or late haze) after corneal injury, surgery, or infection.

Method

Literature review.

Results

The epithelium and epithelial basement membrane (EBM) and/or endothelium and Descemet's basement membrane (BM) are commonly disrupted after corneal injuries, surgeries, and infections. Regeneration of these critical regulatory structures relies on the coordinated production of BM components, including laminins, nidogens, perlecan, and collagen type IV by epithelial, endothelial, and keratocyte cells. Whether a cornea, or an area in the cornea, heals with transparency or fibrosis may be determined by whether there is injury to one or both corneal basement membranes (EBM and/or Descemet's BM) and delayed or defective regeneration or replacement of the BM. These opaque myofibroblasts, and the disordered extracellular matrix these cells produce, persist in the stroma until the EBM and/or Descemet's BM is regenerated or replaced.

Conclusions

Corneal stromal fibrosis (also termed "stromal scarring" or "late haze") occurs as a consequence of BM injury and defective regeneration in both the anterior (EBM) and posterior (Descemet's BM) cornea. The resolution of fibrosis and return of stromal transparency depends on reestablished BM structure and function. It is hypothesized that defective regeneration of the EBM or Descemet's BM allows key profibrotic growth factors, including transforming growth factor beta-1 (TGF-β1) and TGF-β2, to penetrate the stroma at sustained levels necessary to drive the development and maintenance of mature opacity-producing myofibroblasts from myofibroblast precursors cells, and studies suggest that perlecan and collagen type IV are the critical components in EBM and Descemet's BM that bind TGF-β1, TGF-β2, platelet-derived growth factor, and possibly other growth factors, and regulate their bioavailability and function during homeostasis and corneal wound healing.

Cell-laden and orthogonal-multilayer tissue-engineered corneal stroma induced by a mechanical collagen microenvironment and transplantation in a rabbit model

The development of functional therapies for corneal repair and regeneration is a pressing issue. Corneal stroma provides the principal functions of the cornea. However, because of the highly organized nature of the stromal matrix, the attempts to reproduce corneal stroma might follow a scar model. Here, we have developed a protocol for the efficient generation of a cell-laden and orthogonal-multilayer tissue-engineered (TE) corneal stroma, which is induced by the mechanical effects of compressed collagen (CC) or stretched compressed collagen (SCC). Within SCC, with applied compression and force extension, collagen microfibres and corneal stromal cells (CSCs) are arranged orderly, while collagen fibres and CSCs in CC are randomly arranged. Dehydrated SCC has higher tensile strength than dehydrated CC. Hydrated SCC has similar transparency with hydrated native corneal stroma. Compared with those cultured on tissue culture plates (TCP), down-regulation of the genes and proteins of cytoskeleton, activation, proliferation, collagen and TRPV4, up-regulation of proteoglycans, gap junction proteins and TRPA1 are in CSCs of CC and SCC. Moreover, SCC and CC grafts displayed biocompatibility and integration with host corneal tissue after rabbit intra-corneal stromal transplantation by wk 6 under slit lamp microscopy, in vivo confocal microscopy and histological examination. The SCC model facilitates the construction of physiological feature TE corneal stroma, which serves as a foundation for physiological TE construction of other tissues.

STATEMENT OF SIGNIFICANCE

The development of functional therapies for corneal repair and regeneration is a pressing issue. Corneal stroma provides the principal functions of the cornea. Here, we have developed a protocol for the efficient generation of a cell-laden and orthogonal-multilayer tissue-engineered (TE) corneal stroma, which is induced by the mechanical effects of compressed collagen (CC) or stretched compressed collagen (SCC). These models facilitate the construction of physiological feature TE corneal stroma, which serves as a foundation for physiological TE construction of other tissues and helps to reverse fibrosis pathologies in general.

Corneal crosslinking for keratoconus in Japanese populations: one year outcomes and a comparison between conventional and accelerated procedures

PURPOSE

We retrospectively investigated the efficacy of corneal crosslinking (CXL) on progressive keratoconus in a Japanese population and compared the outcomes of conventional and accelerated CXL.

STUDY DESIGN

A retrospective cohort study METHODS: A total of 108 consecutive eyes in 95 patients (75 men; 21.9 ± 6.2 years) with progressive keratoconus were enrolled. The epithelium was ablated in all eyes. After presoaking the corneal stroma in riboflavin, UV-A was irradiated at 3.0 mW/cm² (conventional CXL) for 30 min on 23 eyes and 18.0 mW/cm² for 5 min (accelerated CXL) on 85 eyes. Best spectacle-corrected visual acuity (BSCVA), manifest refraction, keratometric value, corneal thickness, corneal endothelial cell density (ECD), intraocular pressure, and complications were evaluated at 1, 3, 6, and 12 months after the procedure.

RESULTS

BSCVA, manifest refraction, ECD, and corneal thickness did not change significantly after both procedures. The keratometric value was significantly decreased from the preoperative value at 12 months (p < 0.001). Progression to more than 1.0 D after CXL was observed in 10 eyes (9.3%). The ΔKmax was negatively associated with preoperative Kmax (p < 0.001) and positively associated with preoperative thinnest corneal thickness (p < 0.001). Both treatment modules showed no significant difference in all parameters.

CONCLUSION

CXL was as effective in treating keratoconus in Japanese patients as in individuals of other ethnicities. Overall, CXL could be performed using either the conventional or accelerated approach to halt the progression of keratoconus in Japanese populations.

A report of 10 patients with Acanthamoeba keratitis

CLINICAL CASES

Cases are presented of 10 patients with Acanthamoeba keratitis treated between 2008 and 2017. All were contact lens wearers. All of them received treatment with a biguanide combined with a diamidine. In 3 cases the infestation did not exceed the superficial stroma, responding to topical treatment. In 7, the infection reached the deep stroma, with 6 of these cases requiring penetrating keratoplasty (PKP), 3 of them therapeutic PKP because of perforation risk or ocular spreading. The visual acuity improved in all the cases.

CONCLUSION

The infestation depth at the time of diagnosis appears to be the main risk factor for requiring a PKP.

Customized Topography-Guided Corneal Collagen Cross-linking for Keratoconus

PURPOSE

To compare the efficacy and safety of topography-guided corneal collagen cross-linking (TG-CXL) to conventional corneal CXL (C-CXL) in progressive keratoconus.

METHODS

In this prospective, nonrandomized clinical trial, 60 eyes of 60 patients were scheduled to receive either TG-CXL (30 eyes with deepithelialization focused on the cone, riboflavin application for 10 minutes, and 30 mW/cm² pulsed ultraviolet-A irradiance pattern according to topography) or C-CXL (30 eyes treated in accordance with the Dresden protocol). Patients were observed for 1 year postoperatively. Maximum keratometry (Kmax), mean keratometry in the inferior part of the cornea (I index), corrected distance visual acuity (CDVA), demarcation line observed in optical coherence tomography, and nerves and cell densities analyzed by confocal microscopy were compared preoperatively and at 1 year postoperatively.

RESULTS

The difference was significant for both Kmax (P < .01) and I index (P < .01) between the two groups. CDVA improved significantly in the TG-CXL (0.2162 ± 0.2495 logMAR, P < .05) versus the C-CXL (0.2648 ± 0.2574 logMAR, P = .104) group. A stromal demarcation line was observed in both treatment groups, with similar depth at the top of the cone (P = .391), but it was shallower at the surrounding area in the TG-CXL group (P < .0001). Stromal evaluation by confocal microscopy showed less damage and faster healing in the surrounding area than on the cone area in the TG-CXL group.

CONCLUSIONS

At 1 year postoperatively, TG-CXL seems to be as safe as C-CXL with stronger flattening in Kmax and I index and better improvement in CDVA. TG-CXL induces a biological gradient between the cone and the surrounding area that facilitates nerve and cell recovery. [J Refract Surg. 2017;33(5):290-297.].

AS-OCT as a Rescue Tool During Difficult Lenticule Extraction in SMILE

PURPOSE

To report a case of lenticule adherent to the anterior cap during small incision lenticule extraction (SMILE) and its subsequent management aided by anterior segment optical coherence tomography (AS-OCT).

METHODS

Case report.

RESULTS

A 24-year-old woman presented with high myopia of -8.00 -0.50 @ 180° in the right eye and -8.00 -0.25 @ 180° in the left eye and underwent SMILE. In the right eye, difficulty was experienced in separating the lenticule from adjacent stroma. AS-OCT examination confirmed the presence of the lenticule adherent to the anterior stromal cap with the plane of dissection visible posterior to the lenticule. A Sinskey hook was used to lift off the peripheral edge of the lenticule from the anterior cap and the stripping of the lenticule was continued in a centripetal fashion until a small edge of the lenticule was rolled over. The lenticule was then completely separated from the overlying stromal cap and extracted through the side cut using forceps. Postoperative AS-OCT confirmed complete removal of the lenticule. Postoperative uncorrected distance visual acuity was 20/40 on day 1 and 20/20 on day 30 with a clear interface.

CONCLUSIONS

AS-OCT-guided identification of the retained lenticule followed by Sinskey hook-assisted lenticule extraction aids in completion of the surgical procedure in the same sitting with optimal visual and anatomical outcomes. [J Refract Surg. 2017;33(5):352-354.].

A New Matrix Therapy Agent for Faster Corneal Healing and Less Ocular Discomfort Following Epi-off Accelerated Corneal Cross-linking in Progressive Keratoconus

PURPOSE

To investigate the hypothesis that a new matrix therapy agent (ReGeneraTing Agent, [RGTA]) would speed up the corneal reepithelialization, improve stromal healing, and reduce ocular symptoms after epi-off corneal cross-linking (CXL).

METHODS

Sixty eyes of 60 patients with progressive keratoconus were enrolled in the study. Epi-off accelerated CXL was performed in all patients. Sixty eyes were randomized into two groups according to use of RGTA eye drops prior to contact lens fitting at the end. Identical medical agents were started postoperatively for the two groups. All participants were monitored on 3 consecutive days after the CXL. Ocular pain, burning, stinging, tearing, photophobia, conjunctival hyperemia, and corneal healing status were evaluated.

RESULTS

By day 2, 25 eyes (83.3%) with RGTA revealed complete healing compared to 4 eyes (13.3%) that revealed complete healing in the control group (P < .001). All eyes had complete corneal epithelial defect closure by day 3 in both groups. Ocular pain scores were lower in the RGTA group on days 0, 1, and 2 (all P < .05). Burning scores were lower on days 1 and 2; stinging scores on days 2 and 3; tearing scores on days 2 and 3; and photophobia on days 1 and 2 (P < .05) in the RGTA group compared to the control group.

CONCLUSIONS

RGTA ophthalmic solution facilitates corneal healing by reconstructing the extracellular matrix in the wound area, leading to an earlier relief of symptoms for patients. [J Refract Surg. 2017;33(3):163-170.].

Customized Corneal Cross-linking Using Different UVA Beam Profiles

PURPOSE

To evaluate the performance of different customized corneal cross-linking (CXL) methods.

METHODS

This was a single-center interventional, prospective, longitudinal case series. Four different customized CXL methods were evaluated in keratoconic eyes: (1) uniform (uniform intensity ultraviolet-A [UVA] beam [9 mW/cm²] for 10 minutes) (n = 12 eyes); (2) sector axial map (sector-based UVA irradiation) (n = 12 eyes); (3) ring axial map (concentric rings of UVA beam intensity centered at the steepest curvature of the anterior axial map) (n = 12 eyes); and ring tangential map (same as the ring axial map but centered at the steepest curvature of the anterior tangential map) (n = 14 eyes). Peak UVA energy density in the sector and ring axial map (and ring tangential map) protocols did not exceed 15.0 and 10.8 J/cm², respectively. A 0.1% riboflavin solution was applied after epithelium removal. Corneal tomography and visual acuity were assessed before and 6 months after CXL.

RESULTS

Average and peak energy density was lowest in the ring tangential protocol and highest in the sector axial map group (P < .001). Treated area was lowest in the ring tangential map group and highest in the uniform group (P < .001). Decrease in curvature was similar among the uniform, sector axial map, and ring axial map groups (P < .05). The ring tangential map group had the greatest decrease in curvature per unit energy dose to the cornea (P < .05). Improvement in uncorrected (0.081 ± 0.056 logMAR) and corrected (0.041 ± 0.026 logMAR) distance visual acuity per unit energy density was greatest in the ring tangential map group (P > .05).

CONCLUSIONS

When normalized to the average energy density, the ring tangential map protocol appeared to provide maximum flattening and improvement in visual acuity. Further studies with larger sample sizes are needed to validate the findings of this pilot study. [J Refract Surg. 2017;33(10):676-682.].