Thin Corneas Research Articles

Subtotal Transepithelial Phototherapeutic Keratectomy with Mitomycin C Application for Central Corneal Opacities-Three Case Series

Purpose: To evaluate the beneficial effects of transepithelial subtotal phototherapeutic keratectomy (PTK) with mitomycin C application for corneal opacities on patients’ visual acuity. Methods: Three cases with central corneal opacities were subjected to transepithelial subtotal (PTK) using Excimer laser ablation with mitomycin C (0.02%) application for 2 minutes, the first case with a central post-PRK with mitomycin corneal scar 98 µ depth, where PTK ablation depth only 70 µ (thin cornea=430 µ), the second case with a central post-traumatic corneal scar 121 µ depth, with PTK ablation depth only 70 µ (thin cornea=480 µ) and the third case with right corneal (granular) dystrophy, with opacity level was 200 µ, where PTK of only 100 µ was done (young female patient). Results: The BCVA increased from 0.2 to 0.7 in case 1 and from 0.2 to 0.5 in case 2 and from 0.05 to 0.5 in case 3, without evidence of residual haze in case 1, and with minimal residual haze in case 2 and case 3. Conclusion: In the presence of relatively non-superficial corneal opacities of various causes, subtotal transepithelial phototherapeutic keratectomy with mitomycin C application can result in marked improvement of visual acuity without the need for keratoplasty.

Correlation between central corneal thickness and retinal nerve fiber layer thickness in open-angle glaucoma

Background Central corneal thickness (CCT) is an important risk factor in the development and progression of primary open-angle glaucoma (POAG). The retinal nerve fibers respond to high intraocular pressure (IOP) with irreversible loss. So, there is a great interest to study the correlation between these two factors: CCT and retinal nerve fiber layer thickness (RNFLT) using the spectral-domain optical coherence tomography (SD-OCT). Aim The aim of this study was to correlate the CCT and the RNFLT in POAG patients by using SD-OCT. Patients and methods This study was conducted in Menoufia University Hospitals, Egypt, from October 2017 to October 2018. The study included 116 eyes of 61 patients with POAG receiving antiglaucomatous eye drops with controlled IOP. CCT and peripapillary RNFLT were measured by using SD-OCT (Optovue RTVue-100). Then, we performed a correlation between them. Results The study included 61 (40 males and 21 females) patients. The mean age was 51.5±6 years. A significant positive relationship was found between the CCT and the RNFLT (r=0.6). This means that patients with thick cornea have thicker nerve fiber layer than those with thinner corneas. Conclusion CCT is an important risk factor and predictive factor for both diagnosis and prognosis of POAG. So, it is mandatory to be measured to modify the IOP measurements and to correlate with the nerve fiber layer thickness. This helps us to tailor the plan of treatment.

The Short-Term Safety Evaluation of Corneal Crosslinking Agent-Genipin

Background: Genipin (GP) is a safe method for corneal crosslinking, even for very thin corneas. However, there have been no reports on the optimal GP concentration range to use in vivo for corneal crosslinking. Objectives: To investigate the safety of corneal crosslinking after a 24-h incubation with different concentrations of GP. Methods: Twenty New Zealand white rabbits were divided into a phosphate-buffered saline (PBS) group, 0.2% GP crosslinking (GP-CXL) group, 0.25% GP-CXL group, and 0.3% GP-CXL group. Before and after surgery, the operated eyes of each group were characterized by confocal microscopy, and corneal buttons were excised for endothelium staining and electron microscopy. Results: The keratocyte structures in each GP group appeared to be similar to those in the PBS group. Through the confocal microscopy, the changes in corneal endothelial cell density also did not significantly differ among groups. There was a significant difference in apoptosis between the 0.3% GP-CXL and PBS groups (p < 0.05) and between the 0.3% GP-CXL and 0.25% GP-CXL groups (p < 0.05), but there were no significant differences between the 0.2 and 0.25% GP-CXL groups compared to the PBS group. Transmission electron microscopy showed endothelial cell damage in the 0.3% GP-CXL group, with minimal endothelial cell damage in the other groups. Conclusions: Treatment of rabbit corneas with ≤0.25% GP resulted in minimal toxicity to keratocytes and endothelial cells, suggesting that it is a safe crosslinking agent at those concentrations.

Diurnal variation of central corneal thickness and intraocular pressure in eyes with pseudoexfoliation

Purpose:Pseudoexfoliation syndrome (PXS) is an age related microfibrillopathy characterized by deposition of whitish flaky material over various ocular tissues. PXS eyes are known to have thinner corneas and thus can lead to an underestimation in intraocular pressure measurement. The purpose of this study was to find if there is any variation in central corneal thickness and intraocular pressure in PXS eyes and if there was any relationship between them.Methods:A prospective observational study was done on 141 eyes of 85 patients with PXS without glaucoma between November 2015 to April 2017 in the department of Ophthalmology in a tertiary hospital. CCT and IOP were measured by a handheld ultrasonic pachymeter (DGH Technology INC. Pachette 2, USA) and Goldmann applanation tonometer respectively at 4 different times during office hours.Results:A significant reduction of about 10 μm in mean CCT and 1.4 mmHg in mean IOP was noted over the 4 sessions which was statistically significant (P < 0.001). A significant correlation exists between IOP and CCT in PXS eyes at all times during the day (P < 0.001).Conclusion:The CCT measurements show significant thinning throughout the day, similar drop in IOP was also noted. Our study shows that there is a significant correlation between diurnal variation of CCT and IOP. Hence, it is prudent to measure CCT along with IOP at all times.

Correlation between retinal nerve fiber layer thickness and central corneal thickness in ocular hypertension

Aim: The aim of the study is to determine correlation between the retinal nerve fiber layer thickness (RNFL) and central corneal thickness (CCT) in patients with ocular hypertension (OHT) and age-matched control. Materials and Methods: This was a prospective, observational study, done between January 2016 and June 2017 at a rural tertiary care eye center. Participants diagnosed with OHT, defined as an intraocular pressure (IOP) of 21 mm Hg or higher, with normal optic disc and visual field, in the absence of any other ocular disease, were included in the study. The control group included age- and sex-matched participants with normal IOP, optic discs, and visual fields. Patients with OHT were subdivided into thin (CCT ≤555 μm) and thick (CCT >555 μm) corneas. RNFL was measured with spectral-domain optical coherence tomography and CCT with ultrasound pachymetry. Statistical Analysis: Mean, percentage, and standard deviation were used for descriptive values. Mean, standard deviation, and 95% confidence interval were utilized for the analysis of IOP, CCT, and RNFL. Mean was compared using the independent t-test. P

Development of a new algorithm for treatment of primary angle closure glaucoma

Purpose – to develop a new algorithm for treatment of primary angle closure glaucoma (PACG) based on laser peripheral iridotomy (PI) and selective laser trabeculoplasty (SLT) and to determine its indications and contraindications. 68 eyes with PACG were observed for 6 years. These patients had undergone PI and then SLT. The control group included 74 POAG eyes of the same age and stage of glaucoma. The effectiveness of SLT was assessed using the Kaplan-Meier survival analysis. The risk factors for SLT failure in the long-term period were studied to determine the indications and contraindications for this treatment algorithm, and the condition of corneal endothelium in dynamics was investigated using confocal microscopy. The hypotensive effect of SLT in PACG was worse than in POAG: 90 and 93% respectively one year after SLT, and 16 and 21% six years after SLT (log rank test, p=0.195). The following factors of SLT failure were common for both forms of glaucoma: IOP &gt;24 mm Hg, corneal thickness ≤540 µm, corneal hysteresis &lt;7 mm Hg and age of patients &gt;68 years. The extension of laser action &lt;1800 and lens thickness &gt;4.8 mm were additional predictors of SLT failure in PACG. In both forms of glaucoma, diabetes mellitus, age of patients and duration of the disease before SLT had a negative effect on the condition of corneal endothelium. The anterior-posterior axis and the presence of pigment deposition on the endothelium were significant in PACG. The proposed algorithm for PACG treatment, including the initial performance of PI and then SLT, is an effective method of treating this form of glaucoma, provided that the opening of the anterior chamber angle is sufficient (at least half) and the lens thickness is no more than 4.8 mm. The initially high IOP, the age of patients over 68 and a thin cornea (&lt;540 μm) worsen the SLT prognosis. Moreover, diabetes mellitus and the presence of pigment deposition on the endothelium along with long-term glaucoma history increase the risk of corneal endothelium damage after SLT.

Predictive Factors for Successful Type 1 Big Bubble during Deep Anterior Lamellar Keratoplasty.

Objective Big bubble (BB)-deep anterior lamellar keratoplasty (DALK) has become the reference transplantation technique for corneal stromal disorders. Type 1 BB is the desired aspect but it is not constant. We aimed to determine the predictive factors of type 1 BB success. Methods Observational cohort study including 77 consecutive eyes of 77 patients undergoing DALK by one surgeon at a single reference center without any selection. Clinical and spectral domain optical coherence tomography data were collected pre- and postoperatively. Results Stromal scars were found in 91.8% of cases and were located in the anterior (90.9%), mid (67.5%), and posterior (36.4%) stroma. Type 1 BB (49.3% of cases) was significantly associated with the absence of scars in the posterior stroma, stage 1–3 keratoconus, and deep trephination. Among eyes with posterior scars, type 1 BB was associated with higher minimal corneal thickness, maximum-minimum corneal thickness < 220 μm, and diagnosis other than keratoconus. Eyes with type 1 BB featured significantly thinner residual stromal bed (22 ± 8 µm versus 61 ± 28 µm), thinner corneas at 12, 24, and 36 months, and better visual acuity at 12 months compared with eyes with no type 1 BB. Conversely, no significant differences between both groups were observed for graft survival, visual acuity at 24 and 36 months, and endothelial cell density at 12 and 36 months. Conclusion OCT assessment before DALK is useful for choosing trephination depth that should be as deep as possible and for looking for posterior scars. The BB technique may not be the most appropriate method in keratoconus with posterior scars. Follow-up data do not support the need for conversion to penetrating keratoplasty when type 1 BB cannot be obtained nor does it support the need for performing a penetrating keratoplasty as a first-choice procedure in eyes with posterior stromal scars.

Biomechanical efficacy of contact lens-assisted collagen cross-linking in porcine eyes.

Contact lens-assisted corneal cross-linking (CACXL) has been proposed for the cross-linking treatment in thin corneas. The aim of this study was to assess the biomechanical efficacy of this treatment. Post-mortem porcine eyes were treated with standard cross-linking and with cross-linking placing a contact lens soaked with isoosmolar riboflavin solution on the debrided cornea with or without an adherent precorneal riboflavin film of up to 100μm thickness. Three soft contact lenses (Air Optix Aqua, SofLens and Galifa) with different degrees of hydrophilic properties were tested. After cross-linking with a surface UVA irradiance of 3mW/cm² for 30min (fluence 5.4J/cm²), a 400μm deep anterior corneal flap was created using a lamellar rotating microkeratome. Biomechanical stress-strain measurements and thermal shrinkage tests were performed. In the Air Optix Aqua group (30% hydration) without riboflavin film, Young's modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was 92.4% respectively 86.35% of the standard CXL value. In the SofLens group (59% hydration) without riboflavin film, Young's modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was 67.04% respectively 65.28% of the standard CXL value. In the Galifa group (72% hydration) without riboflavin film, Young's modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was about 68.48% respectively 75.52% of thestandard CXL value. In all samples with a precorneal riboflavin film under the contact lens, there was no significant biomechanical effect compared to the untreated controls. Similarly, in the hydrothermal experiments at 70°C, there was a typical mushroom pattern with increased resistance to thermal shrinkage in the anterior stroma after standard CXL, a markedly reduced mushroom effect using a riboflavin-soaked contact lens only and no effect with the use of a riboflavin-soaked contact lens plus a precorneal riboflavin film. The biomechanical effect of CACXL in porcine corneas is about one-third less than after standard CXL. The efficacy of CACXL might be improved by reducing or omitting the riboflavin film on the contact lens. Further risk assessment studies are necessary.

Agreement and Repeatability of Two Biometers to Measure Anterior Segment Components: Refractive Error Effect.

BackgroundTo assess the repeatability and agreement between a new high-resolution optical coherence tomographer (OCT) and a Scheimpflug topographer.Material/MethodsSixty phakic and healthy participants were measured in this study, and one eye per participant was analyzed. Depending on their refractive error, each participant was allocated into a myopic, hyperopic, or emmetropic group. The Cirrus HD-OCT 5000 (Carl Zeiss Meditec, Jena, Germany), and the Sirius Scheimpflug topographer (Costruzione Strumenti Oftalmici, Florence, Italy) were used to take all measurements.ResultsThe repeatability of these instruments to measure the anterior chamber depth, angle-to-angle, thinnest pachymetry, and both nasal and temporal angles was smaller than 0.15 mm, 0.40 mm, 10 μm, and 10 degrees, respectively. However, the repeatability of the Scheimpflug instrument to measure the apex pachymetry was about 15 μm, and for the OCT, it was about 4 μm for all groups. On average, the Sirius Scheimpflug instrument measured shallower anterior chamber depth (about 0.10 mm), shorter angle-to-angle (about 0.5 mm), thinner corneas (approximately 10 μm), and narrower angles (around 5 degrees) for all refractive groups.ConclusionsThe repeatability of the Cirrus OCT and Sirius Scheimpflug instrument was good and independent of the refractive error. Nevertheless, to judge whether these instruments could be used interchangeable, clinical criteria are needed.

Pentacam HR Indices Variation in Normal Corneas with Different Corneal Thickness.

Purpose To evaluate the effect of variable corneal thickness on Pentacam HR diagnostic indices in normal corneas. Methods Retrospective study was conducted at Al Watany Eye Hospital, Cairo, Egypt. Consecutive 160 eyes of young myopic subjects without KC were evaluated using Pentacam HR (WaveLight Allegro Oculyzer II, Erlangen, Germany). The elevation- and thickness-based indices were recorded. Enrolled corneas were categorized into three groups according to TCT quartiles; group 1 (39 eyes) included corneas with TCT <523 µm, group 2 (81 eyes) with TCT between 523 and 564 µm, while group 3 (40 eyes) enrolled TCT >564 µm. The possible effect of pachymetry on Pentacam HR indices was assessed using partial correlation tests. Results In normal corneas, back elevation from best fit sphere (BE from BFS) and that from best fit toric ellipsoid (BFTE) were the elevation indices that showed statistically significant differences among groups (P=0.013 and 0.019, respectively). Regarding pachymetric indices, maximum pachymetry progression index (PPI max) showed statistical significance (P=0.001). Partial correlations, after excluding age and refractive error effects, showed that TCT was correlated with BE from BFS, BE from BFTE, and PPI max (P=0.001, 0.001,0.002, respectively). Conclusions Some Pentacam HR indices varied with different corneal thickness in normal corneas. This necessitates inclusion of pachymetric subgroups in the normative database. The use of the more robust indices (average pachymetry progression index and front elevations) is recommended in relatively thin or thick corneas.

Central corneal thickness in a Jordanian population and its association with different types of Glaucoma: cross-sectional study

BackgroundCentral corneal thickness (CCT) has long been implicated to affect glaucoma predisposition. Several reports have identified that thinner CCT is a risk factor for open-angle glaucoma, and that CCT can be very variable between different ethnic groups. In this study, we aim to identify the relation between CCT and different glaucoma parameters in different types of glaucoma in an Arabian ethnicity.MethodsWe classified our participants into four main groups: primary open-angle glaucoma (POAG), primary angle-closure glaucoma (PACG), pseudoexfoliative glaucoma (PXFG), and a control group. We obtained demographics, intraocular pressure (IOP), cup to disc ratio (CDR), visual field mean deviation (MD) and pattern standard deviation (PSD), CCT, and retinal nerve fiber layer (RNFL) thickness for each participant.ResultsWe included A total of 119 eyes with glaucoma, including POAG (54 eyes), PXFG (31 eyes) and PACG (34 eyes), we also included 57 control eyes. We found that PACG eyes have the thinnest CCT. Mean measurements of CCT for our groups were: 538.31 μm (SD = 36.30) in eyes with POAG, 544.45 μm (SD = 28.57) in eyes with PXFG, 506.91 μm (SD = 34.55) in eyes with PACG and 549.63 μm (SD = 42.9) in the control group. We found that CCT is significantly correlated with CDR (p = 0.012, r = − 0.231), MD (p < 0.001, r = 0.327),and RNFL thickness (p = .007, r = .283).ConclusionIn Arabian ethnicity, PACG patients have the thinnest CCT compared to other types of glaucoma, namely POAG and PXFG. We demonstrated that glaucomatous eyes with thinner corneas will probably have more advanced glaucomatous optic neuropathy. Our results emphasize the importance of taking ethnicity into account upon glaucoma management.

Incidence and Clinical Characteristics of Post LASIK Ectasia: A Review of over 30,000 LASIK Cases

ABSTRACTPurpose: To report the incidence of postoperative ectasia after laser in situ keratomileusis (LASIK). Methods: A retrospective case review of 30,167 eyes (16,732 patients) was conducted following LASIK between August 2007 and August 2015. The follow-up was between 2 and 8 years. Tomography was performed after 2 years postop. After identifying cases of ectasia, the charts of these patients were examined to identify any common factors that may have predisposed them to develop ectasia. Results: Ten eyes of seven patients developed post-LASIK ectasia. Eight eyes had been treated for myopia and myopic astigmatism, two eyes for mixed astigmatism. There were no cases of ectasia after LASIK for hyperopia. All 10 cases of ectasia had a flap that was created using the Moria M2 mechanical microkeratome (average flap thickness 118.15 ± 12.88 µm) and refractive error corrected using the Wavelight Allegretto excimer laser. Retrospectively, most prevalent risk factors were thin cornea (≤ 500 µm, 50% of cases), anterior topographic map irregularities (e.g., asymmetric bow tie, 40% of cases), Ectasia Risk Score > 3 (40% of cases), percent tissue thickness alteration ≥ 40% (20% of cases) and low residual stromal bed (≤ 300 µm, 30% of cases). One eye had no identifiable risk factors. In the retrospective chart review 14.97% (4,506) of all the eyes had similar risk factors to the cases that went on to develop ectasia. Conclusion: The incidence of ectasia was 0.033% over 8 years. The incidence could be higher as some cases may destabilize beyond this period and some patients were lost to follow-up asymptomatic of any clinical signs. Other intrinsic factors may trigger the development of post LASIK ectasia. The current widely accepted risk factors are not sufficiently rigorous for screening out potential ectasia from developing after LASIK. There is a need to augment accuracy with higher sensitivity and specificity.

Biomechanical efficacy of corneal cross-linking using hypoosmolar riboflavin solution.

The use of hypoosmolar riboflavin solution has been suggested for cross-linking thin corneas. The aim of this study was to compare the biomechanical efficacy of corneal cross-linking using hypoosmolar dextran-free riboflavin solution (HCXL) versus isoosmolar standard corneal cross-linking treatment (CXL). A total of 24 postmortem porcine eyes with debrided corneas were subdivided into three treatment groups: Controls, the isoosmolar group with isoosmolar 0.1% riboflavin-20% dextran solution and the hypoosmolar group with dextran-free, 0.1% riboflavin solution. The samples were irradiated with UVA light of 365 nm wavelength and an irradiance of 3 mW/cm² for 30 min (dose 5.4 J/cm²). For the biomechanical measurements, 400-µm-deep anterior corneal flaps were created using a lamellar rotating microkeratome. Uniaxial stress-strain measurements were performed. In the isoosmolar treatment group, stress and Young's modulus at 8% strain were significantly increased by 67.97%, respectively, 62.62% versus the controls. In the hypoosmolar treatment group, stress and Young's modulus at 8% strain were significantly increased by 81.21%, respectively, 51.40% versus the controls. There was no significant difference between the iso- and hypoosmolar groups in biomechanical efficacy. On histology, there was no edema in the anterior 200 µm of the corneas after stromal swelling by the hypoosmolar riboflavin solution. Corneal cross-linking using isoosmolar or hypoosmolar riboflavin solution induces a comparable biomechanical effect. This is explained by the localization of the maximum cross-linking effect in the anterior 200 µm of the cornea which are not affected by the swelling effect of hypoosmolar riboflavin solution.

Clinical Outcomes after Keraring Implantation for Keratoconus Management in Thin Corneas

The aim of our study was to evaluate the clinical outcomes after Keraring implantation for keratoconus in patients with thin corneas. Ten eyes from 10 patients with keratoconus, who underwent femtosecond laser-assisted Keraring implantation for keratoconus, were included in this retrospective study. Uncorrected visual acuity (UCVA), corrected visual acuity (CDVA), keratometric readings, central corneal thickness and thinnest corneal pachymetry have been evaluated preoperatively and 6 months after the Keraring implantation. UCVA, BCVA and keratometric readings improved at 6 months postoperatively. Our data showed significant keratometric amelioration and visual improvement after Keraring implantation for keratoconus in patients with thin corneas at 6 months postoperatively.

Prevalence of Keratoconus in a Refractive Surgery Population.

Objective This study examined the prevalence of keratoconus among patients who were interested in undergoing refractive surgery. Corneal tomography measurements were used to help detect keratoconus. Methods Adult subjects who presented to the private hospital Cataract and Refractive Surgery Unit (Abha, Saudi Arabia) for refractive surgery evaluation were considered for inclusion in this cross-sectional, retrospective study. All subjects were from the Aseer province, a southern, high-altitude region in Saudi Arabia, and presented between January and December 2017. The incidence of keratoconus and other refractive surgery contraindications were examined. Results A total of 2931 patients were considered for inclusion in analyses. Of these, 2280 patients (77.8%) were not candidates for refractive surgery. These 2280 patients had a mean age of 24.1 ± 6.6 years and 1231 patients (54.0%) were male. Of the subjects who did not undergo refractive surgery, 548 (24%) had keratoconus, 400 (17.5%) were keratoconus suspects, 344 (15.1%) had thin corneas, 321 (14.1%) had high myopia, and 52 (2.3%) had a high astigmatism. An additional 479 subjects (21%) were candidates for refractive surgery, but chose not to undergo a procedure. Conclusion The incidence of keratoconus in Saudi Arabian refractive surgery prospects was 18.7%. Keratoconus was the most common reason for not performing refractive surgery and accounted for 24.0% of cases in which surgery was not performed.

Crescentic Tuck in Lamellar Keratoplasty—A Novel Technique in a Case of Advanced Pellucid Marginal Corneal Degeneration

To describe a new surgical technique "crescentic tuck in lamellar keratoplasty" for the management of advanced pellucid marginal corneal degeneration (PMCD). A 45-year-old man with advanced PMCD and maximal thinning in the inferior juxtalimbal periphery underwent a crescentic lamellar keratoplasty in the right eye. Best-corrected visual acuity was 6/60 with no further improvement because of severe irregular astigmatism. Thinnest pachymetry in the peripheral cornea was 280 μm. Peripheral crescent-shaped lamellar corneal dissection of 3.5-mm width was performed, and an intrastromal pocket was fashioned from 4 to 8 O'clock, extending beyond limbus. A crescent-shaped donor corneal button of 3.5-mm width was denuded of its endothelium and beveled in inferior periphery to create a flange. The flange was tucked into the peripheral scleral pocket. The donor graft was secured to the host bed using 10-0 nylon interrupted sutures. Donor cornea integrated with the host bed over time and best spectacle-corrected visual acuity at 1 year improved to 6/9 with -1.25/-3.5 D × 90°. The simK (simulated keratometry) changed from 41.6/56.3 diopters (D) to 45.1/50.6 D. The astigmatism reduced from 14.6 D to 5.5 D. Crescentic tuck in lamellar keratoplasty provides good apposition of the donor lenticule and tectonic support to the peripheral thin cornea while preserving the peripheral limbal stem cells. Additionally, there is a significant reduction in the astigmatism, resulting in visual improvement.

Customized epithelial island corneal collagen cross-linking for progressive keratoconus

Objective To evaluate the efficacy of epithelial island collagen cross-linking (CXL) for progressive keratoconus with thin cornea. Methods A prospective study, forty-two eyes of 42 cases with keratoconus with thickness less than 450 μm were enrolled. They received epithelial island CXL. The follow-up time was 12 months. Results One month postoperatively, the keratocytes apoptosis associated with nerve fibers loss in the 160 μm deep deeassociated under the epithelial island were observed with confocal microscope. The keratocytes apoptosis in the paracentral 250 μm deep epithelialized ring was recorded. Preoperative endothelial cell density was (2 455±73) cells/mm2. At the end of follow-up, final endothelial cells density was (2 459±69) cells/mm2. The difference was not statistically significant (t=1.68, P=0.21). Simulated K values at 12 months after surgery decreased 0.7±0.6 diopters, the difference was statistically significant (t=8.71, P=0.04). Coma values at 12 months after surgery decreased (0.7±0.1)μm, the difference was not statistically significant (t=7.43, P=0.06). Optical pachymetry demonstrated a slight decline at 3 months after surgery and the thickness resembled the baseline at 6 and 12 months follow-up. According to the VAS pain scale, the average value early postoperatively was 2(range 1-3), a mild pain could be tolerated. Conclusion Customized epithelial island cross-linking treatment(CXL) is a safe and effective method for progressive keratoconus with thin cornea. Key words: Cross-linking, collagen, cornea, epithelium island, customized; Keratoconus

Сравнительный анализ коррекции миопии высокой степени и сложного миопического астигматизма методом фемтолазерной интрастромальной имплантации кольца MyoRing у пациентов с тонкой роговицей и имплантации отрицательной факичной ИОЛ

Сравнительный анализ коррекции миопии высокой степени и сложного миопического астигматизма методом фемтолазерной интрастромальной имплантации кольца MyoRing у пациентов с тонкой роговицей и имплантации отрицательной факичной ИОЛ

Сorrection of Corneal Astigmatism in Patients with a Thin Cornea by Improved Combined Technology

Purpose:to carry out an advanced combined technology, including femtosecond astigmatic keratotomy and topographically-oriented photorefractive keratectomy in order to correct corneal astmigmatism in patients with a thin cornea. Presentation and evaluation of the results of this observation.Patients and methods. There are data of 19 patients (30 eyes) with complex myopic astigmatism combined with a thin cornea who received the operation of femtosecond astigmatic keratotomy (the first stage of an improved combined technology). Mean values before surgery: sph –4.1 ± 2.1 (from –0.3 to –7.8) D, cyl –4.9 ± 1.4 (–3.0 to –7.3) D, UDVA 0.1 ± 0.05 (from 0.01 to 0.2) of the rows of table, CDVA 0.6 ± 0.1 (from 0.4 to 0.9) of the rows of table, Kmax 46.70 ± 1.1 (from 44.50 to 48.50), Kmin 42.8 ± 1.3 (from 40.00 to 44.00), the thickness of the cornea is 470.0 ± 12.7 (from 4470 to 495.0) μm. The second stage: topographically oriented photorefractive keratectomy was performed to the same patients with the aim of correcting residual ametropy. Mean values before surgery: sph –5.3 ± 2.0 (from –1.8 to –8.8) D, cyl –1.6 ± 0.8 (from –0.5 to –3.0) D, UDVA 0.3 ± 0.1 (from 0.1 to 0.6) rows of the table, CDVA 0.7 ± 0.1 (from 0.5 to 0.9) rows of the table, Kmax 46.70 ± 1.1 (from 44.50 to 48.50), Kmin 42.8 ± 1.3 (from 40.00 to 44.00), the thickness of the cornea 464.3 ± 8.3 (from 460.0 to 485.0). All patients from the study received a diagnostic examination by standard and special methods based on the S. Fyodorov Eye Microsurgery State Institution, a screening of the keratoconus on the scanning topograph Pentacam HR “Oculus Optikgerate GmbH”, Germany was carried out. The first stage of the advanced combined technology was used the LenSx Laser (“Alcon”, USA), the second stage — WaveLight EX-500 (“Alcon”, USA), was used.Results. After the completion of two stages of improved combined technology the following results were obtained: reduction of the sph with –4.1 ± 2.1 (from –7.8 to –0.3) to –0.4 ± 0.3 (from –1.0 to 0.0), cyl with –4.9 ± 1.4 (from –7.3 to –3.0) to –0.1 ± 0.1 (from –0.5 to 0.0), Kmax from 44.70 ± 1.1 (from 44.50 to 48.50) to 37.8 ± 1.6 (from 36.00 to 43.00), Kmin 42.80 ± 1.3 (from 40.00 to 44.00) to 37.00 ± 1.3 (from 36.00 to 40.00), CDVA growth with 0.6 ± 0.l (from 0.4 to 0.9) to 0.8 ± 0.1 (from 0.5 to 1.0), UDVA from 0.1 ± 0.05 (from 0.01 to 0.2) to 0.7 ± 0.1 (from 0.4 to 0.9).Conclusion. The improved combining technology, including femtosecond astigmatic keratotomy and topographically — oriented photorefractive keratectomy is effective and safety technology, allowing to correct of corneal astigmatism in patients with a thin cornea.

Long-term safety of laser in situ keratomileusis in eyes with thin corneas: 5-year follow-up.

To investigate the long term (≥5y) efficacy, predictability, and safety of laser in situ keratomileusis (LASIK) in eyes with thin corneas [central corneal thickness (CCT) <500 µm]. A total of 339 patients met the criteria of this study. Finally, 175 eyes of 89 patients who had thin corneas and underwent LASIK≥5y ago returned to our clinic and included in this study. Preoperative parameters recorded included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), manifest refraction, CCT and corneal topography. At returning visits, in addition to visual acuity and manifest refraction, ultrasound CCT and corneal topography were performed. Optical coherence tomography was used to measure the CCT, LASIK flap thickness, and residual stromal bed thickness (RSBT). Safety index, efficacy index, percentage of eyes within ±0.5 D and ±1.0 D of refraction, percent tissue altered (PTA), and percentage stromal bed thickness (PSBT) were calculated. The safety index was 1.09 and efficacy index was 0.99. The percentages of eyes within ±0.5 D and ±1.0 D were 71.2% and 87.7%, respectively. The mean PTA was 40%±6% (range 20% to 55%); 76 eyes (43.4%) had PTA <40% and 99 eyes (56.6%) had PTA≥40%. The mean RSBT was 303±27 µm (range 240 to 390 µm), and 2 eyes had RSBT<250 µm. The mean PSBT was 61%±9% (range 51% to 85%). No eyes developed ectasia. In this cohort with the PSBT of 50% or more, LASIK is safe with follow-up for at least 5y.