UNASSIGNED: Studies in the epidemiology of keratoconus are limited in Southeast Asia. A study on the prevalence and characteristics of keratoconus in the Thai population could give a general idea of its impact.
UNASSIGNED: To study keratoconus prevalence in patients seeking refractive surgery and analyze the characteristics of keratoconus.
UNASSIGNED: Medical records from April 2015 to August 2018 were retrospectively reviewed. Keratoconus and keratoconus suspect prevalence in patients seeking laser vision correction were calculated. The characteristics of keratoconus patients were reviewed. The Amsler-Krumeich classification was used to determine the stages. Topographically, the types of cones were categorized into oval, nipple, pellucid marginal degeneration (PMD)-like, and astigmatic types.
UNASSIGNED: Keratoconus and keratoconus suspect prevalence were 1.66% and 0.68%, respectively. Out of the affected patients, 73.8% were male. The mean age at diagnosis was 25.25 ± 8.35 years. The presenting symptoms were blurred vision (87%) and itching (47%). Stage 1 was predominant, found in 39% of patients (followed by stages 2, 4, and 3, respectively). Ocular findings comprised the Munson sign (14.63%), the Rizutti sign (6.94%), Fleischer ring (28.14%), Vogt striae (24.95%), corneal scar (8.63%), prominent corneal nerve (2.81%), and corneal staining (7.69%). Mean uncorrected visual acuity (logarithm of the minimum angle of resolution [logMAR]) was 0.88 ± 0.64. Mean corrected visual acuity (logMAR) was 0.40 ± 0.49. Mean Q-value was -0.92 ± 0.63. The thinnest pachymetry was 459.39 ± 56.96 microns. The mean keratometry was 49.7 ± 6.64 diopters. Topographically, the types of cones were oval (57%), astigmatic (33%), PMD-like (5%), and nipple type (4%).
UNASSIGNED: Keratoconus prevalence among Thai patients seeking refractive surgery was 1.66%. Most patients were male and presented with the disease at a mild bilateral stage in their second decade of life.

OBJECTIVE: To evaluate refractive, aberrometric, topographic, and topometric outcomes of asymmetric intracorneal ring segment (ICRS) implantation in snowman phenotype (asymmetric bow-tie) keratoconus.
METHODS: This retrospective, interventional study included eyes with snowman phenotype keratoconus. Two asymmetric ICRSs (Keraring AS) were implanted after femtosecond laser-assisted tunnel formation. Visual, refractive, aberrometric, topographic, and topometric changes after asymmetric ICRS implantation were evaluated with a mean follow-up of 11 months (6-24 months).
RESULTS: Seventy-one eyes were analyzed in the study. Keraring AS implantation corrected refractive errors significantly. The mean spherical error decreased from -5.06±4.23 D to -1.62±3.45 D (P=0.001), and the mean cylindrical error decreased from -5.43±2.48 D to -2.44±1.49 D (P=0.001). Uncorrected distance visual acuity improved from 0.98±0.80 to 0.46±0.46 Log MAR (P=0.001), and corrected distance visual acuity improved from 0.58±0.56 to 0.17±0.39 Log MAR (P=0.001). Keratometry (K) maximum, K1, K2, K mean, astigmatism, and corneal asphericity (Q-value) showed a significant decrease (P=0.001). Vertical coma aberration decreased significantly from -3.31±2.12μm to -2.56±1.94μm (P=0.001). All topometric indices of corneal irregularities were significantly reduced postoperatively (P=0.001).
CONCLUSIONS: Keraring AS implantation in snowman phenotype keratoconus demonstrated good efficacy and safety. Clinical, topographic, topometric, and aberrometric parameters improved significantly after Keraring AS implantation.

OBJECTIVE: To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD).
METHODS: It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1 week, 2 and 6 months.
RESULTS: One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5 mm zones increased at 1 week (both P < 0.001) and then started to decrease up to 6 months. However, the corneal irregularity of PMD group had significant reduction only at 1 week in 5-mm zone (P = 0.02) and 2 months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively.
CONCLUSIONS: Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

UNASSIGNED: To report a case of late-onset corneal haze 3 months after intrastromal corneal ring segment (ICRS) implantation in an eye with previous transepithelial topography-guided photorefractive keratectomy (TG-PRK).
UNASSIGNED: A 40-year-old woman with stable keratoconus for 10 years underwent limited TG-PRK with mitomycin C in both eyes for mixed astigmatism. After four years, with atopic symptoms worsening and eye rubbing, the patient presented keratoconus progression in the left eye with increased irregular astigmatism. An ICRS was implanted with initial improvement in vision. Three months later severe subepithelial haze was observed along the ring groove.
UNASSIGNED: This is the first report of subepithelial haze after ICRS implantation. This report increases the evidence that permanent corneal wound healing changes occur after PRK and that late-onset haze may be triggered by corneal remodeling, as little inflammation or epithelial defect occurs after ICRS implantation. We do believe the detection of triggers, identification of risk factors of late-onset haze and appropriate preoperative counselling have an increasing importance due to the rising number of patients that have undergone PRK.

Intracorneal ring segment (ICRS) implantation represents a modern, minimally invasive, surgical option for visual improvement in patients with keratoconus. ICRS modify the corneal geometry in a manner that enhances its refractive properties and thereby, they improve visual acuity. It is well-documented that implantation of ICRS decreases the keratometric readings, spherical equivalent and cylinder, reduces high-order aberrations and improves uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (BCDVA) in patients with keratoconus. Success rate after ICRS implantation is high, depending on appropriate patient selection and adherence to suitable implantation nomograms, and most important, the overall complication rate is very low. This review is summarizing current indications/contra-indications for ICRS implantation, implantation techniques, clinical outcomes and potential complications, shedding light on myths and realities related to this innovative surgical option.

To evaluate the efficacy of the functional, keratometric, and refractive postoperative parameters of intracorneal ring segment (ICRS) implantation in keratoconus and its association with collagen cross-linking (CXL), photorefractive keratectomy (PRK), and intraocular lenses (IOLs).
We conducted a systematic review and meta-analysis on case series published between 2007 and 2017.
We included 95 case series with a total of 4560 patients. We included 64 studies of the ICRS procedure, 20 studies of ICRS+CXL, 9 studies of ICRS+CXL+PRK, and 5 studies of ICRS+IOL. We demonstrated an overall improvement of all parameters in all procedures. Cylinder was decreased with an overall effect size (ES) of -1.15 (-1.36 to -0.95; I2 = 93.7%). Corrected distance visual acuity was improved with an overall ES of 0.89 (0.78 to 1.00; I2 = 81.9%). Maximal keratometry was decreased with an overall ES of 0.98 (0.85 to 1.11; I2 = 78.9%). ICRS+IOL is the best procedure to improve spherical equivalent and uncorrected distance visual acuity (P < 0.05) compared with other procedures. ICRSs versus ICRS+CXL are similar in all parameters except for corrected distance visual acuity. ICRS+CXL+PRK is better than ICRS alone in all parameters except for the correction of spherical equivalent.
Although the quality and strength of the data are questionable, ICRS implantation is an effective strategy to preserve visual function in keratoconic patients. Particularly, ICRS+CXL+PRK could be a low invasive procedure to propose to young keratoconic patients.
To propose an overview of postoperative parameters on each ICRS procedure on keratoconus.

The aim of this study is to identify predisposing factors, the clinical course and visual outcomes in patients with keratitis after intracorneal ring implantation.
In a retrospective study, 11 patients with documented keratitis after intracorneal ring implantation and 71 matched controls with uncomplicated surgery were enrolled. Patients were examined for slitlamp findings and corrected distance visual acuity at time of the initial presentation, one month later and six months later. Smears and cultures were provided in all cases. Relevant data in controls were extracted from their medical records, and statistical analysis was done.
Keratitis onset time ranged from three to 56 days. The incidence was 2.7 per cent over two years. All pathogens were Gram-positive cocci, and the most frequent was Staphylococcus spp. No relationship was found between keratitis occurrence and the ring type or the femtosecond procedure, but the rate of keratitis was higher in patients with the horizontal position of intracorneal ring segments (p = 0.001; Fisher\'s exact test). All cases were treated with implant explantation and tunnel irrigation with antibiotics. In three cases, amniotic membrane transplantation was performed, and two cases finally underwent penetrating keratoplasty. The final six month corrected distance visual acuity was 0.68 ± 0.35. Poor corrected distance visual acuity improvement was associated with the ulcer size at the first day of the diagnosis (p = 0.011; Spearman\'s rho).
The only predisposing factor was the horizontal position of the ring. A careful evaluation in the early post-operative period for any sign of the infiltration would be helpful. Early diagnosis with proper management including fortified antibiotic therapy specifically against Gram-positive cocci and removal of the intracorneal ring seems to result in acceptable visual outcomes in later follow-up. However, a corneal transplant may be the only choice in advanced infectious complications.

OBJECTIVE: To represent mathematically the intersection between the ectatic corneal geometry and the plane of intracorneal ring implants (ICRS) in order to determine the corneal response to ICRS surgery in keratoconus (KC). Thereafter, to present the concept and early results of a newly derived topography-guided nomogram for ICRS surgery for the treatment of keratectasia.
METHODS: The corneal rings plane intersection was modelled to a conic section. Ring effect was the result of: the ring size, position (steep vs flat), location (distance from the geometric centre of the cornea), and the discrepancy between the ring\'s curvature and the tunnel\'s curvature. Femtosecond laser was used to create the tunnels and the incision sites were chosen according to the nomogram in order to place the thickest ring in the steepest portion of the cornea regardless of the astigmatism axis of refraction.
RESULTS: The conic section had a more prolate shape in the steep area of the cornea than in the flat area, depending on the corneal sagittal curvature. Equal ring size had more flattening effect in the steep area than in the flat area. Thick segment should be implanted under the steep portion of the cornea regardless of the cylinder axis of refraction. Single segment in the steep area was sufficient in early and moderate cases of KC. The new nomogram provided more topographic regularity with significant reduction of astigmatism and better improvement in uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) than the conventional nomogram.
CONCLUSIONS: The newly derived nomogram can produce better results than the conventional nomogram. Moreover, based on this concept, a new nomogram can be integrated into the femtosecond laser software to create topography-guided, customized, elliptical tunnels with modified focal asphericity that allows for customized focal flattening of the irregularly steepened ectatic cornea.

Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures.

In order to determine the effect of intracorneal rings (Intacs SK), when implanted in keratoconic patients, on corneal curvature, Uncorrected Visual Acuity (UCVA), Best Corrected Visual Acuity (BCVA) and on the progression of the cone through three years follow-up period. In this prospective nonrandomized study 114 eyes of 71 keratoconic patients (38 females and 33 males) were implanted with Intacs SK. Incisions were always made in the steep meridian. UCVA, BCVA, Corneal Topography (TMS) were measured pre and postoperatively and at intervals of 1, 3, 6 & 12 months then yearly for 3 consecutive years. Preoperative mean k-reading was 52.53 and 48.18, 49.56, 49.17, 48.51, 48.15 & 48.01 at 1, 3, 6, 12, 24 & 36 months postoperatively (P‹0.01). In terms of UCVA, 15.64% of patients gained more than 3 lines and 69.73% gained 1-3 lines with a total of 85.37% of patients gaining lines compared to their preoperative UCVA (P‹0.01) while 14.63% of cases did not gain any lines at 1 month postoperative. At three months postoperatively, 12.64% gained more than 3 lines, 71.15% gained 1-3 lines with a total of 83.79% while 16.21% did not gain any lines. Three years postoperative 11.82% of cases gained more than 3 lines, 73.23% gained 1-3 lines with a total of 85.05% while 14.95% did not gain any lines (P‹0.01). With regard to BCVA, 19.73% gained more than 3 lines, 68.26% gained 1-3 lines with a total of 87.99% of cases gaining lines compared to their preoperative BCVA (P‹0.01) while 12.01% did not gained any lines at 1 month postoperative. At three months postoperatively, 14.96% gained more than 3 lines, 70.19% gained 1-3 lines with a total of 85.15% while 14.85% did not gain any lines. Three years postoperative, 12.17% gained more than 3 lines, 71.78% gained 1-3 lines with a total of 83.95% (P‹0.01) while 16.05% did not gain any lines. No eyes lost any lines as it pertained to UCVA & BCVA. Despite the fluctuation of k-readings, UCVA and BCVA in the first 3 months, which may represent the time needed to stabilize the cone, UCVA and BCVA were improved and maintained throughout the study. Patient selection remains the key point for the success of intacs in keratoconic patients.