Current surgical options for keratoconus

Comparing the natural progression and clinical features of keratoconus between pediatric and adult patients

To present the natural course of keratoconus (KC) and compare pediatric and adult patients. Design A retrospective cohort study. Setting Hospital-based. Patient Population In total, 152 patients (288 eyes) diagnosed with KC at Chang Gung Memorial Hospital, Taiwan, were included. Previously managed patients and those with missing optical data were excluded. Observation Procedures Patients were divided into pediatric (≤ 18 years) and adult (> 18 years) groups. Demographics, clinical data, and optical variables were collected, including corrected distance visual acuity (CDVA), refractive error, and keratometric readings (K). Main Outcome Measure Optical variables at the final follow-up before aggressive treatment. Results In total, 20 pediatric (37 eyes) and 132 adults (251 eyes) patients were eligible for this study. The mean follow-up time was 2.98 years. Male predominance was observed in both groups. Both groups had similar clinical characteristics and optical variables at the initial diagnosis. Pediatric patients progressed significantly more rapidly in refractive errors, including spheres and cylinders, spherical equivalence, steep K, and flat K during the follow-up. However, significant change between the two study groups was only seen in sphere refractive error spherical equivalence. Conclusion Pediatric patients had more rapidly progressive KC than adult patients, so early detection and frequent follow-up for prompt interventions are necessary for these patients.

Need for explantation of an intrastromal titan ring after penetrating keratoplasty in two patients

The most severe complications after penetrating keratoplasty (PKP) include high astigmatism and immunological graft reaction. The introduction of the corneal intrastromal titan ring by Krumeich intended to reduce the incidence of both complications. We present two patients with keratoconus who referred to our department after a PKP combined with the implantation of an intrastromal ring. The first patient suffered from bulbar pain and headaches. The second patient suffered from postoperative high myopia, irregular astigmatism and was contact lens intolerant. In the first patient we recognized anterior movement of the ring inside the stroma and decided to remove it. The second patient was found to have extreme bulging of the transplant. We removed the ring and sequentially performed a repeat-PKP. In both patients the implantation of the ring failed to decrease the postoperative astigmatism and caused symptoms that affected the patients’ everyday life. Therefore, we recommend not to use this titan ring.

Penetrating Keratoplasty versus Deep Anterior Lamellar Keratoplasty for Keratoconus: A Systematic Review and Meta-analysis

Keratoconus is the most common form of primary corneal thinning. Different methods have been suggested to deal with the condition, including glasses, contact lenses, and surgical interventions, like penetrating keratoplasty (PKP) and deep anterior lamellar keratoplasty (DALK), well-known methods of the latter. This study was conducted to compare the outcomes and side effects of the two mentioned keratoplasty techniques. First, we systematically reviewed all original articles studies on PubMed, Scopus, Web of Science, and Embase. Then, the extracted data were pooled and meta-analyzed on each of the intended outcomes. A total of 30 studies were included in which PKP was more commonly performed compared to DALK. We found that adverse outcomes consisting of cataracts, graft rejection, graft failure, High-IOP, and corneal infection, were all more common findings in the PKP groups compared to the DALK groups. However, only for the high-IOP, cataracts, and graft rejection, the analysis of the extracted results demonstrated statistical significance. Overall, the DALK groups demonstrated significantly better results when considering the improvement levels by measuring the Endothelial Cell Count (ECC) and Spherical Equivalent (SE). In addition, though statistically insignificant, the Central Corneal Thickness(CCT), Best Corrected Visual Acuity(BCVA), Topographic Cylinder(TC), Refractive Cylinder values were greater in the PKP groups. Based on our study and with its limitations in mind, we can conclude that DALK can be a relatively safer and more effective procedure. Though, a larger number of high-standard randomized clinical trials still need to be conveyed for more definite conclusions.

A novel method of tunnel creation using intraoperative optical coherence tomography-guided deep anterior lamellar keratoplasty

The big bubble technique has become the technique of choice for performing deep anterior lamellar keratoplasty (DALK) since its inception in 2002. The main challenge with this technique is in achieving a big bubble while preventing inadvertent perforation of the Descemet's membrane. Although femtosecond lasers have increased the safety, accuracy, and predictability of corneal dissection in DALK, the challenge of achieving a big bubble still exists. To overcome this challenge, Zeimer Z8 Femto LDV has launched a new software module for DALK, which has an added advantage of real-time optical coherence tomography-assisted femtosecond tunnel creation for achieving a big bubble.

Corneal supply and the use of technology to reduce its demand: A review

Recovery and access to end-of-life corneal tissue for corneal transplantation, training and research is globally maldistributed. The reasons for the maldistribution are complex and multifaceted, and not well defined or understood. Currently there are few solutions available to effectively address these issues. This review provides an overview of the system, key issues impacting recovery and allocation and emphasises how end-user ophthalmologists and researchers, with support from administrators and the wider sector, can assist in increasing access long-term through sustaining eye banks nationally and globally. We posit that prevention measures and improved surgical techniques, together with the development of novel therapies will play a significant role in reducing demand and enhance the equitable allocation of corneas.

[Intracorneal ring segments in keratoconus management]

Intracorneal ring segments (ICRS), used in the management of keratoconus since the 2000s, have enjoyed significant technological development. Various types of ICRS exist, whose arc length, thickness, and diameter can be chosen according to the desired effect on the spherical equivalent, keratometry and asphericity. Individualized implantation strategies, based on each patient's topographic and tomographic pattern, are constantly evolving. The surgical procedure is standardized, and complications remain very rare. Combined procedures (corneal collagen cross-linking and refractive photokeratectomy±topo-guided, phakic and pseudophakic intraocular lenses) are increasingly used and require a good knowledge of the effect of ICRS alone on the keratoconic cornea. The objective of this review is to summarize clinical practices used in the visual rehabilitation of keratoconic patients using the ICRS+- combined procedures.

Combined corneal cross-linking and 320° intrastromal corneal ring segments in progressive keratoconus: one-year results

BACKGROUND

Intrastromal corneal ring segments (ICRS) attain regularization of corneal surface in keratoconus (KC), while collagen cross-linking (CXL) halts or slows its progression. The long-arc 320° rings combined with CXL may have a dual-benefit synergistic effect of surface regularity and progression halt.

METHODS

This was a prospective case series study including eyes with progressive KC. Femto-assisted 320° ICRS implantation and epi-off CXL 8 weeks later were carried out in all cases. Uncorrected (UCVA) and corrected distance visual acuity (CDVA) were assessed using Snellen's chart, while corneal tomography was evaluated using Scheimpflug imaging. Follow-up was carried out 3, 6, and 12 months after the CXL.

RESULTS

Thirty-two eyes of 32 patients with progressive KC were included, 18 males and 14 females, and the mean age was 23.1 years. According to the Amsler-Krumeich classification, four eyes had stage 1 KC, 20 had stage 2 KC, and eight had stage 3 KC, and UCVA and CDVA improved from 0.1 ± 0.15 and 0.2 ± 0.19 to 0.4 ± 0.2 (P>  0.01) and 0.5 ± 0.2 (P>  0.01) respectively at 12 months. Manifest refraction spherical equivalent was reduced from - 5.6 ± 2.3 to - 1.1 ± 1.3 D at 12 months after the procedure (P>  0.01). In addition, maximum keratometry was significantly reduced from 54.8 to 49.3 diopters (P>  0.01), while the asphericity index (Q value) has changed from - 1.4 to - 0.25 (P>  0.01) after 12 months. No significant differences were detected between central (n = 12) and eccentric (n = 20) KC in all outcomes.

CONCLUSION

The 320° ICRS-CXL protocol has improved the visual and the tomographic outcomes at 1 year in our patients with progressive KC. No differences were detected between central and eccentric cases. Further larger studies could ensure the safety profile of the combined protocol.

Accelerated epithelium-on or accelerated epithelium-off corneal collagen cross-linking: Contralateral comparison study

PURPOSE

The aim of the study is to compare the accelerated epithelial-on corneal collagen cross-linking (epi-on CXL) and accelerated epithelial-off corneal collagen cross-linking (epi-off CXL) in terms of clinical and confocal microscopy results.

MATERIALS AND METHODS

Forty-two eyes of 21 patients with progressive keratoconus and simultaneously undergoing accelerated epi-on CXL in one eye and accelerated epi-off CXL in other eye were evaluated. Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) with spectacle in logMAR and topographic findings (mean keratometry [K _mean] and maximum keratometry [K_max]) were recorded at 1, 3, 6, 12, 18, 24, and 30 months. Eyes were compared in terms of subjective pain scores after the procedures. Furthermore, anterior segment optical coherence tomography and confocal microscopy were performed at 1 month.

RESULTS

K_mean and K_max were less than baseline in both the groups; however, the reduction was significantly higher in epi-off CXL than epi-on CXL eyes at 18 and 30 months. The UCVA and BCVA increased approximately 1 Snellen line at the end of mean follow-up in epi-off CXL and in epi-on CXL. Stromal demarcation line for epi-off CXL is 276.4 ± 58.9 while 148.3 ± 24.8 for epi-on CXL (P = 0.001). Furthermore, subepithelial nerves were observed in any eye in epi-off CXL; however, subepithelial nerves were observed in 12 eyes (80%), in epi-on CXL (P = 0.01).

CONCLUSION

Both techniques were able to stop progression; however, in contrast to expectations, the pain was felt more in epi-on CXL than epi-off CXL.

Evaluation of a Tangential Map-Based Nomogram for Intrastromal Corneal Ring Segments' Implantation in Keratoconus: One Year Results

Purpose

To evaluate a new tangential map-based nomogram versus the axial map-based nomogram for ICRS in keratoconus.

Methods

A prospective case series study including 64 eyes of 64 patients who underwent ICRS implantation. Cone location was determined for each eye with two maps: the axial and the tangential. Appropriate ring selection was determined using two surgical nomograms: axial map-based and tangential map-based. Visual, refractive, and topographic outcomes were assessed before, as well as at 3, 6, and 12 months after ICRS implantation.

Results

The cone location, and consequently the ring selection, was significantly different in the two nomograms with a “centralization tendency” in the tangential map. In the axial group, UDVA and CDVA improved from 0.12 ± 0.04 and 0.24 ± 0.08 to 0.28 ± 0.08 and 0.4 ± 0.1, respectively. Similarly, MRSE substantially decreased from −6.7 ± 3.3 to −1.2 ± 1.1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1P=0.01^∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months, P=0.01^∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months,

Conclusion

The tangential map-based nomogram attained better visual and refractive outcomes at 1 year. In addition, the cone location was significantly different between both maps with a centralization tendency in the tangential one.

Trends in Research Related to Keratoconus From 2009 to 2018: A Bibliometric and Knowledge Mapping Analysis

Supplemental Digital Content is Available in the Text.

Purpose:

To map the publication trends in and explore hotspots of keratoconus research.

Methods:

A bibliometric analysis based on the Web of Science Core Collection was conducted to investigate the publication trends in research related to keratoconus. The records extracted were analyzed, and a knowledge map was constructed using VOSviewer v.1.6.10 to visualize the annual publication number, distribution of countries, international collaborations, author productivity, source journals, intellectual base, and research hotspots in the field of keratoconus.

Results:

In total, 3194 peer-reviewed publications on keratoconus published between 2009 and 2018 were retrieved, and the annual research output increased with time. The United States ranked the highest among the countries with the most publications, and Tehran University of Medical Sciences was the most active institution. JL Alio contributed to the most number of publications on keratoconus, and Cornea was the most prolific journal publishing keratoconus research. The top cited references mainly focused on corneal collagen cross-linking. The keywords formed 6 clusters: 1) pathogenesis of keratoconus, 2) corneal collagen cross-linking, 3) management for early-stage keratoconus, 4) corneal parameter measurement, 5) surgical treatment of keratoconus, and 6) corneal biomechanics-related research.

Conclusions:

On the basis of the data extracted from the Web of Science Core Collection, the quantity and quality of publications on keratoconus were assessed using bibliometric techniques. The cited references and research hotspots could provide insights into keratoconus research as well as valuable information to cornea specialists for performing research in this field and discovering potential collaborators.

Keratoconus Asymmetry between Both Eyes Based on Corneal Tomography

PURPOSE

To characterize the asymmetry between both eyes in patients with keratoconus based on corneal tomography.

MATERIALS AND METHODS

All patients with keratoconus who presented to the eye clinic at Jordan University Hospital between January 2008 and November 2011 were included in the study. Using computerized corneal tomography, the keratometric values and indices of both eyes of participants with keratoconus and normal controls were compared. For both eyes to be considered symmetrical, the difference between the mean curvature power (Km), flat curvature power (K1), or steep curvature power (K2) in both eyes was equal to or <2.5 diopters, and the difference between the thinnest corneal points was equal to or <25.0 μm between both eyes.

RESULTS

Ninety-eight patients with keratoconus and 49 normal participants were evaluated. The mean age of the participants was 26.3 ± 6.6 years. The results showed two populations of patients with keratoconus: one with asymmetrical corneas who were more affected by the disease and another with symmetrical corneas. As the disease severity increased, the differences between the two eyes increased for patients with the asymmetrical form, while both corneas of patients with the symmetrical form were similar.

CONCLUSIONS

Corneal tomography identified two forms of keratoconus: symmetrical and asymmetrical. The latter tended to be more severe and occurred in a younger age group. Questions remain about whether the two keratoconic forms are specific to the Middle Eastern population and whether there are ethnic or demographic forms of the disease.

Topographic typology in a consecutive series of refractive surgery candidates

PURPOSE

The term 'keratoconus (KC) suspect' is used as a blanket term to refer to any deviation of virgin cornea shape toward KC features. We intend to subclassify such topographies in meaningful and informative designations.

METHODS

Pentacam corneal topographies of 199 consecutive refractive surgery candidates (398 eyes) are examined. Features of steepness, inferior-superior asymmetry, focal steepening, thinning, and bounded anterior or posterior elevations are observed in the quad map. Scissoring on retinoscopy, loss of best spectacle-corrected visual acuity, and iron ring deposition were looked for. Through iterative observation and refinement of classification criteria-partly taken from the literature-all eyes were designated a specific topographic diagnosis, i.e., circumventing the usage of the expression KC 'suspect'.

RESULTS

Topographies of 308, 48, 21, 13, 6, 1, and 1 (collectively 398 eyes) were designated: normal, 'atypical normal,' forme fruste KC, posterior KC, subclinical/mild KC, superior KC, and pseudo-KC, respectively.

CONCLUSION

Current imaging modalities of the cornea and our accumulated experience in refractive science allow assignment of distinctive designations for abnormal corneal shapes along the topography spectrum. We devised and used the expressions: normal, atypical normal, forme fruste (arrested-incomplete) KC, posterior KC, subclinical (active latent) KC, superior KC, and pseudo-keratoconus. Identification of 1.5% (mild) KC highlights the importance of screening for ultraviolet cross-linkage candidacy in refractive surgery referrals.

The Superficial Stromal Scar Formation Mechanism in Keratoconus: A Study Using Laser Scanning In Vivo Confocal Microscopy

To investigate the mechanism of superficial stromal scarring in advanced keratoconus using confocal microscopy, the keratocyte density, distribution, micromorphology of corneal stroma, and SNP in three groups were observed. Eight corneal buttons of advanced keratoconus were examined by immunohistochemistry. The keratocyte densities in the sub-Bowman's stroma, anterior stroma, and posterior stroma and the mean SNP density were significantly different among the three groups. In the mild-to-moderate keratoconus group, activated keratocyte nuclei and comparatively highly reflective ECM were seen in the sub-Bowman's stroma, while fibrotic structures with comparatively high reflection were visible in the anterior stroma in advanced keratoconus. The alternating dark and light bands in the anterior stroma of the mild-to-moderate keratoconus group showed great variability in width and direction. The wide bands were localized mostly in the posterior stroma that corresponded to the Vogt striae in keratoconus and involved the anterior stroma only in advanced keratoconus. Histopathologically, high immunogenicity of α-SMA, vimentin, and FAP was expressed in the region of superficial stromal scarring. In vivo confocal microscopy revealed microstructural changes in the keratoconic cone. The activation of superficial keratocytes and abnormal remodeling of ECM may both play a key role in the superficial stromal scar formation in advanced keratoconus.

The Role of the Reactive Oxygen Species and Oxidative Stress in the Pathomechanism of the Age-Related Ocular Diseases and Other Pathologies of the Anterior and Posterior Eye Segments in Adults

The reactive oxygen species (ROS) form under normal physiological conditions and may have both beneficial and harmful role. We search the literature and current knowledge in the aspect of ROS participation in the pathogenesis of anterior and posterior eye segment diseases in adults. ROS take part in the pathogenesis of keratoconus, Fuchs endothelial corneal dystrophy, and granular corneal dystrophy type 2, stimulating apoptosis of corneal cells. ROS play a role in the pathogenesis of glaucoma stimulating apoptotic and inflammatory pathways on the level of the trabecular meshwork and promoting retinal ganglion cells apoptosis and glial dysfunction in the posterior eye segment. ROS play a role in the pathogenesis of Leber's hereditary optic neuropathy and traumatic optic neuropathy. ROS induce apoptosis of human lens epithelial cells. ROS promote apoptosis of vascular and neuronal cells and stimulate inflammation and pathological angiogenesis in the course of diabetic retinopathy. ROS are associated with the pathophysiological parainflammation and autophagy process in the course of the age-related macular degeneration.

A study comparing standard and transepithelial collagen cross-linking riboflavin solutions: epithelial findings and pain scores

PURPOSE

To evaluate epithelial signs and pain after epithelial-on corneal collagen cross-linking (Epi-on CCL) with new transepithelial riboflavin formulation and epithelial-off corneal collagen cross-linking (Epi-off CCL) with standard riboflavin formulation and to compare pain and duration of epithelial healing between both techniques.

METHODS

Thirty-nine eyes of 39 patients undergoing Epi-on CCL and 39 eyes of 39 patients undergoing Epi-off CCL were evaluated. Corneal epithelial signs and durations of corneal epithelial healing and subjective pain scores after the procedures were recorded and compared between 2 groups.

RESULTS

Total epithelialization was observed after 2.7 ± 0.7 days in Epi-on CCL and 2.3 ± 0.4 days in Epi-off CCL (P = 0.006). The mean pain score on the first day was 3.1 ± 0.6 in Epi-on CCL and 2.3 ± 0.4 in Epi-off CCL with a significant difference (P = 0.0001).

CONCLUSION

The epithelial damage was observed in both procedures; also, the epithelial healing time was longer in Epi-on CCL and it is of great importance that the patients should have therapeutic contact lenses until the epithelium heals in both procedures. The Epi-off CCL group had less pain scores than the Epi-on CCL group and more pain problems after Epi-on CCL still remains. The patient should be informed about pain, even if the Epi-on CCL procedure was performed.

Comparison of corneal measurements in keratoconic eyes using rotating Scheimpflug camera and scanning-slit topography

AIM

To compare the anterior segment measurements obtained by rotating Scheimpflug camera (Pentacam) and Scanning-slit topography (Orbscan IIz) in keratoconic eyes.

METHODS

A total of 121 patients, 71 males (58.7%) and 50 females (41.3%) (214 eyes) with the diagnosis of keratoconus (KC) were enrolled in this study. Following diagnosis of KC by slit-lamp biomicroscopic examination, central corneal thickness (CCT), thinnest corneal thickness (TCT), anterior chamber depth (ACD), and pupil diameter (PD) were measured by a single examiner using successive instrumentation by Pentacam and Orbscan.

RESULTS

There was no significant difference between the two instruments for the measurement of CCT and TCT. In contrast, scanning-slit topography measured ACD (3.46±0.40 mm vs. 3.38±0.33 mm, P=0.019) and PD (4.97±1.26 mm vs 4.08±1.19 mm, P<0.001) significantly larger than rotating Scheimpflug camera. The two devices made similar measurements for CCT (95% CI: -2.94 to 5.06, P=0.602). However, the mean difference for TCT was -6.28 (95% CI: -10.51 to -2.06, P=0.004) showing a thinner measurement by Orbscan than by Pentacam. In terms of the ACD, the mean difference was 0.08 mm (95% CI: 0.04 to 0.12, P<0.001) with Orbscan giving a slightly larger value than Pentacam. Similarly, Orbscan measurement for PD was longer than Pentacam (95% CI: 0.68 to 1.08, P<0.001).

CONCLUSION

A good agreement was found between Pentacam and Orbscan concerning CCT measurement while comparing scanning-slit topography and rotating Scheimpflug camera there was an underestimation for TCT and overestimation for ACD and PD.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

New microwave thermokeratoplasty and accelerated crosslinking method for keratoconus: results in 24 eyes during a 1-year follow-up

PURPOSE

To evaluate the safety and efficacy of a new microwave thermokeratoplasty procedure combined with accelerated corneal collagen crosslinking (CXL) to improve visual function in patients with keratoconus.

SETTING

Cornea and refractive surgery department, Istanbul, Turkey.

DESIGN

Prospective clinical trial.

METHODS

Patients with keratoconus who had the combined procedure were evaluated over 12 months postoperatively. The main outcome measures were changes in logMAR uncorrected (UDVA) and corrected (CDVA) distance visual acuities and in keratometry (K) values.

RESULTS

The study enrolled 24 eyes of 24 patients aged 18 to 45 years. The attempted corrections ranged from -1.60 to -6.50 diopters (D). The mean preoperative UDVA of 0.66 logMAR ± 0.26 (SD) significantly improved to 0.39 ± 0.21 logMAR 1 month postoperatively. However by 6 months, the mean UDVA had regressed to 0.58 ± 0.21 logMAR. At 12 months, the mean UDVA was 0.62 ± 0.17 logMAR. The mean K value was 49.11 ± 2.43 D preoperatively, 43.50 ± 3.04 D 1 month postoperatively, 47.52 ± 2.99 D at 6 months, and 48.37 ± 3.00 D at 12 months. There were no cases of significant endothelial cell loss or loss of CDVA lines at 12 months.

CONCLUSIONS

The new thermokeratoplasty procedure followed by accelerated CXL produced the desired reduction in K values and improvement in postoperative UDVA without significant side effects. However, the early and complete regression of the thermokeratoplasty effect shows the need for further advancement of this technology.

FINANCIAL DISCLOSURE

Drs. Yilmaz and Marshall are paid consultants to Avedro, Inc. Dr. Muller is president and CEO of Avedro. No other author has a financial or proprietary interest in any material or method mentioned.

Keratoconus: tissue engineering and biomaterials

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.

Evaluation of subbasal nerve morphology and corneal sensation after accelerated corneal collagen cross-linking treatment on keratoconus

PURPOSE

The aim of this study was to report on the evaluation of corneal nerve fiber density and corneal sensation after accelerated corneal collagen cross-linking on keratoconus patients.

METHODS

The study was performed on 30 keratoconus eyes (30 participants: 16 M, 14 F; 17-32 years old) treated with accelerated collagen cross-linking for disease stabilization. Mean outcome measures were corneal sensation evaluation by Cochet-Bonnet esthesiometry and subbasal nerve fiber density assessment by corneal in vivo confocal microscopy. All corneal measurements were performed using scanning slit confocal microscopy (ConfoScan 4, Nidek Technologies, Padova, Italy).

RESULTS

The accelerated corneal collagen cross-linking procedure was performed on 30 eyes of 30 patients (19 right, 63.3%; 11 left, 27.7%). The mean age was 23.93 ± 4. The preoperative mean keratometry, apex keratometry and pachymetry values were 47.19 ± 2.82 D, 56.79 ± 5.39 and 426.1 ± 25.6 μm, respectively. Preoperative mean corneal sensation was 56.3 ± 5.4 mm (with a range from 40 to 60 mm), it was significantly decreased at 1st and 3rd month visit and increased to preoperative values after 6th month visit. Preoperative mean of subbasal nerve fiber density measurements was 22.8 ± 9.7 nerve fiber/mm(2) (with a range of 5-45 mm), it was not still at the preoperative values at 6th month (p = 0.0001), however reached to the preoperative values at 12th month (p = 0.914).

CONCLUSIONS

Subbasal nerve fibers could reach the preoperative values at the 12th month after accelerated corneal collagen cross-linking treatment although the corneal sensation was improved at 6th month. These findings imply that the subjective healing process is faster than the objective evaluation of the keratoconus patients' cornea treated with accelerated corneal collagen cross-linking.

Deficient repair regulatory response to injury in keratoconic stromal cells

BACKGROUND

Keratoconus manifests as a conical protrusion of the cornea and is characterised by stromal thinning. This causes debilitating visual impairment, which may necessitate corneal transplantation. Hypothetically, many of the pathological features in keratoconus may be manifestations of defects in wound healing; however, as the pathobiology remains unclear, therapeutic targets related to disease mechanisms are currently lacking. This study investigated the protein expression of cytokines which may control stromal wound healing and the effect of an induced secondary injury (SI) on stromal cells from ex vivo human keratoconus and control corneas.

METHODS

Total protein was extracted from stromal cells from human keratoconic and non-keratoconic central corneas (n = 12) with (+SI) and without (-SI) an ex vivo corneal incision wound. The levels of interleukin 1 alpha (IL-1α), fibroblast growth factor 2 (FGF-2), nerve growth factor beta (β-NGF), insulin-like growth factor 1 (IGF-1), tumour necrosis factor alpha (TNF-α), epidermal growth factor (EGF), transforming growth factor beta 1 (TGF-β1), platelet-derived growth factor (PDGF) and hepatocyte growth factor (HGF) were quantified using chemiluminescence-based immunoarrays.

RESULTS

In stromal cells from -SI keratoconic corneas (compared with -SI normal corneas), the levels of IL-1α, IGF-1, TNF-α and TGF-β1 were increased and the levels of HGF and β-NGF were reduced. These alterations were also observed in +SI non-keratoconic corneas (compared with -SI non-keratoconic corneas). In stromal cells from +SI keratoconic corneas (compared with -SI keratoconic corneas), the quantities of IL-1α, FGF-2, TNF-a, EGF, TGF-a1 and PDGF were decreased.

CONCLUSION

The repair-modulating milieu in keratoconic corneas appears comparable to that in wounded normal corneas. Moreover, wounded keratoconic corneas may be less capable of orchestrating a normal reparative response. These novel findings may improve our understanding of the pathobiology and may facilitate the identification of potential biological targets and therapeutic agents to advance the clinical management of this disorder.

Comparison of Optical versus Ultrasonic Biometry in Keratoconic Eyes

Purpose. To compare the measurements of optical versus ultrasonic biometry devices in keratoconic eyes. Materials and Methods. Forty-two eyes of 42 keratoconus (KC) patients enrolled in the study were examined. Clinical and demographic characteristics of the patients were noted, and detailed ophthalmological examination was performed. Following Pentacam measurements, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and axial length (AL) were obtained using the Lenstar and US biometer to determine the reproducibility of the measurements between the two devices in keratoconic eyes. The Bland-Altman method was used to describe the agreement between the two devices. Results. The Lenstar could not measure at least one of the biometric properties in one eye and did not automatically give the corrected ACD in 2/3 of our study population. The Lenstar measured CCT (average difference 5.4 ± 19.6 µm; ICC = 0.90; P < 0.001), LT (average difference 0.13 ± 0.17 mm; ICC = 0.67; P < 0.001), and AL (average difference 0.10 ± 0.76 mm; ICC = 0.75; P < 0.001) thinner than US biometer, whereas it measured ACD (average difference 0.18 ± 0.17 mm; ICC = 0.85; P < 0.001) deeper than US biometer in keratoconic eyes. Conclusion. Although the difference between the measurements obtained using the two devices might be clinically acceptable, US biometry and Lenstar should not be used interchangeably for biometric measurements in KC patients.

Paired arcuate and modified circular keratotomy in keratoconus

AIM: To reduce astigmatism, increase corneal volume and improve visual acuity.

METHODS: A retrospective, single-surgeon, single-center, clinic-based study of a surgical procedure on twenty-four eyes of fourteen patients diagnosed with stage III or stage IV keratoconus. Paired arcuate keratotomy coupled with modified circular keratotomy was performed at a single center by a single surgeon as an outpatient procedure with local anaesthetic in a minor surgery room. Modified circular keratotomy was performed 7 mm from the pupillary center with depth of incision ranging between 70% and 90% of corneal thickness. Arcuate keratotomy was performed 2.5 mm from the pupillary center with the depth of incision at 90% of corneal thickness. Angular length of the arcs ranged between 60° and 120° depending on the astigmatic power of the cornea.

RESULTS: Astigmatism decreased in 87.5% of the 24 treated eyes, increased in 8.33% and did not change in 4.17%. Corneal volume increased in 91.66% of the 24 eyes and decreased in 8.34%. Visual acuity improved in 100% of the eyes; there was a mean improvement of 59% from preoperative visual acuity, 8.34% of the treated eyes reaching a visual acuity of 1.0 (20/20) with correction. No complications occurred during or after surgery. No suturing was performed and there was no rupturing at incision sites. There was statistical significance difference between pre.sph against post.sph (P = 0.001). Also between pre.cyl against post.cyl (P = 0.005), there was no significance difference between pre.axis against post.axis (P = 0.05).

CONCLUSION: Paired arcuate keratotomy coupled with modified circular keratotomy should be considered as an intervention before performing keratoplasty.

New clinical pathways for keratoconus

Pre-2000, the clinical management of keratoconus centred on rigid contact lens fitting when spectacle corrected acuity was no longer adequate, and transplantation where contact lens wear failed. Over the last decade, outcome data have accumulated for new interventions including corneal collagen crosslinking, intracorneal ring implantation, topographic phototherapeutic keratectomy, and phakic intraocular lens implantation. We review the current evidence base for these interventions and their place in new management pathways for keratoconus under two key headings: corneal shape stabilisation and visual rehabilitation.

Ophthalmic transplantology: anterior segment of the eye - part I

Background

Transplantology is a quickly developing field of ophthalmology. It currently is able to treat many inherited, degenerative, inflammatory, traumatic, and cancerous diseases. This review outlines recent concepts and methods of treating ocular diseases with tissue and cell grafts. Ocular transplants related to the anterior part of the eye, including the conjunctiva and the cornea, are reviewed in Part 1.

Material/Methods

The scientific literature dated from January 2005 to July 2011 was thoroughly searched using Medline and PubMed. Publications dated 2009, 2010, and 2011 were analyzed in detail. Search terms were as follows: auto-, homo-, heterologous transplantation, eyeball, ocular adnexa, anterior segment of the eye, cornea, lamellar keratoplasty, stem cells, cultured cells. Further data were found at the website of the Eye Bank Association of America.

Results

Nearly all tissues of the anterior segment of the eye (the conjunctiva, sclera, eye muscles, and cornea) are transplanted. Because of the recent significant progress in the field, cornea transplantation was analyzed in more detail, specifically procedures such as limbus grafts and anterior and posterior lamellar keratoplasty. Indications, advantages, and drawbacks of the transplant techniques were also reviewed.

Conclusions

Recent progress in the field of cornea transplants allows treatment at the level of the endothelium and the use of cultured limbal epithelial stem cell grafts. However, compared with previous techniques, modern and multilayered transplant techniques of the cornea require much more expertise and longer training of the surgeon, as well as expensive and technologically advanced equipment. The availability of donor tissue is still the main limitation affecting all transplants. Therefore, cell culturing techniques such as stem cells, as well as artificial cornea projects, seem to be very promising.

Severe corneal vascularization after intacs implantation and rigid contact lens use for the treatment of keratoconus

PURPOSE

To present a case of unilateral development of severe corneal vascularization in the eye of a keratoconic patient implanted with Intacs microthin prescription inserts and concurrent bilateral use of rigid gas permeable (RGP) contact lenses.

METHODS

A 20-year-old male underwent unilateral implantation of Intacs in his right eye for treatment of keratoconus and five years later began the use of RGP contact lens. In the left eye the patient continued the use of RGP contact lens.

RESULTS

Ten years after implantation the patient had developed severe central corneal neovascularization in the eye treated with Intacs implantation that recessed one month after discontinuing contact lens use. In the fellow eye he had developed only mild peripheral neovascularization.

CONCLUSIONS

Central corneal vascularization is a possible side-effect in patients treated with both Intacs implantation and RGP contact lens fitting that necessitates long term follow-up of such patients.

Visual perception changes and optical stability after intracorneal ring segment implantation: comparison between 3 months and 1 year after surgery

PURPOSE

To prospectively evaluate intracorneal ring segment (ICRS) implantation on quality of life (QoL) of patients with keratoconus changes and identify factors responsible.

METHODS

Sixty-nine eyes of 42 keratoconus patients were implanted with the Keraring (Mediphacos, Belo Horizonte, Brazil). Best corrected visual acuity (BCVA), refraction, and steep keratometry were analyzed 3 months and 1 year after surgery. All patients self-administered the National Eye Institute Refractive Error Quality of life instrument at 2 time points: after having worn best correction for at least 30 days since evaluation (mean 4 months after surgery) and 1 year after surgery. To analyze if the use of the appropriate correction at 1 year follow up had any impact on visual acuity and V-QoL, patients were divided into 2 groups: group A (appropriate correction) and B (not appropriate correction).

RESULTS

After 1 year, QoL changes related to scales 'clarity of vision', 'near vision', and 'far vision'. Keratometric values, sphere, and spherical equivalent did not differ significantly between 3 months and 1 year postoperative. Cylinder increase was statistically but not clinically significant. Binocular BCVA did not change 1 year after surgery in group A and showed a clinically significant impairment in group B. A year after surgery, 18 patients did not use correction suggested by a physician 3 months after surgery. QoL was not statistically different 1 year after surgery between group A and group B.

CONCLUSION

Our findings show that the way keratoconic patients see is difficult to analyze using only quantitative and 1-visit metrics. They highlight the importance of patients' self perception and performing longitudinal analysis to consider neural compensation to optical changes from surgery.

Common complications of deep lamellar keratoplasty in the early phase of the learning curve

PURPOSE

To evaluate and record the common complications that face surgeons when they perform their first few series of deep lamellar keratoplasty and measures to avoid these.

SETTING

Dar El Oyoun Hospital, Cairo, Egypt.

METHODS

Retrospective study of the first 40 eyes of 40 patients carried out by two corneal surgeons working in the same center. All patients were planned to undergo a deep anterior lamellar keratoplasty using the big bubble technique. Twelve patients suffered from keratoconus while 28 patients had anterior corneal pathologies. Recorded complications were classified as either intraoperative or postoperative.

RESULTS

Perforation of Descemet's membrane was the most common intraoperative complication. It occurred in nine eyes (22.5%): five eyes (12.5%) had microperforations while four eyes (10%) had macroperforations, three eyes (7.5%) had central perforations, and six eyes (15%) had peripheral perforations. Other complications included incomplete separation of Descemet's membrane and remnants of peripheral stromal tissue. Postoperative complications included double anterior chamber which occurred in four eyes (10%) and Descemet's membrane corrugations. Postoperative astigmatism ranged from 1.25 to 4.5 diopters with a mean of 2.86 diopters in the whole series, but in the six cases with identified residual stroma in the periphery of the host bed, the astigmatism ranged from 2.75 to 4.5 diopters with a mean of 3.62 diopters.

CONCLUSION

Deep lamellar keratoplasty is sensitive to procedural details. Learning the common complications and how to avoid them helps novice surgeons to learn the procedure faster.

Clinical validation of point-source corneal topography in keratoplasty

PURPOSE

To validate the clinical performance of point-source corneal topography (PCT) in postpenetrating keratoplasty (PKP) eyes and to compare it with conventional Placido-based topography.

METHODS

Corneal elevation maps of the anterior corneal surface were obtained from 20 post-PKP corneas using PCT (VU topographer, prototype; VU University Medical Center, Amsterdam, The Netherlands) and Placido-based topography (Keratron, Optikon 2000, Rome, Italy). Corneal surface parameters are calculated in terms of radius and asphericity. Corneal aberrations were characterized using standard Zernike convention. An artificial surface with quadrafoil feature (SUMIPRO, Almelo, The Netherlands) was measured and used as a reference to assess instrument performance compared with the gold standard.

RESULTS

The differences (mean ± std of PCT - Placido) found between the two types of topographers in measurements of post-PKP eyes are 0.02 ± 0.21 mm (p=0.64) for radius of curvature, 0.14 ± 0.49 (p=0.23) for asphericity, -0.19 ± 1.67 μm (p=0.61) for corneal astigmatism, -0.25 ± 1.34 μm (p=0.41) for corneal coma, 0.23 ± 0.82 μm (p=0.23) for corneal trefoil, and 0.15 ± 0.28 μm (p=0.02) for corneal quadrafoil. The PCT measured the artificial surface more accurate (rms error 0.16 μm; 0.12 eq. Dpt.) than the Placido-based topographer (rms error 1.50 μm; 1.15 eq. Dpt.).

CONCLUSIONS

PCT is more accurate than Placido-based topography in measuring quadrafoil aberration.

Femtosecond laser-assisted corneal surgery

PURPOSE OF REVIEW

A look at the recent advances in corneal transplantation surgery using the femtosecond laser technology.

RECENT FINDINGS

The femtosecond laser uses near-infrared light to create photodisruption, a process that allows corneal tissue to be cut at precise depths and in various patterns. Penetrating keratoplasty as well as disease targeted lamellar corneal surgery have been performed using this technology in order to improve surgical outcomes and wound healing. It is now possible to create customized trephination patterns, including 'zig-zag' and 'top-hat', which demonstrate more rapid visual recovery and decreased amounts of astigmatism as compared with conventional blade trephination penetrating keratoplasty. The benefits of these cuts have been extended into the deep anterior lamellar keratoplasty surgery in order to maintain the benefits of the customized cut, whereas preserving the endothelial layer in ectatic and stromal diseases of the cornea.

SUMMARY

Femtosecond laser-assisted corneal surgery is improving traditional outcomes in transplantation. Continued studies using this ultrafast laser may continue to yield new and exciting possibilities in the treatment of corneal disease.

Combined Kerarings and Artisan/Artiflex IOLs in Keratectasia

PURPOSE:To evaluate the results of combined intracorneal ring (Keraring, Mediphacos Ltd) and anterior chamber, iris-fixated, phakic intraocular lens (pIOL) (Artisan and Artiflex, Ophtec BV) implantation in patients with ectatic corneal conditions and secondary high myopic and astigmatic refractive error. METHODS:Ten eyes of eight consecutive patients with different ectatic corneal diseases underwent sequential intracorneal Keraring and iris-fixated pIOL implantation. Two eyes with keratoconus, one eye with pellucid marginal degeneration, and one eye with iatrogenic corneal ectasia were implanted with the Artisan pIOL; six eyes with keratoconus were implanted with the Artiflex pIOL. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), topographic findings, and complications were recorded. RESULTS:Mean UDVA improved from 0.02+/-0.10 pre-operatively to 0.11+/-0.06 after Keraring implantation and to 0.54+/-0.18 after pIOL implantation (P<.001 for all). Mean CDVA improved from 0.18+/-0.12 preoperatively to 0.39+/-0.13 after Keraring implantation and to 0.66+/-0.18 after pIOL implantation (P<.001 for all). Mean MRSE reduced from -12.50+/-6.31 D preoperatively to +/-12.08+/-5.17 D after Keraring implantation (P=.10) and to -0.10+/-0.84 D after pIOL implantation (P<.001). No intra- or postoperative complications were observed. CONCLUSIONS:Sequential intracorneal Keraring segments and Artisan/Artiflex pIOL implantation resulted in visual and refractive improvements in patients with different corneal ectatic conditions with high myopic refractive errors.

Deep anterior lamellar keratoplasty performed with the femtosecond laser zigzag incision for the treatment of stromal corneal pathology and ectatic disease

We describe a variation of the big-bubble deep anterior lamellar keratoplasty (DALK) technique using the femtosecond laser zigzag incision. This technique allows precise depth visualization for air-needle placement in the posterior stroma based on the lamellar and posterior laser cuts, thus minimizing the risk for perforation of Descemet membrane. The matching donor and host tissue zigzag cut allows more precise tissue apposition and greater surface area for healing. The angled anterior donor and host junction allows a smooth transition for improved visual outcomes. If the big-bubble- Descemet membrane dissection fails, the surgeon can convert to a full-thickness graft while retaining the benefits of the femtosecond laser incision.

Inadequate results for microkeratome-assisted additive stromal keratoplasty for management of keratoconus

PURPOSE

To evaluate a new automated technique--microkeratome-assisted additive stromal keratoplasty (MASK)--for the management of keratoconus in eyes scheduled for surgery with clear cornea associated with total contact lens intolerance.

METHODS

This non-comparative, interventional case series included four eyes of four patients with stage I and II keratoconus associated with total contact lens intolerance. The first step of the surgical procedure consisted of performing a nasal-hinged flap on the host cornea with a microkeratome. The second step consisted of extracting a stromal piano-powered disk from the donor's cornea using an artificial chamber. The 80-microm thick lamellar graft was punched with a 7.5-mm circular trephine and positioned beneath the flap. Corneal refractive surgery was scheduled for the end of the sixth postoperative month.

RESULTS

No corneal refractive surgery was performed after 6 months of follow-up. Only one eye gained five lines of best spectacle-corrected visual acuity (BSCVA). Among the other three eyes, two had unchanged BSCVA and one lost one line of BSCVA. At the end of surgery, mean corneal thickness was increased by 148.75 microm.

CONCLUSIONS

Microkeratome-assisted additive stromal keratoplasty appears to be a safe and straightforward surgical technique that preserves the host endothelium and avoids the need of an open-sky procedure. However, in our study, MASK is not considered as an alternative to penetrating or deep lamellar keratoplasty in the management of keratoconus with clear cornea because of imprecise anatomic and refractive outcomes.