Prevention of intraocular pressure rise following intravitreal injection

[Prevention of intraocular pressure elevation following intravitreal injections]

Determining the role of vascular endothelial growth factor (VEGF) in the pathogenesis of intraocular neovascularization prompted the development of anti-VEGF therapy. In general, these intravitreal injections (IVI) are considered relatively safe. One of the side effects that can occur after IVI of anti-VEGF agents is ocular hypertension, it can be acute or persistent. Numerous studies investigating the prevention of ophthalmic hypertension have been carried out in connection with the proven risk of short-term intraocular pressure (IOP) elevation after anti-VEGF injections. Scientific literature describes several methods of preventing intraocular pressure spikes after IVI: prophylactic medications, anterior chamber paracentesis, scleral decompression. Despite the significant number of publications, there is no universal consensus on the necessity of prevention measures for IVI of anti-VEGF drugs since the clinical benefits of slightly reducing the short-term IOP spikes remain unclear. This literature review analyzes the prospects of preventing ocular hypertension after IVI of anti-VEGF agents.

Effect of antiglaucoma agents on short-term intraocular pressure fluctuations after intravitreal bevacizumab injections

PURPOSE

To evaluate the effect of prophylactic pressure-lowering medications on intraocular pressure (IOP) spikes after intravitreal injections (IVIs) METHODS: In this randomized double-blind clinical trial, 74 eyes that were candidates for intravitreal anti-vascular endothelial growth factor (VEGF) injection (IVI) (0.05 mL, 1.25 mg of bevacizumab) were enrolled and sorted randomly into five groups, group 1: topical timolol 0.5% (n = 16); group 2: topical brimonidin (n = 15); group 3: oral acetazolamide 250 mg (n = 14); group 4: intravenous mannitol (1.5 gr/kg) (n = 16); group 5: no intraocular pressure-lowering medication (n = 13). Medications were administered 30-60 min prior to injection. None of the patients had history of glaucoma. Intraocular pressure was measured before (baseline), 5 min after (T5), 10 min after (T10), 15 min after (T15) and 30 min after (T30) IVI using Goldmann Tonometer.

RESULTS

There was a statistically significant, but relatively weak negative correlation between the amount of vitreous reflux post-IVI intraocular pressure elevation (Spearman's rho = -0.315, p = 0.006). There was no difference of the amount of vitreous reflux (P = 0.196) between study groups. The baseline mean IOP for Groups 1, 2, 3,4 and 5 were 11.19 ± 3.7, 10.07 ± 2.19, 11 ± 2.98, 10.13 ± 3.48 and12.54 ± 2.60 mmHg, respectively. (P = 0.214) There was no difference of peak IOP spike between groups at T5: 37 ± 19.7, 34.80 ± 15.76, 33.43 ± 18.29, 33.56 ± 16.88, 34.92 ± 9.99 mmHg (P = 0.977). There was also no difference of IOP at T10, T15 and T30 between study groups: P = 0.979, P = 0.994 and P = 0.692, respectively.

CONCLUSION

Although it is advisable to prevent IOP spikes, our study showed that use of prophylactic pressure-lowering medications with every mechanism of action has no effect in IOP spikes following intravitreal bevacizumab injections in non-glaucomatous eyes. Trial registrationThe study was registered with clinicaltrails.gov (ID# NCT02140450). Trial registration date: 05.09.2014.

Survey of Intravitreal Injection Techniques Among Retina Specialists in Mexico

Purpose

To report technique preferences for intravitreal injections among retina specialists in Mexico.

Methods

Cross-sectional survey. Ophthalmologists with a two-year retina training, active members of the Mexican Retina Association, were contacted through email to answer a survey consisting of 37 items regarding their IVI application technique.

Results

A total of 133 retina specialists participated, with a response rate of 78%. Forty-five percent applied the intravitreal injections in an operating room designated for the procedure. Sixty-three percent reported never injecting both eyes on the same day. Ninety-six percent wore a face mask during the procedure and 91% wore gloves. Eighty-two percent used a lid speculum. Tetracaine drops were the anesthetic method employed by 97% of participants. All participants utilized povidone-iodine for antisepsis. Eighty percent measured the puncture site with a caliper. Superotemporal quadrant was the one chosen to place the injection by 63% of participants. Fifty-nine percent indicated post-injection antibiotic drops for several days. Post-injection counting fingers visual acuity was verified by 53% of the participants. Fifty-six percent of the participants placed an eye-patch after the procedure.

Conclusion

There are different practices regarding the application of intravitreal injections among retina specialists in Mexico. Performing this type of survey periodically could show changes in preferences, as new evidence is incorporated into clinical practice.

Reduction of Intraocular Pressure Spikes Due to Intravitreal Bevacizumab Injections by Scleral Indentation with Cotton Swab or Digital Ocular Massage: Innovative Techniques Compared

Purpose

This study aims to evaluate the effectiveness of different decompressive injection techniques in reducing intraocular pressure (IOP) spikes, if compared to the injection without pressure applied on the eye, following the intravitreal injection of bevacizumab.

Patients and Methods

Two hundred patients with indication to intravitreal therapy were randomized into five arms: 40 received intravitreal injection without ocular decompression (arm A), 40 with pre-injection scleral indentation with cotton swab (arm B), 40 with pre-injection digital ocular massage (arm C), 40 with post-injection scleral indentation with cotton swab (arm D) and 40 with post-injection digital ocular massage (arm E). All patients underwent measurement of the IOP with Goldamm applanation tonometer 10 minutes before and 10 minutes after the injection. The primary endpoint of the study was variation of the post- injection IOP with the different techniques.

Results

An increase in post-injection IOP was observed in all the arms, if compared to pre-injection values. The greatest increase was observed in arm A with a mean IOP rise of 17.60 mmHg. All other techniques showed lower mean IOP increases: arm B 10.76 mmHg, arm C 9.35 mmHg, arm D 8.8 mmHg, arm E 3.4 mmHg. The post-injection IOP differences of innovative techniques compared to the technique without ocular decompression were all statistically significant (p-value <0.01). If compared to arm A (35%), a reduction in IOP spike ≥40 mmHg frequency was also observed. The status of phakia/pseudophakia, a previous diagnosis of glaucoma and the underlying pathology for which indication was given to inject bevacizumab did not significantly alter the post-injection IOP in any of the protocols.

Conclusion

The introduction of new injection protocols, such as injections performed before or after decompressive treatments, could be a safe and effective approach to control post-injection IOP increase.

Predictors of sustained intraocular pressure elevation in eyes receiving intravitreal anti-vascular endothelial growth factor therapy

PURPOSE

To determine the intravitreal anti-vascular endothelial growth factor (VEGF) injection techniques and preferences within the retinal community and to identify potential factors associated with the development of sustained intraocular pressure (IOP) elevation in patients treated with intravitreal anti-VEGF therapy for neovascular age-related macular degeneration (AMD).

DESIGN

Cross-sectional physician survey.

METHODS

Five hundred and thirty retina specialists spanning both private and academic practices were surveyed regarding current anti-VEGF intravitreal injection protocols, including the anti-VEGF drug of choice, needle gauge, injection volume, injection technique, and self-reported prevalence of sustained IOP elevation. Multivariate logistic regressions were performed to assess the potential influence of these factors on long-term IOP.

RESULTS

Two hundred ninety-two specialists (55%) reported believing that intravitreal anti-VEGF therapy may cause sustained IOP elevation. Of these responses, the most common reported prevalence was 1%-2% (48%), followed by 3%-5% (34%). There was no relationship between the frequency of sustained IOP elevation and anti-VEGF drug of choice. Physicians who injected greater than 0.05 cc in less than 1 second were 5.56 times more likely to observe a high frequency of sustained IOP elevation (P=.006, 95% CI 1.64-18.89).

CONCLUSIONS

Based on physician survey data, serial anti-VEGF injections using higher injection volumes with a rapid injection technique may potentially lead to sustained IOP elevation. The underlying mechanism for this complication may be injury to the trabecular meshwork resulting from rapid elevations in IOP. Further investigation of the relationship between injection techniques and sustained IOP elevation in the form of retrospective or prospective clinical studies is warranted.

Purinergic control of vascular tone in the retina

Purinergic control of vascular tone in the CNS has been largely unexplored. This study examines the contribution of endogenous extracellular ATP, acting on vascular smooth muscle cells, in controlling vascular tone in the in vivo rat retina. Retinal vessels were labelled by i.v. injection of a fluorescent dye and imaged with scanning laser confocal microscopy. The diameters of primary arterioles were monitored under control conditions and following intravitreal injection of pharmacological agents. Apyrase (500 units ml(-1)), an ATP hydrolysing enzyme, dilated retinal arterioles by 40.4 ± 2.8%, while AOPCP (12.5 mm), an ecto-5'-nucleotidase inhibitor that increases extracellular ATP levels, constricted arterioles by 58.0 ± 3.8% (P < 0.001 for both), demonstrating the importance of ATP in the control of basal vascular tone. Suramin (500 μm), a broad-spectrum P2 receptor antagonist, dilated retinal arterioles by 50.9 ± 3.7% (P < 0.001). IsoPPADS (300 μm) and TNP-ATP (50 μm), more selective P2X antagonists, dilated arterioles by 41.0 ± 5.3% and 55.2 ± 6.1% respectively (P < 0.001 for both). NF023 (50 μm), a potent antagonist of P2X1 receptors, dilated retinal arterioles by 32.1 ± 2.6% (P < 0.001). A438079 (500 μm) and AZ10606120 (50 μm), P2X7 antagonists, had no effect on basal vascular tone (P = 0.99 and P = 1.00 respectively). In the ex vivo retina, the P2X1 receptor agonist α,β-methylene ATP (300 nm) evoked sustained vasoconstrictions of 18.7 ± 3.2% (P < 0.05). In vivo vitreal injection of the gliotoxin fluorocitrate (150 μm) dilated retinal vessels by 52.3 ± 1.1% (P < 0.001) and inhibited the vasodilatory response to NF023 (50 μm, 7.9 ± 2.0%; P < 0.01). These findings suggest that vascular tone in rat retinal arterioles is maintained by tonic release of ATP from the retina. ATP acts on P2X1 receptors, although contributions from other P2X and P2Y receptors cannot be ruled out. Retinal glial cells are a possible source of the vasoconstricting ATP.

Time profile of viral DNA in aqueous humor samples of patients treated for varicella-zoster virus acute retinal necrosis by use of quantitative real-time PCR

The objective of this study was to evaluate the kinetics of varicella-zoster virus (VZV) loads using quantitative PCR (qPCR) in patients treated for acute retinal necrosis (ARN). Six patients (52 ± 13 years old) with ARN syndrome were consecutively studied. Aqueous humor (AH) was sampled from both eyes of all patients for qPCR evaluation. The patients were treated with intravenous acyclovir and intravitreal injections of antiviral drugs. The mean follow-up time was 17.6 ± 16.4 months. Main outcome measures were the numbers of viral genome copies in the AH, assessed using real-time qPCR with hydrolysis probe technology with a threshold of detection of 200 copies/ml. Two main portions of the viral load curves were observed for each patient: a plateau phase (27.8 ± 24.9 days) and a decrease in the number of viral genome copies. The mean baseline viral load was 3.4 × 10(7) ± 4.45 × 10(7) copies/ml (6 × 10(6) to 1.2 × 10(8) copies/ml). The viral load decreased according to a logarithmic model, with a 50% reduction obtained in 3 ± 0.7 days. There was a significant viral load (>102 copies/ml) at 50 days after the onset of treatment, despite antiviral drugs. qPCR use demonstrated reproducible VZV DNA kinetics with a two-phase evolution: a plateau followed by a logarithmic decrease. These data suggest that high-dosage antiviral therapy administered for the conventional 10-day duration is insufficient for most patients. This series of patients responded with a similar decrease in viral load once treatment was initiated, and the data from these patients may be used to predict the responses of future patients.

Intraocular Pressure rise after Anti-VEGF Treatment: Prevalence, Possible Mechanisms and Correlations

Intraocular pressure (IOP) rise after anti-vascular endothelial growth factor (VEGF) treatment for neovascular age-related macular degeneration (AMD) can be either short-term or long-term and may require medical intervention. Short-term IOP spikes are a fairly common and well recognized complication of anti-VEGF injections. Long-term IOP rise is less well-understood and disputed as a complication by some authors. We try to review current literature on the subject and especially studies focused on the prevalence of this complication, speculate on possible mechanisms of IOP rise and discuss correlations of long-term IOP rise with the nature of the injected agent, average number of injections, previous glaucoma history and other factors. How to cite this article: Kampougeris G, Spyropoulos D, Mitropoulou A. Intraocular Pressure rise after Anti-VEGF Treatment: Prevalence, Possible Mechanisms and Correlations. J Current Glau Prac 2013;7(1):19-24.

[Immediate changes in intraocular pressure after an intravitreal injection of 2.5 mg of bevacizumab]

PURPOSE

To report the immediate changes of intraocular (IOP) pressure after an intravitreal injection of 2.5mg (0.1 ml) of bevacizumab.

METHODS

Prospective, non-controlled, interventional case series of 45 patients undergoing intravitreal injection of 2.5mg (0.1 mL) of bevacizumab for a variety of retinal disorders. IOP was measured with a Goldmann tonometer at baseline, immediately after, 30 minutes and one day after injection in all of the cases. The main outcome measured was the IOP immediately after injection.

RESULTS

At baseline the mean IOP was 16.6±2.8mm Hg (range, 10-24 mm Hg; median, 16 mm Hg; 25(th) percentile, 14 mm Hg and 75(th) percentile, 18 mm Hg). IOP rose to 53.9±18.2mm Hg (range, 16-78 mm Hg, median, 54 mm Hg; 25(th) percentile, 40 mm Hg and 75(th) percentile, 70 mm Hg; p<0.001) immediately after the injection. After 30 minutes, the IOP normalized but was still higher than baseline with a mean of 19.8±5.2 mm Hg (range, 10-36 mm Hg; median,18 mm Hg; 25(th) percentile,16 mm Hg and 75(th) percentile, 24 mm Hg; P<.01). At 24 hours the IOP was 15.7±3.1 mm Hg (range,10-24 mm Hg; median, 16 mm Hg; 25(th) percentile,14 mm Hg and 75(th) percentile,18 mm Hg; p>0.05).

CONCLUSIONS

An intravitreal injection of 2.5mg (0.1 ml) of bevacizumab causes a transient elevation of IOP that tends to return to normal 30 minutes later.

Subconjunctival reflux and need for paracentesis after intravitreal injection of 0.1 ml bevacizumab: comparison between 27-gauge and 30-gauge needle

PURPOSE

Intravitreal injections may lead to a significant elevation of the intraocular pressure (IOP). A paracentesis may become necessary for acute reduction of the IOP in certain cases. The purpose of this study was to determine the frequency of paracentesis performed and the grade of reflux under the conjunctiva after injection of 0.1 ml bevacizumab (1.25 mg), depending on the thickness of the needles used.

METHODS

A retrospective review was undertaken of the surgery reports of 234 consecutive intravitreal bevacizumab injections in 145 eyes of 144 patients within 14 months. In particular, the frequency of paracentesis, the thickness of the needles used (27-gauge versus 30-gauge), the lens status, and a semi-quantitative reflux grade were analysed.

RESULTS

A paracentesis was performed in 78 cases (33%) for acute reduction of the IOP. In the 27-gauge group the frequency was 26% (25 of 96), and in the 30-gauge group 38% (53 of 138) (p = 0.05, independent estimating equation (IEE)). The medians of the semi-quantitative assessment of the reflux grade under the conjunctiva were 2.0 in the 27-gauge group (corresponding to a mild reflux) and 1.0 in the 30-gauge group (corresponding to a minimal reflux, p < 0.001, IEE).

CONCLUSIONS

When using a 30-gauge needle for intravitreal injections, the reflux under the conjunctiva was less than with a 27-gauge needle. However, the use of a 30-gauge needle appeared to be associated with a higher frequency of paracentesis.

Safety and efficacy of intravitreal triamcinolone for cystoid macular oedema in uveitis

PURPOSE

To report the safety and efficacy of intravitreal triamcinolone in the treatment of inflammatory cystoid macular oedema (CMO) in six patients who were resistant to other forms of therapy.

METHODS

An open-label unmasked prospective nonrandomized pilot study of six patients with idiopathic uveitis and visually significant macular oedema, resistant to periocular and/or systemic corticosteroid treatment, was carried out. Baseline examination and investigations were performed, including fundus fluorescein angiography, and the patients were given a single intravitreal injection of triamcinolone (4 mg/0.1 mL). The primary outcome measure was angiographic resolution of CMO. Patients were reviewed at intervals of 2-4 weeks for 12 months.

RESULTS

A single intravitreal injection of triamcinolone induced clinical and angiographic resolution of inflammatory macular oedema in all patients for varying periods of time up to 6 months. Five patients experienced increased intraocular pressure to 30 mmHg or greater which required treatment. Two patients developed posterior subcapsular cataract.

CONCLUSION

One injection of intravitreal triamcinolone was an effective short-term treatment for resistant CMO in uveitis. As with steroids given by other routes, raised intraocular pressure and cataract may occur. As it was so effective in these eyes with resistant CMO, a larger study is warranted to evaluate this form of therapy.

Quantitative analysis of intravitreal injections in the rat

Intravitreal injections are currently used in the rat to introduce a therapeutic factor in the eye, especially for experimental treatments of retinal degenerations. The injected volume and its location can influence the quantification of results. We have investigated the quantitative effect of a single intravitreal injection in rats at different ages and for different volumes. Albinos rats aged three weeks or two months received intravitreal injections of 1, 3, 5 or 10 microl China ink. Animals were sacrificed immediately after injection, eyes were enucleated, fixated, embedded in paraffin and microtomy was performed in a sagittal plane. Regularly spaced sections were analyzed to reconstruct the vitreous and injected dye volumes. The measured vitreous volume was 6.76 +/- 0.37 mm(3) in three weeks old rats and 13.36 +/- 0.64 mm(3) in two months old rats. Mean intravitreal ink volumes immediately after injection were 0.8 mm(3) for 1 ml injections, 2 mm( 3) for 3 ml, 2.3 to 2.6 mm(3) for 5 microl and 3.2 mm(3 ) for 10 microl. The percentage of vitreous volume involved by the injection ranged from 4.4% to 33.2%. The injected volume is limited by the large lens size of the rat. Extraocular loss of injected solution increases for higher injected volumes, with larger standard deviations. In this model, the dye tends to localize behind the lens. A 3 or 5 microl volume appears to have the best reproducibility with minimum loss of solution.

Etoposide as a virocidal anticytomegalovirus therapy: intravitreal toxicology and pharmacology in rabbits

BACKGROUND

Although Cytomegalovirus (CMV) retinitis is now a common intraocular infection, current therapy is only virostatic so ongoing treatment is required. Etoposide was found to be virocidal for CMV in laboratory experiments and it might prove to be beneficial clinically. We investigated the toxicity and intraocular concentration of etoposide (VP16) and its new analogue etoposide-phosphate (VP16P) following intravitreal injections in rabbit eyes.

METHODS

First a sequential dose-response was assessed with flash electroretinogram for both eyes of light- and dark-adapted rabbits (n = 7; one rabbit for each dose) over a range of light intensities before and after intravitreal injection of VP16 or VP16P to one eye; the other eye was injected with normal saline as a control. A multidose study was then performed on four rabbits. A non-toxic dose of VP16P (50 or 75 g) was injected into the vitreous of one eye on four occasions 1 week apart. A photopic electroretinogram was performed before the first injection and 6 weeks after the last injection. All the eyes from the electroretinogram studies were fixed in formalin, placed in paraffin, then stained with haematoxylin and eosin and examined under a light microscope. To determine the time-course of the intraocular concentrations of VP16P a sequential pharmacokinetic study was performed using a further 12 rabbits. Each rabbit was injected with 50 g VP16P to one eye and 75 g VP16P to the other eye. Three of these rabbits were killed at 1, 3, 6 and 9 h after injection. Samples of vitreous were assayed for both VP16 and VP16P using HPLC. An in vitro dose response assay was performed using third-passage bovine retinal pigment epithelial (RPE) cells cultured in Dulbecco's modified Eagles medium with fetal calf serum. The effect of a log-dose increment of VP16P on the RPE cell proliferation was assessed using tritiated thymidine incorporation.

RESULTS

The electroretinogram studies suggested that VP16 was toxic even with the 10 g dose. For VP16P a toxic effect was noted following injection of a single dose greater than 100 g. Multiple injections of 50 or 75 g VP16P did not produce a toxic response. Histological examination demonstrated significant abnormality only with the 500 g dose of VP16 or VP16P. VP16P was rapidly metabolized to VP16 in the eye, producing concentrations of 2.0 g/mL or more for up to 9 h following a 75-microg dose. This suggests that the electroretinogram findings following VP16 injections were confounded by a toxic effect of the ethanol solvent (which is absent from the VP16P preparation). VP16P was quite potent, the ID50 was about 0.1 g/mL for bovine RPE cells in the in vitro assay.

DISCUSSION

These results indicate that multiple 75-gVP16P intravitreal injections were not toxic to the rabbit eye and provide a therapeutic intraocular concentration for up to 9 h after the injection.

High-dose (2000-microgram) intravitreous ganciclovir in the treatment of cytomegalovirus retinitis

OBJECTIVE

The authors prospectively studied visual outcome, relapse, complications, and survival of patients with acquired immune deficiency syndrome (AIDS)-related cytomegalovirus (CMV) treated with high-dose intravitreous ganciclovir (2 mg/0.1 ml) injections. The outcomes were compared with those of patients treated with standard doses of intravenous ganciclovir in the same institution. The histopathologic and electrophysiologic effects of high-dose intravitreous ganciclovir injections in rabbits also were studied.

DESIGN

A nonrandomized case series.

PARTICIPANTS

A total of 42 patients (74 eyes) were treated with intravitreous injections and 18 patients (27 eyes) were treated with intravenous ganciclovir. Five eyes of three New Zealand white rabbits were injected with ganciclovir, and the sixth eye was a control specimen.

INTERVENTION

Patients treated with intravitreous injections received twice-weekly doses of 2 mg/0.1 ml ganciclovir for 3 weeks, then weekly injections. Patients treated with intravenous ganciclovir received standard doses. Patients were monitored with regular examinations. Rabbit eyes were given intravitreous injections of 1 mg/0.1 ml of ganciclovir weekly for 4 weeks.

MAIN OUTCOME MEASURES

Assessments of vision, retinal inflammation, and survival were made. Electroretinograms were performed on the rabbit eyes, and they were processed for light and electron microscopy.

RESULTS

In the intravitreous group, visual acuity (VA) was stable in 64 of 74 eyes, 5 improved, and 5 deteriorated. Sixty-three (85%) of 74 eyes had final VA of 20/20 to 20/40. Relapse occurred in five eyes (7%; median time, 42 weeks). There were three cases of endophthalmitis. Median survival after diagnosis of CMV retinitis was 36 weeks. In the intravenous group, VA was stable in 18 eyes, 0 improved, and 9 deteriorated. Sixteen (59%) of 27 eyes had final VA of 20/20 to 20/40. Relapse occurred in 15 eyes (56%) at a median time of 21 weeks. Median survival was 21 weeks. The rabbit studies showed no evidence of toxicity.

CONCLUSION

High-dose intravitreous ganciclovir effectively suppressed CMV retinitis, preserved vision, and prevented relapse without deterioration in survival.

High dose intravitreal ganciclovir injection provides a prolonged therapeutic intraocular concentration

BACKGROUND

Although intravitreal high dose ganciclovir has previously been found to provide excellent control of cytomegalovirus (CMV) retinitis, little was known about the vitreous concentrations of ganciclovir after a 2 mg intravitreal injection.

METHODS

Eleven vitreous samples were taken from seven patients with CMV retinitis at 24 and 72 hours after a 2 mg intravitreal injection of ganciclovir and the concentration of ganciclovir was measured by high performance liquid chromatography.

RESULTS

The mean concentration of ganciclovir at 24 hours was 143.8 mg/l (95% confidence interval 97.8-190) and at 72 hours was 23.4 mg/l (95% CI 0-49.7). The half life ranged from 11.9 to 26.3 (mean 18.8) hours in the four patients who had two samples taken. The mean half life calculated from the mean concentrations at 24 and 72 hours was 18.3 hours, so the calculated mean concentration at 7 days was 0.6 mg/l.

CONCLUSIONS

This suggests that it takes about 7 days to eliminate the intravitreal ganciclovir, and that it is not likely to accumulate with weekly injections. The intravitreal concentrations achieved with high dose therapy remained above the ID50 for CMV (0.25-1.22 mg/l) for up to 7 days.

High dose intravitreal ganciclovir for CMV retinitis: a shelf life and cost comparison study

BACKGROUND

It was previously found that high dose intravitreal ganciclovir provided superior treatment of cytomegalovirus retinitis compared with intravenous treatment. This study examined the stability and solubility of the ganciclovir solution to determine the shelf life of prepared solution, and compared the cost of intravitreal with intravenous therapy.

METHODS

For the solubility studies high performance liquid chromatography was used to determine the ganciclovir concentration in various solutions. Measurements were taken of freshly made 20 mg/ml solution, the same solution stored at room temperature or frozen for 10, 17, and 24 days, after the solution was filtered, and after it was heated at 56 degrees C. For the cost comparison analysis the cost of 22 patients treated exclusively with intravitreal high dose ganciclovir was compared with cost estimates for the same patients treated with a standard intravenous therapy regimen over the same time.

RESULTS

There was little variation in the concentration of ganciclovir regardless of the storage conditions, suggesting that the 20 mg/ml solution was very stable. The heating and filtering experiments suggest that maximum solubility was achieved both in the freshly prepared and thawed frozen stored solution. The total cost of the intravitreal treatment was Aus $172,435 and the estimate of intravenous treatment was Aus $490,521. This represents a total saving of $318,086 (65%), or $14,458 per patient. The average number of weeks of treatment for each patient was 27.9 (613 weeks/22 patients), so the saving per patient per year was $29,946.

CONCLUSION

High dose intravitreal ganciclovir therapy may be administered in a very cost effective way, which along with its acceptability, safety, and clinical efficacy make it an attractive method of treatment of CMV retinitis.

Intraocular pressure after peribulbar anaesthesia: is the Honan balloon necessary?

Peribulbar anaesthetic blocks were administered to 70 patients and the intraocular pressure (IOP) measured immediately before and within 1 minute of the injections. In 10 patients IOPs were recorded at 1 minute intervals for 15 minutes after injection and then compared with the IOPs recorded in 60 patients after 5 or 10 minutes of Honan balloon ocular compression. The IOP rose significantly after injection in all patient groups and in some cases this increase was marked (over 50 mm Hg in 10 patients). The IOP showed an equivalent drop after 5 or 10 minutes of ocular compression when compared with eyes that did not receive ocular compression. The Honan balloon does not appear to be necessary to reduce IOP in the 10 minutes following peribulbar injection. Furthermore, the occurrence of IOP peaks after peribulbar anaesthesia suggests that the balloon should be used with caution in eyes in which the ocular circulation may be compromised.