Reis-Bücklers corneal dystrophy: a reappraisal using in vivo and ex vivo imaging techniques

Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy

PURPOSE

During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM.

METHODS

31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.

RESULTS

The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia.

CONCLUSIONS

Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

Recurrence Characteristics on Optical Coherence Tomography and Treatments of Reis-Bücklers Corneal Dystrophy After Phototherapeutic Keratectomy or Penetrating Keratoplasty

PURPOSE

To evaluate the recurrence characteristics on optical coherence tomography and clinical outcomes after phototherapeutic keratectomy (PTK) or penetrating keratoplasty (PKP) in patients with Reis-Bücklers corneal dystrophy (RBCD).

DESIGN

Retrospective interventional case series.

METHODS

Seventeen patients with RBCD (31 eyes, including 6 surgery-naïve eyes and 25 surgical eyes) received 44 surgical interventions from 1996 through 2022. PTK or PKP was performed as the initial surgical procedure. Significant recurrence was determined when best spectacle-corrected visual acuity decreased at least 2 lines with increased opacity in the superficial cornea. Repeated PTK or PTK on the corneal graft (CG-PTK) was considered if patients could not endure poor vision due to significant recurrence. Recurrence depth and annual increase in thickness of the central cornea and subepithelial deposits were assessed by anterior segment optical coherence tomography.

RESULTS

The mean follow-up time was 12.8 ± 8.5 years (range, 2.0-25.5 years). The mean logMAR best spectacle-corrected visual acuity improved from 1.24 ± 0.48 preoperatively to 0.27 ± 0.09 postoperatively in the initial PTK group (13 eyes, P < .001), from 1.84 ± 0.69 to 0.40 ± 0.13 in the PKP group (12 eyes, P < .001), from 1.04 ± 0.46 to 0.30 ± 0.07 in the repeated PTK group (12 times in 7 eyes, P < .001), and from 1.29 ± 0.43 to 0.39 ± 0.11 in the CG-PTK group (7 times in 5 eyes, P = .001). The median significant recurrence time was 27 months (95% confidence interval 23.9-30.1), 96 months (84.1-107.9), 31 months (28.8-33.1), and 24 months (19.8-28.2), respectively (P < .001). The depth of superficial deposits located between the epithelium and the anterior stroma was approximately 115 µm (85-159 µm). The annual thickening of subepithelial deposits was 14 ± 2 µm after initial PTK, 7 ± 3 µm after PKP, 14 ± 3 µm after repeated PTK, and 30 ± 11 µm after CG-PTK, compared to 4 ± 2 µm in surgery-naïve eyes (P = .002, .515, .002, <.001). The thickness of the central cornea increased by 15 ± 2 µm, 7 ± 2 µm, 15 ± 3 µm, and 31 ± 10 µm per year in the 4 surgery groups, respectively, compared to 5 ± 2 µm in surgery-naïve eyes (P = .001, .469, .001, <.001).

CONCLUSIONS

Better visual acuity can be achieved after PTK than PKP for treatment of RBCD. The annual thickening of subepithelial deposits may approximate an increase in central corneal thickness. The superficial distribution of subepithelial deposits makes it feasible to perform repeated PTK, even on the corneal allograft, for recurrent RBCD.

The observation of anterior segment in children with an R124L mutation corneal dystrophy by anterior segment optical coherence tomography and in vivo confocal microscopy

Purpose

To evaluate the anterior segment in children with an R124L mutation corneal dystrophy (CD) using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM).

Methods

We investigated a family with prevalent CD and an R124L mutation; 59 individuals (14 patients; 6 male and 8 female, aged 2–69 years, 6 children, 2:4 male: female ratio) from four generations were included. We observed corneal lesions through ophthalmologic examinations, AS-OCT, and IVCM. The mean follow-up was 4.60 ± 3.91 years.

Results

The mean age for childhood CD onset was 0.90 ± 0.61 years. An Avelino DNA test revealed a heterozygous R124L mutation. Clinical manifestations included recurrent photophobia, tearing, and a foreign body sensation. Recurrence frequency decreased with age. Slit lamp microscopy revealed a rough corneal epithelium. The anterior matrix under the corneal epithelium and the anterior elastic layer were scattered with gray and white opacity. From onset to follow-up, the children’s visual acuity decreased from 0.34 ± 0.12 to 0.55 ± 0.17 LogMAR units. AS-OCT showed uneven corneal epithelial thickness. The Bowman’s layer was replaced by abnormal substances in the anterior segment. Corneal deposits became increasingly thicker; the average thickness at the last follow-up was 102.78 ± 10.13 μm. IVCM revealed uneven and reflective signals in the corneal upper cortex and subepithelium, with unclear boundaries and a loss of normal cell morphology.

Conclusion

We report an early age of onset in a family with prevalent CD due to R124L mutations. AS-OCT is a convenient, quick, and non-contact tool for screening and monitoring the pathological process of CD.

In vivo Imaging of Reis-Bücklers and Thiel-Behnke Corneal Dystrophies Using Anterior Segment Optical Coherence Tomography

Purpose

To investigate in vivo corneal changes of genetically confirmed Reis–Bücklers corneal dystrophy (RBCD) and Thiel–Behnke corneal dystrophy (TBCD) using anterior segment optical coherence tomography (AS-OCT).

Design

A single-center, prospective, comparative case series.

Methods

Seven patients from 3 pedigrees (3 males, 4 females) with RBCD [Arg124Leu (R124L) heterozygous missense mutation of human transforming growth factor beta-induced (TGFBI) gene] and 4 patients from 3 pedigrees (3 males, 1 female) with TBCD [Arg555Gln (R555Q) heterozygous missense mutation of TGFBI gene] were examined. Six patients with RBCD and three patients with TBCD exhibited recurrence after corneal surgery including penetrating keratoplasty, phototherapeutic keratectomy, and electrolysis. All patients were examined by slit-lamp biomicroscopy followed by AS-OCT. Selected AS-OCT images of the cornea were evaluated qualitatively for changes in shape and degree of light reflection of corneal deposits.

Results

Slit-lamp biomicroscopy showed characteristic irregular gray opacities in Bowman’s layer in each dystrophy: a geographic pattern in RBCD and a honeycomb pattern in TBCD. In each dystrophy, distinct characteristic deposits were observed by AS-OCT as a banding lesion in Bowman’s layer and its adjacent epithelium/stroma. In RBCD, the banding lesion was highly reflective and sharply margined at the stroma. In contrast, deposits in TBCD in the same layer showed a saw-tooth pattern toward the epithelium and poorly margined at the stroma.

Conclusion

AS-OCT is able to clearly identify characteristic in vivo corneal microstructural changes associated with RBCD and TBCD. As a result, in vivo differentiation of RBCD and TBCD can be achieved.

Microdot Accumulation in the Anterior Cornea with Aging - Quantitative Analysis with in Vivo Confocal Microscopy

PURPOSE

Degenerative 'microdot' deposits in healthy and hypoxic corneas are believed to represent lipofuscin-like material aggregation in the stroma. To accurately assess microdot deposits in a clinical setting, we sought to quantify these deposits for the first time using the non-invasive clinical imaging technique of in vivo confocal microscopy (IVCM).

METHODS

The corneas of 102 healthy subjects aged 15-88 years were examined by IVCM and microdot density was quantified using a 6-point grading scale by two masked, trained examiners. Microdot density was analyzed with respect to age, sex and stromal depth, and inter-eye and inter-observer differences were evaluated.

RESULTS

In healthy subjects, microdot density decreased from the anterior to posterior stroma, with the greatest accumulation observed in the most anterior stroma (subepithelial region). In this region, microdot density correlated strongly with age (P < .0001), with increased microdot deposition in older subjects (>60 years) relative to younger ones (<45 years) (P < .001). Microdot density between eyes of the same subject was highly correlated (r = 0.92, P < .0001), while no association with sex was noted (P ≥ 0.05). The mean inter-observer difference in microdot assessment was 0.62 ± 0.09 grades, with a high correlation of grading between observers (r = 0.77, P < .0001).

CONCLUSIONS

IVCM can be used to non-invasively quantify microdot deposits in the subepithelial corneal stroma with good inter-observer reproducibility. Microdot assessment may provide a novel means of quantifying age-related or pathologic degeneration of the corneal stroma in a clinical setting.