Misdirected aqueous flow in rhegmatogenous retinal detachment: A pathophysiology update

Insights into myopic choroidal neovascularization based on quantitative proteomics analysis of the aqueous humor

BACKGROUND

Previous studies on the biomarkers of pathologic myopia choroidal neovascularization (pmCNV) development merely detected limited types of proteins and provide a meagre illustration of the underlying pathways. Hence, a landscape of protein changes in the aqueous humor (AH) of pmCNV patients is lacking. Here, to explore the potential mechanisms and biomarkers of pmCNV, we analyzed the clinical data and protein profile among atrophic (A) lesions, tractional lesions (T) and neovascular (N) lesions in myopic patients based on the ATN grading system for myopic maculopathy (MM).

RESULTS

After investigating demographic data of our patients, a correlation was found between A and N lesions (R = 0.5753, P < 0.0001). Accordingly, groups were divided into patients without MM, patients with myopic atrophic maculopathy (MAM), and patients with pmCNV (N2a lesion). In proteomics analysis, the increased protein level of GFAP and complement-associated molecules in AH samples of the 3 groups also indicated that MAM and pmCNV shared similar characteristics. The GO enrichment and KEGG pathway analysis were performed, which mapped that differential expressed proteins mainly engaged in JAK-STAT pathway between the pmCNV group and two controls. Furthermore, we identified several potential biomarkers for pmCNV, including FCN3, GFAP, EGFR, SFRP3, PPP2R1A, SLIT2, and CD248.

CONCLUSIONS

Atrophic lesions under pathologic myopic conditions demonstrated similarities to neovascularization development. Potential biomarkers including GFAP were associated with the pathogenesis of pmCNV. In summary, our study provides new insights for further research on pmCNV development.

Outer Retinal Hyperreflective Dots: A Potential Imaging Biomarker in Rhegmatogenous Retinal Detachment

PURPOSE

To investigate hyperreflective dots (HRDs) on baseline OCT in rhegmatogenous retinal detachment (RRD).

DESIGN

Retrospective cohort study.

SUBJECTS

Consecutive primary fovea-off RRDs presenting between January 2012 and September 2022.

METHODS

Visual acuity (VA) was obtained at baseline, 3, 6, and 12 months. Baseline foveal OCT scans were graded for the presence of HRDs in the outer retina, morphologic stage of RRD in the parafovea, and foveal photoreceptor integrity (intact, patchy or complete loss of the bacillary layer). Epiretinal membrane (ERM) and cystoid macular edema (CME) were graded after surgery.

MAIN OUTCOME MEASURES

The primary outcome was the proportion of patients in each morphologic stage with HRDs present on OCT and their association with postoperative VA. Secondary outcomes included association with the height of foveal detachment, duration of central vision loss, RRD extent, and development of ERM/CME.

RESULTS

A total of 351 patients were included. The presence of HRDs by morphologic stage of RRD was 0% in stage 1, 4.5% (2/42) in stage 2, 13% (7/54) in stage 3a, 16% (20/126) in stage 3b, 48% (40/83) in stage 4, and 85% (35/41) in stage 5. Hyperreflective dots were associated with increasing stage of RRD (P < 0.001), reduced integrity of foveal photoreceptors (P < 0.001), and reduced postoperative VA at 3, 6, and 12 months (P < 0.001), after excluding visually significant cataracts and adjusting for covariates. There was also a significant association between HRDs and height of foveal detachment, duration of central vision loss, and RRD extent (P < 0.001). Hyperreflective dots were neither associated with postoperative ERM formation nor with its severity (P = 0.27). Nevertheless, they were associated with the occurrence of CME at 3 and 6 months after surgery (P = 0.01; P = 0.006).

CONCLUSIONS

Hyperreflective dots have been hypothesized to consist of intraretinal inflammatory cells. We found that HRDs were significantly associated with the morphologic stage, extent, duration, and height of the RRD before surgery and with reduced VA and CME after surgery. Our results suggest that HRDs are associated with photoreceptor degeneration, as longstanding and extensive RRDs are more likely to present with HRDs. The association of HRDs with CME provides insight into the possible importance of inflammatory processes in RRD before and after surgery.

FINANCIAL DISCLOSURE(S)

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

Ultrasound-Mediated Ocular Drug Delivery: From Physics and Instrumentation to Future Directions

Drug delivery to the anterior and posterior segments of the eye is impeded by anatomical and physiological barriers. Increasingly, the bioeffects produced by ultrasound are being proven effective for mitigating the impact of these barriers on ocular drug delivery, though there does not appear to be a consensus on the most appropriate system configuration and operating parameters for this application. In this review, the fundamental aspects of ultrasound physics most pertinent to drug delivery are presented; the primary phenomena responsible for increased drug delivery efficacy under ultrasound sonication are discussed; an overview of common ocular drug administration routes and the associated ocular barriers is also given before reviewing the current state of the art of ultrasound-mediated ocular drug delivery and its potential future directions.

Polymer based sustained drug delivery to the ocular posterior segment: barriers and future opportunities for the treatment of neovascular pathologies

There is an increasing momentum in research and pharmaceutical industry communities to design sustained, non-invasive delivery systems to treat chronic neovascular ocular diseases that affect the posterior segment of the eye including age-related macular degeneration and diabetic retinopathy. Current treatments include VEGF blockers, which have revolutionized the standard of care for patients, but their maximum therapeutic benefit is hampered by the need for recurrent and invasive administration procedures. Currently approved delivery systems intended to address these limitations exploit polymer technology to regulate drug release in a sustained manner. Here, we critically review sustained drug delivery approaches for the treatment of chronic neovascular diseases affecting the ocular posterior segment, with a special emphasis on novel and polymeric technologies spanning the spectrum of preclinical and clinical investigation, and those approved for treatment. The mechanism by which each formulation imparts sustained release, the impact of formulation characteristics on release and foreign body reaction, and special considerations related to the translation of these systems are discussed.

Electron Microscopic Evidence of Photoreceptor Outer-segments in the Trabecular Meshwork in a Case of Schwartz-Matsuo Syndrome

PURPOSE

To describe a case of photoreceptor outer segment glaucoma (Schwartz-Matsuo syndrome) with electron microscopic evidence of photoreceptor outer segments in the trabecular meshwork (TM).

DESIGN

This is a clinicopathologic case report.

PARTICIPANT

A 48-year-old Filipino man.

METHODS

Specimens of aqueous humor and TM in a clinical case of Schwartz-Matsuo syndrome were examined by electron microscopy.

MAIN OUTCOME MEASURES

Electron photomicroscopy.

RESULTS

Electron microscopy showed evidence of retinal photoreceptor outer-segments in both an aqueous humor and a TM specimen.

CONCLUSION

Schwartz-Matsuo syndrome is associated with the presence of photoreceptor outer segments in the TM.

Suspected Spontaneous Aqueous Humor Misdirection Syndrome in a Boston Terrier

An eight-year-old female spayed Boston Terrier presented to the North Carolina Veterinary Hospital with glaucoma in the left eye (OS). Initial ophthalmic examination revealed moderate ocular hypertension, a diffusely and markedly shallow anterior chamber with anteriorly displaced iris and lens, vitreal prolapse, and a normal iridocorneal angle (ICA) morphology. The patient displayed a paradoxical response to topical latanoprost with an increase in intraocular pressure. These examination findings led to a putative diagnosis of spontaneous aqueous humor misdirection syndrome (AHMS). The patient was successfully managed with topical carbonic anhydrase inhibitors (CAIs) and apraclonidine for eight months until progressive ulcerative keratitis necessitated enucleation of the affected globe. Histopathology and high-field magnetic resonance imaging (MRI) of the enucleated globe did not identify an underlying cause for the glaucoma. This case suggests that AHMS should be considered in dogs presenting with a shallow anterior chamber, vitreal prolapse, increased intraocular pressure, and no other causes of glaucoma.

No flow through the vitreous humor: How strong is the evidence?

When analyzing vitreal drug delivery, or the pharmacological effects of drugs on intraocular pressure, or when interpreting outflow facility measurements, it is generally accepted that the fluid in the vitreous humor is stagnant. It is accepted that for all practical purposes, the aqueous fluid exits the eye via anterior pathways only, and so there is negligible if any posteriorly directed flow of aqueous through the vitreous humor. This assumption is largely based on the interpretation of experimental data from key sources including Maurice (1957), Moseley (1984), Gaul and Brubaker (1986), Maurice (1987) and Araie et al. (1991). However, there is strong independent evidence suggesting there is a substantial fluid flow across the retinal pigment epithelium from key sources including Cantrill and Pederson (1984), Chihara and Nao-i, Tsuboi (1985), Dahrouj et al. (2014), Smith and Gardiner (2017) and Smith et al. (2019). The conflicting evidence creates a conundrum-how can both interpretations be true? This leads us to re-evaluate the evidence. We demonstrate that the data believed to be supporting no aqueous flow through the vitreous are in fact compatible with a significant normal aqueous flow. We identify strong and independent lines of evidence supporting fluid flow across the RPE, including our new outflow model for the eye. On balance it appears the current evidence favors the view that there is normally a significant aqueous flow across the RPE in vivo. This finding suggests that past and future analyses of outflow facility, interpretations of some drug distributions and the interpretation of some drug effects on eye tissues, may need to be revised.

Scleral and conjunctival features in patients with rhegmatogenous retinal detachment undergoing scleral buckling: an anterior segment optical coherence tomography and in vivo confocal microscopy study

PURPOSE

To investigate the scleral and conjunctival features in patients with rhegmatogenous retinal detachment (RRD) undergoing scleral buckling (SB), using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM).

METHODS

Twenty RRD eyes were consecutively enrolled. AS-OCT was performed at RRD diagnosis (RRD-D) and day 1, week 1, month 1 and month 6 after SB to evaluate the sclera, in the affected and unaffected quadrants (AQ, UQ). IVCM was performed at RRD-D, and at month 1 and month 6, to evaluate the conjunctiva in AQ and UQ. The main outcomes were as follows: mean intra-scleral hypo-reflective spaces area (MIHSA) at AS-OCT; mean density and area of microcysts (MMD, MMA) at IVCM; and intra-ocular pressure (IOP). The relations between MIHSA, MMA, MMD and IOP were evaluated.

RESULTS

Rhegmatogenous retinal detachment- diagnosis (RRD-D) overall-mean intra-scleral hypo-reflective spaces (MISHA), -MMD and -MMA were significantly higher in affected eye (AE) compared with UE (p < 0.05) and in AQ compared with UQ (p < 0.05). After SB, overall-, AQ- and UQ-MISHA further increased (p < 0.05), whereas overall-MMD and -MMA did not change. At all follow-up, AQ and UQ parameters did not show significant differences between them. RRD-D IOP was 14.3 ± 2.8 and 15.5 ± 2.7 mmHg in the AE and UE, respectively (p < 0.05). After SB, week-1, month-1 and -6 IOP was significantly lower than RRD-D (p < 0.05). Rhegmatogenous retinal detachment- diagnosis (RRD-D), 1- and 6-month overall and AQ-MISHA and AQ-MMD negatively correlated with IOP (p < 0.05).

CONCLUSION

Rhegmatogenous retinal detachment (RRD) and SB induced scleral and conjunctival changes that suggested an activation of fluid outflow through the entire unconventional aqueous humour pathway; these modifications may in part account for the relative hypotony after RRD and SB.

LINCOFF RULES ARE NOT FOLLOWED IN RETINAL DETACHMENT WITH POSTERIOR BREAKS AND ATTACHED CORTICAL VITREOUS

PURPOSE

1) To evaluate factors governing flow of subretinal fluid and validate Lincoff rules (LRs) in cases of rhegmatogenous retinal detachment. 2) To identify cases of rhegmatogenous retinal detachment where LRs are not followed.

METHOD

This was a retrospective study where 253 patients of rhegmatogenous retinal detachment were identified through surgery records. Two hundred and twenty-nine case sheets with complete record of ocular examination and surgical findings were analyzed. Seventy-five of the 229 patients, having subtotal rhegmatogenous retinal detachment where LR could be applied were included for analysis. Validity of LR was analyzed about location of break, lattice degeneration, posterior vitreous detachment (PVD), proliferative vitreoretinopathy, lens status, myopia, and trauma.

RESULT

The mean age of the patients was 40.12 years. Sixty-one were men. Lincoff rule was validated in 59 of the 75 patients. Anterior breaks (P < 0.008) and PVD (P < 0.001) were found to have a significant association with validity of LR. Other attributes did not have a statistically significant association with validity of LR.

CONCLUSION

Presence of posterior retinal breaks and absent PVD is associated with unusual flow of subretinal fluid. Lincoff rules are valid in most of the clinical scenarios.

Traumatic retinal detachment--the difficulty and importance of correct diagnosis

Accurate characterization of a retinal detachment as traumatic is often difficult, but is important because it may instigate a careful search for occult coexistent traumatic pathology, affect the prognosis and the treatment of both eyes, influence insurance coverage benefits and medical-legal determinations, and is essential for epidemiologic studies. We review the epidemiology and pathophysiology of traumatic retinal detachment, common obstacles to correct diagnosis, diagnostic guidelines, and outline categories of traumatic causal relationships. Because there is no generally accepted definition of traumatic retinal detachment, we offer a practical one. Categorization as traumatic should be based on the particular history and physical examination rather than epidemiologic criteria.