One-year visual and astigmatic outcomes of keratoconus patients following sequential crosslinking and topography-guided surface ablation: the TOPOLINK study

Refractive surgical approaches to keratoconus: A systematic review and network meta-analysis

Advancements in diagnostic methods and surgical techniques for keratoconus (KC) have increased non-invasive treatment options. Successful surgical planning for KC involves a combination of clinical science, empirical evidence, and surgical expertise. Assessment of disease progression is crucial, and halting the progression should be the focus if it is progressive. While surgeons used to rely on experience alone to decide the surgical method, comparing the network of primary factors, such as visual acuity, across studies can help them choose the most appropriate treatments for each patient and achieve optimal outcomes. Meticulous tabulation methods facilitate interpretation, highlighting the importance of selecting the correct surgical and rehabilitation approach based on each patient's condition and stage of the disease. We detail the outcomes of a comprehensive network meta-analysis comparing the effectiveness of various combined therapeutic refractive treatments for KC at identical stages of the disease, spanning four distinct follow-up intervals. Additionally, the comprehensive analysis suggests that for corneas with optimal best corrected visual acuity (BCVA) preoperatively (classified as regular), combining phakic intraocular lenses with intracorneal ring segments (ICRS) and corneal cross-linking (CXL) could offer the best therapeutic approach provided the disease stage does not exceed stage 3. For irregular corneas, although initial follow-ups show a significant difference in BCVA with surface ablation, longer-term follow-ups recommend combining surface ablation with ICRS and CXL, especially at higher stages.

Advances in the Treatment of Keratoconus: Epithelial-On (EPI-On) Corneal-Collagen Cross-Linking (CXL) and CXL-Plus Procedures

Keratoconus (KC) incidence is on the increase. The advent of corneal-collagen cross-linking (CXL) has revolutionized the management of KC. This systematic review looks at the efficacy and complications of two novel treatments within CXL: Epithelial-On (Epi-On) and CXL-plus procedures. Two separate literature searches were carried out up until July 1, 2021. Articles only published in the last two years were included to ensure that only the most recent articles were reviewed. A total of 15 articles were selected for this review. There were varied results regarding the efficacy of Epi-On. No significant difference was found between Epi-On and standard Epithelial-Off (Epi-Off) CXL. However, it was found that Epi-On was inferior to standard CXL in terms of reducing KMAX. There was a higher risk of progression in patients treated with Epi-On CXL, with an increased rate of patients requiring re-treatment due to the advancement of their KC. While some studies report CXL-plus procedures demonstrate long-term efficacy and safety, a considerable number of studies advise caution, reporting a significant deterioration in corrected distance visual acuity (CDVA). Consequently, a question persists regarding the safest and most efficacious approach, given the lack of robust large randomized controlled trials (RCTs) in the current literature.

Preferred practice patterns for keratoconus: An e-survey among Indian cornea specialists

PURPOSE

This study aimed to report practice patterns in the management of keratoconus in India.

METHODS

An e-survey was conducted among members of the Cornea Society of India to assess preferred practice patterns for keratoconus.

RESULTS

Of the 912 members, 234 (25.7%) completed the survey. About 88.4% worked in private eye care facilities and 76.1% in cities. Of all the respondents, 91.5% had access to a Scheimpflug-based device or an Orbscan II®; 71.4% of the respondents dispensed scleral contact lenses, and 66.7% dispensed Rose K contact lenses; 92.7% of the respondents performed corneal cross-linking (CXL); and 73.1% of the respondents performed deep anterior lamellar keratoplasty (DALK). A Scheimpflug device or Orbscan II®, Rose K or scleral contact lenses, and CXL were more readily available (P < 0.05) in private eye care facilities. The diagnostic criteria for keratoconus followed by the majority of the respondents (52.1%) were increase in corneal curvature, elevation, and thickness. An increase in keratometry values greater than 0.5 or 1.0D in a 6-month to 1-year period was considered the most favored criterion for keratoconus progression. Epithelium-off, 0.1% riboflavin solution in dextran, and accelerated protocol were the more commonly reported techniques in CXL. About 77.2% of the respondents routinely performed CXL in corneas <400 microns thick. Spectacles (91.0% of the respondents) and topography-guided photorefractive keratectomy (37.6% of the respondents) were, respectively, the preferred optical and surgical methods used to improve vision.

CONCLUSION

While keratoconus management in India is comparable to other developed healthcare systems, the concentration of trained corneal surgeons in cities and private eyecare facilities may lead to less equitable distribution of treatment across the country.

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Comparison of outcomes between cross-linking plus topoguided excimer laser ablation and intrastromal corneal ring segments for keratoconus

OBJECTIVE

To compare cross-linking (CXL) plus topography-guided photorefractive keratectomy (t-PRK) and intrastromal corneal ring segments (ICRS) in keratoconus patients, at 12 months of follow-up.

METHODS

This was a longitudinal, retrospective multi-center study. We included a referred sample of 154 eyes from 149 patients with grade I-III Amsler-Krümeich keratoconus with insufficient corrected-distance visual acuity (CDVA). In group 1 (CXL plus t-PRK, 87 eyes), another possible indication for surgery was evidence of progression. Group 2 (ICRS, 67 eyes) included only eyes with paracentral keratoconus (thinnest point at the inferotemporal quadrant) with coincident axes, and evidence of stabilization was required. A subgroup analysis was performed regarding the disease topographic phenotype. At 12 months postoperatively, visual, refractive, and topographic outcomes were evaluated.

RESULTS

Comparison of the outcomes between CXL plus t-PRK (group 1) and ICRS (group 2) showed similar improvements in CDVA (in group 1, CDVA improved 0.18 logMAR, and in group 2 0.12 logMAR, P = .18) and K2 (-2,45 [6.46] D in group 1 and -2.13 [1.67] D in group 2, P = .34) The improvement in cylinder power was greater in group 2 (-2.37 [2.07] D in group 2 versus -1.18 [2.63] D in group 1, P = .003); group 1 had a higher decrease in Kmax (- 3.26 [3.64] versus-1.74 [2.67], P = .001).

CONCLUSIONS

Both CXL plus t-PRK and ICRS were equally effective in improving CDVA and topographic parameters in a similar group of keratoconus patients at 12 months.

Less Complex Contact Lens Required for a Patient With Keratoconus After Topography-Guided Photorefractive Keratectomy

ABSTRACT

In this report, we discuss contact lens (CL) fitting in a patient with a history of keratoconus (KC), before and after undergoing topography-guided photorefractive keratectomy (TG PRK). Before TG PRK, the patient failed multiple CL modalities and reported difficulty with his habitual CLs and inadequate spectacle-corrected visual acuity to perform his activities of daily living. In this case, a collaborative, comprehensive approach to visual management in a patient with KC was used, and after TG PRK was performed to improve his corneal contour and symmetry, our patient was fit with a standard soft CL and additionally had improved spectacle-corrected visual acuity.

Expanding indications for corneal cross-linking

PURPOSE OF REVIEW

The aim of this study was to summarize the recent developments in corneal cross-linking (CXL) and its indications, including corneal ectasias, refractive surgery and infectious keratitis.

RECENT FINDINGS

Advances in CXL technology, such as the use of higher-intensity LED ultraviolet (UV) light sources and a better understanding of the UV-riboflavin photochemical reaction, have enabled safer and more effective methods of cross-linking thin and ultra-thin corneas, and more effective accelerated transepithelial/'epi-on' CXL procedures that are beginning to supplant the Dresden protocol as the 'gold standard' CXL method. CXL is also being used in combination with laser surgery, not only to expand the patient base who can receive refractive surgery, but also to help rehabilitate vision in patients with ectasia. CXL, and CXL combined with photorefractive keratectomy (PRK), can result in corneal flattening of 1-2 D, and corneal regularization of 4-5 D, respectively. Finally, photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) has been shown to be an effective therapy for infectious keratitis, both alone, and in combination with antimicrobial drugs.

SUMMARY

CXL has evolved from a single technique to treat a single corneal ectasia, keratoconus, to several techniques with several indications, spanning a spectrum of corneal ectasias, as well as visual rehabilitation, refractive procedures and infectious keratitis treatment.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Introducing a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in Keratoconic Corneas

PURPOSE

The aim of this study was to introduce a revised tissue-saving technique for combined topography-guided photorefractive keratectomy (PRK) and cross-linking for keratoconus (KC) treatment and to evaluate its efficacy, safety, and stability.

METHODS

This retrospective, noncontrolled study was performed at Maadi Eye Subspecialty Center and Eye Care Center, Cairo, Egypt. The technique was performed on virgin keratoconic corneas with 3 different morphological patterns of ectasia. It involves performing topography-guided PRK before epithelial removal, followed by customized phototherapeutic keratectomy (PTK) that is tailored to each cornea after studying the treatment profile on the laser treatment screen. The electronic medical records were explored for preoperative and postoperative data, including subjective refraction and topographic data (using Sirius topographer).

RESULTS

The study was conducted on 123 eyes of 93 patients with a mean age of 27.98 years ±6.06. The follow-up ranged from 6 to 36 months (mean ± SD of 16.2 months ±10.4). The results showed statistically nonsignificant differences among the 3 ectasia subgroups in treatment spherical equivalent, treatment maximum depth, thickness of removed epithelium, and thinnest residual stromal bed. There were statistically significant differences in almost all values between the preoperative and postoperative data, with significant postoperative patients' improvement ( P value <0.001). The subgroups' results were almost the same as the whole cohort's results. The safety and efficacy indices of the performed procedure showed remarkably high values (1.48 ± 0.21 and 0.87 ± 0.40, respectively).

CONCLUSIONS

This revised protocol for KC management maximally preserves stromal tissue with proven efficacy, safety, and stability.

Innovations in Corneal Crosslinking

PURPOSE

Corneal Crosslinking (CXL) strengthens the keratoconus cornea and prevents further disease progression. Modified crosslinking protocols and different riboflavin solutions have been proposed to optimize the procedure and improve treatment success.

METHODS

PubMed research of relevant publications and report of own experiences with different CXL protocols.

RESULTS

Accelerated CXL shows comparable efficiency with shorter surgery time and similar complication rates. Customized CXL provides improved results with faster epithelial healing. CXL in a hyperoxic environment seems to be a safe and effective transepithelial alternative with presumably less complications and fewer side effects. Thin corneas (<400 µm) can be treated safely by corneal swelling using hypoosmolar riboflavin solutions and reducing the applied UV-energy. The combination of CXL with photorefractive keratectomy (PRK) can be considered in patients with contact lens intolerance improving visual acuity, however, with increased risk of visual loss compared to CXL alone. Two-Photon (2Ph) CXL is a promising new technology enabling three-dimensional CXL.

DISCUSSION

Recently developed CXL protocols offer advantages over the standard "Dresden-protocol" and should be considered in patients with progressive keratectasia.

[Treatment indications for corneal crosslinking and clinical results of new corneal crosslinking techniques]

BACKGROUND

Corneal crosslinking (CXL) is used in keratoconus to strengthen and stabilize the cornea and to prevent further progression with subsequent visual loss and the possible need for keratoplasty. Correct treatment indications is crucial in this context. Since the introduction of the initial Dresden protocol, other modified CXL protocols have been proposed to optimize treatment success.

OBJECTIVE

The relevant parameters for treatment indications are explained and the clinical results of new CXL protocols are presented.

METHODS

The currently valid criteria with respect to the indications for CXL in keratoconus, PubMed search for relevant publications and own experiences with different CXL protocols are presented.

RESULTS

The reproducibility of topographic parameters depends on the stage of the keratoconus. Accelerated CXL as well as transepithelial CXL with a hyperoxic environment show comparable efficiency with shorter surgery time and possibly lower complication rates. Customized CXL with an individualized UV irradiation profile provides improved results with faster epithelial healing. Lower UV energy doses enable CXL to be conducted in eyes with minimal stromal pachymetry of less than 400 µm before irradiation. The combination of CXL with photorefractive keratectomy (PRK) provides visual acuity improvements but also increases the risk of visual loss.

CONCLUSION

Current indication rules for CXL neglect the reduced reproducability of topographic and tomographic measurements in keratoconus. The latest CXL protocols presented here provide a safe alternative with similar and/or better efficacy compared to standard CXL. The combination of CXL with PRK offers an option for visual rehabilitation in patients with contact lens intolerance.

Corneal Cross-Linking for Keratoconus: Current Knowledge and Practice and Future Trends

Corneal collagen cross-linking (CXL) with riboflavin is an accepted universal standard of care for our keratoconus patients with progressive disease. It has been a game changer in how we manage keratoconus. Early diagnosis and treatment is essential in paediatric patients as younger patients progress more rapidly and have poorer transplant outcomes. There is an ongoing debate around standard, accelerated, and transepithelial protocols of CXL, the role of CXL, and the combination of laser refractive surgery. Future developments will improve CXL safety and efficacy and the scope of utilization, but we must be careful not to leap too far ahead with clinical applications before publication of basic science research and good clinical results with standardized protocols.