Intrastromal corneal inlays are an emerging treatment for presbyopic patients. The KAMRA™ small aperture inlay was the first such inlay to receive Conformité Européenne (CE) marking in 2005. It has been shown to improve uncorrected near and intermediate visual acuity without adversely affecting uncorrected distance visual acuity. Due to the age of presbyopic patients, they may eventually develop cataracts. In two such cases, we found that cataract surgery with the KAMRA implant left in place was not technically more difficult, and that the surgical procedure could be improved by additional ocular rotations to improve visualization. Biometry readings were reliable, and it appeared that the SRK/T formula was accurate for calculation of intraocular lens power. Cataract surgery with the KAMRA implant left in situ is a viable option for patients.
cataract surgery; KAMRA; corneal inlay; AcuTarget; presbyopia
To compare the 3-year incidence of de novo ocular hypertension (OHT) after Descemet stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty (PK). For DSAEK, to evaluate predictors for OHT and 2-year outcomes after OHT development.
This was a review of the prospective Singapore Corneal Transplant Study at a single tertiary referral center. Consecutive DSAEKs and PKs for Fuchs’ endothelial dystrophy (FED) and pseudophakic bullous keratopathy (PBK) in eyes without pre-existing glaucoma were analyzed. OHT incidence after DSAEK and PK were compared using Kaplan–Meier survival analysis, and OHT risk factors identified using Cox proportional regression. OHT was defined: intraocular pressure (IOP) ≥ 24 mmHg or ≥ 10 mmHg from baseline. Secondary outcomes 2 years after OHT development in DSAEK were rates of glaucoma medical therapy failure, IOP success, graft failure and rejection, and best-spectacle corrected visual acuity (BSCVA).
There were 108 (96.4%) DSAEKs and 216 (96%) PKs. The 1-, 2- and 3-year de novo OHT incidence was not significantly different between DSAEK (36.1%, 47.2%, 47.2%, respectively) and PK (35.7%, 44.9%, 45.8%, respectively; P = 0.914). OHT incidence did not differ in subgroup analyses of multiple clinical variables (P > 0.1). OHT predictors after DSAEK were: fellow eye glaucoma (hazard ratio [HR] 3.20, P = 0.004), age <60 years (HR 2.41, P = 0.016), concurrent goniosynechiolysis (HR 3.29, P = 0.021), post-graft complications or procedures (HR 2.85, P = 0.006). Two years after OHT onset, 29.7% of DSAEKs failed glaucoma medical therapy requiring trabeculectomy. Complete and qualified IOP success was achieved in 23.5% and 76.5%, respectively. Graft failure developed in 9.8% and graft rejection in 5.9%. At 6 months, 1, and 2 years from OHT onset, 86.3%, 88.3%, and 92.1% achieved BSCVA 20/40, respectively.
DSAEK and PK have comparable OHT risks. A significant 30% of DSAEK eyes with OHT require filtration surgery. Effective IOP control and good graft and visual outcomes are achieved with treatment.
DSAEK; glaucoma; ocular hypertension; risk factors
Frequent and long-term use of topical corticosteroids after corneal transplantation is necessary to prevent graft rejection. However, it relies heavily on patient compliance, and sustained therapeutic drug levels are often not achieved with administration of topical eye drops. A biodegradable drug delivery system with a controlled and sustained drug release may circumvent these limitations. In this study, we investigated the efficacy of a prednisolone acetate (PA)-loaded poly (d,l-lactide-co-ε-caprolactone) (PLC) microfilm drug delivery system on promoting the survival of allogeneic grafts after penetrating keratoplasty (PK) using a rat model. The drug release profiles of the microfilms were characterized (group 1). Subsequently, forty-eight PK were performed in four experimental groups: syngeneic control grafts (group 2), allogeneic control grafts (group 3), allogeneic grafts with subconjunctivally-implanted PA microfilm (group 4), and allogeneic grafts with PA eye drops (group 5; n = 12 in each). PA-loaded microfilm achieved a sustained and steady release at a rate of 0.006–0.009 mg/day, with a consistent aqueous drug concentration of 207–209 ng/ml. The mean survival days was >28 days in group 2, 9.9±0.8 days in group 3, 26.8±2.7 days in group 4, and 26.4±3.4 days in group 5 (P = 0.023 and P = 0.027 compared with group 3). Statistically significant decrease in CD4+, CD163+, CD 25+, and CD54+ cell infiltration was observed in group 4 and group 5 compared with group 3 (P<0.001). There was no significant difference in the mean survival and immunohistochemical analysis between group 4 and group 5. These results showed that sustained PA-loaded microfilm effectively prolongs corneal allograft survival. It is as effective as conventional PA eye drops, providing a promising clinically applicable alternative for patients undergoing corneal transplantation.
Considerable interest has been generated for the development of suitable corneal endothelial graft alternatives through cell-tissue engineering, which can potentially alleviate the shortage of corneal transplant material. The advent of less invasive suture-less key-hole surgery options such as Descemet’s Stripping Endothelial Keratoplasty (DSEK) and Descemet’s Membrane Endothelial Keratoplasty (DMEK), which involve transplantation of solely the endothelial layer instead of full thickness cornea, provide further impetus for the development of alternative endothelial grafts for clinical applications. A major challenge for this endeavor is the lack of specific markers for this cell type. To identify genes that reliably mark corneal endothelial cells (CECs) in vivo and in vitro, we performed RNA-sequencing on freshly isolated human CECs (from both young and old donors), CEC cultures, and corneal stroma. Gene expression of these corneal cell types was also compared to that of other human tissue types. Based on high throughput comparative gene expression analysis, we identified a panel of markers that are: i) highly expressed in CECs from both young donors and old donors; ii) expressed in CECs in vivo and in vitro; and iii) not expressed in corneal stroma keratocytes and the activated corneal stroma fibroblasts. These were SLC4A11, COL8A2 and CYYR1. The use of this panel of genes in combination reliably ascertains the identity of the CEC cell type.
LASIK (laser-assisted in situ keratomileusis) is a common laser refractive procedure for myopia and astigmatism, involving permanent removal of anterior corneal stromal tissue by excimer ablation beneath a hinged flap. Correction of refractive error is achieved by the resulting change in the curvature of the cornea and is limited by central corneal thickness, as a thin residual stromal bed may result in biomechanical instability of the cornea. A recently developed alternative to LASIK called Refractive Lenticule Extraction (ReLEx) utilizes solely a femtosecond laser (FSL) to incise an intrastromal refractive lenticule (RL), which results in reshaping the corneal curvature and correcting the myopia and/or astigmatism. As the RL is extracted intact in the ReLEx, we hypothesized that it could be cryopreserved and re-implanted at a later date to restore corneal stromal volume, in the event of keratectasia, making ReLEx a potentially reversible procedure, unlike LASIK. In this study, we re-implanted cryopreserved RLs in a non-human primate model of ReLEx. Mild intrastromal haze, noted during the first 2 weeks after re-implantation, subsided after 8 weeks. Refractive parameters including corneal thickness, anterior curvature and refractive error indices were restored to near pre-operative values after the re-implantation. Immunohistochemistry revealed no myofibroblast formation or abnormal collagen type I expression after 8 weeks, and a significant attenuation of fibronectin and tenascin expression from week 8 to 16 after re-implantation. In addition, keratocyte re-population could be found along the implanted RL interfaces. Our findings suggest that RL cryopreservation and re-implantation after ReLEx appears feasible, suggesting the possibility of potential reversibility of the procedure, and possible future uses of RLs in treating other corneal disorders and refractive errors.
To compare anterior segment parameters measured using a semi-automatic software (Zhongshan Angle Assessment Program, ZAP) applied to anterior segment optical coherence tomography (AS-OCT) images, with commonly used instruments.
Cross-sectional study of a total of 1069 subjects (1069 eyes) from three population-based studies of adults aged 40–80 years. All subjects underwent AS-OCT imaging and ZAP software was applied to determine anterior chamber depth (ACD), central corneal thickness (CCT), anterior and keratometry (K) – readings. These were compared to auto-refraction, keratometry and ocular biometry measured using an IOLMaster, ultrasound pachymeter and auto-refractor respectively. Agreements between AS-OCT (ZAP) and clinical instrument modalities were described using Bland-Altman, 95% limits of agreement (LOA).
The mean age of our subjects was 56.9±9.5 years and 50.9% were male. The mean AS-OCT (ZAP) parameters of our study cohort were: ACD 3.29±0.35 mm, CCT 560.75±35.07 µm; K-reading 46.79±2.72 D. There was good agreement between the measurements from ZAP analysis and each instrument and no violations in the assumptions of the LOA; albeit with a systematic bias for each comparison: AS-OCT consistently measured a deeper ACD compared to IOLMaster (95% LOA −0.24, 0.55); and a thicker CCT for the AS-OCT compared to ultrasound pachymetry (16.8±0.53 µm 95% LOA −17.3, 50.8). AS-OCT had good agreement with auto-refractor with at least 95% of the measurements within the prediction interval (P value <0.001).
This study demonstrates that there is good agreement between the measurements from the AS-OCT (ZAP) and conventional tools. However, small systematic biases remain that suggest that these measurement tools may not be interchanged.
Global shortage of donor corneas greatly restricts the numbers of corneal transplantations performed yearly. Limited ex vivo expansion of primary human corneal endothelial cells is possible, and a considerable clinical interest exists for development of tissue-engineered constructs using cultivated corneal endothelial cells. The objective of this study was to investigate the density-dependent growth of human corneal endothelial cells isolated from paired donor corneas and to elucidate an optimal seeding density for their extended expansion in vitro whilst maintaining their unique cellular morphology.
Established primary human corneal endothelial cells were propagated to the second passage (P2) before they were utilized for this study. Confluent P2 cells were dissociated and seeded at four seeding densities: 2,500 cells per cm2 (‘LOW’); 5,000 cells per cm2 (‘MID’); 10,000 cells per cm2 (‘HIGH’); and 20,000 cells per cm2 (‘HIGH×2’), and subsequently analyzed for their propensity to proliferate. They were also subjected to morphometric analyses comparing cell sizes, coefficient of variance, as well as cell circularity when each culture became confluent. At the two lower densities, proliferation rates were higher than cells seeded at higher densities, though not statistically significant. However, corneal endothelial cells seeded at lower densities were significantly larger in size, heterogeneous in shape and less circular (fibroblastic-like), and remained hypertrophic after one month in culture. Comparatively, cells seeded at higher densities were significantly homogeneous, compact and circular at confluence. Potentially, at an optimal seeding density of 10,000 cells per cm2, it is possible to obtain between 10 million to 25 million cells at the third passage. More importantly, these expanded human corneal endothelial cells retained their unique cellular morphology.
Our results demonstrated a density dependency in the culture of primary human corneal endothelial cells. Sub-optimal seeding density results in a decrease in cell saturation density, as well as a loss in their proliferative potential. As such, we propose a seeding density of not less than 10,000 cells per cm2 for regular passage of primary human corneal endothelial cells.
Human corneal endothelium; Human corneal endothelial cells; Primary cell culture; Cell density
To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK) using two different femtosecond lasers.
In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase™ femtosecond laser. Corneal sensitivity, tear break up time (TBUT), Schirmer’s test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively.
There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05), although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P < 0.05), 1 month (P < 0 .001), and 3 months (P < 0.001) postoperatively. A significantly greater reduction of corneal sensitivity was noted in eyes with a myopic spherical equivalent of −6.00 diopters (D) to −11.25 D as compared with eyes that had a relatively lower level of myopia of less than −6.00 D (P < 0.001). TBUT and Schirmer’s test values were significantly diminished at 1 week postoperatively (P < 0.04). Overall, corneal staining was significantly increased at 1 week postoperatively (P < 0.001). The level of myopia did not significantly affect postoperative changes in TBUT, Schirmer’s test values, or corneal staining (P > 0.05).
This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.
femtosecond laser; corneal sensitivity; tear film break-up time; Schirmer’s; corneal staining
To evaluate the feasibility of fibrin glue in Gundersen flap surgery.
Prospective case series.
Seven eyes of seven subjects who had undergone Gundersen flap surgery from 2009 to 2011 at the Singapore National Eye Centre, Singapore.
Review of case records for outcomes after Gundersen flap surgery.
Main outcome measures
Surgical success was defined as achieving a stable ocular surface. Complications to be noted included flap retraction or exposure of underlying corneal surface.
Surgical success was achieved in all eyes with significant reduction in ocular surface inflammation. No retractions were noted and recovery was uncomplicated.
Fibrin glue application is a viable alternative to sutures in Gundersen flap surgery. It reduces surgical downtime, gives faster ocular surface rehabilitation, and offers similar outcomes to conventional conjunctival flap surgery.
Gundersen; conjunctival flap; fibrin glue
This study compared the effects of implanting two interpenetrating polymer networks (IPNs) into rabbit corneas. The first (Implant 1) was based on PEG-diacrylate, the second (Implant 2) was based on PEG-diacrylamide. There were inserted into deep stromal pockets created using a manual surgical technique for either 3 or 6 months. The implanted corneas were compared with normal and sham-operated corneas through slit lamp observation, anterior segment optical coherence tomography, in vivo confocal scanning and histological examination. Corneas with Implant 1 (based on PEG-diacrylate) developed diffuse haze, ulcers and opacities within 3 months, while corneas with Implant 2 (based on PEG-diacrylamide) remained clear at 6 months. They also exhibited normal numbers of epithelial cell layers, without any immune cell infiltration, inflammation, oedema or neovascularisation at post-operative 6 month. Morphological studies showed transient epithelial layer thinning over the hydrogel inserted area and elevated keratocyte activity at 3 months; however, the epithelium thickness and keratocyte morphology were improved at 6 months. Implant 2 exhibited superior in vivo biocompatibility and higher optical clarity than Implant 1. PEG-diacrylamide-based IPN hydrogel is therefore a potential candidate for corneal inlays to correct refractive error.
To optimize fibrin glue (FG) spray for ophthalmic surgery using two spray applicators, EasySpray and DuploSpray systems, by varying the distance from point of application and the pressure/flow rate, and to compare the adhesive strength of sutured and sutureless (FG sprayed) conjunctival graft surgery in a rabbit model.
FG was sprayed on a 0.2 mm-thick sheet of paper using EasySpray by variously combining application distances of 2.5, 5, 7.5, and 10 cm with pressures of 10, 15, and 20 psi. DuploSpray was used at the same distances but with varying flow rates of 1 and 2 L/min. Subsequently, FG was sprayed on porcine corneas and FG thickness was analyzed by histology. In addition, adhesive strength of the conjunctival graft (0.5 × 0.5 cm) attached to the rabbit cornea by sutured and sutureless surgery (FG spray) was compared using a tension meter.
Histology measurements revealed that the FG thickness decreased with increases in distance and pressure of spray using the EasySpray applicator on paper and porcine corneal sections. The adhesive strength of the sutured conjunctival graft (41 ± 4.85 [kilopascal] KPa) was found to be higher than the graft attached by spraying (10 ± 2.3 KPa) and the sequential addition of FG (6 ± 0.714 KPa).
The EasySpray applicator formed a uniform spread of FG at a distance-pressure combination of 5 cm and 20 psi. The conjunctival graft attached with sutures had higher adhesive strength compared with grafts glued with a spray applicator. Although the adhesive strength of FG applied through the applicator was similar to the drop-wise sequential technique, the former was more cost effective because more samples could be sprayed compared with the sequential manual technique.
The standardization of the spray system for the application of FG in ophthalmology will provide an economical method for delivering consistent healing results after surgery.
fibrin glue; EasySpray; DuploSpray; adhesive strength; conjunctival graft surgery
Current treatments for reversible blindness caused by corneal endothelial cell failure involve replacing the failed endothelium with donor tissue using a one donor-one recipient strategy. Due to the increasing pressure of a worldwide donor cornea shortage there has been considerable interest in developing alternative strategies to treat endothelial disorders using expanded cell replacement therapy. Protocols have been developed which allow successful expansion of endothelial cells in vitro but this approach requires a supporting material that would allow easy transfer of cells to the recipient. We describe the first use of plastic compressed collagen as a highly effective, novel carrier for human corneal endothelial cells. A human corneal endothelial cell line and primary human corneal endothelial cells retained their characteristic cobblestone morphology and expression of tight junction protein ZO-1 and pump protein Na+/K+ ATPase α1 after culture on collagen constructs for up to 14 days. Additionally, ultrastructural analysis suggested a well-integrated endothelial layer with tightly opposed cells and apical microvilli. Plastic compressed collagen is a superior biomaterial in terms of its speed and ease of production and its ability to be manipulated in a clinically relevant manner without breakage. This method provides expanded endothelial cells with a substrate that could be suitable for transplantation allowing one donor cornea to potentially treat multiple patients.
We report a case of spontaneous Descemet’s membrane sweating of aqueous humor during a manual deep anterior lamellar keratoplasty (DALK) without perforation of Descemet’s membrane. An 81-year-old female developed a neurotrophic central ulcer with descemetocele in the right eye, and her visual acuity was count fingers at 30 cm. She was unresponsive to medical treatment, and an uneventful manual DALK was performed. Six months after surgery, unaided visual acuity improved to 6/30. Seven months after surgery, the patient had a decrease in visual acuity to count fingers in the same eye. She was diagnosed as having corneal melting with a central descemetocele in the previous lamellar graft. A repeat manual DALK graft was performed. Lamellar dissection was performed starting from the edge of descemetocele, proceeding to the corneal periphery and maintaining the surgical plane of the previous DALK. During the surgical procedure, continuous and localized sweating of aqueous through Descemet’s membrane was observed in the area of the descemetocele. After drying of the recipient bed, no visible perforation of Descemet’s membrane was found. After removal of the previous DALK graft, a new stromal lamellar graft was sutured. The surgery was concluded without complications. One day after surgery, the graft was clear, with no detachment of Descemet’s membrane. If Descemet’s membrane sweating is observed during DALK and there is no visible perforation, the reason may be a hidden micron perforation in an intact Descemet’s membrane. It is recommended to continue with surgery maintaining maximum diligence and low intraocular pressure to prevent extension of micron perforation.
deep anterior lamellar keratoplasty; perforation; Descemet’s membrane; sweating
The rabbit is a common animal model for ophthalmic research, especially corneal research. Ocular structures grow rapidly during the early stages of life. It is unclear when the rabbit cornea becomes mature and stabilized. We investigated the changes of keratometry, refractive state and central corneal thickness (CCT) with age. In addition, we studied the intra- and inter-observer reproducibility of anterior chamber depth (ACD) and anterior chamber width (ACW) measurements in rabbits using anterior segment-optical coherence tomography (AS-OCT).
The growth of New Zealand White rabbits (n = 16) were monitored from age 1 to 12 months old. Corneal keratometric and refractive values were obtained using an autorefractor/keratometer, and CCT was measured using an AS-OCT. Keratometry and CCT changed rapidly from 1 to 7 months and appeared to be stabilizing after 8 months. The reduction of corneal curvature was approximately 1.36 diopter (D)/month from age 1 to 7 months, but the change decelerated to 0.30 D/month from age 8 to 12 months. An increase of 10 μm/month in CCT was observed from age 1 to 7 months, but the gain was reduced to less than 1 μm/month from age 8 to 12 months. There was a hyperopic shift over the span of 12 months, albeit the increase in spherical equivalent was slow and gradual. Rabbits of random age were then selected for 2 repeated ACD and ACW measurements by 2 independent and masked observers. Bland-Altman plots revealed a good agreement of ACD and ACW measurements inter- and intra-observer and the ranges of 95% limit of agreement were acceptable from a clinical perspective.
Corneal keratometry, spherical equivalent refraction and CCT changed significantly during the first few months of life of rabbits. Young rabbits have been used in a large number of eye research studies. In certain settings, the ocular parametric changes are an important aspect to note as they may alter the findings made in a rabbit experimental model. In this study, we have also demonstrated for the first time a good between observer reproducibility of measurements of ocular parameters in an animal model by using an AS-OCT.
Cornea; Rabbit; Refractive; Keratometry; Anterior chamber; Reproducibility
The CorneaL GrAft Thickness Evaluation (COLGATE) system was recently developed to facilitate the evaluation of corneal graft thickness from OCT images. Graft thickness measurement can be a surrogate indicator for detecting graft failure or success. The purpose of this study was to determine the reproducibility of the COLGATE system in measuring DSAEK graft area between two observers.
This was a prospective case series in which 50 anterior segment OCT images of patients who had undergone DSAEK in either eye were analysed. Two observers (MW, AC) independently obtained the image analysis for the graft area using both semi automated and automated method. One week later, each observer repeated the analysis for the same set of images. Bland-Altman analysis was performed to analyze inter and intra observer agreement.
There was strong intraobserver correlation between the 2 semi automated readings obtained by both observers. (r = 0.936 and r = 0.962). Intraobserver ICC for observer 1 was 0.936 (95% CI 0.890 to 0.963) and 0.967 (95% CI 0.942 to 0.981) for observer 2. Likewise, there was also strong interobserver correlation (r = 0.913 and r = 0.969). The interobserver ICC for the first measurements was 0.911 (95% CI 0.849 to 0.949) and 0.968 (95% CI 0.945 to 0.982) for the second. There was statistical difference between the automatic and the semi automated readings for both observers (p = 0.006, p = 0.003). The automatic readings gave consistently higher values than the semi automated readings especially in thin grafts.
The analysis from the COLGATE programme can be reproducible between different observers. Care must be taken when interpreting the automated analysis as they tend to over estimate measurements.
Anterior segment optical coherence tomography; Descemet Stripping Automated Endothelial Keratoplasty; Graft thickness
To compare the results of laser in situ keratomileusis for myopia using WaveLight® Allegretto Wave® Eye-Q® and Technolas® 217z excimer lasers.
A retrospective, comparative case series of 442 eyes matched for age and myopia: half each were treated with Allegretto’s wavefront-optimized algorithm and Technolas PlanoScan. Outcome measures were postoperative mean logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA), manifest refraction spherical equivalent (MRSE), cylinder, safety and efficacy indices, refractive predictability, and optical zone size selection. Refractive predictability of a subgroup treated for −2.50 to −4.0 diopter (D) was analyzed separately.
At mean follow-up of 80.5 days, mean logMAR UCVA, mean MRSE and mean postoperative cylinder were 0.02 ± 0.07 (range −0.12 to 0.30), 0.27 ± 0.36 D (range −1.25 to 1.50 D) and −0.33 ± 0.30 D (range 0.00 to −1.50 D) for Allegretto versus 0.02 ± 0.08 (range −0.12 to 0.40), 0.095 ± 0.47 D (range −1.25 to 1.13 D) and −0.44 ± 0.5 2 D (range 0.00 to −2.25 D) for Technolas (P = 0.98, 0.80 and 0.006). Mean safety and efficacy indices were 1.05 ± 0.13 (0.75–1.33) and 0.97 ± 0.13 (0.50–1.33) for Allegretto and 1.07 ± 0.14 (0.75–1.49) and 0.97 ± 0.17 (0.40–1.49) for Technolas (P = 0.23 and 0.69). Proportions of eyes achieving postoperative MRSE within ±1.0 D, ±0.5 D, and ±0.25 D were 98.2%, 91.9% and 75.6% for Allegretto and 99.1%, 97.8% and 72.4% for Technolas (P = 0.68, 0.20 and 0.51). Mean optical zone size selected was 6.48 ± 0.10 mm (range 6.0–6.5 mm) for Allegretto and 6.38 ± 0.19 mm (range 5.6–6.6 mm) for Technolas (P < 0.001). Of the subgroup with treatment between −2.5 and −4.0 D, 86.8% and 58.5% of eyes treated with Allegretto achieved postoperative MRSE within ±0.50 D and ±0.25 D versus 70.4% and 44.4% for Technolas (P = 0.006 and 0.057).
No differences were seen in postoperative mean logMAR UCVA, MRSE, safety and efficacy indices between the two lasers. Allegretto produced less residual astigmatism, possibly improved refractive predictability, and required smaller optical zone selection.
LASIK; myopia; laser vision correction; conventional laser algorithm
To assess repeatability of the Zhongshan Assessment Program (ZAP) software measurement of Anterior Segment Optical Coherence Tomography (ASOCT) images and correlate with graft trephine diameter following Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)
Retrospectively evaluated interventional case series. 121 consecutive eyes undergoing DSAEK over a 26 month period underwent ASOCT imaging 1month after their surgery. ASOCT images were processed using ZAP software which measured the graft and cornea parameters including anterior and posterior graft arc length and cord length, posterior cornea arc length (PCAL) and anterior chamber width.
The graft measurements showed good repeatability on ASOCT using ZAP with high intra class coefficient and small variation in the coefficient of variation. On ASOCT, the mean recipient PCAL was 12.99+/−0.69mm and the anterior chamber width was 11.16+/−0.57mm. The mean Graft anterior arc length was 9.69+/−0.66mm and the mean Graft anterior cord length was 8.92+/−2.94mm. The mean graft posterior arc length was 9.24+/−0.75mm and the mean graft posterior cord length was 8.15+/−0.57mm. Graft posterior arc length (rho=0.788, p< 0.001) correlated best with intra-operative graft trephine diameter. The mean ratio of posterior graft arc length to PCAL was 0.712 +/− 0.056.
We have validated the repeatability of the ZAP software for DSAEK graft measurements from ASOCT images and shown that the graft arc length parameters calculated from the ASOCT images correlate well with the intra-operative graft trephine diameter. This software may help surgeons determine the optimal DSAEK graft size based on pre-operative ASOCT measurements of the recipient eye.
Small incision lenticule extraction or SMILE is a novel form of ‘flapless’ corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3 months post-operatively.
Single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 diopter (D)) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-masked trial, subjects and their caregivers will be masked to the assigned treatment in each eye.
This novel trial will provide information on whether SMILE has comparable, if not superior, refractive outcomes compared to the established LASIK for myopia, thus providing evidence for translation into clinical practice.
Refractive surgery; Laser in situ keratomileusis; Small incision lenticule extraction
Corneal transplantation has rapidly evolved from full-thickness penetrating keratoplasty (PK) to selective tissue corneal transplantation, where only the diseased portions of the patient's corneal tissue are replaced with healthy donor tissue. Descemet's membrane endothelial keratoplasty (DMEK) performed in patients with corneal endothelial dysfunction is one such example where only a single layer of endothelial cells with its basement membrane (10–15 µm in thickness), Descemet's membrane (DM) is replaced. It is challenging to replace this membrane due to its intrinsic property to roll in an aqueous environment. The main objective of this study was to determine the effects of fibrin glue (FG) on the biomechanical properties of DM using atomic force microscopy (AFM) and relates these properties to membrane folding propensity.
Fibrin glue was sprayed using the EasySpray applicator system, and the biomechanical properties of human DM were determined by AFM. We studied the changes in the “rolling up” tendency of DM by examining the changes in the elasticity and flexural rigidity after the application of FG. Surface topography was assessed using scanning electron microscopy (SEM) and AFM imaging. Treatment with FG not only stabilized and stiffened DM but also led to a significant increase in hysteresis of the glue-treated membrane. In addition, flexural or bending rigidity values also increased in FG-treated membranes.
Our results suggest that fibrin glue provides rigidity to the DM/endothelial cell complex that may aid in subsequent manipulation by maintaining tissue integrity.
The purpose of this study was to compare endothelial cell counts after Descemet’s stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty in Asian eyes.
This was a retrospective study of patients from our prospective Singapore Corneal Transplant Study cohort who received corneal transplantation in 2006–2008. We compared eyes that underwent DSAEK or penetrating keratoplasty for Fuchs’ endothelial dystrophy or pseudophakic and aphakic bullous keratopathy. Clinical data, and donor and recipient characteristics were recorded. Of 241 patients who met our inclusion criteria, 68 underwent DSAEK and 173 underwent penetrating keratoplasty. The main outcome measure was endothelial cell loss at 1 year. Secondary outcome measures were graft survival and visual outcomes at 1-year follow-up.
There were no significant differences in baseline characteristics of patients between the treatment groups. Percent endothelial cell loss at 1-year follow-up was greater in penetrating keratoplasty eyes (40.9% ± 2.9%) compared with DSAEK eyes (22.4% ± 2.3%; P < 0.001). DSAEK-treated eyes had significantly superior uncorrected visual acuity (mean difference = 0.42 ± 0.0059; P < 0.001) and best spectacle-corrected visual acuity (mean difference = 0.14 ± 0.032; P < 0.001) as compared with penetrating keratoplasty-treated eyes. Penetrating keratoplasty-treated eyes had worse astigmatism as compared with DSAEK-treated eyes (−3.0 ± 2.1 versus −1.7 ± 0.8; P < 0.001). Graft survival at 1 year was comparable in both groups, ie, 66/68 (97.0%) DSAEK-treated eyes versus 158/173 (92.0%) of penetrating keratoplasty-treated eyes had clear grafts (P = 0.479).
We report lower percent endothelial cell loss comparing DSAEK and penetrating keratoplasty at 1-year follow-up in Asian eyes, with comparable graft survival rates in both groups.
Descemet’s stripping automated endothelial keratoplasty; endothelial cell count; penetrating keratoplasty
To evaluate the intraoperative changes in the donor lenticule, recipient cornea, and the reduction of interface fluid thickness during Descemet’s stripping and automated endothelial keratoplasty with EndoGlide™ (Angiotech Pharmaceuticals Inc, Vancouver, Canada) donor insertion, using intraoperative spectral-domain optical coherence tomography.
Prospective observational case series of patients underwent Descemet’s stripping and automated endothelial keratoplasty using the EndoGlide inserter. Spectral-domain optical coherence tomography (iVue; Optovue Inc, Fremont, CA) with a handheld probe was used to image the cornea and anterior chamber. Standardized software was used to measure interface fluid gap, host cornea, and donor lenticule thicknesses during the following surgical stages of Descemet’s stripping and automated endothelial keratoplasty: (1) after donor insertion and immediately before full air tamponade; (2) after air tamponade and expression of fluid from venting incisions; (3) at 6 minutes of air tamponade; and (4) at 10 minutes of air tamponade.
Ten patients with a mean age of 74.9 ± 11.8 years were recruited. Spectral-domain optical coherence tomography measurements of the interface fluid gap after fluid was expressed through the venting incisions (P < 0.001), at 6 minutes of air tamponade (P < 0.001) and at 10 minutes of air tamponade (P < 0.001 and P = 0.001, respectively), were significantly decreased compared to the measurements immediately before air tamponade. Donor thickness increased significantly at 6 minutes of air tamponade (P = 0.004) but reduced by 10 minutes compared to immediately before air tamponade.
Significant intraoperative changes in the donor, recipient cornea, and interface fluid thickness occurred following endothelial keratoplasty donor insertion.
Descemet’s stripping and automated endothelial keratoplasty; spectral-domain optical coherence tomography
The culture of human corneal endothelial cells (CECs) is critical for the development of suitable graft alternative on biodegradable material, specifically for endothelial keratoplasty, which can potentially alleviate the global shortage of transplant-grade donor corneas available. However, the propagation of slow proliferative CECs in vitro can be hindered by rapid growing stromal corneal fibroblasts (CSFs) that may be coisolated in some cases. The purpose of this study was to evaluate a strategy using magnetic cell separation (MACS) technique to deplete the contaminating CSFs from CEC cultures using antifibroblast magnetic microbeads. Separated “labeled” and “flow-through” cell fractions were collected separately, cultured, and morphologically assessed. Cells from the “flow-through” fraction displayed compact polygonal morphology and expressed Na+/K+ATPase indicative of corneal endothelial cells, whilst cells from the “labeled” fraction were mostly elongated and fibroblastic. A separation efficacy of 96.88% was observed. Hence, MACS technique can be useful in the depletion of contaminating CSFs from within a culture of CECs.
To investigate the role of Tafazzin (TAZ) protein in regulating the proliferation of normal human conjunctiva epithelial cells and epithelial cells from pterygium tissue.
Conjunctiva epithelial cells were cultured in keratinocytes growth medium and treated with transformation growth factor β (TGFβ) to analyze the expression and translocation of TAZ protein by immunostaining and BrdU analysis. Immortalized conjunctiva epithelial cells (NHC) were treated with TGFβ, targeting siRNA, TGFβ receptor antibody or TGFβ receptor inhibitor, to study the involvement of TAZ and TGFβ signaling pathway in conjunctiva cell proliferation by cell adhesion assay. Conjunctiva tissues from a normal human eye and an eye with pterygium disease were collected for histological analyses and western blot to evaluate the TAZ protein expression in vivo.
TAZ expression was upregulated in mitotic conjunctiva epithelial cells, proliferating conjunctiva epithelial cells, TGFβ treated conjunctiva epithelial cells and human pterygium epithelium. TAZ siRNA induced less conjunctiva epithelial cell growth. Moreover, TGFβ receptor antibody and TGFβ receptor inhibitor rescued this anti-proliferative effect of TAZ siRNA.
TAZ is involved in human conjunctiva epithelial cells proliferation via regulating TGFβ signaling pathway.
Consistent expansion of human corneal endothelial cells (hCECs) is critical in the development of tissue engineered endothelial constructs. However, a wide range of complex culture media, developed from different basal media have been reported in the propagation of hCECs, some with more success than others. These results are further confounded by donor-to-donor variability. The aim of this study is to evaluate four culture media in the isolation and propagation of hCECs isolated from a series of paired donor corneas in order to negate donor variability.
Isolated primary hCECs were cultured in four previously published medium coded in this study as: M1-DMEM; M2-OptiMEM-I; M3-DMEM/F12, & M4-Ham's F12/M199. Primary hCECs established in these conditions were expanded for two passages and analyzed for (1) their propensity to adhere and proliferate; (2) their expression of characteristic corneal endothelium markers: Na+K+/ATPase and ZO-1; and (3) their cellular morphology throughout the study. We found that hCECs isolated in all four media showed rapid attachment when cultured on FNC-coated dishes. However, hCECs established in the four media exhibited different proliferation profiles with striking morphological differences. Corneal endothelial cells cultured in M1 and M3 could not be propagated beyond the first and second passage respectively. The hCECs cultured in M2 and M4 were significantly more proliferative and expressed markers characteristics of human corneal endothelium: Na+K+/ATPase and ZO-1. However, the unique morphological characteristics of cultivated hCECs were not maintained in either M2 or M4 beyond the third passage.
The proliferative capacity and morphology of hCECs are vastly affected by the four culture media. For the development of tissue engineered graft materials using cultured hCECs derived from the isolation methodology described in this study, we propose the use of proliferative media M2 or M4 up to the third passage, or before the cultured hCECs lose their unique cellular morphology.
Descemet’s stripping automated endothelial keratoplasty (DSAEK) has been shown to have superior refractive and visual results compared with penetrating keratoplasty, but higher rates of primary graft failure (PGF). This paper presents donor and surgical risk factors for PGF in DSAEK cases in Asian eyes.
Retrospective case-control study.
All consecutive patients who underwent DSAEK at a tertiary referral teaching hospital from March 2006–December 2008.
Donor details analyzed were: age of donor, cause of donor death, death to harvesting time, donor storage time, distribution distance of tissue, preoperative endothelial cell count. Surgical factors analyzed were: donor diameter, donor thickness, and method of donor insertion. These risk factors in cases of PGF were compared with patients with successful DSAEK as the control group.
Main outcome measure
A total of 124 DSAEK procedures were performed. Six DSAEK procedures (five eyes of five patients; one eye with two failures) resulted in PGF (4.8%). Significant risk factors were found for PGF to include graft insertion using a folding technique (odds ratio [OR], 34.03; 95% confidence interval [CI], 3.75–314.32; P = 0.0017) and a small donor diameter (OR, 39.94; 95% CI, 2.18–732.17; P = 0.013).
The results of this study suggest that in Asian eyes with shallow anterior chambers, surgical trauma relating to the technique of donor insertion, and the use of a small donor are major risk factors for PGF following DSAEK.
DSAEK; PGF; penetrating keratoplasty