A prospective study of acute corneal hydrops by in vivo confocal microscopy in a New Zealand population with keratoconus

Management of acute corneal hydrops - Current perspectives

Acute corneal hydrops (ACH) is a rare but sight-threatening complication of corneal ectasias. We aim to review the current literature on etiopathogenesis, histology, role of ancillary investigations, management, and outcomes of ACH by classifying the various management strategies based on their site of action and the underlying mechanism. A review of the literature was conducted by searching the following databases: PubMed (United States National Library of Medicine), Embase (Reed Elsevier Properties SA), Web of Science (Thomson Reuters), and Scopus (Elsevier BV) till April 2023. The literature search used various combinations of the following keywords: acute corneal hydrops, keratoconus, ectasia, management, keratoplasty. Nine hundred eighty-three articles were identified based on the above searches. Case reports which did not add any new modality of treatment to the existing literature, articles unrelated to management, those with no full text available, and foreign-language articles with no translation available were excluded. Eventually, 75 relevant articles that pertained to the management of ACH were shortlisted and reviewed. Recent studies have described newer surgical interventions like full-thickness or pre-Descemetic sutures, thermokeratoplasty, and plasma injection that aim to close the posterior stromal break. Posterior lamellar keratoplasties act by replacing the posterior torn Descemet's membrane (DM), and early deep anterior lamellar keratoplasty (DALK) has been attempted to combine the correction of the anatomical defect and visual rehabilitation in a single surgery. These surgical interventions may help by reducing the scarring and increasing the number of patients who can be visually rehabilitated with contact lenses rather than keratoplasty.

Optical coherence tomographic features of feline acute corneal hydrops: A case report

OBJECTIVE

The objective of the study was to describe the optical coherence tomographic features of a cat with acute corneal hydrops.

ANIMAL STUDIED

A 4-year-old castrated male domestic shorthaired showing conjunctival redness, ocular discharge, and intermittent squinting of both eyes with asymmetrical disease onset.

METHODS

Complete ophthalmic examination and optical coherence tomography were performed.

RESULTS

On slit-lamp biomicroscopic examination, severe intrastromal fluid pockets with profound bullae were observed in the dorsomedial region in both eyes. A diagnosis of feline acute corneal hydrops was made in both eyes. Optical coherence tomography revealed profound stromal lamellar separation representing heterogeneous reflective areas, and fluid pockets and bullae of variable size were concomitant to Descemet's membrane detachment demonstrated by a well-defined homogeneous hyporeflective area. Upon reevaluation 30 days during healing process for both eyes, the thickened epithelia and the thinning pan-stromal areas were identified as homogeneously hyper-reflective epithelia and as heterogeneous hyper-reflectivity, respectively. A thickened posterior corneal surface was shown as heterogeneous with patchy hyper-reflectivity. Additionally, Descemet's membrane detachment in the initial presentation had two distinct forms suspicious of Descemet's membrane rupture in each eye: a break with rolled ends and a break with flat ends.

CONCLUSION

To the author's knowledge, this study represents the first documentation of in vivo detection of Descemet's membrane detachment and presumed rupture in a cat experiencing acute corneal hydrops. These observations strongly indicate that Descemet's membrane detachment/rupture acts as a most likely risk factor in the onset of acute corneal hydrops in cats.

The novel role of lymphatic vessels in the pathogenesis of ocular diseases

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

Te hauora karu o te iwi Māori: A comprehensive review of Māori eye health in Aotearoa/New Zealand

This article provides a summary of available data on Māori ocular health, highlighting significant disparities between Māori and non-Māori populations. Māori are more likely to develop diabetes, sight-threatening retinopathy and keratoconus, and present for cataract surgery earlier with more advanced disease. Limited data exists for macular degeneration and glaucoma, but there is some suggestion that Māori may have lower prevalence rates. The article emphasises the urgent need for robust national data on Māori ocular health to enable targeted interventions and funding allocation. Achieving equity for Māori in all aspects of health, including ocular health, requires concerted efforts from all stakeholders.

Deep anterior lamellar keratoplasty following thermokeratoplasty assisted epikeratophkia: A novel two-stage one-graft method to treat acute corneal hydrops

Purpose

To evaluate the clinical effects of deep anterior lamellar keratoplasty (DALK) using a single graft after thermokeratoplasty assisted epikeratophakia for the treatment of acute corneal hydrops.

Methods

This novel surgical procedure was performed on seven eyes of seven patients between 2019 and 2020. The procedure combines a first-stage surgery of thermokeratoplasty assisted epikeratophkia with intracameral sterile air injection and a second-stage surgery of DALK using the same corneal graft for both procedures. Main outcome measures included pre- and postoperative corrected distance visual acuity (CDVA) and anterior segment optical coherence tomography (AS-OCT) parameters. Corneal transparency, epithelization, and the presence of neovascularization, were evaluated at the 1-year follow-up visit.

Results

Corneal edema resolved rapidly in six of the seven cases. The mean central corneal thickness was significantly reduced from baseline to 1 day, 1 week, 1 month, and 2 months after the first-stage surgery (P < 0.0001). At a mean of 2.1 ± 0.7 months after the first-stage surgery, DALK was successfully performed in all cases. Six months later, the mean central corneal thickness was 611 ± 31 μm and the mean thickness of the recipient's residual stroma bed was 20 ± 6 μm at the central corneal area. Mean LogMAR CDVA improved from 1.74 ± 0.34 at baseline to 0.20 ± 0.11 after DALK (P < 0.0001). No postoperative complications appeared in our case series during the 1-year observation period.

Conclusion

Very good visual results were obtained with a novel technique (thermokeratoplasty assisted epikeratophakia followed by DALK using the same corneal graft) in the treatment of acute corneal hydrops.

In vivo confocal microscopy of the inflamed anterior segment: A review of clinical and research applications

In vivo confocal microscopy (IVCM) allows non-invasive imaging of the living human cornea, specifically enabling the detection of immune cells in the healthy and diseased ocular anterior segment. Studies using IVCM have provided insight into the effects of contact lens wear on corneal Langerhans cell density and morphology, and the effects of eye drops on conjunctiva-associated lymphoid tissue. IVCM has also been shown to be a useful adjunctive diagnostic tool in distinguishing infective and non-infective uveitis and in diagnosing atypical infective keratitis. In the research setting, this technology has enhanced our understanding of the role of inflammatory cells in corneal neuropathy and angiogenesis. In vivo-ex vivo correlation using animal models has helped overcome some of the difficulties in identifying cell type on IVCM images. As highlighted in this review, currently there are multiple established, and emerging, clinical and research applications for IVCM in the inflamed anterior segment.

Extreme Descemet's membrane rupture with hydrops in keratoconus: Clinical and histological manifestations

Purpose

To study the clinical and histological manifestations of an extreme Descemet's membrane rupture as a result of keratoconus.

Observations

Using Periodic acid-Schiff assay to study a keratoconic cornea with an extreme rupture showed that the ruptured Descemet's membrane had retracted and folded into scrolls and ridges. The dimensions of the rupture were estimated to be 3.7mm², and the central cornea was extremely thinned with a thickness of only 260μm. Stromal scarring and loosely packed lamellae were present anterior to the scrolls and ridges. Antibodies targetting the major components of Descemet's membrane, Laminin and type IV collagen, displayed intense labelling adjacent to the scrolls where the stroma was denuded and differential expression patterns lined the ridges. Environmental scanning electron microscopy showed possible collagen deposition at the site of rupture.

Conclusions and importance

The specific staining patterns of laminin and type IV collagen suggest these components have an important role in re-endothelisation of the cornea. This is the first known report of spatial resolution of the topography of the Descemet's membrane rupture established by environmental scanning electron microscopic image montage.

Advanced anterior segment imaging in keratoconus: a review

Advances in anterior segment imaging have enhanced our ability to detect keratoconus in its early stages and characterize the pathologic changes that occur. Computerized corneal tomography has elucidated the alterations in shape of the anterior and posterior corneal surfaces and alterations in thickness as the disease progresses. Automated screening indices such as the keratoconus screening index were developed to assist in detecting keratoconus in suspicious cases. In vivo assessment of keratoconic corneas has revealed that compromised corneal biomechanics can now be measured clinically. Optical coherence tomography has demonstrated alterations in corneal epithelial thickness and distribution in keratoconus, has a role in assessing Descemet's membrane detachment in acute corneal hydrops (ACH) and the depth of the demarcation line following corneal collagen cross-linking. In vivo confocal microscopy has exhibited cellular changes that occur in keratoconus and provided insight into cellular events that may be related to the development of neovascularization in ACH.

Penetrating Keratoplasty for Keratoconus With and Without Resolved Corneal Hydrops: Long-term Results

PURPOSE

To evaluate the long-term risk of endothelial rejection, graft survival, and associated factors following penetrating keratoplasty (PK) for keratoconus, with and without prior resolved corneal hydrops.

DESIGN

Retrospective cohort study.

METHODS

Primary outcome measures were endothelial rejection-free survival and failure-free survival. Secondary outcome measures were corneal neovascularization following hydrops and complications following PK.

RESULTS

A total of 245 eyes underwent PK for keratoconus with mean follow-up of 5.6 ± 3.6 years. Eyes with prior hydrops (n = 74) had lower endothelial rejection-free survival rates compared with eyes without prior hydrops: 86.5% ± 4.0% vs 86.5% ± 2.6% at 1 year, 61.0% ± 6.2% vs 76.9% ± 3.3% at 5 years, and 45.8% ± 10.1% vs 70.9% ± 4.3% at 10 years, respectively (P = .023). Multivariate analysis identified factors associated with endothelial rejection as age ≤25 years (P = .017), corneal neovascularization (P = .001), donor trephination size >8 mm (P = .017), and poor clinic attendance (P = .015). There was no difference in the failure-free survival rates with and without prior hydrops: 98.6% ± 1.3% vs 97.1% ± 1.3% at 1 year, 97.3% ± 1.9% vs 95.1% ± 1.9% at 5 years, and 97.3% ± 1.9% vs 92.2% ± 2.7% at 10 years, respectively (P = .42). Corneal neovascularization was present at the time of PK in 44.6% of eyes with prior hydrops and 7.6% without prior hydrops (P < .001).

CONCLUSIONS

Corneal neovascularization, a frequent complication of corneal hydrops, was associated with increased risk of endothelial rejection following PK. However, allograft survival was similar in eyes with and without prior hydrops.

Contemporary Treatment Paradigms in Keratoconus

The past 20 years have witnessed an explosion in our knowledge of keratoconus, accompanied by a radical transformation of management options. A 2-hit hypothesis proposes an underlying genetic predisposition coupled with external environmental factors, including eye rubbing and atopy. The variable prevalence and natural history have been better defined including significant cone progression in middle age. Therefore, current management must include early diagnosis, regular monitoring, and treatment of environmental cofactors. Spectacles and contact lenses remain fundamental to the optical management of keratoconus. Intrastromal corneal ring segments have been increasingly used, providing improvement in the corneal shape, corrected visual acuity, and contact lens wear. However, like contact lenses, intrastromal corneal ring segments do not treat the underlying disease process. Therefore, current approaches must also consider treatments to minimize keratoconus progression. Fortunately, there is increasing evidence that corneal collagen crosslinking will halt or slow progression in most cases. Until relatively recently, penetrating keratoplasty was the preferred intervention for advanced keratoconus, with long-term success in the region of 90%; however, the greatest risk of failure remains endothelial allograft rejection. Deep anterior lamellar keratoplasty has emerged in the new millennium as a preferred approach to conserve the host endothelium and avoid rejection. Nonetheless, the overall superiority of deep anterior lamellar keratoplasty compared with penetrating keratoplasty, in terms of optical and survival benefits, is still debated. This perspective provides an overview of our current knowledge of keratoconus and current management options. A step-ladder approach to managing keratoconus is outlined to provide the practitioner with a contemporary management paradigm.

Acute corneal hydrops in keratoconus - new perspectives

PURPOSE

To summarize the current concepts and recent literature regarding the epidemiology, pathogenesis, imaging modalities, and treatment of acute hydrops in keratoconus.

DESIGN

Perspective.

METHODS

Review and synthesis of selected literature, with interpretation and perspective.

RESULTS

Acute corneal hydrops is an incompletely understood complication of keratoconus, characterized by marked corneal edema caused by a break in Descemet membrane, allowing aqueous to enter the corneal stroma and epithelium. Although usually self-limiting, with clinical signs of edema typically resolving after 3 months, it often leaves a vision-impairing scar, necessitating and expediting the need for corneal transplantation. Studies have identified risk factors for developing acute hydrops. Modern imaging modalities such as ultrasound biomicroscopy, anterior segment optical coherence tomography, and in vivo confocal microscopy have enlightened us to the microstructural changes that take place during acute hydrops, the factors that influence its duration, and sequelae. Newer treatment regimens have seen a reduction in the duration of corneal edema during acute hydrops, and have improved the survival of corneal grafts after transplantation for resolved hydrops.

CONCLUSIONS

Effective management of acute corneal hydrops in keratoconus is based on recognizing and addressing the risk factors, treating the acute event effectively and promptly to reduce the duration of edema and its complications, and, ultimately, successful corneal transplantation with acceptable long-term graft survival rates. Improved in vivo imaging of the cornea during acute hydrops has led to an enhanced understanding of the pathogenesis and ultrastructural changes of the condition, and in turn has resulted in improved management of the disease.