Implantable collamer lens implantation (ICL) versus small incision lenticule extraction (SMILE) in low to moderate myopia: study protocol for a randomized, non-inferiority trial.

BACKGROUND: Implantable collamer lens implantation (ICL) is a form of 'foldable' posterior chamber phakic intraocular lens refractive surgery that generally does not impair cornea and natural accommodation. The potential advantages of the ICL over keratorefractive laser procedures include less induction of higher-order aberrations (HOAs) and enhanced retinal image magnification. On the other hand, small incision lenticule extraction (SMILE), currently, one of the most popular refractive surgery procedures, also offers excellent visual outcomes, particularly for eyes with low to moderate amounts of myopia. The aim of this study is to evaluate whether ICL/TICL (toric ICL) is comparable to SMILE for low to moderate myopia in terms of refractive outcomes at 3 and 18 months post-operatively. METHODS/DESIGN: This is a prospective randomized study. A total of 300 participants will be randomized into two groups, the ICL/TICL group and SMILE group. Eligible participants with spherical equivalent (SE) less than - 6.0 diopter (D) will be recruited. Following randomization, participants will be followed at 1, 3, 6, 12, and 18 months. The primary outcome is the refractive predictability at every postoperative point after surgery, which is the proportion of the number of eyes achieving a postoperative SE within ± 0.5 D and ± 1.0 D of the intended target. Secondary outcome parameters include visual acuity, refraction, adverse events, and quality of vision measurements. DISCUSSION: This trial will provide information on whether ICL has comparable, if not superior, refractive outcomes compared to the established SMILE for low to moderate myopia, thus providing evidence for translation into clinical practice. TRIAL REGISTRATION: Chinese clinical trial registry (ChiCTR) 2200055372. Registered on 08 January 2022.

Visual outcomes and corneal biomechanics after V4c implantable collamer lens implantation in subclinical keratoconus.

PURPOSE: To quantitatively evaluate the safety, efficacy, stability, predictability, and corneal biomechanical parameters after V4c implantable collamer lens (ICL) implantation in subclinical keratoconus. SETTING: Xi'an AIER Eye Hospital, Xi'an, China. DESIGN: Retrospective case series. METHODS: Patients undergoing V4c ICL/toric ICL implantation were examined. Scheimpflug tomography (Pentacam) was used to measure the Belin-Ambrosio enhanced ectasia total deviation index. Dynamic Scheimpflug biomechanical analysis (CorVis ST) was used to measure the corneal biomechanical parameters and Corvis Biomechanical Index. The Tomographic and Biomechanical Index was measured by combined Pentacam with CorVis ST. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, and adverse effects were also investigated. RESULTS: A total of 60 eyes of 60 patients (mean age ± SD, 27.21 ± 7.24 years) were included. The mean preoperative UDVA and CDVA were 1.08 ± 0.25 and 0.12 ± 0.04 logarithm of the minimum angle of resolution (logMAR) (20/230 and 20/28 Snellen VA), respectively. After 2 years, the mean postoperative UDVA and CDVA were 0.01 ± 0.06 and -0.05 ± 0.03 logMAR (20/20 and 20/18 Snellen VA), respectively. The mean difference between the intended and achieved spherical equivalent (SE) was -0.08 ± 0.47 diopter (D), and the SE was within ±1.00 D of the intended correction in 57 eyes (95%), and 58 eyes (97%) had astigmatism less than 0.50 D. The refractive results were stable 2 years postoperatively, and the corneal biomechanical parameters returned to their preoperative levels at 3 months. CONCLUSIONS: The V4c ICL/toric ICL in subclinical keratoconus offered predictable correction of SE refractive error. Refractive results and corneal biomechanics were stable at the 2-year follow-up.

Corneal Nerve Regeneration after Self-Retained Cryopreserved Amniotic Membrane in Dry Eye Disease.

PURPOSE: To evaluate the efficacy of self-retained cryopreserved amniotic membrane (CAM) in promoting corneal nerve regeneration and improving corneal sensitivity in dry eye disease (DED). METHODS: In this prospective randomized clinical trial, subjects with DED were randomized to receive CAM (study group) or conventional maximum treatment (control). Changes in signs and symptoms, corneal sensitivity, topography, and in vivo confocal microscopy (IVCM) were evaluated at baseline, 1 month, and 3 months. RESULTS: Twenty subjects (age 66.9 ± 8.9) were enrolled and 17 completed all follow-up visits. Signs and symptoms were significantly improved in the study group yet remained constant in the control. IVCM showed a significant increase in corneal nerve density in the study group (12,241 ± 5083 µm/mm2 at baseline, 16,364 ± 3734 µm/mm2 at 1 month, and 18,827 ± 5453 µm/mm2 at 3 months, p = 0.015) but was unchanged in the control. This improvement was accompanied with a significant increase in corneal sensitivity (3.25 ± 0.6 cm at baseline, 5.2 ± 0.5 cm at 1 month, and 5.6 ± 0.4 cm at 3 months, p < 0.001) and corneal topography only in the study group. CONCLUSIONS: Self-retained CAM is a promising therapy for corneal nerve regeneration and accelerated recovery of the ocular surface health in patients with DED. The study is registered at clinicaltrials.gov with trial identifier: NCT02764814.

Corneal melt of incisions overlying corneal ring segments: case series and literature review.

PURPOSE: : To describe 4 cases of corneal melt encountered after insertion of intrastromal corneal ring segments (ICRS) for ectasia, propose a theory as to the etiology of the melt, and review relevant literature. METHODS: : Retrospective observational case series. Eyes with corneal melt after ICRS implantation were identified and the charts were reviewed. Relevant literature was reviewed to establish the overall incidence of corneal melt after ICRS and potential contributing factors. RESULTS: : Each of our 4 cases of corneal melt occurred in an eye with a corneal incision overlying the ICRS. Case 1 occurred in an eye with pellucid marginal degeneration in which the ICRS incision overlaid the segment. Case 2 occurred in an eye after radial keratotomy that underwent ICRS to address refractive instability. Corneal melt developed around a gaping radial keratotomy (RK) incision. Case 3 occurred in an eye after radial keratotomy and subsequent hyperopic laser in situ keratomileusis that developed ectasia for which an ICRS was inserted. Corneal melt developed in association with an RK incision overlying the ICRS in the area of a peripheral corneal ulcer. Case 4 occurred in an eye after radial keratotomy with an unstable cornea that underwent ICRS implantation for improved stability. The ring segment extruded through an overlying RK incision and corneal melt developed. The literature on ICRS implantation for keratoconus and ectasia was reviewed. Of 1835 eyes after ICRS implantation for keratoconus or ectasia, there were 12 reported cases of corneal melt (0.7%), a majority (7% or 58%) were associated with overlying incision. CONCLUSIONS: : Corneal melt is a rare complication of ICRS. We conclude that wound gape over ICRS contributes to the development of melt. Strategies can be employed to reduce the incidence of this rare but important complications of ICRS.

Lasers in refractive surgery: history, present, and future.

The history of laser refractive surgery is reviewed, followed by an overview of the current state of the field as well as a look at promising future developments.

Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: comparative study.

PURPOSE: To compare the efficacy of conventional laser in situ keratomileusis (LASIK) in treating corneal astigmatism and in treating noncorneal ocular residual astigmatism. SETTING: Private practice, Nashville, Tennessee, USA. DESIGN: Retrospective case series. METHODS: The records of dominant eyes of consecutive patients who had LASIK were retrospectively analyzed to compare the efficacy of LASIK in eyes with predominantly anterior corneal astigmatism with the efficacy in eyes with predominantly ocular residual astigmatism (ORA). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Preoperatively, the ratio of ORA to preoperative refractive cylinder (R) was used to divide the patients into 2 groups; that is, eyes with predominantly anterior corneal astigmatism (ORA/R ratio <1.0) and eyes with predominantly ORA (ORA/R ratio ≥1.0). Efficacy was determined by examining the magnitude of the remaining uncorrected astigmatism and comparing the index of success (proportion of preoperative refractive astigmatism that remained uncorrected by LASIK) between the 2 groups. RESULTS: The study evaluated 61 eyes of 61 patients. Conventional LASIK was twice as efficacious in the low-ORA group as in the high-ORA group. The index of success was 0.24 and 0.50, respectively, and the difference between groups was statistically significant (P = .036). CONCLUSION: The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.

Corneal intrastromal gatifloxacin crystal deposits after penetrating keratoplasty.

BACKGROUND: An 85-year-old man developed faint crystallike white precipitates in the mid peripheral stroma of his left cornea 3 weeks after undergoing penetrating keratoplasty. The patient had been initially treated with 1% prednisolone acetate ophthalmic suspension and 0.3% gatifloxacin eyedrops to his left eye from the first day postoperatively. Three weeks later, the precipitates were more numerous, larger, and diffuse in distribution. Gatifloxacin was discontinued and substituted with a neomycin-polymixin B-dexamethasone ophthalmic ointment. METHODS: A detailed history, physical examination, laboratory workup, and tandem scanning confocal microscopy were performed. RESULTS: Tandem scanning corneal confocal microscopy confirmed the presence of crystals in the cornea. CONCLUSIONS: Gatifloxacin, a fourth-generation fluoroquinolone, can cause intrastromal macroscopic crystalline deposits through a compromised corneal epithelium, similar to what has been described for ciprofloxacin, a second-generation fluoroquinolone.

BIGH3 mutation spectrum in corneal dystrophies.

PURPOSE: To investigate the molecular pathology underlying BIGH3-related corneal dystrophies (CDs) and to further delineate genotype-phenotype specificity. METHODS: Sixty-one index patients with CDs were subjected to phenotypic and genotypic characterization. The corneal phenotypes of all patients were assessed by biomicroscopy and documented by slit lamp photography. The BIGH3 gene was amplified exon by exon from constitutional DNA to perform single-strand conformation polymorphism (SSCP) analysis, followed by direct bidirectional sequencing of abnormal conformers. RESULTS: The phenotypes of CDs were classified as lattice CD in 30 patients, Groenouw type I in 12 (CDGGI), Avellino in 7 (CDA), Reis-Bückler in 8 (CDRB), and Thiel-Behnke in 4 (CDTB). Fifty occurrences of 16 distinct mutations were identified, including 8 novel mutations responsible for lattice type IIIA in three patients (CDLIIA), intermediate type I/IIIA (CDLI/IIIA) in four patients, and atypical CDL with deep deposits in one patient (CDL-deep). CONCLUSIONS: Disease-causing mutations were identified in 80% of the patients (50/61). All mutations localize in two regions of kerato-epithelin: the amino acid R124 and BIGH3 fasc domain 4. This study also confirms the mutation hot spot at positions R124 and R555 with nearly 50% of the mutations targeting these two amino acids (24/50). In addition the corneal phenotypes induced by changes at R124 and R555 are amino acid specific: R124C in CDLI, R555W and R124S in CDGGI, R124H in CDA, R124L in CRRB, and R555Q in CDTB. In CDLIIIA, CDLI/IIIA, and CDL-deep the genotype-phenotype correlation is domain specific, with all changes occurring at the boundary or within the fasc4 domain.