Impact of acute intraocular pressure elevation on the visual acuity of non-human primates

Recent advances in nanogels for drug delivery and biomedical applications

Nanotechnology has shown great promise for researchers to develop efficient nanocarriers for better therapy, imaging, and sustained release of drugs. The existing treatments are accompanied by serious toxicity limitations, leading to severe side effects, multiple drug resistance, and off-target activity. In this regard, nanogels have garnered significant attention for their multi-functional role combining advanced therapeutics with imaging in a single platform. Nanogels can be functionalized to target specific tissues which can improve the efficiency of drug delivery and other challenges associated with the existing nanocarriers. Translation of nanogel technology requires more exploration towards stability and enhanced efficiency. In this review, we present the advances and challenges related to nanogels for cancer therapy, ophthalmology, neurological disorders, tuberculosis, wound healing, and anti-viral applications. A perspective on recent research trends of nanogels for translation to clinics is also discussed.

The role of TRPV4 in the regulation of retinal ganglion cells apoptosis in rat and mouse

Retinal ganglion cell (RGC) damages are common in glaucoma, causing atrophy of the optic papilla, visual field damage, and visual loss. Transient receptor potential vanilloid 4 (TRPV4) is significantly expressed in the eyeball and is sensitive to mechanical and osmotic pressure. However, the specific role and mechanism of TRPV4 in glaucoma and RGC progression remain unclear. TRPV4 expression was detected in RGCs under different pressure culture conditions. We also explored the pressure effect on TRPV4 expression and the role and mechanism behind the functional regulation of RGCs. Immunofluorescence staining, western blotting, and TUNEL were utilized in this study. Our results established that TRPV4 was expressed in RGCs. TRPV4 expression was decreased at 40 mmHg and 60 mmHg, and the expression of BAX at 40 mmHg, 60 mmHg. Additionally, the expression of caspase 9 protein increased at 40 mmHg with the pressure increase compared with the conventional culture group. TUNEL staining revealed that the apoptosis rate of RGCs was elevated at 40 mmHg and 60 mmHg, compared with the traditional culture group. Therefore, the expression of BAX and caspase 9 increased, along with the apoptosis rate of RGCs compared with the control group. However, after TRPV4 antagonist treatment, the expression of BAX and caspase 9 decreased, and the apoptosis rate of RGCs decreased. Thus, TRPV4 may affect the mitochondrial apoptosis pathway, such as BAX and caspase 9, leading to the apoptosis of RGCs. The antagonists of TRPV4 could provide a new idea for clinically treating acute glaucoma.

Identifying new drugs and targets to treat rapidly elevated intraocular pressure for angle closure and secondary glaucomas to curb visual impairment and prevent blindness

A multitude of pharmacological compounds have been shown to lower and control intraocular pressure (IOP) in numerous species of animals and human subjects after topical ocular dosing or via other routes of administration. Most researchers have been interested in finding drug candidates that exhibit a relatively long duration of action from a chronic therapeutic use perspective, for example to treat ocular hypertension (OHT), primary open-angle glaucoma and even normotensive glaucoma. However, it is equally important to seek and characterize treatment modalities which offer a rapid onset of action to help provide fast relief from quickly rising IOP that occurs in certain eye diseases. These include acute angle-closure glaucoma, primary angle-closure glaucoma, uveitic and inflammatory glaucoma, medication-induced OHT, and other secondary glaucomas induced by eye injury or infection which can cause partial or complete loss of eyesight. Such fast-acting agents can delay or prevent the need for ocular surgery which is often used to lower the dangerously raised IOP. This research survey was therefore directed at identifying agents from the literature that demonstrated ocular hypotensive activity, normalizing and unifying the data, determining their onset of action and rank ordering them on the basis of rapidity of action starting within 30-60 min and lasting up to at least 3-4 h post topical ocular dosing in different animal species. This research revealed a few health authority-approved drugs and some investigational compounds that appear to meet the necessary criteria of fast onset of action coupled with significant efficacy to reduce elevated IOP (by ≥ 20%, preferably by >30%). However, translation of the novel animal-based findings to the human conditions remains to be demonstrated but represent viable targets, especially EP2-receptor agonists (e.g. omidenepag isopropyl; AL-6598; butaprost), mixed activity serotonin/dopamine receptor agonists (e.g. cabergoline), rho kinase inhibitors (e.g. AMA0076, Y39983), CACNA2D1-gene product inhibitors (e.g. pregabalin), melatonin receptor agonists, and certain K+-channel openers (e.g. nicorandil, pinacidil). Other drug candidates and targets were also identified and will be discussed.

Effects of acute high intraocular pressure on red-green and blue-yellow cortical color responses in non-human primates

Glaucoma is a leading cause of irreversible blindness worldwide, and intraocular pressure (IOP) is an established and modifiable risk factor for both chronic and acute glaucoma. The relationship between color vision deficits and chronic glaucoma has been described previously. However, the effects of acute glaucoma or acute primary angle closure, which has high prevalence in China, on color vision remains unclear. To address the above question, red-green or blue-yellow color responses in V1, V2, and V4 of seven rhesus macaques were monitored using intrinsic-signal optical imaging while monocular anterior chamber perfusions were performed to reversibly elevate IOP acutely over a clinically observed range of 30 to 90 mmHg. We found that the cortical population responses to both red-green and blue-yellow grating stimuli, systematically decreased as IOP increased from 30 to 90 mmHg. Although a similar decrement in magnitude was noted in V1, V2, and V4, blue-yellow responses were consistently more impaired than red-green responses at all levels of acute IOP elevation and in all monitored visual areas. This physiological study in non-human primates demonstrates that acute IOP elevations substantially depress the ability of the visual cortex to register color information. This effect is more severe for blue-yellow responses than for red-green responses, suggesting selective impairment of the koniocellular pathways compared with the parvocellular pathways. Together, we infer that blue-yellow color vision might be the most vulnerable visual function in acute glaucoma patients.

Safety of EVO ICL Implantation With an Ophthalmic Viscosurgical Device-Free Technique in the Early 24 h After Surgery

Purpose: To compare the safety of the non-ophthalmic viscosurgical device (OVD) technique with that of the minimum OVD technique in EVO Implantable Collamer Lens (EVO-ICL) implantation.

Methods: A total of 180 eyes of 90 consecutive patients were enrolled in the study, of which 100 eyes of 50 patients were treated with non-OVD technique, with a 55% success rate. The remaining 80 eyes of 40 patients were treated with min-OVD technique, so they were classified into the min-OVD group. Preoperative and postoperative intraocular pressure (IOP) measurements were collected and analyzed at 1, 2, 3, and 24 h. Visual acuity, corneal endothelial cell density (ECD), and corneal densitometry 24 h postoperatively were evaluated.

Results: No significant difference was found in visual outcomes (P = 0.54) or ECD (P = 0.78) between the two groups. The operation time was significantly shorter in the non-OVD group (P < 0.0001). The IOP was significantly higher at 1 h (P < 0.0001), 2 h (P < 0.0001) and 3 h (P = 0.0045) postoperatively in the min-OVD group. The non-OVD group had significantly lower IOP than the min-OVD group at 1 h (P = 0.01) and 2 h (P = 0.013) postoperatively. The temporal corneal densitometry in the non-OVD group were significantly lower than those in the minimum group (P = 0.0063) 1 day after surgery.

Conclusion: The non-OVD technique is safe and efficient for ICL implantation. It can be a safer method of ICL implantation in that it completely eliminates ophthalmic viscoelastic devices related complications without causing additional complications in short term.

Transneuronal Degeneration in the Brain During Glaucoma

The death of retinal ganglion cells (RGCs) is a key factor in the pathophysiology of all types of glaucoma, but the mechanism of pathogenesis of glaucoma remains unclear. RGCs are a group of central nervous system (CNS) neurons whose soma are in the inner retina. The axons of RGCs form the optic nerve and converge at the optic chiasma; from there, they project to the visual cortex via the lateral geniculate nucleus (LGN). In recent years, there has been increasing interest in the dysfunction and death of CNS and retinal neurons caused by transneuronal degeneration of RGCs, and the view that glaucoma is a widespread neurodegenerative disease involving CNS damage appears more and more frequently in the literature. In this review, we summarize the current knowledge of LGN and visual cortex neuron damage in glaucoma and possible mechanisms behind the damage. This review presents an updated and expanded view of neuronal damage in glaucoma, and reveals new and potential targets for neuroprotection and treatment.

Immediate Impact of Acute Elevation of Intraocular Pressure on Cortical Visual Motion Processing

Purpose

To physiologically examine the impairment of cortical sensitivity to visual motion during acute elevation of intraocular pressure (IOP).

Methods

Motion processing in the cat brain is well characterized, its X and Y cell visual pathways being functionally analogous to parvocellular and magnocellular pathways in primates. Using this model, we performed ocular anterior chamber perfusion to reversibly elevate IOP over a range from 30 to 90 mm Hg while monitoring cortical activity with intrinsic signal optical imaging. Drifting random-dot fields and gratings were used to characterize cortical population responses to motion direction and orientation in early visual areas 17 and 18.

Results

We found that acute IOP elevations at 50 mm Hg and above, which is often observed in acute glaucoma, suppressed cortical motion direction responses. This suppression was more profound in area 17 than in area 18, and more profound in central than peripheral visual field (eccentricities 0°–4° vs. 4°–8°) within area 17. In addition, orientation responses were more suppressed than motion direction responses for the same IOP modulation.

Conclusions

In contrast to human chronic glaucoma that may cause greater dysfunction in large-cell magnocellular than in small-cell parvocellular visual pathways, our direct measurement of cortical processing networks implies that the small X-cell pathway shows greater vulnerability to acute IOP elevation than the large Y-cell pathway in visual motion processing. The results demonstrate that fine discrimination mechanisms for motion in the central visual field are particularly impacted by acute IOP attacks, suggesting a neural basis for immediate visual deficits in the fine motion perception of acute glaucoma patients.

A comparative study on the effects of flexible and rigid laryngoscopy techniques on intraocular pressure

OBJECTIVES

This study compared the impact of transoral rigid laryngoscopy (TORL) and transnasal flexible laryngoscopy (TNFL) methods on intraocular pressure (IOP).

METHODS

This study included 100 patients, with 50 patients undergoing a TORL, and 50 patients a TNFL. Before procedure IOP values were recorded by an ophthalmologist using Icare Pro tonometry, also immediately post procedure, and at the 15th, 30th and 60th minute after laryngoscopy.

RESULTS

Both groups were similar in terms of age, gender, mean body mass index (BMI), and pre-laryngoscopy IOP values. When the TNFL and TORL groups were compared, no significant differences were observed between pre-laryngoscopy, and 60^th minute IOP values (p = 0.891, p = 0.149, respectively). IOP values measured immediately after laryngoscopy, and at the 15th and 30th minute were significantly higher in the TORL group (p < 0.001, p < 0.001, p = 0.002, respectively).

CONCLUSIONS

We demonstrated higher IOP fluctuations in the TORL group, when compared to the TNFL group. For this reason, TNFL may be considered a safer method for evaluating laryngeal tissues in conditions that require lower IOP fluctuation as in glaucoma. However, further studies are required to clarify the exact effects of IOP fluctuations during TNFL and TORL in patients with glaucoma.

Impact of Visual Field Testing on Intraocular Pressure Change Trends in Healthy People and Glaucoma Patients

PURPOSE

To compare the impact of visual field (VF) testing on intraocular pressure (IOP) change trends between healthy subjects and glaucoma patients.

METHODS

We recruited healthy volunteer subjects who did not have previous ocular diseases and open-angle glaucoma patients who were medically controlled well. IOP in both eyes of each participant was measured by using a noncontact tonometer at five time points: before, immediately after (0 minute), and 10, 30, and 60 minutes after the standard automated perimetry. Repeated measures ANOVA was used to analyze the effect of VF testing on IOP change trends in healthy and glaucoma eyes.

RESULTS

Forty healthy subjects (80 eyes) and 31 open-angle glaucoma patients (62 eyes) were included for the study. The baseline IOP of healthy and glaucoma eyes was 16.11 ± 3.01 mmHg and 15.78 ± 3.57 mmHg, respectively. After the VF testing, the IOP in healthy eyes was decreased by 1.5% at 0 minute, 6.5% at 10 minutes (P < 0.001), 6.6% at 30 minutes (P < 0.001), and 7.0% at 1 hour (P < 0.001), indicating that this reduction was sustained for at least 1 hour. However, the IOP in glaucoma eyes was increased by 12.7% at 0 minute (P < 0.001) and, then, returned towards initial values 1 hour after the VF testing.

CONCLUSIONS

IOP change trends after VF field testing between healthy subjects and glaucoma patients were quite different. VF testing led to a mild and relatively sustained IOP decrease in healthy subjects, whereas IOP in open-angle glaucoma patients tended to significantly increase immediately after VF testing and, then, returned to pretest values after 1 hour. These findings indicate that the factors of VF testing should be considered in the clinical IOP measurements.

Safety of the Minimum Ophthalmic Viscosurgical Device Technique in Phakic Implantable Collamer Lens Implantation

PURPOSE

To compare the safety of the minimum ophthalmic viscosurgical device (OVD) technique with the standard procedure in phakic Visian Implantable Collamer Lens (ICL) (STAAR Surgical AG, Nidau, Switzerland) implantation.

METHODS

This retrospective cohort study evaluated a total of 147 eyes of 74 patients who underwent ICL implantation with the minimum OVD technique (minimum OVD group) and 154 eyes of 77 patients with the standard procedure (standard OVD group). Intraoperative and postoperative complications were recorded. Preoperative and postoperative visual acuity, intraocular pressure (IOP), aqueous depth (AQD), and central corneal endothelial cell density (ECD) were collected and analyzed over the 12-month follow-up. Lens vault and occurrence of paracentesis after surgery were also recorded.

RESULTS

No intraocular complications were observed. No difference was found in visual outcomes, lens vault, and AQD at all time points between the two groups (P > .05). The minimum OVD group had significantly lower IOP than the standard OVD group at 2 hours (17.04 ± 4.21 vs 19.40 ± 6.78 mm Hg, P < .001) and 3 hours (15.12 ± 3.38 vs 17.15 ± 5.09 mm Hg, P < .001) postoperatively. The IOP gradually returned to the preoperative level after 24 hours postoperatively. The occurrence rate of paracentesis was significantly less in the minimum OVD group compared with the standard group (0.68% [1 of 147] vs 3.2% [5 of 154], P < .001). ECD was not significantly different between groups at all time points (P > .05).

CONCLUSIONS

The minimum OVD technique could achieve visual and structural outcomes comparable to the standard procedure without additional damage to the corneal endothelial cells, while reducing the IOP fluctuations after surgery. [J Refract Surg. 2020;36(1):42-48.].