Transepithelial phototherapeutic keratectomy for treatment-resistant recurrent corneal erosion syndrome
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-04-15 |
| Journal | Graefe s Archive for Clinical and Experimental Ophthalmology |
| Authors | Mukhtar Bizrah, Maheshver Shunmugam, Geoffrey Ching, Radhika Pooja Patel, Nizar Din |
| Institutions | Imperial College Healthcare NHS Trust, University of British Columbia |
| Citations | 3 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for High-Precision Ophthalmic Laser Systems
Section titled âTechnical Documentation & Analysis: MPCVD Diamond for High-Precision Ophthalmic Laser SystemsâReference Paper: Bizrah et al. (2024). Transepithelial phototherapeutic keratectomy for treatment-resistant recurrent corneal erosion syndrome. Graefeâs Archive for Clinical and Experimental Ophthalmology.
Executive Summary
Section titled âExecutive SummaryâThis study validates the long-term safety and efficacy of Transepithelial Phototherapeutic Keratectomy (TE-PTK) using Excimer laser ablation for treating refractory Recurrent Corneal Erosion Syndrome (RCES). The findings underscore the critical need for high-precision, high-repetition-rate laser systems, which rely heavily on advanced thermal management and robust optical components.
- Application Focus: TE-PTK utilizes Excimer laser ablation (total depth 65 ”m) for highly precise corneal surface modification in treatment-resistant RCES.
- System Demand: The procedure requires ultra-low latency (2.9 ms total system latency) and high-frequency tracking (1050 Hz), necessitating superior thermal stability in the laser optics.
- Performance Metrics: The study achieved a high success rate (96% symptom improvement/resolution) and a low complication rate (1.6% Grade 2 cornea haze), demonstrating the reliability of the underlying laser technology.
- Thermal Challenge: The use of Mitomycin C (MMC) post-ablation highlights the industryâs concern regarding post-operative haze, which can be mitigated by ensuring optimal beam quality and stability via high-purity optics.
- 6CCVD Value Proposition: 6CCVDâs Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) materials are essential for manufacturing the next generation of stable, high-power UV laser optics (windows, heat spreaders) required for high-repetition-rate ophthalmic systems.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters extracted from the study highlight the demanding operational environment of the Excimer laser system used for TE-PTK:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Total Ablation Depth | 65 | ”m | Epithelial (50 ”m) + Subepithelial (15 ”m) |
| Treatment Zone Diameter | 9 | mm | Total ablation and transition zone |
| Excimer Laser Mode | Transepithelial | N/A | Surgical delivery method |
| Eye Tracker Frequency | 1050 | Hz | High-speed infrared tracking |
| System Total Latency | 2.9 | ms | Critical for precise ablation alignment |
| Refractive Correction Factor | +0.50 | D | Applied for 65 ”m ablation to minimize hyperopic shift |
| Post-Ablation Haze Rate | 1.6 | % | Grade 2 cornea haze incidence |
| Post-Ablation Treatment | MMC 0.02% | N/A | Applied for 30 s to minimize haze development |
| Mean Post-Op Follow-up | 60.5 | months | Demonstrates long-term stability requirements |
Key Methodologies
Section titled âKey MethodologiesâThe TE-PTK procedure relies on highly controlled laser parameters and precise surgical steps:
- Pre-operative Assessment: Corrected Distance Visual Acuity (CDVA), topography, and tomography (SCHWIND Sirius) were performed over a 12 mm diameter.
- Laser Setup: SCHWIND Custom Ablation Manager set in transepithelial PTK mode.
- Alignment: Achieved using a 1050 Hz infrared eye tracker integrated into the laser system, centered on the corneal vertex.
- Ablation Protocol: Total ablation depth of 65 ”m (50 ”m epithelium + 15 ”m subepithelium).
- Refractive Compensation: A correction factor of +0.50 D was applied for 65 ”m ablation depth to ensure a neutral refractive outcome (not used for myopic eyes).
- Post-Ablation Treatment: Mitomycin C (MMC) 0.02% was applied for 30 seconds, followed by a thorough ocular surface wash.
- Post-Operative Care: Therapeutic bandage contact lens applied, followed by a regimen of Ciprofloxacin, Diclofenac, and Fluorometholone eye drops.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful implementation of high-frequency, high-precision Excimer laser systems (like those used in TE-PTK) is fundamentally dependent on advanced materials capable of managing high thermal loads and maintaining optical integrity in the deep UV spectrum. 6CCVD specializes in the MPCVD diamond required for these demanding applications.
Applicable Materials for Excimer Laser Optics & Thermal Management
Section titled âApplicable Materials for Excimer Laser Optics & Thermal ManagementâThe high pulse repetition rate (implied by the 1050 Hz tracking system) and the short UV wavelength of Excimer lasers necessitate materials with the highest thermal conductivity and lowest UV absorption.
| Component Requirement | 6CCVD Material Recommendation | Key Capability Match |
|---|---|---|
| Excimer Output Window/Lens | Optical Grade Single Crystal Diamond (SCD) | Ultra-low absorption in UV, high damage threshold, superior thermal stability (k > 2000 W/mK). Essential for maintaining beam quality at high pulse rates. |
| High-Power Heat Spreaders | High-Purity Polycrystalline Diamond (PCD) or SCD Substrates | Excellent thermal management for laser diodes, power supplies, and high-frequency components (e.g., 1050 Hz eye tracker electronics). |
| Ablation Mask/Aperture | Custom Laser-Cut SCD/PCD | High hardness and erosion resistance ensure long-term dimensional stability and precision for defining the 9 mm treatment zone. |
Customization Potential for Ophthalmic Systems
Section titled âCustomization Potential for Ophthalmic Systemsâ6CCVDâs manufacturing capabilities directly address the needs of advanced ophthalmic laser system designers:
- Custom Dimensions: We provide diamond plates and wafers up to 125 mm (PCD) and custom SCD sizes, allowing for large-format optical windows or substrates required in complex beam delivery paths.
- Precision Thickness Control: SCD and PCD layers are grown from 0.1 ”m up to 500 ”m, ensuring optimal thickness for specific optical path lengths and thermal requirements. Substrates up to 10 mm thick are available for robust heat sinking.
- Ultra-Low Roughness Polishing: Maintaining beam quality is paramount. 6CCVD guarantees surface roughness (Ra) of < 1 nm for SCD and < 5 nm for inch-size PCD, minimizing scatter and absorption losses in the UV spectrum.
- Integrated Metalization: For effective heat sinking and mounting within the laser head, 6CCVD offers internal metalization services (Au, Pt, Pd, Ti, W, Cu) tailored to specific thermal and electrical interfaces.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in the application of diamond materials in high-power laser and thermal management environments. We can assist engineers and scientists working on similar Phototherapeutic Keratectomy (PTK) or Refractive Surgery projects by providing:
- Material selection consultation to optimize UV transparency and thermal conductivity for specific Excimer wavelengths.
- Design guidance for integrating diamond heat spreaders into high-frequency tracking and control electronics (e.g., the 1050 Hz eye tracker).
- Custom fabrication and metalization solutions for prototype development and high-volume manufacturing.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Background To evaluate the efficacy and safety of trans-epithelial phototherapeutic keratectomy (TE-PTK) as a treatment for recurrent corneal erosion syndrome (RCES) in patients with symptoms refractory to conventional treatments. Methods All patients who received TE-PTK treatment for RCES had failed 3 or more conventional treatments and were reviewed, and if met criteria, approved by healthcare workers of the British Columbia public health authority (Medical Services Plan (MSP). A retrospective chart review and telephone survey were conducted at the Pacific Laser Eye Centre (PLEC). Exclusion criteria were ocular co-morbidities potentially affecting treatment efficacy. Results This study included 593 eyes of 555 patients (46.2% male; 50.9 ± 14.2 years old) who underwent TE-PTK. The leading identified causes of RCES were trauma (45.7%) and anterior basement membrane dystrophy (44.2%). The most common pre-PTK interventions were ocular lubricants (90.9%), hypertonic solutions (77.9%), and bandage contact lenses (50.9%). Thirty-six eyes had undergone surgical interventions such as stromal puncture, epithelial debridement, or diamond burr polishing. Post-PTK, 78% of patients did not require any subsequent therapies and 20% required ongoing drops. Six patients (1.1%) reported no symptom improvement and required repeat TE-PTK for ongoing RCES symptoms after initial TE-PTK. All 6 eyes were successfully retreated with TE-PTK (average time to retreatment was 11.3 ± 14.9 months). There was no significant difference in best corrected visual acuity pre- vs. post-operatively. The mean post-operative follow-up was 60.5 months (range: 5-127 months). Conclusion TE-PTK has a good efficacy and safety profile for treatment-resistant RCES. The third-party public health-reviewed nature of this study, the low recurrence rate of RCES, and the low PTK retreatment rate suggest that TE-PTK might be considered for wider use in the management of RCES.