An international comparison of retinopathy of prematurity grading performance within the Benefits of Oxygen Saturation Targeting II trials

Purpose

To investigate whether the observed international differences in retinopathy of prematurity (ROP) treatment rates within the Benefits of Oxygen Saturation Targeting (BOOST) II trials might have been caused by international variation in ROP disease grading.

Methods

Groups of BOOST II trial ophthalmologists in UK, Australia, and New Zealand (ANZ), and an international reference group (INT) used a web based system to grade a selection of RetCam images of ROP acquired during the BOOST II UK trial. Rates of decisions to treat, plus disease grading, ROP stage grading, ROP zone grading, inter-observer variation within groups and intra-observer variation within groups were measured.

Results

Forty-two eye examinations were graded. UK ophthalmologists diagnosed treat-requiring ROP more frequently than ANZ ophthalmologists, 13.9 (3.49) compared to 9.4 (4.46) eye examinations, P=0.038. UK ophthalmologists diagnosed plus disease more frequently than ANZ ophthalmologists, 14.1 (6.23) compared to 8.5 (3.24) eye examinations, P=0.021. ANZ ophthalmologists diagnosed stage 2 ROP more frequently than UK ophthalmologists, 20.2 (5.8) compared to 12.7 (7.1) eye examinations, P=0.026. There were no other significant differences in the grading of ROP stage or zone. Inter-observer variation was higher within the UK group than within the ANZ group. Intra-observer variation was low in both groups.

Conclusions

We have found evidence of international variation in the diagnosis of treatment-requiring ROP. Improved standardisation of the diagnosis of treatment-requiring ROP is required. Measures might include improved training in the grading of ROP, using an international approach, and further development of ROP image analysis software.

Visual acuity testability and comparability in Australian preschool children: the Sydney Paediatric Eye Disease Study

PURPOSE

To establish standardised protocols for vision screening, testability and comparability of three different vision tests were examined in a population-based, cross-sectional sample of preschool children (Sydney Paediatric Eye Disease Study).

METHODS

Measurement of presenting monocular distance visual acuity (VA) using the Amblyopia Treatment Study (ATS) HOTV protocol, was attempted by all (1774) children aged≥24 months. In addition, in children aged≥60 months (576), VA was also tested using the logMAR retro-illuminated HOTV or Early Treatment Diabetic Retinopathy Study (ETDRS) linear charts (CSV 1000). Children able to have both eyes tested monocularly were considered.

RESULTS

Testability significantly increased with age for all VA tests. The ATS HOTV with an overall testability of 80% (females: 82%, males: 78%) was the most testable of the VA tests (P<0.0001). In children aged <3 years testability was low (≤47%) rising to≥80% in children aged≥3. In children≥60 months, testability was higher for the HOTV (94%) than the ETDRS (59%) chart. In those that did two VA tests, mean difference of the ATS HOTV compared with the HOTV(CSV) was -0.1, and compared with ETDRS was -0.12 (P<0.0001).

CONCLUSIONS

Children aged <3 years had poor VA testability, whereas those 3 years and above were highly testable using the ATS HOTV. The HOTV (CSV) retro-illuminated test was appropriate for children aged >5 years, and may be possible in younger children with early educational exposure. When comparing VA measures using these tests, the higher VA attained using the ATS HOTV, needs to be taken into account.

Three horizontal muscle surgery for large-angle infantile esotropia: validation of a table of amounts of surgery

PURPOSE

To validate a table of amounts of three horizontal muscle surgery in patients with large-angle infantile esotropia (≥60 prism dioptres, PD).

METHODS

A prospective interventional case series reporting the postoperative alignment of 51 patients (27 male, 24 female) over a 15-year period was conducted. Surgery amounts were according to a published table developed on a previous patient cohort (n=49), using bilateral medial rectus recession with graded unilateral lateral rectus resection. Kaplan-Meier life-table survival curves were formulated for success to orthotropia (±10 PD) after one and subsequent horizontal muscle surgeries for up to 8 years follow-up.

RESULTS

The median preoperative deviation was 65 PD (range 60-80 PD) and median age at surgery was 11.8 months (range 5.1 months-3.6 years). Surgical success to orthotropia (±10 PD) after one surgery was 100% at 2 months, 95.7% at 6 months, 91.3% at 12 months, 77.8% at 4 years, and 73.6% at 8 years. Postoperative failure requiring further horizontal surgery occurred in 17.6% (residual esotropia 4, consecutive exotropia 5).

CONCLUSIONS

Our second cohort has reproduced the success rate of the previous cohort (77.8% vs 77.1% at 4 years). If the published table of surgical amounts is used, three horizontal muscle surgery in large-angle infantile esotropia (≥60 PD) appears to have a good long-term success rate, and does not lead to the high rates of either residual esotropia or consecutive exotropia reported by others in the literature.

Selective inner retinal dysfunction precedes ganglion cell loss in a mouse glaucoma model

BACKGROUND/AIMS

To correlate ganglion cell function with defined parameters of the elevated intraocular pressure profile (IOP) in a mouse glaucoma model and to determine the temporal relationship of these functional changes with ganglion cell death.

METHODS

Unilateral chronic ocular hypertension was induced in C57BL6/J mice by laser ablation of the limbal episcleral veins. Scotopic flash electroretinograms were recorded after 5, 10, 20, and 40 days to isolate specific outer and inner retinal responses. Inner retinal function was correlated with the pressure differential between treated and non-treated eyes at the time of electroretinographic recording, and with the cumulative IOP insult (the integral of the IOP.time profile). Peripheral and central ganglion cell densities were quantified by Brn-3 immunohistochemistry.

RESULTS

Elevated IOP induced a preferential deficit in inner retinal function. The positive scotopic threshold response (pSTR) was suppressed by 68% on day 5, by 50% on day 10, by 54% on day 20 and by 46% on day 40 after laser treatment. Inhibition of the STR correlated with the pressure differential between treated and non-treated eyes but not with the IOP.time integral. Inner retinal dysfunction preceded the progressive death of ganglion cells. Ganglion cell loss occurred preferentially in peripheral retina and correlated with the cumulative IOP insult.

CONCLUSION

We have demonstrated specific inner retinal dysfunction in an inducible mouse glaucoma model. STRs are sensitive to elevated IOP per se, and their early suppression reflects ganglion cell dysfunction rather than cell death. The correlation between IOP elevation and suppression of inner retinal function, in the context of the temporal progression of ganglion cell death, suggests that a portion of the IOP-mediated ganglion cell dysfunction may be reversible.

Telepaediatrics and diabetic retinopathy screening of young people with diabetes in Queensland

We have examined the feasibility of a telemedicine-enabled screening service for children and adolescents with diabetes in Queensland. There are approximately 1400 young people with diabetes in Queensland and only about two-thirds of them are screened in accordance with international guidelines. A regional retinal screening service was established using a nonmydriatic digital retinal camera. Seven centres volunteered to participate in the study. During a five-month pilot trial, 83 of the young people with diabetes who attend these centres underwent digital retinal screening (3.7%). Retinal images were sent via email to a paediatric ophthalmologist for review and results were returned via email. A copy of each participant's results was forwarded by mail to the referring diabetes doctor and the participant and family. The majority of the image files (96%) were rated as excellent or good. Only one participant was identified as having an abnormal result. Participants and their families expressed satisfaction with the digital retinal screening process.

Delayed orbital hemorrhage after routine strabismus surgery

PURPOSE

To report a case of delayed rectus muscle hemorrhage after strabismus surgery.

METHODS

Case report.

RESULTS

Rectus muscle hemorrhage occurred 36 hours after strabismus surgery in a 26-year-old man, causing temporary loss of vision and reduced ocular motility. Urgent lateral cantholysis and orbital exploration to restore hemostasis were undertaken. Full recovery of vision occurred and a small residual motility disturbance was present 3 months postoperatively.

CONCLUSION

Delayed rectus muscle hemorrhage poststrabismus surgery is rare but can have sight-threatening effects. When vision is threatened because of optic nerve compromise, urgent orbital exploration may allow full recovery of function.

Proximal arterial vasoconstriction precedes regression of the hyaloid vasculature

PURPOSE

To determine whether constriction of proximal arterial vessels precedes involution of the distal hyaloid vasculature in the mouse, under normal conditions, and whether this vasoconstriction is less pronounced when the distal hyaloid network persists, as it does in oxygen-induced retinopathy (OIR).

METHODS

Photomicrographs of the vasa hyaloidea propria were analysed from pre-term pups (1-2 days prior to birth), and on Days 1-11 post-birth. The OIR model involved exposing pups to approximately 90% O(2) from D1-5, followed by return to ambient air. At sampling times pups were anaesthetised and perfused with india ink. Retinal flatmounts were also incubated with FITC-lectin (BS-1, G. simplicifolia,); this labels all vessels, allowing identification of vessels not patent to the perfusate.

RESULTS

Mean diameter of proximal hyaloid vessels in pre-term pups was 25.44 +/- 1.98 microm; +/- 1 SEM). Within 3-12 hrs of birth, significant vasoconstriction was evident (diameter:12.45 +/- 0.88 microm), and normal hyaloid regression subsequently occurred. Similar vasoconstriction occurred in the O(2)-treated group, but this was reversed upon return to room air, with significant dilation of proximal vessels by D7 (diameter: 31.75 +/- 11.99 microm) and distal hyaloid vessels subsequently became enlarged and tortuous.

CONCLUSIONS

Under normal conditions, vasoconstriction of proximal hyaloid vessels occurs at birth, preceding attenuation of distal hyaloid vessels. Vasoconstriction also occurs in O(2)-treated pups during treatment, but upon return to room air, the remaining hyaloid vessels dilate proximally, and the distal vessels become dilated and tortuous. These observations support the contention that regression of the hyaloid network is dependent, in the first instance, on proximal arterial vasoconstriction.

Vitreal macrophages express vascular endothelial growth factor in oxygen-induced retinopathy

PURPOSE

The possibility of vitreal macrophages playing an angiogenic role in oxygen-induced retinopathy (OIR) was investigated. Oxygen-induced retinopathy was produced in newborn animals with the purpose of modeling the proliferative phase of human retinopathy of prematurity (ROP).

MATERIALS AND METHODS

To produce OIR in neonatal mice, litters at postnatal day 7 were placed in 80-90% oxygen for a period of 5 days and then returned to room air. Pups were killed on days 7, 12, 15, 17 and 20 over the postnatal period and were perfusion-fixed using a saline wash-out, followed by 4% paraformaldehyde and then India Ink. Eyes were enucleated and either whole-mounted, or snap-frozen and cryosectioned. Immunostaining procedures were used to visualize macrophages and vascular endothelial growth factor (VEGF) protein. The primary antibodies used were anti-F4/80 and antimouse VEGF, respectively. Vitreal macrophages closely associated with the vitreo-retinal interface (within 25 microm of the inner limiting membrane) were counted. In situ hybridization procedures were used to analyse for the presence of VEGF mRNA transcript in vitreal macrophages.

RESULTS

Macrophage numbers were found to significantly increase (P < 0.05) in eyes from oxygen-treated animals compared with those from age-matched controls. A close spatial relationship was observed between macrophages and vitreal neovascular sprouts. In addition, vitreal macrophages were also found to transcribe and express VEGF in the oxygen-treated animals during the vasoproliferative phase.

CONCLUSIONS

Our results raise the possibility that vitreal macrophages play a role in the pathogenesis of OIR and by inference, ROP.

Evaluating photoscreeners II: MTI and fortune videorefractor

BACKGROUND

Amblyopia is a public health problem, usually amenable to treatment if detected early. Photoscreeners are camera-based instruments which can detect risk factors for amblyopia such as squint, refractive errors and media opacities.

OBJECTIVE

To evaluate two commercially available photoscreeners, namely the MTI photoscreener (Medical Technology, Iowa City, IA, USA) and the Fortune Optical VRB-100 (Fortune Optical, Padova, Italy) videophotorefractor, in a selected childhood population, having a high prevalence of amblyopia, before undertaking a full-scale trial in the general population.

SUBJECTS AND METHODS

The study design was a double-masked study. One-hundred and five children aged between 12 and 44 months with either normal vision or known visual disorders were photoscreened without cycloplegia using the Fortune and the MTI photoscreeners. Each child had a full ophthalmic examination either on the day of screening or in the preceding 6 months. Risk factors were: any manifest strabismus (squint), hypermetropia >3.5 D, anisometropia > or =1 D sphere, myopia > or =2 D sphere, astigmatism > or =2 D, media opacity or fundus abnormality affecting vision. The prevalence of risk factors for amblyopia was 60%. Photoscreen images were reviewed by two independent masked observers for indicators of amblyopiogenic risk factors and compared to the full ophthalmological examination to determine sensitivity and specificity for each instrument.

RESULTS

Sensitivities and specificities for the detection of risk factors for amblyopia were as follows. Fortune photoscreener: reader 1, sensitivity 60%, specificity 75%; reader 2, sensitivity 68% specificity 86%. MTI photoscreener: reader 1, sensitivity 56%, specificity 79%; reader 2, sensitivity 61%, sensitivity 86%. The results for reader 1 and 2 showed no significant differences for either instrument.

CONCLUSION

Both instruments performed unsatisfactorily in a study population aged 1-4 years with a high prevalence of amblyopiogenic risk factors. Accordingly, we do not believe that either instrument can be recommended to screen for eye disorders in children between the ages of 1 and 4 years because the low prevalence of amblyopia in this population demands very high sensitivity and specificity in order to avoid inappropriate over- or under-referral.

Late presentation of a unilateral sporadic retinoblastoma in a 16-year-old girl

BACKGROUND

Retinoblastoma is the commonest intraocular tumour of childhood with the majority of cases being diagnosed before 5 years of age. Late presentation of retinoblastoma is rare.

CASE HISTORY

A healthy 16-year-old Caucasian girl presented with a 1-day history of blurred vision in the left eye. Examination revealed an inferonasal mass in the left retina with an overlying haemorrhage and vitreous seeding. Imaging studies revealed a 5-mm densely calcified opacity. Other investigations, including cerebral spinal fluid examination, bone marrow aspirate trephine, toxocara serology and serum protein studies, were normal. After considering the differential diagnoses such as toxocariasis and Coat's disease, a diagnosis of late-presenting retinoblastoma was made. The patient subsequently underwent enucleation with a primary orbital implant. The diagnosis was confirmed histopathologically.

CONCLUSION

Late presentation of retinoblastoma is uncommon but can be a cause of acute visual impairment in the non-paediatric age group. Retinoblastoma should be considered in the differential diagnosis of a fundal mass in any age group.

Autosomal dominant cataracts and Peters anomaly in a large Australian family

Peters anomaly is a congenital corneal opacity with underlying defects in the posterior stroma, Descemets membrane and corneal endothelium. It is a disorder resulting from abnormal migration or function of neural crest cells and may include abnormalities of other anterior segment structures, such as the lens and iris. We report a family in which anterior segment abnormalities, including Peters anomaly and cataracts, were inherited in an autosomal dominant fashion. Although the PAX6 gene on chromosome 11 has been shown to be involved in some cases of anterior segment developmental defects, we found no evidence that the condition in this family is linked to the PAX6 gene. Identification of this gene will indicate another gene with major involvement in the development of the anterior segment of the eye.

Angle-closure glaucoma after laser treatment for retinopathy of prematurity

Laser photocoagulation has become the standard for treatment of retinopathy of prematurity. In general, it has been found to be a safe and effective means of retinal ablation. We report a case of angle-closure glaucoma in an infant after diode laser treatment for retinopathy of prematurity, which required bilateral surgical peripheral iridectomies.

The nanophthalmic macula

AIMS

To define an unusual macular appearance found in association with nanophthalmos.

METHODS

A case review.

RESULTS

Seven children (aged 8 months to 17 years) with nanophthalmos were examined. They all exhibited the same clinical findings of an unusual yellow macula appearance with retinal folds and crowded optic discs. Visual electrophysiology performed in four cases was normal.

CONCLUSION

A distinctive yellow macular pigmentation with associated chorioretinal folds and crowded optic discs is present in nanophthalmos. It is proposed that the retinal folds are due to a disparity between scleral and retinal growth while the macula discoloration is due to a congenital abnormality in arrangement or position of the luteal pigment and is not degenerative. Included in this case series is the second case in the literature of nanophthalmos associated with Kenny's syndrome. Inheritance of nanophthalmos appears to be autosomal recessive.

Results of treatment of superior oblique overaction by silicone tendon-expander technique

PURPOSE

To report the results of treatment of a series of patients with superior oblique overaction using the superior oblique silicone tendon-expander technique.

METHODS

A chart review of 17 patients with superior oblique overaction who had a total of 26 silicone tendon-expander procedures was conducted.

RESULTS

Mean preoperative degree of superior oblique overaction was +2.7. 92% of eyes had mild (+1) or no residual overaction at last postoperative assessment (follow-up range: 6 to 59 months). Of 15 patients with preoperative A-pattern of 10 prism diopter (delta) or more, only two patients (13%) had A-pattern of 10 delta or more at last assessment. Of 13 patients with preoperative hypotropia in primary position, five patients (38%) had no vertical deviation in primary position, and seven patients (54%) had persistent, but less vertical deviation in primary position at last assessment (mean reduced from 11 delta to 4 delta). No patient manifested superior oblique palsy at their last postoperative assessment.

CONCLUSIONS

We believe that the superior oblique tendon-expander technique should be strongly considered for the treatment of superior oblique overaction associated with A-pattern or hypotropia in primary position, because it has a high success rate and a low incidence of postoperative complications. Consecutive superior oblique underaction did not occur in this series.

Evaluation of photoscreener instruments in a childhood population. 1. Otago photoscreener and Dortmans videophotorefractor

OBJECTIVE

To evaluate two photoscreeners in a childhood population.

STUDY DESIGN

Double-masked study.

SUBJECTS AND METHOD

One hundred and thirteen children aged between 11 and 44 months with either normal vision or known visual disorders were photoscreened without cycloplegia by the Otago and Dortmans (prototype) photoscreeners. Each child had a full ophthalmological examination either on the day of screening or in the proceeding six months. Photoscreen images were reviewed by an independent observer for indicators of amblyopiogenic risk factors, and compared to the full ophthalmological examination to determine sensitivity and specificity for each instrument.

RESULTS

The Otago photoscreener returned a sensitivity of 70% and specificity of 82% for the detection of amblyopiogenic risk factors. The Dortmans photoscreener returned a sensitivity of 70% and specificity of 90%. Both photoscreeners were portable and easily operated.

CONCLUSION

Children can be screened successfully for amblyopiogenic risk factors with these photoscreening systems. Further evaluation is required to determine specificity in a normal population. This would also provide information on the potential usefulness of photoscreeners in a cost effective childhood vision screening program.

Results of anterior transposition of the inferior oblique

PURPOSE

We present the results of anterior transposition of the inferior oblique in a series of patients with inferior oblique overaction and dissociated vertical deviation (DVD).

PATIENTS AND METHODS

We performed a retrospective study of 37 procedures on 21 patients who had unilateral or bilateral inferior oblique anterior transpositions. Before surgery, patients had +1 to +3 inferior oblique overaction and +1 (< 10 PD) or +2 (10 PD-20 PD) degree of DVD. The inferior oblique insertion was transposed to between 2 mm posterior to and 2 mm anterior to the temporal border of the inferior rectus insertion. Mean follow-up period was 27 months.

RESULTS

Incidence of inferior oblique overaction of +2 or more was reduced from 84% before surgery to 16% at last postoperative assessments. Some 43% of eyes had no inferior oblique overaction and 86% had an improvement in the degree of inferior oblique overaction. At last assessments, 57% of eyes had no evidence of DVD and 68% of eyes had no evidence of DVD or an improvement in the degree of DVD. No patient who had unilateral anterior transposition developed hypotropia in primary position and there was no evidence of inferior oblique underaction in any patient at last assessment. Three patients requiring repeat inferior oblique surgery are discussed, including one patient who developed a large Y-pattern exotropia after bilateral anterior transposition of the inferior obliques.

CONCLUSIONS

Inferior oblique anterior transposition has a place in the treatment of coexistent inferior oblique overaction and dissociated vertical deviation.

Validity of the Bruckner reflex in the detection of amblyopia

PURPOSE

To establish the sensitivity and specificity of the Bruckner reflex (comparison of the fundus red reflexes) in the detection of amblyopia or its risk factors.

METHODS

A single masked study using a medical student's diagnostic ability against the gold standard of a full clinical examination by a paediatric ophthalmologist.

SETTING

A university teaching hospital outpatient facility.

PATIENTS

Three hundred and one patients consecutively referred for ophthalmic assessment.

RESULTS

The sensitivity of the test for the detection of children with amblyopia risk factors was 86% and the specificity was 65%. Of 70 children with a definite diagnosis of amblyopia, the sensitivity of the test was 95%.

CONCLUSIONS

The Bruckner reflex is a useful screening test for primary eye care personnel. However, there is a significant false-positive rate which will result in unnecessary referrals. We recommend that it form part of a battery of tests, including, for example, the modified base down prism test, which are useful in assessing the vision of preverbal children.

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.

Do tinted lenses improve the reading performance of dyslexic children? A cohort study

The use of tinted lenses as a method to improve reading skills in children with dyslexia has been a controversial issue in recent years. The purpose of the present study was to determine if tinted lenses cause a measurable improvement in the reading performance of dyslexic children. Twenty-four children aged 8 to 12 years participated in the study. Dyslexia was diagnosed in all children by psychological evaluation, and these children underwent an ophthalmic evaluation for inclusion into the study. Participants were graded for speed and accuracy as they read through spectacle frames that contained red-, blue-, yellow-, and green-tinted lenses, a neutral-density lens, and empty frames. All lenses for each subject were of the same density level, with subjects alternately distributed to one of two densities tested (0.12 or 0.30 log units). Each child was asked to select the lens condition that subjectively improved reading ability at the conclusion of testing. One-way analysis of variance of reading performance showed neither improvement nor deterioration attributable to lens color or density when applied to error rates (F = 1.73, P = .14 for a density of 0.12; F = 0.28, P = .92 for a density of 0.30) or to reading rates (F = 0.98, P = .44 for a density of 0.12; F = 0.81, P = .55 for a density of 0.30). In addition, the lens condition that was subjectively preferred by each child did not correlate with actual reading performance (chi 2 = 3.83, not significant; 11.07 needed for significance at P = .05).

Oxygen-induced retinopathy: ultrastructure of vitreous new vessels in the kitten model

Oxygen-induced retinopathy was produced by exposing 3-day-old kittens to 80% oxygen between 60 and 105 hours. They were then allowed to survive in room air until day 15, 21 or 28 when they were sacrificed after perfusion with colloidal carbon. Specimens were prepared for transmission electron microscopy. Ninety separate vitreous capillaries from oxygen-treated animals were examined. A total of 235 intercellular junctions were examined, 116 of them from the 15-day old animals. In the 15-day old animals, five junctions of 116 were open and the remainder were tight. No open junctions were seen in 21- or 28-day-old animals. In one capillary from a 15-day animal, fenestrated endothelium was seen in an aberrant, intraluminal loop of endothelium which formed no part of the blood/tissue barrier. The wall thickness of the vitreous new vessels seemed to decrease and the number of vesicles and vacuoles appeared to increase with increasing age. The basement membrane of the vitreous new vessels was scanty. In some sections, cells, presumably macrophages, were seen outside the new vessels. It is concluded that the increased permeability of the vitreous new vessels in 15-day-old animals can be explained by, and is possibly totally due to, the presence of open endothelial junctions.

The mouse model of oxygen-induced retinopathy: a suitable animal model for angiogenesis research

Newborn mice exposed to high (greater than 98%) ambient oxygen during the newborn period and subsequently removed to room air will develop a proliferative retinopathy which mimics the neovascular component of acute retinopathy of prematurity. In this paper, we report preliminary ultrastructural findings on the vitreous new vessels in the mouse model of oxygen-induced retinopathy, and argue that the model is appropriate for research on non surgical treatments for ROP in particular and angiogenesis in general.

Eccentric photorefraction: improving the predictive value and yield in detection of refractive errors

Eccentric photorefraction (EPR) is a simple photographic technique for detecting amblyopiogenic conditions. Previous EPR studies to detect refractive errors (RE) have demonstrated high sensitivity but poor predictive value. We have established new criteria for detecting RE involving quantifying retinoscopic reflex crescent widths, thereby achieving 67% predictive value with 100% sensitivity for detecting RE greater than or equal to +3.5 D in a clinical study of 69 children. Optical analysis of EPR shows that anticrescent width (light crescent-free portion of the pupil) is independent of pupil diameter. Quantifying anticrescent widths in the above clinical trial increased the predictive value to 85%. Schematic eye and human eye EPR studies verify the theoretical prediction that similar ability to detect refractive errors is maintained when the working distance and eccentricity (distance of light source from lens edge) are reduced. These improvements in EPR reduce its cost and improve its yield; both are essential for its introduction as an acceptable community screening tool.

Tinted lenses and dyslexics--a controlled study. SPELD (S.A.) Tinted Lenses Study Group

We have carried out a randomised prospective controlled trial of the effect of tinted lenses on the reading ability of 24 non-asthmatic dyslexic children aged between nine and twelve years. Reading ability was assessed using the Neale Analysis of Reading. After one school term, there was no significant difference in the change in reading age between treatment and control groups. After two school terms (approximately six months), only 11 children (44%) were still wearing the glasses. Of 381 suitable subjects for entry into the study, 208 were excluded because of a diagnosis of asthma (to avoid effects of medication on cerebral function). As a result, we may have excluded subjects who would have responded favourably to tinted lenses.

Localization of laminin to retinal vessels of the rat and mouse using whole mounts

Using a whole mount procedure in adult and neonatal mice and adult rats, we have developed an immunohistochemical method for the localization of laminin-like immunoreactivity (LLIR) to the retinal vessels. LLIR was localized to the vascular basement membrane, permitting a clear three-dimensional view of the retinal vasculature. Positive stain was seen in the inner limiting membrane, in retracted capillaries, encasing pericytes, and in a banding pattern on retinal arterioles. The major findings with the whole mount preparations were confirmed using paraffin-embedded material, with the additional observation of LLIR in the lens capsule. In whole mounts of retinas from neonatal mice, LLIR was present from the earliest stages of capillary growth, indicating that laminin is likely to be secreted by endothelial cells during retinal angiogenesis. LLIR within the retinal nerve fiber layer does not precede capillary ingrowth, so no evidence was found that laminin acts as a tracker signal for retinal angiogenesis.

Laminin-like immunoreactivity in induced new vessels in kitten and mouse eyes

Laminin is a basement membrane glycoprotein, widely distributed in body tissues. It has been found on capillary basement membranes in both developing and adult retinal vessels. Oxygen-induced retinopathy was produced in kittens and mice by exposing them to a high oxygen environment during the newborn period. When the animals developed a proliferative retinopathy after a period of survival in room air, they were sacrificed and the eyes enucleated and embedded in paraffin wax. Cross-sections were cut and de-waxed. After preliminary digestion with pepsin, we used a fluorescein isothiocyanate (FITC)-labelled double antibody technique to identify laminin-like immunoreactivity (LLIR). LLIR was found on both intravitreal and intraretinal new vessels in the kitten and mouse, indicating that it is probably secreted by endothelial cells during the formation of pathological new vessels.

Combined hamartoma of the retina and RPE: an unusual cause of the dragged disc appearance

Combined hamartoma of the retina and retinal pigment epithelium (RPE), is a rare, benign, congenital fundal lesion which contains a mixture of glial tissue, blood vessels and pigment epithelium. Such tumours are variably pigmented and may be wrongly diagnosed as malignant melanoma or retinoblastoma. We report two cases which were located in the periphery of the fundus and which produced a dragged disc appearance.

A microprocessor-driven one-operator forced-choice preferential looking apparatus

Forced-choice preferential looking (FPL) is a behavioural technique for the estimation of visual acuity in preverbal children. We have constructed an electromechanical FPL apparatus controlled by a microprocessor requiring just one operator. Sixty-three babies aged between six weeks and eleven months were evaluated with an overall success rate of 83% in obtaining an acuity measurement. FPL is a practical method for measurement of infant visual acuity in the ophthalmic clinic setting.

Massive choroidal haemorrhage as a complication of krypton red laser photocoagulation for disciform degeneration

A 78-year-old man with perifoveal subretinal neovascularization originally treated with krypton red laser was re-treated. An attempt was made to produce a "chalky white" burn at the site of the neovascular frond. Immediately after a burn, a brisk choroidal haemorrhage followed, apparently from a ruptured choroidal vessel. Bleeding occurred subretinally and into the vitreous, blinding the patient. While the krypton red laser carries advantages over the argon laser in the treatment of subretinal neovascular fronds, this case indicates that hard burns with the krypton laser carry a risk of massive subretinal haemorrhage.

Angiogenic factors and their assay: activity of formyl methionyl leucyl phenylalanine, adenosine diphosphate, heparin, copper, and bovine endothelium stimulating factor

A number of chemically unrelated substances have been compared for their neovasculogenic activity by two different in vivo tests, and for their ability to induce cultured endothelial cell migration and proliferation. Formyl methionyl leucyl phenylalanine, copper ions, heparin, adenosine diphosphate, and low-molecular-weight bovine endothelium stimulating factor were all neovasculogenic by the corneal pocket assay. By the chorioallantoic membrane assay, copper ions and formyl methionyl leucyl phenylalanine were not detectably neovasculogenic. By the same assay it has been possible to demonstrate angiogenic activity in bovine endothelium stimulating factor that is distinguishable from copper ions. This bovine factor, in contrast to the other agents, induced marked endothelial cell migration and also proliferation and may belong to a special class of agents which represents direct acting angiogenic activity.

Oxygen induced retinopathy: the kitten model re-examined

We have studied the kitten model of oxygen induced retinopathy by the technique of corrosion vascular casting/scanning electron microscopy. The predominant morphological features of the kitten model are preretinal and intraretinal neovascularization with a minor component of arterio-venous shunting. This is contrasted with the active phase of the blinding disease in the human neonate which is characterised predominantly by so called 'mesenchymal arterio-venous shunting'. A failure to appreciate fundamental differences in the nature of oxygen induced retinopathy between the human infant and its kitten model we believe has led to erroneous conclusions about pathogenesis in the human neonate.

Cellular and molecular mechanisms in angiogenesis

Low concentrations of copper sulphate, Dispirin, or Walker carcinoma extract elicit intraocular vascularization when tested by anterior chamber implants in rats. The response is markedly depressed by pre-treatment of animals with methylprednisolone acetate, suggesting that such induced vascularization is mediated by leucocytes. Since many agents inducing vascularization also induce migration of cultured endothelial cells, it raises the problem of how to isolate and study the action of possible leucocyte-derived angiogenic factors. Regardless of the identity of the natural angiogenic factor or factors, it is proposed that during blood vessel formation specialized endothelial cells migrate in response to an angiogenic signal and deposit fibronectin on which other cells can track and subsequently adhere, forming an endothelium.