Hemi-automated lamellar keratoplasty (HALK)

Classic lattice corneal dystrophy: a brief review and summary of treatment modalities

PURPOSE

To provide a brief summary and comparison of the most recent literature on available and theorized treatment modalities for classic lattice corneal dystrophy (LCD). This paper aims to support practitioners in their management of this disease.

METHODS

A search was carried out on available literature through PubMed and Google Scholar of English language articles up to January 2023 that relate to the treatment of LCD. Due to scarcity of literature regarding specific novel therapies for LCD, results from other corneal pathologies (granular corneal dystrophy, corneal scarring) are sometimes included for contrast, which is clearly denoted.

RESULTS

LCD is a slowly progressive disease that leads to recurrent epithelial corneal erosions, stromal haze, corneal opacification, substantial discomfort, and visual impairment. Due to its autosomal-dominant inheritance pattern, this disease can persist throughout ancestral lines and requires consistent treatment and follow-up. An optimal management plan is necessary to (1) prolong years of life with best achievable visual acuity; (2) treat painful recurrent corneal erosions as they occur; (3) ensure proper follow-up throughout the life of a patient, as well as monitor at-risk offspring; and (4) monitor efficacy of treatment.

CONCLUSIONS

This paper addresses (1) treatment for early disease including corneal epithelial debridement, photo therapeutic keratectomy (PTK), femtosecond laser-assisted lamellar keratectomy (FLK), and others; (2) treatment for late disease including full thickness keratoplasties and anterior lamellar keratoplasties; and (3) potential future treatment considerations including a wide variety of topical/systemic, genetic, and regenerative approaches.

Phototherapeutic keratectomy: Indications, methods and decision making

Phototherapeutic keratectomy (PTK) involves treating anterior corneal lesions by superficial corneal ablation using an excimer laser (193 nm). Some of the commonly treated conditions include recurrent corneal erosions (RCE), corneal dystrophies, spheroidal degeneration, keratoconus, and corneal scars. We discuss various techniques of PTK including large area PTK, focal PTK, and multifocal PTK and alternatives to PTK. Masking agents like hyaluronate, methylcellulose, and dextran are recommended to help achieve a better outcome when ablating irregular corneal surfaces. Antifibrotic agents like mitomycin C reduce the chances of recurrence of the disease, apart from minimizing the postoperative scarring. Some of the complications include induced hyperopia and irregular astigmatism, haze, recurrence, and corneal thinning. However, earlier postoperative recovery, possibility of a repeat procedure, and ability to control the depth of ablation make PTK a promising, minimally invasive alternative to keratoplasty in cases with anterior corneal pathologies.

Long-Term Review of Penetrating Keratoplasty: A 20-Year Review in Asian Eyes

PURPOSE

To review the long-term outcomes of optical, therapeutic and tectonic forms of penetrating keratoplasty over a 20-year period in Asian eyes.

DESIGN

Prospective cohort study involving the Singapore Corneal Transplant Study (SCTS).

METHODS

All penetrating keratoplasties (PK) performed at the Singapore National Eye Centre (SNEC) from January 1991 to December 2010 were analyzed using records from the computerized database of the SCTS. This database includes preoperative, intraoperative, and postoperative patient data and donor cornea data. Only primary grafts were included. Patient demographics, donor cornea source, indications for grafting, complications, graft survival rate, and causes of graft failure were analyzed.

RESULTS

A total of 1,206 primary PKs were performed. The mean age of the patients was 55 years (range: <1-101 years). The overall corneal graft survival rates at 1, 5, 10, 15, and 20 years were 91%, 66.8%, 55.4%, 52%, and 44%, respectively. For optical grafts, pseudophakic bullous keratopathy, postinfectious corneal scarring and thinning and keratoconus were the most common diagnoses. Graft survival for optical grafts was significantly better than therapeutic and tectonic grafts at all time points. Multivariate analysis suggested that a younger donor cornea age and higher donor endothelial cell count are associated with better long-term graft survival for optical grafts. Irreversible allograft rejection and late endothelial failure accounted for more than 60% of graft failures.

CONCLUSIONS

Graft survival decreased over time from 91% at 1 year to 44% at 20 years' follow-up. Allograft rejection and late endothelial failure accounted for more than 60% of graft failures.

Long-term outcomes of hemi-automated lamellar keratoplasty

IMPORTANCE

To describe long-term outcomes of hemi-automated lamellar keratoplasty (HALK).

BACKGROUND

HALK is a hybrid anterior lamellar keratoplasty technique for corneas with anterior to mid-stromal scars and topographical irregularities.

DESIGN

Prospective interventional case series.

PARTICIPANTS

Thirty-five eyes of 35 consecutive patients undergoing HALK at a single tertiary referral centre from 2007 to 2016.

METHODS

Patients were followed up for a mean period of 61.4 ± 29.2 months.

MAIN OUTCOME MEASURE

Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE) and cylinder, endothelial cell density (ECD), central corneal thickness (CCT), graft survival and complications were analysed.

RESULTS

The most common indications for HALK were scars because of contact lens associated infectious keratitis (29%), unknown origin (26%) or corneal dystrophies (14%). Five patients had a previous keratoplasty (n = 4; deep anterior lamellar keratoplasty, n = 1). Two HALKs failed at 22 and 32 months follow-up. No graft rejections occurred. UCVA improved from 0.91 ± 0.31 to 0.58 ± 0.35 and BSCVA from 0.66 ± 0.30 to 0.21 ± 0.20 logMAR (P < 0.001) at the last follow-up. Astigmatism (P = 0.2), SE (P = 0.8) and ECD (P = 0.4) did not change significantly during follow-up. CCT increased from 490 to 560 μm (P = 0.004). Kaplan-Meier estimated survival for all HALK cases was 90.6 (95% confidence interval 82.6-98.5) months with a survival probability of 96% at 12 months and 92% at 3, 5 and 7 years of follow-up.

CONCLUSIONS AND RELEVANCE

HALK provides excellent graft survival in primary cases and in patients with prior keratoplasty as well as significant improvement in visual acuity with low complication rates.

Component corneal surgery: An update

Several decades ago, penetrating keratoplasty was a challenge to corneal surgeons. Constant effort by the corneal surgeon to improve the outcomes as well as utilization of the available resources has led to a revolutionary change in the field of keratoplasty. All these efforts have led to the evolution of techniques that allow a corneal surgeon to disease-specific transplant of individual layers of corneal “so-called component corneal surgery” depending on the layer of cornea affected. This has led to an improvement in corneal graft survival as well as a better utilization of corneal tissues. This article reviews the currently available literature on component corneal surgeries and provides an update on the available techniques.

Vision-related quality of life and visual outcomes after small-incision lenticule extraction and laser in situ keratomileusis

PURPOSE

To compare vision-related quality of life (VRQoL) scores and clinical outcomes between small-incision lenticule extraction and laser in situ keratomileusis (LASIK).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Prospective study.

METHODS

Patients had small-incision lenticule extraction using the Visumax 500 kHz femtosecond laser; or LASIK excimer ablation with the Wavelight Allegretto 400 Hz laser. Primary outcomes were 3-month predictability, efficacy, and safety. Secondary outcomes were intraoperative experience, visual symptoms, and VRQoL (validated Quality of Life Impact of Refractive Correction [QIRC] questionnaire) in 25 a subgroup of patients in each group. Following Rasch analysis, "Functional" and "Emotional," QIRC dimensions were analysed separately.

RESULTS

At 3 months, predictability (82.5% versus 85.3%, ±0.5 diopters attempted correction, P =.453), safety index (1.13 ± 0.19 [SD] versus 1.07 ± 0.16, P = .158), and efficacy index (0.91 ± 0.21 versus 0.97 ± 0.19; P = .002) were found when comparing small-incision lenticule extraction (172 eyes) and LASIK (matched 688 eyes). Intraoperative experience between groups was not statistically different; visual fluctuations (P = .020) and episodes of visual blurring (P = .008) were greater after small-incision lenticule extraction than after LASIK at 1 month but not at 3 months. There was no difference in "functional" (66.7 ± 15.7 versus 55.3 ± 22.2, P = .064) and "emotional" (42.7 ± 23.2 versus 37.9 ± 23.8, P = .394) QIRC dimensions between the 2 groups (25 patients in each group) at 3 months.

CONCLUSION

The study, 3-month predictability, safety, and VRQL scores were not statistically different between small-incision lenticule extraction and LASIK.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Dental stem cells: a future asset of ocular cell therapy

Regenerative medicine using patient's own stem cells (SCs) to repair dysfunctional tissues is an attractive approach to complement surgical and pharmacological treatments for aging and degenerative disorders. Recently, dental SCs have drawn much attention owing to their accessibility, plasticity and applicability for regenerative use not only for dental, but also other body tissues. In ophthalmology, there has been increasing interest to differentiate dental pulp SC and periodontal ligament SC (PDLSC) towards ocular lineage. Both can commit to retinal fate expressing eye field transcription factors and generate rhodopsin-positive photoreceptor-like cells. This proposes a novel therapeutic alternative for retinal degeneration diseases. Moreover, as PDLSC shares similar cranial neural crest origin and proteoglycan secretion with corneal stromal keratoctyes and corneal endothelial cells, this offers the possibility of differentiating PDLSC to these corneal cell types. The advance could lead to a shift in the medical management of corneal opacities and endothelial disorders from highly invasive corneal transplantation using limited donor tissue to cell therapy utilizing autologous cells. This article provides an overview of dental SC research and the perspective of utilizing dental SCs for ocular regenerative medicine.