Role of Ultrasound Biomicroscopy in Diagnosis and Treatment of Terrien Disease

Progression and topographic subtypes of Terrien marginal degeneration

PURPOSE

To report long-term outcomes and to search for immunological and genetic risk factors in Terrien marginal degeneration (TMD).

METHODS

Retrospective, in part prospective, hospital-based longitudinal follow-up study of 32 eyes of 16 Finnish patients from 2012 to 2023. Median follow-up was 7.3 years (range, 0.3-15.2). Symptoms, best corrected visual acuity, pattern in axial power map, astigmatism, corneal thickness, higher order irregularity, cavities, progression and human leukocyte antigen genes were analysed. In 13 blood samples, 483 corneal and inflammatory disease-related genes were analysed with exome sequencing.

RESULTS

The median age at first examination was 61 years (range, 13-89). Eleven (69%) patients were male, and 13 (81%) had bilateral disease. The median annual rate of progression of topographic astigmatism and new thinning was 0.03 D (range, -1.50 to 3.60) and 12.9 μm (range, -107.8 to 93.0), respectively; 0.15 D (range -1.50 to 1.17) and 21.6 μm (range, 1.3-93.0) in 6 (38%) patients with fast progression, and 0.02 D (range, -0.06 to 3.60) and 4.1 μm (range, -107.8 to 24.7) in 10 (72%) patients with slow progression. Topographic pattern, unilaterality, cavities, sectoral hyperaemia, poor response to medical treatment and new thinning after surgery were associated with fast progression. Thickness at maximal thinning fell below 450 μm only with fast progression. Five eyes changed the topographic pattern. Coexisting keratitis fugax hereditaria was found in one patient.

CONCLUSIONS

A subtype of TMD progresses faster. The most sensitive indicators of progression were thinning and topographic astigmatism. No shared genetic cause for TMD was identified.

Diagnostic Criteria for Terrien Marginal Degeneration: Nordic Terrien Degeneration Study

PURPOSE

To refine the diagnostic criteria for Terrien marginal degeneration (TMD) based on experience in 3 Nordic countries.

METHODS

This is a retrospective, multicenter, hospital-based cross-sectional study of 49 eyes of 29 white patients in tertiary referral centers in Finland, Sweden, and Denmark from 1998 to January 2018. The median follow-up was 3 years. Symptoms, best corrected visual acuity, astigmatism, corneal thickness, curvature and cavities, stage, and progression were analyzed.

RESULTS

TMD was diagnosed equally likely between 15 and 86 years of age (median, 47 years). Twenty patients (69%) had bilateral disease, and 62% were men. Seventeen patients (59%) had symptoms including blurred vision and ocular surface disease symptoms without inflammatory signs. Eight patients (28%) had slightly reduced corneal sensitivity. Median best corrected visual acuity was 20/25 (range, 20/16-20/200) and astigmatism was 2.6 diopters (D) (range, 0-10) with a mean progression of 0.41 D per year (range, 0-5.4). Age and astigmatism were not correlated. All eyes had peripheral vascularization, lipid deposits, and hyperreflectivity throughout thinned peripheral stroma and its anterior edge. The thinning progressed in 15 patients (52%). Of 26 patients, 8 (31%) had single or confluent paralimbal intrastromal cavities, most commonly superiorly. By Süveges classification, the stage was 2 (92%) or 3 (8%). Minimum corneal thickness and corneal curvature were loosely associated, leading to different stages in Wang classification in 34 eyes (69%).

CONCLUSIONS

TMD is defined by peripheral corneal thinning, superficial neovascularization, lipid deposition at the leading edge, absence of ulceration and inflammation, and frequently cavitation. The most sensitive way to follow its progression is anterior segment optical coherence tomography.

Macular Corneal Dystrophy and Posterior Corneal Abnormalities

PURPOSE

This study reports the presentation of 2 families with macular corneal dystrophy (MCD). The aim of this study was to show whether ultrasound biomicroscopy (UBM) can, based on posterior changes of the cornea in MCD, assist in the choice of surgery, either anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK), compared with optical coherence tomography (OCT) and Scheimpflug.

METHODS

Six patients with MCD were examined for their best-corrected visual acuity, slit-lamp, OCT, UBM, and Scheimpflug findings. Blood samples for DNA and exons of the CHST6 gene were screened for mutations.

RESULTS

All 6 patients showed typical MCD signs at the slit lamp. Corneal transplantation was required in 2 patients in both eyes. Recurrence of MCD was observed in 2 eyes after the DALK procedure (patient A5, age 48 years, right eye and B1, 51 years, left eye), whereas the 2 eyes after PK (patient A5, age 48 years, left eye and patient B1, 51 years, right eye) remained clear (for 10 years of follow-up in patient A5 and 4 years in patient B1). In 2 patients (A1 and A3), corneal thinning could be evaluated by OCT. In 3 patients (A2, 3, and 4), UBM disclosed deeper pathologies including opacities, loss of continuity, and focal protrusions of the posterior cornea, which were not evident by other devices. In family A, a novel mutation was identified.

CONCLUSIONS

Our UBM examination of MCD shows alterations of the cornea's posterior layer and confirms the known clinical and histological findings of MCD that PK represents the therapy of choice, contrary to DALK. The novel CHST6 mutation shows the heterogeneity of MCD.

Corneal Nerve and Epithelial Cell Alterations in Corneal Allodynia: An In Vivo Confocal Microscopy Case Series

PURPOSE

To investigate morphological changes of the corneal epithelium and subbasal nerves in patients with corneal allodynia using in vivo confocal microscopy (IVCM).

DESIGN

Case-control study of patients with corneal allodynia and healthy controls.

METHODS

Ten eyes of six patients were diagnosed with corneal allodynia at a single center and compared to fifteen healthy eyes. IVCM of the central cornea was performed on all subjects and controls. Images were retrospectively analyzed numbers of total corneal subbasal nerves, main trunks and branches, total nerve length and density, nerve branching, and tortuosity, superficial and basal epithelial cell densities, and superficial epithelial cell size.

RESULTS

Corneal allodynia was seen in patients with dry eye disease, recurrent corneal erosion syndrome, exposure to ultraviolet radiation, and Accutane use. Compared to controls, patients with corneal allodynia had a significant decrease in the total numbers of subbasal nerves (P=.014), nerve branches (P=.006), total nerve length (P=.0029), total nerve density (P=.0029) and superficial and basal epithelial cell densities (P=.0004, P=.0036) with an increase in superficial epithelial cell size (P=.016). There were no statistically significant differences in the number of subbasal nerve main trunks (P=.09), nerve branching (P=.21), and nerve tortuosity (P=.05).

CONCLUSIONS

Corneal IVCM enables near-histological visualization and quantification of the cellular and neural changes in corneal allodynia. Regardless of etiology, corneal allodynia is associated with decreased corneal epithelial cell densities, increased epithelial cell size, and decreased numbers and lengths of subbasal nerves despite an unremarkable slit-lamp examination. Therefore, IVCM may be useful in the management of patients with corneal allodynia.

Terrien's marginal degeneration accompanied by latticed stromal opacities

Purpose

We report a case of Terrien’s marginal degeneration (TMD) with a unilaterally typical narrow band of peripheral corneal stroma thinning, accompanied by the presence of an unusual network of opacities diffusing throughout the anterior stroma layers.

Case Report

A 43-year-old woman presented with superior nasal peripheral corneal thinning and an unusual network of polygonal stromal opacities in the anterior corneal stroma of the right eye. Latticed corneal changes were unusually extensive and distributed diffusely in the stroma. No abnormalities were found in the corneal epithelium and in the basal epithelial cells. No noticeable changes were found in the left eye. Because of a progressively worse ocular irritation of the right eye, a diagnosis of TMD was made for this patient.

Conclusions

This case of TMD accompanied by keratopathy was unusual. The branching stromal lattice pattern of the corneal opacities was difficult to distinguish from lattice corneal dystrophy. In this case, the polygonal stromal opacities were located in the anterior corneal stroma and therefore were distinguished from a similar manifestation in posterior crocodile shagreen.

Laser scanning in vivo confocal microscopy in a case of Terrien marginal degeneration

PURPOSE

To describe corneal microstructural modifications in an early case of Terrien marginal degeneration by means of laser scanning in vivo corneal confocal microscopy.

METHODS

A 20-year-old man affected by Terrien marginal degeneration in his right eye was examined with the Heidelberg Retina Tomograph 2 with a Rostock Cornea Module. The patient presented a corneal lesion with marked superior thinning and no clinical signs of inflammation. The left eye showed no clinical signs of degeneration.

RESULTS

The right eye showed irregular Bowman's membrane, amorphous-appearing substance co-localizing with lipid exudation, and needle-like hyperreflective material in the affected peripheral corneal region. Abnormally scarce and branched sub-basal plexus nerves as well as numerous activated keratocytes, sometimes organized in hyperreflective nests, were observed in the central cornea of the same eye. Although the left eye was clinically unaffected, activated keratocytes were detected in its anterior central stroma.

CONCLUSIONS

In vivo confocal microscopy supports the hypothesis of a mild inflammatory state with an atypical sub-basal nerve pattern in a patient affected by Terrien marginal degeneration. This new technique shows promise in studying this still elusive pathology.

Ultrasound evaluation of site-specific effect of simulated microgravity on articular cartilage

Space flight induces acute changes in normal physiology in response to the microgravity environment. Articular cartilage is subjected to high loads under a ground reaction force on Earth. The objectives of this study were to investigate the site dependence of morphological and ultrasonic parameters of articular cartilage and to examine the site-specific responses of articular cartilage to simulated microgravity using ultrasound biomicroscopy (UBM). Six rats underwent tail suspension (simulated microgravity) for four weeks and six other rats were kept under normal Earth gravity as controls. Cartilage thickness, ultrasound roughness index (URI), integrated reflection coefficient (IRC) and integrated backscatter coefficient (IBC) of cartilage tissues, as well as histological degeneration were measured at the femoral head (FH), medial femoral condyle (MFC), lateral femoral condyle (LFC), patello-femoral groove (PFG) and patella (PAT). The results showed site dependence not significant in all UBM parameters except cartilage thickness (p < 0.01) in the control specimens. Only minor changes in articular cartilage were induced by 4-week tail suspension, although there were significant decreases in cartilage thickness at the MFC and PAT (p < 0.05) and a significant increase in URI at the PAT (p < 0.01). This study suggested that the 4-week simulated microgravity had only mild effects on femoral articular cartilage in the rat model. This information is useful for human spaceflight and clinical medicine in improving understanding of the effect of microgravity on articular cartilage. However, the effects of longer duration microgravity experience on articular cartilage need further investigation.