Helen S. Jones

Compliance in amblyopia therapy: objective monitoring of occlusion.

AIM/BACKGROUND--This study aimed to determine the feasibility of objective compliance monitoring of amblyopia therapy in clinical research. Occlusion has been the mainstay of amblyopia therapy for over 250 years, yet it has never been subjected to rigorous evaluation. Treatment regimens range arbitrarily from a few minutes to most of the waking hours of the day. Compliance is problematic and as, hitherto, accurate objective monitoring has been impossible it is not known how much occlusion is required to effect an improvement in vision. METHODS--An occlusion dose monitor (ODM) has been developed. The ODM consists of a modified occlusion patch and a miniature battery driven datalogger which periodically monitors patch skin contact. The patch is a standard disposable item with two miniature electrocardiogram electrodes attached to its undersurface. The datalogger comprises a high speed static RAM and a clock driven address counter. Data are retrieved using an IBM PC/AT computer. Fifteen child amblyopes were randomly allocated unilateral occlusion of 1, 4, or 8 hours per day for 4 weeks. Owing to data loss, presumed because of accumulation and discharge of static electricity, an additional child was included in the 8 hour group. Outcome measures were objective (ODM) and subjective (diary) compliance with treatment, logMAR visual acuity, and contrast sensitivity. RESULTS--Objective monitoring of occlusion is technically feasible and clinically informative. CONCLUSION--Objective monitoring of occlusion has opened up new research opportunities which, it is hoped, will enable the dose-effect relation of occlusion therapy in the various types of amblyopia to be investigated objectively, and facilitate the design of effective therapeutic regimens.

Retinopathy of prematurity: A prospective study. Review at six months

A cohort of infants of birthweight &leq;s 1700 g studied prospectively for retinopathy of prematurity (ROP) has been reviewed at 6 months corrected age and the findings related to the neonatal data. The overall incidence of strabismus was 6.4% (30/468), rising from 3.1% (7/229) without ROP to 29.2% (7/24) with stage 3. Strabismus and fusional ability were significantly related to presence and severity of ROP, and abnormal neonatal cranial ultrasound findings. Binocular visual acuity was measured in 340 infants between 20 and 40 weeks corrected age. Eight were subnormal, all due to neurological problems. For the remainder, despite falling within the normal range, there was a significant trend (p<0.001) for lower acuities with increasing ROP severity. Cycloplegic refraction on 387 infants revealed, with increasing ROP severity: 1, a significant trend towards myopia; 2, increased magnitude of astigmatism; 3, alteration of the astigmatic axis; 4, increased incidence of anisometropia. For the first three categories there was an insignificant trend between no ROP and stage 2, reaching significance only between stage 2 and 3. The predominant axis of astigmatism in infants without ROP was between 60° and 120°, but with ROP there was a significant trend away from this direction.

ARE WE SCREENING TOO MANY BABIES FOR RETINOPATHY OF PREMATURITY

A retrospective, hospital-records-based study of neonates screened for retinopathy of prematurity (ROP) was undertaken to determine whether the inclusion criteria for screening could have been safely altered to reduce the numbers of babies screened whilst not missing any stage III disease. Babies from six neonatal intensive care units in Birmingham were screened by a single examiner. Between November 1989 and November 1995, 1611 babies were examined and 1429 of these fell within the inclusion criteria of current guidelines for ROP screening produced by the Royal College of Ophthalmologists and the British Association of Perinatal Medicine – any baby &leq; 1500 g birthweight or &leq; 31 weeks gestational age. Thirty-nine (39) babies developed stage III ROP of which 31 (2.2%) were from Birmingham. In addition 8 babies with stage III ROP were referred from elsewhere. All 39 babies with stage III ROP had a birthweight &leq; 1250 g or a gestational age of &leq; 29 weeks, but 2 fell outside one criterion, indicating the need for both to be used. Had these inclusion criteria been utilised during this period, then 30% fewer babies would have been examined (432 of 1429). The importance of using both birthweight and gestational age as inclusion criteria is discussed, and the dangers of altering the indications for national screening on the basis of one study population is emphasised.

Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study

AIMS/BACKGROUND To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose. METHODS Subjects were entered into a two phase trial. In the first (‘pretreatment’) subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase (‘treatment’) in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor. RESULTS Eight subjects completed the trial, all but one of whom achieved >80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p=0.008) while mean CS gained 0.09 log units (p=0.01). An identical improvement in mean VA was recorded in the fellow eyes (p=0.03) while mean CS gained 0.11 log units (p=0.02). Within the treatment phase, mean VA further improved (0.12 log units, p=0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p=0.09). CONCLUSIONS Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of ‘pretreatment effects’ and the necessity to confirm objectively the occlusion dose a child receives.

Visual acuity: Calculating appropriate averages

ABSTRACT Controversy surrounds the averaging of visual acuity scores We examine this debate and provide a series of guidelines and worked examples to enable investigators to select an average (eg arithmetic mean, geometric mean, median) appropriate for their data

Binocular inhibition of visual performance in patients with cataract. The influence of test reliability.

Abstract Patients with cataract may show binocular inhibition: their sight improves on closing the eye in which vision is poorer. Of 36 patients questioned, one‐third reported this to be the case. To quantify this phenomenon, all patients undertook a battery of tests of spatial visual performance and, in an attempt to define the reliability of their scores, were tested on two separate occasions. Patients generally performed inconsistently: at best, of 8 patients who demonstrated inhibition on a single test, only 5 did so again when re‐tested after a short interval. In general, the magnitude of inhibition was less than that which could be reliably detected using the test battery. In addition, self‐reported inhibition was not predictive of inhibition measured psychophysically. It is concluded that clinical tests of form vision lack either the necessary reliability or sensitivity to identify patients with cataract who report inhibition of binocular visual function.

General practitioners' awareness of different techniques of cataract surgery: implications for quality of care.

With the introduction of fundholding, general practitioners can now purchase treatment from theprovider of their choice. To obtain the best treatment for their patients they need to keep abreast of new developments in a large range of specialties. The past decade has seen profound changes in ophthalmology, particularly in cataract surgery. Extracapsular cataract extraction and phacoemulsification have largely superseded intracapsular cataract extraction, mainly because of the higher risk of sight threatening complications with intracapsular extraction.1,2 Although extracapsular surgery is now the most commonly used method in the United Kingdom, 2%-4% of ophthalmologists routinely perform intracapsular surgery3,4 and 1% do not routinely use intraocular …