Central Corneal Epithelial Thickness Research Articles

Comparison of Automated and Manual Measurement of Corneal Epithelial Thickness in Eyes With Limbal Stem Cell Deficiency.

The purpose of this study was to compare the outcomes of manual and automated corneal epithelial thickness (CET) assessments using anterior segment optical coherence tomography in eyes with limbal stem cell deficiency (LSCD). Eighty-seven eyes from 64 patients with LSCD and 65 eyes from 39 healthy subjects were included in this cross-sectional study. OCT images of corneas were acquired using a Fourier-domain anterior segment optical coherence tomography. The automated measurement of CET was obtained using the manufacturer's program and the manual measurements were obtained by 2 masked observers. The average CET was obtained from 3 consecutive epithelial profile maps. The average CET of manual measurement was obtained from 3 consecutive cross-line scans using 3-point measurement as previously described. The central CET was thinner in patients with LSCD compared with healthy individuals by both manual and automated measurements. Automated CET measurements were similar to the manually obtained CET in the healthy controls (r = 0.911). However, there is a lower correlation between the automated and manually obtained CET in the LSCD group (r = 0.497). Manual measurements of CET (39.8 ± 11 μm) in eyes with LSCD were significantly lower than the automated measurements (48.8 ± 7.2 μm, P = 0.001, 95% CI -11.0 to -6.9). The correlations between the automated and manually obtained measurements in the mild, moderate, and severe stages of LSCD were 0.623, 0.632, and 0.378, respectively. There is a large discrepancy between the manual and automated measurements in eyes with LSCD but not in normal eyes. Automated measurements in LSCD exhibited a higher rate of errors and nonuniform measurements due to the presence of subepithelial scars. Automated CET measurements appear to be unreliable in eyes with corneal scars in LSCD.

Efficacy of small incision lenticule extraction combined with femtosecond laser-assisted in situ keratomileusis for optimized monovision correction in myopia patients with presbyopia

Objective: To evaluate the efficacy of optimized monovision correction using small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in myopic patients with presbyopia and to assess the corneal epithelial remodeling following these procedures. Methods: A prospective study was conducted. Thirty-two patients (64 eyes) with myopia and presbyopia who underwent surgical correction at Chongqing Bai Ji Eye Clinic from August 2021 to April 2023 were continuously included. There were 9 males and 23 females, with an average age of (44.25±2.96) years. The dominant eyes (32 eyes) underwent SMILE, while the non-dominant eyes (32 eyes) underwent FS-LASIK with mild myopia and partial negative spherical aberration induction. Data on visual acuity and refraction were collected preoperatively and at 1 week, 1 month, 3 months, and 6 months postoperatively. Total ocular aberrations were measured using the iProfiler Plus, and the corneal epithelial thickness in different regions was assessed using anterior segment optical coherence tomography. Safety and efficacy indices were calculated based on visual acuity, the defocus and contrast sensitivity were measured using the Binoptometer 4P binocular vision tester, and a patient satisfaction survey was performed. Results: At 1 week postoperatively, the uncorrected distance visual acuity (UDVA) of dominant eyes significantly improved compared to preoperative values. At 3 months postoperatively, the uncorrected near visual acuity (UNVA) of non-dominant eyes showed significant improvement (P<0.05), 96.9% (31 eyes) of the dominant eyes achieved UDVA of 1.0 or better, and 93.8% (30 eyes) of the non-dominant eyes achieved UNVA of 0.8 or better. The safety index for distance vision was 1.15±0.09, and the efficacy index was 1.15±0.11. At 1 week, 1 month, 3 months, and 6 months postoperatively, the proportion of dominant eyes with a spherical equivalent (SE) deviation within ±0.50 D of the target was 90.6% (29 eyes), 90.6% (29 eyes), 93.8% (30 eyes), and 96.2% (31 eyes), respectively; for non-dominant eyes, the corresponding proportions were 81.3% (26 eyes), 87.5% (28 eyes), 93.8% (30 eyes), and 96.2% (31 eyes). The postoperative spherical aberration was (0.11±0.03) μm for dominant eyes and (-0.01±0.04) μm for non-dominant eyes, showing a statistically significant difference (P<0.05). At 1 week and 1 month postoperatively, the central corneal epithelial thickness of non-dominant eyes was significantly higher than that of dominant eyes [(71.34±21.69) μm vs. (51.97±6.33) μm at 1 week, and (61.34±15.85) μm vs. (52.72±6.32) μm at 1 month; P<0.05]. Patient satisfaction was high, with 96.9% (31 patients) rating their satisfaction as "satisfactory" or higher. Conclusions: The combined use of SMILE and FS-LASIK for optimized monovision correction in myopic patients with presbyopia is both safe and effective, achieving high postoperative satisfaction. The SMILE procedure reduces the extent of corneal epithelial remodeling compared to FS-LASIK.

Co-existence of Neurotrophic Keratopathy in Eyes With Limbal Stem Cell Deficiency

PurposeTo investigate whether neurotrophic keratopathy is present in limbal stem cell deficiency (LSCD) by measuring corneal sensation and characterizing corneal subbasal nerve plexus. DesignProspective, cross-sectional “case-control” comparative study. MethodsForty-six eyes with LSCD and 14 normal eyes were recruited from 2019 to 2022. Corneal sensation was measured using a Cochet-Bonnet esthesiometer and subbasal nerve plexus was imaged using in vivo confocal microscopy (IVCM) at the central cornea and 4 limbal regions. Subbasal nerve density (SND, number of nerve/mm2), subbasal nerve length (SNL, total length of nerve/mm2) and subbasal nerve branch density (SNBD, number of branch/mm2) were quantified. LSCD was graded to stage 1, 2 and 3 using a previously established staging method` consisting of clinical scores, basal cell density, central corneal epithelial thickness and SNL. ResultsThe mean (±SD) cornea sensation in the central cornea and limbus were 29.2 ± 21.5 and 33.6 ± 15.1 mm in the LSCD group and 57.6 ± 5.8 and 54.3 ± 4.7 mm in the control group, respectively (all P < 0.001). In sectoral LSCD, the sensation in the affected regions (29.1 ± 17.6 mm) decreased significantly compared to the unaffected regions (41.4 ± 18.2 mm, P < 0.001). Central corneal SND, SNL and SNBD were reduced by 84.6%, 82.6%, and 89.2%, respectively in LSCD compared to the control (all P < 0.05). The central corneal sensation negatively correlated with the severity of LSCD (rho = -0.64, P < 0.0001) and positively correlated with SND, SNL, and SNBD (rho=0.63, 0.66, and 0.56, respectively; all P < 0.001). ConclusionsCorneal sensation was reduced in eyes with LSCD. The degree of corneal sensation reduction positively correlated with the severity of LSCD. This finding demonstrated the co-existence of neurotropic keratopathy in LSCD.

Intraoperative variability of corneal epithelium thickness in photorefractive keratectomy

PurposeTo evaluate the intraoperative central corneal epithelial thickness (ET) as measured by optical coherence pachymetry (OCP) in myopic eyes undergoing alcohol-assisted photorefractive keratectomy (PRK).MethodsA retrospective review of patients who underwent alcohol-assisted PRK was performed. Data were abstracted on age, gender, contact lens (CL) wear, preoperative refractive errors, keratometry, topographic and ultrasonic pachymetry, and intraoperative OCP measurements before and after epithelium removal. The central ET was calculated by subtracting OCP measurement after epithelium removal from the OCP measurement prior to epithelium removal.ResultsThe study comprised of 162 consecutive eyes from 81 patients. Mean age was 26.73 ± 6.47 years, 50.6% were males. CL was used in 92 eyes (56.8%). The mean sphere and spherical equivalent were −3.60 ± 1.84 D and −3.26 ± 1.85D, respectively. The mean intraoperative ET was 58.22 ± 17.53 µm (range, 15–121µm). Fifty-five percent of the eyes had an ET measurement above or below the range of 40-60µm. ET was significantly higher in the second operated eye compared to the first operated eye (p = 0.006), and an association was found to CL-wear (p = 0.03). There was no significant difference in thickness between genders (p = 0.62), and no correlation to patient age (p = 0.45, rp = 0.06), refractive errors (p > 0.30,rp=−0.07–0.08), nor keratometry(p > 0.80, rp=−0.01− (−0.02)).ConclusionThe intraoperative assessment of ET in alcohol-assisted PRK showed a high variability of the central corneal epithelium, with a significant difference between the first and second operated eyes. This difference may have implications when the epithelium is not included in the surgical planning in surface ablation.

Corneal Epithelial Cell Density Is Reduced in Young Adults With Conjunctival Ultraviolet Autofluorescence.

The aim of this study was to investigate the effects of chronic ultraviolet (UV) radiation exposure on the corneal microstructure using conjunctival UV autofluorescence (CUVAF) as a marker of exposure. Young healthy adults aged 18 to 35 years were recruited. Participant's demographics and sun exposure behavior were recorded using questionnaires. Images of the bulbar conjunctiva from the right eye were captured and analyzed for the CUVAF area. Corneal microstructure was assessed by in vivo confocal microscopy and anterior segment optical coherence tomography. The presence of palisades of Vogt in all 4 limbal quadrants was recorded. CUVAF was observed in 31 of 52 eyes (60%), with a mean (±SD) nasal, temporal, and total CUVAF area of 5.39 ± 4.16 mm 2 , 4.29 ± 4.27 mm 2 , and 9.67 ± 7.01 mm 2 , respectively. Individuals with CUVAF were significantly more likely to report undertaking moderate-intensity to high-intensity outdoor exercise ( P = 0.021). Individuals with CUVAF were less likely to have visible nasal and temporal palisades of Vogt ( P = 0.011). Corneal basal cell densities anterior to the nerve whorl ( P < 0.001) and nasally ( P = 0.005) were lower in individuals with CUVAF. Wing cell density anterior to the nerve whorl was lower in individuals with CUVAF ( P = 0.011). No significant changes in the central and limbal corneal epithelial thickness were observed. Significant reductions in corneal epithelial cell density were observed in individuals with CUVAF, a biomarker of chronic UV exposure. This observation suggests that chronic UV exposure is damaging to the corneal microstructure.

The effect of sodium hyaluronate on dry eye and corneal epithelial thickness following cataract surgery.

To evaluate the effects of sodium hyaluronate drops on dry eye parameters and corneal epithelial thickness following cataract surgery. The study included 84 patients who underwent uncomplicated phacoemulsification. In Group A, 0.15% sodium hyaluronate drops were added to the postoperative antibiotic/anti-inflammatory treatment. In Group B, only antibiotic/anti-inflammatory treatment was applied. Preoperatively and at 1week and 1month postoperatively, all the patients were evaluated in respect of tear break-up time (TBUT), the Schirmer test under anesthesia, the corneal fluorescein staining (CFS) score, mean central corneal thickness (CCT) and mean central corneal epithelial thickness (CCET), and the two groups were compared. A statistically significant difference was determined between the two groups at postoperative 1month in respect of TBUT, Schirmer test, CFS score, and CCET (p < 0.01). In Group A, a statistically significant increase was determined in the TBUT and Schirmer values at 1month postoperatively (p < 0.01, p = 0.01, respectively) and in Group B, these values were decreased compared to preoperatively (p < 0.01). The CCET was determined to be significantly thinner in Group B 1month postoperatively (p < 0.01). A significant increase in CCT was observed in both groups at postoperative 1week (p < 0.01) and preoperative values were reached at 1month postoperatively. In the patient group using sodium hyaluronate, significant differences were determined in all dry eye parameters and CCET. The use of hyaluronate sodium drops after cataract surgery was seen to improve dry eye parameters and contribute to a healthy ocular surface by ensuring continuity of the corneal epithelium.

Uneven Corneal Epithelial Redistribution After Femtosecond Laser-Assisted Lenticule Intrastromal Keratoplasty in Correcting Moderate-to-High Hyperopia.

To evaluate the characteristic of corrective epithelial thickness after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) to correct moderate-to-high hyperopia. The prospective case series study of the LIKE procedure was performed to correct moderate-to-high hyperopia. The epithelial thickness map was generated by anterior segment optical coherence tomography (AS-OCT) in the corneal central 9-mm zone. Keratometry and corneal higher order aberrations were analyzed by Pentacam (Oculus Optikgeräte GmbH) preoperatively and postoperatively. In the 26 eyes of 13 participants who underwent the LIKE procedure for moderate-to-high hyperopia, the attempted spherical equivalence (SEQ) was +6.50 ± 1.09 diopters (D). Compared to the preoperative epithelial thickness maps, the postoperative epithelial thickness had become significantly thinner in the central 5-mm zone; the difference was 6 to 7 µm. The paracentral epithelium performed nonuniform remodeling; the thinnest epithelial thickness was located in the inferotemporal section, which has the greatest difference from the superonasal; the difference between these two was approximately 3 µm. Through correlation analysis, it was found that the sections with thinner epithelium were significantly related to corneal curvature and corneal vertical coma. The LIKE procedure can be used to correct moderate-to-high hyperopia. This study further indicated the epithelial remodeling characteristic after the LIKE procedure: the central and paracentral corneal epithelial thickness becomes thinner, and the epithelial thickness distributes non-uniformly, which may be the important factor of the postoperative curvature asymmetric distribution and induction of corneal vertical coma. [J Refract Surg. 2024;40(5):e321-e327.].

Comparison of focal loss volume, global loss volume, retinal nerve fiber layer thickness, and corneal epithelial thickness in eyes with glaucoma and suspicious optic discs

Abstract: PURPOSE: The purpose of this study was to study the role of the focal loss volume (FLV), global loss volume (GLV), and other spectral-domain optical coherence tomography (SD-OCT) parameters in early diagnosis of glaucomatous damage. METHODS: A retrospective study included records of 34 eyes with early glaucoma (Group A) and 17 eyes with suspicious optic discs (Group B). Retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and corneal thickness parameters were assessed by the SD OCT (RTVue SD-OCT). These included the FLV, GLV, in addition to RNFL thickness, cup/disc ratio, GCC thickness, and anterior segment OCT for assessment of central corneal thickness and central corneal epithelial thickness. Data from both groups were subjected to statistical analysis. RESULTS: The FLV and GLV had the highest areas under the receiver operating characteristic curve in Group A eyes. FLV had higher (97.2%) specificity and was the earliest parameter to be affected by glaucomatous damage, followed by GLV. Moreover, Group A eyes had significant thinning of the RNFL (91.59 μm) compared to Group B (118.18 μm), and GCC thickness was also significantly thinner in Group A (92.07 μm) than in Group B (110.54 μm). Interestingly, Group A eyes had thinner corneal epithelium (nonsignificant) than Group B. CONCLUSION: FLV and GLV were of the greatest value in the assessment of early glaucomatous GCC degeneration.

The association of pre-photorefractive keratectomy Schirmer-1 test value with postoperative corneal epithelial thickness, ocular surface discomfort, and visual acuity.

To investigate the association of pre-photorefractive keratectomy Schirmer-1 test value with post-photorefractive keratectomy central corneal epithelial thickness, ocular surface disease index score, and uncorrected distance visual acuity. Patients were categorized according to preoperative Schirmer-1 value: the normal Schirmer Group (n=54; Schirmer-1 test value, >10 mm) and the low Schirmer Group (n=52; Schirmer-1 test value, between 6 and 10 mm). We analyzed ablation depth, visual acuity, result of Schirmer-1 test (with anesthesia), tear film break-up time, ocular surface disease index score, central corneal epithelial thickness, and spherical equivalent refraction. We found significant differences between the groups in Schirmer-1 test value, tear film break-up time, and ocular surface disease index score, both preoperatively and postoperatively (p<0.001). The preoperative central corneal epithelial thicknesses of the two groups were similar (p>0.05). After photorefractive keratectomy, the Schirmer-1 test value and spherical equivalent refraction decreased in both groups (p<0.05), and ocular surface disease index scores and central corneal epithelial thickness values increased in the low Schirmer Group (p<0.001) but not in the normal Schirmer Group (p>0.05). The postoperative central corneal epithelial thicknesses of the low Schirmer Group were significantly higher than those of the normal Schirmer Group (p<0.001). Postoperative uncorrected distance visual acuity did not differ significantly between the two groups (p>0.05). In patients with low Schirmer-1 test values before photorefractive keratectomy, the corneal epithelium thickened and ocular surface complaints increased during the postoperative period. However, changes in the corneal epithelium did not affect the postoperative uncorrected distance visual acuity. To reduce postoperative problems on the ocular surface in these patients, we recommend that dry eye be treated before photorefractive keratectomy.

Assessment of corneal sublayer thickness changes in glaucoma patients using optical coherence tomography and correlation of epithelial layer thinning with dry eye monitoring

In this study, we aimed to assess the central corneal epithelial thickness (CET), central corneal stromal thickness (CST), and total central corneal thickness (CCT) thinning relationships with dry eye development monitoring and underestimated measurement of intraocular pressure (IOP) in primary open-angle glaucoma (POAG) patients treated with timolol, dorzolamide, and brimonidine. This longitudinal cohort study included 106 patients with POAG. All patients underwent a detailed ophthalmic examination. In addition, CET, CST, and CCT were measured using anterior segment optical coherence tomography (AS-OCT). Subsequently, the cohort was divided into three groups based on the therapy administered. The Tomec group received monotherapy with benzalkonium chloride (BAK)-preserved timolol+dorzolamide fixed combination. The Alphagan group received monotherapy with purite-preserved brimonidine, and the Combigan group received monotherapy with BAK-preserved timolol+brimonidine fixed combination. CET, CST, and CCT did not show a statistically significant decrease in the Alphagan group (p>0.05). However, the Tomec and Combigan groups showed significantly reduced measurements, except for stromal thickness (p<0.05). Finally, a significant positive correlation was found between changes in tear break-up time (TBUT) and CET during the follow-up period (r=0.637, p=0.001). CET and CCT thinning were higher in the Tomec and Combigan groups than in the Alphagan group. Furthermore, although CCT reduction was significant in the Tomec and Combigan groups, its effect on IOP underestimation was approximately 1%. Furthermore, the positive correlation between CET and TBUT suggests that CET measurement with AS-OCT may also be useful in dry eye monitoring.

Evaluation of Limbal Stem Cells in Patients With Type 2 Diabetes: An In Vivo Confocal Microscopy Study.

This study aimed to investigate corneal limbus changes in patients with type 2 diabetes mellitus (DM) using in vivo confocal microscopy (IVCM) and explore the correlation between their ocular manifestations and systemic status. Fifty-five patients with type 2 DM and 20 age-matched controls were included. The following IVCM parameters were compared between the 2 groups: palisades of Vogt (POV), corneal epithelial thickness (CET), basal cell density (BCD), subbasal nerve plexus, and dendritic cell density. All subjects underwent blood and urine sampling for laboratory analysis, including fasting blood glucose, glycated hemoglobin, total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein, urinary albumin-to-creatinine ratio, urine albumin, and urine creatinine. The correlations between IVCM parameters and blood biomarkers were detected. Receiver operating characteristic curve was used for selecting the cutoff value of risk factors for corneal stem cell injury in patients with DM. Compared with controls, patients with DM displayed a significant reduction of POV (superior region, P = 0.033; inferior region, P = 0.003; nasal region, P < 0.001; temporal region, P < 0.001), central CET (44.8 ± 3.6 μm vs. 51.9 ± 3.6 μm, P < 0.001), central corneal BCD (7415.5 ± 563.2 cells/mm 2 vs. 9177.9 ± 977.8 cells/mm 2 , P < 0.001), and peripheral corneal BCD (6181.3 ± 416.5 cells/mm 2 vs. 8576.3 ± 933.2 cells/mm 2 , P < 0.001). Dendritic cell density (41.0 ± 33.7 cells/mm 2 vs. 24.6 ± 7.8 cells/mm 2 , P = 0.001) was significantly higher in the DM group. The following weak correlations were shown between IVCM parameters and blood biomarkers: central corneal BCD was negatively correlated with DM duration (r = -0.3, P = 0.024), TC (r = -0.36, P = 0.007), and LDL (r = -0.39, P = 0.004). The presence of POV in the superior region was negatively correlated with TC (r = -0.34, P = 0.011) and LDL (r = -0.31, P = 0.022). Cutoff values of 1.215 mmol/L for HDL, 1.59 mmol/L for TG, or 4.75 mmol/L for TC were established to distinguish patients with a high risk from a low risk for stem cell damage. Patients with type 2 DM displayed a lower positive rate of typical POV and a decrease in BCD, CET, and subbasal nerve density. The most relevant indicators for stem cell phenotypes were DM duration, TC, and LDL. Lipid status in diabetic patients could be a predictor of risk for developing corneal limbal stem cell deficiency. Further studies with larger sample sizes or basic research are needed to verify the results.

Does corneal epithelial thickness show the severity of psoriasis? SD-OCT study

BackgroundPrevious studies have generally focused on dry eye test abnormalities and ocular involvements such as uveitis, and blepharitis in psoriasis. Psoriasis area severity ındex (PASI), which is used to assess psoriasis severity, is a time-consuming and complex tool. ObjectiveTo evaluate the relationship between disease severity and central corneal epithelial thickness (CCET) in psoriasis. Methods175 eyes of 175 psoriasis patients and 57 eyes of 57 healthy individuals as a control group was included in this study. Psoriasis patients were divided into three subgroups according to PASI score as < 10 mild, 10‒20 moderate and > 20 severe. CCET was measured by spectral domain-optical coherence tomography (SD-OCT), and mean values were recorded. Mean CCET values were compared between the psoriasis groups and the control group. Additionally, the relationship between PASI score and CCET was examined. ResultsThe mean CCET value was 58.06±3.1μm in the mild group, 60.10±5.0μm in the moderate group, 65.75±6.3μm in the severe group and 56.16±3.1μm in the control group. It was determined that the mean CCET value was significantly higher in all psoriasis groups compared to the control group (p<0.001). The mean CCET value was significantly higher in the moderate psoriasis group than in the mild psoriasis group (p=0.018), and in the severe psoriasis group compared to the moderate psoriasis group (p<0.001). There was a strong positive correlation between PASI score and CCET (p<0.001, r=0.519). Study limitationsCross-sectional design and a relatively small number of participants. ConclusionsThere is a strong positive correlation between psoriasis severity and CCET. Contactless measurement of CCET by SD-OCT can be an indicator of psoriasis severity.

The diagnosis and treatment of contact lens-induced limbal stem cell deficiency

Objective: To analyze the clinical features and treatment outcomes of eyes with contact lens-induced limbal stem cell deficiency (CL-iLSCD). Methods: This cross-sectional study involved patients diagnosed with CL-iLSCD at the Eye, Ear, Nose & Throat Hospital of Fudan University between October 2018 and September 2022. A total of 17 patients (25 eyes) with a mean age of (36.4±6.9) years were enrolled. Among them, 14 were females (82.4%). Corneal and limbal abnormalities, especially the range of epitheliopathy, were observed under a slit lamp biomicroscope with fluorescein staining. Anterior segment optical coherence tomography and in vivo laser scanning confocal microscopy were performed to obtain the central corneal epithelial thickness, density of basal epithelial cells and corneal nerve fiber length. The clinical features of CL-iLSCD, along with their treatment outcomes and related risk factors, were analyzed. Results: All patients wore soft contact lenses, with an average daily wearing time of (10.5±2.5) hours and a median wearing duration of 10 (4 to 30) years. Ocular symptoms, including decreased vision, ocular discomfort or pain, redness, and photophobia, were present in 22 eyes (88.0%). The most characteristic clinical sign of CL-iLSCD was comb-or whorl-pattern late fluorescein staining under cobalt blue light, which was most commonly seen at the superior limbus (25/25, 100.0%). Additionally, reductions in central corneal epithelial thickness, basal cell density, and corneal nerve fiber length were observed. A comprehensive score was assigned to each eye based on clinical findings and in vivo imaging biomarkers. LSCD was mild, moderate, and severe in 5, 11, and 8 eyes, respectively. A history of misdiagnosis was found in 20 eyes (80.0%). After discontinuing the use of contact lenses and receiving medical treatment, significant improvement was observed in all eyes, with 13 eyes fully recovered. Conclusions: The symptoms and clinical signs of CL-iLSCD can be subtle at the early stage. Discontinuing contact lens wear and medication are effective to treat CL-iLSCD.

Investigation of corneal epithelial thickness and irregularity by optical coherence tomography after transepithelial photorefractive keratectomy

ABSTRACT Clinical relevance Corneal epithelial healing after refractive surgery is a clinically significant issue, especially for surface ablation procedures, and this can be monitored using optical coherence tomography (OCT). Background The aim of this work is to investigate the corneal epithelial thickness and irregularity by OCT after transepithelial photorefractive keratectomy (t-PRK) and analyse its correlation with visual and refractive outcomes. Methods Patients aged ≥18 years with myopia, with or without astigmatism, who underwent t-PRK between May 2020 and August 2021 were included. All participants were subjected to complete ophthalmic examinations and OCT pachymetry at every follow-up visit. Patients were followed up at 1 week and 1, 3, and 6 months postoperatively. Results A total of 67 patients (126 eyes) were enrolled in this study. One month postoperatively, spherical equivalent refraction and visual acuity achieved preliminary stability. However, central corneal epithelial thickness (CCET) and standard deviation of the corneal epithelial thickness (SDcet) took 3–6 months to progressive recovery. Patients with higher baseline spherical equivalent refraction were associated with slower epithelial recovery. At every follow-up time point, a significant superior-inferior difference in the minimum corneal epithelial thickness area was observed. Higher stromal haze was correlated with higher spherical equivalent refraction (both baseline and residual) but had no relation with visual outcomes. There was a significant correlation between higher CCET with a better uncorrected distance visual acuity and lower corneal epithelial thickness irregularity. Conclusions CCET and SDcet measured by OCT seem to be a good auxiliary indicator for reflecting the status of corneal wound recovery after t-PRK surgery. However, a well-designed randomised control study is needed to confirm the study results.

Effects of topical prostaglandin therapy on corneal layers thickness in primary open-angle glaucoma patients using anterior segment optical coherence tomography.

To evaluate the effects of latanoprost, bimatoprost, and travoprost eye drops and their preservatives on each corneal layer thickness in patients with primary open-angle glaucoma (POAG). We retrospectively analyzed 79 eyes of 79 patients with POAG who were receiving prostaglandin therapy. Patients were divided into three subgroups according to monotherapy with latanoprost, bimatoprost, and travoprost during a mean of 43.14 ± 19.12months follow-up period. In addition, the central corneal epithelial thickness (CET), central corneal stromal thickness (CST), and total central corneal thickness (CCT) were measured by anterior segment optical coherence tomography (AS-OCT) at baseline and every six months after treatment initiation at each visit between 9 and 12 o'clock in the morning. Furthermore, intraocular pressure (IOP) was measured with Goldmann applanation tonometry (GAT) after AS-OCT measurements at each visit. All three groups were not significantly different in age, gender, follow-up period, and mean intraocular pressure values (p > 0.05 for all). The reduction of CCT in the latanoprost, bimatoprost, and travoprost groups was 6.53 ± 3.17, 18.59 ± 8.42, and 10.1 ± 1.13µm, respectively. The decrease in CST values was 4.65 ± 1.54, 15.84 ± 7.47, 9.69 ± 1.45µm, and CET values were 1.88 ± 1.66, 2.75 ± 0.73, 0.41 ± 0.54µm in all groups, respectively. A statistically significant thinning was observed in all corneal layers (p < 0.05) except the CST values in the latanoprost group and CET values in the travoprost group. However, no significant difference was found in the average reduction of CET, CST, and CCT values among the three groups (p > 0.05). Topical treatment with latanoprost, bimatoprost, and travoprost affects each layer of the cornea separately according to the active and protective substances contained in these eye drops. On the other hand, the thinning effect on the corneal layers was similar in these three drugs because there was no significant difference between the three groups in the total amount of thinning of the corneal layers during the follow-up period.

Transpalpebral intraocular pressure measured by Diaton tonometer before, 1 week, and 1 month after transepithelial photorefractive keratectomy in young myopic Saudi patients and its determinants.

To present changes in transpalpebral intraocular pressure (tpIOP) in eyes after transepithelial photorefractive keratectomy (TPRK) in myopic Saudi patients and its determinants. This one-armed cohort included the myopic eyes of Saudi adolescents treated with TPRK in 2020-2021. The difference in tpIOP before surgery, 1 week after surgery, and 1 month after surgery using Diaton was the main outcome. Central corneal thickness (CCT), myopia grade, gender, age, and corneal epithelial thickness before surgery were independent factors. Matched-pair analysis was conducted. The determinants of tpIOP post-TPRK were studied. Our cohort included 193 eyes of 97 participants (25.6 ± 5.8 years). Mild, moderate, and severe myopia were present in 93, 79, and 21 eyes, respectively. tpIOP was 22 mmHg or more in 5 and 8 eyes at 1-week and 1-month follow-up, respectively. The change in tpIOP ranged from - 7.00 to + 11.0 mmHg at 1 week and - 8.0 to + 26.0 mmHg at 1 month. The median change of CCT at 1 month was 59 μ. Change in tpIOP was not correlated with change in CCT at 1 month (r = -0.107, Pearson P = 0.14). Change of tpIOP was significantly correlated to spherical equivalent (SE) before surgery (matched-pair P < 0.001). SE (Mann-Whitney U P = 0.02) and tpIOP (Mann-Whitney U P = 0.02) before TPRK were significantly correlated to tpIOP >22 mmHg after TPRK. The changes in tpIOP following refractive surgery correlate to the refractive status of the eye and tpIOP before surgery.

Transepithelial Corneal Cross-linking with Supplemental Oxygen in Keratoconus Treatment - Corneal Stromal Demarcation Line and Safety

Purpose: To evaluate the corneal stromal demarcation line and safety of transepithelial corneal cross-linking (CXL) with supplemental oxygen in progressive keratoconus treatment. Methods: This is a retrospective review of 25 patients with progressive keratoconus who underwent epithelial-on CXL with supplemental oxygen from December 2019 to February 2022. Outcomes measured include corneal stromal demarcation line depth, volume of cornea treated, endothelial cell count, best-corrected visual acuity, keratometric parameters and post-treatment adverse events. Results: 25 eyes of 25 patients were included and mean age was 28.3 years. Mean follow-up period was 11.5 ± 1.39 months. Pre-operatively, mean ± standard deviation (SD) of K1, K2, Kmax and minimal corneal thickness were 45.9D ± 3.79D, 50.2D ± 4.83D, 57.5D ± 6.98D and 482.3um ± 36.8um respectively. There is no significant difference between pre and post-treatment corneal topographic parameters. There was improvement in BCVA post-treatment. The mean post-treatment corneal stromal demarcation line depth was 367.3 ± 89.8um. The volume of treated cornea including the central corneal epithelial thickness was 73.3 ± 4.39%. There was no reduction in endothelial cell count (ECC) post-procedure (pre-treatment mean ECC±SD: 2695.4 ± 224.5 cells/mm2, post-treatment ECC 2730.1 ± 252.0 cells/mm2, p-value = 0.33). Post-treatment corneal haze was mild and seen in 8 patients postoperatively. One patient developed a non-visual axis involving stromal infiltrate that resolved with topical broad-spectrum anti-microbials. Conclusion: Trans-epithelial CXL with supplemental oxygen for keratoconus treatment achieved comparable corneal stromal demarcation line depth comparable to that of conventional epithelial-off corneal cross-linking and had a similar safety profile.

Corneal epithelial remodeling after femtosecond laser-assisted in situ keratomileusis combined with intraoperative accelerated corneal collagen crosslinking for myopia: a retrospective study

BackgroundThis study analyzed regional corneal thickness remodeling, biomechanical properties, and visual outcomes after femtosecond laser-assisted in situ keratomileusis combined with intraoperative accelerated corneal collagen crosslinking (LASIK Xtra) for myopia.MethodsThis retrospective study analyzed 21 consecutive patients (18 women, three men; 42 eyes) who were treated with LASIK Xtra. All treatments were performed with ultraviolet-A (energy, 2.7 J/cm2; irradiance, 30 mW/cm2), using continuous (90 s) illumination. Postoperative values of corneal biometrics and visual outcomes were compared with preoperative values. Corneal thickness changes were evaluated using anterior segment optical coherence tomography. All patients were followed up for 12-month postoperatively. Preoperative and postoperative data were compared statistically using the paired t-test for normally distributed parameters and the Wilcoxon rank-sum test and Friedman analysis of variance with Bonferroni correction for non-normally distributed data.ResultsUncorrected distance visual acuity (UDVA) significantly improved at 6-month after surgery (P < 0.001). The central and inner regional corneal epithelial thickness significantly increased after LASIK Xtra (P < 0.05 for all), while the peripheral corneal epithelial thickness remained stable at 12-month after surgery. There was also a statistically significant decreased in the stromal thickness at most locations (P < 0.05 for all), except in the outer superior and outer superior-temporal regions.ConclusionsLASIK Xtra provided improvement in UDVA, corneal curvature, and corneal biomechanical stability. Because the results of this retrospective study results depended on the cohort members’ past information, it was inferred and confirmed that regular corneal thickness remodeling occurred after treatment.

Evaluation of central corneal epithelial thickness with anterior segment OCT in patients with type 2 diabetes mellitus.

This study aimed to evaluate the central corneal thickness (CCT) and central corneal epithelial thickness (CCET) in patients with Type 2 diabetes mellitus (DM), and the effect of the duration of diabetes, the degree of diabetic retinopathy (DR), and HbA1c level. CCT and CCET values of 72 patients diagnosed with type 2 DM and 72 healthy individuals were measured by anterior segment optical coherence tomography. The eye tear function was evaluated with the Tear Break-up Time test (TBUT) and the Schirmer test. From the results of fundus examination, the diabetic patients were grouped as those without DR, non-proliferative DR, and proliferative DR. The disease duration and the HbA1c levels were recorded. In the diabetic patients, the mean CCT was determined to be thicker (p = 0.025), the CCET was thinner (p = 0.003), and the TBUT and Schirmer values were lower (p<0.001, p<0.001, respectively). The duration of diabetes and the HbA1c level was not found to have any statistically significant effect on these parameters (p>0.05). The presence of retinopathy had no significant effect on CCT, TBUT, and Schirmer values. The CCET was determined to be thinner in patients with retinopathy (p<0.001). As the corneal epithelial thickness is reduced in patients with advanced diabetic retinopathy, corneal epithelial pathologies can be seen more often. Therefore, early and effective treatment can be started by taking into consideration the complications which may develop associated with the corneal epithelium following surgical procedures, especially those applied to the cornea.

An Evaluation of Central Corneal Epithelial Thickness and Central Corneal Thickness Determined On Optic Coherence Tomography Before and After Applanation Tonometry

Objective: To determine the changes in corneal epithelial thickness and central corneal thickness using optic coherence tomography taken after Goldmann applanation tonometry measurements. Material and Methods: The study included 25 patients who presented at our clinic for routine ophthalmological examination. Before taking tonometry measurements of the patients, epithelial corneal thickness and central corneal thickness values were determined using optic cohence tomography (OCT). The intraocular pressure (IOP) was measured with tonometry and then the corneal OCT measurements were repeated. All the OCT and tonometry measurements were taken by the same clinician. Results: Evaluation was made of 25 patients comprising 18 males and 7 females with a mean age of 36.6 years (range, 17-55 years). The mean epithelial corneal thickness was 52.58 microns before the applanation tonometry measurement, and 52.02 microns after the tonometry (p=0.059). Central corneal thickness was measured as mean 530.96 microns before tonometry and 529.88 microns after (p&amp;gt;0.05). No statistically significant difference was determined in the changes of both measurements. Following tonometry, a change was seen in corneal epithelial thickness, but not of a statistically significant level (p=0.059). Conclusion: The study results showed no statistically significant difference in the measurements of corneal epithelial thickness and central corneal thickness following applanation tonometry. Although not statistically significant, the difference seen in thickness indicates desquamation in the epithelial cells as a result of the procedure. This may cause complaints such as a reduction in visual acuity and the feeling of burning or pricking in the eye. If glasses are to be prescribed for patients, this should be taken into consideration and the examination should be made before the tonometry measurement. To the best of our knowledge, there has been no previous study in literature of central corneal epithelial thickness measured before and after tonometry, and therefore the results obtained in this study are the first on this subject.