Scanning electron microscopic findings on intraocular metallic foreign bodies

· Background: The study reported here was performed to investigate morphologic intraocular reactions on the surface of metallic intraocular foreign bodies (IOFB) with scanning electron microscopy. · Methods: Twenty-seven extracted IOFB were investigated. Of these, 22 were situated in the vitreous body; 19 had contact with the retina. Five IOFB had been removed from the anterior segment (control group). The duration of intraocular retention was 6 h to 24 days. Immediately after microsurgical removal the IOFB were fixed, dehydrated, dried, sputter-coated and investigated with a scanning electron microscope. Two IOFB from the vitreous were treated for collagen preservation.  · Results: Eighteen of 20 intravitreal IOFB showed fibers of fibrin on its surface; 11 of 20 were covered with a homogeneous layer. Within this layer a net of collagen fibers was detectable. A major cellular reaction was observed only on IOFB that injured the retina, pigment epithelium and choroid. · Conclusions: This morphologic study shows that: (1) a fibrin net develops in the vitreous around intravitreal IOFB; (2) depositions of amorphous material into the spaces of this net lead to dense coverage of the IOFB; (3) cellular reactions are not condition for the development of this coverage; (4) laceration of the retina induces a fibrocellular response. Received: 16 September 1997 Revised version received: 9 December 1997 Accepted: 10 December 1997     

Detection of neurone-specific enolase in long-term cultures of human corneal endothelium

· Background: Human corneal endothelial cells cultivated in monolayer culture for protracted periods undergo morphological dedifferentiation, whereby they assume a more fibroblast-like appearance. These cultures may also become overgrown with contaminating stromal fibroblasts and/or with keratocytes, when non-selective media are employed, thus rendering identification of actual endothelial cells difficult on a strictly morphological basis. · Methods: The endothelium of the human cornea stains for neurone-specific enolase (NSE) in situ, and we therefore wished to study the expression of this marker in primary and long-term monolayer cultures of these cells. Ten such cultures were established, six being stained for NSE at the primary and first-passage stage, the other four for 6, 8, 10 and 12 months. The NSE-staining pattern manifested in co-cultures of corneal endothelium and fibroblasts or keratocytes (first to fifth passage cultures) was also investigated, and co-cultures established from each of the latter two cell types served as controls. · Results: In monolayers of corneal endothelium which had retained their cobblestone-like morphology, NSE could be demonstrated even after more than 20 passages, which amounted to 1 year in culture. Dedifferentiated or degenerating endothelial cells stained poorly and inhomogeneously. Control cultures of fibroblasts or keratocytes were consistently NSE-negative, and when each of these cell types was co-cultured separately with corneal endothelium, only the latter expressed the marker protein. · Conclusion: Since antibodies against NSE are commercially available, practical use may be made of this marker protein for confirming corneal endothelial status in long-term cultures. Received: 11 August 1997 Revised version received: 13 October 1997 Accepted: 15 October 1997     

Retinal sensitivity measurement over drusen using scanning laser ophthalmoscope microperimetry

· Background: Retinal sensitivity over drusen was examined using a scanning laser ophthalmoscope to confirm a previous report of no change in sensitivity over drusen. · Methods: Microperimetry was performed using a scanning laser ophthalmoscope in 23 eyes of 19 subjects. Subject age ranged from 42 to 86 years (mean 68.5 years). Fifty-four drusen bigger than the diameter of a major retinal vein at the optic disc rim were examined, and drusen were classified as soft drusen and other large drusen. · Results: Nine eyes of eight subjects showed a decrease in retinal sensitivity over drusen. The decrease in retinal sensitivity was more than 5 dB less than the sensitivity at a peripheral non-drusen area peripheral to the measurement point. The sensitivity decrease was noted over 15 of 29 large drusen and the decrease was statistically significant (P<0.02). However, no relationship between the size of the drusen and the amount by which sensitivity decreased was found. Nevertheless, a decrease in retinal sensitivity was not seen over any of 25 soft drusen. · Conclusion: Large drusen may influence retinal sensitivity and function. Received: 20 February 1997 Revision version received: 20 June 1997 Accepted: 5 August 1997     

Extracellular matrix of opacified anterior capsule after endocapsular cataract surgery

· Background: We determined the types and distribution of glycosaminoglycans (GAGs) and collagens, in anterior capsular opacification after endocapsular phacoemulsification and aspiration (ECPEA) and intraocular lens implantation. · Methods: Opacified anterior capsules were removed from human eyes after ECPEA. Immunohistochemical staining was performed to determine GAGs with monoclonal antibodies to chondroitin, chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), dermatan sulfate (DS), and keratan sulfate (KS); collagens with monoclonal antibodies to types I, II, and III collagens; and cellular characteristics with monoclonal antibodies to vimentin, desmin, α-smooth muscle actin, and cytokeratin. Decorin mRNA and type I collagen mRNA were detected by in situ hybridization. · Results: In the capsules, the C6S, DS, KS, and types I and III collagens were similar to the chemical components found at the adhesion site of the anterior and posterior capsules after extracapsular cataract extraction, and cellular components contained vimentin, desmin, α-smooth muscle actin, cytokeratin, decorin mRNA, and type I collagen mRNA. · Conclusions: The GAGs and collagens in opacified anterior capsule after ECPEA were similar to those found during wound healing, although KS is present in normal anterior segment tissue during development and only in the cornea postnatally. These chemical components may be produced by myofibroblast-like cells presumably transformed from lens epithelial cells. Received: 4 August 1997 Revised version received: 6 October 1997 Accepted: 16 October 1997     

Complications of surgery for epiretinal membranes

· Purpose: Surgery has been successful in removing epiretinal membranes (ERM) from the macula, allowing some improvement in vision in 80–90% of patients; however, complications are relatively frequent. We conducted a retrospective study to evaluate the rate of peri- and postoperative complications and their influence on functional outcome of eyes having been operated on for ERM. · Material and methods: Preoperative findings, intraoperative and postoperative complications as final results of 70 consecutive cases of idiopathic or secondary ERM operated on by the same retina surgeon were analyzed. · Results: In all cases the ERMs were succesfully removed from the fovea. The mean visual acuity (VA) increased from 0.34±0.2 to 0.54±0.31 (P<0.05) postoperatively. Idiopathic and secondary ERM both showed significant improvement after surgery. Complications included intraoperative hemorrhage and retinal tears and postoperative progressive nuclear sclerosis, retinal tears causing detachments, macular edema and retinal pigmentary epitheliopathy. Final VA was not significantly different from the mean after complications, apart from when retinal detachments involved the macular area. · Conclusions: Performing surgery for ERM is worthwhile in eyes with major decreased VA and in eyes with metamorphopsia but only moderately reduced vision. Postoperative complications are frequent but can usually be managed successfully. Of them, only retinal detachment has a negative effect on the final functional outcome. Received: 8 July 1997 Accepted: 20 November 1997     

Reproduction of antiviral effect in an in vivo model of human cytomegalovirus retinal infection

· Background: Cytomegalovirus retinitis remains a serious problem in AIDS patients, and the species specificity of human cytomegalovirus (HCMV) has hindered the development of animal models suitable for testing new therapeutic agents. Having previously described an in vivo model of HCMV retinal infection, we investigated its ability to reproduce the antiviral effects of the established anti-HCMV agent ganciclovir in order to determine the model’s potential for evaluating novel agents. · Methods: Athymic rats had human fetal retinal tissue implanted in both anterior chambers. At 14 or 28 days post implantation, a suspension of a β-galactosidase (lacZ⁺) mutant of HCMV was injected into each anterior chamber. Commencing 3 days prior to the injection of virus, rats in the treatment group received twice-daily intraperitoneal injections of ganciclovir (≡ a total of 100 mg/kg per day) for the duration of the study. The control rats received no drug. Twenty days after virus injection, the eyes of all rats were removed, sectioned and developed with X-gal substrate to detect any β-galactosidase expression in the human tissue implants. · Results: Blue-staining foci of infection were detected in the implanted retinal tissue in 8 of 10 eyes from untreated control rats, but no β-galactosidase expression was found in any of 12 eyes from animals which had received ganciclovir treatment. · Conclusion: Intraperitoneal administration of ganciclovir successfully prevented HCMV replication in the intraocular retinal implants. This model of HCMV retinal infection is therefore suitable for preliminary evaluation of systemically administered antiviral agents. Received: 21 July 1997 Revised version received: 3 November 1997 Accepted: 11 November 1997     

Effect of exposure to balanced salt solution upon the hardness of the crystalline lens

· Background: The nucleus confers most of the hardness upon the lens, water content decreases towards the centre of the nucleus and a relative dehydration accompanies increased hardness in some cataractous lenses. It is a possibility that exposure and incubation of the inner layers of the nucleus to balanced salt solution (BSS) can result in the softening of the nucleus. · Purpose: This study aimed to investigate the effect of BSS upon the lens hardness. · Methods: Nuclear colour element of cataract was graded biomicroscopically. Following extracapsular cataract surgery the lens nucleocortex was divided into two equal parts and each half was allocated randomly to incubation in BSS or air for 5 min before the hardness of each section was assessed by an automated guillotine. · Results: Following incubation with BSS the mean force necessary to bisect the lens was 0.50 N and in the control air group the mean force was 0.64 N. The lenses in the BSS-treated group were consistently softer than those in the control group, with a mean softening of 18.3% (P=0.001). The amount of softening was not related to the nuclear colour (P=0.6) or age (P=0.1). · Conclusion: Softening of the lens through physical disruption has previously been reported. This study describes the phenomenon of nuclear softening following exposure to BSS, indicating that lens softening can occur through biochemical means. Received: 3 April 1997 Revised version received: 18 August 1997 Accepted: 9 September 1997     

Retinal capillary density in patients with arterial hypertension: 2-year follow-up

· Background: Arterial hypertension is known to be an important risk factor for cerebral and cardiovascular disease. Previous studies have demonstrated a decrease of capillary density in the perifoveal network in tandem with decreased capillary flow velocity in patients with essential hypertension. In a prospective study we quantified the retinal microcirculation in order to evaluate the time course of changes in the perifoveal network. · Methods: Thirty-three patients with essential hypertension (mean age 45±14 years) underwent videofluorescein angiographic studies at baseline and at 2 years (28±6 months) thereafter. The angiograms were obtained with a scanning laser ophthalmoscope and were digitally recorded. By means of digital image analysis we quantified off-line the mean area of perifoveal intercapillary areas (PIA) and the mean capillary flow velocity. · Results: At baseline, the patients with hypertension showed significantly increased PIA and a significantly decreased capillary flow velocity compared with reference values. During the follow-up period the capillary flow velocity decreased further significantly, whereas the PIA showed no significant change. · Conclusions: The continuous decrease of capillary flow velocity demonstrates a progression of altered microcirculation in patients with essential hypertension whose blood pressure was believed to be well controlled. Further studies with this technique may be useful to determine the influence of antihypertensive therapy and may help to identify patients at risk for cerebrovascular events. Received: 14 January 1997 Revised version received: 15 September 1997 Accepted: 29 September 1997     

Is visual field evaluation using multiple correlations and linear regressions useful? An evaluation of Delphi perimetry

· Background: Delphi perimetry is a method of visual field examination which produces a statistical estimation of the visual field by testing only four critical points of the central visual field. This study was performed to evaluate this technique for the detection of glaucomatous field loss. · Method: Patients with glaucoma and ocular hypertension underwent Delphi perimetry and Humphrey visual field analysis (HVFA) program 24-2. The visual field results of both examination were compared. · Results: Of 262 eyes from 199 patients, 120 eyes showed glaucomatous defects by HVFA and 142 were normal. Delphi perimetry showed abnormal visual fields in 107 eyes, 13 of which were false-positive results as Humphrey visual fields were normal. Delphi classified 155 fields as normal, of which 26 were false negatives as Humphrey visual fields showed glaucomatous defects. Therefore, the sensitivity of Delphi perimetry for the detection of glaucomatous visual field defect was 78% and the specificity was 91%. In the 26 false-negative eyes, the most common defect missed was an isolated paracentral scotoma or an early nasal step. Furthermore, 27 of the 94 glaucomatous eyes classified as abnormal by Delphi had defects estimated by Delphi perimetry that corresponded poorly to the field loss demonstrated by Humphrey visual field analysis. Therefore, qualitative sensitivity and specificity of Delphi perimetry for producing an accurate representation of the location, extent and defect depth of glaucomatous visual field loss would be 48.8% and 72% respectively. · Conclusion: In this study Delphi perimetry failed to give an accurate statistical estimation of the visual field in an unacceptably high number of cases; therefore, it cannot be recommended for clinical use. Received: 12 June 1997 Revised version received: 11 November 1997 Accepted: 13 November 1997     

Long-term outcome of primary glaucoma triple procedure with adjunctive 5-fluorouracil

· Purpose: To evaluate the long-term effect of adjunctive subconjunctival 5-fluorouracil (5-FU) on the filtration outcome of primary glaucoma triple procedure (PGTP) in primary open-angle glaucoma (POAG) patients. · Methods: Seventy-four POAG patients were randomly assigned to PGTP alone (36 patients) or PGTP with adjunctive subconjunctival 5-FU (5.0 ± 1.3 injections of 5 mg each, total of 24.8 mg) (38 patients). After surgery, the patients were examined at regular intervals for intraocular pressure (IOP), visual acuity, medical therapy requirements, and complications. Surgical success was defined as IOP ≤20 mmHg on postoperative medication ≤1 without additional glaucoma surgery. · Results: Over an average follow-up (±SD) of 45.3 ± 25.0 months, both 5-FU and control groups maintained significant improvement of IOP control and visual acuity. However, there were no statistically significant differences between the 5-FU and control groups with respect to postoperative IOP, number of glaucoma medications, visual acuity outcome, and success rate overall or in selected patients with one or more of the risk factors for filtration failure. · Conclusions: The use of low-dose subconjunctival 5-FU (mean dosage of 24.8 mg in 5.0 ± 1.3 injections) as an adjunct did not significantly improve the long-term filtration outcome of PGTP in POAG patients. Received: 29 July 1997 Revised version received: 10 October 1997 Accepted: 15 October 1997     

A comparative investigation of FK506 and cyclosporin A in murine corneal transplantation

· Background: Acute rejection is the cause of over 50% of transplant opacifications in some immunological high-risk groups. More potent immunomodulating substances must be found in order to allow extended or individualised therapeutic options for combating rejection. · Methods: Rats of the inbred strains Brown Norway and Lewis were used as donors and recipients, respectively. FK506 (Prograf) was administered intraperitoneally for 14 days in a dosage of 0.3 mg/kg bw, and cyclosporin A (CSA; Sandimmun) was administered, likewise for 14 days, in an intramuscular dosage of 10 mg/kg bw. The transplants were examined every 3rd day by slit-lamp microscopy. Every transplant was subjected to histological or immunohistological evaluation. · Results: The average transplant survival period in the allogeneic strain combination was 7.9 days (SEM=1.1). Therapy with FK506 led to a statistically significant prolongation of transplant survival to 17.1 days (SEM=1.5, P<0.05). Therapy with CSA delayed transplant rejection to 21 days (SEM=0.0, P<0.05). No statistically significant difference was found between the two therapeutic regimens. There were no significant histomorphologic differences in rejected grafts in the FK506- and CSA-treated animals. · Conclusions: In this study we have shown that FK506 is able to delay corneal allograft rejection at a much lower dosage than CSA without a higher incidence of side effects related to toxicity or overimmunosuppression. Received: 8 September 1997 Revised version received: 16 December 1997 Accepted: 13 January 1998     

Appearance and rapid growth of retinal tumor (reactive astrocytic hyperplasia?)

· Background: Tumors of the retina are often seen in association with systemic syndromes such as neurofibromatosis, tuberous sclerosis, and von Hippel-Lindau disease. These masses are either astrocytic hamartomas or capillary hemangiomas. Retinal tumors unassociated with other systemic disease have also been reported. · Methods: The ophthalmologic evaluation and clinical course of a 65-year-old woman who developed an epiretinal membrane followed by a vascularized retinal mass in the macular area are described. · Results: Appearance and rapid growth of the lesion were documented with fundus photography and fluorescein angiography. The lesion was treated with photocoagulation following growth that threatened the foveal region. Choroidal neovascularization subsequently developed toward the fovea, and visual acuity has remained poor. After 4 years of follow-up no local recurrence or systemic disease possibly related to the tumor has occurred. · Conclusions: This is the first report of documented appearance and rapid growth of a retinal tumor that resembles a reactive astrocytic hyperplasia. Received: 30 October 1996 Revised version received: 22 October 1997 Accepted: 6 November 1997     

Toxoplasmic retinochoroiditis: resolution without treatment of the perilesional satellite dark dots seen by indocyanine green angiography

· Purpose: Satellite dark dots (SDD) seen by indocyanine green angiography (ICGA) around the main retinochoroiditis focus are described in 75% of cases. Whether SDDs represent subclinical infectious foci or just a perilesional inflammatory reaction is not known. The purpose here was to report a case giving additional information on this question. · Methods: We analysed the evolution of ICGA SDDs in a patient with recurrent toxoplasmic retinochoroiditis who received no anti-toxoplasmic treatment because the lesion was located outside the areas where treatment is classically recommended. · Results: The patient had a recurrence of retinochoroiditis on the nasal aspect of the disc about 2 disc diameters away from the disc. It was decided to observe the recurrence before introducing treatment. Diminution of SDDs occurred by 3 weeks after the initial ICGA, and complete resolution was observed on a follow-up ICG angiogram obtained 8 weeks after the initial visit. · Conclusion: Resolution of ICGA SDDs in toxoplasmic retinochoroiditis seems to occur in a similar fashion whether or not the retinochoroiditis is treated by anti-toxoplasmic drugs, indicating that SDDs probably represent a non-infectious perilesional inflammatory reaction. Received: 8 September 1997 Accepted: 22 September 1997     

Characterization of multi-input electroretinogram using normal control subjects

· Background: The multi-input electroretinogram (ERG) has recently been developed to analyze focal retinal responses in the central region and is expected to become a powerful tool for management of retinal diseases. The relationship between the obtained ERG response and retinal neuronal functions is not yet fully understood. · Method: In the present study, in order to study the spatial retinal functions; multi-input ERGs were recorded from 14 healthy subjects under several illumination conditions modulating photoreeptor functions. · Results: The first-order kernel amplitudes were changed in correspondence to the cone photoreceptor adaptation states under different background illuminations. A strong flash exposure significantly lowered the amplitude (approximately 70%) within the central 15 deg but lowered it only slightly (10–20%) in the peripheral areas outside the central 15 deg. Similar effects were observed when the stimulus luminance was lowered by neutral density filters. · Conclusion: Our data suggest that a newly developed multi-input measurement of ERGs represents signals within the firing of postreceptor neurons from cone photoreceptors at specific areas. Thus, this analysis is a useful tool for mapping the spatial network of neurons in the central region. Received: 15 September 1997 Revised version received: 2 February 1998 Accepted: 3 March 1998     

Age-related deterioration of motion perception and detection

· Purpose: The purpose of this study was to evaluate the effect of aging on motion detection and perception. · Methods: Forty-six subjects, ages 19–92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick. · Results: Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction. · Conclusion: The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway. Received: 14 April 1997 Revised version received: 25 June 1997 Accepted: 5 August 1997     

Thalidomide inhibits corneal angiogenesis induced by vascular endothelial growth factor

· Background: Ocular diseases caused by neovascularization are among the leading causes of blindness. No specific pharmacological treatment is available. Among potential drugs, thalidomide deserves special interest since a wide body of clinical experience exists. However, its antiangiogenic effect is controversial. We therefore investigated the effect of thalidomide on corneal angiogenesis induced by vascular endothelial growth factor (VEGF), which has a special role among angiogenic growth factors. · Methods: Corneal neovascularization was induced in NZW rabbits by an intrastromal pellet loaded with 500 or 750 ng VEGF. Animals received two daily feedings of 200 mg/kg thalidomide. · Results: Significant inhibition of corneal angiogenesis (P<0.0001) was caused by the teratogenic dose of thalidomide after the 5th day of treatment and persisted for more than 16 days. No obvious side effects were recorded. · Conclusions: Thalidomide has a significant antiangiogenic effect against VEGF-induced neovasclar growth. Together with earlier findings this observation indicates that the drug inhibits two angiogenic pathways which are mediated through integrin adhesion molecules. Received: 7 April 1997 Revised version received: 31 July 1997 Accepted: 18 August 1997     

Prolongation of corneal allograft survival by an interleukin-2-immunoglobulin fusion protein in mice

· Background: Interleukin 2 (IL2) production by activated T-helper cells leads to activation and proliferation of cytotoxic T cells. Recently, an IL2-IgG fusion protein was found to suppress cell-mediated and humoral immune responses in mice. · Methods: We used the genetically engineered murine IL2-IgG2b fusion protein in a fully MHC-mismatched mouse keratoplasty model. The DTH reaction against sheep red blood cells was investigated as a measure of IL2-IgG2b-mediated immunosuppression. The animals were divided into three control groups (n≥6) [no treatment, subconjunctival (SQ) treatment with saline or mouse serum], two IL2 SQ-treated groups (14 μg or 140 μg), and four IL2-IgG2b-treated groups (14 μg, 140 μg or 280 μg SQ or 280 μg IP). · Results: Administration of 20 μg of IL2-IgG2b twice daily from the time of immunization until the time of challenge resulted in almost complete prevention of footpad swelling. The 140 μg SQ application of IL2 (allograft reaction on day 20.5 ± 4.04) and the 280 μg SQ (day 19.2 ± 2.48) or IP (day 19.7 ± 1.5) application of IL2-IgG2b fusion protein significantly prolonged the corneal graft survival in comparison to the untreated group (day 13.4 ± 1.35) (P<0.01) or saline control group (P<0.01) and the mouse-serum-treated group (day 14.7 ± 3.5) (P<0.05). · Conclusion: Our results indicate that, at a total dose of 280 μg, the fusion protein IL2-IgG2b causes no detectable side effects and very effectively suppresses the immune response of the corneal allograft in mice. This fusion protein could prove useful in the treatment of allograft rejections and autoimmune diseases. Received: 22 May 1997 Revised version received: 8 October 1997 Accepted: 3 November 1997     

Comparison of two fixed combinations of latanoprost and timolol in open-angle glaucoma

· Objective: To compare the intraocular pressure (IOP)-reducing effect of the fixed combinations of timolol 0.5% and latanoprost 0.001% or 0.005% after 4 weeks’ treatment. · Design: Following a 1-week run-in period on timolol 0.5% once daily, 139 patiens were randomized to once-daily treatment with a fixed combination of timolol 0.5% and latanoprost 0.001% (comb. 10) or latanoprost 0.005% (comp. 50) or to the individual monotherapies. The IOP was measured at inclusion and at 8 a.m., noon and 4 p.m. on days 1, 7 and 28. · Results: Comb. 10, comb. 50, latanoprost and timolol reduced IOP by 3.7, 6.1, 4.9 and 2.1 mmHg, respectively, from a baseline mean diurnal IOP (±SEM) of 24.8±0.5, 24.1±0.4, 25.2±1.2 and 24.8±0.9 mmHg, respectively. The difference in IOP reduction was significant between comb. 50 and comb. 10 (P<0.001), latanoprost (P=0.046) and timolol (P<0.001) in favor of comb. 50. There was also a significant difference between latanoprost and timolol (P=0.007), in favor of latanoprost. All treatments were generally well tolerated. · Conclusion: This study indicates that a fixed combination of latanoprost 0.005% and timolol 0.5% could be useful in the treatment of glaucoma. Received: 6 October 1997 Revised version received: 16 December 1997 Accepted: 7 January 1998     

Quantification of intraocular retained perfluorodecalin after macroscopic complete removal

· Background: A study was performed to determine the amount of intraocular retained perfluorodecalin after macroscopic complete removal. · Material and methods: Freshly enucleated pig eyes had the anterior segment removed, vitrectomy was carried out, and the eye cups were placed in 0.9% buffered saline solution. One millilitre of perfluorodecalin was instilled for 30 min, followed by a fluid-air exchange. Perfluorodecalin was macroscopically removed. The retina was rinsed twice with 0.9% buffered saline solution. In a second group no rinsing was done, while in a third group no fluid-air exchange was performed. Finally all eye cups were filled with 2.0 ml of the perfluoropolyether Hostinert 130 to dissolve retained perfluorodecalin. The quantity of perfluorodecalin in perfluoropolyether was determined by gas chromatography. · Results: Retained perfluorodecalin was detected in all experiments. The smallest portion of perfluorodecalin retained (range 0.04–0.08, mean 0.058%, SD ±0.015%) was observed without fluid-air exchange. After fluid-air exchange the portion with rinsing was 0.11–0.27% (mean 0.21%, SD ±0.059%) and that without rinsing was 0.51–0.69% (mean 0.60%, SD ±0.065%). · Conclusions: Even after macroscopic complete removal of perfluorodecalin a thin layer remains on the retina. If intraoperative fluid-gas exchange is necessary, multiple rinsing with 0.9% buffered saline solution should be performed to reduce the amount of perfluorocarbon liquid retained. Received: 4 November 1997 Revised version received: 22 January 1998 Accepted: 27 February 1998