Combined OCT distance and FBG force sensing cannulation needle for retinal vein cannulation: in vivo animal validation.

PURPOSE: Retinal vein cannulation is an experimental procedure during which a clot-dissolving drug is injected into an obstructed retinal vein. However, due to the fragility and minute size of retinal veins, such procedure is considered too risky to perform manually. With the aid of surgical robots, key limiting factors such as: unwanted eye rotations, hand tremor and instrument immobilization can be tackled. However, local instrument anatomy distance and force estimation remain unresolved issues. A reliable, real-time local interaction estimation between instrument tip and the retina could be a solution. This paper reports on the development of a combined force and distance sensing cannulation needle, and its experimental validation during in vivo animal trials. METHODS: Two prototypes are reported, relying on force and distance measurements based on FBG and OCT A-scan fibres, respectively. Both instruments provide an 80 [Formula: see text] needle tip and have outer shaft diameters of 0.6 and 2.3 mm, respectively. RESULTS: Both prototypes were characterized and experimentally validated ex vivo. Then, paired with a previously developed surgical robot, in vivo experimental validation was performed. The first prototype successfully demonstrated the feasibility of using a combined force and distance sensing instrument in an in vivo setting. CONCLUSION: The results demonstrate the feasibility of deploying a combined sensing instrument in an in vivo setting. The performed study provides a foundation for further work on real-time local modelling of the surgical scene. This paper provides initial insights; however, additional processing remains necessary.

Laser-induced retinal injury following a recreational laser show: two case reports and a clinicopathological study.

BACKGROUND: Two patients who attended a dance festival with an audience-scanning laser show presented in our department with a decrease in visual acuity from a direct laser hit in one eye. Ophthalmoscopy showed a similarly sized retinochoroidal coagulation spot, which had led to a retinal hemorrhage in both patients. Because the organizers of the show concluded that the retinal injury was caused by powerful, handheld laser pointers in the crowd, we were interested in determining if these laser pointers could cause this kind of acute retinopathy. METHODS: A 44-year-old man with an extrafoveal, temporal choroidal melanoma was scheduled for enucleation. The eye (visual acuity 20/20) had a healthy-appearing macula. Prior to enucleation, the retina was exposed to eight different durations (0.5-64 seconds) of laser beam from a commercially available, handheld, class 3B green laser pointer (500 mW). RESULTS: Histologic analysis was unable to identify any abnormalities in the choriocapillaris, the photoreceptors or the retinal pigment epithelium (RPE). CONCLUSION: The use of powerful laser appliances (class 4 lasers) directed into the audience (audience-scanning laser show) can cause significant retinal injuries with lifelong visual consequences. It is unlikely that laser pointers, even those of class 3B, can cause these ocular injuries.

Preoperative eye disinfection in vitrectomy surgery using antibiotic or antiseptic eyedrops.

PURPOSE: To determine the efficacy of preoperative eye disinfection by comparing antibiotic and antiseptic eye drops. DESIGN: Prospective, randomized double-masked comparative study with three study arms: untreated, antibiotic treated and antiseptic treated. METHODS: Patients that were scheduled for vitrectomy were asked to use an antibiotic or antiseptic eye drop 4 times a day, 5 days before the surgery. Conjunctival smear was cultured at the onset of the surgery. Culture results for each study arm were compared. RESULTS: Comparable results were found in the patients treated with an antibiotic or antiseptic eye drop. CONCLUSIONS: Since an antiseptic eye drop will cause less bacterial resistance than an antibiotic eye drop, and both treatments have a similar antibacterial effect, this study indicates that prophylactic antiseptic eye drops may be preferred over antibiotic treatment, when prophylaxis is needed.

Comparison of postoperative comfort in 20 gauge versus 23 gauge pars plana vitrectomy.

PURPOSE: Although the sutureless 23Gauge (23G) vitrectomy technique is being increasingly used, a significant number of pars plana vitrectomies are still conducted using the 20G technique. This study evaluates whether the 23G vitrectomy causes less postoperative pain, less discomfort and a shorter duration of sick leave than the 20G vitrectomy. METHODS: In 2006, a questionnaire was sent to 877 patients who had undergone either 20G or 23G pars plana vitrectomy for different indications. Postoperative pain, discomfort of the eye and duration of sick leave were evaluated. Data for analysis was obtained from 544 patients. RESULTS: After receiving a 20G pars plana vitrectomy, patients had a significantly increased risk of sleeping less during the first postoperative night and week, waking up because of pain during the first postoperative night and week, taking pain medication during the first postoperative night and week and using a postoperative ointment. The 20G group also experienced a longer period of postoperative discomfort and reddish eyes. CONCLUSIONS: 23G pars plana vitrectomy causes significantly less postoperative pain and discomfort compared to 20G pars plana vitrectomy. The similar duration of leave in the patient groups could be explained because a fibrin sealant was used in the 20G group.

Systemic resorption of 5-fluorouracil used in infusion fluid during vitrectomy.

PURPOSE: The aim of this study is to determine whether 5-fluorouracil (5FU) used in the infusion fluid during vitrectomy is systemically absorbed. PATIENTS AND METHODS: The major catabolite of 5FU, alpha-fluoro-beta-alanine (FBAL) was measured in urine samples of 2 patients that underwent vitrectomy using 5FU in the infusion fluid. RESULTS: In both patients, FBAL was found in the urine samples collected up to 48 hours after the surgery, with the highest concentration and total amount in the first 6 hours after the first urine production after surgery. Moreover, the concentration and total amount of FBAL was higher in the patient who received silicone oil tamponade (versus 12.5% SF6), with the longest surgery time (40 min versus 20 min) and the highest amount of infusion fluid used (350 ml versus 250 ml). CONCLUSIONS: 5FU, used to prevent the formation of proliferative vitreoretinopathy (PVR), is systemically absorbed when used in infusion fluid during vitrectomy. As such, patient selection is needed to avoid adverse effects on procreativity. Further studies will be needed to determine which clinical setting will influence most the absorption.

Comparing fibrin glue to sutures for conjunctival closure in pars plana vitrectomy.

PURPOSE: To evaluate whether fibrin glue causes less postoperative pain, discomfort and work inaptitude in conjunctival closure following 20 gauge pars plana vitrectomy than sutures. DESIGN: Retrospective study. METHODS: A questionnaire was sent in 2006 to 506 patients who underwent 20 gauge pars plana vitrectomy in 2004 at the University Hospital, Leuven, Belgium. Patients were asked about their postoperative pain and discomfort of the eye and the duration of their work inaptitude. RESULTS: Our results showed a shorter duration of the eye being reddish (p-value 0.0471), discomfort of the eye (p-value 0.0376) and using an ointment (p-value 0.0105) in the glue group. The glue group used less ointment (p-value 0.0038) and independent workers had a shorter work inaptitude after receiving glue (p-value 0.0292). If patient had vitrectomy without cerclage, they had less pain on the first postoperative day when having received glue (p-value 0.0340). CONCLUSIONS: Fibrin glue causes less postoperative pain, discomfort and work inaptitude for closure of conjunctival wounds in 20 gauge pars plana vitrectomy than sutures. Fibrin glue appears in our hands to be a better alternative to sutures for closure of conjunctival wounds in 20 gauge pars plana vitrectomy.

Vitrectomy with peeling of the inner limiting membrane for treating diabetic macular edema.

PURPOSE: to evaluate the results of pars plana vitrectomy with peeling of the inner limiting membrane (ILM stained with infracyanine green (IfCG) in 26 patients with diabetic macular edema, and to identify which factors are associated with a better postoperative visual outcome. PATIENTS AND METHODS: 26 patients with diabetic macular edema were included in the study. A pars plana vitrectomy with ILM peeling stained with IfCG was performed, in some cases combined with cataract surgery. In 22 patients the ILM was retained, examined with electron microscopy and compared with normal ILM's. Visual acuity and fundus examination were recorded several months after surgery. To determine which factors lead to the best postoperative results, patients were divided into different groups and compared. RESULTS: during surgery, a taut posterior hyaloid was found in 26 patients, which was successfully detached in all cases. ILM peeling within the vessel arcade succeeded in all patients. Postoperative examination showed improved visual acuity and decreased macular edema in 19 patients, unaltered visual acuity in 3 patients and decreased visual acuity in 4 patients. Comparison between different groups of patients revealed that young patients with recent vision loss and without previous macular laser treatment, had better postoperative results. Electron microscopical examination showed a more condensed ILM in diabetic patients, consisting of a layer of fine curled fibers. CONCLUSION: pars plana vitrectomy with peeling of the ILM stained with IfCG leads to good postoperative results in young diabetic patients with recent vision loss due to macular edema and without previous macular laser treatment.

Bilateral acute retinal necrosis in a 12-year-old girl.

Acute retinal necrosis (ARN) is a severe ocular syndrome consisting of a moderate-to-severe anterior uveitis, vasculitis, and vaso-occlusive retinal necrosis. It can occur in healthy individuals at any age, but reports of this condition in children are rare.

Autologous peripheral retinal pigment epithelium translocation in patients with subfoveal neovascular membranes.

AIM: To evaluate the possibility of translocating autologous peripheral retinal pigment epithelial (RPE) cells and enhance their adhesion to improve functional outcome after choroidal neovascular membrane extraction in patients with subfoveal neovascular membranes. METHODS: A prospective, non-controlled surgical study in eight consecutive patients operated between February and July 2001 with final data monitoring in July 2002. All patients had mixed subfoveal membranes of 2-4 disc diameters. Functional tests included Snellen vision and central fixation testing. During vitrectomy, after the extraction of the neovascular complex, 8 x 10(4)-16 x 10(4) RPE cells were removed from the periphery and translocated under the macula following the submacular injection of 2 microg of poly-L-lysine to promote adhesion of the cells. RESULTS: With a follow up ranging from 3 months to 16 months, a pigmented area was seen in the extraction bed of the neovascular membrane in only one patient. Fixation was at the edge of the extraction bed in three patients. Vision remained the same in five patients and deteriorated in three (all with retinal detachment). Retinal detachment due to proliferative vitreoretinopathy occurred in three patients. CONCLUSIONS: The translocation of autologous peripheral RPE cells after membrane extraction was technically possible in a sterile manner, but was associated with a high proliferative vitreoretinopathy rate and in the present series had no measurable positive effect on functional outcome.

Double vital staining using trypan blue and infracyanine green in macular pucker surgery.

AIMS: To study the clinical properties of double vital staining in premacular fibrosis, facilitating complete removal of all epiretinal tissue. METHODS: In a two step surgery, the epiretinal pucker was removed after staining with trypan blue, whereafter the inner limiting membrane was peeled after staining with infracyanine green. RESULTS: In all 30 patients, a separate epiretinal layer and inner limiting membrane were removed from the macular area. Pathological examination showed different histological properties of the removed layers. An increased visual acuity was measured in 26 patients, and a slightly decreased visual acuity in one patient. CONCLUSION: The described double staining technique could be a novel valuable tool that may help to achieve optimal anatomical and functional recovery after surgery for premacular fibrosis

ICG staining of the inner limiting membrane facilitates its removal during surgery for macular holes and puckers.

Formation of a macular hole is an uncommon idiopathic disease whereby a disruption of the neural retinal layer is formed at the foveal area. It has been suggested that tangential traction of the inner limiting membrane (ILM) on the neuroretina may contribute to the formation of a macular hole. Removal of the ILM has been associated with very high closure rates in macular hole surgery. However, since the inner limiting membrane is a transparent layer, it can be difficult to achieve complete removal from the underlying neural retina. Also in surgery for macular pucker formation, whereby growth of epiretinal tissue induces metamorphopsia, removal of the ILM may play a beneficial role. This paper describes a method facilitating the removal of the inner limiting membrane by staining it with indocyanine green.

Unusual retinal vasculitis in a patient with protein S deficiency and systemic toxoplasmosis: a case report.

A 28-year old female patient presented with unilateral dropped visual acuity and a central scotoma. Fundus examination and a fluorescein angiogram were suggestive for central retinal vein prethrombosis. Further tests revealed an isolated protein S deficiency for which oral anticoagulation therapy was initiated. Six months later she presented with new symptoms of a right retrobulbar pain on ocular movements. The retinal vessels had normalized with improved visual acuity. Re-evaluation of the fluorescein angiogram taken six months earlier showed an image compatible with unilateral vasculitis. During this six month period persisting high levels of IgG and IgM antibodies against Toxoplasma were observed while no signs of other active infection could be found. This report illustrates that in cases of prethrombosis with vasculitis in a young patient, a full medical examination and a thorough investigation of infectious diseases are warranted.

OCT study of fellow eyes of macular holes.

The aim of this study was to examine the vitreomacular interface in symptom-free fellow eyes of macular holes using optical coherence tomography (OCT) to add information to the pathogenesis of macular holes and to refine prognostic factors for bilateral involvement. Sixty-six patients with a full thickness macular hole in one eye and a symptom-free fellow eye were included in the study between 01/98-05/99. The finding on OCT that a perifoveal vitreous detachment can result in a foveal cyst and subsequently a macular hole confirms the theory of Gass of vitreous traction. Symptom-free fellow eyes with a foveal cyst on OCT represent an elevated risk (55%) for macular hole development. Vitreofoveal separation is probably a good prognostic sign.

Properties of intra- and intercellular Ca(2+)-wave propagation elicited by mechanical stimulation in cultured RPE cells.

Membrane deformation induced by a mechanical stimulus increases the [Ca2+]i in cultured retinal pigment epithelial (RPE) cells, and in many other cell types. In this study, confocal microscopy and Ca(2+)-measurements using the fluorescent dye fluo-3 were used to measure the spatiotemporal characteristics of the Ca(2+)-wave propagation during a mechanical stimulation in Long Evans (LE) RPE cells or dystrophic Royal College of Surgeons (RCS) RPE cells. Ca2+ signals were recorded in the mechanically stimulated cell and in the neighboring cells. A regenerative Ca(2+)-wave with a decreasing rate of propagation was found in the stimulated cells. The rate of propagation was significantly slower in RCS-RPE cells compared to LE-RPE cells. Incubation with thapsigargin significantly lowered the propagation rate in both LE- and RCS-RPE cells. The amplitude of the [Ca2+]i-rise in the nucleus and cytoplasm was differentially modulated by protein kinase C in RCS-RPE cells, but not in LE-RPE cells. It is concluded that RCS-RPE cells have intracellular Ca(2+)-regulating properties which are different from those of LE-RPE cells.

Radiation-associated choroidal neovasculopathy.

PURPOSE: To characterize a newly discovered choroidal vascular abnormality in patients who have received radiation therapy for subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration. DESIGN: Two-center cross-sectional study. PARTICIPANTS: In the United States, there were 95 patients who were treated with 10 or 12 Gy of external beam photons. In Belgium, 98 patients were treated with 20 Gy. These patients were examined retrospectively for the presence of a specific CNV abnormality. RESULTS: During the follow-up period, an unusual vascular growth pattern was identified in 12 patients (12.6%) of those treated in the United States and in 7 (7.1%) of those treated in Belgium. These patients developed round or oval vascular blebs along the outer border of their neovascular lesions. These blebs profusely leaked fluorescein dye and could be imaged best by indocyanine green angiography. Patients with these blebs appeared to have a marked propensity for loss of visual acuity. CONCLUSION: An unusual pattern of new vessel growth occurred in 19 of the 193 patients with CNV treated with radiation. This new entity, termed radiation-associated choroidal neovasculopathy, is a recognizable disorder that appears to have a particularly poor prognosis.

The use of optical coherence tomography in macular diseases.

With optical coherence tomography (OCT), a new technique has emerged that allows imaging of a transverse section of the retina with a resolution that has not been reached by other imaging techniques. The OCT technique can be used in the diagnosis and assessment of various diseases of both the anterior segment and the ocular fundus. This paper demonstrates that OCT can deliver useful information in the diagnosis and follow-up of several macular diseases that cannot be obtained with other fundus imaging techniques. The optical principle of OCT is based on visible-light interference. OCT allows imaging of the anatomical foveal appearance. This normal foveal appearance is disrupted when macular edema occurs, leading to thickening of the neuroretina and cyst formation. The anatomical difference between a neuro-retinal elevation and RPE elevations can be demonstrated using OCT. Epiretinal membranes and pseudo-macular holes can easily be visualized. Perhaps the most interesting addition of OCT in the retinal diagnostic field is the imaging of vitreo-macular traction syndromes and staging of macular holes, which are both difficult with ophthalmoscopy and fluorescein-angiography. Each of the above mentioned macular diseases will be illustrated by a typical case.

How to protect your eyes from solar retinopathy.

On August 11, in Belgium a solar eclipse will occur which will be total in the Southern area of the country. Although the observation of a solar eclipse is an intriguing phenomenon, inappropriate shielding from the sunlight can cause irreversible ocular lesions. Besides good absolute absorption of visible light, a blocking of ultraviolet and infrared light is equally important. In this study, four homemade sun filters were tested: a soot-blackened piece of glass, a black unexposed developed slide film, an audio-CD and a recordable CD-ROM. Also two commercially available filters were investigated: eclipse-shades and mylar foil. The soot-blackened glass and black slide film slip were highly transparent for infrared light, making them dangerous for solar observation. The recordable CD-ROM was too transparent for visible light to serve as solar filter, while the audio-CD tested absorbed enough visible, ultraviolet and infrared light to make it suitable for eclipse viewing. However, many types of audio-CD's are available making it impossible for the observer to know if a given CD is safe to use for solar viewing. Both commercially available solar filters tested had a good absolute visible light absorption, as well as an equally good absorption of ultraviolet and infrared light, making them safe for eclipse observation.

Intra- and intercellular Ca2+ signaling in retinal pigment epithelial cells during mechanical stimulation.

The intercellular communication (IC) was investigated between cultured rat retinal pigment epithelial (RPE) cells isolated from Long-Evans (LE) or dystrophic Royal College of Surgeons (RCS) rats and grown in solutions containing normal and high glucose concentrations, or after modulation of protein kinase C (PKC). This was performed by studying the conduction of the free Ca2+-concentration ([Ca2+]i) wave elicited by mechanical stimulation and by analyzing the fluorescence recovery after photobleaching (FRAP). Mechanical stimulation of LE-RPE cells triggers Ca2+ influx, mediated by stretch-sensitive cation channels followed by intracellular Ca2+ release. A regenerative [Ca2+]i wave was found with a lower propagation rate in RCS-RPE cells. This rate could be increased by PKC down-regulation. Mechanical stimulation caused a [Ca2+]i increase in the mechanically stimulated (MS) cell followed after a delay by a [Ca2+]i rise in the adjacent cell layers. The intercellular [Ca2+]i wave propagation could be blocked by gap junction blockers such as halothane or PKC activation. An inhibition of the [Ca2+]i-wave propagation similar to that induced by halothane could be observed in cells grown in solutions containing 14 mM or higher concentrations of glucose. PKC down-regulated cells grown in glucose-rich medium did not develop this inhibitory effect on gap junction communication (GJC). FRAP experiments confirmed that the observed changes were consistent with a PKC-mediated inhibitory effect of high glucose concentrations on GJC.

A decreased Ca2+-wave propagation is found among cultured RPE cells from dystrophic RCS rats.

PURPOSE: The authors investigated intercellular communication among cultured rat retinal pigment epithelial (RPE) cells isolated from dystrophic Royal College of Surgeons (RCS) rats by studying the conduction of the [Ca2+]i wave elicited by mechanical stimulation. The effect of protein phosphorylation was measured by modulating the protein kinase C (PKC), protein kinase A (PKA), and tyrosine kinase activity. METHODS: Cultured RPE cells isolated from neonatal control Long-Evans (LE) and dystrophic RCS rats were analyzed using the fluorescent dye fluo-3 to measure the Ca2+-wave propagation on mechanical stimulation to investigate the intercellular communication. RESULTS: Mechanical stimulation in LE-RPE cells resulted in a centrifugally spreading Ca2+ wave through the neighboring cells. When a mechanical stimulus was applied on RCS-RPE cells, a significantly reduced Ca2+-response was found in the neighboring cells compared with that of control RPE cells. Activation of PKC almost completed blocked the mechanically induced Ca2+ rise in the neighboring RCS-RPE cells. In contrast to LE-RPE cells, an activation of PKA also significantly decreased the Ca2+-wave propagation in RCS-RPE cells. Inhibition of PKA had no effect on the intercellular communication in LE- or RCS-RPE cells. In addition, when protein phosphatase activity or tyrosine kinase activity was inhibited, an increased Ca2+ rise in the neighboring cells on mechanical stimulation was measured, reaching levels currently found for LE-RPE cells. CONCLUSIONS: In dystrophic RCS-RPE cells, a decreased intercellular Ca2+-wave propagation is found. This intercellular communication can be mediated by protein phosphorylation.