Modified Bagolini striated glass test: clinical applications of starlight test in binocular visual field screening

AIM—To introduce the "starlight" test which was devised to check binocular vision in normal conditions of seeing in a rapid, easy, and cost effective manner and to estimate the possibility of its clinical use in screening the binocular visual field of patients.
METHOD—The Bagolini striated glass test consists of optically plano lenses with imperceptible parallel scratches that barely blur the environment but produce two perpendicular luminous stripes (right eye stripe of 45° and left eye stripe of 135°) when subjects with normal binocular vision view one light source. Unlike the original Bagolini test, the starlight test uses three light sources in horizontal or vertical lines according to the testing purposes and the subject is asked to fixate upon the centre light. Through Bagolini glasses, the subject observes the resulting grid-like pattern and the state of binocular visual field of the subject can be roughly estimated.
RESULTS—Normal subjects and patients with strabismus, visual field loss from intracranial diseases, glaucoma, retinitis pigmentosa, and functional visual loss were examined using the starlight test and findings from each case were discussed.
CONCLUSIONS—The starlight test, which was made by hand at a low cost, is a simple test that can be used clinically. It provides information about the state of binocular vision of patients in normal conditions of seeing. It is also useful because it enables the examiner to share similar experiences with the examinee. The results suggest it can be effective in visual field screening.

Keywords: Bagolini striated glass; binocular visual field; screening; starlight test     

Visual impairment and socioeconomic factors

BACKGROUND—Information about socio economic factors associated with visual impairment can assist in the design of intervention programmes. Such information was collected by the Melbourne Visual Impairment Project (Melbourne VIP).
METHODS—The Melbourne VIP was a population based study of non-institutionalised permanent residents in nine suburbs of the Melbourne metropolitan area aged 40 years of age and older. A standardised eye examination was provided to eligible residents which included a structured interview. Variables of interest for this analysis were age, sex, country of birth, language spoken at home, education level, use of private health insurance, employment status, and living arrangements. Visual impairment was defined as a best corrected visual acuity <6/18 and/or visual field constriction to within 20° of fixation
RESULTS—A total of 3271 (83%) residents participated. Participants ranged in age from 40 to 98 years; 54% were female. Forty four (1.34%) were classified as visually impaired due to visual acuity and/or visual field loss. To evaluate the independent association of the significant sociodemographic variables with visual impairment, a regression model was constructed that included age, retirement status, use of private health insurance, and household arrangement. The results showed that age was the significant predictor of visual impairment (OR: 3.19; CI: 2.29-4.43), with the mean age of people with visual impairment significantly older (75.0 years) compared with people without visual impairment (58.2 years) (t test=9.71; p=0.0001). Of the 44 visually impaired people, 39 (87%) were aged 60 years of age and older.
CONCLUSION—The results indicate that age is the most significant factor associated with visual impairment. Of some importance was the finding that people with visual impairment were less likely to have private health insurance. With the aging of the population, the number of people affected by visual impairment will increase significantly. Intervention programmes need to be established before the onset of middle age to offset the escalation of visual impairment in the older population.

     

Eye care utilisation patterns in a rural county in Ireland: implications for service delivery

AIMS/BACKGROUND—This investigation determined eye care utilisation patterns in a rural county in Ireland. Population based estimates of visual impairment and glaucoma were available, so the two studies will optimise planning for eye care services for the county.
METHODS—Roscommon has a population of 55 000 served by one ophthalmologist and two optometrists. Data were collected on all outpatient visits for all providers for a 3 month period. Information was abstracted on demographics, presenting and final diagnoses. Expected number of visits for glaucoma were calculated using the population structure and rates of glaucoma, and assuming one visit per year per glaucoma patient.
RESULTS—1398 patients had a total of 1442 visits in 3 months. A third of the visits were to optometrists, and all but 21 visits were for normal eye examinations or glasses. The majority of children aged less than 16 years, and people older than 60 years were seen by the ophthalmologist. Among children, 81% of all visits were to the ophthalmologist and 92% were classified as a normal examination. Only an estimated 188 visits per year for glaucoma were observed, compared with 1100 expected.
CONCLUSION—In this rural county, many of the visits to the ophthalmologist were for normal eye examination, particularly among children. Screening algorithms which would free the ophthalmologist to see more complicated problems could be considered. There is an underutilisation of services by glaucoma patients. Reasons for this are described.

     

Visual outcome after paediatric cataract surgery: is age a major factor?

AIMS—To determine functional results after unilateral and bilateral cataract surgery in children with different aphakic optical correction.
METHODS—In this retrospective study, we evaluated visual acuity and binocular vision in 107 children who underwent cataract surgery during the 10 year period from 1985 to 1995. Aphakia was corrected by an intracapsular intraocular lens (IOL), spectacles or contact lenses.
RESULTS—Mean visual acuity was >20/40 (<0.3 log MAR) with normal binocular vision in 58 children over 7 months of age operated on for bilateral cataracts. Pseudophakic eyes regained visual acuity >20/63 (<0.5 log MAR) more often (90%) than aphakic eyes (46%) (p<0.001). Binocular vision was also achieved more often after IOL implantation (p<0.001). Visual outcome of early bilateral cataracts was less satisfactory in children with abnormal foveolar function. For 49 children who had surgery for unilateral cataracts, prognosis was poor when surgery was performed before the age of 7 months. For cataract surgery in older children (7 months) mean visual acuities were better with IOL implantation (p<0.05).
CONCLUSION—Cataract surgery with unilateral and bilateral IOL implantation can provide a beneficial effect on final visual outcome in children who are operated on before abnormal foveolar function develops.

Keywords: binocular vision; intraocular lens; paediatric cataract; visual outcome     

Local hypothermia protects the retina from ischaemic injury in vitrectomy

AIMS—Hypothermic irrigating solutions were used during vitrectomy in pressure induced ischaemic eyes so that their effects on retinal function and histological changes could be investigated.
METHODS—After anaesthetised albino rabbits underwent closed vitrectomy, their vitreous cavities were continuously irrigated for 30 minutes at a perfusion pressure of 140 mm Hg. The rabbits were divided into three groups according to their intraocular perfusion temperatures—8°C, 22°C, and 38°C. Electroretinograms were taken before and after irrigation. Glutamate levels in the vitreous were examined after irrigation. Eyes were enucleated on the seventh postoperative day and examined histologically.
RESULTS—On the seventh postoperative day, the recovery rate of a-wave amplitudes was significantly lower in the 38°C group than in the 8°C group, and that of b-wave amplitudes was significantly lower in the 38°C group than in either the 8°C or 22°C group. Retinal damage in the 38°C group revealed more severe histological impairment than in either the 8°C or 22°C group. Oedema of the inner retinal layer was significant in both the 22°C and 38°C groups. Glutamates reached peak values 30 minutes after the end of ischaemia in the 38°C group. However, no significant glutamate increases were detected 15 to 60 minutes after ischaemia in either the 8°C or 22°C group.
CONCLUSION—Local hypothermia during vitrectomy in acute ischaemic eyes appears to decrease retinal damage.

     

Interobserver and intraobserver reliability of a classification scheme for corneal topographic patterns

AIMS—To determine the interobserver and the intraobserver reliability of a published classification scheme for corneal topography in normal subjects using the absolute scale.
METHOD—A prospective observational study was done in which 195 TMS-1 corneal topography maps in the absolute scale were independently classified twice by three classifiers—a cornea fellow, an ophthalmic technician, and an optometrist. From these observations the interobserver reliability for each category and the intraobserver reliability for each observer were determined in terms of the median weighted kappa statistic for each category and for each observer.
RESULTS—For interobserver reliability, the median weighted kappa statistic for each category varied from 0.72 to 0.97 and for intraobserver reliability the range was 0.79 to 0.98.
CONCLUSION—This classification scheme is extremely robust and even in the hands of less experienced observers with minimal training it can be relied upon to provide consistent results.

     

An alternative and more cost effective method of delivery of radiotherapy in age related macular degeneration

AIMS/BACKGROUND—In the past 5 years there has been a dramatic increase in the use of radiotherapy to treat subfoveal neovascular membranes (NVMs) in both Europe and the USA despite the high cost. An alternative, more cost effective method of delivery using x ray simulation and bite block head fixation is described.
METHOD—15 patients were recruited with classic subfoveal NVMs. Head fixation was achieved with a customised Perspex mask for eight patients and a bite block for seven. An x ray simulator was used to check the field of irradiation. No computerised tomography (CT) was performed. All patients received a total dose of 13.3 Gy ionising radiation. Visual acuities were charted before and after treatment over a 24 month period.
RESULTS—After 24 months, 5/8 (67%) in the mask group showed stable visual acuities (less than two line change on Snellen chart) compared with 3/7 (43%) in the bite block group. This difference may be attributed to a variation in the pretreatment visual acuities in the two groups. From several studies it has been estimated that 24 months after diagnosis 28% untreated individuals would have stable vision compared with 53% patients in this study.
CONCLUSIONS—These results compare favourably with other studies and show that teletherapy can be a safe and effective form of treatment for subfoveal NVMs. The authors have described an alternative method of head fixation and shown that CT scanning is not essential. This method of delivery is considerably less costly than that traditionally used and may allow greater numbers of patients to benefit from radiotherapy treatment.

     

Epidemic optic neuropathy in primary school children in Dar es Salaam, Tanzania

BACKGROUND—An epidemic of bilateral optic neuropathy is affecting large numbers of people aged between 10 and 40 in Dar es Salaam, the capital city of Tanzania. The disease is characterised by acute onset of bilateral visual impairment, bilateral impairment of colour vision, and a characteristic temporal pallor of the optic discs. The disease often occurs in association with peripheral neuropathy and sensorineural hearing loss. This report presents the first data on disease prevalence in adolescents, based on a rapid assessment of schoolchildren.
METHODS—Three schools in Dar es Salaam were visited and all children aged between 10 and 16 were screened for the disease.
RESULTS—The prevalence of bilateral optic neuropathy among the schoolchildren is estimated to be 1.0% (95% CI 0.5-1.4%). This suggests that 5000 children (95% CI 2600-7300) aged 10-16 in Dar es Salaam may have the disease.
CONCLUSION—The results of this rapid assessment indicate this epidemic is a major public health problem. The prevalence of the disease in the community is likely to be far higher than found in this survey because children with the disease may have withdrawn from school. As the disease predominantly affects young adults, resulting in impaired vision and hearing, the economic and social consequences are enormous.

Keywords: optic neuropathy; schoolchildren; Tanzania     

Monocular optokinetic nystagmus in humans with age-related maculopathy

AIM—To investigate full field monocular optokinetic nystagmus (OKN) in patients with age-related maculopathy (ARM) and relative central scotoma.
METHODS—Six patients aged 59-88 years with bilateral ARM and an aged-matched control group of six patients aged 54-83 years were examined. Visual fields were assessed with a Humphrey field analyser using the threshold 30-1 routine. Monocular full field horizontal optokinetic stimuli were presented on a hemicylindrical screen subtending 172° horizontally and 50° vertically. The stimulus was a projected random dot pattern and three stimulus velocities were used, 30, 50, and 70°/s in both nasalward and temporalward directions. Each trial lasted between 30 and 40 seconds and eye movements were monitored using infrared oculography.
RESULTS—The ARM patients had relative central scotomas with an average depth of 10 dB. Neither the ARM nor the age-matched groups displayed any directional preponderance or a buildup of the slow phase eye velocity with time. No statistically significant difference in the gain was found between the two groups (p>0.05).
CONCLUSIONS—Marked central field loss in ARM does not significantly impair OKN gain. This supports the view that complete central retinal integrity is by no means essential and that the peripheral retina provides an important input to the generation of OKN.

     

BD8 certification of visually impaired people

BACKGROUND—There is debate as to the completeness of the blind and partial sight registers in England and Wales. The purpose of this study was to estimate the proportion of eligible visually impaired people attending the hospital eye service who have a BD8 certificate and to identify factors associated with not being certified.
METHODS—Cross sectional survey of patients attending outpatients by medical record review analysed by multiple logistic regression.
RESULTS—51% (43%, 58%) of patients identified as eligible for registration did not have a BD8 certificate. The severity of visual impairment and the main diagnosis in terms of requirements for treatment, permanence of visual loss, and visual field loss were independently associated with non-certification. A partially sighted patient is estimated to be three times more likely to not have a BD8 certificate as a blind patient of similar diagnosis (adj OR: 3.4 (95% CI: 1.7, 6.8)). A patient whose impairment is due to abnormal visual fields is estimated to be greater than three times more likely to be non-certified than one with low visual acuity of similar severity and cause (adj OR: 3.6 (95% CI: 1.0, 12.7)). People whose impairment is potentially reversible are estimated to be eight times ( 8.3 (2.2, 31.4)) more likely not to have a certificate compared with people who had permanent non-treatable visual loss; and in those with permanent visual loss, a requirement for ongoing treatment was found to be associated with a lower odds of certification.
CONCLUSIONS—These data strongly suggest that epidemiological data collected during registration are biased towards permanent, non-treatable causes of visual loss and those which affect central rather than peripheral vision. Certain subgroups of the visually impaired are likely to be at greater risk of non-certification. BD8 guidelines need to be simplified.

Keywords: registration; BD8 certification; data collection; visual impairment     

National survey of blindness and low vision in Lebanon

AIMS—To survey level of blindness and low vision in Lebanon.
METHODS—A population survey was undertaken in 10 148 individuals to measure the prevalence and identify the causes of blindness in Lebanon.
RESULTS—The prevalence of blindness was 0.6% and that of low vision 3.9%. The major causes of blindness were cataract (41.3%) and uncorrected large refractive error (12.6%).
CONCLUSION—Most causes of blindness in Lebanon can be controlled by various educational and medical programmes.

     

Retinopathy of prematurity: systemic complications associated with different anaesthetic techniques at treatment

BACKGROUND—Treatment of retinopathy of prematurity (ROP) in the UK is subject to considerable regional variation in terms of anaesthetic support. Change in practice at St Mary's neonatal medical unit from topical to general anaesthesia and, subsequently, to sedation/analgesia allowed comparison of the impact of these three modalities on infants' early postoperative course in a consecutive, non-randomised, observational study.
METHODS—The study population consisted of 30 babies undergoing treatment of threshold ROP. Twelve were treated using topical anaesthesia alone (group A), six using general anaesthesia (group B), and 12 using sedation/analgesia combined with elective intubation and artificial ventilation (group C). Daily measurements of infant health were recorded starting 4 days preoperatively and continuing for 7 days postoperatively to facilitate the formulation of a cardiorespiratory stability index as follows: (0) improvement from baseline, (1) no change from baseline, (2) mild instability, (3) marked instability, and (4) life threatening event.
RESULTS—Within the first 48 hours postoperatively in group A 5/12 showed mild instability and 4/12 showed marked instability (including three babies suffering life threatening events requiring emergency resuscitation). In group B within the first 48 hours postoperatively 1/6 showed mild and 1/6 showed marked instability, and in group C 5/12 babies showed mild instability alone. There was a significant difference for cardiorespiratory stability scores between the three groups overall for the 7 days postoperatively (repeated measures ANOVA, p = 0.018).
CONCLUSIONS—Premature infants undergoing cryotherapy for ROP who were treated using topical anaesthesia alone had more severe and protracted cardiorespiratory complications.

     

"Johnny Poppers": a cause of serious ocular injury

AIMS/BACKGROUND—The causes of blunt ocular trauma are many and diverse. We present two cases of ocular injury caused by an unusual form of weapon called a "Johnny Popper". There follows a theoretical and experimental evaluation of the velocity of the projectiles fired by this device.
METHODS—A Johnny Popper was constructed under expert guidance. The elastic properties of the device were measured and this allowed calculation of a theoretical exit velocity of the projectiles fired. The weapon was subsequently fired under test conditions which permitted the exit velocity of the projectiles fired to be measured directly.
RESULTS—The theoretical velocity of the projectiles was calculated as 80 ms^-1 and the experimentally measured velocity was 57 ms^-1.
CONCLUSIONS—Johnny Poppers are a previously undescribed and unique form of home made weapon. They are intended for playful mischief, but have the potential to cause serious ocular trauma.

     

Reliable keratometry with a new hand held surgical keratometer: calibration of the keratoscopic astigmatic ruler

AIM—Some surgeons consider hand held surgical keratometers unreliable. This may be due to incorrect use through not realising that the distance that the keratometer is held from the cornea influences the shape of the image. When a keratometer is held closer to the astigmatic cornea, the elliptical image will appear more circular, particularly for larger degrees of astigmatism. However, the keratoscopic astigmatic ruler (KAR) has design features that correct the hitherto unrecognised problems with the use of a hand held keratometer. This study assesses the reliability and accuracy of measurement of astigmatism using the KAR.
METHODS—The KAR and the Bausch & Lomb keratometer (B&L) were compared using six back surface toric cut contact lens blanks representing 1 to 6 dioptres of astigmatism. Two observers (one experienced in the use of the keratometers, the other a novice) took eight randomly repeated "masked" measurements of each lens blank with the KAR and four measurements with the B&L in a similar fashion.
RESULTS—There was no difference between the measurements with either instrument by each of the observers (p=0.95, ANOVA). The standard error of measurement for the KAR was 0.59 D, for the B&L, 0.31 D. The intraclass correlation coefficient of reliability for the KAR was 0.90 and for the B&L it was 0.97. The coefficient of repeatability for the KAR was plus or minus 0.83 D, and for the B&L plus or minus 0.77 D. The interobserver reliability for the KAR was 0.898, and for the B&L, 0.975.
CONCLUSION—These results suggest that the KAR has good reliability and reproducibility and compares favourably with the B&L keratometer. Inexperience with use does not affect reliability.

     

Movement hyperacuity in childhood amblyopia

BACKGROUND—Amblyopia results in deficits in a number of visual functions in both the amblyopic and dominant eye. The present work describes oscillatory movement displacement thresholds (OMDT) in childhood amblyopia.
METHODS—The OMDT from the dominant and amblyopic eyes of 50 orthoptic patients (aged 74 (SD 16) months) were compared with those from a group of 24 controls (79 (21) months). OMDT were measured using a forced choice staircase procedure. Subjects were asked to identify which of the computer controlled monitors displayed the oscillating stimulus. Visual acuity and stereoscopic responses were noted from clinical records.
RESULTS—Amblyopic children demonstrating stereopsis showed no significant OMDT deficit in the amblyopic eye. Those children having no stereopsis had elevated OMDT in the amblyopic eye (p<0.05). Results suggest that the dominant eye of children with amblyopia may also have a pattern of visual development which is anomalous (difference in correlation coefficient with age; p <0.05).
CONCLUSION—OMDT deficits demonstrated in some amblyopic eyes indicate that amblyopia is incompletely described by its "clinical" definition. Results suggest that the dominant eye in those with unilateral amblyopia may not be "normal".

Keywords: amblyopia; children; vision; movement hyperacuity; stereopsis     

Intraocular pressure and central visual field of normal tension glaucoma

AIM—To study whether damage in the central 30° field of normal tension glaucoma (NTG) is relatively heterogeneous or homogeneous with respect to intraocular pressure (IOP) related damage.
METHODS—Using the results of Humphrey perimeter examinations, the central 30° field was divided into four subfields; superior and inferior hemifields excluding the caecocentral field (30-2 program) and superior and inferior 10° hemifields (10-2 program). In 103 NTG cases, the intraindividual bilateral difference in the mean of total deviations (mean TD) in the four subfields was analysed by multiple linear regression to correct the effects of factors other than IOP. Explanatory variables were the intraindividual bilateral difference in the mean of clinic IOP (IOP_mean), that in the ratio of area of peripapillary atrophy corresponding to each subfield to disc area, and that in myopic refraction.
RESULTS—The intraindividual bilateral difference in the mean TD was significantly and negatively correlated with that in IOP_mean in three of the above four subfields (p<0.005) and correlation tended to be negative (p=0.07) in the superior 10° hemifield.
CONCLUSIONS—Diffuse IOP related damage was suggested in the central 30° field of NTG; greater extent of the damage in the above four subfields was correlated with higher mean IOP. The present findings may have clinical implications.

     

Endogenous cortisol profile in patients with central serous chorioretinopathy

AIM—To study the endogenous cortisol levels in patients with central serous chorioretinopathy (CSCR).
METHODS—Endogenous cortisol levels in urine and plasma were determined in 30 patients with acute CSCR and compared with 30 age and sex matched controls.
RESULTS—The mean values of the 8 am plasma cortisol (29.97 µg/dl v 18.76 µg/dl), 11 pm plasma cortisol (22.03 µg/dl v 13.06 µg/dl), and 24 hour urine cortisol (11.01 mg/24 h v 7.39 mg/24 h) revealed significantly higher values in the patient group (p<0.001).
CONCLUSIONS—Increased levels of endogenous cortisol are present in patients with CSCR.

     

Difficulty in performing everyday activities in patients with juvenile macular dystrophies: comparison with patients with retinitis pigmentosa

AIMS—To ascertain the level of perceived difficulty experienced by patients with central vision loss due to juvenile macular dystrophies in the performance of everyday activities. A second objective was to compare their perceived difficulty with that of patients with retinitis pigmentosa (RP) with primarily peripheral vision loss.
METHODS—72 patients with Stargardt disease, cone dystrophy, or cone-rod dystrophy who had visual acuities worse than 20/40 and normal peripheral visual fields rated themselves on their difficulty in the performance of 33 activities encompassing a wide variety of everyday tasks. These findings were compared with the responses of 120 patients with typical RP or Usher syndrome type 2 who had visual acuities of 20/40 or better and peripheral visual field loss.
RESULTS—The juvenile macular dystrophy group reported the greatest level of overall self perceived difficulty with activities involving central vision, and lesser and variable degrees of difficulty with items within the mobility, negotiating steps, driving, and miscellaneous categories. Consistent with these findings, there were highly significant correlations between subjects' rated performances of activities involving central vision and the clinical measures of vision, including visual acuity and size of central scotoma. There were fewer significant correlations between perceived performance of activities in the other categories and the clinical measures. In general, those activities that showed significant correlations with the clinical measures of vision for the patients with juvenile macular dystrophies also showed significant differences in the patterns of responses between the juvenile macular dystrophy group and the RP group. Those items which were not correlated with the clinical measures in the juvenile macular dystrophy group tended not to show significant differences in the response patterns between the two groups.
CONCLUSION—These results provide insight into the types of perceived difficulties in performing tasks of everyday life in patients with these disorders which affect counselling of these patients.

Keywords: vision; impairment; everyday activities; juvenile macular dystrophy     

Electrophysiological evaluation of visual loss in Müller cell sheen dystrophy

AIMS—To describe the clinical picture and electrophysiological findings in Müller cell sheen dystrophy, a recently reported retinal dystrophy.
METHOD—A basic ophthalmological evaluation as well as recording of standard electro-oculography and electroretinography were performed in one patient at the onset of visual loss and after 1 year of follow up.
RESULTS—A 61 year old woman presented with visual loss in the right eye. Multiple folds at the level of the internal limiting membrane were seen at the posterior pole in both eyes. Macular oedema was present in the right eye. The visual acuity of the right eye was 6/30 and of the left 6/9. A paracentral scotoma was found in the right eye. Electro-oculographic examination of both eyes gave normal results. Electroretinography (ERG) revealed reduced b-wave and flicker amplitudes in the right eye; these potentials were normal for the left eye. The ON response in the right eye was reduced and delayed; it was normal in the left eye. A further loss of visual function was noted 1 year later in the right eye, but the ophthalmoscopic findings were unchanged. The ERG of the right eye had a negative waveform when dark adapted. Light adapted responses showed an unusual delayed b-wave, broad and delayed ON and OFF responses and a missing flicker response, suggesting a Müller cell dysfunction. Light adapted responses were slightly reduced in the left eye.
CONCLUSIONS—Electrophysiological data indicate Müller cell dysfunction as a background of functional loss in Müller cell sheen dystrophy. This is in agreement with previously reported histological findings in this disorder.

Keywords: internal limiting membrane; electroretinography; retinal degeneration; Müller cells