IMMEDIATE SUBRETINAL FLUID DISPLACEMENT FROM THE BUOYANT FORCE OF A SMALL GAS BUBBLE IN PNEUMATIC RETINOPEXY: INSIGHTS INTO THE POTENTIAL MECHANISM OF RETINAL DISPLACEMENT AFTER RETINAL DETACHMENT REPAIR

PURPOSE

To demonstrate how a small gas bubble injected into the vitreous cavity in pneumatic retinopexy for rhegmatogenous retinal detachment causes immediate displacement of subretinal fluid and to gain insights into the potential mechanism of retinal displacement.

METHODS

Three patients with rhegmatogenous retinal detachment who underwent pneumatic retinopexy were enrolled and prospectively followed. All patients underwent ultra-widefield fundus photography at baseline and at 1 to 2 minutes after intravitreal gas injection.

RESULTS

In all cases, the ultra-widefield fundus photograph demonstrated immediate displacement of subretinal fluid, suggesting that the buoyant force applied to the retina by the bubble was responsible for the displacement of subretinal fluid. The results were extrapolated to determine the buoyant force applied by a small and large gas bubble as in pneumatic retinopexy and pars plana vitrectomy. We determined that the buoyant force applied with a larger bubble in pars plana vitrectomy was substantially greater, and this may lead to retinal displacement.

CONCLUSION

Intravitreal gas applies significant buoyant force to the detached retina and subretinal fluid that leads to substantial and rapid displacement of subretinal fluid. Understanding the affect of the buoyant force of the gas bubble on the detached retina can provide insight into possible mechanisms of retinal displacement.

Pathophysiology of outer retinal corrugations: Imaging dataset and mechanical models

This article presents high-resolution swept-source optical coherence tomography (SS-OCT) imaging data used to elaborate a mechanical model that elucidates the formation of outer retinal corrugations (ORCs) in rhegmatogenous retinal detachments (RRD). The imaging data shared in the repository and presented in this article is related to the research paper entitled "Outer Retinal Corrugations in Rhegmatogenous Retinal Detachment: The Retinal Pigment Epithelium-Photoreceptor Dysregulation Theory" (Muni et al., AJO, 2022). The dataset consists of 69 baseline cross-sectional SS-OCT scans from 66 patients that were assessed for the presence of ORCs and analyzed considering the clinical features of each case. From the 66 cases, we selected SS-OCT images of 4 RRD patients with visible ORCs and no cystoid macular edema (CME) to validate the mechanical model. We modelled the retina as a composite material consisting of the outer retinal layer (photoreceptor layer) and the inner retinal layer (the part of the retina that excludes the photoreceptor layer) with thicknesses T o and T i and elastic modulus E o and E i , respectively. The thickness of the outer and inner retinal layers and the relative increase in the length of the outer retinal layer (γ) were measured from the SS-OCT images. Measurements from the SS-OCT images of patients with RRD demonstrated a 30% increase (γ=0.3) in the length of the outer retinal layer and a 400% increase in the thickness of the outer retinal layer (To). Using the mathematical model, Eo/Ei ranged between 0.05 to 0.5 to result in ORCs with a similar frequency to those observed in the SS-OCT scans.

En Face OCT in Diagnosis of Persistent Subretinal Fluid and Outer Retinal Folds after Rhegmatogenous Retinal Detachment Repair

PURPOSE

To evaluate the role of en face OCT as a diagnostic tool for the detection of persistent subretinal fluid (PSRF) and outer retinal folds (ORFs) after successful rhegmatogenous retinal detachment (RRD) repair.

DESIGN

Observational post hoc analysis of 2 prospective surgical trials.

PARTICIPANTS

All patients with gradable (signal strength ≥ 5 and no segmentation error) 6 × 6-mm² macular cube scans obtained using spectral-domain OCT (Carl Zeiss Meditec) between 1 and 2 months after surgery were included in this study.

METHODS

The scans were assessed for the presence or absence of PSRF or ORFs using en face OCT and cross-sectional B scans by 2 masked graders, with any disagreements adjudicated by a third senior masked grader.

MAIN OUTCOME MEASURES

The sensitivity, specificity, and predictive accuracy (using area under the curve [AUC]) of en face OCT were compared with those of cross-sectional OCT, which is considered the gold standard.

RESULTS

Two hundred twenty-three patients were included in this study. The Cohen kappa between the graders in the diagnosis of PSRF and ORFs using en face OCT was 0.84 and 0.86, respectively. The sensitivity of en face OCT was 100% (95% confidence interval [CI], 100%-100%) in the diagnosis of PSRF and 98.8% (95% CI, 96.5%-101.1%) in the diagnosis of ORFs. Similarly, the specificity of en face OCT was 98.7% (95% CI, 96.8%-100.5%) and 84.2% (95% CI, 78.1%-90.2%) in the diagnosis of PSRF and ORFs, respectively. The AUC was 0.99 for PSRF and 0.91 for ORFs.

CONCLUSIONS

En face OCT has good sensitivity, specificity, and predictive accuracy (using AUC) in the diagnosis of PSRF and ORFs. En face OCT is an efficient screening tool for postoperative anatomic abnormalities, such as PSRF and ORFs, after RRD repair.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Outer Retinal Corrugations in Rhegmatogenous Retinal Detachment: The Retinal Pigment Epithelium-Photoreceptor Dysregulation Theory

PURPOSE

Outer retinal folds occur when outer retinal corrugations (ORCs) persist after retinal reattachment with worse functional outcomes. We investigate the pathophysiology of ORCs in vivo.

DESIGN

Prospective cohort study.

METHODS

Patients with rhegmatogenous retinal detachment (RRD) presenting to St. Michael's Hospital, Toronto, Ontario, Canada, between August 2020 and February 2022 were assessed with swept-source optical coherence tomography (SS-OCT) and ultra-widefield SS-OCT for ORCs. Clinical characteristics of eyes with/without ORCs were compared. Mathematical models were used to deduce mechanical properties leading to ORCs.

RESULTS

Sixty-six patients were included. More than half (60.6%, 40/66) were fovea-off and 48.4% (32/66) had ORCs at presentation. All eyes (32/32) with ORCs had retinal pigment epithelium (RPE)-photoreceptor dysregulation for at least 2 days, defined as loss of RPE control with acute, progressive, and extensive RRDs. In all (34/34) eyes without ORCs the RPE was in relative control of the subretinal space with nonprogressive subclinical or small localized or resolving RRDs, or with RPE-photoreceptor dysregulation for fewer than 2 days. Mathematical models indicate that a modulus of elasticity of the outer retina relative to the inner retina of 0.05 to 0.5 leads to ORCs.

CONCLUSIONS

ORCs develop with (1) acute exposure of subretinal space to liquified vitreous, (2) for >2 days, that (3) overwhelms RPE capacity, leading to progressive and extensive RRD. Mathematical models suggest that a reduction in the modulus of elasticity of the outer retina occurs such that intrinsic compressive forces, likely related to progressive outer retinal hydration and lateral expansion, lead to ORCs. Understanding the pathophysiology of ORCs has implications for management.

Morphologic Stages of Rhegmatogenous Retinal Detachment Assessed Using Swept-Source OCT

PURPOSE

To describe the sequential morphologic changes after rhegmatogenous retinal detachment (RRD) utilizing a novel, objective, and clinically relevant staging system based on swept-source OCT (SS-OCT) and determine its association with the duration of fovea-off and postoperative visual acuity (VA).

DESIGN

Prospective cohort study.

SUBJECTS

Consecutive patients with primary fovea-involving RRD referred to St. Michael's Hospital, Toronto, Canada, from January 2020 to April 2022.

METHODS

All patients underwent SS-OCT and ultrawide-field SS-OCT at baseline. Primary RRDs with breaks above the 8- and 4-o'clock meridians were included. Patients with vision loss for ≥ 3 months, proliferative vitreoretinopathy grade C or worse, a demarcation line, previous vitrectomy, or other retinal pathology were excluded. The staging was based on an assessment of outer retinal morphology on successive SS-OCT scans from the peripheral break to the most posterior aspect of the RRD, following its direction of progression.

MAIN OUTCOME MEASURES

Sequential outer retinal morphologic changes observed using SS-OCT and associated VA at 3 months after surgery.

RESULTS

Forty-nine eyes were included. The mean age (standard deviation [SD]) was 61.2 (15.2) years. The mean presenting logarithm of the minimum angle of resolution (SD) acuity was 1.09 (0.75). All stages observed on a high-definition horizontal 51-line scan were reported. Outer retinal changes occurred in 5 stages: (1) separation of the neurosensory retina from the retinal pigment epithelium (42/49, 85.7%); (2) thickening of inner and outer segments of photoreceptors (45/49, 91.8%); (3) outer retinal corrugation formation: (3a) low-frequency (44/49, 93.6%) and (3b) high-frequency outer retinal corrugations (42/49, 85.7%); (4) loss of the definition of outer retinal corrugations, with concurrent thickening of inner and outer segments (26/49, 53.1%); and (5) patchy (moth-eaten) or complete loss of inner and outer segments (17/49, 34.7%). The mean duration of fovea-off by stage in the parafovea (SD) was 2 (1.4), 2.3 (1.2), 11.4 (8.1), and 12 (13.3) days for stages 3a, 3b, 4, and 5, respectively. There was a statistically significant association between increasing stage of RRD and longer duration of foveal involvement (P = 0.001) and, most importantly, between increasing stage and worse VA at 3 months after surgery (P = 0.011).

CONCLUSIONS

This novel staging system describes the sequential morphologic changes in RRD using SS-OCT. Increasing stage of RRD was associated with worse VA at 3 months after surgery.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Paracentral acute middle maculopathy following hepatitis B vaccine

Purpose

To report a case of paracentral acute middle maculopathy (PAMM) following Hepatitis B vaccine in a child.

Observations

A 12-year-old healthy female presented with a paracentral scotoma in the right eye due to PAMM, likely associated with a recent Hepatitis B vaccine.

Conclusions

Despite the great importance of vaccines, it is critical to promptly recognize their rare ocular complications, such as the vaccine associated PAMM described in this report.

Inner shell as variation key of local hard clam Meretrix spp

The morphology and 12 shell morphometric features proportionate to shell length were analysed between local hard clam; Meretrix lyrata, M. meretrix and M. lusoria from Sarawak, Malaysia. Meretrix spp. was observed to comprise a unique feature of a pallial sinus scar for each species. Analysis of variance revealed significant differences among Meretrix spp. using proportion ratios of SL for SW; LL; AL; LCT; AW; PW and PS (p<0.05). Cluster analysis among morphometric features of M. lyrata, M. meretrix and M. lusoria were discriminated at 98.5% similarities and supported by the principal component analysis. The present study suggests that pallial sinus scar shape, together with interior and exterior morphometric features, were suitable as identification keys for Meretrix spp. Hence, the present study emphasizes on the application of interior, rather than exterior morphology and morphometric features in hard clam identification before further investigation can be performed through genetic identification means.