Maximum Keratometry Research Articles

Short- and long-term safety and efficacy of corneal collagen cross-linking in progressive keratoconus: A systematic review and meta-analysis of randomized controlled trials.

The purpose of the study is to evaluate the safety and outcomes of corneal collagen cross-linking (CXL) and different CXL protocols in progressive keratoconus (PK) population at short and long-term. A systematic review and meta-analysis was conducted. A total of eight literature databases were searched (up to February 15, 2022). Randomized controlled trials (RCTs) comparing CXL versus placebo/control or comparing different CXL protocols in the PK population were included. The primary objective was assessment of outcomes of CXL versus placebo and comparison of different CXL protocols in terms of maximum keratometry (Kmax) or Kmax change from baseline (Δ), spherical equivalent, best corrected visual acuity (BCVA), and central corneal thickness (CCT) in both at short term (6 months) and long term (1st, 2nd, and 3rd year or more). The secondary objective was comparative evaluation of safety. For the meta-analysis, the RevMan5.3 software was used. A total of 48 RCTs were included. Compared to control, CXL was associated with improvement in Δ Kmax at 1 year (4 RCTs, mean difference [MD], -1.78 [-2.71, -0.86], P = 0.0002) and 2 and 3 years (1 RCT); ΔBCVA at 1 year (7 RCTs, -0.10 [-0.14, -0.06], P < 0.00001); and Δ CCT at 1 year (2 RCTs) and 3 years (1 RCT). Compared to conventional CXL (C-CXL), deterioration in Δ Kmax, ΔBCVA and endothelial cell density was seen at long term in the transepithelial CXL (TE-CXL, chemical enhancer). Up to 2 years, there was no difference between TE-CXL using iontophoresis (T-ionto) and C-CXL. At 2 and 4 years, C-CXL performed better compared to accelerated CXL (A-CXL) in terms of improving Kmax. Although CCT was higher in the A-CXL arm at 2 years, there was no difference at 4 years. While exploring heterogeneity among studies, selection of control eye (fellow eye of the same patient vs. eye of different patient) and baseline difference in Kmax were important sources of heterogeneity. CXL outperforms placebo/control in terms of enhancing Kmax and CCT, as well as slowing disease progression over time (till 3 years). T-ionto protocol, on the other hand, performed similarly to C-CXL protocol up to 2 years.

A randomized clinical trial assessing theranostic-guided corneal cross-linking for treating keratoconus: the ARGO protocol

The Assessment of theranostic guided riboflavin/UV-A corneal cross-linking for treatment of keratoconus (ARGO; registration number NCT05457647) clinical trial tests the hypothesis that theranostic-guided riboflavin/UV-A corneal cross-linking (CXL) can provide predictable clinical efficacy for halting keratoconus progression, regardless of treatment protocol, i.e., either with or without epithelial removal. Theranostics is an emerging therapeutic paradigm of personalized and precision medicine that enables real-time monitoring of image-guided therapy. In this trial, the theranostic software module of a novel UV-A medical device will be validated in order to confirm its accuracy in estimating corneal cross-linking efficacy in real time. During CXL procedure, the theranostic UV-A medical device will provide the operator with an imaging biomarker, i.e., the theranostic score, which is calculated by non-invasive measurement of corneal riboflavin concentration and its UV-A light mediated photo-degradation. ARGO is a randomized multicenter clinical trial in patients aged between 18 and 40 years with progressive keratoconus aiming to validate the theranostic score by assessing the change of the maximum keratometry point value at 1-year postoperatively. A total of 50 participants will be stratified with allocation ratio 1:1 using a computer-generated stratification plan with blocks in two treatment protocols, such as epithelium-off or epithelium-on CXL. Following treatment, participants will be monitored for 12 months. Assessment of safety and performance of theranostic-guided corneal cross-linking treatment modality will be determined objectively by corneal tomography, corneal endothelial microscopy, visual acuity testing and slit-lamp eye examination.

Partial-thickness compression sutures without descemetopexy for management of acute hydrops in keratoconus: A novel surgical technique.

This article reports a novel surgical technique of partial-thickness compression sutures without descemetopexy with air or gas for the management of acute hydrops in keratoconus. Two patients presented with localized corneal edema with a Descemet membrane (DM) tear in the left eye. Tomography of the right eye revealed localized steepening with increased maximum keratometry and decreased central pachymetry. They were diagnosed with keratoconus in the right eye and acute corneal hydrops (ACH) in the left eye. Compression sutures were passed through the stroma without touching the DM. The anterior chamber was not entered at all at any point during the surgery. Resolution of edema was noted intraoperatively itself. Further resolution of edema was noted from the first postoperative day which markedly reduced within the first week. A corneal scar with no edema was seen at six weeks. In both the patients, vision at presentation was counting fingers close to face which improved to 20/60 and 20/50, respectively, at the last visit.

Long-Term Follow-Up of a 150° Arc-Length Intrastromal Corneal Ring Segment Implantation in Post-LASIK Ectasia

Purpose To evaluate the outcomes of implanting a 150° arc-length intrastromal corneal ring segment (ICRS) using a femtosecond laser in patients with post-LASIK ectasia throughout a 5-year follow-up period. Methods This study enrolled 45 eyes of 45 patients diagnosed with post-LASIK ectasia who underwent a 150° arc-length Ferrara-type ICRS implantation. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, residual refractive errors, and root mean square (RMS) for coma-like aberration were evaluated preoperatively and at 6-, 12-, 36, and 60 months postoperatively. Results Mean UDVA (logMAR) ameliorated from 0.53 ± 0.33 preoperatively to 0.26 ± 0.24 at 6 months postoperatively (p < 0.0001). Mean CDVA improved from 0.12 ± 0.13 to 0.04 ± 0.06 (p < 0.0001). Mean UDVA and CDVA remained stable throughout the 5-year follow-up (p > 0.1). No eyes lost lines of CDVA at any follow-up visit compared to preoperatively, and most eyes gained lines. The eyes with a refractive cylinder ≤ 2.00 D varied from 26.7% preoperatively to more than 75% at all postoperative follow-up visits. The maximum keratometry was significantly flattened (p < 0.0001), and the RMS for corneal coma-like aberration was halved (p < 0.0001). 93.3% of the eyes did not show signs of disease progression or regression of the visual or refractive outcomes at any follow-up visits. Conclusion These results suggest that implanting a single 150° arc-length Ferrara-type ICRS is a safe, effective and stable procedure for visual restoration in post-LASIK ectasia. In very few cases, visual and/or refractive instability was experienced throughout the follow-up.

Evaluation of Corneal Parameters and Meibomian Gland Alterations After Corneal Cross-Linking in Patients With Progressive Keratoconus.

The aim of the study was to evaluate the changes in corneal parameters and meibomian gland alterations after corneal cross-linking (CXL) for progressive keratoconus. Thirty nine eyes of 39 keratoconus patients were treated with CXL. Corneal topography, specular microscopy, the Ocular Surface Disease Index© (OSDI), noninvasive tear break-up time (NITBUT), and meibography indices were evaluated preoperatively and at the first, third, and sixth months after CXL. The flattest keratometry (K1) ( P =0.003), steepest keratometry (K2) ( P <0.001), apex, central, and thinnest corneal thicknesses ( P <0.001) showed significant differences after cross-linking, whereas the changes in the maximum keratometry (Kmax) were not significant ( P =0.140). The endothelial cell density, coefficient of variation, and hexagonality were unchanged. The NITBUT values decreased after cross-linking; however, there was no significant change in OSDI index ( P =0.313), meiboscore ( P =0.392), and meibomian gland loss degrees ( P =0.300). No change was detected in the morphology of the meibomian glands after CXL. In eyes with keratoconus, a flattening in keratometry readings and thinning in corneal thickness were observed after CXL. The corneal endothelium is protected by dextran-free riboflavin. Cross-linking procedure causes dry eye by changing the corneal structure without affecting the morphology of the meibomian glands.

Femtosecond laser-assisted Bowman layer transplantation for advanced keratoconus.

To assess the technical feasibility and outcomes of femtosecond laser-assisted Bowman layer transplantation (FLABOLT) in stabilizing progressive, advanced keratoconus, which is ineligible for corneal crosslinking. This single-center retrospective study included 50 eyes of 49 patients with progressive advanced keratoconus, ineligible for corneal crosslinking, that underwent FLABOLT with both the donor graft and recipient mid-stromal pocket using a femtosecond laser. The mean follow-up was 13.2 ± 4.9 months (range 7-35 months). Donor graft preparation and accurate dissection of the recipient mid-stromal pocket were successful in 96% and 100% of cases, respectively. The mean maximum keratometry decreased by 1.93 D at 6 months after surgery and there was no change in the mean preoperative best contact lens-corrected visual acuity (BCLVA). Three eyes developed hydrops postoperatively and recovered after clinical treatment. One eye that achieved useful BCLVA postoperatively, worsened 2 years after the surgery due to progressive corneal scarring and required corneal transplantation for visual rehabilitation. Preoperative corneal scarring was a risk factor for BCLVA loss. All other eyes remained stable (92%), and no other procedure was required until the last follow-up. In this series, FLABOLT was successfully performed as an alternative to stabilize advanced progressive keratoconus. This technique is highly reproducible for graft preparation and recipient pocket dissection when assisted by femtosecond laser. Despite promising initial results, more studies with longer follow-up periods are needed to evaluate the effectiveness of FLABOLT in stabilizing advanced progressive keratoconus.

Interethnic differences in post-procedural outcomes of corneal crosslinking for progressive keratoconus: A longitudinal cohort study

Purpose To assess interethnic differences in the prevalence of keratoconus and identify interethnic differences in safety and efficacy of crosslinking. Methods Participants diagnosed with progressive keratoconus and that received crosslinking treatment between January 1st 2012 and October 31st 2019, were included in this study. Participants received 12 months follow-up at the tertiary ophthalmology treatment centre of the University Medical Centre Utrecht (Utrecht, The Netherlands). A questionnaire addressing ethnicity, consanguinity, and educational level was conducted. Thinnest pachymetry and maximum keratometry values were chosen as indices for disease progression. A mixed effect model was used to examine associations between ethnicity, baseline clinical parameters, and treatment efficacy. Fisher’s exact test was used to identify differences in post-operative complications. Results 467 eyes of 318 patients were identified and considered eligible for analysis. At baseline North African and South American subjects were relatively over-represented (χ2, P &lt; 0.001). Compared to Europeans, no ethnicity showed a significantly different disease progression 12-months post-crosslinking (P &gt; 0.05). The overall post-operative complications rate was 3.2% (n = 15). There was no statistically significant difference in the number of infiltrates, persistent stromal scars, re-crosslinking or corneal transplantation between the ethnic groups and the European reference group (All P &gt; 0.05). Conclusion Despite the relative overrepresentation of non-European patients at our keratoconus treatment centre, this study reports no differences between Middle Eastern, North African, Sub-Saharan African, South American, Caribbean, Asian ethnic groups and a European reference group after crosslinking for progressive keratoconus in terms of complication rates, keratometry progression, or corneal thinning at 12-month follow-up.

Recurrent Keratoconus: Corneal Transplants for Keratoconus Develop Tomographic Ectatic Changes.

The purpose of this study was to evaluate postoperative Scheimpflug imaging changes during the first 5 years after penetrating keratoplasty (PK) in patients with keratoconus (KC). This retrospective, interventional case series includes 31 eyes of 31 patients who underwent their first PK with a history of KC. Postoperative Scheimpflug imaging was performed 3 months after the removal of the last suture (baseline) and then repeated 3 and 5 years after the PK. Demographic data, donor and host trephination diameter, and Scheimpflug imaging (Pentacam HR, Oculus, Germany) parameters indicative of ectasia were analyzed to evaluate postoperative graft changes that occur after PK. The maximal keratometry (Kmax) progressed significantly between baseline (53.5 ± 6.1 D) and postoperative year 3 and year 5 [56.5 ± 6.1 diopter (D) and 58.8 ± 7.9 D, P < 0.001]. Significant changes were also observed for the anterior best fit sphere and posterior best fit sphere ( P < 0.001 for 3 and 5 years compared with baseline). Kmax increased by at least 2 Ds for 74.2% of patients and up to 7 Ds or more for 25.8% of the patients. A significant inverse correlation was observed for host trephine size and progression of Kmax (r = -0.52, P = 0.01), which indicated that larger host trephination size was associated with a smaller increase in postoperative Kmax. Tomographic graft changes indicative of ectasia were observed within 3 to 5 years after PK in patients with KC. These changes were observed more frequently and sooner after corneal transplants than previously reported.

Role of Corneal Epithelial Measurements in Differentiating Eyes with Stable Keratoconus from Eyes that Are Progressing

To evaluate measures of corneal epithelium in eyes that showed documented signs of keratoconus (KC) progression and compare with stable eyes and healthy controls. Also, to determine the correlation of these epithelial parameters with maximum keratometry (K max) and pachymetry. Prospective, observational, comparative study. One-hundred and fifty eyes from 150 patients. The study included 50 eyes from patients with documented KC progression, 50 eyes with stable KC, and 50 clinically normal eyes to serve as controls. A spectral-domain (SD)-OCT imaging was obtained in all eyes, and mean values were compared between the groups. The correlation of epithelial parameters with K max and thinnest pachymetry was also investigated. For the purposes of this study, the epithelial measures maximum, minimum, superior, and inferior values as well as the difference between the minimum and maximum (min-max) and epithelial standard deviation were considered, obtained from SD-OCT and compared between groups. Measurements of the thinnest point and min-max in pachymetry were also recorded. The only epithelial parameter that presented a statistically significant difference between stable and progressive KC was epithelium min-max. Although stable KC presented epithelium min-max mean values of-18.2 ± 6.6, progressive KC eyes presented mean values of-23.4 ± 10.3 (P < 0.0001). Epithelial maximum (P= 0.16), minimum (P= 0.25), superior (P= 0.28), inferior (P= 0.23), and standard deviation (P= 0.25) values were not significantly different between stable and progressive eyes. Difference min-max pachymetry points in stable (-108.3 ± 33.5) and progressive KC (-115.2 ± 56.0) were not significantly different (P= 0.723). There was no significant correlation between epithelium min-max with corneal thinning (P= 0.39) or K max (P= 0.09) regardless of disease progression. Epithelial measures are useful to identify KC eyes that are progressing; the parameters that measure the difference between min-max epithelium points were significantly different between stable and progressive groups, unlike this difference in pachymetry. Finally, this epithelial parameter seems to be independent of corneal thinning and K max. Proprietary or commercial disclosure may be found after the references.

The Characteristics of Quick Contrast Sensitivity Function in Keratoconus and Its Correlation with Corneal Topography.

To characterize quick contrast sensitivity function (qCSF) in keratoconus and its correlation with corneal topographic parameters. Patients with keratoconus (n = 120) who visited the Fudan Eye and ENT Hospital between April and June 2021 were enrolled in our study. A total of 215 eyes were subdivided into three groups according to maximum keratometry (Kmax): Group1 (Kmax ≤ 48D, 74 eyes), Group2 (48D < Kmax ≤ 55D, 64 eyes), and Group3 (Kmax > 55D, 77 eyes). Manifest refraction, best corrected distance visual acuity (BCVA), corneal topography, and the qCSF test were examined. Intergroup comparisons and correlations among various corneal topographic parameters and qCSF were analyzed. Significant differences in the area under the logCSF (AULCSF) and CSF Acuity among the three groups were found, which decreased with an increase in Kmax. Contrast sensitivity (CS) between spatial frequencies of 3.0 to 18.0cpd was significantly different (all P < 0.05) between Groups1 and 2. The CS at all spatial frequencies was significantly different (all P < 0.05) between Group3 and other two groups. At 3.0-18.0cpd, CS decreased significantly (all P < 0.05) in Groups1-3. Manifest refraction and topographic indices correlated significantly with qCSF parameters (all P < 0.05). Multivariable linear regression analysis showed that cylindrical refraction, logMAR BCVA, and index of surface variance had good predictive values for AULCSF and CSF Acuity. The use of qCSF test can serve as a feasible tool to evaluate visual quality and severity of keratoconus, since changes in CS significantly correlated with keratoconus severity.

Progressive Flattening after Corneal Collagen Crosslinking: A 10-Year Follow-Up

Purpose: This study aimed to demonstrate the importance of long-term follow-up after corneal collagen crosslinking. Methods: This case report showed an intense progressive flattening of keratometric parameters in a patient without risk factors such as high maximum keratometry, thin cornea, uncontrolled ocular allergy, collagen, or rheumatologic diseases. Even with significant haze formation and progressive flattening, the patient exhibited progression after a long follow-up period. Results: The patient presented with grade 2 haze associated with progressive flattening of approximately 10 D in keratometric parameters (Kmax, K1, K2, and Kmean) during the first 5 years after surgery. Corneal opacity altered the minimum pachymetry reading on Pentacam to 265 microns. Anterior corneal follow-up optical coherence tomography revealed a thickness of 453 microns. The patient developed low visual acuity while wearing glasses. The scleral lens was fitted, allowing a visual acuity of 20/30, with satisfactory visual quality. Keratometric stability was observed between the fifth and tenth year. In the tenth year, the patient maintained haze, but there was a progression of 1.7 D in the Pentacam comparative map. Conclusions: Long-term monitoring after corneal crosslinking should be performed. Eyes with haze and intense progressive flattening may fail after a long period.

Reliability analysis of successive Corvis ST® measurements in keratoconus 2 years after accelerated corneal crosslinking compared to untreated keratoconus corneas

PurposeTo assess the reliability of successive Corvis ST® measurements (CST, Oculus, Wetzlar, Germany) in keratoconus (KC) ≥ 2 years after accelerated corneal crosslinking (9 mW/cm2, 10 min, 5.4 J/cm2) compared to untreated KC corneas.MethodsThree successive CST measurements per eye were performed in ≥ 2 years after CXL (CXLG, n = 20 corneas of 16 patients) and a control group consisting of non-operated, ABC-stage-matched KC corneas according to Belin’s ABCD KC grading (controls, n = 20 corneas, 20 patients). Main outcome measures included maximal keratometry (Kmax), the Belin/Ambrósio-Enhanced-Ectasia-Deviation-Index BAD-D; the biomechanical parameters A1 velocity, deformation amplitude (DA) ratio 2 mm, Ambrósio relational thickness to the horizontal profile (ARTh), integrated radius, stiffness parameter A1 (SP-A1), and the Corvis Biomechanical Factor (CBiF, the linearized term of the Corvis Biomechanical Index). Mean values, standard deviations, and Cronbach’s alpha (CA) were calculated.ResultsBoth groups were tomographically comparable (BAD: 11.5 ± 4.7|11.2 ± 3.6, p = 0.682, Kmax: 60.5 ± 7.2|60.7 ± 7.7, p = 0.868 for controls|CXLG, paired t-test). A1 velocity (mean ± SD: 0.176 ± 0.02|0.183 ± 0.02, p = 0.090, CA: 0.960|0.960), DA ratio 2 mm (6.04 ± 1.13|6.14 ± 1.03, p = 0.490, CA: 0.967|0.967), integrated radius (12.08 ± 2.5|12.42 ± 1.9, p = 0.450, CA: 0.976|0.976), and CBiF (4.62 ± 0.6|4.62 ± 0.4, p = 0.830, CA: 0.965|0.965) were also comparable (controls|CXLG). ARTh was significantly higher in controls (177.1 ± 59, CA: 0.993) than after CXL (155.21 ± 65, p = 0.0062, CA: 0.993) and SP-A1 was significantly higher after CXL (59.2 ± 13, CA: 0.912) than in controls (52.2 ± 16, p = 0.0018, CA: 0.912).ConclusionARTh and SP-A1 differed significantly between controls and CXLG. Biomechanical measurements were generally of excellent reliability in both groups. CXL seems to affect biomechanical measurements of human corneas over more than 2 years.

Long-Term Results of Laser In Situ Keratomileusis in Myopic Patients with Topographic Indices outside Suggested Ranges.

To investigate the long-term results of laser in situ keratomileusis (LASIK) in patients with one or more topographic indices outside the suggested range preoperatively. Patients who had conventional or femtosecond laser-assisted LASIK for myopia correction between 2011 and 2015, and had at least one preoperative corneal topographic index outside the suggested range were contacted for a follow-up examination. Ranges were based on the cutoffs suggested for subclinical keratoconus: thinnest pachymetry (TP) < 497.50µm, maximum keratometry (Kmax) > 47.20D, maximum 8mm best-fit-sphere anterior elevation (MaxAE) > 9.50µm, maximum 8mm best-fit-sphere posterior elevation (MaxPE) > 20.50µm, and Belin/Ambrósio enhanced ectasia display-total deviation (BAD-D) > 1.60. Two hundred thirty patients (377 eyes) were enrolled; their mean age at baseline and at follow-up was 30.78 ± 8.16 and 9.06 ± 1.91years, respectively. Mean ± SD was 484.36 ± 11.49 for TP (n = 133), 48.17 ± 0.83 for Kmax (n = 133), 16.33 ± 5.39 for MaxAE (n = 35), 27.87 ± 7.86 for MaxPE (n = 34), and 1.97 ± 0.36 for BAD-D (n = 162). Post-LASIK and suspected ectasia was found in one (0.26%) and two (0.53%) eyes, respectively. In the remaining 374, the efficacy and safety indices were 0.96 ± 0.14 and 1.01 ± 0.08, respectively. Uncorrected distance visual acuity (UDVA) was not reduced in any eyes, and corrected distance visual acuity (CDVA) was reduced one line in 1.9% of the cases; 79.9% of the cases were emmetropic. The long-term changes in UDVA, CDVA, and spherical equivalent were not different between groups with one, two, or three out-of-range topographic indices (all P > 0.05). A single out-of-range topographic index is not a strong predictor for postoperative complications, and one should consider the combination of topographic and clinical findings, or the pattern they create in tandem. Developing a scoring system that would take a combination of indices and topographic patterns may help improve the predictive accuracy of these indices.

Clinical Outcomes Comparison of Combined Small Incision Lenticule Extraction with Collagen Cross-Linking Versus Small Incision Lenticule Extraction Only.

Purpose To evaluate clinical outcome during 24 months follow-up between small incision lenticule extraction combined with cross-linking (SMILE Xtra) and small incision lenticule extraction (SMILE) only. Setting. Ophthalmology Division of San Rossore Medical Center, Pisa, Italy. Design Retrospective comparative case series. Methods The study comprised 70 eyes (35 patients); 40 eyes were corrected using SMILE and 30 eyes were corrected using SMILE Xtra using a low energy protocol. The outcomes were compared at 1, 6, 12, and 24 months postoperatively. Results The mean spherical equivalent (SEQ) reduced from −7.18 ± 1.21 D to −0.01 ± 0.09 D in the SMILE group and from −6.20 ± 2.99 D to −0.04 ± 0.1 D postoperatively in SMILE Xtra (p < 0.05). At 24 months the mean SEQs were −0.01 ± 0.24 D for SMILE and −0.15 ± 0.33 D for SMILE Xtra (p > 0.05). At 1, 6, 12, and 24 months, there were no statistically significant differences between the SMILE and SMILE Xtra groups in logarithm of the minimum angle of resolution (logMAR) uncorrected distance visual acuity (UDVA), safety, and efficacy index (p > 0.05). The mean average keratometry (K-avg) at 1, 6, 12, and 24 months after surgery did not shown any statistically significant difference between SMILE and SMILE Xtra group (p > 0.05). The mean maximum keratometry (K-max) readings at 1, 6, 12, and 24 months were not statistically significant between SMILE and SMILE Xtra group (p > 0.05). The preoperative mean thinnest point pachymetry (TTP) was 543.90 ± 22.85 μm in the SMILE group and 523.40 ± 37.01 μm in the SMILE Xtra group (p < 0.05). At 1, 6, 12, and 24 months the mean TTP was not statistically significant between the SMILE and SMILE Xtra groups (p > 0.05). At 24 months, the TTP was 408.29 ± 38.75 μm for the SMILE group and 402.22 ± 37 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the mean maximum posterior elevation (MPE) was 8.63 ± 4.35 μm for SMILE and 8.13 ± 2.54 μm for SMILE Xtra (p > 0.05). After the surgical procedure, both groups showed a statistically significant increase of the MPE (p < 0.05). At 24 months, the MPE was 11.00 ± 4.72 μm for SMILE Xtra and 10.14 ± 3.85 μm for the SMILE group (p > 0.05). In the preoperative period, the means of the root mean square (RMS) of high-order aberration (HOA) were 0.08 ± 0.03 μm for the SMILE group and 0.08 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the RMS of HOA was 0.13 ± 0.07 μm for the SMILE group and 0.14 ± 0.07 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the root mean square of coma aberration (RMS-Coma) aberration was 0.06 ± 0.09 μm for the SMILE group and 0.04 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the coma aberration of SMILE group was 0.12 ± 0.21 μm and 0.16 ± 0.25 μm for SMILE Xtra group (p > 0.05). Conclusions SMILE Xtra procedure is a safe and simple procedure that can be offered to patients with high corneal ectasia risk because there were no differences in the indices of ectasia compared to the group treated only with SMILE which has a low corneal ectatic risk.

Role of Corneal Collagen Cross Linking in Halting the Progression of Keratoconus: A Contralateral Eye Study

Objective: To assess the efficacy of Corneal Collagen Cross-Linking in preventing the progression of Keratoconus by comparing changes in Maximum Simulated Keratometry (K-max) in treated and untreated eye of the same patient. Methodology: All the cases, that met the inclusion/exclusion criteria (with complete pre-operative examinations), were enrolled in the study. Patients gave informed permission. In each patient, a computerized random number table was used to pick one eye for treatment and the other as a control. Patients were told to stop wearing hard contact lenses 3 weeks before the treatment and soft lenses 1 week before. After pre-op assessment, the selected eye underwent CXL. To control bias, only one experienced surgeon carried out the procedure and a thorough examination was done at 1st post-op day, 01 week, 01, 03 and 4 months after CXL. Main outcome measure during follow up was K-max as measured by Corneal Topography using Galilei G4. One experienced person performed corneal topography for all eyes to control bias. Results: In our study, mean age was 20.55+6.27 years, 60.61%(n=20) were male while 39.39%(n=13) were females. Comparison of the efficacy of corneal collagen cross-linking in preventing the progression of keratoconus by comparing changes in maximum simulated keratometry (K-max) in treated and untreated eyes of the same patient shows that 96.97%(n=32) in CXL and 3.03%(n=1) in control group showed efficacy whereas remaining 3.03%(n=1) in CXL and 96.97%(n=32) in control group had no efficacy, p value was 0.000. Conclusion: We concluded that Corneal Collagen Cross Linking is significantly effective in preventing increase in K-max when compared with the control group. Keywords: Keratoconus, Maximum Simulated Keratometry, Corneal Collagen Cross-Linking, Efficacy

Corneal characteristics in Down syndrome patients with normal and keratoconic cornea.

PurposeTo determine the reference range of corneal indices in Down syndrome patients with normal corneas (DS-N) and to compare it with the corneal indices in Down syndrome patients with keratoconic corneas (DS-KC).MethodsA study was conducted using the data of 154 eyes of 154 DS-N and 25 eyes of 25 DS-KC patients. Eighteen indices related to thickness, anterior chamber, keratometry, elevation, and aberrations routinely used for KC diagnosis were extracted from the Pentacam.ResultsThe mean age of the participants in DS-N and DS-KC groups was 16.73 ± 4.70 and 16.56 ± 4.22 years (P = 0.852). In the DS-N group, 95% CI were 511.65–520.31 for minimum corneal thickness, 2.97–3.07 for anterior chamber depth (ACD), 46.83–47.37 for maximum keratometry (Kmax), 46.13–46.62 for zonal Kmax at 3 mm, 0.35–0.58 for inferior-superior asymmetry (I-S value), 1.56–1.88 for Belin/Ambrósio display-total deviation, 8.65–10.79 for best-fit-sphere posterior elevation at the thinnest point, and 0.18–0.22 for corneal vertical coma. The age-related change in I-S value and corneal spherical aberration (SA) was significant (both P < 0.05). There were significant inter-gender differences in 11 indices; the female DS patients had shallower, steeper, more elevated, and more aberrated corneas (all P < 0.05). There were significant differences in all indices except for ACD (P = 0.372) and corneal SA (P = 0.169) between DS-N and DS-KC groups.ConclusionIn DS patients aged 10–30 years, the reference ranges of corneal indices are different from the range reported for non-DS subjects and are close to values reported for mild KC non-DS cases. The normal values are different between DS male and female; hence, sex-specific ranges should be considered for diagnosis of corneal abnormality in DS patients.

Comparison of safety and efficacy of silicone hydrogel contact Lens-assisted CXL and accelerated CXL in keratoconus patients with thin corneas.

To evaluate the efficacy and safety of silicone hydrogel contact lens-assisted corneal cross-linking (CL-CXL) and compare 12-month visual and topographic outcomes with accelerated CXL using hypo-osmolar riboflavin (A-CXL) in keratoconus patients with thin corneas (below 400 μm with epithelium). This retrospective study included 27 eyes of 27 keratoconus patients who underwent CL-CXL (n = 14) or A-CXL (n = 13). Uncorrected and corrected distance visual acuity (UDVA and CDVA) and data obtained from corneal topography were analyzed at baseline and again at 6- and 12-month follow-ups. Corneal demarcation line depth (DLD) was measured at one month, and changes in the corneal endothelial cell density (ECD) at 12 months were also assessed. Mean UDVA improved significantly in both groups at 12 months (all p < 0.05). Maximum keratometry (K-max) decreased by 1.04 ± 1.90 D in the CL-CXL group and by 0.87 ± 1.89 D in the A-CXL group at 12 months, which was not statistically significant (all p>0.05). Total corneal higher-order aberrations (HOAs) analysis showed a significant improvement in only the CL-CXL group at 12 months (p = 0.041). Average DLD was 227.18 ± 65.60 μm in the CL-CXL group and 245.30 ± 66.84 μm in the A-CXL group (p = 0.275). No significant change in ECD was found in either group (all p>0.05). Mean changes in UDVA, CDVA, K-max, K-mean, HOAs, and ECD were not statistically significant between the groups (all p>0.05). Silicone hydrogel CL-assisted CXL seems as effective as A-CXL in halting keratoconus progression in thin corneas with no side effects during the one-year follow-up period.

One-year Visual and Refractive Outcomes of Deep Anterior Lamellar Keratoplasty (DALK) in Patients with Advanced Keratoconus.

To determine the one-year visual and refractive outcomes of deep anterior lamellar keratoplasty (DALK) in patients with advanced keratoconus (KC) using inexpensive readily available instruments. An observational study. Department of Cornea and Refractive Surgery, Al-Shifa Trust Eye Hospital, from November 2016 to March 2021. The authors evaluated different types of big bubble (BB) formation and the conversion rate of intended DALK (n=120) to the penetrating keratoplasty (PK) in patients with grade 4 KC. For analysis, only those patients were included in whom DALK was completed. Main outcome measures at 1-year follow-up were best-corrected visual acuity (BCVA), maximum keratometry (Kmax) reading, spherical equivalent (SE), and topographic astigmatism (TA). All the postoperative complications were recorded. Type 1 BB was formed in 68% (n=82) of the patients. An incomplete type 1 BB and type 2 BB were observed in twenty and eighteen patients, respectively. DALK was completed successfully in 102 patients. Whereas, the conversion rate to PK was 15% (n=18). The mean preoperative BCVA improved from 1.11±0.23 logMAR to 0.46±0.20 logMAR, at 1-year follow-up. The mean Kmax, SE, and TA readings reduced from a preoperative value of 62.1±4.60 D, -11.6±2.62 D, and 4.63±1.82 D, respectively, to 49.1±3.10 D, -5.65±0.84 D, and 2.78±1.35 D, respectively, at 1-year follow-up. Stromal rejection was recorded in two patients, but it responded well to topical therapy. Inexpensive readily available instruments can be used to perform DALK in patients with advanced KC with favourable visual and refractive outcomes. Big bubble, Deep anterior lamellar keratoplasty, Keratoconus, Perforation, Penetrating keratoplasty.

Oxygen in Corneal Collagen Crosslinking to Treat Keratoconus: A Systematic Review and Meta-Analysis.

Keratoconus is a disorder that results in visual loss from increased corneal high-order aberrations and irregular astigmatism and reduces quality of life. The primary treatment for progressive keratoconus is crosslinking (CXL). Recently, it has been suggested that oxygen enhances the type II photodynamic reaction of CXL that is oxygen dependent. Our study investigated the effect of increased oxygen availability in epithelium-on CXL on visual acuity and corneal curvature. We searched PubMed, EMBASE, Medline, Web of Science, and Scopus databases on November 3, 2021. We included studies that reported increased oxygen availability during CXL in patients with keratoconus published within the last 10 years. A meta-analysis on the primary outcomes, maximum keratometry, and corrected distance visual acuity, was conducted. The search yielded 108 publications which were screened and assessed for eligibility. Six studies were included in the systematic review and 5 studies were included in our meta-analysis of the outcomes of increased oxygen availability in accelerated CXL. The meta-analysis on data after 6 months of follow-up found a significant decrease in mean maximum keratometry of 1.2 diopter (95% confidence interval: 0.2-2.3; P =0.02) and an improvement in mean corrected distance visual acuity by 0.08 logMAR (95% confidence interval, 0.02-0.13; P =0.01). There were no serious adverse events reported. Increasing oxygen during epithelium-on CXL improved visual acuity and produced corneal flattening without any serious adverse events in patients with keratoconus. The demarcation line depth was significantly higher with oxygen compared to the control group. Further data are required with a control group and long-term follow-up across a range of CXL protocols for implementation into standard clinical practice.

Intrastromal Corneal Ring Segments Implantation After Deep Anterior Lamellar Keratoplasty for Astigmatism Correction: Mid-term and Long-term Follow-up.

The aim of this study was to assess the long-term outcomes of implanting intrastromal corneal ring segments (ICRSs) using a femtosecond laser for correcting astigmatism in patients who had previous deep anterior lamellar keratoplasty (DALK) throughout a 5-year follow-up period. This retrospective study included 40 eyes of 40 patients with previous DALK and astigmatism ≥3.00 D who underwent Ferrara-type ICRS implantation. The manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity (logMAR), and corneal topography were recorded preoperatively and at 6, 12, 36, and 60 months postoperatively. The mean UDVA (logMAR scale) improved from 1.39 ± 0.55 preoperatively to 0.71 ± 0.37 at 6 months postoperatively ( P < 0.0001). The mean CDVA (logMAR) significantly improved from 0.36 ± 0.17 to 0.22 ± 0.12 at 6 months after surgery ( P < 0.0001). Both UDVA and CDVA remained unchanged throughout the follow-up ( P = 0.09). Postoperatively, no eyes lost lines of CDVA compared to preoperatively, and around 80% of the eyes gained lines of CDVA. The safety index remained stable at a value of 1.4 throughout the follow-up. The refractive cylinder decreased from -6.86 ± 2.62 D preoperatively to -2.33 ± 1.09D at 6 months postoperatively ( P < 0.0001), and subsequently, it was stable over the postoperative period ( P = 0.2). The maximum and minimum keratometry measurements significantly decreased after surgery and remained stable over the postoperative follow-up period ( P > 0.07). This study shows the long-term viability of Ferrara-type ICRS implantation using a femtosecond laser as a surgical alternative for astigmatism correction in post-DALK eyes.