An experimental study on the effect of encircling band procedure on silicone oil emulsification.

AIM: Silicone oil is a useful tamponading material used in complex vitroretinal surgery. However, the use of silicone oil is associated with emulsification which can lead to vision threatening complications. The authors developed an experimental model to study the effect of encircling band on silicone oil emulsification. METHODS: Two identical artificial eye chambers were constructed with circumferential indentations placed at the sphere's equator (mimicking an encircling band indentation), and filled with varying amounts of Silicone Oil 1000 centistrokes (Adato, Bausch and Lomb, UK) and balanced salt solution. The chambers were then placed on a horizontal rotating shaker, mimicking physiological saccadic eye movements, which spun the chambers at 100 Hz for 5 days at 37 degrees C. Emulsification was then quantified by dark field microscopy, digital photography, and manual counting by a masked observer. RESULTS: The mean (standard deviation (SD)) values of silicone emulsification bubbles were as follows: in the 90% silicone oil filled chamber with no encircling band, 139.1 (SD 313.4); in the 90% silicone oil filled chamber with encircling band, 10.9 (SD 22.2) (p<0.0001); in the 75% silicone oil filled chamber with no encircling band, 103.6 (SD 272.6); in the 75% silicone oil filled chamber with encircling band, 18.5 (SD 32), (p = 0.001). CONCLUSIONS: The emulsification of silicone oil results from friction between the silicone oil and aqueous liquids. The results from this study suggest silicone oil emulsification is reduced by (1) more complete silicone oil fill and (2) indentation from an encircling band. The authors hypothesise that both these measures resulted in reduced emulsification by reducing silicone oil/aqueous movement and resulting shearing forces.

Variations in the morphology of retinopathy of prematurity in extremely low birthweight infants.

AIMS: To investigate the clinical observations that arteriovenous shunts typical of threshold retinopathy of prematurity (ROP) are morphologically different in extremely low birthweight infants weighing less than 1000 g. METHODS: An observational case series of six extremely low birthweight infants displaying specific features of threshold retinopathy of prematurity enrolled between 1998 and 2001 at one centre. The variant morphology was documented with colour photography and fundus fluorescein angiography before laser therapy. RESULTS: Stage 3 threshold ROP in extremely premature infants may be characterised by a different morphology not demonstrating classic shunt formation. A poorly developed capillary bed is present in already vascularised retina in these cases. CONCLUSIONS: This case series of extremely low birthweight infants display variations in the typical morphological appearance of threshold ROP. In these cases, established plus disease may be present in the absence of arteriovenous shunting. Delaying treatment until a classic stage 3 ridge with extraretinal neovascularisation develops may be detrimental to controlling the disease process. The authors propose that the criteria for threshold disease requiring treatment do not accurately apply in this extremely low birthweight group as defined by the CRYO-ROP study and that treatment should be instituted before the typical threshold features arise. Plus disease remains the most reliable sign indicating the need for treatment.

Cryotherapy for retinopathy of prematurity: a MRI study of the surgical-anatomical relationship of the neonatal conjunctival fornices to the globe.

PURPOSE: To demonstrate the surgical-anatomical relationship of the neonatal conjunctival fornices to the globe in order to ascertain whether adequate cryotherapy is possible in infants with stage 3 retinopathy of prematurity using a trans-scleral approach without opening the conjunctiva. METHODS: Magnetic resonance (MR) scans of the orbit were performed on an adult and an infant of 38 weeks post-conceptual age with maximal posterior placement of a MR-compatible replica of the Schulenburg cryoprobe in the nasal and temporal aspects of the globe. RESULTS: In the infant MR scan, the scleral indentation produced by the probe was anterior to the equator on the nasal side and at, or just anterior to, the equator on the temporal side. Nasally, the scleral indentation reached only the more anterior part and not the posterior part of zone 2 and none of zone 1. Temporally, the scleral indentation reached the central part of zone 2 but not the posterior part of zone 2 or zone 1. CONCLUSION: The findings suggest that adequate cryotherapy with a trans-scleral approach without opening the conjunctiva is unlikely to be achieved in the more immature neonate with posteriorly located retinopathy of prematurity. To permit access of the cryoprobe to the more posterior part of the globe, one radial conjunctival incision from the corneal limbus in each quadrant may be required to achieve adequate ablation of the posterior non-vascularised retina in these high-risk infants.

Combined phacoemulsification--vitrectomy surgery: technique, indications and outcomes.

PURPOSE AND METHODS: Cataract extraction may be combined with vitrectomy to improve the operative view and/or enhance post-operative rehabilitation. A retrospective review of the records of all patients undergoing combined phacoemulsification and vitrectomy procedures since 1993 was performed. Surgical technique is discussed. RESULTS: Fifty operations on 49 patients are described. Visual acuity improved overall (mean LogMAR acuity 1.58 +/- 0.74 pre-operatively and 1.17 +/- 0.76 LogMAR post-operatively), with 57% of patients having improved acuity post-operatively. Operative complications were few and post-operative complications were acceptable given the severity of the posterior segment disease. CONCLUSIONS: Combined phacoemulsification-vitrectomy surgery is a viable option in the management of posterior segment disease in the presence of cataract. It has a number of advantages over other approaches, and can be combined with intraocular lens insertion into the capsular bag in most cases.

A review of the spectrum of clinical ocular fundus findings in P. falciparum malaria in African children with a proposed classification and grading system.

Ocular fundus pathology in Plasmodium falciparum malaria is common and has prognostic significance. We have made a collaborative effort to document the ocular features in several populations. Based on examination of 735 patients in Malawi, Kenya and The Gambia by direct and indirect ophthalmoscopy with dilated pupils, we have determined that the 5 distinct clinical features (in order of frequency) include retinal whitening, haemorrhages, unique vessel abnormalities, papilloedema, and cotton wool spots. Photographs and descriptions of these are presented, along with a proposed grading scheme.

Current problems in the management of ROP.

Guidelines for screening for retinopathy of prematurity (ROP) and indications for treatment are well established, but implementation of screening and delivery of treatment may be problematical. We have performed a national survey of 118 specialised units dealing with at risk neonates to audit current practice in Britain and to identify practical problems with screening and with treatment. A screening policy for neonates at risk is in practice at 97% of units, performed by consultant ophthalmologists in 86% of centres. Units referred to specialised treatment centres in 23% of cases. An average of 54 infants at risk of ROP were screened by each of 118 units throughout Britain in 1993, and approximately 3% of these infants underwent treatment for ROP. Cryotherapy was used for treatment in 85% of units, laser photocoagulation in 51% and both treatment modalities were used in 36% of units. Less than 1/4 of the neonatologists polled were of the opinion that they should be trained to screen for ROP themselves. These results show that the screening guidelines have been successfully implemented in Britain, but demonstrate a wide variation in practice. Problems with screening and treatment are discussed.

Retinal detachment in AIDS-related cytomegalovirus retinitis.

Patients with acquired immune deficiency syndrome (AIDS) and cytomegalovirus retinitis (CMVR) are surviving longer due to the use of virostatic medicines and improved treatment of opportunistic infections. As a result, retinal detachment is likely to become an increasingly common cause of visual morbidity in these patients. The incidence and outcome of retinal detachment complicating CMVR was studied at two London AIDS centres. Patients with CMVR were identified prospectively and underwent standard treatment. Retinal detachments were diagnosed during regular follow-up. If retinal reattachment surgery was performed, a standard procedure of vitrectomy and silicone oil internal tamponade was employed. Of 147 patients with CMVR, 41 (28%) developed retinal detachments (47 eyes). Forty-three detachments were rhegmatogenous and 4 were exudative. Fifteen eyes of 9 patients with rhegmatogenous detachments underwent retinal reattachment surgery. Of these, visual acuity remained stable or improved in 12 eyes (80%) in the immediate post-operative period. At the last clinic visit, 8 eyes (53%) maintained a visual acuity of 6/60 or better. The visual results of surgery are good in selected patients, bearing in mind the progressive nature of the underlying disease and poor life expectancy.

Bilateral congenital mydriasis.

A single case of bilateral congenital mydriasis is described. A review of the literature is presented and possible modes of inheritance are discussed.

Measures of capillary permeability in acute falciparum malaria: relation to severity of infection and treatment.

Capillary permeability was investigated in 32 Thai patients aged 14-49 years who had acute falciparum malaria with use of three distinct techniques: quantitation of the urinary albumin/creatinine ratio (ACR), estimation of the transcapillary escape rate of radiolabeled albumin (TER), and retinal photography/fluorescein angiography. Fourteen patients had uncomplicated infections and 18 were severe cases. The severely ill patients had significantly higher ACRs (median, 4.8 mg/mmol; 95% confidence limits, 2.4-19.9 mg/mmol) and TERs (median, 8.3%/h; 95% confidence limits, 6.2-13.2%/h) than the uncomplicated cases (ACR: median, 2.1 mg/mmol; 95% confidence limits, 6.2-13.2%/h) than the uncomplicated cases (ACR: median, 2.1 mg/mmol; 95% confidence limits, 1.0-8.8 mg/mmol; TER: median, 5.9%/h; 95% confidence limits, 3.8-10.6%/h; P = .014 and .042). Both variables were significantly associated with biochemical indices of disease severity including total serum bilirubin levels (rs greater than or equal to 0.398, P less than .025 in each case), but there were no significant differences between ACRs and TERs among comatose and noncomatose patients with severe infections (P greater than or equal to .08). Retinopathy (hemorrhages, cotton-wool spots, capillary nonperfusion, and/or extravasation of fluorescein) was found in eight severely ill patients and in two uncomplicated cases. Fluorescein leakage was evident in six patients. Although fluorescein leakage had the strongest parametric correlation with the presence of coma relative to both ACR and TER in the full patient series (r = 0.58, P less than .01), multiple linear regression analysis indicated that concentrations of plasma lactate (t = 2.998, P = .006) and serum creatinine (t = 2.200, P = .036) were the factors responsible for this association. These data do not support a role for tissue edema in the pathogenesis of cerebral malaria but reveal an association between markers of disease severity and a generalized increase in systemic capillary permeability.

Cryosurgery for acute retinopathy of prematurity: factors associated with treatment success and failure.

Cryosurgery for stage 3 plus acute retinopathy of prematurity (ROP) increases the probability of disease regression, but up to 25% of eyes may progress to retinal detachment and blindness in spite of treatment. In a series of 37 eyes in 23 patients treated at the Hammersmith Hospital an overall 75% of eyes reached a favourable outcome. We present these results in detail and analyse the apparent causes of treatment failure. Poor anatomical results (total retinal detachment and traction detachment involving the macula) were associated with inappropriate cryoprobe design and with zone 1 and rush-type disease. Poor functional results in the presence of a largely flat retina (marked macular ectopia and high myopia) appeared to be associated with delayed treatment during the period of evolution of the stage 3 lesion, and with the appearance of a more highly differentiated vascular shunt with early localised forward vitreous invasion. Suggestions for the refinement of existing gradings of acute ROP are made.

Vaso-occlusive retinopathy in the primary anti-phospholipid antibody syndrome.

We report two patients with contrasting patterns of retinal vascular occlusion associated with the primary anti-phospholipid antibody syndrome. The immuno-pathological features and clinical associations are discussed. This condition is of interest to ophthalmologists because of its association with thrombosis in the eye, brain and elsewhere and because it provides new insights into the pathogenesis of retinal vascular disease in young patients.

Surveillance for retinopathy of prematurity in practice: experience from one neonatal intensive care unit.

We have reviewed the results of a six year surveillance programme for acute Retinopathy of Prematurity (ROP) in order to see how the yield of cases reaching clinically significant stage 3 can safely be maximised, and to assess the effectiveness of an examination technique which does not require a speculum or scleral indentation. An overall 137 (44.8%) developed some signs of ROP and 35 (10.8%) reached stage 3. Seventeen of these were born at 25 weeks or less gestational age, and included four with rush-type disease. None of those born at or over 30 weeks developed stage 3. It is concluded that infants born at 31 weeks or more do not need to be included in a surveillance program, and this protocol will increase the yield of significant disease. In addition, cases of stage 3 which may require cryosurgery will not be missed using an atraumatic examination technique.

Clinical factors associated with retinopathy of prematurity.

In the period from September 1983 until June 1986 a prospective study was carried out to determine the incidence and severity of retinopathy of prematurity in inborn infants of less than 1500 g at birth and the risk factors associated with the development of retinopathy of prematurity in infants of less than 31 weeks' gestation. One hundred and forty four infants were eligible for inclusion in the study. Altogether 140 infants of less than 1500 g birth weight were examined, 42 (30%) of whom developed retinopathy of prematurity. Fifteen of these infants had progression to advanced disease (stage III or stage IV). One hundred and seventeen of the infants were of less than 31 weeks' gestation and 34 (29%) of them developed retinopathy of prematurity. Thirty four risk factors shown previously to be associated with the development of the disease were collected prospectively and analysed using multiple logistic regression analysis to determine the independently significant variables. Three risk factors: acidosis, the number of times that the pH was less than 7.2; hyperoxia, the number of times that arterial oxygen tension was greater than 12 kPa; and gestational age were found to be independently associated with the development of retinopathy of prematurity in these infants. These findings suggest that acidosis may be an important aetiological factor in the pathogenesis of this disease.

Foscarnet as treatment for cytomegalovirus retinitis following bone marrow transplantation.

This report describes a patient with chronic granulocytic leukaemia who developed cataracts on busulphan treatment. Following allogeneic bone marrow transplantation, he developed cytomegalovirus retinitis, which was treated successfully with trisodium phosphonoformate (foscarnet). Cytomegalovirus retinitis and its therapy, and busulphan-induced cataract are discussed.

Natural history of retinopathy of prematurity.

Sixty-nine infants at risk of developing retinopathy of prematurity (ROP) were entered into a prospective study to assess the incidence and natural history of the disease. Seventeen infants developed ROP, and in six eyes the disease progressed to stage IV ROP. The natural regression of a pupillary membrane and physiological vitreous haze was not influenced by the onset of ROP. Progression from stage I to stage III was rapid and the rate was influenced by the zone affected. Congestion and tortuosity of vessels in the posterior pole always signified stage III ROP. Progression from stage III to stage IV ROP was slower; it was characterised by the development of vitreoretinopathy, signified by the sudden onset of a vitreous haze. Iris congestion associated with poor mydriasis may be a grave sign indicating imminent retinal detachment. Cicatricial ROP can be divided into retinal and vitreoretinal cicatricial disease directly related to the stage of active disease reached. ROP is characterised by its self limiting nature, but the stage at which it becomes inactive varies and will influence the final outcome.