Salzmann's Nodular Degeneration in Refractive Surgery: The Earlier Hit Hypothesis of EBM Injury-Related Fibrosis of the Subepithelial Space and Deeper Corneal Extension.

PURPOSE: To review the atypical development of Salzmann's nodular degeneration (SND) after two cases of laser in situ keratomileusis (LASIK) and one case of photorefractive keratomileusis (PRK), and to highlight the pathophysiology of SND and its treatment. METHODS: Three cases of SND (two following LASIK performed with microkeratomes and one following PRK) were reviewed and Pubmed.gov and internet searches were performed. RESULTS: SND is myofibroblast-generated fibrosis in the subepithelial space between the epithelium and Bowman's layer that develops years or decades after traumatic, surgical, infectious, or inflammatory injuries to the cornea in which the epithelial basement membrane is damaged in one or more locations and does not fully regenerate. It is hypothesized based on these cases, and the previous immunohistochemistry of other investigators, that myofibroblast precursors, such as fibrocytes or corneal fibroblasts, that enter the subepithelial space are driven to develop into myofibroblasts, which slowly proliferate and extend the fibrosis, by transforming growth factor-beta from epithelium and tears that passes through the defective epithelial basement membrane. These myofibroblasts and the disordered collagens, and other extracellular matrix components they produce, make up the subepithelial opacity characteristic of SND. Nodules are larger accumulations of myofibroblasts and disordered extracellular matrix. If the injury is associated with damage to the underlying Bowman's layer and stroma, as in LASIK flap generation, then the myofibroblasts and fibrosis can extend into Bowman's layer and the underlying anterior stroma. CONCLUSIONS: SND fibrosis often extends into Bowman's layer and the anterior stroma if there are associated Bowman's defects, such as incisions or lacerations. In the latter cases, SND frequently cannot be removed by simple scrape and peel, as typically performed for most common SND cases, but can be trimmed to remove the offending tissue. This condition is more accurately termed Salzmann's subepithelial fibrosis. [J Refract Surg. 2024;40(5):e279-e290.].

Identification of A Novel TGFBI Gene Mutation (p.Serine524Cystine) Associated with Late Onset Recurrent Epithelial Erosions and Bowman Layer Opacities.

BACKGROUND: Most transforming growth factor beta-induced (TGFBI) corneal dystrophies are associated with a characteristic phenotype, clinical course, and a conserved mutation in the TGFBI gene. However, we report a novel TGFBI missense mutation associated with a late-onset, variant Bowman layer dystrophy. METHODS: Participants underwent slit-lamp examination and multimodal imaging. Polymerase chain reaction amplification and Sanger sequencing were performed on saliva-derived genomic DNA to screen TGFBI exons 4 and 12 as well as COL17A1 exon 46. PolyPhen-2 and SIFT were used to predict the functional impact of any identified variants. RESULTS: A 56-year-old Thai woman reported a four-year history of decreased vision and intermittent eye irritation, suggestive of recurrent epithelial erosions, in both eyes. Slit-lamp exam revealed bilateral, irregular, limbal-sparing Bowman layer opacities, which were also noted on anterior segment optical coherence tomography. Phototherapeutic keratectomy was performed in the right eye, improving the best-corrected visual acuity from 20/50 to 20/30. Sequencing of the TGFBI gene revealed a novel heterozygous, missense mutation in exon 12 (c.1571 C > G; p.Ser524Cys), which was present in an affected son and absent in an unaffected son, and was predicted to be damaging by PolyPhen-2 and SIFT. The patient was diagnosed with a variant Bowman layer dystrophy given the late onset of an atypical phenotype and the identification of a novel TGFBI mutation. CONCLUSIONS: A novel TGFBI missense mutation is associated with a late-onset Bowman layer dystrophy. Given the atypical clinical appearance and course, molecular genetic analysis was utilized to establish a definitive diagnosis.

Large Field of View Corneal Epithelium and Bowman's Layer Thickness Maps in Keratoconic and Healthy Eyes.

PURPOSE: To assess differences between epithelium thickness (ET) and Bowman's layer thickness (BLT) maps in keratoconic eyes and healthy eyes. DESIGN: Cross-sectional study. METHODS: Setting: institutional. STUDY POPULATION: 47 patients (1 eye) with keratoconus (KC) and 20 healthy subjects (1 eye). OBSERVATION PROCEDURE: epithelium and Bowman's layer measurements were performed by using custom-designed polarization-sensitive optical coherence tomography (PS-OCT) with a conical scanning optics design. En face corneal ET and BLT maps with a diameter of 11 mm were computed. Main outcome measurements were mean ET and BLT of 25 sectors; the thinnest (minET, minBLT) and thickest sectors (maxET, maxBLT) were assessed. Ratios between thinnest/thickest sectors (R1) and between mean ET and BLT of the inferior temporal quadrant/superior nasal quadrant (R2) were calculated (R1ET, R1BLT; R2ET, R2BLT). Receiver operator characteristic (ROC) curve analysis was used to assess the diagnostic power of statistically different parameters. RESULTS: In healthy eyes, smooth ET maps were observed. KC eyes showed a "doughnut pattern." The BLT maps of healthy eyes had a smooth appearance, but highly irregular "moth"-like damage pattern could be observed in keratoconic eyes. Highest area under the curve values were found for the thinnest sector of the BLT map, the R1ET, and the thinnest sector of the ET map. CONCLUSIONS: PS-OCT imaging enables the visualization of significant differences of the corneal epithelium and the Bowman's layer in en face maps covering almost the entire cornea. ET and BLT profiles could clearly show their diagnostic importance for the distinguishing of keratoconic eyes and healthy eyes.

Bowman's topography for improved detection of early ectasia.

The aim of this study was to evaluate whether OCT topography of the Bowman's layer and artificial intelligence (AI) can result in better diagnosis of forme fruste (FFKC) and clinical keratoconus (KC). Normal (n = 221), FFKC (n = 72) and KC (n = 116) corneas were included. Some of the FFKC and KC patients had the fellow eye (VAE-NT) with normal topography (n = 30). The Scheimpflug and OCT scans of the cornea were analyzed. The curvature and surface aberrations (ray tracing) of the anterior corneal surface [air-epithelium (A-E) interface in OCT] and epithelium-Bowman's layer (E-B) interface (in OCT only) were calculated. Four random forest models were constructed: (1) Scheimpflug only; (2) OCT A-E only; (3) OCT E-B only; (4) OCT A-E and E-B combined. For normal eyes, both Scheimpflug and OCT (A-E and E-B combined) performed equally in identifying these eyes (P = .23). However, OCT A-E and E-B showed that most VAE-NT eyes were topographically similar to normal eyes and did not warrant a separate classification based on topography alone. For identifying FFKC eyes, OCT A-E and E-B combined performed significantly better than Scheimpflug (P = .006). For KC eyes, both Scheimpflug and OCT performed equally (P = 1.0). Thus, OCT Topography of Bowman's layer significantly improved the detection of FFKC eyes.

Microdistortions in Bowman's Layer 3 Years After SMILE for Myopia.

PURPOSE: To investigate the characteristics and changes in microdistortions in Bowman's layer 3 years after small incision lenticule extraction (SMILE). METHODS: In this non-randomized, prospective study, 50 eyes of 28 patients who received SMILE with a mean spherical equivalent of -6.72 ± 1.41 diopters (D) were divided into a thin lenticule group (lenticule thickness ⩽ 135 µm) and a thick lenticule group (lenticule thickness > 135 µm). Examinations were performed preoperatively and 1 day, 1 month, and 3 years after SMILE. Microdistortions in Bowman's layer determined via optical coherence tomography were analyzed digitally. RESULTS: All patients completed the follow-up with no complications. Three years after SMILE, no eyes exhibited loss of corrected distance visual acuity. The safety index was 1.20 ± 0.15 and the efficacy index was 1.01 ± 0.10. The respective mean lengths of microdistortions at 1 day, 1 month, and 3 years after SMILE were 2,397.47 ± 1,777.22, 3,444.87 ± 2,145.82, and 1,283.81 ± 1,184.43 µm. The respective mean microdistortion lengths at each time-point were 1,781.29 ± 17,78.15, 2,617.78 ± 1,949.67, and 1,112.95 ± 1,245.88 µm in the thin lenticule group and 2,692.10 ± 1,825.20, 3,739.20 ± 2,072.60, and 1,332.44 ± 1,137.33 µm in the thick lenticule group. CONCLUSIONS: Microdistortions in Bowman's layer can remain 3 years after SMILE, but their lengths decrease over time. Thicker lenticules were associated with the early occurrence of microdistortions, but this effect decreased in the long term. [J Refract Surg. 2019;35(2):96-101.].

Thickness changes in the corneal epithelium and Bowman's layer after overnight wear of silicone hydrogel contact lenses.

BACKGROUND: To investigate thickness changes in the corneal epithelium and Bowman's layer after overnight silicone hydrogel contact lens (CL) wear by using ultra-high resolution optical coherence tomography (UHROCT). METHODS: Eleven subjects without CL wearing history were recruited for this study. An UHROCT was used to measure the thickness of the epithelium (ET), Bowman's layer (BT), stroma (ST), and total cornea (CCT) at the center of both eyes. A silicone hydrogel CL was inserted in the right eye of each subject, and the fellow non-CL wearing left eye served as the control. The lens was inserted at 9:30 pm and removed at 8:00 am the next morning. The subjects were evaluated at 9:00 pm (baseline), 9:30 pm (lens insertion), 10:00 pm (before sleep), 7:00 am (waking), 7:30 am, and 8:00 am (lens removal). RESULTS: Compared to the lens insertion level, the ET of the lens-wearing eye increased by 5.73% at eye opening (P = 0.001). The ET of the non-CL wearing eye and the BT in both eyes did not change after overnight CL wear. Compared to baseline, the CCT of the lens-wearing eye increased by 2.87% upon waking (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, compared to baseline, the CCT of the non-CL wearing eye did not increase upon waking (P = 0.105). CONCLUSIONS: By using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea. TRIAL REGISTRATION: Retrospectively registered. Registration number: ChiCTR1800015115 . Registered 07 March 2018.

Short-term Observation of Intraocular Scattering and Bowman's Layer Microdistortions After SMILE-CCL.

PURPOSE: To investigate changes in intraocular scattering and Bowman's layer microdistortions after femtosecond laser small incision lenticule extraction using the continuous curvilinear lenticulerhexis technique (SMILE-CCL). METHODS: In this prospective study, 93 eyes of 93 patients (44 women, 49 men) were treated with SMILE-CCL. Mean age was 26.09 ± 4.39 years and mean spherical equivalent was -6.31 ± 2.16 diopters. The Objective Scatter Index (OSI) was examined with an objective optical quality analysis system. Bowman's layer microdistortions in the central 4-mm optical zone were measured using Fourier-domain optical coherence tomography. RESULTS: The mean OSI value increased from 0.67 preoperatively to 1.09 at 20 days, and then decreased to 0.84 at 3 months (P < .05). Microdistortions were observed in 62.37% of the eyes at 20 days and 48.39% at 3 months postoperatively (P < .05). The width of the microdistortions per meridian was 283.18 ± 197.19 µm at 20 days; this decreased to 156.00 ± 159.86 µm at 3 months (P < 0.05). Regression analysis models revealed that older age (b = 0.02, P = .03) and higher preoperative spherical equivalent (b = -0.09, P < .05) resulted in higher postoperative OSI values; no significant association was found between postoperative OSI values and microdistortion-related parameters (P > .05). Higher preoperative spherical equivalent (b = -0.28, P = .01) and thinner preoperative corneal thickness (b = -0.02, P = .01) were associated with more microdistortions. CONCLUSIONS: SMILE induced a temporary increase in OSI values and Bowman's layer microdistortions. The microdistortions did not influence intraocular scattering. [J Refract Surg. 2018;34(6):387-392.].

Epithelial Recurrent Erosion Dystrophy Secondary to COL17A1 c.3156C>T Mutation in a Non-white Family.

PURPOSE: To report the identification of the collagen, type XVII, alpha 1 (COL17A1) c.3156C>T mutation associated with epithelial recurrent erosion dystrophy (ERED) in a Thai family. METHODS: Slit-lamp examination was performed to determine the affected status of each member of a Thai family, with multiple members demonstrating scattered Bowman layer opacities. After genomic deoxyribonucleic acid (DNA) was isolated from saliva, polymerase chain reaction (PCR) amplification and Sanger sequencing were performed to screen COL17A1 and exons 4 and 12 of the transforming growth factor ß-induced gene. RESULTS: The 67-year-old proband and her 4 siblings were examined by slit-lamp biomicroscopy, which identified bilateral subepithelial opacities in the proband and in one of the 4 siblings. In both the proband and the affected sister, screening of the COL17A1 gene identified a heterozygous c.3156C>T synonymous mutation that has been previously demonstrated to introduce a cryptic splice donor site, likely leading to aberrant splicing of COL17A1. This mutation was not identified in the unaffected siblings, and no mutations were identified in exons 4 and 12 of the transforming growth factor ß-induced gene in any of the screened family members. CONCLUSIONS: ERED associated with a COL17A1 mutation has been previously reported in only 6 families, all white. Identification of the c.3156C>T mutation, previously identified in 5 of these 6 families, in the Thai family we report indicates conservation of the genetic basis of ERED across different races and underscores the importance of ophthalmologists around the globe being familiar with ERED, which has only recently become a recognized corneal dystrophy.

Direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus.

PURPOSE: To compare the tomography of the corneal epithelium and Bowman layer in eyes with moderate to severe keratoconus before and after epithelial debridement. SETTING: University hospital tertiary referral center. DESIGN: Prospective case series. METHODS: Dual-channel Scheimpflug combined with Placido-disk tomography was used to measure the corneal variables in eyes with keratoconus having corneal crosslinking immediately before and after epithelial debridement. The differences in pachymetry, axial keratometry, astigmatism magnitude, asphericity, total corneal power, and spherical aberrations were computed. RESULTS: The study comprised 30 eyes of 30 patients. After epithelial removal, the central (0.0 to 4.0 mm) and midperipheral (4.0 to 7.0 mm) corneal zones were significantly thinner mean (21 µm ± 14 [SD] and 35 ± 44 µm, respectively). The mean anterior axial flat keratometry (K) (+1.71 diopters [D]), steep K (+2.14 D), maximum K (+2.13 D), corneal astigmatism (+1.11 D), asphericity (-0.31), and total corneal power changes (+2.03 D) were significantly different after epithelial debridement. There were no significant changes in posterior corneal flat K or steep K, posterior corneal astigmatism, or posterior asphericity. There were no significant differences in the mean astigmatic axis (anterior or posterior corneal surface) or spherical aberration after epithelial debridement. CONCLUSIONS: In eyes with moderate to severe keratoconus, the tomography of Bowman layer was significantly steeper than that of the epithelium; thus, epithelial debridement increased the magnitude of anterior corneal keratometry, astigmatism, and prolateness. These data suggest that the corneal epithelium smooths the underlying Bowman layer irregularity in keratoconus.

Noncontact Quantification of Topography of Anterior Corneal Surface and Bowman's Layer With High-Speed OCT.

PURPOSE: To quantify keratometry and wavefront aberration of the anterior corneal surface and epithelium-Bowman's layer interface using anterior segment optical coherence tomography (OCT). METHODS: Twenty-five normal eyes and 25 eyes with keratoconus were retrospectively analyzed. The anterior corneal edge and epithelium-Bowman's layer interface were segmented from 12 distortion-corrected OCT B-scans. Axial tangential curvatures and wavefront aberration were calculated by ray tracing and 6th order Zernike analyses. All eyes underwent simultaneous imaging with Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany). The Pentacam elevation data were used for aberration analyses using the same ray-tracing method. The paired t test was used to compare the variables. RESULTS: In normal eyes, mean steep axis and maximum keratometry of OCT of the anterior corneal surface and epithelium-Bowman's layer interface were significantly greater than the same of the Pentacam anterior corneal surface (P < .05). Mean root mean square of higher order aberrations of the OCT surfaces was greater than the same of the Pentacam surface by a factor of 4. In eyes with keratoconus, mean steep axis and maximum keratometry of the OCT epithelium-Bowman's layer interface was the greatest (P < .05). Mean root mean square of the higher order aberrations and vertical coma of the OCT epithelium-Bowman's layer interface was the greatest (P < .05). In general, the aberrations of the OCT epithelium-Bowman's layer interface were significantly greater than those of the Pentacam anterior corneal surface. CONCLUSIONS: A noncontact method to quantify the topography and aberrations of corneal surfaces with OCT was presented. OCT measurements yielded greater curvature and aberrations than Pentacam in both normal and keratoconic eyes. [J Refract Surg. 2017;33(5):330-336.].

New histopathologic and ultrastructural findings in Reis-Bücklers corneal dystrophy caused by the Arg124Leu mutation of TGFBI gene.

BACKGROUND: Reis-Bücklers corneal dystrophy (RBCD) was consistently reported as a corneal dystrophy only affected Bowman's layer and superficial corneal stroma, and superficial keratectomy was a recommendation surgery for treatment in literatures. The study reported new histopathological and ultrastructural findings in RBCD caused by the Arg124Leu mutation of transforming growth factor induced (TGFBI) gene in a four-generation Chinese pedigree. METHODS: Subjects including eight patients and seven unaffected family members received slit-lamp biomicroscopy and photography. DNA was obtained from all subjects, and exons 4 and 11 to 14 of TGFBI gene were analyzed by polymerase chain reaction and the products were sequenced. Anterior segment optical coherence tomography (AS OCT) and in vivo confocal microscopy were conducted for ten eyes of five patients. Based on the results of AS OCT and in vivo confocal microscopy, deep anterior lamellar keratoplasty (DLKP) using cryopreserved donor cornea was applied for four eyes of four patients. Four lamellar dystrophic corneal buttons were studied by light and transmission electron microscopy, and TGFBI immunohistochemistry. RESULTS: Eight patients had typical clinical manifestations of RBCD presenting recurrent painful corneal erosion starting in their early first decades, along with age-dependent progressive geographic corneal opacities. TGFBI sequencing revealed a heterozygous mutation, Arg124Leu in all eight patients. Anterior segment optical coherence tomography and in vivo confocal microscopy showed the dystrophic deposits involved not only in subepithelial and superficial stroma, but also in mid- or posterior stroma in four examined advanced eyes. Light microscopy showed Bowman's layer was absent, replaced by abnormal deposits stain bright red with Masson's trichrome. In superficial cornea, the deposits stacked and produced three to five continuous bands parallel to the corneal collagen lamellae. In mid- to posterior stroma, numerous granular or dot- like aggregates were heavily scattered, and most of them presented around the nuclei of stromal keratocytes. Transmission electron microscopy revealed the multiple electron-dense rod-shaped deposits aggregated and formed a characteristic pattern of three to five continuous bands in superficial cornea, which were similar to those seen under light microscopy. In mid- to posterior stroma, clusters of rod-shaped bodies were scattered extracellular or intracellular of the stromal keratocytes between the stromal lamellae suggesting the close relationship between mutated proteins and keratocyte. CONCLUSIONS: The study offer evidences indicating DLKP is a viable treatment option for advanced RBCD to avoid recurrence, and the mutated TGFBIp in dystrophic corneas are of keratocytes origin.

Value of corneal epithelial and Bowman's layer vertical thickness profiles generated by UHR-OCT for sub-clinical keratoconus diagnosis.

Ultra-high resolution optical coherence tomography (UHR-OCT) can image the corneal epithelium and Bowman's layer and measurement the thicknesses. The purpose of this study was to validate the diagnostic power of vertical thickness profiles of the corneal epithelium and Bowman's layer imaged by UHR-OCT in the diagnosis of sub-clinical keratoconus (KC). Each eye of 37 KC patients, asymptomatic fellow eyes of 32 KC patients, and each eye of 81 normal subjects were enrolled. Vertical thickness profiles of the corneal epithelium and Bowman's layer were measured by UHR-OCT. Diagnostic indices were calculated from vertical thickness profiles of each layer and output values of discriminant functions based on individual indices. Receiver operating characteristic curves were determined, and the accuracy of the diagnostic indices were assessed as the area under the curves (AUC). Among all of the individual indices, the maximum ectasia index for epithelium had the highest ability to discriminate sub-clinical KC from normal corneas (AUC = 0.939). The discriminant function containing maximum ectasia indices of epithelium and Bowman's layer further increased the AUC value (AUC = 0.970) for sub-clinical KC diagnosis. UHR-OCT-derived thickness indices from the entire vertical thickness profiles of the corneal epithelium and Bowman's layer can provide valuable diagnostic references to detect sub-clinical KC.

The role of ultraviolet radiation in the pathogenesis of pterygia (Review).

Pterygium is a common ophthalmic disease affecting humans only. Extensive epidemiological data have demonstrated a causative effect of chronic ultraviolet (UV) radiation on pterygia. Progress has been made in determining the origin of pterygia, their nasal predilection and wing­shaped appearance, and the roles of UV radiation in the initiation and the development of pterygia. In the present review, the current understanding of the involvement of UV radiation in the pathogenesis of pterygia is summarized. This involvement includes the alteration of limbal stem cells and fibroblasts that contribute to the initiation of pterygia and the induction of various pro­inflammatory cytokines, growth factors and matrix metalloproteinases that promote the progression of pterygia. Further elucidation of the roles of UV radiation in the pathogenesis of pterygia may help to encourage individuals at risk of developing pterygia to take preventive measures and aid researchers in the development of novel targeted therapeutic agents to treat pterygia.

Correlação clínico-patológica em ceratites fúngicas e uma possível evidência de infecção oportunista: relato de dois casos / Clinicopathological correlation in fungal keratitis and a possible evidence of opportunistic infection: a report of two cases

RESUMO Os autores relatam dois casos de ceratite fúngica, que apresentam em comum no exame histopatológico: a ausência de epitélio, sem ulceração e a integridade da camada de Bowman com a presença de formas fúngicas no seu interior. São sugeridos prováveis mecanismos de recidiva das ceratites fúngicas, ressaltando uma possível "via externa não usual", por meio da penetração do fungo através da camada de Bowman íntegra. A existência desta infecção oportunista não está relatada na literatura oftalmológica e são necessárias mais evidências para que seja considerada como tal.

ABSTRACT The authors describe two cases of fungal keratitis which, upon histopathological examination, are found to have in common the absence of epithelium, without ulceration and the lack of integrity of the Bowman's layer with the presence of fungal forms in their interior. Through them the authors suggest probable mechanisms of recurrence of fungal keratitis, highlighting the possible existence of an "unusual external route" that would occur by the fungus penetration through the full Bowman layer. Although these findings appear not yet reported or recovered in the ophthalmic literature, the authors suggest that they could be possible opportunistic infection signals which, however, require more evidence to be considered as such.

Bowman Break and Subbasal Nerve Plexus Changes in a Patient With Dry Eye Presenting With Chronic Ocular Pain and Vitamin D Deficiency.

PURPOSE: To report the case of a 40-year-old patient with persistent bilateral ocular pain and discomfort for 2 years in whom conventional management of dry eye had failed. Detailed ocular examination, meibography, and tear film evaluation were suggestive of bilateral meibomian gland dysfunction and evaporative dry eye. Topical medication failed to alleviate the patient's symptoms. To identify the cause of pain, imaging was performed with in vivo confocal microscopy and anterior segment spectral domain optical coherence tomography. Systemic evaluation revealed severe vitamin D deficiency with a value of 5.86 ng/mL. METHODS: Case report. RESULTS: In vivo confocal microscopy showed abnormal subbasal nerve plexus morphology, increased dendritic cell density, and enlarged terminal nerve sprouts. A breach in the Bowman layer was detected in both eyes on spectral domain optical coherence tomography. Conventional management having failed, LipiFlow treatment (TearScience, Morrisville, NC) was performed and topical therapy with cyclosporine 0.05%, steroids, and lubricating eye drops was initiated with incomplete symptomatic relief. However, with parenteral therapy for vitamin D deficiency, there was a dramatic improvement in the patient's symptoms. CONCLUSIONS: Inflammation aggravated by vitamin D deficiency results in an altered epithelial profile, Bowman layer damage, recruitment of dendritic cells, and altered subbasal nerve plexus features in patients with chronic dry eye disease. These can serve as potential imaging markers for studying the underlying mechanisms in patients with dry eye disease with persisting symptoms despite aggressive conventional treatment.

The Impact of Flap Creation Methods for Sub-Bowman's Keratomileusis (SBK) on the Central Thickness of Bowman's Layer.

PURPOSE: To determine the impact of flap creation methods for sub-Bowman's keratomileusis (SBK) on central Bowman's layer thickness. METHODS: SBK flaps were made by Moria microkeratome for 20 subjects and by femtosecond (FEMTO) laser for 21 subjects. Corneal sublayer thicknesses were measured by ultra-high resolution optical coherence tomography before SBK and at 1 day, 1 week, 2 weeks, and 1 month afterwards. Each subject was imaged twice on each visit. Thicknesses of central epithelium, Bowman's layer, flap, and total cornea were calculated using a custom-made automated image processing algorithm. The repeatability of sublayer thickness measurements was tested by the intraclass correlation coefficient (ICC) and by the coefficient of repeatability (CoR) at 1 week post-SBK. RESULTS: ICCs of the Moria and FEMTO groups were ≥ 0.959 and ≥ 0.961 respectively for all sublayer measurements. The segmentation CoRs were less than 6.78% and 5.63% respectively. For both groups, microdistortions were present in the epithelium and Bowman's layer after SKB. The flap thickness of the Moria group was 9.8 µm (95% confidence interval: 4.8 - 14.8 µm) thinner than the FEMTO group one day after SBK (independent samples t-test, P < 0.05). Bowman's layer became thicker by 1.6 ± 1.1 µm and 1.7 ± 1.6 µm one day post-SBK for the Moria and FEMTO groups (repeated ANOVA, P < 0.05) and then remained stable. Corneal and sublayer thickness were similar between the two groups. CONCLUSIONS: Central Bowman's layer thickness increased 1 day post-SBK. Flap creation by Moria microkeratome and femtosecond laser did not have significantly different impacts on Bowman's layer thickness following SBK. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR) NO: ChiCTR-OCH-14004525.

Quantitative analysis of Microdistortions in Bowman's Layer using optical coherence tomography after SMILE among different myopic corrections.

PURPOSE: To quantitatively analyze the characteristics of Bowman's layer microdistortions after femtosecond laser small incision lenticule extraction (SMILE) among different myopic corrections, and their correlations with stromal lenticule thickness. METHODS: In this nonrandomized, prospective, controlled study, 63 eyes of 32 consecutive patients undergoing SMILE were divided into three groups according to the preoperative spherical equivalent (SE): greater than -6.00 D (20 eyes), -3.00 to -6.00 D (26 eyes), and -3.00 D or less (17 eyes). Measurement by slit-lamp microscope, uncorrected distance visual acuity (UDVA), manifest refraction, and Fourier-domain optical coherence tomography (FD-OCT) were conducted preoperatively and 1 day and 1 month postoperatively. Index M was calculated according to the OCT images to indicate the quantity of microdistortions in Bowman's layer. RESULTS: Microdistortions in Bowman's layer were observed in 65.0% (13 of 20 eyes) and 30.8% (8 of 26 eyes) in the greater than -6.00 D and -3.00 to -6.00 D groups, respectively, 1 day postoperatively, and in 60% (12 of 20 eyes) and 23.1% (6 of 26 eyes) 1 month later. No Bowman's layer microdistortion was detected in the -3.00 D or less group postoperatively. The quantitative index M of microdistortions was higher in the greater than -6.00 D group than in the -3.00 to -6.00 D group at 1 day and 1 month (P < .05). There was no statistically significant difference between the indexes M on 1 day compared to 1 month. Index M was correlated with the preoperative SE and lenticule thickness (P < .05). CONCLUSION: The incidence and range of microdistortions in Bowman's layer detected after SMILE are positively correlated with the myopic correction. High myopia tends to develop more microdistortions in Bowman's layer after SMILE.

Genes in dizygote twins with Bowman layer corneal dystrophy.

PURPOSE: To report a de novo R124C mutation of transforming growth factor ß-induced (TGFBI) gene in one of dizygotic twins with corneal dystrophy of the Bowman layer. CASE REPORT: An 11-year-old boy was one of dizygotic twins and had a history of bilateral blurred vision and recurrent corneal erosion. Examination of the visual acuity demonstrated 20/40 in his each eye. Biomicroscopy showed bilaterally central corneal subepithelial opacities and some dot opacities in the superficial stroma. Anterior segment optical coherence tomography demonstrated most hyperreflective opacities at the subepithelial layer with some interspersed opacities in the superficial stroma. Confocal microscopy revealed irregular hyperreflective materials in the Bowman layer and the superficial stroma. Several rough filaments were found in the middle layer of stroma, corresponding to a feature of amyloid lattice. The corneas of his parents and dizygotic sister were clear. Sequencing of the TGFBI gene revealed an R124C mutation in the affected boy but not in his three healthy family members. CONCLUSIONS: A de novo R124C mutation of the TGFBI gene may occur in one of dizygotic twins. Patients with an R124C mutation may have clinical features like corneal dystrophy of the Bowman layer. Confocal microscopy can be used to detect subclinical lattice lines, thereby facilitating differential diagnosis.