Toxicity of ocular surgical solutions

Testing the Biocompatibility of a Glutathione-containing Intraocular Irrigation Solution by Using an Isolated Perfused Bovine Retina Organ Culture Model — an Alternative to Animal Testing

The effects of a glutathione-containing intraocular irrigation solution, BSS Plus®, on retinal function and on the survival of ganglion cells in whole-mount retinal explants were studied. Evidence is provided that the perfused ex vivo bovine retina can serve as an alternative to in vivo animal testing. Isolated bovine retinas were prepared and perfused with an oxygen-saturated standard irrigation solution, and an electroretinogram was recorded to assess retinal function. After stable b-waves were detected, the isolated retinas were perfused with BSS Plus for 45 minutes. To investigate the effects of BSS Plus on photoreceptor function, 1mM aspartate was added to the irrigation solution in order to obtain a-waves, and the ERG trace was monitored for 75 minutes. For histological analysis, isolated whole retinal mounts were stored for 24 hours at 4°C, in the dark. The percentages of cell death in the retinal ganglion cell layer and in the outer and inner nuclear layers were estimated by using an ethidium homodimer-1 stain and the TUNEL assay. General swelling of the retina was examined with high-resolution optical coherence tomography. During perfusion with BSS Plus, no significant changes in a-wave and b-wave amplitudes were recorded. Retinas stored for 24 hours in BSS Plus showed a statistically significant smaller percentage (52.6%, standard deviation [SD] = 16.1%) of cell death in the retinal ganglion cell layer compared to the control group (69.6%, SD = 3.9, p = 0.0031). BSS Plus did not seem to affect short-term retinal function, and had a beneficial effect on the survival of retinal ganglion cells. This method for analysing the isolated perfused retina represents a valuable alternative for testing substances for their retinal biocompatibility and toxicity.

Subconjunctival lidocaine before laser treatment: a randomized trial

PURPOSE

The aim of the study was to determine whether subconjunctival anesthesia is effective at reducing pain associated with laser retinopexy.

DESIGN

This was a single-center, prospective, patient-masked, randomized, controlled trial.

PARTICIPANTS

In the primary study group, 65 patients were recruited. Thirty-two patients (32 eyes) received anesthetic injection, and 33 patients (33 eyes) received the sham injection. The crossover study group consisted of 28 patients (56 eyes).

METHODS

Between February 2008 and April 2008, all patients who were consecutively booked to undergo panretinal photocoagulation (PRP) or peripheral laser retinopexy (PLR) were invited to participate in the study. Patients were randomized to receive subconjunctival lidocaine injection or a sham injection before their intended laser retinal treatment. These patients were defined as our primary study group. Patients who required a second laser treatment received the opposite injection in a masked fashion before laser retinal treatment. These patients were defined as our crossover group. Patients in both the primary study group and the crossover group were masked to the treatment given. After the laser treatment, patients completed a pain questionnaire.

MAIN OUTCOME MEASURES

The primary outcome was incidence of pain. The secondary outcome was severity of pain.

RESULTS

Primary study group: In the anesthetic treatment group, 19 patients (59%) experienced pain compared with 32 patients (97%) in the sham treatment group (P<0.001). Among the patients who did experience pain, the average pain score was 3.6 in the anesthetic treatment group and 4.1 in the sham treatment group (P=0.55). Crossover study group: In the anesthetic treatment group, 12 patients (43%) experienced pain compared with 28 patients (100%) in the sham treatment group (P<0.001). In patients who did experience pain, the average pain score was 3.3 in the anesthetic treatment group and 4.6 in the sham treatment group. Twenty patients (71%) preferred anesthetic to sham treatments, 1 patient (4%) preferred sham over anesthetic, and 7 patients (25%) thought both laser treatments were the same.

CONCLUSIONS

Subconjunctival 2% lidocaine significantly reduces the incidence of pain in patients who receive PRP or PLR.

Investigation of tear film change after recovery from acute conjunctivitis

PURPOSE

To study the changes of tear film after recovery from acute conjunctivitis.

METHODS

This study involved 73 eyes of 56 consecutive patients who complained of dry eye after recovery from acute conjunctivitis at the Zhongshan Ophthalmic Center. Excluded were other factors that could affect the stability of the tear film. Tear film breakup time (BUT), Schirmer 1 test (S1T), tear meniscus height (TMH), and fluorescein staining (FL) were performed on both recovered and healthy eyes. The scores were measured at 3, 7, 14, 21, and 30 days after recovery.

RESULTS

Compared with the results of the healthy eyes, most scores of BUT, S1T, TMH, and FL were all abnormal until day 30 after recovery from acute conjunctivitis. BUT decreased at 3, 7, 14, and 21 days (P < 0.05). S1T decreased at 3, 7, and 21 days (P < 0.05). TMH values became less than normal at 3, 7, and 14 days (P < 0.05). FL increased significantly at 7, 14, and 21 days (P < 0.05). At 30 days after recovery, all of the test scores returned to normal (P > 0.05).

CONCLUSIONS

During acute conjunctivitis, inflammation and topical therapeutic agents can alter the tear film secretion, resulting in dry eye for nearly 1 month in recovered eyes. To minimize the effect of topical agents to the tear film, individualized treatment instead of frequent instillation of topical agents is recommended for acute conjunctivitis.

Toxic endothelial cell destruction from intraocular benzalkonium chloride

PURPOSE

To present a cluster of cases of corneal edema occurring after phacoemulsification.

SETTING

Regional hospital in rural Australia.

METHODS

This retrospective case series comprised 12 patients from a single surgical list comprising 19 cases who developed persistent corneal edema after having phacoemulsification.

RESULTS

After 6 months, the edema improved in 1 patient. Inadvertent intraocular use of balanced salt solution (BSS) preserved with benzalkonium chloride was found to be the cause of this serious complication.

CONCLUSIONS

Benzalkonium chloride in concentrations commonly used extraocularly is highly toxic to the corneal endothelium. Every possible safeguard should be taken to prevent inadvertent intraocular use of such preserved solutions.