Kah-Guan Au Eong

Prevalence of Amblyopia and Strabismus in Young Singaporean Chinese Children

PURPOSE. To determine the prevalence of amblyopia and strabismus in young Singaporean Chinese children. METHODS. Enrolled in the study were 3009 Singaporean children, aged 6 to 72 months. All underwent complete eye examinations and cycloplegic refraction. Visual acuity (VA) was measured with a logMAR chart when possible and the Sheridan-Gardner test when not. Strabismus was defined as any manifest tropia. Unilateral amblyopia was defined as a 2-line difference between eyes with VA < 20/30 in the worse eye and with coexisting anisometropia (> or =1.00 D for hyperopia, > or =3.00 D for myopia, and > or =1.50 D for astigmatism), strabismus, or past or present visual axis obstruction. Bilateral amblyopia was defined as VA in both eyes <20/40 (in children 48-72 months) and <20/50 (<48 months), with coexisting hyperopia > or =4.00 D, myopia < or = -6.00 D, and astigmatism > or =2.50 D, or past or present visual axis obstruction. RESULTS. The amblyopia prevalence in children aged 30 to 72 months was 1.19% (95% confidence interval [CI], 0.73-1.83) with no age (P = 0.37) or sex (P = 0.22) differences. Unilateral amblyopia (0.83%) was twice as frequent as bilateral amblyopia (0.36%). The most frequent causes of amblyopia were refractive error (85%) and strabismus (15%); anisometropic astigmatism >1.50 D (42%) and isometropic astigmatism >2.50 D (29%) were frequent refractive errors. The prevalence of strabismus in children aged 6 to 72 months was 0.80% (95% CI, 0.51-1.19), with no sex (P = 0.52) or age (P = 0.08) effects. The exotropia-esotropia ratio was 7:1, with most exotropia being intermittent (63%). Of children with amblyopia, 15.0% had strabismus, whereas 12.5% of children with strabismus had amblyopia. CONCLUSIONS. The prevalence of amblyopia was similar, whereas the prevalence of strabismus was lower than in other populations.

Effects of indocyanine green injection on the retinal surface and into the subretinal space in rabbits.

Purpose To evaluate the effects of indocyanine green (ICG) injection on the retinal surface and into the subretinal space of rabbit eyes. Methods Twenty-two Dutch-belted rabbits underwent two-port vitrectomy followed by injection of ICG (5 mg/mL) on the retinal surface and into the subretinal space. Balanced salt solution (BSS) was also injected subretinally. The locations where ICG was delivered (both epiretinal and subretinal) were exposed to light from an endoilluminator for 7 minutes. The animals were examined at 1, 7, and 14 days after surgery. The eyes were studied by fluorescein angiography as well as light and electron microscopy. Results No damage was observed after epiretinal ICG injection, but subretinal ICG injection resulted in damage to the outer nuclear layer, photoreceptor inner and outer segments, and retinal pigment epithelium. This damage was more severe with longer follow-up. Control experiments without ICG, in which balanced salt solution was injected into the subretinal space or light was delivered on the epiretinal surface, demonstrated only damage to the photoreceptor outer segments. Conclusion Subretinal delivery of ICG (5 mg/mL) in rabbits induces retinal pigment epithelium, photoreceptor inner and outer segment, and outer nuclear layer damage. These mechanisms of damage may explain the retinal pigment epithelium changes that are sometimes seen after ICG-assisted internal limiting membrane peeling in humans.

Family history, near work, outdoor activity, and myopia in Singapore Chinese preschool children

Aims To investigate the risk factors for myopia, including near work and outdoor activity, in Singapore Chinese preschool children. Methods A cross-sectional study, with disproportionate random sampling by 6-month age groups, of 3009 Singapore Chinese children aged 6–72 months was performed. Information on family history, near work and outdoor activity was obtained. Spherical equivalent refraction (SER) was assessed. Results Children with two myopic parents were more likely to be myopic (adjusted OR=1.91; 95% CI 1.38 to 2.63) and to have a more myopic SER (regression coefficient=−0.35; 95% CI −0.47 to −0.22) than children without myopic parents. For each 1 cm taller height, the SER was more myopic by 0.01 dioptres. Neither near work nor outdoor activity was associated with preschool myopia. Conclusions A family history of myopia was the strongest factor associated with preschool myopia. In contrast, neither near work nor outdoor activity was found to be associated with early myopia. These data suggest that genetic factors may play a more substantial role in the development of early-onset myopia than key environmental factors.

Subjective visual experience during phacoemulsification and intraocular lens implantation under topical anesthesia.

OBJECTIVE The aim of this study was to investigate the subjective visual experience of patients during phacoemulsification and intraocular lens (IOL) implantation under topical anesthesia. DESIGN Postoperative questionnaire survey. PARTICIPANTS The study cohort consisted of 52 patients with cataracts. There were 18 male (34.6%) and 34 female (65.4%) patients. Their mean (+/- SD) age was 67.5 (+/-10.8) years. INTERVENTION The patients underwent routine phacoemulsification and IOL implantation under topical anesthesia. MAIN OUTCOME MEASURES The patients were interviewed on the same day after their operation regarding their visual experience in the operated eye during surgery. RESULTS All patients (100%) reported that they could see at least some light during the surgery. Some patients reported they could also see one or more colors (50 patients, 96.2%), movements (32 patients, 61.5%), flashes (24 patients, 46.2%), the surgeons fingers/hands (13 patients, 25%), instruments (12 patients, 23.1%), and/or the surgeon (4 patients, 7.7%). The colors seen included red (24 patients, 46.2%), yellow (23 patients, 44.2%), blue (12 patients, 23.1%), green (7 patients, 13.5%), and orange (6 patients, 11.5%). Eight patients (15.4%) saw the spectrum of colors similar to that of the rainbow. Twenty-four patients (46.2%) reported that the brightness of light changed during the course of the operation. Eight patients (15.4%) found their visual experience frightening. There was no statistically significant association between those who found the visual experience frightening and the sex or age of the patient, a history of cataract operation in the fellow eye, the type of visual sensation experienced, or the presence of coexisting ocular pathology. CONCLUSION All patients undergoing phacoemulsification under topical anesthesia experience a variety of visual sensations that may be frightening in a small proportion of patients.

The prognostic significance of a system for classifying mechanical injuries of the eye (globe) in open-globe injuries.

PURPOSE The aim of this study was to determine the prognostic significance of a previously published system for classifying mechanical injuries of the eye (globe) in open-globe injuries. METHODS The medical records of 150 patients with open-globe injuries identified from an established institutional database were retrospectively reviewed to classify all injuries at presentation by the four specific variables of the classification system: type of injury, defined by the mechanism of injury; grade of injury, defined by visual acuity in the injured eye at initial examination; pupil, defined as the presence or absence of a relative afferent pupillary defect in the injured eye; and zone of injury, defined by the location of the eye-wall opening. Final visual outcomes for these injuries were also recorded. Logistic regression models were used to analyze the data and to determine whether relationships existed between the specific classification variables and final visual acuity in the injured eyes. RESULTS All four classification variables were significant predictors of visual outcome. When adjusted for the other variables, grade and pupil were the most significant predictors of final visual acuity. CONCLUSION This system for classifying mechanical injuries of the eye appears to be prognostic for visual outcomes in open-globe injuries. In particular, the measurement of visual acuity and testing for a relative afferent pupillary defect at the initial examination should be performed in all injured eyes because of their relative prognostic significance.

Effects of intravitreal indocyanine green injection in rabbits.

Purpose To report the clinical, electrophysiologic, and histologic findings of different concentrations of indocyanine green (ICG) injected into the vitreous cavity of rabbit eyes. Methods Forty-two rabbits underwent intravitreal injection of 0.1 mL of ICG in three different concentrations: 0.5 mg/mL (250 mOsm), 5 mg/mL (270 mOsm), and 25 mg/mL (170 mOsm). Fellow eyes were injected with 0.1 mL of balanced salt solution. Biomicroscopy, ophthalmoscopy, electroretinography, fluorescein angiography, and histologic evaluation were performed. Results Eyes injected with 0.5 mg/mL of ICG showed b-wave latency delay on the first day after injection. Eyes injected with 5 mg/mL of ICG showed b-wave latency delay and decreased b-wave amplitude on the first and seventh days after injection; delayed a-wave latency on the first day after injection was also observed. Eyes injected with 25 mg/mL of ICG showed b- and a-wave amplitude and latency abnormalities during the entire follow-up. Direct correlation of increasing retinal edema proportional to the progressively increasing ICG concentrations was shown on histologic evaluation. Conclusion Intravitreal ICG injection in rabbit eyes may impair retinal function and morphology proportional to the progressively increasing ICG dosages.

Incidence of eyelid cancers in Singapore from 1968 to 1995

AIM To describe the epidemiological characteristics of patients with eyelid malignancies seen in all hospitals in Singapore from 1968 to 1995. METHOD The Singapore Cancer Registry has been collecting epidemiological data of all cancers seen in Singapore since 1968. The data of all cases of Singapore residents with eyelid cancers diagnosed from 1968 to 1995 (ICD-9, sites 172.1 and 173.1) were retrieved for analysis. RESULTS There were 162 male patients (49.8%) and 163 females (50.2%). The median age at diagnosis was 63 years in males and 66 years in females. The average annual age standardised incidence rate among male Singapore residents was 6.5 per million and 5.5 per million among female Singapore residents. Between 1993 and 1995, the average annual rate for females was 6.8 per million, compared with 3.1 per million between 1968 and 1972. The most common cancer was basal cell carcinoma (84.0%), followed by sebaceous adenocarcinoma (10.2%) and squamous cell carcinoma (3.4%). CONCLUSION The annual age standardised incidence for male residents has remained relatively stable. The incidence for female residents has shown a steady increase over the past 28 years. The incidence for males is generally higher than that for females. These expanded epidemiological characteristics may serve to provide a foundation to monitor future disease patterns and to promote further research into the aetiology of these cancers.

Utility values associated with vitreous floaters.

PURPOSE To ascertain the health-related quality of life associated with symptomatic degenerative vitreous floaters. DESIGN Cross-sectional questionnaire survey. METHODS In this institution-based study, 311 outpatients aged 21 years and older who presented with symptoms of floaters were enrolled. Data from 266 patients (85.5%) who completed the questionnaire were analyzed. Utility values were assessed using a standardized utility value questionnaire. The time trade-off (TTO) and standard gamble (SG) for death and blindness techniques were used to calculate the utility values. Descriptive, univariate, and multivariate analyses were performed using Stata Release 6.0. RESULTS The mean age of the study population was 52.9 ± 12.02 years (range, 21-97). The mean utility values were 0.89, 0.89, and 0.93 for TTO, SG (death), and SG (blindness), respectively. Patients aged ≤55 years reported significantly lower SG (blindness) utility values when compared with patients above 55 years of age (age ≤55 = 0.92, age >55 = 0.94, P = .007). Utility measurements did not demonstrate significant relationship with any of the other socio-demographic variables examined in this study. The utility values did not demonstrate any significant relationship with other ocular characteristics such as duration of symptoms, presence of a posterior vitreous detachment, and presence or severity of myopia. CONCLUSIONS Symptomatic degenerative vitreous floaters have a negative impact on health-related quality of life. Younger symptomatic patients are more likely to take a risk of blindness to get rid of the floaters than older patients.

Eye cancer incidence in Singapore.

AIM To describe the epidemiological characteristics of patients with primary intraocular, conjunctival, and orbital cancers seen in Singapore from 1968 to 1995. METHODS Epidemiological data of all cancers diagnosed in Singapore are collected by the Singapore Cancer Registry. The data of all cases of Singapore residents with eye cancers (ICD-9, site 190) were retrieved for analysis. This includes intraocular, conjunctival, and orbital cancers but excludes cancer of the eyelids. RESULTS There were 125 patients of which 67 (53.6%) were male and 58 (46.4%) were female. The average annual age standardised incidences for male and female Singapore residents were 1.89 and 1.81 per million respectively. The most common cancer was retinoblastoma (53.6%), followed by malignant melanoma (19.2%) and squamous cell carcinoma (11.2%). The most common cancer among patients younger than 15 years was retinoblastoma (95.7%) and that for those 15 years and older was malignant melanoma (42.6%). The most common subsite was the retina (53.6%), followed by conjunctiva (12.8%), orbit (8.8%), and lacrimal gland (6.4%). CONCLUSION The annual age standardised incidence have been stable for the 28 years studied. Retinoblastoma is much more common than melanoma in Singapore. These expanded epidemiological characteristics serve to provide ophthalmologists and epidemiologists with a foundation to monitor future disease patterns in Singapore and provide a basis for comparison with other selected populations elsewhere.

Endogenous Klebsiella endophthalmitis.

Purpose To report 4 cases of endogenous Klebsiella endophthalmitis. This disease is a rare but devastating complication of Klebsiella sepsis. Familiarity with its varied clinical presentations would aid in early diagnosis and institution of appropriate therapy.Methods We report 5 eyes of 4 patients with endogenous Klebsiella endophthalmitis from December 1995 to September 1996 and review the literature regarding previously successfully treated cases.Results The mean age of the patients was 67.5 years (range 37–85 years). One patient had bilateral involvement. At presentation, 3 eyes had a visual acuity of no perception of light (NPL) and the 1 patient with bilateral involvement had an acuity of counting fingers in one eye and 20/40 in the other. The primary source of sepsis was the pulmonary system in 2 patients, the hepatobiliary system in 1 patient and the urinary tract in 1 patient. One patient had coexisting diabetes mellitus. Two patients had a pupillary hypopyon. Local and systemic treatment with an aminoglycoside and cephalosporin was initiated. Despite treatment, 2 eyes remained NPL. One eye developed a globe perforation and was eviscerated. The patient with bilateral involvement was treated within 8 h and recovered fully with a final visual acuity of 20/20 in both eyes.Conclusion It is important to have a high index of suspicion in patients with septicaemia presenting with intraocular inflammation, especially in diabetics with suppurative liver disease, urinary tract infection or pulmonary infection. As the visual prognosis for patients with Klebsiella endophthalmitis is generally poor, early diagnosis and treatment with intravenous and intravitreal antibiotics may improve the visual outcome.