Systemic antiviral drugs used in ophthalmology

Diagnostic and therapeutic challenges in acute retinal necrosis; an update

Acute retinal necrosis (ARN) is a rare but severe ophthalmic pathology defined by panuveitis, retinal necrosis, and high rates of retinal detachment. ARN may lead to poor visual outcomes even if promptly diagnosed and treated. ARN may present with a wide spectrum of clinical findings compatible with panuveitis including anterior uveitis, scleritis, vitritis, necrotizing retinitis, occlusive vasculitis, and optic disc edema. The American Uveitis Society introduced clinical criteria in 1994 for the diagnosis of ARN, while more recent criteria have been proposed by the Standardization of Uveitis Nomenclature (SUN) Working Group and the Japanese ARN Study Group. Multimodal imaging is a valuable tool in evaluating patients with ARN, particularly in unusual cases, while utilizing retinal imaging and applying AI algorithms in these areas of clinical research could be highly beneficial. Over the last few years, significant progress has been made in achieving timely diagnosis and treatment. The precise identification of the viral cause in suspected ARN cases has been greatly enhanced by the advancements in PCR techniques and flow cytometry used for intraocular fluids. systemic (intravenous or oral) antivirals with adjunctive intravitreal antiviral therapy are recommended as first-line therapy to reduce disease severity, the risk of vision loss, and retinal detachment incidence. Although aciclovir was the first existing antiviral agent, at present many clinicians prefer high-dose valaciclovir orally or intravenous aciclovir combined with intravitreal foscarnet. Despite significant progress in diagnosing and treating ARN, further research is needed to improve visual outcomes in this challenging clinical condition.

Voltammetric Pathways for the Analysis of Ophthalmic Drugs

Background:

This review investigates the ophthalmic drugs that have been studied with voltammetry in the web of science database in the last 10 years.

Introduction:

Ophthalmic drugs are used in the diagnosis, evaluation and treatment of various ophthalmological diseases and conditions. A significant literature has emerged in recent years that investigates determination of these active compounds via electroanalytical methods, particularly voltammetry. Low cost, rapid determination, high availability, efficient sensitivity and simple application make voltammetry one of the most used methods for determining various kinds of drugs including ophthalmic ones.

Methods:

In this particular review, we searched the literature via the web of science database for ophthalmic drugs which are investigated with voltammetric techniques using the keywords of voltammetry, electrochemistry, determination and electroanalytical methods.

Results:

We found 33 types of pharmaceuticals in nearly 140 articles. We grouped them clinically into seven major groups as antibiotics, antivirals, non-steroidal anti-inflammatory drugs, anti-glaucomatous drugs, steroidal drugs, local anesthetics and miscellaneous. Voltammetric techniques, electrodes, optimum pHs, peak potentials, limit of detection values, limit of quantification values, linearity ranges, sample type and interference effects were compared.

Conclusion:

Ophthalmic drugs are widely used in the clinic and it is important to determine trace amounts of these species analytically. Voltammetry is a preferred method for its ease of use, high sensitivity, low cost, and high availability for the determination of ophthalmic drugs as well as many other medical drugs. The low limits of detection values indicate that voltammetry is quite sufficient for determining ophthalmic drugs in many media such as human serum, urine and ophthalmic eye drops.

Chitosan grafted-poly(ethylene glycol) methacrylate nanoparticles as carrier for controlled release of bevacizumab

The aim of the present study is to obtain, for the first time, polymeric nanocarriers based on the chitosan grafted-poly(ethylene glycol) methacrylate derivative. The strategy involves the use of chitosan grafted-poly(ethylene glycol) methacrylate with high solubility in water, obtained via Michael addition, in order to prepare potentially non-toxic micro/nanoparticles (MNPs). By modifying chitosan, its solubility in aqueous media was improved. Micro/nanoparticles-based chitosan grafted-poly(ethylene glycol) methacrylate were obtained under mild condition, with good and controlled swelling properties in acetate buffer solution (ABS) and phosphate buffer solution (PBS). The technique selected for the preparation of the MNPs was a double crosslinking (ionic and covalent) process in reverse emulsion which provide the mechanical stability of the polymeric nanocarrier. The chitosan derivative and MNPs were thoroughly characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM). The Scanning Electron Microscopy photographs revealed that prepared MNPs have different diameters depending on the used stirring rate and polymer concentration. Nanoparticles potential as drug delivery system was analyzed by loading bevacizumab (BEV) a full-length monoclonal antibody. Also, the prepared particles were found suitable from the cytotoxicity and hemocompatibility point of view enabling their potential use as delivery system for the treatment of posterior segment of the eye conditions.

Intravitreal and Systemic Foscarnet in the Treatment of Aids-Related Cmv Retinitis

Cytomegalovirus retinitis is the most frequent ocular opportunistic infection in AIDS patients. Untreated, it is always a progressive and destructive disease of the retina that results in blindness. Specific treatment is therefore mandatory to halt the progression of the retinal lesions. The authors report their experience in the treatment of CMV retinitis with foscarnet in 25 AIDS patients; the drug is an analog of pyrophosphate, virostatic against all herpes-class viruses including CMV. Foscarnet was successful in halting the progression of CMV retinitis during induction treatment (180 mg/kg/day) by either a TID (three times a day) or a BID (twice a day) regimen, and in healing retinal lesions during maintenance (90 mg/kg/day) in 14 out of 19 patients. Five patients had a relapse of retinitis during maintenance. In these patients a brief course of intravitreal foscarnet, in association with the lowest dosage of the drug administered systematically (90 mg/kg/day), was effective in healing the retinal lesions. The main systemic side effects, such as renal impairment and electrolytic disturbances, were observed only during the induction treatment, and only in one case was it necessary to stop the therapy.

Focal posterior pole viral retinitis

PURPOSE

To describe the clinical features of an atypical form of viral retinitis in immunocompetent patients.

METHODS

This was a retrospective noncomparative case series. The charts of 8 patients diagnosed with and treated for focal posterior viral retinitis were reviewed. Clinical and demographic features were evaluated. All the patients had extensive laboratory tests, fundus fluorescein angiography, optical coherence tomography of macula, and polymerase chain reaction of vitreous.

RESULTS

All the patients were referred to our Uveitis Service from other hospitals, as their uveitis symptoms deteriorated in spite of treatment. The mean age of 4 male and 4 female patients was 32.1 years (range, 22-42 years). The mean follow-up period was 10 months (range, 6-18 months). All of the patients had unilateral disease. Polymerase chain reaction analysis of vitreous specimen was positive for herpes simplex virus-1 in 5 patients and varicella zoster virus in 3 patients. Retinitis resolved after systemic acyclovir treatment in all patients.

CONCLUSIONS

Viral etiology must be borne in mind in the differential diagnosis of atypical retinitis. It can be a milder form of viral retinitis like focal viral retinitis, as mentioned in this study. The prognosis of this disease is better than the other forms of necrotizing retinopathies involving a larger area of retina.

Vitreous penetration of orally administered famciclovir

PURPOSE

To determine the vitreous penetration of penciclovir (Denavir; GlaxoSmithKline, Philadelphia, Pennsylvania, USA) after oral administration of the prodrug famciclovir (Famvir; Novartis Pharmaceuticals Corp, East Hanover, New Jersey, USA).

DESIGN

Prospective interventional case series.

METHODS

Ten patients undergoing elective pars plana vitrectomy at a single institution were enrolled to take 3 oral doses of famciclovir 500 mg the day preceding surgery and a fourth dose on the morning of surgery. Blood and undiluted vitreous samples were acquired from each patient during surgery. High-performance liquid chromatography was used to determine the concentration of penciclovir in each sample. Exclusion criteria included prior vitrectomy, compromised blood-retina barrier, renal or hepatic disease, human immunodeficiency virus infection, bone marrow or renal transplantation, pregnancy or breastfeeding, history of adverse reaction or allergy to famciclovir or penciclovir, and antiviral, probenecid, or cimetidine use within 1 month of surgery.

RESULTS

Ten eyes of 10 patients ranging in age from 26 to 82 were included. All patients had normal renal and hepatic function as determined by history and laboratory values. Mean serum penciclovir concentration +/- standard deviation was 4.45 +/- 1.31 microg/ml (range, 2.51 to 6.34 microg/ml). Mean vitreous penciclovir concentration was 1.21 +/- 0.38 microg/ml (range, 0.39 to 1.88 microg/ml). Mean vitreous-to-serum concentration ratio of penciclovir was 0.28 +/- 0.09 (range, 0.16 to 0.41).

CONCLUSIONS

Oral administration of famciclovir results in vitreous concentrations of penciclovir within the inhibitory ranges for herpes simplex 1, herpes simplex 2, and varicella zoster virus. Oral famciclovir may be a reasonable alternative to intravenous acyclovir (Zovirax; GlaxoSmithKline) in the treatment of acute retinal necrosis, especially in cases of acyclovir resistance or patient inability to tolerate prolonged intravenous treatment.

[The latest in herpes simplex keratitis therapy]

Herpetic keratitis is characterized by spontaneous recurrences and a risk of vision loss, the latter being more serious when relapses are frequent and severe. Two clinical forms are commonly distinguished: epithelial keratitis, usually quickly resolved with topical antivirals, and stromal keratitis, which has a slower progression, even when both steroids and antivirals are used. Great strides have been made during the last 20 Years in the therapy of herpes keratitis, which is now considered and treated as a chronic disease. Randomized controlled studies definitively showed the decrease in spontaneous herpetic ocular events in patients treated with long-term oral acyclovir. The effectiveness of preventive treatment has also been shown during high-risk periods, especially ocular surgery, in patients with a history of herpes keratitis. However, the optimal duration and dosage of antiviral prevention have yet to be defined. We can also hope that in the future novel antiviral strategies such as vaccination will reduce the place of herpes keratitis as an indication for corneal graft.

Antiviral therapy for ocular viral disease

Ophthalmic manifestations of viral disease are commonly encountered in veterinary practice. Although the number of antiviral agents is rapidly increasing, the efficacy of many of these drugs against animal viral pathogens may not be known. Furthermore, some of these newer medications may, in fact. be toxic to animal patients. Continued research on the efficacy of these medications in treating viral diseases of veterinary importance is warranted.A thorough review of the ever-growing body of literature is imperative before instituting any new or unknown antiviral therapy. At this time, feline HSV-1 infections remain the most well understood of the ocular viral infections that veterinary practitioners may be called on to treat. Ironically, the number of antiviral agents proven to be effective in naturally occurring clinical cases of FHV-I remains quite limited. With new medications being investigated, this paucity of information on efficacious antiviral therapeutic agents will hopefully improve.

Polymerase chain reaction as a rapid diagnostic tool for therapy of acute retinal necrosis syndrome

Herpesviruses are involved in the pathogenesis of acute retinal necrosis syndrome (ARN). A rapid and accurate diagnosis of herpetic infections is crucial for prompt administration of a specific antiviral therapy. The purpose of this study was to evaluate a polymerase chain reaction (PCR)-based assay to detect herpesvirus DNA in the aqueous humor of clinical samples from ten patients with uveitis and clinical suspicion of ARN. Samples were assayed for herpes simplex virus type 1-2 (HSV 1-2), varicella zoster virus (VZV) and cytomegalovirus (CMV). Clinical suspicion of ARN was confirmed for four patients. Two patients (one with bilateral ARN) tested PCR-positive for VZV DNA and the other two were positive for HSV 1-2 DNA. CMV DNA was not detected in any of the samples, and no sample was positive for DNA from more than one virus. The remaining patients did not show any evidence of herpesvirus DNA in their aqueous samples. Our findings demonstrate that the use of PCR for detecting herpesvirus DNA in aqueous humor of uveitic subjects may be a valuable tool for early diagnosis of acute retinal necrosis syndrome and for timely administration of a suitable therapy.

Efficacy of polyclonal antibodies for treatment of ocular herpes simplex infection

PURPOSE

Herpes simplex virus (HSV) can cause corneal infections in humans and lead to permanent scarring, loss of vision, and blindness. Current treatment of epithelial HSV keratitis consists of using antiviral DNA analogs. In this study, we used in vitro and in vivo models to evaluate the efficacy of six polyclonal antibodies to HSV recombinant surface glycoprotein D in treating ocular epithelial HSV.

METHODS

Confluent cultures of African Green monkey kidney fibroblasts (Vero cells) and normal 3-to 5-lb female New Zealand White rabbits were infected with HSV type 1, strain RE. In vitro virucidal and antiviral assays were performed, and the best of the compounds was chosen for the in vivo stage. Animals were carefully monitored until day 5 after HSV-1 inoculation, then arbitrarily divided into groups receiving, for 14 days, varying doses of: polyclonal antibodies four times a day, polyclonal antibodies three times a day, trifluorothymidine (current treatment of choice and the positive control) nine times a day, or 0.9% physiologic saline nine times a day. The animals were followed up in a masked fashion and carefully monitored for severity and resolution of the HSV infection by biomicroscopy (slit lamp) examination and viral cultures using standardized plaque assays.

RESULTS

All six of the compounds tested were effective in vitro, but one compound in particular, SP-510-50, was superior. It was used for the in vivo testing and showed antiviral efficacy in a dose-dependent manner, and at dosing four times a day, it was of comparable efficacy to trifluorothymidine (nine times a day).

CONCLUSIONS

We conclude that polyclonal antibodies to glycoprotein D appear to be effective antiviral agents in vitro and in vivo in a rabbit model of HSV-1 keratitis and show promise as a new antiviral treatment for ophthalmic use.

Changing therapeutic paradigms in CMV retinitis in AIDS

Cytomegalovirus (CMV) retinitis is a common ocular complication of immunosuppression. The management of CMV retinitis has been continuously evolving over the last decade. The mainstay of therapy remains ganciclovir and foscarnet. However, increasing resistance and ongoing toxicities to these agents remain a challenge. Additional frequently utilised agents include cidofovir and fomivirsen. The advent of highly active antiretroviral therapy (HAART) has allowed the restoration of immunocompetency to many patients previously challenged by CMV infection. In some circumstances, HAART has even eliminated the need for ongoing antiviral therapy. This paper reviews the current treatment modalities, including their toxicities and dosing recommendations.

Diagnostic anterior chamber paracentesis in uveitis: a safe procedure?

BACKGROUND

Differentiation between infectious and non-infectious uveitis is of crucial value for accurate management of patients with uveitis. Tests performed on aqueous humour yield more relevant information than those done in serum. The objective of this study was to evaluate whether the aqueous humour tap for diagnostic purposes is a safe procedure to perform in uveitis patients.

METHODS

In this retrospective study 361 patients with uveitis, who underwent a diagnostic anterior chamber paracentesis in an outpatient clinic, were investigated. 72 of the 361 patients were examined 30 minutes after the puncture. The site of the paracentesis, the depth of the anterior chamber, and cells in the anterior chamber were examined. All 361 patients were evaluated within 2 weeks after the paracentesis was performed. The final follow up period varied from 6 months to more than 3 years. The clinical data were analysed with the emphasis on the occurrence of cataract and a history of corneal infections or endophthalmitis.

RESULTS

In this series no serious side effects such as cataract, keratitis, or endophthalmitis were observed. The depth of the anterior chamber of all evaluated patients was restored after 30 minutes. In five out of 72 cases (three AIDS patients with cytomegalovirus retinitis and two patients with anterior uveitis due to herpes simplex virus) a small hyphaema was observed 30 minutes after the paracentesis took place.

CONCLUSION

Anterior chamber paracentesis appears to be a safe procedure in the hands of an experienced ophthalmologist.

Evaluation of a new self-screening chart for cytomegalovirus retinitis in patients with AIDS

AIDS patients often present without visual symptoms despite severe vision-threatening cytomegalovirus (CMV) retinitis. A new self-examination chart, the Teich Target (copyright 1993, Steven A. Teich, pat. no. 370259), which tests the central 45 degrees of vision, was evaluated for its ability to screen AIDS patients for CMV retinitis. It was compared with the Amsler grid (which tests the central 20 degrees of vision) in 50 consecutive AIDS patients referred for ophthalmologic evaluation by a single practitioner. Of 19 patients found to have CMV retinitis, 12 (63%) noted scotomas with the Teich Target compared with 7 (37%) with the Amsler grid (p < 0.05). Overall, 13 of 20 (65%) infectious retinitis cases were detected by the Teich Target. and 7 of 20 (35%) with the Amsler grid (p < 0.05). All scotomas noted on the Amsler grid were detected by the Teich Target. Four visually asymptomatic patients with newly diagnosed CMV retinitis noted scotomas only with the Teich Target. Both methods detected a branch retinal artery occlusion, but only the Teich Target detected a quadrantanopsia due to cerebral toxoplasmosis. There were no false positives with either method. In this small series, the Teich Target was more effective than the Amsler grid in screening AIDS patients for CMV retinitis primarily because it detected lesions beyond the central 20 degrees of vision. Peripheral CMV retinitis beyond the central 40 degrees occurred in 37% of patients and was net detected by either method. The Teich Target therefore augments but does not replace periodic ophthalmologic evaluations. The Teich Target may have potential utility for home use as a patient self-screening test for CMV retinitis or for mass screening in an AIDS clinic.

Serologic and polymerase chain reaction analysis of intraocular fluids in the diagnosis of infectious uveitis

PURPOSE

Infectious uveitis entities are usually rapidly progressive blinding diseases that can be prevented by prompt administration of specific antimicrobial therapy. With the aim of improving early diagnosis in patients with infectious uveitis, intraocular fluid samples from patients with sight-threatening posterior uveitis were investigated to determine the causative agent.

METHODS

Thirty-eight patients with acquired immunodeficiency syndrome (AIDS) and retinitis, eight immunosuppressed patients with retinitis, 16 immunocompetent patients with acute retinal necrosis, and 22 immunocompetent patients with toxoplasmic retinochoroiditis were analyzed by polymerase chain reaction for the presence of herpesviruses and Toxoplasma gondii DNA and for local antibody production against these microorganisms.

RESULTS

In patients with AIDS and retinitis, polymerase chain reaction was positive for cytomegalovirus DNA in 21 (91%) of the 23 ocular fluid samples obtained during active cytomegalovirus retinitis, whereas local antibody production analysis was negative in all cases. In acute retinal necrosis, varicella-zoster virus or herpes simplex virus could be established as the inciting agent in 81% of the cases, using the combination of both techniques. Polymerase chain reaction was positive in all samples obtained within two weeks after the onset of disease. Toxoplasma gondii DNA was detected in 4 of 13 samples (31%) from immuno-competent patients with active toxoplasmic retinochoroiditis; in each case, local antibody production was also detected. In contrast, no local antibody production was observed in two of three samples from transplant recipients that were positive for T. gondii DNA. All the control samples tested were negative for the above-mentioned tests.

CONCLUSIONS

In patients with AIDS, polymerase chain reaction analysis is preferable above local antibody production in detecting the inciting agent of retinitis. In other cases, the combination of both techniques can make a valuable contribution to the diagnosis.

Progressive zonal outer retinitis

We examined an immunocompetent patient with uniocular acute progressive outer retinitis. The retinitis was curvilinear in shape, showed progressive enlargement, and appeared to be altered by treatment with intravenous acyclovir. When regressed, the affected area of retina appeared atrophic and, at one-year follow-up, demonstrated intraretinal pigment migration with retinal pigment epithelial atrophy and atrophy of the choriocapillaris. Although visual acuity was unaffected, a dense scotoma was recorded on field testing. The response to acyclovir implicates the herpesvirus family, and acyclovir or another antiherpetic agent should be considered for such cases.

The progressive outer retinal necrosis syndrome. A variant of necrotizing herpetic retinopathy in patients with AIDS

BACKGROUND

The progressive outer retinal necrosis syndrome is a recently recognized variant of necrotizing herpetic retinopathy. This report characterizes more fully its clinical features and course.

METHODS

Using standardized clinical criteria, patients with progressive outer retinal necrosis syndrome from four institutions were identified. Patient records were reviewed retrospectively for the following data: medical and demographic characteristics, presenting symptoms, physical findings, course, responses to treatment, and outcomes.

RESULTS

Thirty-eight patients (65 involved eyes) were studied. All had acquired immune deficiency syndrome. A known history of cutaneous zoster was documented in 22 (67%) of 33 patients. Median CD4 lymphocyte count was 21/mm3 (range, 0-130/mm3). Median follow-up was 12 weeks. The most common presenting symptom was unilateral decreased vision (35 of 65 eyes, 54%); median visual acuity at presentation was 20/30 (range, 20/20 to no light perception [NLP]). Anterior chamber and vitreous inflammatory reactions were absent or minimal in all patients. Typical retinal lesions were multifocal, deep opacities scattered throughout the periphery, although macular lesions also were present in 21 eyes (32%) at diagnosis. Lesions progressed rapidly to confluence. Initial intravenous antiviral therapy appeared to reduce disease activity in 17 (53%) of 32 eyes, but treatment did not alter final visual outcome. Visual acuity was NLP in 42 (67%) of 63 eyes within 4 weeks after diagnosis. Retinal detachment occurred in 43 (70%) of 61 eyes, including 13 (93%) of 14 eyes that received prophylactic laser retinopexy.

CONCLUSION

The progressive outer retinal necrosis syndrome is characterized by features that distinguish it from cytomegalovirus retinopathy, acute retinal necrosis syndrome, and other necrotizing herpetic retinopathies. Visual prognosis is poor with current therapies.

Atypical cytomegalovirus retinitis: a clinicopathological correlation

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Recurrence of presumed varicella-zoster virus retinopathy in patients with acquired immunodeficiency syndrome

Five patients with acquired immunodeficiency syndrome (AIDS) and presumed varicella-zoster virus retinopathy had recurrence of retinopathy after stabilization with initial intravenous antiviral therapy. Recurrences were recognized as increased retinal opacification at the borders of preexisting lesions or as new lesions. In four of the five patients, recurrences were temporally associated with a reduction in the amount of antiviral medication being received. Changes included switch from intravenous to oral acyclovir (two patients), taper of oral acyclovir (one patient), and discontinuation of medications (one patient). In four patients disease was initially unilateral; in three of these four, disease subsequently developed in the previously unaffected fellow eye at the time of recurrence. The median time from stabilization of disease to recurrence was 51 days (range, 14 to 90 days). In contrast to the management of varicella-zoster virus retinopathy in immunocompetent patients and varicella-zoster virus lesions of the skin, varicella-zoster virus retinopathy in patients with AIDS appears to require chronic suppressive antiviral therapy to prevent recurrences. In this respect it is similar to other opportunistic retinal infections in patients with AIDS. The best drugs and optimal treatment regimens for maintenance antiviral therapy remain unknown.