Anterior chamber flare and choroidal vascular index as inflammatory markers after uncomplicated phacoemulsification surgery

PURPOSE

To determine the effect of phacoemulsification surgery, which is one of the types of cataract surgery by using ultrasonic power to break up the crystalline lens and clean it with vacuum, on anterior chamber flare (ACF) and choroidal vascular index (CVI).

METHODS

For this cross-sectional study, patients were included if they had cataract with nucleus hardness grade 2 or 3, no systemic inflammatory disease, and not use of anti-inflammatory drugs/prostaglandins preoperatively. ACF using a laser flare meter and CVI in patients underwent uncomplicated phacoemulsification was recorded preoperatively, on the postoperative 1st day, 1st week, and 1st month.

RESULTS

Fifty-six eyes were included. ACF was 9.00 ± 2.90 ph/ms preoperatively. Although ACF increased significantly on postoperative day-1 (39.38 ± 23.31ph/ms) and decreased gradually until the 1st month (14.03 ± 6.03ph/ms) after the operation, it was still significantly higher at the 1st month (p < 0.001). Macular and peripapillary CVI increased significantly on postoperative day-1 (0.64 ± 0.03/0.63 ± 0.05) and week-1 (0.64 ± 0.04/0.62 ± 0.04) (p = 0.01, p < 0.001); the postoperative 1st month was similar to the preoperative one (0.59 ± 0.06/0.58 ± 0.06). The relationship between the change in ACF and the change in CVI was not significant.

CONCLUSION

Phacoemulsification causes raises in ACF and CVI due to increased intraocular inflammation. The fact that ACF was significantly higher in postoperative month-1 and CVI returned to its preoperative value suggests that the effect of uncomplicated phacoemulsification surgery on the increase in inflammation in the anterior segment lasts longer than in the posterior segment. These results suggest that ACF and CVI follow-up may be clinically important in the follow-up of postoperative inflammation.

Ocular posterior segment complications following COVID-19 vaccination

BACKGROUND

The SARS-CoV-2 pandemic has had a significant impact on healthcare, including eye care, worldwide. Effective and safe vaccines have been developed using both conventional and novel technologies to combat SARS-CoV-2 infection. While vaccination has been shown to be remarkably effective in reducing the spread and associated morbidity and mortality of COVID-19 disease, there have been reports of complications to the posterior segment of the eye.

METHODS

We present a case-based analysis of reported complications of COVID-19 vaccination to the posterior segment of the eye. The study aims to highlight the diversity of possible complications and discuss the plausible involved pathophysiologic mechanisms.

RESULTS

The most significant complications reported were retinal macro or microvascular occlusions, uveitis, and central serous chorioretinopathy. These complications are rare but require prompt diagnosis and management to prevent serious visual morbidity.

CONCLUSIONS

Our study highlights the need for ophthalmologists to be aware of possible complications related to COVID-19 vaccination and the importance of prompt diagnosis and management. The findings of this study may help ophthalmologists to better understand and manage these rare complications.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Background

The fast development of swept-source optical coherence tomography (SS-OCT) and swept-source optical coherence tomography angiography (SS-OCTA) enables both anterior and posterior imaging of the eye. These techniques have evolved from a research tool to an essential clinical imaging modality.

Main text

The longer wavelength and faster speed of SS-OCT and SS-OCTA facilitate better visualization of structure and vasculature below pigmented tissue with a larger field of view of the posterior segment and 360-degree visualization of the anterior segment. In the past 10 years, algorithms dealing with OCT and OCTA data also vastly improved the image quality and enabled the automated quantification of OCT- and OCTA-derived metrics. This technology has enriched our current understanding of healthy and diseased eyes. Even though the high cost of the systems currently limited the widespread use of SS-OCT and SS-OCTA at the first beginning, the gap between research and clinic practice got obviously shortened in the past few years.

Conclusions

SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift toward more widespread adoption of new imaging technology in clinical practice.

The link between Keratoconus and posterior segment parameters: An updated, comprehensive review

Keratoconus (KCN) has been typically known as a disorder with effects limited to the cornea. Because of this viewpoint, less attention has been devoted to its effects on the posterior segment structures. We aimed to provide a comprehensive review of the literature to understand the potential link between KCN and posterior segment structures and their functions. It is clear from the extensive evidence in the literature that KCN can be associated with morphological and functional changes in different parts of the posterior segment. It is worth noting that anatomical changes have been not only noted in several layers of the retina but also in the optic nerve head and the choroid. Several mechanisms have been proposed to explain this observation, including incidents induced by oxidative stress in keratoconic corneas and retinal adaptions to the distorted image that lands on the retina. Consequently, when KCN has been diagnosed, it seems practical to consider assessing the retinal and choroidal profile using optical coherence tomography and potentially functional abnormalities through electrophysiology procedures.

In vitro dissolution testing models of ocular implants for posterior segment drug delivery

The delivery of drugs to the posterior segment of the eye remains a tremendously difficult task. Prolonged treatment in conventional intravitreal therapy requires injections that are administered frequently due to the rapid clearance of the drug molecules. As an alternative, intraocular implants can offer drug release for long-term therapy. However, one of the several challenges in developing intraocular implants is selecting an appropriate in vitro dissolution testing model. In order to determine the efficacy of ocular implants in drug release, multiple in vitro test models were emerging. While these in vitro models may be used to analyse drug release profiles, the findings may not predict in vivo retinal drug exposure as this is influenced by metabolic and physiological factors. This review considers various types of in vitro test methods used to test drug release of ocular implants. Importantly, it discusses the challenges and factors that must be considered in the development and testing of the implants in an in vitro setup.

Long-acting nanoparticle-loaded bilayer microneedles for protein delivery to the posterior segment of the eye

Treatment of neovascular ocular diseases involves intravitreal injections of therapeutic proteins using conventional hypodermic needles every 4-6 weeks. Due to the chronic nature of these diseases, these injections will be administrated to patients for the rest of their lives and their frequent nature can potentially pose a risk of sight-threatening complications and poor patient compliance. Therefore, we propose to develop nanoparticle (NP)-loaded bilayer dissolving microneedle (MN) arrays, to sustain delivery of protein drugs in a minimally invasive manner. In this research, a model protein, ovalbumin (OVA)-encapsulated PLGA NPs were prepared and optimised using a water-in-oil-in-water (W/O/W) double emulsion method. The impact of stabilisers and primary sonication time on the stability of encapsulated OVA was evaluated using an enzyme-linked immunosorbent assay (ELISA). Results showed that the lower primary sonication time was capable of sustaining release (77 days at 28.5% OVA loading) and improving the OVA bioactivity. The optimised NPs were then incorporated into a polymeric matrix to fabricate bilayer MNs and specifically concentrated into MN tips by high-speed centrifugation. Optimised bilayer MNs exhibited good mechanical and insertion properties and rapid dissolution kinetics (less than 3 min) in excised porcine sclera. Importantly, ex vivo transscleral distribution studies conducted using a multiphoton microscope confirmed the important function of MN arrays in the localisation of proteins and NPs in the scleral tissue. Furthermore, the polymers selected to prepare bilayer MNs and OVA NPs were determined to be biocompatible with retinal cells (ARPE-19). This delivery approach could potentially sustain the release of encapsulated proteins for more than two months and effectively bypass the scleral barrier, leading to a promising therapy for treating neovascular ocular diseases.

Clinical outcomes of posterior segment intraocular foreign bodies: The volume effect

PURPOSE

To assess the effect of foreign body volume on visual and anatomic outcomes in patients with a posterior segment intraocular foreign body (IOFB).

METHODS

Patients were divided into three groups according to the volume of the IOFB; group 1 (n=18 eyes) with IOFBs<2mm³, group 2 (n=15 eyes) with 2mm³≤IOFBs<6mm³, group 3 (n=18 eyes) with IOFBs≥6mm³. All eyes underwent pars plana vitrectomy (PPV) for removal of the IOFB. Demographic characteristics, features of the injury and IOFB, findings of the initial and final ophthalmological examinations, and timing of IOFB removal were studied.

RESULTS

The mean age was 38.8±12.0years, and the median follow-up period was 12.0 (range: 6-98) months. Initial visual acuity (VA) was significantly lower in group 3 (P=0.005), while final VA was similar between the three subgroups. Frequencies of primary globe repair, initial vitreous hemorrhage (VH), corneoscleral entry, and IOFB removal through the cornea were significantly higher in eyes with large volume IOFBs (P<0.05). Siderosis was only seen in 4 patients in group 1 (22.2%). No patients developed postoperative endophthalmitis.

CONCLUSION

Large volume posterior segment IOFBs are associated with poor initial VA, initial VH and corneoscleral injury. Nevertheless, PPV and IOFB extraction under favorable conditions may provide significant visual improvement in eyes with large volume IOFBs.

Antimicrobial guide to posterior segment infections

PURPOSE

This review article is meant to serve as a reference guide and to assist the treating physician in making an appropriate selection and duration of an antimicrobial agent.

METHODS

Literature review.

RESULTS

Infections of the posterior segment require prompt medical or surgical therapy to reduce the risk of permanent vision loss. While numerous options exist to treat these infections, doses and alternative therapies, especially with contraindications for first-line therapy, are often elusive. Antimicrobial agents to treat posterior segment infections can be administered via various routes, including topical, intravitreal, intravenous, and oral.

CONCLUSIONS

Although there are many excellent review articles on the management of endophthalmitis, we take the opportunity in this review to comprehensively summarize the appropriate antimicrobial regimen of both common and rare infectious etiologies of the posterior segment, using evidence from clinical trials and large case series.

Surgical outcomes of the removal of posterior segment metallic intraocular foreign bodies

BACKGROUND

Posterior segment metallic intraocular foreign bodies (IOFBs) are a leading cause of visual morbidity and blindness, especially among young and middle-aged working populations. Here, we aimed to evaluate the surgical outcomes of the removal of such IOFBs that result from injuries.

METHODS

In this retrospective study, 39 patients injured by metallic posterior segment IOFBs and who underwent primary repair procedures, vitrectomies, and IOFBs removal with or without procedures for traumatic cataract removal, scleral buckling and intraoperative tamponade application from January, 2008 to January, 2019. We analyzed the preoperative, intraoperative and postoperative related factors that affect the final visual outcomes.

RESULTS

The mean age of the 39 patients was 40.51 ± 12.48 years with the male being predominent (100%).The mean preoperative vision measured 1.50 [Snellen Equivalent (SE), 20/645] ± 1.12 logMAR with the mean final vision measuring 0.93 (SE, 20/172) ± 1.09 logMAR. The related factors that were determined to affect the final visual outcomes included preoperative vision (P = 0.025), IOFB-related macula injuries (P = 0.001) and the development of postoperative complications (P = 0.005) especially retinal detachment (P = 0.002) with the mean final vision measuring 2.12 (SE, counting finger to hand motion) ±1.23 logMAR. Concerning the preoperative signs, the patients with preoperative endophthalmitis also obtained poor mean final vision measuring 1.30 (SE,20/400) ± 1.40 logMAR.

CONCLUSION

IOFB-related macula injuries and postoperative retinal detachment were important related factors of poor final visual prognoses in cases involving posterior segment metallic IOFBs. Removing IOFB as early as possible may prevent preoperative endophthalmitis which could lead poor final visions even without significance.

Efficacy and safety of injecting increasing volumes into the extravascular spaces of the choroid using a blunt adjustable depth injector

PURPOSE

To evaluate the efficacy and safety of injecting increasing volumes into the extravascular spaces of the choroid (EVSC) in rabbit eyes in vivo using a blunt adjustable depth injector.

METHODS

Indocyanine green (ICG) was injected in the superior-temporal quadrant, 2 mm posterior to the limbus at increasing volumes (0.1-0.3 ml) into the EVSC of New Zealand rabbit eyes in vivo. Intraocular pressure (IOP) measurements, spectral domain optical coherence tomography (SD-OCT), fundus imaging and histology analysis were performed to assess the safety and efficacy of the injection.

RESULTS

Volumes up to 0.3 ml were administered consistently. ICG injection was successfully monitored in vivo using infrared fundus imaging and SD-OCT. ICG was detected across the EVSC compartment, reaching the retinal pigment epithelium, optic nerve head and visual streak. Injection of 0.3 ml yielded maximal dye distribution with a coverage area of 61.8% ± 6.7% (mean ± standard error, SE) of the posterior segment. Maximal IOP elevation was recorded 5 min following injection of 0.2 and 0.3 ml ICG (+ 20.0 mmHg, + 19.4 mmHg, respectively). Twenty minutes post-injection, the IOP was < 15 mmHg in all injection volumes. No retinal detachment or hemorrhages were detected in any of the injected eyes.

CONCLUSIONS

This study demonstrates consistent and safe delivery of large volumes within the EVSC using a blunt adjustable depth injector that distributes the dye over 60% of the retinal surface. This injection system may offer a minimally invasive and easy way to deliver large volumes of pharmaceuticals into the posterior segment.

Extended release of dexamethasone from oleogel based rods

HYPOTHESIS

Topical and systemic methods are not able to deliver ophthalmic drugs for treatment of retinal diseases. Consequently, invasive monthly intravitreal injections through the eyeball are required to deliver retinal drugs. A reduction in the frequency of the injection through extended release of the drugs could have significant clinical benefits.

EXPERIMENTS

Oleogels containing ethyl cellulose as the gelator at 10% (wt%) in soybean oil were loaded with dexamethasone above the solubility limit and expunged from a syringe to create cylindrical rods for extended drug delivery. The devices were imaged to explore particle distribution and drug release was measured under sink conditions in buffer. A model was developed and fitted to data to determine effective drug diffusivity.

FINDINGS

Dexamethasone is released slowly due to the presence of the drug particles that serve as drug depots. The release increases from 600 to 3000 h as the drug loading is increased from 3% to 28%. The release profiles can be modeled by considering drug dissolution and diffusion, as well as the tortuosity of the matrix due to the presence of the voids formed after the drug particles have dissolved. The proposed approach is promising as the release profiles of the drug are comparable to commercial devices.

Posterior segment eye lesions: prevalence and associations with ocular and systemic parameters: results from the Gutenberg Health Study

BACKGROUND

To estimate the prevalence of posterior segment eye lesions and to identify their ocular and systemic associations within the Gutenberg Health Study (GHS) in Germany.

METHODS

Assessment and grading of fundus images as well as physical examination and history taking were performed in the cross-sectional analysis of 15,010 subjects (aged 35-74 years) using standardised procedures to determine the prevalence and associations of various posterior segment eye lesions.

RESULTS

Fundus photographs of both eyes were available for 12,782 (85.2%; 50% female) subjects. The prevalence weighted to the region of Mainz and Mainz-Bingen in Germany was for choroidal nevi 2.4%, drusen of the optic nerve head 0.2%, tilted discs 1.5%, chorioretinal scars suggestive of toxoplasmosis 0.2%, retinitis pigmentosa 0.04% and persistent hyaloid artery 0.02%. Choroidal nevi were positively associated with a history of myocardial infarction (OR = 2.7, 95% confidence interval 1.2-6.2, p value = 0.017). Tilted discs were positively associated with increased intraocular pressure (OR = 1.09 per mm Hg (1.02-1.16), p = 0.011) and negatively associated with smoking (OR 0.4 (0.3-0.7), p = 0.0022). Participants with tilted discs had a mean spherical equivalent of - 3.6 dioptres (standard deviation 4.0) compared with - 0.4 dioptres (2.4) to those without.

CONCLUSION

Our study is-to the best of our knowledge-the first to determine the prevalence of drusen of optic nerve head among Caucasians, to show a positive association between tilted discs and increased intraocular pressure and questions a possible link between choroidal nevi and myocardial infarction. It also showed that participants with tilted discs had a lower mean spherical equivalent than those without.

Posterior Vitreous Detachment and the Associated Risk of Retinal Toxicity with Intravitreal Melphalan Treatment for Retinoblastoma

BACKGROUND/AIMS

The presence of a posterior vitreous detachment (PVD) may play a role in the development of severe retinal toxicity following intravitreal melphalan (IVM) injection for vitreous seeding. We aimed to evaluate the incidence of PVD in retinoblastoma eyes and its association with retinal toxicity after IVM.

METHODS

We reviewed 112 eyes of 81 retinoblastoma patients with B-scan images available for review from 2010 to 2017. A cohort with vitreous seeding treated with IVM was compared to a cohort that did not undergo injection. The primary outcome measure was the presence of PVD at diagnosis and after treatment. Secondary measures included IVM-associated retinal toxicity and other ocular complications.

RESULTS

The incidence of PVD was 20% at diagnosis, and in eyes with B-scans available both at diagnosis and after treatment 18% of eyes developed a PVD over the course of therapy, more frequently after IVM (p = 0.05). Of 34 eyes receiving IVM treatment, the incidences of posterior segment toxicity and globe salvage were similar between eyes with and without PVD (p = 0.4015 and 0.52, respectively).

CONCLUSION

In this cohort of patients, there did not appear to be an association with the presence of PVD during IVM and the development of retinal toxicity.

Ocular Drug Delivery

Although the eye is an accessible organ for direct drug application, ocular drug delivery remains a major challenge due to multiple barriers within the eye. Key barriers include static barriers imposed by the cornea, conjunctiva, and retinal pigment epithelium and dynamic barriers including tear turnover and blood and lymphatic clearance mechanisms. Systemic administration by oral and parenteral routes is limited by static blood-tissue barriers that include epithelial and endothelial layers, in addition to rapid vascular clearance mechanisms. Together, the static and dynamic barriers limit the rate and extent of drug delivery to the eye. Thus, there is an ongoing need to identify novel delivery systems and approaches to enhance and sustain ocular drug delivery. This chapter summarizes current and recent experimental approaches for drug delivery to the anterior and posterior segments of the eye.

Controlled non-invasive iontophoretic delivery of triamcinolone acetonide amino acid ester prodrugs into the posterior segment of the eye

This study investigated short duration transscleral iontophoretic delivery of four triamcinolone acetonide (TA) amino acid ester prodrugs (TA-AA) (alanine, Ala; arginine, Arg; isoleucine, Ile and lysine, Lys) using whole porcine eyes globes in vitro. Post-iontophoretic biodistribution of TA was quantified by UHPLC-MS/MS in the different ocular compartments (cornea, aqueous humor, sclera, ciliary body, choroid and retinal pigmented epithelium (RPE), neural retina and vitreous humor). Transscleral iontophoresis (3 mA/cm² for 10 min) increased total drug delivery of the TA-AA prodrugs by 14-30-fold as compared to passive diffusion. The TA-AA prodrugs had distinct biodistribution profiles - the penetration depth achieved was dependent on their physicochemical properties (e.g. lipophilicity for TA-Ile) and susceptibility to hydrolysis (e.g. TA-Arg). Intraocular drug distribution was also influenced by prodrug binding to melanin (TA-Lys). Interestingly, under conditions of equivalent charge (6 mA/cm² for 5 min vs. 1.5 mA/cm² for 20 min, i.e. 1.44 C respectively) the longer duration (20 min) at lower current density resulted in ∼6 times more TA delivery into the vitreous humor. Overall, the study provided further evidence of the potential of transscleral iontophoresis for the non-invasive treatment of posterior segment inflammatory diseases.

Laparoscopic liver resection of hepatocellular carcinoma located in unfavorable segments: a propensity score-matched analysis from the I Go MILS (Italian Group of Minimally Invasive Liver Surgery) Registry

OBJECTIVE

Laparoscopic liver resection (LLR) for Hepatocellular Carcinoma (HCC) is one of the most important indications for the minimally invasive approach. Our study aims to analyze the experience of the Italian Group of Minimally Invasive Liver Surgery with laparoscopic surgical treatment of HCC, with a focus on tumor location and how it affects morbidity and mortality.

METHODS

38 centers participated in this study; 372 cases of LLR for HCC were prospectively enrolled. Patients were divided into two groups according to the HCC nodule location. Group 1 favorable location and group 2 unfavorable location. Perioperative outcomes were compared between the two groups before and after a propensity score match (PS) 1:1.

RESULTS

Before PS in group 2 surgical time was longer; conversion rate was higher; postoperative transfusion and comprehensive complication index were also higher. PS was performed with a cohort of 298 patients (from 18 centers), with 66 and 232 patients with HCC in unfavorable and favorable locations, respectively. After PS matching, 62 patients from group 1 and group 2 each were compared. Operative and postoperative course were similar in patients with HCC in favorable and unfavorable LLR locations. Surgical margins were found to be identical before and after PS.

CONCLUSIONS

These results show that LLR in patients with HCC can be safely performed in all segments because of the extensive experience of all surgeons from multiple centers in performing traditional open liver surgery as well as laparoscopic surgery.

Ocular drug delivery targeted by iontophoresis in the suprachoroidal space using a microneedle

Treatment of many posterior-segment ocular indications would benefit from improved targeting of drug delivery to the back of the eye. Here, we propose the use of iontophoresis to direct delivery of negatively charged nanoparticles through the suprachoroidal space (SCS) toward the posterior pole of the eye. Injection of nanoparticles into the SCS of the rabbit eye ex vivo without iontophoresis led to a nanoparticle distribution mostly localized at the site of injection near the limbus and <15% of nanoparticles delivered to the most posterior region of SCS (>9 mm from the limbus). Iontophoresis using a novel microneedle-based device increased posterior targeting with >30% of nanoparticles in the most posterior region of SCS. Posterior targeting increased with increasing iontophoresis current and increasing application time up to 3 min, but further increasing to 5 min was not better, probably due to the observed collapse of the SCS within 5 min after injection ex vivo. Reversing the direction of iontophoretic flow inhibited posterior targeting, with just ~5% of nanoparticles reaching the most posterior region of SCS. In the rabbit eye in vivo, iontophoresis at 0.14 mA for 3 min after injection of a 100 μL suspension of nanoparticles resulted in ~30% of nanoparticles delivered to the most posterior region of the SCS, which was consistent with ex vivo findings. The procedure was well tolerated, with only mild, transient tissue effects at the site of injection. We conclude that iontophoresis in the SCS using a microneedle has promise as a method to target ocular drug delivery within the eye, especially toward the posterior pole.

QUIET PLEASE! Effect of distraction on simulated posterior segment surgical performance

PURPOSE

To determine the effect of distraction on posterior segment surgical performance using a virtual reality simulator in expert and novice ophthalmic surgeons.

METHODS

Twenty subjects were given 6 min to read an unpublished research paper and then were randomized into two groups. Group 1 subjects were allowed 3 min to complete a standardized vitreoretinal simulated task undistracted. Group 2 subjects were asked six questions on the research paper whilst completing the same task. Each subject then performed the alternate scenario. Finally, all participants were asked six questions on the research paper whilst not operating.

RESULTS

There was no evidence of a difference in the odometer values (p = 0.127), cognitive task score (p = 0.390) or overall surgical task scores (p = 0.113) between the two groups. The time taken by the distracted group was significantly greater (95% CI -26.03 to -1.67, t-test p = 0.028).

CONCLUSION

Distraction significantly increases the time taken to perform a simulated vitreoretinal surgical task for all grades of surgeon. More studies are required to understand the impact on different types of distraction on surgical performance.

Pharmaceutical microscale and nanoscale approaches for efficient treatment of ocular diseases

Efficient treatment of ocular diseases can be achieved thanks to the proper use of ophthalmic formulations based on emerging pharmaceutical approaches. Among them, microtechnology and nanotechnology strategies are of great interest in the development of novel drug delivery systems to be used for ocular therapy. The location of the target site in the eye as well as the ophthalmic disease will determine the route of administration (topical, intraocular, periocular, and suprachoroidal administration) and the most adequate device. In this review, we discuss the use of colloidal pharmaceutical systems (nanoparticles, liposomes, niosomes, dendrimers, and microemulsions), microparticles (microcapsules and microspheres), and hybrid systems (combination of different strategies) in the treatment of ophthalmic diseases. Emphasis has been placed in the therapeutic significance of each drug delivery system for clinical translation.

Synthetic nanocarriers for the delivery of polynucleotides to the eye

This review is a comprehensive analysis of the progress made so far on the delivery of polynucleotide-based therapeutics to the eye, using synthetic nanocarriers. Attention has been addressed to the capacity of different nanocarriers for the specific delivery of polynucleotides to both, the anterior and posterior segments of the eye, with emphasis on their ability to (i) improve the transport of polynucleotides across the different eye barriers; (ii) promote their intracellular penetration into the target cells; (iii) protect them against degradation and, (iv) deliver them in a long-term fashion way. Overall, the conclusion is that despite the advantages that nanotechnology may offer to the area of ocular polynucleotide-based therapies (especially AS-ODN and siRNA delivery), the knowledge disclosed so far is still limited. This fact underlines the necessity of more fundamental and product-oriented research for making the way of the said nanotherapies towards clinical translation.

Ocular Pharmacokinetics

Although the fundamental concepts of pharmacokinetics remain the same, ocular pharmacokinetics has its own challenges due to the uniqueness of barrier properties posed by various ocular tissues and its growing complexity with different routes of ocular administration. A thorough understanding of the barrier nature will aid in tailoring a drug or its carrier's physicochemical properties to its advantage. In order to deliver the right payload of a drug at the target site, various approaches can be taken to leverage the pharmacokinetics that includes molecular design based on desirable physicochemical properties, formulation approaches, and alternative routes of administration. In this chapter, a brief overview of the barrier properties with respect to various routes of administration is presented along with the physicochemical properties that influence the pharmacokinetics of ocular drugs. Recent advances in ocular pharmacokinetics are discussed in addition to new perspectives in interpreting existing data.

Light activated liposomes: Functionality and prospects in ocular drug delivery

Ocular drug delivery, especially to the retina and choroid, is a major challenge in drug development. Liposome technology may be useful in ophthalmology in enabling new routes of delivery, prolongation of drug action and intracellular drug delivery, but drug release from the liposomes should be controlled. For that purpose, light activation may be an approach to release drug at specified time and site in the eye. Technical advances have been made in the field of light activated drug release, particularly indocyanine green loaded liposomes are a promising approach with safe materials and effective light triggered release of small and large molecules. This review discusses the liposomal drug delivery with light activated systems in the context of ophthalmic drug delivery challenges.

Graft harvest of right posterior segment for living-donor liver transplantation

INTRODUCTION

Right posterior segmental graft (RPSG) is an alternative procedure for living-donor liver transplantation (LDLT). Although the first case of RPSG was reported in 2001, it has not been disseminated because of the lack of popularity, technical concerns, and surgical difficulties.

PRESENTATION OF CASE

A 37-year-old man with primary sclerosing cholangitis. His spouse was the only transplantation candidate, although she was ABO incompatible. Preoperative investigations revealed that left-lobe graft was insufficient for the recipient and that right-lobe graft was accompanied by donor risk. In RPSG, estimated graft-to-recipient weight ratio (GRWR) and estimated ratio of liver remnant were reasonable. In the donor operation, the right hepatic vein (RHV) and demarcation line were confirmed, and intraoperative cholangiography was performed. The cut line was carefully considered based on the demarcation line and RHV. The RPSG was harvested. Actual GRWR was 0.54. Unfortunately, this recipient showed a poor course and outcome after LDLT.

DISCUSSION

Segmental branches of vessels and biliary duct may be not suitable for reconstruction, and surgeons must exercise some ingenuity in the recipient operation. Segmental territory based on inflow and that based on outflow never overlap completely, even in the same segment. The selection of RPSG based only on liver volume may be unfeasible. Liver resection should be carefully considered based on preoperative imaging, and demarcation line and RHV during surgery.

CONCLUSION

RPSG is a useful tool for LDLT. However, detailed studies before surgery and careful consideration during surgery are important for RPSG harvest.

Medial extrusion of the posterior segment of medial meniscus is a sensitive sign for posterior horn tears

BACKGROUND

To evaluate medial extrusion of the posterior segment of the medial meniscus in posterior horn tears.

METHODS

This study enrolled 72 patients without medial meniscal tears (group N), 72 patients with medial meniscal tears without posterior horn tears (group PH-), 44 patients with posterior horn tears of the medial meniscus (group PH+). All meniscal tears were confirmed by arthroscopy. Medial extrusion of the middle segment and the posterior segment was measured on coronal MRIs.

RESULTS

Extrusions of both middle and posterior segments in groups PH- and PH+ (middle segment; 2.94±1.51 mm for group PH- and 3.75±1.69 mm for group PH+, posterior segment; 1.85±1.82 mm for group PH- and 4.59±2.74 mm for group PH+) were significantly larger than those in group N (middle segment; 2.04±1.20, posterior segment; 1.21±1.86). Both indicators of extrusion in group PH+ were larger than those in group PH-. In the early OA category, neither middle nor posterior segment in group PH- extruded more than in group N. However, only the posterior segment in group PH+ extruded significantly more than in group N. Multiple lineal regression analyses revealed that posterior segment extrusion was strongly correlated with the posterior horn tears (p<0.001) among groups PH- and PH+.

CONCLUSION

The newly presented indicator for extrusion of the posterior segment of the medial meniscus is associated with posterior horn tears in comparison with the extrusion of the middle segment, especially in the early stages of osteoarthritis.

LEVEL OF EVIDENCE

Level II--Diagnostic Study.

Drug delivery to the ocular posterior segment using lipid emulsion via eye drop administration: effect of emulsion formulations and surface modification

This work explored submicron-sized lipid emulsion as potential carriers for intraocular drug delivery to the posterior segment via eye drops. The effects of physicochemical properties of lipid emulsion on drug delivery were evaluated in vivo using mice. Different formulations of submicron-sized lipid emulsions were prepared using a high pressure homogenization system. Using coumairn-6 as a model drug and fluorescent marker, fluorescence could be observed in the retina after administration of the lipid emulsion. The fluorescence intensity observed after administration of medium chain triglycerides containing the same amount of coumarin-6 was much lower than that observed after administration of lipid emulsions. The inner oil property and phospholipid emulsifier did not affect the drug delivery efficiency to the retina. However, compared with unmodified emulsions, the fluorescence intensity in the retina increased by surface modification using a positive charge inducer and the functional polymers chitosan (CS) and poloxamer 407 (P407). CS-modified lipid emulsions could be electrostatically interacted with the eye surface. By its adhesive property, poloxamer 407, a surface modifier, possibly increased the lipid emulsion retention time on the eye surface. In conclusion, we suggested that surface-modified lipid emulsions could be promising vehicles of hydrophobic drug delivery to the ocular posterior segment.

Utility of transporter/receptor(s) in drug delivery to the eye

The eye is a highly protected organ, and designing an effective therapy is often considered a challenging task. The anatomical and physiological barriers result in low ocular bioavailability of drugs. Due to these constraints, less than 5% of the administered dose is absorbed from the conventional ophthalmic dosage forms. Further, physicochemical properties such as lipophilicity, molecular weight and charge modulate the permeability of drug molecules. Vision-threatening diseases such as glaucoma, diabetic macular edema, cataract, wet and dry age-related macular degeneration, proliferative vitreoretinopathy, uveitis, and cytomegalovirus retinitis alter the pathophysiological and molecular mechanisms. Understanding these mechanisms may result in the development of novel treatment modalities. Recently, transporter/receptor targeted prodrug approach has generated significant interest in ocular drug delivery. These transporters and receptors are involved in the transport of essential nutrients, vitamins, and xenobiotics across biological membranes. Several influx transporters (peptides, amino acids, glucose, lactate and nucleosides/nucleobases) and receptors (folate and biotin) have been identified on conjunctiva, cornea, and retina. Structural and functional delineation of these transporters will enable more drugs targeting the posterior segment to be successfully delivered topically. Prodrug derivatization targeting transporters and receptors expressed on ocular tissues has been the subject of intense research. Several prodrugs have been designed to target these transporters and enhance the absorption of poorly permeating parent drug. Moreover, this approach might be used in gene delivery to modify cellular function and membrane receptors. This review provides comprehensive information on ocular drug delivery, with special emphasis on the use of transporters and receptors to improve drug bioavailability.

Ultrasonographic findings in patients examined in cataract detection-and-treatment campaigns: a retrospective study

INTRODUCTION

A cataract is defined as an opacity of any portion of the lens, regardless of visual acuity. In some advanced cases of cataracts, in which good fundus visualization is not possible, an ultrasound examination provides better assessment of the posterior segment of the globe.

OBJECTIVES

This study aims to evaluate the ultrasonographic records of patients with advanced cataracts who were examined during cataract campaigns.

METHODS

The ultrasonographic findings obtained from 215 patients examined in cataract campaigns conducted by the Hospital das Clínicas Department of Ophthalmology of the Faculdade de Medicina da Universidade de São Paulo between the years of 2005 and 2007 were evaluated, and the utility of this exam in changing the treatment procedures was studied.

RESULTS

A total of 289 eyes from 215 patients were examined. Of the eyes examined, 77.5% presented with findings in the vitreous cavity and the posterior pole. A posterior vitreous detachment with no other complications was observed in 47.4% of the eyes. The remaining 30.1% presented with eye diseases that could result in a reduced visual function after surgery. The most frequent eye diseases observed were diffuse vitreous opacity (12.1% of the eyes) and detachment of the retina (9.3% of the eyes).

DISCUSSION

In many cases, the ultrasonographic evaluation of the posterior segment revealed significant anomalies that changed the original treatment plan or contra-indicated surgery. At the very least, the evaluation was useful for patient counseling.

CONCLUSION

The ultrasonographic examination revealed and differentiated between eyes with cataracts and eyes with ocular abnormalities other than cataracts as the cause of poor vision, thereby indicating the importance of its use during ocular evaluation.