Deep anterior lamellar keratoplasty for keratoconus

Effect of Increasing Povidone-Iodine Exposure on Corneal Epithelium and Impact on Donor Rim Cultures

PURPOSE

The purpose of this study was to assess the effect of a second povidone-iodine (PVP-I) application at the time of donor tissue recovery on overall tissue quality and to analyze the rate of positive fungal and bacterial rim cultures before and after implementing increased PVP-I exposure.

METHODS

The left cornea was recovered after a single application of PVP-I, while the right cornea was recovered after double PVP-I application in research-consented donors. The epithelial cell death rate was estimated using viability assay in corneal whole mounts under 10× objective (n = 5). Clinical characteristics of epithelium, stroma, and endothelium; positive rim culture rate; and incidences of infectious postoperative adverse reactions were compared for a period of 14 months before and after implementation of increased PVP-I protocol.

RESULTS

The average epithelial cell death rate was unaltered between single and double PVP-I exposure groups. We observed a modest 10% increase in the number of tissues with mild edema after implementation of increased PVP-I exposure. Nonetheless, the percentage of tissues with moderate or severe edema was unaltered. The average positive rim culture rate decreased from 1.17% to 0.88% (P = 0.075) after implementation of the double PVP-I soak procedure. There has been only one report of infectious postoperative adverse reactions since this procedure change. By contrast, there were 5 reports for a period of 14 months before implementation of this protocol.

CONCLUSIONS

These results indicate that new donor preparation methods with an additional 5 minutes of PVP-I exposure do not affect tissue quality, reduce positive rim cultures, and lead to lower incidence of postoperative infection.

Comparison of penetrating keratoplasty and deep anterior lamellar keratoplasty in keratoconus eyes with vernal keratoconjunctivitis

Purpose:

The purpose of the study is to compare outcomes after penetrating keratoplasty (PK) against deep anterior lamellar keratoplasty (DALK) for keratoconus in patients with vernal keratoconjunctivitis (VKC).

Methods:

Keratoconic patients with VKC who received PK (n = 55, group 1) or DALK (n = 62, group 2) were retrospectively enrolled. The Student’s t test, Mann–Whitney test, Fisher’s exact test, chi-square test, and Kaplan–Meier survival curve were used to compare outcomes between the groups.

Results:

The follow-up period was 59.4 ± 44.1 and 62.4 ± 38.9 months in groups 1 and 2, respectively (p = 0.70). Postoperative best spectacle-corrected visual acuity was 0.24 ± 0.18 and 0.29 ± 0.19 logMAR, respectively (p = 0.13). Graft rejection occurred in 34.6% and 25.8% of eyes in groups 1 and 2, respectively (p = 0.30). Groups 1 and 2 were comparable in the rates of cataract (3.6% and 12.9%, respectively, p = 0.07) and high intraocular pressure (3.6% and 8.1%, respectively, p = 0.31). Compared with the eyes with inactive VKC, PK eyes that experienced postoperative disease reactivation had a higher rate of suture abscesses (10.9% versus 50.0%, respectively, p = 0.01) and suture-tract vascularization (6.5% versus 33.3%, respectively, p = 0.03). Similarly, disease reactivation significantly increased suture abscesses from 27.3% to 51.7% (p = 0.03) and suture-tract vascularization from 18.2% to 49.6% (p = 0.005) in the DALK group. The graft survival rates were 95.3% in group 1 and 87.9% in group 2 at the 4-year follow-up, with mean durations of 14.4 and 11.1 months, respectively (p = 0.20).

Conclusion:

The results indicate no difference in outcomes between PK and DALK for keratoconus in patients with VKC. Postoperative VKC reactivation increased the rate of suture-related problems after both techniques of keratoplasty.

Topical Estrogen Therapy for Hyperopia Correction in Vivo

Purpose

In vitro studies found that 17β-estradiol (estrogen) modulates corneal biomechanical properties and reduces tissue stiffness. Therefore we hypothesized that topical estrogen might affect the refractive properties of the cornea, inducing a myopic shift.

Methods

Twelve female New Zealand white rabbits 16 weeks old were used. The rabbits were randomly divided to either the treatment group receiving 1.5% (w/v) estrogen eye drops or a control group receiving vehicle only (n = 6 each group). Both groups were given drops (50 µL) to the right eye every 12 hours for 35 days. Ocular examination, pachymetry, intraocular pressure (IOP), keratometry, and refraction were evaluated at baseline and on a weekly basis.

Results

No significant differences were observed between the two groups at baseline in all outcome measures. Both groups displayed corneal flattening and a hyperopic shift. However, the change rate was slower in the treatment group. Repeated measurements analysis revealed a statistically significant difference in keratometry readings between groups (P = 0.034) with steeper keratometry by up to 0.6 diopters in the treatment group. The difference between the two groups diminished and became statistically insignificant after treatment cessation. No significant changes were observed in IOP and pachymetry throughout the study period. No side effects were observed in either group.

Conclusions

Estrogen eye drops induced a myopic shift in keratometry readings. These results suggest that corneal refractive power might be manipulated pharmacologically. Further studies on the physiology behind this change are warranted to facilitate a pathway for development of novel pharmacologic treatments to correct refractive errors.

Approaches toward enhancing survival probability following deep anterior lamellar keratoplasty

The greatest advantage of deep anterior lamellar keratoplasty over full-thickness corneal transplantation is the elimination of graft failure caused by endothelial rejection. Despite this advantage, a deep anterior lamellar keratoplasty graft can fail because of several factors, such as complications related to the donor-recipient interface, graft epithelial abnormalities, graft vascularization, stromal graft rejection, and recurrence of herpetic keratitis. Increased deep anterior lamellar keratoplasty graft survival is mainly built upon optimization of the ocular surface to provide a hospitable environment for the graft. Any predisposing factors for graft epithelial abnormalities, corneal neovascularization, and preexisting vernal keratoconjunctivitis should be identified and treated preoperatively. Prompt recognition and appropriate treatment of interface-related complications and stromal graft rejection usually result in good anatomic outcomes, with no detrimental effects on vision.

The effect of estrogen and progesterone on porcine corneal biomechanical properties

PURPOSE

To determine the effect of the hormones estrogen and progesterone on the biomechanical properties of porcine corneas.

METHODS

Thirty fresh porcine corneas were acquired from an abattoir. The corneas were equally divided into three groups. Groups were incubated for 1 week in Eusol-C solution containing supra-physiologic concentrations of estrogen, progesterone, or control (no added hormone). After incubation, the central corneal thickness (CCT) of each cornea was measured using an electronic caliper, and then the corneas were cut into strips. The strips were then clamped in the pneumatic jaws of a computer-controlled biomaterial tester (Instron 4502, USA) and stretched at a constant rate of 1 mm/min until tissue rupture while constantly recording the stress and strain of the tissue. Stress-strain curves were plotted and Young's modulus was calculated for each corneal strip.

RESULTS

Average corneal thickness was 873.5 ± 143.1 μm for the control group, 928.0 ± 97.7 μm for the estrogen group, and 922.0 ± 116.7 μm for the progesterone group (data presented as mean ± SD). There was no statistically significant difference between the groups regarding the CCT (p = 0.89). The average Young's modulus was 17.00 ± 3.46 MPa for the control group, 16.95 ± 6.83 MPa for the progesterone group, and 12.33 ± 3.24 MPa for the estrogen group. The difference between the control and estrogen groups was statistically significant (p = 0.018) while the difference between the control and progesterone groups was not (p = 0.72).

CONCLUSION

Estrogen has a relaxing effect on the porcine cornea, resulting in reduced stiffness of the tissue. Progesterone has no significant effect on the biomechanical properties of porcine corneas. Estrogen and progesterone do not significantly affect CCT.

Prevalence of microbial contamination in donor corneas

BACKGROUND/PURPOSE:

Postoperative infection is the most disastrous complication of penetrating keratoplasty (PK). Corneoscleral rim culture provided information regarding subsequent infections. Our aims were to identify the incidence of microbial contamination in donor corneas and to report the recovery of bacteria with two culture methods, i.e., conventional culture media after aerobic/anaerobic cotton swabs and blood culture media (Fastidious Antibiotic Neutralization [FAN]).

MATERIALS AND METHODS:

A total of 118 patients underwent PK. Corneoscleral rim cultures were performed using aerobic/anaerobic culture cotton swabs (Transystem™, COPAN, Italia) with subsequent convention media and blood culture media (FAN bottle, BD BACTEC™, USA). The results of the different methods were reported and analyzed.

RESULTS:

Microorganisms were recovered from 24 in total 118 cases (20.3%, n = 118), 14 from blood culture media (FAN) (11.8%, n = 118), 9 from conventional culture media after aerobic/anaerobic cotton swabs (7.63%, n = 118), and 2 from fungus culture (1.69%, n = 118). The most commonly identified pathogen was coagulase-negative Staphylococcus (CoNS) (n = 13, 54.2%), and more isolates of CoNS and staphylococcus aureus were recovered from blood culture media (FAN) than those from conventional culture media after aerobic/anaerobic cotton swabs (13 vs. 4, P = 0.05). Conversely, more nonfermentative Gram-negative bacilli were recovered from conventional culture media after aerobic/anaerobic cotton swabs. None of the 24 cases with positive corneoscleral rim cultures reported ocular infection for the recipients in at least 6 months’ follow-up.

CONCLUSION:

The conventional culture media after aerobic/anaerobic cotton swabs and blood culture media (FAN) did not yield identical isolates of bacteria. The blood culture media (FAN) could further yield Gram-positive bacteria in addition to those recovered from convention media. It seemed adding gentamicin and streptomycin could achieve bacteriostatic effect instead of the bactericidal effect. The administration of postoperative antibiotic in the recipient was suggested.

Microbiological Screening of Hypothermic Preserved Donor Corneas in Keratoplasty

Purpose: To determine the prevalence, risk factors and microbial profiles of donor corneal contamination and its association with postoperative infection. Materials and Methods: 1348 hypothermic preserved donor corneas were screened during keratoplasty to assess the impacts of donor age, gender, cause of death and corneal preservation time on the contamination risk. The microbial spectrum and antibiotic sensitivity of causative microorganisms and the prognostic role of corneoscleral rim cultures were analyzed. Results: 111 donor corneas (8.2%) had positive microbial cultures, with 84 contaminated by bacteria, 25 by fungi and 2 by both. Acinetobacter baumannii complex (19.8%) and Candida spp. (9.0%) were the most commonly isolated bacteria and fungi, respectively. Two patients (1.8%) who received contaminated corneal buttons developed postoperative infections. Death due to cardiac disease led to more corneal contaminations than death due to brain disease (odds ratio (OR) = 2.59, P = .009). Longer preservation time was associated with a trend toward increasing contamination rate (from 8.3% to 15.0%). Moreover, fungal-contaminated corneas were preserved longer than bacterial-contaminated corneas (6.6 ± 4.5 versus 10.2 ± 5.4 days, P = .001). Corneas from donors who died from cardiac diseases and trauma showed the highest prevalence of bacterial (10.9%) and fungal (2.6%) contamination, respectively. Antibiotic sensitivity testing revealed that the third-generation fluoroquinolone levofloxacin had high rates of susceptibility to both gram-positive (G+) (60.0%) and gram-negative (G-) (44.6%) bacteria. Conclusions: The causes of donor corneal contamination are multifactorial. The antibiotic resistance rate of contaminating microbes seems to be increasing. Whether antibiotic usage in storage medium and postoperative prophylaxis should be updated accordingly warrants further investigation.

Comparison of clinical outcomes of deep anterior lamellar keratoplasty and excimer laser assisted anterior lamellar keratoplasty in keratoconus

AIM

To compare and evaluate the clinical outcomes of deep anterior lamellar keratoplasty (DALK) and excimer laser assisted anterior lamellar keratoplasty (ELLK) in eyes with keratoconus.

METHODS

In this study, 57 eyes of 56 patients operated between 2013 to 2017 were included. Thirty-one eyes underwent big-bubble DALK and twenty-six eyes underwent ELLK. Preoperative and at control visits complete ophthalmic examination was performed.

RESULTS

The mean patient age at the time of DALK surgery was 27y and mean follow-up period was 21±5.4mo. The mean patient age at the time of ELLK surgery was 27y and mean follow-up period was 40±18mo. Mean best spectacle corrected visual acuity (BSCVA) at postoperative period was significantly higher for DALK group (0.66±0.11) versus ELLK group (0.4±0.2) (P<0.05). Descemet's membrane microperforation was occurred in 7 patients in DALK group versus in 1 patient in ELLK group. In 4 eyes, interface irregularity was developed in ELLK group. None of the patients in follow-up had graft rejection in both groups.

CONCLUSION

In ELLK group, complication rate is lower, the surgical technique is simpler, faster and safer and also ELLK requires less experience with respect to DALK. Further, DALK can be performed unless satisfactory visual acuity is achieved after ELLK.

Graft rejection-like reactions in the early postoperative period after deep anterior lamellar keratoplasty for keratoconus: a retrospective study

Background

Deep anterior lamellar keratoplasty (DALK) is indicated to correct high astigmatism in patients with keratoconus (KC) and no evidence of Descemet’s membrane rupture. However, some patients with KC experience graft rejection-like inflammatory reactions within 2 months (usually in the first week) after DALK. The aim of this study was to identify the characteristics and influencing factors of these reactions by reviewing the records of patients who underwent DALK or penetrating keratoplasty (PKP) for KC or other corneal problems.

Methods

We retrospectively reviewed the medical records of patients who underwent DALK for KC (DALK/KC), PKP for KC (PKP/KC), or DALK for other corneal problems (DALK/non-KC) at Ban Buntane Hotokukai Hospital between January 2006 and December 2015 and who were followed for more than 1 year. We collected data on the characteristics and incidence of severe inflammatory graft reactions in the early postoperative phase (ie, within 2 months after keratoplasty) and visual outcomes after these inflammatory reactions.

Results

Postoperative inflammatory reactions characterized by persistent epithelial defects, loose suture with infiltration, and vessel invasion occurred in seven of eleven DALK/KC patients, three of 50 DALK/non-KC patients, and none of five PKP/KC patients. These reactions were nonresponsive to topical steroids, and suture removal was required. Although a clear corneal graft in the pupillary area was obtained and best-corrected visual acuity was good after the resolution of inflammation, a risk of corneal astigmatism remained.

Conclusion

The incidence of these reactions in the early postoperative period is high after DALK for KC. These reactions do not respond well to topical steroids, and suture removal may be required, which may cause high astigmatism after the inflammation subsides. Lamellar keratoplasty should be considered carefully for patients with KC.

Incidence and Outcomes of Positive Donor Rim Cultures and Infections in the Cornea Preservation Time Study

PURPOSE

To assess donor rim culture results and outcomes of ocular infections in the Cornea Preservation Time Study (CPTS).

METHODS

Donor corneal rim cultures were optional. Donor characteristics were assessed for association with positive cultures using the Fisher exact test and Poisson regression analyses. Incidence rates of ocular infections were estimated, and 95% confidence intervals were calculated.

RESULTS

Cultures were performed in 784 (58.9%) of the 1330 cases. For the 0 to 7-day versus 8 to 14-day preservation time groups, respectively, positive fungal growth occurred in 10 of 397 (2.5%) versus 5 of 387 (1.3%) corneas (P = 0.30), whereas positive bacterial cultures occurred in 6 of 397 (1.5%) versus 4 of 387 (1.0%) corneas (P = 0.75). Surgeon-prepared tissue remained a significant risk for positive fungal cultures [relative risk (RR) of surgeon- versus eye-bank-prepared, 2.85; 95% CI (1.02-7.98)], whereas younger donors [RR per year of age, 0.96; 95% CI (0.93-1.00)] and accidental death donors [RR of accident versus disease, 3.71; 95% CI (1.36-10.13)] were at a greater risk for positive bacterial cultures. Fungal infection (Candida glabrata) developed in 1 (6.7%) of 15 recipients with a positive fungal culture, and no recipient infections occurred with positive bacterial culture. With one additional fungal keratitis (Candida albicans) and one bacterial endophthalmitis (E. coli) with no rim culture performed, a total of 2 of 1330 eyes (0.15%) developed fungal and 1/1330 eyes (0.08%) developed bacterial postkeratoplasty infections.

CONCLUSIONS

A longer preservation time was not associated with a higher rate of positive donor rim cultures. The overall rate of infection across the entire cohort was low.

The value of corneoscleral rim cultures in keratoplasty: a systematic review and cost-effectiveness analysis

PURPOSE

This study evaluated the performance of donor corneoscleral rim cultures for predicting infection after corneal transplantation, and determines if there is a correlation between positive corneoscleral rim cultures and postkeratoplasty infection.

DESIGN AND DATA SOURCES

This was a systematic review, prognostic accuracy analysis, and cost-effectiveness analysis. Databases searched were: Medline (Ovid), Embase (Ovid), CINAHL, Cochrane Library, Web of Science, and BioSis Previews. Grey literature was also explored.

MATERIALS AND METHODS

A systematic review was conducted to locate published and unpublished studies. All studies examining corneal button contamination and its association with endophthalmitis and keratitis posttransplantation were included. Extracted data were used to calculate sensitivity, specificity, positive predictive value, and negative predictive value. Cost data from the London Laboratory Services Group in London, ON were used to calculate the cost-effectiveness of culturing donor rim cultures.

RESULTS

Of 7,870 grafts, 954 had a positive rim culture (12.1%), with 12 patients going on to develop keratitis or endophthalmitis (1.3%). The prevalence of keratitis and endophthalmitis in this study was 0.15%, and the positive predictive value 1.5%. Of the 12 infections, nine were fungal and three bacterial. The estimated cost of a positive and negative test result was CAD$45.99 and $14.15, respectively. The cost to run all 7,870 tests was estimated to be $141,735.86, with an incremental cost-effectiveness ratio of $40,215.70.

CONCLUSION

There was a significant divergence between bacterial and fungal rim-culture results. Bacterial cultures predicted clinical infection poorly, did not change management, and were expensive. Fungal cultures predicted clinical infection in over 10% of patients, had the potential to change management, and were 40% less expensive than full rim culturing (bacterial and fungal tests). Fungal rim cultures may be considered in areas where fungal infection rates are high.

Comparison of Outcomes in Patients Who Underwent Deep Anterior Lamellar Keratoplasty and Those Converted to Penetrating Keratoplasty

OBJECTIVES

To compare clinical outcomes of cases who underwent deep anterior lamellar keratoplasty (DALK) and cases who were converted to penetrating keratoplasty (PKP) from DALK surgery.

MATERIALS AND METHODS

The records of 54 patients for whom DALK surgery was planned and were operated for different diagnoses between March 2013 and June 2015 were retrospectively analyzed. Patients were divided into two groups: group 1 (PKP group) consisted of 23 cases who were converted to PKP due to Descemet's membrane perforation at any stage of surgery; group 2 (DALK group) consisted of 31 patients whose surgery could be completed as DALK. Preoperative and postoperative follow-up results were evaluated in each group.

RESULTS

Corrected distance visual acuity (CDVA) increased in the postoperative period according to baseline in both groups. However, there was no statistically significant difference in the rates of CDVA increase between the groups (p=0.142). The mean astigmatism measured by corneal topography at final examination was 5.8±2.3 diopters in group 1 and 5.4±1.8 diopters in group 2. The difference between groups was not statistically significant (p=0.430). The groups were not statistically different regarding postoperative pachymetry (p=0.453). The grafts in all 54 patients (100%) were clear at final postoperative examination. There were no statistically significant differences between the groups in terms of postoperative complications.

CONCLUSION

Similar clinical outcomes were obtained in our study for patients who underwent DALK and those whose procedure was converted from DALK to PKP.

[Update: Deep anterior lamellar keratoplasty (DALK) for keratoconus. When, how and why]

BACKGROUND

The treatment of keratoconus has been significantly expanded in recent years. In addition to the previous options for correction by fitting hard contact lenses and penetrating keratoplasty (PK), corneal cross-linking and lamellar transplantation techniques have been added.

OBJECTIVE

The aim of this review article is to highlight currently available options for minimization of complications and standardization of deep anterior lamellar keratoplasty (DALK) for keratoconus.

MATERIAL AND METHODS

This article summarizes our own data and gives a review of the literature in PubMed.

RESULTS

Performing DALK can provide keratoconus patients with corneal grafts with considerably longer graft survival and a reduced risk of complications.

CONCLUSION

The DALK procedure provides numerous advantages over PK, especially the reduced intraoperative opening of the eye, which thus reduces the risk of serious intraoperative complications. A further benefit is the complete absence of postoperative endothelial immune reactions as the recipient's endothelium remains untouched. The absence of endothelial immune reactions is especially advantageous for young patients with keratoconus and patients with an increased risk of graft rejection, e.g. in atopic dermatitis; however, there are also typical complications of DALK that do not occur during PK. The outlined strategies for standardization of DALK and avoidance of intraoperative and postoperative complications should make DALK safer and more reproducible and lead to possible establishment as a standard procedure in keratokonus.

Current techniques of lamellar keratoplasty for keratoconus

In recent years, there has been a considerable interest regarding the concept of lamellar keratoplasty (LK), which contributed in spreading the use of this procedure in the treatment of keratoconus. This is a new frontier in corneal surgery that minimizes trauma on the recipient patient since it works on a "closed bulb". The LK surgery, in fact, aims to selectively replace diseased corneal stroma, leaving the healthy endothelium. The main advantage of LK is to avoid major causes of failure of penetrating keratoplasty as immunological rejection, and the late mismatch in the transplanted cornea, thus increasing the life of transplantation. In the last decade, several techniques of LK have been proposed, depending on how the anterior portion of the recipient cornea is removed. This article, through a literary research reviews the various emerging techniques of anterior lamellar surgery for the management of keratoconus, analyzing their indications, visual outcomes, and rate of complications.

Intraoperative management of macroperforations of Descemet's membrane in deep anterior lamellar keratoplasty

Background

To describe a surgical approach for the completion of pre-descemetic deep anterior lamellar keratoplasty (pdDALK) in the presence of a macroperforation of Descemet’s membrane (DM).

Methods

Using case notes, we recorded the details of the intra- and perioperative course of patients who underwent successful pdDALK in the presence of macroperforation. A literature search of pdDALK techniques available to the corneal surgeon in a similar scenario was undertaken.

Results

In two very different scenarios with intra- or preoperative perforation of DM, a centripetal layered lamellar dissection was performed and allowed completion of pdDALK with a residual recipient central stromal thickness of 36 and 115 µm and good visual outcome.

Conclusion

Despite very different scenarios, a centripetal layered lamellar dissection offers an approach for the completion of pdDALK in the presence of a macroperforation.

Glucocorticoid action in human corneal epithelial cells establishes roles for corticosteroids in wound healing and barrier function of the eye

Glucocorticoids play diverse roles in almost all physiological systems of the body, including both anti-inflammatory and immunosuppressive roles. Synthetic glucocorticoids are one of the most widely prescribed drugs and are used in the treatment of conditions such as autoimmune diseases, allergies, ocular disorders and certain types of cancers. In the interest of investigating glucocorticoid actions in the cornea of the eye, we established that multiple cell types in mouse corneas express functional glucocorticoid receptor (GR) with corneal epithelial cells having robust expression. To define glucocorticoid actions in a cell type-specific manner, we employed immortalized human corneal epithelial (HCE) cell line to define the glucocorticoid transcriptome and elucidated its functions in corneal epithelial cells. Over 4000 genes were significantly regulated within 6 h of dexamethasone treatment, and genes associated with cell movement, cytoskeletal remodeling and permeability were highly regulated. Real-time in vitro wound healing assays revealed that glucocorticoids delay wound healing by attenuating cell migration. These functional alterations were associated with cytoskeletal remodeling at the wounded edge of a scratch-wounded monolayer. However, glucocorticoid treatment improved the organization of tight-junction proteins and enhanced the epithelial barrier function. Our results demonstrate that glucocorticoids profoundly alter corneal epithelial gene expression and many of these changes likely impact both wound healing and epithelial cell barrier function.

Visual Outcomes of Successful versus Failed Big-Bubble Deep Anterior Lamellar Keratoplasty for Keratoconus

PURPOSE

To compare the visual outcomes of deep anterior lamellar keratoplasty (DALK) for keratoconus with and without successful big-bubble formation.

METHODS

In this retrospective comparative study, a total of 289 consecutive eyes from 257 patients underwent DALK using the big-bubble technique. In cases where the big bubble could not be accomplished, manual stromal dissection down to Descemeton membrane (DM) was performed using a crescent knife. Visual acuity and refractive outcomes were compared between the bare DM group (Group 1) and manual dissection group (Group 2).

RESULTS

A bare DM was successfully achieved in 229 (79.2%) eyes and manual dissection was performed in 60 (20.8%) eyes. The study groups were comparable in terms of age (P = 0.79), preoperative best-spectacle corrected visual acuity (BSCVA) (P = 0.15), and follow-up duration (P = 0.73). Postoperative BSCVA was significantly better in Group 1 than in Group 2 throughout follow-up (P < 0.05). In Group 2, BSCVA was significantly lower in eyes with advanced keratoconus as compared to those with moderate keratoconus (P = 0.007). At final follow-up, BSCVA ≤ 0.30 logarithm of minimum angle of resolution (logMAR) was achieved in 82.1% of eyes in Group 1 versus 54.5% of eyes in Group 2 (P < 0.001). Groups 1 and 2 were comparable in terms of postoperative spherical equivalent refractive error (P = 0.61) and keratometric astigmatism (P = 0.39).

CONCLUSION

Retention of the posterior corneal stroma which occurs with manual dissection during failed big bubble formation in DALK is associated with lower visual acuity as compared to achieving a bare DM.

Bilateral cloudy cornea: is the usual suspect congenital hereditary endothelial dystrophy or stromal dystrophy?

We provide the diagnosis, treatment and follow-up period of a patient with cloudy cornea in both eyes from birth. A 4-year-old girl presented with blurring in both eyes. Penetrating keratoplasty (PK) was performed with the preliminary diagnosis of congenital hereditary endothelial dystrophy in June 2012. According to the pathology report for extracted host tissue, the Descemet's membrane (DM) and endothelium were healthy and diagnosis was reported to be congenital hereditary stromal dystrophy. Deep anterior lamellar keratoplasty was performed on the left eye. The DM was transparent at follow-up. Cornea transplantation is the only choice to provide visual rehabilitation in children with congenital cloudy cornea. However, it is known that the prognosis of traditional PK in the paediatric age group is not good. Therefore, when using alternative keratoplasty (deep anterior lamellar keratoplasty, Descemet's stripping automated endothelial keratoplasty) options, pathological examination of the host tissue should be made.

Physical and Biological Characterization of the Gamma-Irradiated Human Cornea

PURPOSE

To compare the physical and biological characteristics of commercial gamma-irradiated corneas with those of fresh human corneas and to determine suitability for transplantation.

METHODS

The physical properties of gamma-irradiated and fresh corneas were evaluated with respect to light transmittance, hydration (swelling ratio), elastic modulus (compressive modulus by the indentation method), matrix organization (differential scanning calorimetry), and morphology (light and transmission electron microscopy). The biological properties of the gamma-irradiated cornea, including residual cell content and cellular biocompatibility, were evaluated by quantifying DNA content and measuring the proliferation rate of human corneal epithelial cells, respectively.

RESULTS

The hydration, light transmittance, elastic modulus, and proliferation rate of human corneal epithelial cells were not significantly different between fresh and gamma-irradiated corneas. However, differences were observed in tissue morphology, DNA content, and thermal properties. The density of collagen fibrils of the gamma-irradiated corneal sample (160.6 ± 33.2 fibrils/μm) was significantly lower than that of the fresh corneal sample (310.0 ± 44.7 fibrils/μm). Additionally, in the gamma-irradiated corneas, cell fragments-but not viable cells-were observed, supported by lower DNA content of the gamma-irradiated cornea (1.0 ± 0.1 μg/mg) than in fresh corneas (1.9 μg/mg). Moreover, the denaturation temperature of gamma-irradiated corneas (61.8 ± 1.1 °C) was significantly lower than that of fresh corneas (66.1 ± 1.9 °C).

CONCLUSIONS

Despite structural changes due to irradiation, the physical and biological properties of the gamma-irradiated cornea remain similar to the fresh cornea. These factors, combined with a decreased risk of rejection and longer shelf life, make the gamma-irradiated tissue a viable and clinically desired option in various ophthalmic procedures.

High Levels of 17β-Estradiol Are Associated with Increased Matrix Metalloproteinase-2 and Metalloproteinase-9 Activity in Tears of Postmenopausal Women with Dry Eye

Purpose. To determine the serum levels of sex steroids and tear matrix metalloproteinases (MMP) 2 and 9 concentrations in postmenopausal women with dry eye. Methods. Forty-four postmenopausal women with dry eye and 22 asymptomatic controls were enrolled. Blood was drawn and analyzed for serum levels of sex steroids and lipids. Then, the following tests were performed: tear collection, Ocular Surface Disease Index (OSDI) questionnaire, fluorescein tear film break-up time (TBUT), corneal fluorescein staining, Schirmer test, and conjunctival impression cytology. The conjunctival mRNA expression and tear concentrations of MMP-2 and MMP-9 were measured. Results. Serum 17β-estradiol levels were significantly higher in the dry eye subjects than in the controls (P = 0.03), whereas there were no significant differences in levels of testosterone, dehydroepiandrosterone sulfate (DHEA-S), and progesterone. Tear MMP-2 and MMP-9 concentrations (P < 0.001), as well as the MMP-9 mRNA expression in conjunctival samples (P = 0.02), were significantly higher in dry eye subjects than in controls. Serum 17β-estradiol levels were positively correlated with tear MMP-2 and MMP-9 concentrations and negatively correlated with Schirmer test values. Conclusions. High levels of 17β-estradiol are associated with increased matrix metalloproteinase-2 and metalloproteinase-9 activity in tears of postmenopausal women with dry eye.

Factors Predicting Refractive Outcomes After Deep Anterior Lamellar Keratoplasty in Keratoconus

PURPOSE

To determine the factors that predict refraction, mean keratometry, and keratometric astigmatism after deep anterior lamellar keratoplasty (DALK) in keratoconus.

DESIGN

Consecutive interventional case series.

METHODS

This study enrolled 194 consecutive eyes of 181 patients with keratoconus who underwent DALK using the big-bubble technique. Indications for surgery included contact lens intolerance or poor corrected visual acuity. Univariate analyses and analysis of covariance were used to investigate recipient-, surgical-, and postoperative-related variables capable of predicting refractive outcomes, including mean keratometry, keratometric astigmatism, and spherical equivalent refraction.

RESULTS

The mean patient age was 27.9 ± 8.2 years, and the patients were followed for 35.9 ± 18.2 months postoperatively. Preoperative mean keratometry (P = .007), time interval from surgery to running suture removal (P = .01), and suture-tract vascularization (P = .04) significantly influenced postoperative mean keratometry. Vitreous length predicted postoperative spherical equivalent (P = .03). Postoperative keratometric astigmatism failed to demonstrate any significant correlation with the preoperative, surgical, and postoperative variables. Postoperative refractive outcomes did not change relative to patient age and sex, central and peripheral corneal thickness, recipient trephination size, surgical technique (big-bubble vs manual dissection DALK), duration of steroid administration, and elevated intraocular pressure.

CONCLUSION

Keratoconus patients with an elongated posterior segment and/or steep corneas should be informed of the need for postoperative optical correction after DALK. Running suture removal should be postponed for as long as possible if there is no suture-related complication.

Modified deep anterior lamellar keratoplasty for the treatment of advanced keratoconus with steep corneal curvature to help in eliminating the wrinkles in the Descemet's membrane

Aims:

To determine the clinical efficacy of modified deep anterior lamellar keratoplasty (DALK) for the treatment of advanced-stage keratoconus with steep curvature.

Materials and Methods:

In this interventional, non-comparative case series, 30 patients with advanced stages of keratoconus and curvature of more than 60 D underwent a modified DALK procedure. In this technique, after big-bubble formation, posterior stromal lamella was cut and removed 5 mm centrally (baring Descemet's membrane completely) with posterior stromal layer remaining peripherally.

Results:

The study included 30 eyes (30 patients with a mean ± SD age of 25 ± 5.4 years). The follow-up examination was performed for all participants up to 12 months after the surgery. The mean uncorrected visual acuity (UCVA) increased from 20/800 before the surgery to a subsequent 3/10 (P =0.12). Likewise, best spectacle corrected visual acuity (BSCVA) improved, reaching 6/10 postoperatively (former quantity 20/200) (P =0.18). In addition, mean keratometry and keratometric astigmatism managed to achieve considerable improvement, from 58.8 ± 5.4 D to 46.5 ± 2.1 D and 7.8 ± 2.1 to 4.54 ± 1.54 D, respectively (P =0.52). Descemet's membrane wrinkling was not seen in any patient postoperatively.

Conclusions:

This technique is effective in restoring acceptable vision and corneal regularity in advanced cases of keratoconus with a curvature more than 60 D who are also at risk of Descemet's membrane wrinkling after DALK. Therefore, this procedure could prevent from Descemet membrane wrinkling in such cases.

Modified big-bubble technique compared to manual dissection deep anterior lamellar keratoplasty in the treatment of keratoconus

PURPOSE

To evaluate the clinical findings and results of manual dissection deep anterior lamellar keratoplasty (DALK) compared to a modified big-bubble DALK technique in eyes affected by keratoconus.

METHODS

Sixty eyes of 60 patients with keratoconus were treated with one of the two surgical techniques manual DALK (n = 30); big-bubble DALK (n = 30). The main outcomes measured were visual acuity, corneal topographic parameters, thickness of residual stroma and endothelial cell density (ECD). Patients were examined postoperatively at 1 month, 6 months, 1 year and 1 month after suture removal.

RESULTS

Final best spectacle-corrected visual acuity (BSCVA) measured 1 month after suture removal was 0.11 ± 0.08 LogMAR in the big-bubble group compared to 0.13 ± 0.08 in the manual DALK group (p = 0.227). In patients treated with the big-bubble technique without complications (Descemet's membrane completely bared), the stromal residue was not measureable. Mean stromal residual thickness in the manual DALK group was 30.50 ± 27.60 μm. Data analysis of the manual DALK group demonstrated a significant correlation between BSCVA and residual stromal thickness; lower residual stromal thickness correlated with better BSCVA values (Spearman ρ = 0.509, p = 0.018). Postoperative ECD was similar in both groups at all intervals, with no statistically significant differences. In both groups, ECD loss was only significant during the 1- to 6-month interval (p = 0.001 and p < 0.001 in the big-bubble DALK and manual DALK groups, respectively).

CONCLUSION

Manual DALK provides comparable results to big-bubble DALK. Big-bubble DALK permits faster visual recovery and is a surgical technique, which can be easily converted to manual DALK in cases of unsuccessful 'big-bubble' formation.

Corneal Regeneration by Deep Anterior Lamellar Keratoplasty (DALK) Using Decellularized Corneal Matrix

The purpose of this study is to demonstrate the feasibility of DALK using a decellularized corneal matrix obtained by HHP methodology. Porcine corneas were hydrostatically pressurized at 980 MPa at 10°C for 10 minutes to destroy the cells, followed by washing with EGM-2 medium to remove the cell debris. The HHP-treated corneas were stained with H-E to assess the efficacy of decellularization. The decellularized corneal matrix of 300 μm thickness and 6.0 mm diameter was transplanted onto a 6.0 mm diameter keratectomy wound. The time course of regeneration on the decellularized corneal matrix was evaluated by haze grading score, fluorescein staining, and immunohistochemistry. H-E staining revealed that no cell nuclei were observed in the decellularized corneal matrix. The decellularized corneal matrices were opaque immediately after transplantation, but became completely transparent after 4 months. Fluorescein staining revealed that initial migration of epithelial cells over the grafts was slow, taking 3 months to completely cover the implant. Histological sections revealed that the implanted decellularized corneal matrix was completely integrated with the receptive rabbit cornea, and keratocytes infiltrated into the decellularized corneal matrix 6 months after transplantation. No inflammatory cells such as macrophages, or neovascularization, were observed during the implantation period. The decellularized corneal matrix improved corneal transparency, and remodelled the graft after being transplanted, demonstrating that the matrix obtained by HHP was a useful graft for corneal tissue regeneration.

Long-term clinical outcomes of deep anterior lamellar keratoplasty in patients with keratoconus

PURPOSE

To report long-term clinical outcomes of deep anterior lamellar keratoplasty (DALK) in patients with keratoconus.

DESIGN

Retrospective noncomparative interventional study.

METHODS

setting: Single center. patients: Total of 158 eyes/150 consecutive patients with keratoconus with postoperative follow-up time equal to or greater than 4 years. intervention: DALK. main outcome measure(s): Uncorrected and corrected distance visual acuity (UDVA, CDVA), mean refractive spherical equivalent (MRSE), keratometry, endothelial cell density (ECD).

RESULTS

Mean postoperative follow-up was 76.9 ± 23.2 (range 48-120) months. Preoperative UDVA was 20/400 (1.5 ± 0.4 logMAR), CDVA 20/50 (0.7 ± 0.2 logMAR), MRSE -11.1 ± 5.6 diopters (D), mean keratometry 60.7 ± 6.1 D, topographic astigmatism 4.7 ± 2.6 D. At last postoperative follow-up visit, UDVA improved to 20/50 (0.5 ± 0.3 logMAR), CDVA to 20/25 (0.09 ± 0.1 logMAR), MRSE to -2.6 ± 3.5 D, mean keratometry to 44.4 ± 2.2 D, and topographic astigmatism to 2.9 ± 1.3 D. Postoperative ECD did not vary from preoperative values being 2070.5 ± 367.5 cell/mm(2) and 2198 ± 373 cell/mm(2), respectively, with 70% of eyes (111/158) showing ECD ≥2000 cells/mm(2). Eighteen eyes (11.3 %) developed stromal or epithelial rejection, 3 (1.8%) required regrafting. Eyes with successful big bubble showed greater CDVA than those that required manual dissection at follow-up equal to or less than 5 years but comparable results in the longer term.

CONCLUSIONS

DALK provides stable long-term visual and refractive outcomes. Risk of graft rejection, postoperative complication, and late ECD decay is reduced when compared to standard penetrating keratoplasty.

Efficacy and safety of deep anterior lamellar keratoplasty vs. penetrating keratoplasty for keratoconus: a meta-analysis

Purpose

To evaluate difference in therapeutic outcomes between deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PKP) for the clinical treatment of keratoconus.

Methods

A comprehensive search was conducted in Pubmed, EMBASE, Cochrane Library, and Web of science. Eligible studies should include at least one of the following factors: best corrected visual acuity (BCVA), postoperative spherical equivalent (SE), postoperative astigmatism and endothelial cell count (ECC), central corneal thickness (CCT), graft rejection and graft failure, of which BCVA, graft rejection and graft failure were used as the primary outcome measures, and postoperative SE, astigmatism, CCT and ECC as the secondary outcome measures. Given the lack of randomized clinical trials (RCTs), cohort studies and prospective studies were considered eligible.

Results

Sixteen clinical trials involving 6625 eyes were included in this review, including 1185 eyes in DALK group, and 5440 eyes in PKP group. The outcomes were analyzed using Cochrane Review Manager (RevMan) version 5.0 software. The postoperative BCVA in DALK group was significantly better than that in PKP group (OR = 0.48; 95%CI 0.39 to 0.60; p<0.001). There were fewer cases of graft rejection in DALK group than those in PKP group (OR = 0.28; 95%CI 0.15 to 0.50; p<0.001). Nevertheless the rate of graft failure was similar between DALK and PKP groups (OR = 1.05; 95%CI 0.81 to 1.36; p = 0.73). There were no significant differences in the secondary outcomes of SE (p = 0.70), astigmatism (p = 0.14) and CCT (p = 0.58) between DALK and PKP groups. And ECC in DALK group was significantly higher than PKP group (p<0.001). The postoperative complications, high intraocular pressure (high-IOP) and cataract were analyzed, fewer cases of complications occurred in DALK group than those in PKP group (high-IOP, OR 0.22, 95% CI 0.11–0.44, P<0.001) (cataract, OR 0.22; 95% CI 0.08–0.61, P = 0.004). And no cases of expulsive hemorrhage and endophthalmitis were reported.

Conclusion

The visual outcomes for DALK were not equivalent to PKP. The rate of graft failure was similar between DALK and PKP. Fewer postoperative complications occurred in DALK group, indicating that compared with PKP, DALK has lower efficacy but higher safety.

Current review and a simplified "five-point management algorithm" for keratoconus

Keratoconus is a slowly progressive, noninflammatory ectatic corneal disease characterized by changes in corneal collagen structure and organization. Though the etiology remains unknown, novel techniques are continuously emerging for the diagnosis and management of the disease. Demographical parameters are known to affect the rate of progression of the disease. Common methods of vision correction for keratoconus range from spectacles and rigid gas-permeable contact lenses to other specialized lenses such as piggyback, Rose-K or Boston scleral lenses. Corneal collagen cross-linking is effective in stabilizing the progression of the disease. Intra-corneal ring segments can improve vision by flattening the cornea in patients with mild to moderate keratoconus. Topography-guided custom ablation treatment betters the quality of vision by correcting the refractive error and improving the contact lens fit. In advanced keratoconus with corneal scarring, lamellar or full thickness penetrating keratoplasty will be the treatment of choice. With such a wide spectrum of alternatives available, it is necessary to choose the best possible treatment option for each patient. Based on a brief review of the literature and our own studies we have designed a five-point management algorithm for the treatment of keratoconus.

Serum-induced differentiation of human meibomian gland epithelial cells

PURPOSE

We hypothesize that culturing immortalized human meibomian gland epithelial cells in serum-containing medium will induce their differentiation. The purpose of this investigation was to begin to test our hypothesis, and explore the impact of serum on gene expression and lipid accumulation in human meibomian gland epithelial cells.

METHODS

Immortalized and primary human meibomian gland epithelial cells were cultured in the presence or absence of serum. Cells were evaluated for lysosome and lipid accumulation, polar and neutral lipid profiles, and gene expression.

RESULTS

Our results support our hypothesis that serum stimulates the differentiation of human meibomian gland epithelial cells. This serum-induced effect is associated with a significant increase in the expression of genes linked to cell differentiation, epithelium development, the endoplasmic reticulum, Golgi apparatus, vesicles, and lysosomes, and a significant decrease in gene activity related to the cell cycle, mitochondria, ribosomes, and translation. These cellular responses are accompanied by an accumulation of lipids within lysosomes, as well as alterations in the fatty acid content of polar and nonpolar lipids. Of particular importance, our results show that the molecular and biochemical changes of immortalized human meibomian gland epithelial cells during differentiation are analogous to those of primary cells.

CONCLUSIONS

Overall, our findings indicate that immortalized human meibomian gland epithelial cells may serve as an ideal preclinical model to identify factors that control cellular differentiation in the meibomian gland.

New perspectives on lamellar keratoplasty

Lamellar (anterior and posterior) keratoplasty entails the surgical replacement of diseased-only corneal tissue, while healthy host corneal tissue is preserved. Selective keratoplasty offers several advantages in comparison to penetrating keratoplasty such as a lower rate of graft rejection, less endothelial cell loss, faster/superior visual rehabilitation and enhanced resistance to closed injury. The surgical approach of "partial corneal transplantation" may be divided into anterior and posterior: techniques including superficial and deep anterior lamellar keratoplasty (SALK and DALK, respectively) and endothelial keratoplasty as well as Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK). These novel surgical procedures are rapidly becoming the preferred therapy option for specific corneal dysfunctions involving the corneal stroma (SALK, DALK), or corneal endothelium (DSAEK, DMEK). During the past decade, the continuing advancement of surgical techniques and the development of innovative surgical instruments have significantly enhanced corneal transplantation. Lamellar keratoplasty techniques facilitate corneal surgery, provide patients with superior outcomes and can successfully restore vision in corneal-related blindness. Nevertheless, more long-term evidence is needed to better evaluate these promising new techniques.

Corneal blindness and xenotransplantation

Approximately 39 million people are blind worldwide, with an estimated 285 million visually impaired. The developing world shoulders 90% of the world's blindness, with 80% of causative diseases being preventable or treatable. Blindness has a major detrimental impact on the patient, community, and healthcare spending. Corneal diseases are significant causes of blindness, affecting at least 4 million people worldwide. The prevalence of corneal disease varies between parts of the world. Trachoma, for instance, is the second leading cause of blindness in Africa, after cataracts, but is rarely found today in developed nations. When preventive strategies have failed, corneal transplantation is the most effective treatment for advanced corneal disease. The major surgical techniques for corneal transplantation include penetrating keratoplasty (PK), anterior lamellar keratoplasty, and endothelial keratoplasty (EK). Indications for corneal transplantation vary between countries, with Fuchs' dystrophy being the leading indication in the USA and keratoconus in Australia. With the exception of the USA, where EK will soon overtake PK as the most common surgical procedure, PK is the overwhelming procedure of choice. Success using corneal grafts in developing nations, such as Nepal, demonstrates the feasibility of corneal transplantation on a global scale. The number of suitable corneas from deceased human donors that becomes available will never be sufficient, and so research into various alternatives, for example stem cells, amniotic membrane transplantation, synthetic and biosynthetic corneas, and xenotransplantation, is progressing. While each of these has potential, we suggest that xenotransplantation holds the greatest potential for a corneal replacement. With the increasing availability of genetically engineered pigs, pig corneas may alleviate the global shortage of corneas in the near future.

Long-term comparison of full-bed deep anterior lamellar keratoplasty and penetrating keratoplasty in treating keratoconus

OBJECTIVE

To compare postoperative outcomes of full-bed deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in treating keratoconus.

METHODS

Seventy-five eyes of 64 patients who received full-bed DALK and 52 eyes of 51 patients who received PK between June 2000 and August 2010 were included in this retrospective study. Full-bed DALK was performed using Yao's hooking-detaching technique. PK was performed using a standard technique. Intraoperative and postoperative complications, visual acuity, rejection, graft survival, endothelial cell density, corneal sensation recovery, and re-innervation were compared between the two groups.

RESULTS

A best correct visual acuity of 0.5 or better was achieved in 90.7% of eyes after full-bed DALK and in 92.3% of eyes after PK (P=0.75). By the fifth postoperative year, graft endothelial cell loss reached 34.6% in the PK group vs. 13.9% in the full-bed DALK group (P<0.001). There were no statistical differences in corneal sensitivity recovery or corneal re-innervation between the groups (P>0.05). Intraoperative microperforation occurred in seven out of 75 (9.3%) eyes with a temporally postoperative double anterior chamber in two eyes in the full-bed DALK group. Postoperative complications in the PK vs. the full-bed DALK groups respectively were: rejection (7.7% vs. 0%, P=0.015), high intraocular pressure (IOP) (46.2% vs. 1.3%, P<0.001), secondary glaucoma (9.6% vs. 0%, P=0.006), complicated cataract (19.2% vs. 0%, P<0.001), and wound dehiscence (9.6% vs. 0%, P=0.006).

CONCLUSIONS

Both full-bed DALK and PK can offer long-term satisfactory visual outcomes for keratoconus. Graft rejection, secondary glaucoma, complicated cataracts, and constant endothelial cell loss were observed in eyes only after PK.

Structural and biomechanical effects of photooxidative collagen cross-linking with photosensitizer riboflavin and 370 nm UVA light on human corneoscleral tissues

This study quantitatively investigated the immediate effects of a photooxidative collagen cross-linking treatment with photosensitizer riboflavin (RF) and 370 nm UVA light in in vitro human corneoscleral collagen fibrils using histology, thickness, scanning electron microscopy, and atomic force microscopy analyses. Twenty 8 x 2 mm corneoscleral strips were dissected sagittally from donor tissue using a scalpel. Four parameters were investigated, including the density, thickness, adhesion force, and stiffness of corneoscleral tissues before and after the collagen cross-linking treatment. The RFUVA-catalyzed collagen cross-linking treatment led to an increase in the density of both corneal (8%) and scleral (23%) stromal collagens. However, there was no difference in corneoscleral thickness. Furthermore, RFUVA-catalyzed collagen cross-linking treatment led to an increased biomechanical response of corneosclera: 25 and 8% increases in corneoscleral stiffness, and 24 and 22% increases in corneoscleral adhesion force. The collagen cross-linking treatment through RF-sensitized photoreaction may cause structural and biomechanical changes in the collagen fibril network of the cornea and the sclera. This is due to narrowing of the interfibrillar spacing and the stromal edema.

In Vitro Antimicrobial Long-Term Evaluation of Corneal Preservation Media Against Microorganisms Using A Closed-Chamber Study Model

PURPOSE

To evaluate the existence of in vitro long-term antimicrobial activity of Optisol-GS against microorganisms related to corneal infection using a closed-chamber study model.

METHODS

Optisol-GS was contaminated with microorganisms related to corneal infections, and different times after contamination was analyzed using a closed-chamber study model. Microbial growths were analyzed by macroscopic observation.

RESULTS

For Staphylococcus aureus and Pseudomonas aeruginosa, bacterial growth was observed in samples taken 1 hour through 7 days and 14 days after contamination occurred. For Staphylococcus epidermidis, Streptococcus agalactiae, and Candida albicans, microbial growth was observed in all samples studied. For Streptococcus pneumoniae, bacterial growth was observed in samples taken 1 hour through 72 hours after contamination. For Streptococcus pyogenes, bacterial growth was observed in samples taken 1 hour through 7 days after contamination. For Escherichia coli, bacterial growth was observed in samples taken 1 hour through 48 hours after contamination occurred.

CONCLUSIONS

We conclude that no in vitro antimicrobial effect for any microorganism analyzed was observed in contaminated Optisol-GS after 72 hours; however, effective antimicrobial activity was observed for S. aureus, Str. pneumoniae, Str. pyogenes, P. aeruginosa, and E. coli after 7 to 10 days.

Transcription, translation, and function of lubricin, a boundary lubricant, at the ocular surface

IMPORTANCE

Lubricin may be an important barrier to the development of corneal and conjunctival epitheliopathies that may occur in dry eye disease and contact lens wear.

OBJECTIVE

To test the hypotheses that lubricin (ie, proteoglycan 4 [PRG4 ]), a boundary lubricant, is produced by ocular surface epithelia and acts to protect the cornea and conjunctiva against significant shear forces generated during an eyelid blink and that lubricin deficiency increases shear stress on the ocular surface and promotes corneal damage.

DESIGN, SETTING, AND PARTICIPANTS

Human, porcine, and mouse tissues and cells were processed for molecular biological, immunohistochemical, and tribological studies, and wild-type and PRG4 knockout mice were evaluated for corneal damage.

RESULTS

Our findings demonstrate that lubricin is transcribed and translated by corneal and conjunctival epithelial cells. Lubricin messenger RNA is also present in lacrimal and meibomian glands, as well as in a number of other tissues. Absence of lubricin in PRG4 knockout mice is associated with a significant increase in corneal fluorescein staining. Our studies also show that lubricin functions as an effective friction-lowering boundary lubricant at the human cornea-eyelid interface. This effect is specific and cannot be duplicated by the use of hyaluronate or bovine serum albumin solutions.

CONCLUSIONS AND RELEVANCE

Our results show that lubricin is transcribed, translated, and expressed by ocular surface epithelia. Moreover, our findings demonstrate that lubricin presence significantly reduces friction between the cornea and conjunctiva and that lubricin deficiency may play a role in promoting corneal damage.

Histopathological changes after deep anterior lamellar keratoplasty using the 'big-bubble technique'

PURPOSE

During deep anterior lamellar keratoplasty (DALK), endothelium and Descemet's membrane are separated from the corneal stroma by intrastromal air injection ('big-bubble technique'). The aim of our study is to analyse histopathological changes in host corneal tissue caused by air insufflation in patients with keratoconus, their variability in 10 patients and their possible clinical implication.

METHODS

The excised anterior corneal lamellae of 10 patients with keratoconus having undergone DALK using the 'big-bubble technique' were analysed by light and transmission electron microscopy as well as immunohistochemistry. In addition, intrastromal air accumulations were quantified morphometrically.

RESULTS

Intrastromal air was detected in all examined excised lamellae (8% of stromal volume), but with large variability (SD 8.8). It was detected preferentially in the inner layer of the corneal stroma and represented there up to 39% of the stromal volume. In addition, the air was predominantly located at one periphery of the excised lamellae. Intrastromal air bubbles were larger in the inner than in the superficial stromal layer and characterized by round shape and a CD68-negative collagenous 'pseudocapsule'. We detected no air-injection-induced alterations in Bowman's layer and epithelium.

CONCLUSION

Our results show that 'big-bubble DALK' causes significant intrastromal air accumulations in the cornea. Pathologists should be conscious of this phenomenon and the high topographic variability. Intrastromal air in the recipient rim may be accompanied by a decrease in mechanical stability and could contribute to postoperative suture loosening.

Spontaneous resolution of double anterior chamber with perforation of Descemet's membrane in deep anterior lamellar keratoplasty

Deep anterior lamellar keratoplasty (DALK) using Dr. Anwar's big bubble technique was performed for a patient with granular dystrophy. Intraoperatively, a perforation of the Descemet's membrane (DM) was noted inferonasally. Though the surgery was completed, the donor graft appeared to have an intact endothelium, which was inadvertently left behind by the surgeon. Intraoperatively, there was a perforation of inferonasal DM and surgery was completed by inadvertently placing a donor with an intact endothelium. Postoperatively the patient presented with a complete DM detachment and a resultant double anterior chamber (DAC). In spite of two attempts at an air tamponade on the first and fifth post operative days, the DAC still persisted. Surprisingly, during the 6^th week follow up visit, there was a complete resolution of the DAC as well as total recovery of vision. This interesting case clearly exemplifies that, in spite of failed attempts at air tamponade, a DM detachment and a DAC due to DM perforation following a DALK procedure can resolve spontaneously with good visual outcome.

Impact of eye bank lamellar tissue cutting for endothelial keratoplasty on bacterial and fungal corneoscleral donor rim cultures after corneal transplantation

PURPOSE

To determine if the lamellar cut of donor tissue for endothelial keratoplasty (EK) by an eye bank facility is associated with a change in the prevalence of positive bacterial or fungal donor rim cultures after corneal transplantation.

METHODS

A retrospective review was conducted of bacterial and fungal cultures of donor rims used for corneal transplantation at a tertiary eye care center from January 1, 2003, to December 31, 2008, with tissue provided by a single eye bank. The cases were divided into 2 groups. Group 1 ("no-cut") included keratoplasty procedures in which a lamellar cut was not performed. Group 2 ("precut") included EK procedures in which a 4-hour period of prewarming of tissue followed by a lamellar cut was performed in the eye bank before tissue delivery to the operating surgeon.

RESULTS

There were 351 donor rim cultures in group 1 and 278 in group 2. Bacterial cultures were positive in 30 donor rims (8.5%) in group 1 and 13 (4.7%) in group 2 (P = 0.058). Positive bacterial cultures were not associated with any postoperative infections. Fungal cultures were positive in 8 donor rims (2.3%) in group 1 and 7 (2.5%) in group 2 (P = 1.0). Positive fungal cultures were associated with 2 cases (13.3%) of postoperative fungal infections.

CONCLUSIONS

Corneal donor tissue can be precut for EK by trained eye bank personnel without an increased risk of bacterial or fungal contamination.

Corneal endothelium after deep anterior lamellar keratoplasty and penetrating keratoplasty for keratoconus: a four-year comparative study

PURPOSE

To compare the status of corneal endothelium and central corneal thickness within the first four postoperative years after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in patients with keratoconus.

MATERIALS AND METHODS

Thirty-nine eyes (Group A) which had PK and 44 eyes (Group B) which had DALK for the treatment of keratoconus were included in this retrospective study. The endothelial cell density (ECD), the mean endothelial cell area and the coefficient of variation of cell area were assessed with a non-contact specular microscope, and the central corneal thickness (CCT) was measured with an ultrasound pachymeter.

RESULTS

Mean ECD loss rate at two years was 36.24% in Group A and 18.12% in Group B (P<0.001). Mean ECD loss rate at four years was 47.82% in Group A and 21.62% in Group B (P<0.001). Mean annual ECD loss rate was calculated 14.12% per year in Group A and 5.78% per year in Group B. In the PK group, increase in mean CCT was 15.60% in two years and 15.03% in four years, while in the DALK group, mean CCT increased by 8.05% in two years and 9.31% in four years.

CONCLUSIONS

As the majority of ectatic disorders such as keratoconus occur in young people, long-term endothelial cell survival following treatment with keratoplasty is essential for the long-term visual ability. Our finding that corneal endothelial cell loss in the DALK group occurs at a slower rate than in the PK group suggests DALK as a safer alternative to PK in these selected patients.

Deep anterior lamellar keratoplasty for pellucid marginal degeneration

PURPOSE

To present the surgical outcomes of deep anterior lamellar keratoplasty (DALK) for pellucid marginal degeneration (PMD).

METHODS

A retrospective review was performed in 16 eyes of 16 patients who underwent DALK at the King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia between January 1, 2006 and December 30, 2009. Baring of Descemet's membrane (DM) during DALK was achieved in 8 (50%) eyes; residual stroma was left intraoperatively in the remaining 8 (50%) eyes. The big bubble technique was performed in 10 (62.5%) eyes and manual dissection was performed in the remaining 6 (37.5%) eyes. Visual acuity (LogMAR notation), intraocular pressure, intraoperative complications and postoperative graft status were assessed.

RESULTS

The mean follow up was 14.6 ± 8.2 months (range 6-35 months). The mean overall age was 31.4 ± 9.6 years (range, 19-50 years). Visual acuity increased statistically significantly from 0.9 ± 0.3 (range 0.5-1.6) preoperatively to 0.4 ± 0.2 (range 0.0-0.7) at last follow-up (p < 0.0001). There was a statistically significant improvement in postoperative sphere, cylinder, and spherical equivalent (p < 0.035, p < 0.001, and p < 0.02, respectively) compared to preoperative. Postoperative visual acuity was not statistically significantly related to gender, type of surgical technique, and baring or perforation of DM. The main graft-related complication was graft-host vascularization (2/16 eyes).

CONCLUSION

DALK reduces severe corneal astigmatism and results in good visual and refractive outcomes and is an effective alternative for patients with PMD.

Estrogen negatively regulates epithelial wound healing and protective lipid mediator circuits in the cornea

Estrogen receptors (ERs) are expressed in leukocytes and in every ocular tissue. However, sex-specific differences and the role of estradiol in ocular inflammatory-reparative responses are not well understood. We found that female mice exhibited delayed corneal epithelial wound closure and attenuated polymorphonuclear (PMN) leukocyte responses, a phenotype recapitulated by estradiol treatment both in vivo (topically in male mice) and in vitro (corneal epithelial cell wound healing). The cornea expresses 15-lipoxygenase (15-LOX) and receptors for lipoxin A(4) (LXA(4)), which have been implicated in an intrinsic lipid circuit that regulates corneal inflammation and wound healing. Delayed epithelial wound healing correlated with lower expression of 15-LOX in the regenerated epithelium of female mice. Estradiol in vitro and in vivo down-regulated epithelial 15-LOX expression and LXA(4) formation, while estradiol abrogation of epithelial wound healing was completely reversed by treatment with LXA(4). More important, ERβ and ERα selectively regulated epithelial wound healing, PMN cell recruitment, and activity of the intrinsic 15-LOX/LXA(4) circuit. Our results demonstrate for the first time a sex-specific difference in the corneal reparative response, which is mediated by ERβ and ERα selective regulation of the epithelial and PMN 15-LOX/LXA(4) circuit. These findings may provide novel insights into the etiology of sex-specific ocular inflammatory diseases.