Prevalence and associated factors of corneal opacity among adults in Kolladiba town, Northwest Ethiopia: a cross-sectional study

OBJECTIVE

This study aimed to assess the prevalence and associated factors of corneal opacity among adults in Kolladiba town, Northwest Ethiopia.

METHODS AND ANALYSIS

A community-based cross-sectional study was conducted using a systematic random sampling technique. A total of 846 adult individuals were recruited for the study. Ethical approval was obtained from the University of Gondar School of Medicine Ethical Review Committee. A standardised, semistructured questionnaire plus an ocular examination were used to collect the data. The data were entered into Epi Info V.7 and cleaned and analysed using SPSS V.26. Binary and multivariable logistic regression analyses were performed to select candidate variables and identify statistically significant factors. Variables with a p value of less than 0.05 according to the multivariable logistic regression analysis were considered to be statistically significant.

RESULTS AND CONCLUSION

The prevalence of corneal opacity among the study participants was 27.2% (95% CI 24.4% to 30.4%). In this study, age 49-60 years (adjusted OR (AOR): 1.90; 95% CI 1.03 to 3.32), age ≥61 years (AOR=2.12; 95% CI 1.17 to 3.87), inability to read and write (AOR=2.65; 95% CI 1.68 to 4.16), middle-income level (AOR=2.12; 95% CI 1.30 to 3.47) and poor income level (AOR=4.96; 95% CI 3.04 to 8.09) were factors that were significantly associated with corneal opacity.In this study, the prevalence of corneal opacity was considerably high. Being poor and unable to read and write were the primary factors significantly associated with corneal opacity. Hence, concerned stakeholders should strive to reverse the effects of corneal opacity on the quality of life of the study and causal studies should be considered in the future.

Performance outcomes from a DMEK peeling and preparation wet lab

OBJECTIVE

To evaluate the Descemet membrane endothelial keratoplasty (DMEK) preparation performance of trainee surgeons in an ex vivo human donor cornea DMEK wet lab simulation setting.

METHODS

Human donor corneoscleral rims unsuitable for transplantation were obtained from Moorfields Lions Eye Bank. At the wet lab, graft stripping was performed by scoring the peripheral endothelium. The trypan blue positive cells (TBPC) and cell density (cells/mm2-reticule count) were counted manually before and after stripping. The procedural time, peripheral and central tears and complete peel-off were also recorded and analysed.

RESULTS

Eight trainee surgeons attended the wet lab each attempting three DMEKs. Between the first and last attempts a significant decrease was seen in the procedural time (17.6 min vs 10.6 min (p<0.05)) and the TBPC % (12.9% vs 3.8% (p<0.05)). The percentage of tears peripherally and centrally also reduced between the first and the last trials (50% vs 13% (p=0.2226) and 38% vs 0% (p=0.1327)). A significant correlation was found between longer peeling times and higher TBPC % (p<0.001) with a 0.7% endothelial mortality increase for each additional minute required to complete the peel.

CONCLUSIONS

DMEK wet labs provide a controlled risk-free learning opportunity for trainee surgeons to improve confidence and competence. Wet labs improve the success rate of DMEK graft preparation as well as flatten the learning curve. This emphasises the importance of continued support for the expansion of this valuable learning resource, promoting wider uptake of DMEK surgery.

Extending the utility of anterior corneal buttons through refrigeration and glycerol cryopreservation: utility rate and outcome analysis

BACKGROUND/AIMS

To evaluate the utility rate, indication, outcome, and cost of refrigeration and glycerol cryopreservation for storing anterior corneal buttons during endothelial keratoplasty for subsequent use in tectonic lamellar patch grafting.

METHOD

Anterior corneal buttons collected after precutting or prestripping during endothelial keratoplasty from January 2014 to December 2019 were preserved using the following protocol: (1) refrigeration for up to 4 weeks at 4°C in Optisol-GS and (2) glycerol cryopreservation for up to 2 years. The utility rate, outcome and cost of these cryopreserved anterior corneal buttons were retrospectively examined.

RESULTS

During the 6-year study period, 26 anterior corneal buttons were refrigerated and 49 were cryopreserved for extended use. The utility rates for the refrigerated and cryopreserved anterior corneal buttons were 69.2% and 73.5%, respectively. Their average preservation periods were 0.53±0.05 and 12.76±0.94 months, respectively. Noninfection-related perforation was the leading indication for using the extendedly preserved anterior corneal buttons. The average postoperative follow-up periods were 10.03±2.91 and 14.35±2.17 months for refrigerated and cryopreserved anterior corneal buttons. Secondary keratoplasty was required by 7 of 18 (38.9%) and 6 of 36 (16.7%) patients receiving refrigerated and cryopreserved anterior corneal buttons, respectively. None of our patients developed graft infection from donor tissues.

CONCLUSION

Cryopreservation can safely extend the utility of anterior corneal buttons. This method not only reduced the wastage of the limited donor tissue but also was cost-effective.

A new storage medium containing amphotericin B versus Optisol-GS for preservation of human donor corneas

BACKGROUND/AIM

We compared the quality of human donor corneas stored in a cold storage medium containing 2.5 μg/ml of amphotericin B (Kerasave, AL.CHI.MI.A. S.R.L., Ponte San Nicolò, Italy) and Optisol-GS (Bausch & Lomb Inc., Bridgewater, NJ, USA) for 14 days.

METHODS

Sixteen pairs of human donor corneas were collected in Eusol-C (AL.CHI.MI.A. S.R.L., Ponte San Nicolò, Italy). Next, all tissues underwent the first evaluation that included the assessments of central corneal thickness (CCT), endothelial cell density (ECD) measured using both trypan blue staining and specular microscopy, endothelial cell (EC) mortality and morphology, and corneal transparency within 24 hours from recovery (Day 1). Afterwards, one cornea of each pair was transferred into Kerasave or Optisol-GS. ECD and CCT were also assessed at Day 7, and all the metrics were evaluated again at the end of the storage period (Day 14).

RESULTS

At all tested time points, no differences were found in the qualitative (corneal transparency, EC morphology) and quantitative metrics (ECD, CCT, EC mortality) between the Kerasave and the Optisol-GS storage groups. At Day 14, the corneas stored in Kerasave and Optisol-GS showed ECD of 2312±98 and 2335±128 cells/mm² (p=0.886), CCT of 717±17 and 697±19 μm (p=0.454) and central EC mortality of 0.54%±0.40% and 0.14%±0.14% (p=0.719), respectively.

CONCLUSIONS

The new amphotericin B-containing medium Kerasave was comparable to Optisol-GS in terms of preservation of corneal characteristics at 2-8°C for 14 days.

Fifteen-year incidence rate and risk factors of pterygium in the Southern Indian state of Andhra Pradesh

PURPOSE

To report 15-year incidence rate and associated risk factors of pterygium among people aged 30 years and above at baseline in the rural clusters of longitudinal Andhra Pradesh Eye Disease Study (APEDS III).

METHODS

The baseline APEDS I included 7771 participants of which 6447 (83%) were traced and 5395 (83.7%) were re-examined in APEDS III. To estimate the incidence of pterygium, we selected participants who were 30 years and above at baseline (4188), of which 2976 were traced and 2627 (88.3%) were examined, and based on inclusion criteria, 2290 participants were included in the study. The incidence rate of pterygium was defined as the proportion of people free of pterygium at baseline who had developed the condition at 15-year follow-up (range 13-17 years). Univariate and multivariable analyses for risk factors were undertaken.

RESULTS

The sex-adjusted incidence rate of pterygium was 25.2 per 100 person-years (95% CI 24.8 to 25.7) which was significantly higher for men than women (26.3 per 100 person-years (95% CI 25.6 to 27.0) and 24.7 (95% CI 24.1 to 25.3) respectively). At the multivariable analysis, male gender (RR: 1.35, 95% CI 1.0 to 1.83), no formal education (RR: 2.46, 95% CI 1.22 to 4.93), outdoor occupation (RR: 1.47, 95% CI 1.14 to 1.9) and lower body mass index (BMI) (<18.5) (RR: 1.25, 95% CI 1.02 to 1.55) were associated with increased risk of pterygium.

CONCLUSIONS

The overall incidence rate of pterygium was high in this rural population, especially in men and those engaged in outdoor activities, lack of formal education and with lower BMI. It is likely that greater exposure to ultraviolet light is a major contributing factor, thus warranting preventive strategies.

Long-term clinical outcomes of keratoplasty using gamma-irradiated corneal lenticules

Objective

To report long-term clinical outcomes of gamma-irradiated corneal lenticules in partial and full-thickness keratoplasty.

Methods and Analysis

This multicentre, retrospective case series includes 23 patients who underwent surgery at three centres (India, Guatemala, and USA) between May 2009 and March 2018. The main outcome measures were epithelialization and retention for therapeutic keratoplasty and best spectacle-corrected visual acuity (BSCVA) for optical keratoplasty.

Results

Patients were categorised according to primary aetiology requiring corneal transplantation: non-inflammatory conditions, infectious keratitis and sterile keratolysis. Nine patients with non-inflammatory conditions underwent anterior lamellar keratoplasty (n=7) and Boston type 1 keratoprosthesis (n=2). All nine grafts remained intact and epithelialized during follow-up (median 24 months). In the seven patients who underwent anterior keratoplasty, the graft stayed optically clear during follow-up (median 12 months), with BSCVA between 20/20 and 20/40 in all but one patient who developed cataract. Nine patients with severe infectious keratitis had emergency patch grafting. Six of those grafts epithelialized and remained intact over a median of 30 months, providing tectonic support until optical keratoplasty with fresh tissue could be performed. Three grafts had recurrent infectious keratitis 1–3 months postoperatively, two of which underwent tectonic keratoplasty with fresh tissue which also eventually became infected during follow-up. In five additional patients with sterile keratolysis who underwent lamellar patch graft, two grafts remained intact during follow-up (median 36 months). Two patients had recurrent corneal melt within 1 month, and both had subsequent corneal surgery with fresh tissue which also failed. There were no donor-related complications.

Conclusion

Gamma-irradiated sterile corneal stromal lenticules can be considered as a viable alternative to fresh tissue in various clinical settings.

Very early endothelial cell loss after penetrating keratoplasty with organ-cultured corneas

AIMS

After keratoplasty, postoperative endothelial cell loss is calculated between the eye bank endothelial cell density (ebECD) and the postoperative specular microscopy (SM). To elucidate the very early cell loss, always described after penetrating keratoplasty (PK), we designed two complementary studies.

METHODS

(1) Clinical prospective study of 90 consecutive PKs (keratoconus, Fuchs' corneal dystrophy, lattice dystrophy, bullous keratopathy) with organ-cultured corneas and postoperative follow-up by SM at day 5 (D5), D15, month 1 (M1) and M3. This series provided a quantification of the difference between ebECD performed 2 days before graft and very early postoperative ECD. (2) Ten pairs of corneas with comparable ebECD in both corneas and same organ-culture (OC) duration were randomised: one cornea was grafted, and, at the same time, the viable ECD (vECD) of the other was measured after labelling with Hoechst/ethidium/calcein-AM. The relationship between vECD and very early postoperative ECD was studied.

RESULTS

vECD at the time of graft did not differ from ECD 5 days after PK, with a difference of 39 (-356; 355) cells/mm² (median (10°; 90° percentile, p=0.799)), whereas a significant difference of 755 (359; 1146) cells/mm², corresponding to 28% (95% CI 26 to 30) of cells, was measured between ebECD and ECD 5 days after PK (p<0.001).

CONCLUSIONS

In OC, ebECD provided to surgeons significantly overestimate the number of viable ECs grafted to patients. The absence of difference between the vECD at D0 and ECD at D5 indicates that the very early endothelial cell loss is almost negligible in recipients.

Organ culture storage of pre-prepared corneal donor material for Descemet's membrane endothelial keratoplasty

PURPOSE

To evaluate the effect of media composition and storage method on pre-prepared Descemet's membrane endothelial keratoplasty (DMEK) grafts.

METHODS

50 corneas were used. Endothelial wound healing and proliferation in different media were assessed using a standard injury model. DMEK grafts were stored using three methods: peeling with free scroll storage; partial peeling with storage on the stroma and fluid bubble separation with storage on the stroma. Endothelial cell (EC) phenotype and the extent of endothelial overgrowth were examined. Global cell viability was assessed for storage methods that maintained a normal cell phenotype.

RESULTS

1 mm wounds healed within 4 days. Enhanced media did not increase EC proliferation but may have increased EC migration into the wounded area. Grafts that had been trephined showed evidence of EC overgrowth, whereas preservation of a physical barrier in the bubble group prevented this. In grafts stored in enhanced media or reapposed to the stroma after trephination, endothelial migration occurred sooner and cells underwent endothelial-mesenchymal transformation. Ongoing cell loss, with new patterns of cell death, was observed after returning grafts to storage. Grafts stored as free scrolls retained more viable ECs than grafts prepared with the fluid bubble method (74.2± 3% vs 60.3±6%, p=0.04 (n=8).

CONCLUSION

Free scroll storage is superior to liquid bubble and partial peeling techniques. Free scrolls only showed overgrowth of ECs after 4 days in organ culture, indicating a viable time window for the clinical use of pre-prepared DMEK donor material using this method. Methods for tissue preparation and storage media developed for whole corneas should not be used in pre-prepared DMEK grafts without prior evaluation.

In vitro study of air bubble dynamics following pneumodissection of donor corneas and relationship of air bubble pattern with a peripheral paracentesis incision

AIMS

To study various types of morphological patterns of the air bubble and their relation to a peripheral paracentesis after air injection in corneal stroma in vitro experiment.

METHODS

Air was injected into the donor corneas from the endothelial side and pattern was noted. Four different scenarios were created, namely (a) air injection into the deep stroma (n=11), (b) air injection into the superficial stroma (n=3), (c) air injection into the deep stroma after making a peripheral incision internal to the trabecular meshwork region that simulated an anteriorly placed paracentesis incision, with the site of air injection within a clock hour of the peripheral incision (n=7) and (d) air injection into the deep stroma after making a peripheral incision, the site of air injection being 180° away from the peripheral incision site (n=3).

RESULTS

Air injection at deep posterior stroma resulted in the formation of type-1 and type-2 bubbles, type 2 began from the periphery and followed the type-1 bubble pattern in majority of the donor corneas. The type-1 pattern was noted as a bubble in the central part of the donor disc that did not reach the peripheral extent of the cornea. The type-2 pattern was a bubble that started at the peripheral cornea and expanded but was limited by the limbus circumferentially. With a full-thickness peripheral incision and air injection in the same clock hour of the incision, only a type-1 bubble pattern was noted with air leakage from the site of the incision.

CONCLUSIONS

The results of the study corroborate with the clinical observations made during deep lamellar keratoplasty (DLK). The placement of the paracentesis has a bearing on the pattern of the air bubble and can be used to an advantage during DLK surgery.

Global cell-by-cell evaluation of endothelial viability after two methods of graft preparation in Descemet membrane endothelial keratoplasty

Purpose

To describe a novel method of global cell viability assessment for Descemet membrane endothelial keratoplasty (DMEK) and the comparison of two contemporary methods of donor tissue preparation.

Methods

DMEK transplants were prepared using two different methods: liquid bubble separation and manual peeling (n=8 each group). Samples were incubated with Hoechst, calcein-AM and ethidium homodimer prior to mounting on a curved imaging chamber. Z-stacked fluorescence microscopy images were combined to produce an in-focus global image capable of resolving all cell nuclei. Image processing software was used to define a calcein-positive live cell area, count all cell nuclei within this area and subtract ethidium-positive dead cells to derive the total viable endothelial cell count. Corrected global cell density was calculated by dividing the number of viable cells by the graft area, which had been corrected for imaging a curved surface.

Results

Corrected global cell density was lower than the central endothelial cell density in both groups: 85.5% of the pre-preparation central endothelial cell density in the peel group and 75.8% in the bubble group. Corrected global cell density was significantly lower in the liquid bubble separation group than in the peel group (p=0.04).

Conclusions

Eye bank estimations of central endothelial cell density overestimate true cell density after graft preparation in DMEK. A peel method is less damaging and more consistent than a liquid bubble method. Cell loss correlated strongly with the degree of stromal hydration prior to bubble separation in the liquid bubble group.

The impact of donor age and endothelial cell density on graft survival following penetrating keratoplasty

PURPOSE

To determine if donor age and preoperative endothelial cell density (ECD) affect corneal endothelial failure following penetrating keratoplasty (PK).

METHODS

Preoperative and postoperative data for PKs performed in the UK between April 1999 and March 2012 were analysed. Donor age was split into three groups (0-60, 61-75 and >75 years) and donor ECD was split into three groups (≤2400, 2401-2600 and >2600 cells/mm²). Cox proportional hazards regression was used to determine whether the selected subgroups of donor age and donor ECD have an impact on endothelial failure and a systematic analysis of the interaction between donor ECD and donor age was conducted. The analysis was stratified for primary corneal diagnosis (Fuchs endothelial dystrophy (FED), pseudophakic bullous keratopathy (PBK) and other) and corrected for potentially confounding factors (human leukocyte antigen matching, donor trephine diameter, deep vascularisation, the occurrence of reversible rejection episodes and receipt of systemic antiviral medication, long-term steroids or other immunosuppressive agents).

RESULTS

A total of 9415 patients, from the National Health Service Blood and Transplant UK Transplant Registry, who received their first PK for visual reasons were included in this study. The overall 5-year graft survival rate due to endothelial failure was 89%. Survival rates in recipients with FED, PBK and 'all other indications' were 95%, 83% and 89%, respectively. Our analysis shows that donor ECD did not affect outcome following corneal graft within the preselected categories, irrespective of diagnosis and after allowing for any potential confounding factors. Furthermore, HRs for each level of donor ECD, relative to >2600 cells/mm², for each combination of age group and indication, were not statistically significant.

CONCLUSIONS

We were unable to detect a significant effect of donor age, up to 90 years, and preoperative donor ECD, above the lower limit of 2200 cells/mm², on endothelial failure at 5 years following PK.

Long-term preservation of donor corneas in glycerol for keratoplasty: exploring new protocols

AIM

To evaluate the role of temperature and adjunctive dehydration in better long-term preservation of human corneas when preserved and stored in glycerol.

METHODS

Different preservation temperatures and effects of adding silica gel in glycerol-preserved corneal tissues were evaluated. Human corneal tissues not suitable for optical keratoplasty initially preserved in McCarey-Kaufman medium were transferred to glycerol and stored at four different temperatures for 3 months as follows: tissues in anhydrous glycerol with and without silica gel at -80°C, -20°C, 4°C and at room temperature (RT). Parameters evaluated included microbial sterility, thickness (Digimatic micrometer), transparency (slit lamp examination, UV-Vis spectrophotometer), mechanical strength (Instron 5848 Microtester), tissue integrity (H&E staining), antigenicity (immunohistochemistry) and ultrastructure of collagen (transmission electron microscopy, TEM).

RESULTS

Microbial test after 3 months of glycerol preservation confirmed sterility of the tissues. The thickness increased in corneas preserved at RT with and without silica gel (p<0.001). RT corneas had the lowest transparency and tensile strength. Tissues in anhydrous glycerol stored with and without silica gel at -80°C were the most transparent (p<0.001) and had the highest tensile strength (p<0.001). Tissue integrity was maintained and expression of Human Leukocyte Antigen D related (HLA-DR) was less in glycerol-preserved corneas at -80°C. TEM studies indicated that parallel alignment of stromal collagen was disrupted at RT-preserved corneas.

CONCLUSIONS

Corneal tissue preserved at -80°C was the best method for preservation as it maintained the sterility, thickness, optical transparency, mechanical strength and ultrastructural features.

Surrogate scleral rim with fibrin glue: a novel technique to expand the pool of donor tissues for Descemet stripping automated endothelial keratoplasty

Descemet stripping automated endothelial keratoplasty is being performed in increasing number of cases each year. An adequate scleral rim on all sides is mandatory for the donor cornea to be mounted on the artificial anterior chamber for microkeratome-assisted dissection. Occasionally, the scleral rim may however be inadequate. The primary cause of inadequate scleral rim is poorly trained technicians in in-situ excision technique. Hence, we devised a novel technique for performing successful microkeratome-assisted dissection in donor corneas with inadequate scleral rim. A surrogate scleral rim was obtained from the donor tissue not fit for optical keratoplasty. It was then glued to the optical grade donor cornea that had an inadequate scleral rim either focally or circumferentially. The combination was then used for a successful microkeratome-assisted dissection followed by endothelial keratoplasty.

Topical 0.03% tacrolimus preventing rejection in high-risk corneal transplantation: a cohort study

BACKGROUND/AIMS

The present study aims to identify the rate of rejection and safety of 0.03% tacrolimus eye drops associated with 1% prednisolone in a topical formulation, comparing them with the use of 1% prednisolone eye drops alone in patients with high-risk corneal transplantation.

METHODS

Retrospective cohort study with 72 patients (72 eyes) who underwent more than one penetrating keratoplasty (PK) in the same eye or had severe chemical burn between 2004 and 2011 in the department of cornea and external disease of the Clinical Hospital of Porto Alegre, Brazil. We compared the records of 36 patients that performed unilateral PK and received only 1% prednisolone eye drops between May 2004 and July 2008, with 36 patients that received 0.03% tacrolimus eye drops in addition to 1% prednisolone between August 2008 and August 2011.

RESULTS

The mean follow-up of the group exposed to tacrolimus was 23.1 months and 24.0 in the prednisolone alone group. The demographics, intraoperative and initial indications for first PK were similar between groups, as well as the number of regrafts performed. Intraocular pressure (IOP) was not statistically different among groups. Regarding irreversible rejections, topical tacrolimus showed greater protection: only seven grafts (19.4%) lost transparency against 16 (44.4%) in the 1% prednisolone alone group (p <0.05).

CONCLUSIONS

Topical 0.03% tacrolimus was effective in preventing irreversible rejection in patients with high-risk corneal transplantation without increasing IOP.