Thin Corneas Research Articles

Efficacy and Safety of Contact Lens-Assisted Corneal Crosslinking in the Treatment of Keratoconus With Thin Corneas.

To evaluate the safety and efficacy of contact lens-assisted crosslinking (CA-CXL) in progressive keratoconus with thin corneas (350-400 µm). Forty eyes (30 patients) underwent epithelium-off CA-CXL with iso-osmolar riboflavin and ultraviolet-A irradiation for 30 min (fluence, 3 mW/cm2). A non-ultra-violet-absorbing soft contact lens (sCL) soaked in riboflavin was applied over the cornea during irradiation. Demarcation line (DL) depth was measured 1 month postoperatively. Endothelial cell count (ECC) was measured preoperatively and 3 months postoperatively. Distance uncorrected visual acuity (UDVA) and best spectacle-corrected visual acuity (BDVA), and maximum keratometric values (K max) were evaluated preoperatively and 9 months postoperatively. The sCL added a mean thickness of 100.05±1.23 µm. The mean ECC was 2,982±165 cell/mm2 preoperatively and 2,955±125 cell/mm2 postoperatively (endothelial cell loss, 0.9%, P=0.21). The mean DL depth was 204.8±20.2 µm. There was significant improvement in UDVA (P<0.001) and BDVA (P=0.011) with a stable K max (P=0.06). Contact lens-assisted crosslinking was safe and effective, with endothelial loss less than 1% after 3 months and stable corneal tomography over 9 months, with improved visual acuity. Demarcation line depth was found to be shallower than conventional CXL. Therefore, the long-term efficacy of CA-CXL requires further study. NCT04504578 Clinical trials.gov.

Endothelial cell loss after accelerated corneal crosslinking using pachymetry-guided hypo-osmolar riboflavin dosing in thin keratoconic corneas.

To report the intraoperative changes in corneal pachymetry, as well as the efficacy and safety of accelerated corneal crosslinking (A-CXL) treatment using only hypo-osmolar riboflavin (HO-RF) solution in progressive keratoconus patients with thin corneas. University of Health Sciences, Prof. Dr. Cemil Tascioglu Education and Research Hospital, Istanbul, Turkey. Retrospective study. Thin keratoconic corneas (<400 m without epithelium) who had A-CXL (9 mW/cm2-10 minutes) with HO-RF solution application were enrolled in the study. Intraoperative corneal pachymetric changes and uncorrected and corrected distance visual acuities (UDVA and CDVA), refraction power values, topographic values, and endothelial cell density (ECD) measurements were recorded preoperatively and at 1st, 3rd, 6th, and 12th month follow-up postoperatively. 31 eyes of 25 patients (mean age: 24.17 ± 3.07 years) included in this study. The mean thickness increased to 438 μm (P = .001) after the application of HO-RF solution, and it was reduced to 424 μm (P = .001) after ultraviolet irradiation. At all postoperative visits after month 1, there was a significant increase in both UDVA (P < .05) and CDVA (P < .01) values and a significant decrease in both maximum keratometry (P < .05) and ECD (P < .01) values. Accelerated CXL with only HO-RF solution application throughout the procedure in thin corneas was effective but seemed to result in a significant ECD decrease postoperatively.

Comparison of corneal biomechanics among primary open-angle glaucoma with normal tension or hypertension and controls.

Background:Normal tension glaucoma (NTG) is a less pressure-dependent type of glaucoma with characteristic optic neuropathy. Recently, the biomechanical mechanism has been thought to account for glaucomatous optic neuropathy to some degree. We intended to compare dynamic corneal response parameters (DCRs) among patients with primary open-angle glaucoma with normal tension or hypertension and controls. The correlations between DCRs and known risk factors for glaucoma were also analyzed.Methods:In this cross-sectional study, 49 NTG subjects, 45 hypertension glaucoma (HTG) subjects, and 50 control subjects were enrolled. We compared the differences in DCRs using corneal visualization Scheimpflug technology among the NTG, HTG, and control groups. We also analyzed the correlations between DCRs and known risk factors for glaucoma (eg, central corneal thickness [CCT], intraocular pressure [IOP], etc).Results:The maximum inverse concave radius (NTG: 0.18 [0.17, 0.20] mm−1; control: 0.17 [0.16, 0.18] mm−1; P = 0.033), deformation amplitude ratio of 2 mm (DAR 2 mm, NTG: 4.87 [4.33, 5.39]; control: 4.37 [4.07, 4.88]; P < 0.001), and DAR 1 mm (NTG: 1.62 [1.58, 1.65]; control: 1.58 [1.54, 1.61]; P < 0.001) were significantly higher in NTG than in the controls. The integrated radius (IR, NTG: 8.40 ± 1.07 mm−1; HTG: 7.64 ± 1.31 mm−1; P = 0.026) and DAR 2 mm (NTG: 4.87 [4.33, 5.39]; HTG: 4.44 [4.12, 5.02]; P < 0.007) were significantly higher, whereas the stiffness parameter at the first applanation (SP-A1, NTG: 91.23 [77.45, 107.45]; HTG: 102.36 [85.77, 125.12]; P = 0.007) was lower in NTG than in HTG. There were no significant differences in the DCRs between HTG and control groups (P > 0.05). In the univariate and multivariate analyses, some of the DCRs, such as IR, were negatively correlated with CCT and IOP, whereas SP-A1 was positively correlated with CCT and IOP.Conclusions:The cornea was more deformable in NTG than in HTG or controls. There were no significant differences in corneal deformability between HTG and controls. The cornea was more deformable with the thinner cornea and lower IOP.

Goldmann Tonometry and Corneal Biomechanics

Glaucoma is the second cause of irreversible blindness in the world. Intraocular pressure (IOP) is a recognized major risk factor for the development and progression of glaucomatous damage. Goldmann applanation tonometry (GAT) is internationally accepted as the gold standard for the measurement of IOP. The purpose of this study was to search for correlations between Goldmann tonometry and corneal mechanical properties and thickness by means of in vitro tests. IOP was measured by the Goldmann applanation tonometer (GIOP), and by a pressure transducer inserted in the anterior chamber of the eye (TIOP), at increasing pressure levels by addition of saline solution in the anterior chamber of enucleated pig eyes (n = 49). Mechanical properties were also determined by inflation tests. The GAT underestimated the real measurements made by the pressure transducer, with most common differences in the range 15–28 mmHg. The difference between the two instruments, highlighted by the Bland–Altman test, was confirmed by ANOVA, normality tests, and Mann–Whitney’s tests, both on the data arranged for infusions and for the data organized by pressure ranges. Pearson correlation tests revealed a negative correlation between (TIOP-GIOP) and both corneal stiffness and corneal thickness. In conclusion, data obtained showed a discrepancy between GIOP and TIOP more evident for softer and thinner corneas, that is very important for glaucoma detection.

A Novel Approach to Enhancement Linked Laser Asymmetric Keratectomy Using Semi-Cylindrical Ablation Pattern in Patients with Myopic Regression After Laser Refractive Surgery.

PurposeWe aimed to introduce a new technique to reduce regional asymmetry of corneal thickness by assessing its effectiveness in four patients with myopic regression after laser refractive surgery (LRS).Patients and MethodsFour patients (four eyes) with myopic regression after LRS were included in this study. A new technique of enhancement with laser epithelial keratomileusis-linked laser asymmetric keratectomy using semi-cylindrical ablation pattern (E-LAK-SCAP) with full integration of the Vision-Up software for analyzing the corneal thickness deviation can be used to create central symmetry by blocking laser ablation on the thin cornea. It reduces the regional asymmetry of the corneal thickness, thus improving corneal symmetry and correcting the refractive power and myopic shift due to E-LAK-SCAP. We measured refraction, visual acuity, intraocular pressure (IOP), central corneal thickness (CCT), corneal irregularities in the 3.0mm, and 5.0 zones on Orbscan maps, the sum of corneal thickness deviations in four directions (SUM), distance between the maximum posterior elevation (best-fit-sphere [BFS]) and the visual axis (DISTANCE), and angle kappa before and after LRS and E-LAK-SCAP. Blurring scores were measured before and after E-LAK-SCAP.ResultsThe uncorrected far visual acuity (LogMAR) increased after LRS and E-LAK-SCAP. SUM (µm) increased after LRS in three cases, but decreased in all four cases after E-LAK-SCAP. DISTANCE increased after LRS, but decreased after E-LAK-SCAP. The spherical equivalent, CCT, decreased after LRS and E-LAK-SCAP. Blurring scores decreased after E-LAK-SCAP, and angle kappa was similar before and after LRS, but decreased after E-LAK-SCAP. IOP was similar before and after both LRS and E-LAK-SCAP.ConclusionE-LAK-SCAP improved corneal symmetry by reducing the SUM and DISTANCE, showing good postoperative visual acuity, and blurring was reduced postoperatively. There was no myopic regression in the one-year postoperative period.

Comparative study on corneal cross-linking with isotonic and hypotonic riboflavin: can hypotonic riboflavin be applied in thinner corneas?

AIM: To compare the results of corneal cross-linking (CXL) with isotonic (IR) and hypotonic riboflavin (HR) in patients with keratoconus and to verify the efficacy of keratoconus in thinner corneas. METHODS: Retrospective study of 29 eyes/keratoconus patients submitted to CXL, 15 eyes with application of IR (IR group) and 14 eyes with application of HR (HR group). The parameters analysed included (1-year follow-up): best corrected visual acuity (BCVA), sphere and cylinder, central and finer pachymetry, mean and maximum keratometry (Km and Kmax respectively), complications and progression. RESULTS: An increase on the BCVA scale (logMAR, logarithm of the minimal angle of resolution) was observed in the two groups: 0.26±0.57 (IR) and 0.47±0.72 (HR) before treatment, and 0.13±0.79 (IR) and 0.29±1.52 (HR) at the 1y. Only at 1y, the difference was statistically significant (P=0.018, group IR with higher BCVA). The central pachymetry (μm) decreased at 1mo in both groups, and increased in the following months: 497±28 μm (IR) and 432±14 μm (HR) before treatment, and 480±31 μm (IR) and 424±15 μm (HR) to the 1y. The thinner pachymetry (μm) presented the same evolution: 487±29 μm (IR) and 410±20 μm (HR) before treatment, and 468±33 μm (IR) and 413±13μm (HR) at 1y. Km and Kmax decreased in both groups (P&gt;0.05). Six eyes from each group presented transitory haze. No eye progressed to the 1y. CONCLUSION: The use of hypotonic riboflavin seems to be a valid alternative for performing the traditional corneal cross-linking technique in eyes with a central corneal thickness of &lt;400 μm.

Prophylactic Corneal Cross-Linking in Myopic Femtosecond Laser-Assisted In Situ Keratomileusis: Long-Term Visual and Refractive Outcomes

The purpose of our study was to evaluate the safety, effectiveness, predictability, and stability of myopic and astigmatic laser-assisted in situ keratomileusis (LASIK) with simultaneous prophylactic corneal cross-linking (CXL) in thin corneas. In total, 100 eyes from 50 patients who were subjected to myopic and astigmatism femtosecond LASIK with simultaneous prophylactic CXL were included. The design of the study was retrospective, longitudinal, and observational. All patients had a 48-month follow-up. The MEL 80 excimer laser was utilized with the Aberration Smart Ablation platform. CXL treatment was applied when the predicted stromal thickness was less than 330 µm. Patients’ mean age was 30.22 ± 5.97 years. Previous mean spherical equivalent was −5.50 ± 1.65 (−9.50 to −1.13) diopters (D). Postoperative mean spherical equivalent was −0.24 ± 0.29 (−0.85 to +0.50) D. Visual acuity (VA) of 20/20 or better was observed in 87% of the eyes and no eyes experienced VA loss. Spherical equivalent within ±0.50 D was observed in 93% of eyes, and 4% of eyes varied by 0.50 D or more between 3 and 48 months. Prophylactic corneal cross-linking with simultaneous femtosecond laser-assisted in situ keratomileusis in thin corneas proved to be effective, safe, and predictable. The results remained stable after 48 months of follow-up.

Corneal Tomographic Analysis Among Patients With Thyroid Gland Dysfunction.

To analyze the corneal tomographic parameters of patients with thyroid gland dysfunction. This case-control study included 100 eyes of 50 patients with thyroid gland dysfunction and 100 eyes of 50 healthy controls. All eyes were examined by Pentacam (Oculus Optikgeräte GmbH). Pentacam parameters were compared between patients with thyroid gland dysfunction and controls. Spearman's correlation coefficient between different Pentacam parameters and the serum level of free thyroxin (T4) and thyroid-stimulating hormone (TSH) was calculated. Patients with hypothyroidism had significantly higher median values of steep and maximum simulated keratometric readings, central corneal thickness (CCT), and thinnest pachymetry (CTmin) than both patients with hyperthyroidism and controls (P⩽ .05). The median values of the average and maximum pachymetric progression index (PPI), posterior elevation, and back difference elevation were significantly higher in patients with hyperthyroidism than in patients with hypothyroidism and controls (P ⩽ .05). The Ambrósio Relational Thickness (ARTmax) was significantly reduced in patients with hyperthyroidism (P ⩽ .001). Both CCT and CTmin showed a moderately positive correlation with serum TSH level and a moderately negative correlation with serum free T4 level. Patients with non-autoimmune thyroid gland dysfunction had significantly thinner CCT, CTmin, and inferior vertical deviation than the autoimmune group (P ⩽ .05). Thyroid gland dysfunction is associated with significant corneal tomographic changes. Patients with hyperthyroidism tend to have thinner corneas and more abnormal tomographic parameters correlating with keratoconus. No significant tomographic changes were found in association with autoimmune thyroid gland dysfunction. The authors recommend screening and regular follow-up of patients with thyroid gland dysfunction for early detection and management of keratoconus. [J Refract Surg. 2021;37(3):192-197.].

Femtosecond laser-assisted stromal keratophakia for keratoconus: A systemic review and meta-analysis

Femtosecond lasers have revived the possibility of stromal keratophakia or tissue additive keratoplasty, a technique originally introduced by Prof. Jose Ignacio Barraquer in the 1960s. The surgical technique offers a unique solution to treat keratoconus. In the current study, we reviewed and performed a meta-analysis of the clinical outcomes of the femtosecond laser-assisted stromal keratophakia in the treatment of keratoconus. This is a systematic review and meta-analysis of the estimated outcome difference between pre- and post-lenticule implantations. A total of related 10 studies were found in the literature. No studies reported adverse events, such as persistent haze or graft rejection, at last patients' visits. We further narrowed down the article selection in accordance to our inclusion criteria to report the composite outcomes (9 studies) and meta-analysis (4 studies). In the composite analysis, we demonstrated that lenticule implantation in keratoconus and post-LASIK ectasia patients appeared to expand the stromal volume of the thin corneas, flattened the cones, and significantly improved uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalent (SE). The meta-analysis showed that the random estimated UCVA, BCVA, SE and mean keratometry (Km) differences following the lenticule implantation was -0.214 (95% CI: -0.367 to 0.060; p = 0.006), -0.169 (-0.246 to 0.091; p < 0.001), -2.294 D (-3.750 to -0.839 D; p = 0.002), and 2.909 D (0.805 to 5.012 D; p = 0.007), respectively. Femtosecond laser-assisted stromal keratophakia is a feasible technique to correct the refractive aberrations, expand corneal volume and regularize corneal curvature in patients with keratoconus. However, there is a need to standardize the technique (e.g., whether to crosslink or not or to use convex or concave lenticules) and to formulate a mathematical model that accounts for the long-term epithelial thickness changes and stromal remodeling to determine the shape or profile of the lenticules, in order to improve the efficacy of the keratophakia further.

Predictive Factors for Corneal Scarring in Progressive Keratoconus Patients after Corneal Collagen Cross-linking

ABSTRACT Objectives : To evaluate predictive factors for corneal scar formation following corneal collagen cross-linking (CXL). Methods : The medical records of 295 progressive keratoconus patients who had undergone accelerated CXL were reviewed retrospectively in this comparative cohort study. Thirty-two eyes of 32 patients who still had a corneal scar in the first year (scar group) and 75 eyes of 75 patients without any scar (control group) were included. The patients’ demographic characteristics, preoperative uncorrected distance visual acuity (UCVA) and corrected distance visual acuity (CDVA), slit-lamp biomicroscopy and corneal topographic parameters data were acquired from the patients’ files. Multivariable logistic regression analysis and Receiver operating characteristic (ROC) curves were used for the purpose of evaluating predictive factors for corneal scar formation. Results : The UCVA and CDVA, which were determined to be similar between the groups during the preoperative period (P = .63, P = .71, respectively), improved postoperatively in both groups (P = .98, p = .10, respectively). The thinnest point of corneal thickness was statistically lower in the scar group (p = .03). In multivariable logistic regression analysis, preoperative keratometric astigmatism was a predictive value showing postoperative scar development (OR 11.81 95% CI 2.46–56.62, p = .002). Keratometric astigmatism had the highest sensitivity (90%), specificity (86.7%), and accuracy (95%) for scar formation at the best cut-off point of 5.61 D according to the ROC curve. Conclusions : A higher tendency for stromal haze development following CXL was determined in eyes with thinner corneas and higher keratometric astigmatism with the best cut-off value of 5.61 D.

Compaction of very thin corneas from ultraviolet A riboflavin-vitamin E transepithelial cross-linking

The purpose of the study was to determine the decrease in pachymetry of very thin corneas with advanced keratoconus due to corneal compaction from the ultraviolet-A (UV-A) irradiation phase of transepithelial (epi-on) cross-linking.Twenty removed corneal buttons were obtained from patients who underwent penetrating keratoplasty for advanced keratoconus. Removed corneal buttons selected from among the post-surgical specimens for this study had intact epithelium, no scarring or surgical cautery, endothelial cell density >2500 cells/mm2, and average pachymetry over the measured points of below 400 μm. Corneas were mounted in a Franz chamber. Each epithelial surface was soaked in isotonic riboflavin and D-alpha-tocopheryl polyethylene glycol 1000 succinate (Ribocross® IROMED Group, Italy) for 15 min. Pachymetry was measured at three points over both the shielded and unshielded corneal halves for each corneal button. Surfaces were then washed in saline to remove the Ribocross®. Shields from UV-A irradiation over half of each cornea were then fixed to stand 5 mm above the test corneas. UV-A irradiation using the custom fast cross-linking (CF-CXL) protocol was then performed for the typical 10 ± 1.5 min, for a total energy of 1.08 ± 0.6 J/cm2 after which pachymetry was re-measured.The average percent change in pachymetry was −0.43% ± 0.38% (maximum −1.06%) in the shielded half. Pachymetry change was −6.2% ± 2.2% (maximum 12%) in the cross-linked halves.In conclusion, we estimate that the change in corneal thickness from corneal compaction due to the cross-linking reaction itself was −5.8% ± 2.2%. Scanning electron microscopy of cross-linked corneal segments showed stromal fiber contraction.

Management of cataract in a patient with anterior megalophthalmos

A healthy 40-year-old man presented with reduced (counting fingers) right eye visual acuity (VA) due to a dense unilateral cataract (posterior subcapsular and nuclear sclerosis) ([figure 1A][1]). Examination revealed bilateral...

Effects of glaucoma and central corneal thickness on optic nerve head biomechanics.

To evaluate effects of glaucoma and central corneal thickness (CCT) on optic nerve head biomechanics. Four groups were formed according to CCT measurements and the presence of glaucoma. Glaucomatous patients with thin (< 510µ) and thick (> 570µ) corneas composed groups 1 and 3, respectively. Nonglaucomatous patients with thin and thick corneas composed groups 2 and 4, respectively. Real-time elastography (RTE) was performed on all groups, and optic nerve strain rate (ONSR), orbital fat strain rate (OFSR), and strain ratio of orbital fat to the optic nerve and medial and lateral parts of the optic nerve (SROFON, SROFMON, SROFLON, respectively) were obtained and compared between groups. The correlations between CCT and these parameters were also investigated. Statistically significant difference was not found between groups in terms of strain rate of optic nerve and orbital fat, SRFON, SROFMON and SROFLON. There was a positive correlation between ONSR and OFSR and mean CCT in patients with CCT thinner than 510µ (p: 0.03 r: 0.26, p: 0.01 r: 0.32 respectively). SROFON, SROFLON and SROFMON values did not differ between glaucomatous and nonglaucomatous patients with thin or thick CCTs. The correlations between CCT and OFSR and ONSR were found to be statistically significant in patients with thin CCT.

Biomechanical Properties in Different Types of Thin Corneas in Menoufia Population.

Background To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in normal thin (NT) healthy corneas with central corneal thickness (CCT) of 470–500 μm with matched thickness in keratoconus suspect (KCS) and keratoconus (KC) eyes. Methods A total of 103 eyes in three groups were included prospectively: NT, KCS, and KC groups based on clinical examination and Pentacam findings. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using the ocular response analyzer (ORA). CCT, CH, and CRF were compared between the three groups and statistically analyzed by variance tests. Results The three groups consisted of 44 NT, 26 KCS, and 33 KC. The mean CH measured was 8.689 ± 1.775, 9.051 ± 1.1190, and 8.129 ± 0.8539 mmHg in NT, KCS, and KC eyes, respectively. The mean CRF was 8.441 ± 1.663, 8.337 ± 1.114, and 7.2422 ± 1.3110 mmHg in NT, KCS, and KC eyes, respectively. Within the range of central corneal thickness (470–500 μm), only mean CRF was statistically significantly different between the NT and KC (P < 0.05); there was no statistically significant difference between NT and KCS, nor was the mean CH between each group (P > 0.05). Conclusions CRF only can be helpful in differentiating KC from NT eyes; KCS could not be predicted with either corneal biomechanical metrics. There was no benefit from CH in differentiating between the three study groups.

Association between central corneal thickness and ocular dominance in a South Indian population

Aims: The aim of the study is to investigate the association between ocular dominance and central corneal thickness (CCT) among normal eyes. Settings and Design: A cross-sectional study was conducted in the outpatient department of a tertiary care center in Southern India. Subjects and Methods: Participants of the study included 87 outpatients and volunteers with bilateral nonpathological eyes. This study was performed according to the tenets of the Declaration of Helsinki. To determine the dominant eye, hole-in-card test was utilized. Masked of the ocular dominance result, an independent observer measured CCT at the visual axis with specular microscopy (CEM-530, Nidek, Canada) by noncontact modality. Three readings were obtained from each eye. The right eye was first examined. Average of the three CCT readings was used for analysis. Statistical Analysis Used: Statistical methods included paired t-test (for comparison of eyes within patient) and Chi-square test to assess the association between ocular dominance and CCT. A P < 0.05 was considered statistically significant. Results: The 87 volunteers studied were aged 37.6 ± 14.8 years and 62.1% were female. CCT was 525.5 ± 28.4 μm in the right eye and 534.8 ± 29.8 μm in the left eye. Right eye was dominant in 63 (72.4%) patients. CCT in the dominant eye was 528.0 ± 29.5 μm and was significantly thinner (P < 0.001) than the nondominant eye (532.2 ± 29.3 μm). This was true in 69.0% of the patients. However, thinner cornea in a person was not indicative of a dominant eye (P = 0.535). Conclusions: As with other populations, right eye dominance was seen in South Indian population among nonpathological eyes. CCT is predominantly thinner in the dominant eye. Yet, this result cannot be applied to an individual by labeling the eye with thinner cornea as dominant with precision.

Safety and efficacy of epithelial island crosslinking in keratoconus with thinnest pachymetry less than 400µ

PURPOSE:To evaluate the efficacy and safety of epithelial-island crosslinking (EI-CXL) in keratoconus with corneas thinner than 400 µm.METHODS:Twenty-six patients (30 eyes) underwent EI-CXL (preserving the epithelium over the thinnest area), using standard protocol (3 mW/cm2 for 30 min). Uncorrected and best spectacle-corrected distance visual acuity (UCDVA, BCDVA), manifest refractive spherical equivalent (SEQ), mean simulated keratometry (Kmean), maximum keratometry (Kmax), and thinnest corneal thickness (TCT) were determined preoperatively and at 1, 3, 6, and 12 months following CXL. Endothelial cell count (ECC) was determined preoperatively and at 6 months. Anterior segment optical coherence tomography (AS-OCT) was done at 1 month to determine the depth of the corneal stromal demarcation line (DL).RESULTS:After 1 year, mean UCDVA improved from 1.29 preoperatively to 1.17 (P = 0.001) and BCDVA from 0.62 to 0.57 (P = 0.011). Mean manifest SEQ decreased from -7.63 to-7.32D (P = 0.001). Mean Kmean decreased from 54.92 to 54.81D (P = 0.045), and Kmax from 67.60 to 67.42D (P = 0.072), and mean TCT changed minimally from 377.17 to 375.30 µ (P = 0.11). The mean ECC decreased from 2329 to 2268 cells/mm2 (2.6% decrease, P < 0.001). AS-OCT showed a DL in 29 out of 30 eyes at an average depth of 215.9 µ under the spared epithelium, and 299.9 µ in the de-epithelialized cornea.CONCLUSION:EI-CXL halted keratoconus progression over a 1-year period. This was associated with statistically significant endothelial loss, but less than seen with conventional epi-off CXL in thinner corneas.

Corneal astigmatism in patients with various ophthalmic pathologies

To analyze the prevalence, magnitude of corneal astigmatism, anatomical parameters of the eye and age of patients with the condition, as well as to assess the prospects of its correction with intraocular lenses (IOLs). The study involved a retrospective analysis of initial biometric data of 128 379 patients (256 630 eyes) referred to the S.N. Fedorov NMRC «MNTK «EYE MICROSURGERY» research center in the years 2013 to 2018. The patients previously operated for cataract were examined 6 months after surgery. In 5 years, corneal astigmatism of over 1.0 D was diagnosed in 66 610 (25.96%) eyes. Among them, low astigmatism was observed in 86.30% of cases, with-the-rule - in 56.10%, compound - in 78.72%, and astigmatism combined with myopic refraction - in 61.48%. More severe astigmatism is characterized by thinner cornea and lens (p<0.05). Cataract surgery with implantation of toric IOLs was performed only on 2.56% of eyes. The average age of the operated patients was 68.42±13.3. Patients with implanted toric IOLs had 23% better uncorrected visual acuity (UCVA), and 15% better corrected visual acuity compared with outcomes of spherical IOL implantation. Corneal astigmatism of more than 1.0 D was observed in 25.96% of examined subjects. Patients with corneal astigmatism apply for cataract surgery 10 years earlier, when they are still in the working age, due to inability to engage in professional activities; in most cases, those patients are female. Astigmatism of up to 0.75 D is more common on the right dominant eye, of 2.0 D and higher - on the left. The correlation coefficients determined for study data indicate a barely noticeable relationship between biometric parameters and the degree of astigmatism. The use of toric intraocular lenses provides a 2-fold increase in uncorrected visual acuity compared to spherical IOLs.

Rare Keratopathy of Bilateral Anterior Amorphous Corneal Opacities with Spontaneous Corneal Stromalysis and Unilateral Descemetocele - Quantitative Framing with AS-OCT and Scheimpflug Imaging in inverse contrast

Posterior amorphous corneal dystrophy (PACD) is classically characterised by bilaterally thin and flat central corneas with a deep, stromal sheet-like opacity. The epithelium, Bowman's layer, and anterior stroma are usually normal in PACD. Here, we report a case that had bilaterally anterior oval amorphous corneal opacities, which is different from the typical presentation of PACD. Corneal stromalysis occurred in them with progression to descemetocele unilaterally. To our knowledge, Scheimpflug images of anterior amorphous opacities especially with spontaneous corneal stromalysis and descemetocele are poorly reported in literature. Hence the objective of this manuscript was to throw light to the lacunae in literature, by describing the Scheimpflug images of this rare keratopathy in default and inverse contrast for better quantitative framing of the pathology.

Exploring the Relationship Between Central Corneal Thickness and Intraocular Pressure Among Nonglaucoma Patients in a General Ophthalmology Clinic, South East Nigeria

Context: Glaucoma is an important cause of irreversible blindness and visual impairment in Nigeria. Studies have shown that intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. The true IOP of an individual, in turn, is determined by the central corneal thickness (CCT). Aim: The aim of the study is to describe the relationship between IOP and CCT among nonglaucoma patients in Owerri, Imo State, Nigeria. Methods: This was a hospital-based, cross-sectional, analytical study done on nonglaucomatous patients aged 18 years and above. A comprehensive ocular examination was carried out for all participants and IOP was measured between 8 am and 12 noon to reduce the effect of diurnal variations. Results: Four hundred and twenty-two subjects with a mean age of 40.34 ± 14.468 years and a female to male ratio of 1.7:1 participated. The mean measured IOP was 16.77 ± 4.37 mmHg, and the mean CCT was 533.05 ± 33.92 μm. The mean corrected IOP was 17.61 ± 4.57 mmHg indicating a pattern of falsely low IOP. There was a positive, statistically significant correlation between IOP and CCT (P = 0.045). Conclusion: There was a positive correlation between IOP and CCT with the resultant effect that thin corneas presented with falsely low IOP and thick corneas with falsely high IOP. Routine CCT measurement in addition to IOP measurement should be done on every patient.

Preliminary results of a new intrastromal corneal ring segment as a tissue saving procedure in photorefractive keratectomy to correct moderate to high myopia.

To evaluate the clinical results after implantation of a new intrastromal corneal ring segment (ICRS) associated with photorefractive keratectomy (PRK) to correct high myopia (HM) patients with thin corneas. We evaluated 42 eyes of 23 HM patients that had ICRS implantation followed by PRK. The mean age of patients was 29.1±7.12y (range 18 to 40 years old). Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry, spherical equivalent, pachymetry, and aberrometry were compared using ANOVA with repeated measurements evaluated preoperatively and at last follow-up visit after the procedures. The refractive predictability and simulated/real corneal ablation were also assessed. The mean follow-up time after PRK was 6.8±1.6mo. The mean preoperative UCVA improved from 20/800 preoperative to 20/100 after ICRS and 20/35 after PRK. The mean preoperative BCVA was 20/25 (range from 20/30 to 20/20) and remained unchanged after ICRS implantation. Following the PRK the mean BCVA was 20/25 (range from 20/30 to 20/20). The mean spherical equivalent decreased from -7.25±1.12 (range -5.00 to -9.00) preoperatively to -3.32±1.0 (range -2.00 to -5.00) postoperatively (P<0.001) after ICRS implantation and decreased from -2.44±1.51 preoperatively to 0.32±0.45 (range -0.625 to 0.875) postoperatively (P<0.001) after PRK. The change in BCVA and topographic astigmatism was statistically significant (P<0.0001). ICRS in HM associated with PRK can be a tissue saving procedure and an alternative surgical option for correction of moderate to high myopia.