Permeability of the Retina and RPE-Choroid-Sclera to Three Ophthalmic Drugs and the Associated Factors

Topical brimonidine induced acute uveal effusion in a patient with nanophthalmos: a case report

BACKGROUND

We report a case of uveal effusion in a nanophthalmic eye after topical use of brimonidine.

CASE PRESENTATION

A 42-year-old male patient with nanophthalmos experienced sudden blurred vision in the right eye after using topical brimonidine when picking up tennis balls repeatedly 6 weeks after bilateral YAG peripheral iridotomy. Ocular examination showed wide choroidal and exudative retinal detachment in the temporal and inferior region, involving the macula. Acute uveal effusion in the right, bilateral nanophthalmos was diagnosed. Oral and topical corticosteroids, combined with topical nonsteroids and atropine led to a complete resolution of the uveal effusion after one month.

CONCLUSION

This case suggested a possible causal relationship between the topical use of brimonidine and acute uveal effusion in patients with nanophthalmos. Topical brimonidine should be used with caution in nanophthalmic eyes.

Optical coherence tomography findings in fungal uveitis

PURPOSE

The purpose of the study was to describe the vitreal, retinal, and choroidal features of eyes affected by endogenous endophthalmitis (EE) and evaluate the effects of systemic antifungal drug treatment and pars plana vitrectomy by using spectral domain optical coherence tomography (SD-OCT).

METHODS

Medical records and SD-OCT images of eyes diagnosed with EE at a single uveitis tertiary referral center in Brazil were acquired at the time of diagnosis, after 7 days of high-dose antifungal drug treatment, and at follow-up assessments performed 30 days after resolution.

RESULTS

Thirteen eyes were enrolled in the study. All patients showed hyperreflective round-shaped lesions on SD-OCT and pre-retinal aggregates. Five eyes responded to antifungal systemic oral drugs despite showing vitreous opacity. The response to treatment was observable on optical coherence tomography (OCT) images.

CONCLUSION

Fungal endophthalmitis showed typical features on SD-OCT, facilitating early diagnosis and treatment despite the absence of vitreous culture or biopsy. This study suggests that OCT images can be used to support diagnosis by physicians who do not have access to vitreoretinal surgery.

A Physiology-Based Mathematical Model to Understand Drug Delivery from Contact Lenses to the Back of the Eye

OBJECTIVE

Therapeutic contact lenses, able to store drug and deliver it to the eye surface in a sustained fashion, gained interest as an effective and patient-friendly alternative to eye drops. Recent animal studies also demonstrated the presence of therapeutic drug levels in the back of the eye after wearing drug-loaded contact lenses, thus opening the possibility of treating the posterior segment without need of invasive intraocular injections. The drug pathways from contact lenses to the back of the eye require further investigation.

METHODS

A mechanistic mathematical model was developed to evaluate the drug concentration over time in the tears, sclera and choroid, retina, aqueous humor and vitreous humor after the application of a therapeutic contact lens. The main drug transport mechanisms of the eye and the barrier properties of the different tissues were included in the model. Validation was performed by comparison with experimental data in literature.

RESULTS

The model predictions of drug concentration over time reflected the experimental data both in the anterior and posterior segment of the eye. The model can differentiate between contributions to transport from different pathways.

CONCLUSIONS

The model constitutes a first step towards the possibility of predicting the ocular drug distribution and the treatment efficacy in the early stage of contact lens development, and it may help reduce both the need for in vivo tests (with ethical and economic advantages) and the gap between the lens design and clinical application. It also allows for an improved understanding of drug transport in the eye.

Preparation and Characterization of Ion-Sensitive Brimonidine Tartrate In Situ Gel for Ocular Delivery

Brimonidine tartrate (BRT) is a highly selective α2 adrenergic receptor agonist as treatment for patients with open angle glaucoma and high intraocular pressure. The objective of this study was to formulate an ophthalmic ion-sensitive in situ gel (ISG) of BRT to increase the retention time of the drug and its bioavailability. The optimum formulation of 2 mg/mL BRT-ISG was obtained with 0.45% gellan gum as the gel matrix. In vitro release results showed that the water-soluble drug bromonidine tartrate in ocular in situ gels exhibited a high burst effect and fast release in solution. The results of dialysis membrane permeation showed that there was a significant difference between the commercially available and BRT-ISG groups after 45 min. The results of the pre-corneal retention study indicated that gellan gum can effectively prolong ocular surface retention. Preliminary stability results showed that it should be stored in a cool and dark place, and the formulation under long-term preservation can be basically stable. The pharmacokinetic study of the BRT-ISG in the anterior chamber of the rabbit eye was studied by microdialysis technique, and microdialysis samples were analyzed by LC-MS/MS. The pharmacokinetic study showed that the BRT-ISG reached Cmax (8.16 mg/L) at 93 min after administration, which was 2.7 times that of the BRT eye drops, and the AUC(0-t) (1397.08 mg·min/L) was 3.4 times that of the BRT eye drops. The optimal prescription can prolong the retention time of BRT in front of the cornea and significantly improve the bioavailability of BRT in the eye. Combined with the results of in vitro release, permeation and pre-corneal retention studies, the improvement of BRT-ISG bioavailability in rabbit eyes was found to be mainly due to the retention effect after the mixture of ISG and tears.

Feasibility of Therapeutic Ultrasound Application in Topical Scleral Delivery of Avastin

Purpose

Macromolecules have been shown to be effective in vision-saving treatments for various ocular diseases, such as age-related macular degeneration and diabetic retinopathy. The current delivery of macromolecules requires frequent intraocular injections and carries a risk of serious adverse effects.

Methods

We tested the application of therapeutic ultrasound as a minimally invasive approach for the delivery of Avastin into the diseased regions of the eye. Avastin (bevacizumab) is an anti-vascular endothelial growth factor (VEGF) antibody with a molecular weight of 149 kDa. We tested the effectiveness and safety of Avastin delivery through rabbit sclera in vitro using a standard diffusion cell model. Ultrasound at frequencies of 400 kHz or 3 MHz with an intensity of 1 W/cm2 was applied for the first 5 minutes of 1-hour drug exposure. Sham treatments mimicked the ultrasound treatments, but ultrasound was not turned on. Absorbance measurements of the receiver compartment solution were performed at 280 nm using a spectrophotometer.

Results

Absorbance measurements indicated no statistical difference between the sham (n = 13) and 400 kHz ultrasound group (n = 15) in the delivery of Avastin through the sclera. However, the absorbance values were statistically different (P < 0.01) between the 3 MHz ultrasound group (0.004, n = 8) and the matched sham group (0.002, n = 7). There was 2.3 times increase in drug delivery in the 3 MHz ultrasound when compared to the corresponding sham group. Histological studies indicated no significant damage in the ultrasound-treated sclera due to ultrasound application.

Conclusions

Our preliminary results provided support that therapeutic ultrasound may be effective in the delivery of Avastin through the sclera.

Translational Relevance

Our study offers clinical potential for a minimally invasive retinopathy treatment.