Proposed new classification scheme for chemical injury to the human eye

Amniotic membrane transplantation for acute ocular burns

BACKGROUND

Ocular surface burns can be caused by chemicals (alkalis and acids) or direct heat. One effect of the burn is damage to the limbal epithelial stem cells of the ocular surface with delayed re-epithelialisation, stem cell failure, and conjunctivalisation of the cornea. Amniotic membrane transplantation (AMT) performed in the acute phase (day 0 to day 7) following an ocular surface burn is claimed to reduce pain and accelerate healing. The surgery involves securing a layer of amniotic membrane (AM) to the eyelid margins as a patch to cover the entire ocular surface. However, there is debate about the severity of an ocular burn that may benefit from AMT and uncertainty of whether AMT improves outcomes.

OBJECTIVES

To compare the effect of AMT with medical therapy in the first seven days after an ocular surface burn, compared to medical therapy alone.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; which contains the Cochrane Eyes and Vision Trials Register; 2021, Issue 9); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov and the WHO ICTRP. We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 29 September 2021.

SELECTION CRITERIA

We included randomised trials that compared an AMT applied in the first seven days following an ocular surface burn in addition to medical therapy with medical therapy alone. The outcome measures were failure of re-epithelialisation by day 21 post injury, visual acuity at final follow-up, corneal neovascularisation, symblepharon, time to re-epithelialisation and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, assessed the included studies for risk of bias and extracted relevant data. We contacted trial investigators for missing information. We summarised data using risk ratios (RRs) and mean differences (MDs) as appropriate.

MAIN RESULTS

We analysed two RCTs, but excluded individual patients who had been treated outside the acute phase in one of the studies (data provided by study authors). In total, 36 moderate burns from one RCT and 92 severe burns from two RCTs were evaluated separately. For both categories, the certainty of the evidence was downgraded principally as a result of high risks of performance and detection biases, and because of imprecision indicated by very wide confidence intervals. In addition, follow-up was insufficiently frequent to calculate time-to-epithelialisation precisely. Moderate severity ocular burns (Roper-Hall classification II-III) The relative risk of AMT on failure of epithelialisation by day 21 was 0.18 (0.02 to 1.31), and LogMAR visual acuity was 0.32 lower (0.55 to 0.09 lower) in the treatment group (i.e. better), suggesting a possible benefit of AMT. The GRADE assessment for failure of epithelialisation by day 21 was downgraded to very low due to the risk of bias and imprecision (very wide confidence intervals including no effect). The GRADE assessment for visual acuity at final follow-up was downgraded to low due to the risk of bias and imprecision (optimal information size not met). The relative effects of AMT on corneal neovascularisation (RR 0.56; 0.21 to 1.48), symblepharon (RR 0.41; 0.02 to 9.48) and time-to-epithelialisation (13 days lower; 26.30 lower to 0.30 higher) suggest possible benefit of AMT, but the wide confidence intervals indicate that both harm and benefit are possible. GRADE assessments for these outcomes were once again downgraded to very low due to the risk of bias and imprecision. Since adverse effects are rare, the small sample would have fewer occurrences of rare but potentially important adverse effects. The GRADE assessment for adverse effects was therefore considered to be low.  Severe ocular burns (Roper-Hall classification IV) The relative risk of AMT on failure of epithelialisation by day 21 was 1.03 (0.94 to 1.12), and LogMAR visual acuity was 0.01 higher (0.29 lower to 0.31 higher) in the treatment group (i.e, worse), indicating no benefit of AMT. GRADE assessments for failure of epithelialisation by day 21 and final outcomes were downgraded to low. The relative effects of AMT on corneal neovascularisation (RR 0.84; 0.66 to 1.06), symblepharon (RR 0.89; 0.56 to 1.42) and time-to-epithelialisation (1.66 days lower; 11.09 lower to 7.77 higher) may include both benefit and harm. GRADE assessments for corneal neovascularisation, symblepharon and time-to-epithelialisation were downgraded to low due to risk of bias and imprecision. For adverse effects, the GRADE assessment was downgraded to low, reflecting the small sample sizes in the RCTs.

AUTHORS' CONCLUSIONS

There is uncertain evidence to support the treatment of moderate acute ocular surface burns with AMT in addition to standard medical therapy as a means of preventing failure of epithelialisation by day 21, improving visual outcome and reducing corneal neovascularisation, symblepharon formation and time-to-epithelialisation. For severe burns, the available evidence does not indicate any significant benefit of treatment with AMT.

Advances and Current Clinical Applications of Anterior Segment Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is the most relevant evolution based on optical coherence tomography (OCT). OCTA can present ocular vasculature, show detailed morphology for assessment, and quantify vessel parameters without intravenous dye agent. Research on the anterior segment OCTA (AS-OCTA) is only in its initial phase, and its advances in clinical diagnosis and treatment efficacy evaluations require a detailed comparison to traditional imaging methods. In this review of AS-OCTA, we summarize its technical features, imaging advances, current clinical applications in various eye diseases, as well as its limitations and potential future directions. AS-OCTA offers potential advantages in ophthalmic imaging, and with further development it could become a common tool in the near future.

Consensus Nomenclature for Reporting Neovascular Age-Related Macular Degeneration Data: Consensus on Neovascular Age-Related Macular Degeneration Nomenclature Study Group

PURPOSE

To establish a process to evaluate and standardize a state-of-the-art nomenclature for reporting neovascular age-related macular degeneration (AMD) data.

DESIGN

Consensus meeting.

PARTICIPANTS

An international panel of retina specialists, imaging and image reading center experts, and ocular pathologists.

METHODS

During several meetings organized under the auspices of the Macula Society, an international study group discussed and codified a set nomenclature framework for classifying the subtypes of neovascular AMD and associated lesion components.

MAIN OUTCOME MEASURES

A consensus classification of neovascular AMD.

RESULTS

The study group created a standardized working definition of AMD. The components of neovascular AMD were defined and subclassified. Disease consequences of macular neovascularization were delineated.

CONCLUSIONS

The framework of a consensus nomenclature system, a definition of AMD, and a delineation of the subtypes of neovascular AMD were developed. Establishing a uniform set of definitions will facilitate comparison of diverse patient groups and different studies. The framework presented is modified and updated readily, processes that are anticipated to occur on a periodic basis. The study group suggests that the consensus standards outlined in this article be used in future reported studies of neovascular AMD and clinical practice.

Anterior Segment Optical Coherence Tomographic Angiography Assessment of Acute Chemical Injury

PURPOSE

To compare routine clinical examination with optical coherence tomography angiography (OCTA) for the assessment of limbal conjunctival ischemia following a chemical burn.

SETTING

Validity analysis.

METHODS

We assessed 10 participants (15 eyes) with an acute chemical injury. Clinical photographs were used to determine the extent of any limbal conjunctival epithelial defect and ischemia. These were compared with the extent of limbal ischemia identified on OCTA images of the ocular surface. Quantitative and longitudinal analysis using the OCTA software were also performed. Correlations with visual outcome were sought using clinical and OCTA-derived variables.

RESULTS

The extent of clinically determined limbal ischemia was less than that identified with OCTA (2.3±3.6 clock hours vs 5.1±4.2 clock hours, P = .003), which in turn was less than the size of limbal conjunctival epithelial defect (7.3±5.1 clock hours, P = .03). Longitudinal OCTA analysis showed that mean vessel area increased by 0.2%±0.1% during the study, corresponding to a rate of vascular recovery of 0.9 mm²/d. Significant correlations were found between visual outcome at 3 months and limbal conjunctival fluorescein staining (r = 0.67, P = .006), and limbal conjunctival ischemia on OCTA (r = 0.76, P = .001).

CONCLUSIONS

OCTA can objectively identify and monitor the recovery of limbal ischemia following an acute ocular chemical injury. OCTA confirms that limbal ischemia is usually more extensive than is suggested by clinical examination, and the former is highly correlated with visual outcome. OCTA therefore is a useful tool in the management of ocular chemical injury.

Absence of Therapeutic Benefit of the Anti-Inflammatory Protein TSG-6 for Corneal Alkali Injury in a Rat Model

Purpose: To investigate the therapeutic efficacy of tumor necrosis factor (TNF)-α stimulated gene/protein 6 (TSG-6) in a rat model of corneal alkali injury. Methods: Corneal alkali injury was produced by placing an NaOH-soaked filter paper disk on the central cornea of the right eye of an anesthetized male Lewis (LEW/Crl) rat. Recombinant human TSG-6, or an equal volume of phosphate-buffered saline (PBS), was administered intravenously (IV), by anterior chamber (AC) injection, or as a topical drop. The affected eyes were photographed daily using a dissecting microscope and documented for clinical time course analysis of corneal opacification. Corneal tissue was excised at pre-determined therapeutic endpoints, with subsequent qRT-PCR or histological analyses. Results: The continuous monitoring of corneal alkali injury progression revealed TSG-6 treatments do not show sufficient effectiveness in vivo regardless of IV injection, AC injection, or topical application. Corneal opacification and neovascularization were not diminished, and gene expression was not impacted by these treatments. However, both IV and AC administration of TSG-6 significantly suppressed pro-inflammatory cytokines compared to PBS-treated eyes. Conclusion: We conclude that the therapeutic potential of TSG-6 is insufficient in a rat corneal alkali injury model.

Acute Chemical Eye Injury and Limbal Stem Cell Deficiency-A Prospective Study in the United Kingdom

PURPOSE

To analyze the incidence, nature, outcomes, and complications of acute chemical eye injuries, including the incidence of limbal stem cell deficiency (LSCD) and to compare the 2 main classifications for ocular chemical injuries: Roper-Hall (RH) and Dua.

METHODS

This is a prospective, consecutive, interventional single-center study between April and October 2009 of all new patients with acute chemical eye injury presenting to the Royal Victoria Infirmary eye emergency department (EED).

RESULTS

Of 11,683 patients who attended the EED, 98 patients (110 eyes) presented with acute chemical eye injury (60% male). This represents an estimated annual incidence of 5.6 new cases per 100,000 population. Mean age was 36.5 years (1-78; SD 17.1 years), including 7 children (age <10 years). Fifty-one patients (52%) had work-related injuries. The most common chemical agent was alkali (78%). All 4 RH grade IV cases were unilateral, assault with ammonia, and required early amniotic membrane transplantation as per the protocol, but despite full treatment, they developed total LSCD in the affected eye.

CONCLUSIONS

Acute chemical eye injuries are rare. Male patients in the working age group are more prone to work-related chemical injuries, whereas young children tend to have domestic injuries. Grade I, II, and III RH and Dua chemical injuries had a very good prognosis with topical treatment only, whereas RH grade IV (Dua grade IV-VI), mainly assaults with ammonia, progressed to total/severe LSCD despite appropriate management including early amniotic membrane transplantation. The Dua classification includes conjunctival involvement, having a greater value in predicting the final clinical outcome when grading chemical eye injuries.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

Mesenchymal stem cells improve healing of the cornea after alkali injury

PURPOSE

To evaluate the efficacy of mesenchymal stem cells (MSCs) to ameliorate the consequences of corneal alkali injuries.

METHODS

Corneal alkali injuries were created in 30 rabbit eyes. The MSC group (n = 15) were treated with intrastromal and subconjunctival injections of phosphate-buffered saline (PBS) containing 2 × 10(6) MSCs and topical application. The control group (n = 15) was treated with PBS by the same applications forms. Drops of standard treatment (ascorbate 10 %, citrate 10 %, tobramycin, dexamethasone, Cyclogyl) were instilled for 2 weeks. Rabbits underwent slit-lamp examination, fluorescein staining, photography, and were evaluated for corneal neovascularization, opacification, and epithelial defects. Tear secretion and IOP were also evaluated. Furthermore, the concentration of Serumglutamic-pyruvic transaminase (SGPT) and vascular endothelial factor (VEGF) were measured. Immunohistochemistry was also performed for a-SMA and Ki-67.

RESULTS

Eyes treated with MSCs showed better recovery. The mean neovascularized area was significantly smaller in the MSC group (p < 0.05). A significant difference in the degree of corneal opacification and re-epithelialization was also observed, as well as the IOP at 21 and 28 posttraumatic days (p < 0.05). Histology showed that MSCs resulted in almost normal architecture of eye tissues. After the MSCs infusion, SGPT and VEGF levels in cornea were significantly reduced. Immunohistochemistry demonstrated a reduction of a-SMA in the MSC group with higher mitotic-regenerative activity with the presence of Ki67.

CONCLUSIONS

Our study represents a first step in understanding the possibilities of the MSC approach to treatment of alkali injuries of the cornea and shows that such an approach improves clinical outcomes and leads to better prognosis.

Survey of ocular irritation predictive capacity using Chorioallantoic Membrane Vascular Assay (CAMVA) and Bovine Corneal Opacity and Permeability (BCOP) test historical data for 319 personal care products over fourteen years

The Chorioallantoic Membrane Vascular Assay (CAMVA) and Bovine Corneal Opacity and Permeability (BCOP) test are widely used to predict ocular irritation potential for consumer-use products. These in vitro assays do not require live animals, produce reliable predictive data for defined applicability domains compared to the Draize rabbit eye test, and are rapid and inexpensive. Data from 304 CAMVA and/or BCOP studies (319 formulations) were surveyed to determine the feasibility of predicting ocular irritation potential for various formulations. Hair shampoos, skin cleansers, and ethanol-based hair styling sprays were repeatedly predicted to be ocular irritants (accuracy rate=0.90-1.00), with skin cleanser and hair shampoo irritation largely dependent on surfactant species and concentration. Conversely, skin lotions/moisturizers and hair styling gels/lotions were repeatedly predicted to be non-irritants (accuracy rate=0.92 and 0.82, respectively). For hair shampoos, ethanol-based hair stylers, skin cleansers, and skin lotions/moisturizers, future ocular irritation testing (i.e., CAMVA/BCOP) can be nearly eliminated if new formulations are systematically compared to those previously tested using a defined decision tree. For other tested product categories, new formulations should continue to be evaluated in CAMVA/BCOP for ocular irritation potential because either the historical data exhibit significant variability (hair conditioners and mousses) or the historical sample size is too small to permit definitive conclusions (deodorants, make-up removers, massage oils, facial masks, body sprays, and other hair styling products). All decision tree conclusions should be made within a conservative weight-of-evidence context, considering the reported limitations of the BCOP test for alcohols, ketones, and solids.

Advances in corneal stem-cell transplantation in rabbits with severe ocular alkali burns

PURPOSE

To evaluate the efficacy of autologous corneal epithelial sheet implantation in restoring transparency of rabbit corneas severely injured by alkaline and the effect of photocoagulation in arresting corneal neovessel ingrowth.

SETTING

Ophthalmology Department, School of Biomedical Sciences, Universidad Austral, Buenos Aires, Argentina.

METHODS

Limbal stem-cell deficiency (LSCD) was induced in 14 rabbits by alkali burns. A limbal cell biopsy was done in the contralateral eye, and the cells were cultured on a fibroblast feeder layer grown on autologous clotted platelet-poor plasma or commercial fibrin for 21 days. Anterior keratectomy was followed by suturing corneal cell sheets over the stroma. If regrowth of vessels occurred, argon laser photocoagulation was applied to them. Rabbits were killed at 30, 60, 90, 180, and 360 days and the corneas processed for histopathology and inmunohistochemistry.

RESULTS

A small (2.5 mm(2)) limbal biopsy achieved stem-cell replication in vitro. Corneal clarity and epithelial defects evolved with a trend toward improvement. There was a significant reduction in corneal neovascularization. Histology showed a multilayered stratified epithelium including several epithelial-like cells with clear cytoplasm in the deepest part. There were no signs of intraepithelial mucin cells on the implanted corneas. Immunohistochemical results showed expression of cytokeratins 3 and 12 in the central corneal epithelium and an absence of cytokeratin 19.

CONCLUSIONS

Autologous limbal epithelial cell transplantation improved the corneal surface in eyes with LSCD. Photocoagulation of neovessel ingrowth was effective over the 1-year follow-up. Results may facilitate the application of this technique in patients.