A comparison of induced astigmatism in 20- vs 25-gauge vitrectomy procedures.

INTRODUCTION: Surgically induced astigmatism is an unwanted variable that can lead to poorer visual and refractive outcomes in patients undergoing vitrectomy even when a technically precise procedure has been performed. This study assesses the difference in surgically induced astigmatism (SIA) between the traditional 20-gauge vitrectomy and the newer 25-gauge sutureless technique by comparing pre- and post-procedure keratometry readings. METHOD: The study is a retrospective consecutive case series of vitrectomies performed by a single surgeon. There were a total of 47 patients, eight with bilateral procedures, 24 who underwent the 20 gauge, and 31 who had the 25-gauge procedure. Patients were excluded for corneal altering pathology or scleral buckling procedures. Vector analysis of pre- and post-vitrectomy readings was performed using Alpin's method, facilitated by the ASSORT program version 4.1. RESULTS: Mean time at which post-operative keratometry readings were taken was 3.9 months (1-36). Mean astigmatism at presentation was 0.63 D and 0.92 D and at post-surgically follow-up 1.14 D and 0.91 D (20 and 25 gauge, respectively). Mean SIA was 0.66 D (SD=0.8 D) for the 20-gauge group and 0.27 D (SD=0.23 D) for the 25 gauge (P=0.037). The calculated figure of SIA variability representing the 95% CI for the maximum amount of SIA for each procedure was 2.26 D and 0.73 D for the 20- and 25-gauge procedure, respectively. CONCLUSIONS: The study shows that the 25-gauge technique involves a statistically significant reduction in the amount of SIA. This can ultimately lead to a better visual and refractive outcome for the patient.

De-misting condensation on intraocular lenses.

BACKGROUND: Condensation occurs rapidly on intraocular lenses (IOLs), particularly silicone IOLs, after vitrectomy and fluid-air exchange in the presence of a posterior capsulotomy and severely limits the surgeon's view of the retina. This study investigated the value of heating contact lens irrigation fluid to prevent condensation on IOLs. DESIGN: An experimental in vitro study and a noncomparative interventional case series. PARTICIPANTS: Five control eyes had temperature measurements during fluid-air exchanges. Two patients with silicone IOLs and posterior capsulotomies underwent a vitrectomy involving a fluid-air exchange with heated contact lens fluid. METHODS: An in vitro model allowed monitoring of temperature and humidity changes during condensation formation on four different IOL materials. Adjusting variables to promote evaporation rather than condensation was achieved in vitro. In vivo, intraocular temperatures were measured at various stages of five vitrectomies involving a fluid-air exchange. Finally, in two in vivo cases a blood warmer was used to heat the accessory contact lens irrigation fluid during the vitrectomy and fluid-air exchange. MAIN OUTCOME MEASURES: Successful prevention of condensation on the silicone IOL during the fluid-air exchange. RESULTS: Anterior segment temperature influences the IOL temperature, such that when it is higher than the posterior segment temperature, condensation does not form and evaporation is promoted. In vivo the temperatures in the eye are hypothermic throughout the vitrectomy. At fluid-air exchange the posterior segment heats rapidly as irrigation ceases and low specific heat gas enters. Finally, in two in vivo cases with silicone IOLs, condensation was predicted then prevented by our intervention for the duration of the fluid-air exchange. CONCLUSIONS: Heating the anterior segment by conduction from warmed irrigation fluid flowing through the irrigating contact lens represents a cheap, noninvasive, and safe means to prevent condensation on IOL materials.

Retrospective study of macular holes treated with pars plana vitrectomy.

BACKGROUND: Tangential vitreo-foveal traction resulting in full-thickness macular hole is an important cause of visual loss. PURPOSE: To determine, correlate and evaluate the factors that affect the anatomical and visual outcome of macular hole surgery. METHOD: Retrospective analysis of all cases of macular hole surgery undertaken by a single surgeon (RDB) between 1995 and 1998. RESULTS: One hundred eyes were analysed with a minimum follow-up of 3 months. One operation anatomical success rate was 95%. Anatomically successful eyes had visual acuity improvement of one or more lines in 73.4% and two or more lines in 66.3%. Failure to remove diaphanous contractile 'epiretinal' membranes (presumably the internal limiting membrane) around the macular hole was significantly associated with anatomical failure (P < 0.001). Improvement of two or more lines of visual acuity was significantly associated with successful anatomical closure of the macular hole (P = 0.001). The success rate was highest in the more recent cases, suggesting a learning curve effect. Postoperatively, cataract developed or progressed in 96% of phakic eyes. Retinal detachment occurred in 6%, with all eyes having the retina reattached following subsequent surgery. Gross retinal pigment epithelial changes at the macula region developed in 3%. CONCLUSION: Meticulous rapid dissection of adherent, diaphanous 'epiretinal' membrane around the macular hole, combined with gas tamponade and postoperative posturing, result in successful anatomical closure with improved visual acuity.

Subretinal perfluorodecalin toxicity.

BACKGROUND: Subretinal injection of perfluorocarbon liquids (PFCL) can occur during vitreoretinal surgery. The long-term effects of this complication are not well established. METHODS: A case report is presented of a patient with retained subretinal perfluorodecalin following retinal detachment repair for a giant retinal tear. RESULTS: In the early postoperative period, the macular retinal pigment epithelium (RPE) became opalescent in appearance and by 2 months postoperatively the patient developed macular RPE atrophy with resulting poor central vision. CONCLUSIONS: Toxicity of subretinal perfluorodecalin causing RPE atrophy is proposed. We recommend all traces of PFCL should be removed if possible.

Intravitreal cilia in phakic penetrating eye injury.

BACKGROUND: Intraocular cilia present clinical perplexity due to their radiolucency, the extremely variable ocular response to such cilia, and the inadvisability of using MRI in cases of suspected metallic intraocular foreign bodies (IOFB). METHODS: Two cases of intravitreal cilia associated with phakic penetrating eye injury are described where preoperative CT scan revealed no retained IOFB. RESULTS: B-scan ultrasonography detected intravitreal cilia in one patient and raised this suspicion in the other. One patient presented with endophthalmitis unresponsive to intravitreal antibiotics, the other with culture-negative anterior uveitis. Both underwent vitrectomy and removal of cilia. CONCLUSIONS: Intravitreal cilia should be considered in penetrating eye injuries even in phakic eyes with no radiological evidence of IOFB, especially if associated with endophthalmitis. B-scan ultrasonography may aid detection of intravitreal cilia and thus alter clinical management.

Perimetric and angiographic effects of retinotomy.

AIM: We sought to characterise the morphological and functional effects of drainage retinotomy on the vascular, neural, subretinal and epiretinal components of the affected retina. PATIENTS AND METHODS: Following successful retinal reattachment surgery involving drainage retinotomy in 15 cases (retinotomy group) and no retinotomy in 14 cases (control group), the existence, nature and quadrantic area of visual field loss to a white III4e target was determined using kinetic Goldmann perimetry. Vascular alterations were characterised using fluorescein angiography with peripheral sequences. RESULTS: Visual field defects within 30 degrees of fixation were present in 12 of 14 (86%) of the retinotomy group (including all eyes in which the retinotomy was sited within five disc diameters of fixation) and none of the control group (Fisher exact test, P = 0.00005). Following superonasal retinotomy, inferotemporal field area (median area 82 units, range 44 to 128) was approximately half that following superotemporal retinotomy (median area 167 units, range 119 to 192) (Wilcoxon's ranksum P = 0.003). No vascular abnormalities distal to the retinotomy were identified, although subretinal neovascularization (two eyes) and epiretinal membrane formation (one eye) occurred at the retinotomy site. CONCLUSION: We recommended that where possible subretinal fluid be drained via existing breaks, and if retinotomy is necessary, that it should be sited more than five disc diameters from fixation in the supertemporal quadrant to minimise visual field loss.

The stability of perfluoro-N-octane during vitreoretinal procedures.

OBJECTIVES: To examine the propensity for intraoperative procedures, such as endolaser, to generate polar impurities in perfluorocarbon liquids, either by degradation of the compound or by dissolution of materials contacting the liquid, given the value of these liquids as adjuncts to vitreoretinal procedures and the importance of using pure and inert liquid. METHODS: Perfluoro-N-octane liquid recovered from patients after vitreoretinal procedures was analyzed by gas chromatography, nuclear magnetic resonance, ultraviolet spectroscopy, and a cell proliferation assay. Similar analyses were performed on pure and impure perfluoro-N-octane exposed in vitro to superclinical energy levels of argon and YAG laser, endodiathermy, and endoillumination. RESULTS: No change in chemical structure and only minor (parts per million) increases in dissolved contaminants were observed. The perfluoro-N-octane liquid retained its inertness as indicated by the inability of fibroblasts to attach and proliferate on its surface. CONCLUSION: The structure and biologic inactivity of perfluoro-N-octane are unaffected by vitreoretinal surgical manipulations.

Macula toxicity after intravitreal amikacin.

BACKGROUND: Although intravitreal aminoglycosides have substantially improved visual prognosis in endophthalmitis, macular infarction may impair full visual recovery. METHODS: We present a case of presumed amikacin retinal toxicity following treatment with amikacin and vancomycin for alpha-haemolytic streptococcal endophthalmitis. RESULTS: Endophthalmitis resolved with improvement in visual acuity to 6/24 at three months. Fundus fluorescein angiography confirmed macular capillary closure and telangiectasis. CONCLUSIONS: Currently accepted intravitreal antibiotic regimens may cause retinal toxicity and macular ischaemia. Treatment strategies aimed at avoiding retinal toxicity are discussed.

Vascular consequences of retinectomy.

OBJECTIVE: To define the vascular sequelae of retinectomy. DESIGN: Clinical and angiographic survey of patients who had undergone retinectomy procedures. PATIENTS: Twenty consecutive patients with ambulatory vision and attached posterior retina after retinectomy procedures underwent ophthalmic examination, including retinal biomicroscopy, indirect ophthalmoscopy with scleral indentation, and peripheral retinal fluorescein angiography. RESULTS: Ten eyes (50%) showed anterior retinal neovascularization (NV), with vessels derived from the ciliary body or posterior retina. Neovascularization occurred in residual anterior retina adjacent to the retinectomy, in detached anterior retina demarcated by laser in quadrants not involved by retinectomy, and in fibrinous membranes extending anterior to the retinectomy edge. This was associated with postoperative vitreous hemorrhages in two patients. Iris NV and inferior iridectomy occlusion were strongly associated with retinal NV (Fisher's exact test, P < .005). No patient had neovascular glaucoma or optic disc NV during a median follow-up of 250 days (range, 121 to 465). CONCLUSIONS: Retinectomy may have profound secondary effects on ocular vascular circulation, resulting in retinal NV in association with iris NV, occlusion of inferior iridectomies, and vitreous hemorrhage. Complete intraoperative removal of residual anterior retina to the ora serrata in quadrants involved by retinectomy, combined with prophylactic retinal laser treatment from the vitreous base to the ora in the remaining quadrants, is recommended to prevent the development of retinal NV and its associated complications.

Retinal detachment complicating scleral-sutured posterior chamber intraocular lens surgery.

Although retinal detachment has been reported in association with sutured posterior chamber intraocular lenses (PCIOL), detailed analysis of the pathogenesis, clinical features and risk factors is lacking. Thirty-nine patients who had undergone surgery for scleral-sutured PCIOL were therefore reviewed, revealing 8 patients with associated retinal tears or detachments. Retinal breaks resulted from vitreous incarceration by the intraocular suture (6), post-operative vitreous detachment (1), preretinal manipulation of the dislocated PCIOL (1), surgical entry-sites (1) and surgical induction of posterior vitreous detachment (1). An axial length > 25 mm was associated with the development of retinal tears (p < 0.05, Fisher's exact test). All patients had attached retina with median visual acuity of 6/12 (range 6/6 to CF) at last follow-up (median 15 months, range 1-41 months). In patients requiring a pars plana approach, careful attention to the posterior hyaloid face, basal gel, surgical entry-sites and suture tract is recommended to reduce the risk of retinal detachment associated with scleral-sutured PCIOL procedures.

Extraconal bupivacaine in scleral buckling procedures.

BACKGROUND: Intraoperative retrobulbar bupivacaine injection provides effective analgesia after scleral buckling procedures performed under general anesthesia, but is associated with significant risks. METHODS: The safety and analgesic efficacy of an extraconal technique using a blunt cannula was evaluated. Forty patients undergoing scleral buckling procedures with general anesthesia were randomized to intraoperative extraconal bupivacaine injection (bupivacaine group. n = 21) or to no such treatment (control group, n = 19). General anesthetic and postoperative analgesia regimens were standardized. Analgesia requirements, pain, nausea, and sedation levels were graded at four intervals the first 24 hours after surgery. Chemosis was assessed 1 day after surgery, and ocular motility was assessed at 1 day, 1 week, and subsequent review. RESULTS: Maximum, 0 to 2-hour, and 4 to 6-hour pain levels were lower in the bupivacaine group than the control group (Wilcoxon rank sum, P < 0.005, < 0.005, < 0.01, respectively). Postoperative analgesia was required within the first 24 hours of surgery by all patients in the control group, but by only 12 of 21 patients (57%) in the bupivacaine group (Fisher's exact test, P = 0.001). Ptosis with minimal supraduction defect was noted at first postoperative examination in two patients who had undergone extraconal bupivacaine injection but resolved within 1 week. No other complication was encountered. CONCLUSION: Intraoperative extraconal bupivacaine injection appears to be a safe and effective method for reducing pain and analgesia requirements after scleral buckling procedures performed under general anesthesia.

Perfluorocarbon heavy liquids.

Perfluorocarbon heavy liquids (PFCL) facilitate the transfer of intraocular fluids and other surgical manoeuvres in the posterior segment. The indications for their use have extended since first described in the management of giant retinal tears and proliferative vitreoretinopathy. We reviewed our personal experience and experimental evidence, including adverse effects, in order to identify the current role of PFCL in vitreoretinal surgery. High-density perfluorocarbon liquids represent a major advance in vitreoretinal surgery. Clinical experience and the results of experimental investigations have demonstrated their efficacy and safety as an intraoperative device.

Detection of functional vision loss using the Ishihara plates.

Many techniques have been described for the detection of functional visual loss. We report four cases in which Ishihara pseudo-isochromatic colour plates gave objective evidence of functional vision loss. In all cases the patients were able to read the first test pattern (No. 12), but could not distinguish any of the following pseudo-isochromatic numbers (plates 2-17). However, they experienced no difficulty in tracing the winding lines (plates 18-24), demonstrating that they in fact had normal colour vision.

Herpes zoster ophthalmicus and the orbital apex syndrome.

Herpes zoster ophthalmicus (HZO) commonly causes isolated ophthalmoplegic syndromes. Visual loss caused by optic neuritis secondary to HZO can be reversible or irreversible. HZO rarely presents as an orbital apex syndrome, when an association with meningo-encephalitis has been reported. We report a case of orbital apex syndrome secondary to HZO treated with systemic steroids and acyclovir. Our patient suffered no systemic complications and displayed a rapid resolution of optic neuropathy. We discuss this case in the light of previous reports and explore the possible pathogenic mechanisms involved.