Visualization of corneal vascularization in peripheral hypertrophic subepithelial corneal opacification with OCT angiography

Peripheral hypertrophic subepithelial corneal opacification - Role of tear secretion, medication and systemic diseases

BACKGROUND

Peripheral hypertrophic subepithelial corneal opacification (PHSCO) is a corneal disease that may severely affect vision. The major goal of this study was to test the hypothesis that tear secretion, medication and systemic diseases are associated with PHSCO.

METHODS

This is a retrospective, case-control study conducted at the Department of Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz. We analysed medical records of patients diagnosed with PHSCO. Sex, age, Schirmer's test II, general medication and medical history were assessed and compared to an age- and sex-matched control group from the Gutenberg Health Study (GHS).

RESULTS

One hundred ninety-five eyes of 112 patients with PHSCO were included. Eighty-eight patients were female with a mean age of 55.3 ± 14.7 years (23-89 years) and 24 patients were male with a mean age of 59.3 ± 12.6 years (38-84 years). In 83 patients (74.1%) both eyes were involved. The Schirmer's test II was significantly reduced in patients with PHSCO compared to the GHS control group (p < 0.001). Patients with PHSCO were more frequently administered artificial tears and steroid eye drops (p < 0.001) and were more hyperopic than healthy controls (p = 0.01). Systemic diseases or medication did not differ markedly between PHSCO and healthy controls.

CONCLUSION

Reduced tear secretion and more frequent use of artificial tears in patients with PHSCO suggest a link between PHSCO and dry eye disease. The results of the study do not support our hypothesis that PHSCO is associated with systemic diseases. Interestingly, patients with PHSCO were less frequently on β-blockers than control subjects.

Recent advances in corneal neovascularization imaging

Corneal neovascularization (CoNV) is a vision-threatening ocular disease commonly secondary to infectious, inflammatory, and traumatic etiologies. Slit lamp photography, in vivo confocal microscopy, angiography, and optical coherence tomography angiography (OCTA) are the primary diagnostic tools utilized in clinical practice to evaluate the vasculature of the ocular surface. However, there is currently a dearth of comprehensive literature that reviews the advancements in imaging technology for CoNV administration. Initially designed for retinal vascular imaging, OCTA has now been expanded to the anterior segment and has shown promising potential for imaging the conjunctiva, cornea, and iris. This expansion allows for the quantitative monitoring of the structural and functional changes associated with CoNV. In this review, we emphasize the impact of algorithm optimization in anterior segment-optical coherence tomography angiography (AS-OCTA) on the diagnostic efficacy of CoNV. Through the analysis of existing literature, animal model assessments are further reported to investigate its pathological mechanism and exhibit remarkable therapeutic interventions. In conclusion, AS-OCTA holds broad prospects and extensive potential for clinical diagnostics and research applications in CoNV.

Current clinical applications of anterior segment optical coherence tomography angiography: a review

Optical coherence tomography (OCT) is a revolutionary in vivo imaging technology that presents real-time information on ocular structures. Angiography based on OCT, known as optical coherence tomography angiography (OCTA), is a noninvasive and time-saving technique originally utilized for visualizing retinal vasculature. As devices and built-in systems have evolved, high-resolution images with depth-resolved analysis have assisted ophthalmologists in accurately localizing pathology and monitoring disease progression. With the aforementioned advantages, application of OCTA has extended from the posterior to anterior segment. This nascent adaptation showed good delineation of the vasculature in the cornea, conjunctiva, sclera, and iris. Thus, neovascularization of the avascular cornea and hyperemia or ischemic changes involving the conjunctiva, sclera, and iris has become prospective applications for AS-OCTA. Although traditional dye-based angiography is regarded as the gold standard in demonstrating vasculature in the anterior segment, AS-OCTA is expected to be a comparable but more patient-friendly alternative. In its initial stage, AS-OCTA has exhibited great potential in pathology diagnosis, therapeutic evaluation, presurgical planning, and prognosis assessments in anterior segment disorders. In this review of AS-OCTA, we aim to summarize scanning protocols, relevant parameters, and clinical applications as well as limitations and future directions. We are sanguine about its wide application in the future with the development of technology and refinement in built-in systems.

Risk factors for peripheral hypertrophic subepithelial corneal opacification

BACKGROUND

To evaluate the phenotype, tear secretion and refractive changes of patients diagnosed with peripheral hypertrophic subepithelial corneal opacification (PHSCO).

METHODS

This is a retrospective, interventional case series conducted at the Department of Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz. Medical records of patients diagnosed with PHSCO were analysed. Sex, age, fluorescein tear film breakup time (FTBUT), Schirmer Test II, iris colour and hair colour were assessed. Objective refraction was evaluated at different time points and, in case of surgery, 1 month and 1 year postoperatively.

RESULTS

One hundred ninety-five eyes of 112 patients (78.6% female, 21.4% male; mean age 56.2 ± 14.3) were included. The median FTBUT was 6 sec. (Q1: 4/Q3: 8.75; range 1-20 s) (measured in 70 eyes of 36 patients), the median Schirmer Test II was 8 mm (Q1: 5/ Q3:15; range 1-35 mm). In 83 patients (74.1%) both eyes were involved. In 86 eyes of 64 patients (55.3%) superficial keratectomy was performed. Sphere and cylinder changed significantly 1 month and 1 year postoperative compared to the pre-operative objective refraction, while there was no significant change between 1 month and 1 year postoperatively.

CONCLUSION

We found that PHSCO occurs mostly bilaterally in middle-aged women and appears to be associated with decreased tear production and reduced tear film stability.

Spatial Distribution of Mast Cells Regulates Asymmetrical Angiogenesis at the Ocular Surface

Mast cells, historically known for their function as effector cells in the induction of allergic diseases, reside in all vascularized tissues of the body, particularly, in proximity to blood and lymphatic vessels. Despite being neighboring sentinel cells to blood vessels, whether the spatial distribution of mast cells regulates the degree of angiogenesis remains to be investigated. Herein, an asymmetrical distribution of mast cells was shown at the murine ocular surface, with the higher number of mast cells distributed along the nasal limbus of the cornea compared with the temporal side. Using a well-characterized murine model of suture-induced corneal neovascularization, insult to the nasal side was shown to result in more extensive angiogenesis compared with that to the temporal side. To directly assess the impact of the spatial distribution of mast cell on angiogenesis, neovascularization was induced in mast cell-deficient mice (cKit^w-sh). Unlike the wild-type (C57BL/6) mice, cKit^w-sh mice did not show disproportionate growth of corneal blood vessels following the temporal and nasal insult. Moreover, cromolyn-mediated pharmacologic blockade of mast cells at the ocular surface attenuated the asymmetrical nasal and temporal neovascularization, suggesting that spatial distribution of mast cells significantly contributes to angiogenic response at the ocular surface.

Effects of Superficial Keratectomy in Peripheral Hypertrophic Subepithelial Corneal Opacification on Front and Back Corneal Astigmatism

PURPOSE

To evaluate changes of anterior and posterior corneal astigmatism after superficial keratectomy in peripheral hypertrophic subepithelial corneal opacification (PHSCO).

METHODS

Patients with PHSCO, who had received superficial keratectomy with mitomycin C 0.02%, were included in this retrospective study. Scheimpflug imaging of the cornea (Pentacam®, Oculus, Wetzlar, Germany), best-corrected visual acuity (BCVA) and objective refraction were determined preoperatively and 3 months after superficial keratectomy.

RESULTS

Fifteen eyes of 15 patients (age: 55 ± 16 years; range: 36-82 years) were included. The mean preoperative BCVA was logMAR 0.4 ± 0.2 and improved to logMAR 0.21 ± 0.3 (p < .01) postoperatively. The median preoperative astigmatism of the anterior corneal surface was 4.67 ± 2.4 D (range: 0.9-13.2 D) and decreased to 1.4 ± 0.4 D (range: 0.8-2.3 D) 3 months after surgery. The median astigmatism of the posterior corneal surface was 0.6 ± 0.5 D (range: 0.1-2.2 D) before surgery and decreased to 0.3 ± 0.2 D (range: 0-0.7 D) 3 months after surgery.

CONCLUSION

Superficial keratectomy reduces anterior corneal astigmatism more than posterior corneal astigmatism in patients with PHSCO. Furthermore, a myopic shift and corneal steepening in the peripheral and mid-peripheral cornea was observed after removal of the subepithelial corneal opacification spots.

New Technologies in Clinical Trials in Corneal Diseases and Limbal Stem Cell Deficiency: Review from the European Vision Institute Special Interest Focus Group Meeting

To discuss and evaluate new technologies for a better diagnosis of corneal diseases and limbal stem cell deficiency, the outcomes of a consensus process within the European Vision Institute (and of a workshop at the University of Cologne) are outlined. Various technologies are presented and analyzed for their potential clinical use also in defining new end points in clinical trials. The disease areas which are discussed comprise dry eye and ocular surface inflammation, imaging, and corneal neovascularization and corneal grafting/stem cell and cell transplantation. The unmet needs in the abovementioned disease areas are discussed, and realistically achievable new technologies for better diagnosis and use in clinical trials are outlined. To sum up, it can be said that there are several new technologies that can improve current diagnostics in the field of ophthalmology in the near future and will have impact on clinical trial end point design.

Successful Treatment of Corneal Opacification with Associated Thickened Epithelium by Simple Peeling: Acquired Corneal Subepithelial Hypertrophy (ACSH)

Purpose

To study clinical and histopathological findings of corneal opacification caused by thickened epithelium leading to reduced vision and topographical changes and to evaluate the outcome of its removal.

Methods

Twelve patients (17 eyes) with central, paracentral or peripheral corneal opacification were reviewed to obtain their visual acuity, describe their slit lamp (SL) appearance (depth, extent and density) and document their topographic changes before and after peeling of the epithelium under SL or surgical removal under the microscope. Specimens of six cases were available for histopathological examination and immunohistochemical staining.

Results

Most of the eye opacifications were secondary to corneal procedures in 10 [Penetrating keratoplasty (PKP) in 7 for congenital glaucoma, keratoconus or adherent leukoma – usually over graft-host junction –, Photorefractive keratectomy (PRK) in 2 and Phototherapeutic keratectomy in one], chronic inflammation following trachoma or non-specific causes (3), and herpetic scar (1). Three cases were considered to be idiopathic. All cases presented with decreased vision, astigmatism or changes in topography or refraction. Their vision, clinical symptoms and topography improved after treatment. Histopathologically, all six cases shared findings that are similar to what have been described as peripheral hypertrophic subepithelial corneal degeneration (PHSCD) rather than Salzmann’s nodular degeneration. None of the cases showed inflammation or subepithelial pannus formation in the excised tissue. However, our cases did not fit into the diagnosis of PHSCD because of the location of the corneal opacification (being peripheral in 41% of the corneas, the presence of underlying primary etiologic factors in 82% of the eyes and the bilateral occurrence in 5 patients.

Conclusions

Meticulous SL examination aided by corneal imaging may accurately diagnose and determine the depth of corneal opacification as a cause for reduced vision. Histopathologically, the removed tissue is similar to PHSCD, but cases differ in their clinical profile. Peeling the thickened epithelial/subepithelial tissue is curative in most patients, improves visual and clinical outcome and avoids unnecessary corneal grafting.

Quantitative analysis of conjunctival microvasculature imaged using optical coherence tomography angiography

Background

The goal was to quantitatively analyze the bulbar conjunctival microvascular density using optical coherence tomography angiography (OCTA) and compare it to the vessel density using functional slit-lamp biomicroscopy (FSLB).

Methods

Temporal bulbar conjunctiva of 20 eyes (10 healthy subjects) was imaged using both OCTA and FSLB. Image processing was performed including equalization, de-noising, thresholding, and skeletonization. The vessel density was measured by fractal analysis (box counting, Dbox) and pixel counting (%).

Results

Vessel density (Dbox) of the bulbar conjunctiva obtained using OCTA was 1.28 ± 0.01 Dbox, which was significantly lower than the result (1.32 ± 0.01 Dbox, P < 0.001) obtained using FSLB. Furthermore, the vessel density (%) obtained using OCTA was 3.31 ± 0.12%, which was also significantly lower than the result (3.69 ± 0.16%, P < 0.001) obtained using FSLB. No significant correlations (r ranged from 0.21 to 0.32, P > 0.05) between both instruments were found in both vessel density methods (Dbox and percentage). However, in each of the devices, vessel density in Dbox was significantly correlated with the vessel density in percentage (r = 1.0 for FSLB and r = 0.98 for OCTA, both P < 0.001).

Conclusion

This study demonstrated that the vessel density of the bulbar conjunctiva obtained using OCTA can be quantified, and the results were not compatible with that obtained using slit-lamp biomicroscopy photography.