Risk factors for strabismus in children born before 32 weeks' gestation.

AIM: To investigate risk factors associated with strabismus in children born prematurely. METHODS: Prospective study of all children born before 32 weeks' gestation between 1 January 1990 and 31 December 1991 in a geographically defined population of approximately 3 million in the Northern Region of the United Kingdom. All children were examined aged 2 years by the same ophthalmologist and paediatrician. RESULTS: 558 children (98.6% of study group) were examined. Logistic regression showed an increased risk of strabismus in children with cicatricial retinopathy of prematurity (p=0.02), refractive error (p=0.003), family history of strabismus (p<0.0001), and poor neurodevelopmental outcome (p<0.0001), in particular impaired locomotor skills (p=0.008) and hand-eye coordination (p=0. 001). Gestational age and regressed acute ROP were not independent risk factors for strabismus (p=0.92 and 0.85 respectively). CONCLUSIONS: This study has identified factors which are independently related to strabismus (although not necessarily causative) and others which are related only indirectly. This may contribute both to the management of children born prematurely and to future studies of the aetiology of strabismus.

Regionalisation of retinopathy of prematurity (ROP) screening improves compliance with guidelines: an audit of ROP screening in the Northern Region of England.

AIMS: This project was designed to determine whether a coordinated regional strategy can improve the implementation of national guidelines for screening for retinopathy of prematurity (ROP), and to identify causes for failure of compliance. METHODS: Retrospective case note audit relating to two periods, 1990-1 and 1994, involving all 17 neonatal intensive care units in the Northern Region of England. Between the two periods, a regional strategy was instituted in an endeavour to improve compliance. Babies born in or admitted to the units during the study periods who were eligible for ROP screening were included. Screening performance was assessed against a standard of 100% compliance with the guidelines. In the second audit period compliance with subsidiary standards was also measured, and reasons for failure were identified. RESULTS: Compliance improved from 47% (262/558) in the first audit cycle to 73% (264/360) in the second. Subgroup analysis in this second cycle indicated better compliance (93.3%) in higher risk babies (< or = 29 weeks' gestational age). Babies transferred between units, discharged home before screening, or who failed to qualify for screening on one of the two defined criteria, were more likely to be missed. CONCLUSION: A carefully implemented regional approach to screening resulted in a higher uptake for babies most at risk. Simple recommendations are made to achieve further improvement in compliance with the guidelines. The wider implications for screening in other conditions and in other areas and specialties are highlighted.

Resistance of the human posterior lens capsule and zonules to disruption.

PURPOSE: To determine the resistance of the human posterior lens capsule and zonules to disruption during cataract surgery. SETTING: Wet lab at Walkergate Hospital, Newcastle upon Tyne, England. METHOD: Human donor eyes were obtained after removal of a corneoscleral disc. Lens extraction was performed by an extracapsular technique leaving an intact capsular bag. The resistance of the zonules and posterior capsule to disruption by aspiration was measured in each eye, and the resistance of the zonules to damage from direct mechanical stretch was determined. RESULTS: Posterior capsules tolerated a median suction pressure of 200 mm Hg (range 150 to 300 mm Hg) before disruption. Values for female eyes were slightly greater than for male; no significant correlation with age was shown. The zonular fibers tolerated a median suction pressure of 200 mm Hg (range 150 to 300 mm Hg). The median mechanical zonular stretch tolerance was 3.00 mm (range 2.75 to 4.00 mm). No significant correlation was found between zonular suction tolerance or stretch tolerance and sex or between suction tolerance and age, but a negative relationship was noted between maximum tolerated stretch and age. CONCLUSION: Setting the maximum aspiration pressure during irrigation/aspiration to 150 mm Hg should help prevent capsular or zonular rupture. If more powerful aspiration is required, it should be used with great care so as not to engage the capsule.

Does vitreoretinal surgery under local anaesthesia result in missed fellow eye pathology?

PURPOSE: There has been a significant increase in the number of vitreoretinal procedures being performed under local anaesthesia over the past few years. This trend is expected to continue. This study was performed to investigate whether by undertaking retinal detachment surgery under local anaesthesia fellow eye examination was compromised. DESIGN: This was a prospective, consecutive, blind, observational study. SETTING: This study was performed at a tertiary referral vitreoretinal unit in a teaching hospital. STUDY POPULATION: In all, 108 consecutive patients undergoing retinal detachment surgery under general anaesthesia were included. OBSERVATION PROCEDURES: Patients were examined independently by different retinal surgeons pre- and intraoperatively. MAIN OUTCOME MEASURES: The findings of the two examiners were compared and differences were analysed. RESULTS: There were 108 patients in this study, 57 of these were males and 51 females. The mean age was 59.01 years (range 16-91). Of these 108 eyes, 48/108 (49.08%) the preoperative examination was regarded as unsatisfactory by the examiner. Over 34% of eyes had fellow eye pathology when examined preoperatively but there were nine (8.33%) eyes in which additional lesions were found intraoperatively. CONCLUSION: General anaesthesia should be considered for patients in whom preoperative fellow eye examination is unsatisfactory.

Retinopathy of prematurity in practice. I: screening for threshold disease.

AIMS: To review an 11-year period of screening for retinopathy of prematurity (ROP) in the north of England by a single ophthalmologist. To identify the gestational ages and birth weights of babies reaching different stages of ROP. To investigate the workload involved in screening to detect threshold ROP, and that the practical outcomes had narrower inclusion criteria for screening. To identify babies treated for threshold disease. METHODS: During the period August 1987-October 1998, babies were screened according to the national guidelines and the results were prospectively entered onto a computerised database. These data were then systematically reviewed. RESULTS: Data were available for 484 babies: 203 (41.9%) developed any ROP, 46 (9.5%) reached stage 3 ROP, and 25 (5.2%) reached threshold and were treated. Data on 425 babies showed them to require an average of 2.3 screening examinations per baby. It took an average of 39 screening examinations to detect one case of threshold ROP. The more premature and lighter birth weight babies required the most examinations. Therefore, restricting the inclusion criteria for screening would only have reduced the total number of screenings modestly and could have allowed us to miss two of our threshold cases who were both of 30 weeks gestational age and >1400 g birth weight. CONCLUSIONS: Screening is time consuming but worthwhile in view of the benefits of treatment. As applied to babies in the north of England, the current national screening criteria are satisfactory. The results of treatment of the babies identified in this study are presented in the accompanying paper.

Retinopathy of prematurity in practice. II: long-term results following treatment for threshold disease.

OBJECTIVE: To determine the long-term outcome of treatment for threshold retinopathy of prematurity (ROP) in one UK unit. METHODS: A total of 35 infants diagnosed with threshold ROP were treated by a single ophthalmologist (DGC) between 1987 and 1998. The parents of the 29 surviving patients were contacted; 21 brought their child for special review of acuity, motility, refraction and fundoscopy (Group 1). Of the eight patients who were unable to attend, six patients (Group 2) had sufficient follow-up detail in their records to be included in the study. RESULTS: A total of 40 eyes in the 21 patients in Group 1 had been treated; 10 had received cryotherapy (eight bilateral) and 11 had bilateral laser. Mean follow-up was 5 years (range 2-12 years). A total of 23 treated eyes (in 16 patients) had an acuity of 6/12+ (57.5% of treated eyes). Four eyes of three patients had no light perception. Seven eyes in four patients had myopia of more than 3 D. Eight patients had a manifest squint: six esotropia, two exotropia. The retinal status of 36 eyes (90%) showed a favourable outcome. The four blind eyes had stage 5 disease. In Group 2, four eyes of two patients (33%) had 6/12+ acuity recorded; five eyes in three patients had stage 5 disease and no perception of light. In total, a favourable structural outcome was achieved in 81.4% and favourable functional outcome observed in 74.6%. CONCLUSION: These results show that the favourable outcomes reported in the CRYO-ROP trial can be achieved in routine practice and maintained after long follow-up.

Reversible retinal toxicity associated with retained intravitreal copper foreign body in the absence of intraocular inflammation.

PURPOSE: To report on a patient who developed retinal toxicity from an intraocular copper foreign body in the absence of any signs of chalcosis or inflammation. METHOD: Case report. RESULT: Removal of the copper foreign body resulted in electroretinographic improvement and the patient has retained good vision. CONCLUSION: Retinal toxicity from intraocular copper can be subclinical and such foreign bodies should be removed. Removal of the foreign body can be associated with at least partial reversal of retinal toxicity.

Haemodynamic responses to subconjunctival mydriatic agents (Mydricaine) used for maintenance of perioperative mydriasis in patients undergoing vitreoretinal surgery.

PURPOSE: To assess the systemic effects of subconjunctival mydriatic agents (Mydricaine). METHODS: Haemodynamic variables were recorded at baseline and during the first 60 min following subconjunctival injection of Mydricaine and normal saline. RESULTS: Statistical analysis of the change in heart rate showed a highly significant difference between the two groups (p < 0.001). There was no significant difference in the effect on systolic or diastolic blood pressure between the two groups. CONCLUSIONS: We advise extreme caution when using Mydricaine via the subconjunctival route in patients with compromised cardiac function.

Refractive errors in children born before 32 weeks gestation.

PURPOSE: To document the refractive errors in a cohort of children born before 32 weeks gestation. METHODS: All children born before 32 weeks gestation between 1 January 1990 and 31 December 1991 to mothers resident in the Northern Region of the National Health Service were examined at 2 years old (n = 558). RESULTS: Stage 3 or worse retinopathy of prematurity (ROP) was associated with myopia. In those not developing stage 3 or worse ROP, the refractive errors were myopia in 1.5%, hypermetropia > 4 dioptres (D) in 5.4%, anisometropia > 1 D in 1.1% and astigmatism > 1.25 D in 5.7%. CONCLUSION: The incidence of refractive errors in those not developing stage 3 or worse ROP was similar to that in the general population.

Ocular outcome in children born before 32 weeks gestation.

Ocular outcome was assessed in a 2 year cohort of all children born before 32 weeks gestation within a geographically defined population of approximately 3 million. Five hundred and sixty-five children were born within the study period; 558 children (98.8% of the study group) were assessed at approximately 2 years old. There was a high incidence of abnormalities, particularly strabismus (70, 12.5%), cortical visual loss (7, 1.3%), sequelae of retinopathy of prematurity (16, 2.9%) and other significant refractive errors (69, 12.7%). These data provide a recent estimate of gestational age-specific prognosis and suggest that follow-up yields a significant proportion of children with visual abnormalities who could benefit from treatment.

Referral delay and ocular surgical outcome in Terson syndrome.

BACKGROUND: In Terson syndrome, vitreous hemorrhage can result from intracranial hypertension associated with intracranial bleeding. The vitreous hemorrhage can cause a considerable visual handicap. The aim of this study was to determine the outcome of surgery in patients with Terson syndrome and any delay in referral to an ophthalmologist. METHODS: Retrospective case review of 25 eyes of 17 patients undergoing vitrectomy for Terson syndrome. Delay in presentation to an ophthalmologist, intraoperative and postoperative complications, and the final visual acuity were noted. RESULTS: The mean interval between visual symptoms and referral to an ophthalmologist was 5.2 months for the nine unilateral cases and 4.9 months for the eight bilateral cases. Intraoperative complications included retinal break (2) and retinal dialysis (3). Late complications included epiretinal membrane (4), ghost cell glaucoma (1), and cataract (8). Twenty-two of the 25 eyes achieved a final visual acuity of 20/30 or better. CONCLUSION: Vitrectomy for vitreous hemorrhage in Terson syndrome is a safe and effective procedure, offering a rapid and prolonged improvement in vision. There is good reason to consider early vitrectomy, particularly when the hemorrhage is bilateral and dense.