RETINAL FUNCTION AFTER VITRECTOMY

Cone implicit time as a predictor of visual outcome in macular hole surgery

PURPOSE

To investigate whether preoperative retinal function measured by full-field ERG and multifocal ERG is correlated to postoperative visual acuity after macular hole surgery.

METHODS

Standard pars plana vitrectomy with removal of the internal limiting membrane (ILM) was performed on 19 consecutive patients undergoing macular hole surgery. Intraocular gas tamponade with a C2F6 gas-air mixture was employed, followed by a face-down position for at least 5 days. The patients were examined with the ETDRS chart, full-field ERG (Espion), multifocal ERG (Veris 6), and optical coherence tomography (OCT) preoperatively, and 6 weeks, 6 months, and 18 months after surgery.

RESULTS

The cone 30-Hz flicker implicit time in the full-field ERG reflecting retinal function was prolonged (p = 0.016) before surgery compared to aged-matched controls. After macula hole surgery, longstanding alteration of cone function reflected by mfERG and full-field ERG was verified 18 months after surgery. The prolonged cone 30-Hz flicker implicit time in the full-field ERG before surgery was significantly correlated to the ETDRS visual acuity 6 months postoperatively (p = 0.03).

CONCLUSIONS

Preoperative evaluation of retinal function with multifocal ERG and full-field ERG improves the understanding of the retinal recovery process after macular hole surgery. The cone implicit time in full-field 30-Hz flicker ERG could be a valid predictor of long-term visual outcome, which may be useful for selecting patients suitable for surgery.

Efficacy of vitrectomy in improving the outcome of Bacillus cereus endophthalmitis

PURPOSE

To evaluate the efficacy of vitrectomy with vancomycin for the treatment of experimental Bacillus cereus endophthalmitis.

METHODS

Endophthalmitis was initiated in rabbits via intravitreal injection of 100 colony-forming unit B. cereus. Treatment groups included 25-gauge transconjunctival sutureless vitrectomy with intravitreal vancomycin (1 mg) or vancomycin alone. Groups were treated at 4, 5, or 6 hours after infection. At 48 hours (for 4-hour and 5-hour groups) or 36 hours (for the 6-hour group) after infection, eyes were analyzed by electroretinography, histology, and inflammatory cell counts.

RESULTS

Treatment with vitrectomy/vancomycin at 4 hours resulted in significantly greater retinal function compared with that of vancomycin alone. Intraocular inflammation after treatment at 4 hours was minimal for both the treatment groups. Treatment with vitrectomy/vancomycin or vancomycin alone at 5 hours or 6 hours after infection resulted in similar levels of retinal function loss (i.e., >90%) and significant intraocular inflammation.

CONCLUSION

These results demonstrate that vitrectomy may be of therapeutic benefit in the treatment of B. cereus endophthalmitis but only during the early stages of infection.

Surgical Results and Microscopic Analysis of the Tissue Reaction following Implantation and Explantation of an Intraocular Implant for Epiretinal Stimulation in Minipigs

AIMS

For the purpose of visual rehabilitation of subjects with photoreceptor degeneration, an implantable microelectronic device for epiretinal stimulation was developed. Our study aimed to show whether implantation and explantation could be conducted safely and to investigate tissue compatibility.

METHODS

The device was implanted in 5 Göttinger minipigs. Four weeks later, the implant was surgical- ly removed. Histopathological examination that followed aimed at detecting inflammatory or proliferative changes. Stains used were hematoxylin and eosin, leukocyte common antigen, CD68 and glial fibrillary acidic protein. A grinding technique was used to visualize the retinal tissue in conjunction with the retinal tacks.

RESULTS

The implantation of the devices was successful in all cases. The explantation was complicated by intraoperative hemorrhages. Complete explantation could only be achieved after modifying the implantation strategy. Histopathology revealed a mild degree of cystic disaggregation of the retina. Immunohistochemically, an increased glial fibrillary acidic protein expression of Müller cells was found, which shows a moderate glial cell activation. Inflammatory cells were absent. Using the grinding technique, tissue adjacent to the retinal tacks showed a mild gliosis.

DISCUSSION

The viability of implantation and explantation of the implant in minipigs has been shown. The absence of immunoreactive cells or a considerable glial reaction suggest that the device may be considered safe and suitable for further implantation in humans.

Pharmacological dissection of multifocal electroretinograms of rabbits with Pro347Leu rhodopsin mutation

PURPOSE

To determine whether photoreceptor degeneration in transgenic (Tg) rabbits carrying the Pro347Leu rhodopsin mutation alters the neural activity of the middle and inner retinal neurons.

METHODS

Multifocal electroretinograms (mfERGs) were recorded from eight 12-week-old Tg rabbits both before and after intravitreal injection of the following: tetrodotoxin citrate (TTX), N-methyl-DL: -aspartic acid (NMDA), 2-amino-4-phosphonobutyric acid (APB), and cis-2,3-piperidine-dicarboxylic acid (PDA). Digital subtraction of the mfERGs recorded after the drugs were administered from those recorded before was used to extract the components that were eliminated by these drugs. Eight agematched, wild-type (WT) rabbits were studied with the same protocol.

RESULTS

There was no reduction in the amplitude of the cone photoreceptor response of the mfERGs in Tg rabbits. Both the first positive and the first negative waves of the ON-bipolar cell responses were significantly larger in the Tg than in the WT rabbits. Late negative waves of the ON-bipolar cell response were recorded only in the WT rabbits. The first negative wave of the inner retinal responses was larger in the Tg than in the Wt rabbits. The late positive waves were seen mainly in the WT rabbits.

CONCLUSIONS

The ON-bipolar cell and inner retinal responses were altered at the early stage of photoreceptor degeneration in Tg rabbits despite the preservation of the cone photoreceptor responses.

Blood-assisted internal limiting membrane peeling for macular hole repair

PURPOSE

To evaluate the efficacy of autologous heparinized whole blood in assisting internal limiting membrane (ILM) peeling by coating the ILM for macular hole (MH) repair.

DESIGN

Prospective, interventional case series.

PARTICIPANTS

Twenty-nine patients (32 eyes) who underwent blood-assisted ILM peeling for MH repair.

METHODS

Patients in whom stage 2-4 idiopathic MHs had developed and who desired surgery were enrolled in this study. After core vitrectomy, autologous heparinized whole blood was applied to cover the macula and to coat the surface of the macular area in the fluid-filled vitreous cavity. The redundant blood was removed and only a very thin film of blood was left on the macular area. The blood-coated ILM was removed by forceps in a circular fashion. To confirm the removed membrane was the ILM, the first 10 specimens were examined by electron microscopy (EM).

MAIN OUTCOME MEASURES

The MH closure rate, the interval mean visual acuity (before and after surgery), retinal changes, and the EM results of the ILM specimens.

RESULTS

All 32 eyes in 29 patients completed 12 months of follow-up. The ILM were coated by autologous heparinized whole blood, removed without difficulty, and confirmed by EM. The whole blood highlighted the contrast of the coated and noncoated areas during the ILM peeling procedure. The MHs were closed in all surgical eyes with a single surgery (100%). Compared with study entry, the mean logMAR best-corrected visual acuity 12 months after surgery improved significantly (1.02 and 0.53, respectively; P<0.001). At 12 months of follow-up, 31 eyes (96.9%) had stable or improved vision. No toxic fundus changes were observed during follow-up.

CONCLUSIONS

Autologous heparinized whole blood coated the ILM and facilitated visibility during ILM peeling. Autologous heparinized whole blood is a cost-effective and useful tool for assisting MH surgery.