Christopher B O Yu

Changing patterns of strabismus: a decade of experience in Hong Kong

Background/aims: Racial variation in the pattern of strabismus is known, but few large scale studies on non-white populations are available. Furthermore, longitudinal change in this pattern within a local setting has not been well documented in the past. This study aims to support the clinical impression that exotropia is more common in Chinese patients, and that the proportion of patients with exotropia has been increasing in the past decade. Methods: A total of 2704 consecutive patients with the diagnosis of primary horizontal strabismus, seen in the strabismus clinic of the Hong Kong Eye Hospital, were retrospectively analysed to determine the relative prevalence of esotropia and exotropia. Characteristics recorded include patient demographics, type of strabismus, and whether the nature of the squint was constant or intermittent. Results: 742 (27.4%) patients were found to have esotropia, 548 (20.3%) had constant exotropia, 1213 (44.9%) had intermittent exotropia, and 201 (7.4%) had microtropia. The proportion of exotropic to esotropic patients was shown to increase steadily throughout the past decade (p<0.0001). This was mainly accounted for by an increase in the number of patients with intermittent exotropia, and a corresponding decrease in the number of patients with esotropia. Conclusion: Exotropia was shown to be more prevalent than esotropia in a Hong Kong Chinese population. Furthermore, the proportion of patients with intermittent exotropia appears to be increasing, in contrast with esotropic patients. The exact nature of this trend, and possible aetiological factors will require further study.

Ocular hypertensive and anti-inflammatory responses to different dosages of topical dexamethasone in children: a randomized trial.

Background:  The purpose of the present study was to investigate the ocular hypertensive and anti‐inflammatory responses to two different dosage schedules of 0.1% topical dexamethasone in a population of Chinese children undergoing strabismus surgery.

25-Gauge transconjunctival sutureless vitrectomy system in the surgical management of children with posterior capsular opacification

Purpose:  To evaluate the safety and efficacy of the 25‐gauge transconjunctival sutureless vitrectomy (TSV) system in the surgical management of posterior capsular opacification (PCO) in pseudophakic children.

Comparison of lidocaine 2% gel versus amethocaine as the sole anesthetic agent for strabismus surgery

PURPOSE To compare the efficacy of lidocaine 2% gel with amethocaine 1% eyedrops as the sole anesthetic agent for one-stage adjustable suture strabismus surgery. DESIGN Prospective, double-masked randomized trial. PARTICIPANTS Fourteen consecutive patients scheduled to undergo bilateral and symmetrical strabismus surgery under topical anesthesia in one institution. METHODS Each patient was randomized to receive lidocaine 2% gel in one eye and amethocaine 1% eyedrops in the other eye as the sole anesthetic agent for surgery. Masking of the patient and surgeon was ensured by administration of a placebo gel and eyedrop as part of the regimen. Pain and discomfort were assessed via a 10-cm visual analog scale. MAIN OUTCOME MEASURES Subjective pain and discomfort perceived during surgery were assessed separately by the patient and the surgeon, and the need for any additional anesthesia was recorded. RESULTS A total of 14 subjects indicated mean pain and discomfort scores of 2.6 and 3.2 respectively, for lidocaine gel, and 5.3 and 6.2, respectively, for amethocaine drops (P = 0.01). The mean number of additional drops required by eyes randomized to lidocaine gel was 0.3, compared with 1.6 for amethocaine drops (P = 0.02). CONCLUSIONS In terms of pain control, lidocaine 2% gel alone is a superior topical anesthetic for one-stage adjustable suture strabismus surgery when compared with amethocaine 1% eyedrops.

Comparative study on the safety and efficacy of different cycloplegic agents in children with darkly pigmented irides

Background: The ideal cycloplegic drug that is safe, effective and convenient in children is not yet available. This study aimed to evaluate the safety and efficacy of three cycloplegic regimens in hyperopic children with pigmented irides. The responses to cycloplegia in different age groups and presence of strabismus were also compared.

Changes in refraction and ocular dimensions after cataract surgery and primary intraocular lens implantation in infants

PURPOSE: To study refraction and axial length changes after cataract extraction and primary intraocular lens (IOL) implantation in children younger than 1 year of age. SETTING: Two regional hospitals. METHODS: After determining the IOL power for emmetropia, 80% of the value was used to choose the IOL for implantation to counter anticipated myopic shift with age. The main outcome measures were changes in refraction and axial length 3 years after surgery. RESULTS: Thirty‐four eyes of 20 children (mean age 6.7 months ± 3.9 [SD]) were studied. Refraction in the immediate postoperative period was +4.53 ± 1.45 diopters (D). Three years after surgery, the mean refraction was −2.49 ± 3.08 D (P<.001). Twenty‐two eyes (64.7%) had surgery during the first 6 months of life (group 1) and had a shorter axial length at surgery (mean 18.92 ± 1.32 mm) compared with 12 eyes (35.3%) that received surgery between 7 and 12 months (group 2, mean 20.29 ± 1.00 mm) (P = .007). However, the final axial length was greater in group 1 (mean 22.67 ± 1.04 mm) than in group 2 (mean 21.23 ± 0.26 mm) (P = .019). CONCLUSIONS: Primary IOL implantation is an option for children having cataract surgery in the first year of life. Significant myopic shifts occurred, and this seemed to be more pronounced in younger children. It appears that rethinking current strategies for IOL power calculation may be required to achieve more optimal refractive outcomes.

Cystoid macular edema after pediatric intraocular lens implantation: fluorescein angioscopy results and literature review

Purpose: To evaluate the occurrence of cystoid macular edema (CME) after lens extraction, anterior vitrectomy, and intraocular lens implantation (IOL) in children using angioscopy after administration of oral fluorescein. Setting: Centers in Tamil Nadu, India, and Hong Kong, China. Methods: This study comprised 18 children (28 eyes) who had cataract extraction, posterior capsulorhexis, anterior vitrectomy, and in‐the‐bag IOL implantation. The presence of CME was evaluated 1 week and 4 to 6 weeks after surgery using fluorescein angioscopy. Results: Anterior chamber fibrin occurred in 4 eyes (14.3%). Fluorescein angioscopy was performed 1 week after surgery in all eyes and after 1 month in 25 eyes (89.3%). No eye demonstrated the presence of CME on fluorescein angioscopy. Conclusions: Cystoid macular edema did not occur in the early period after pediatric cataract surgery using current surgical techniques. Longer follow‐up is required to ascertain the incidence of CME in the late postoperative period.

Residual torticollis in patients after strabismus surgery for congenital superior oblique palsy

Aim: To study postoperative residual vertical deviation and abnormal head posture (AHP) after surgical treatment for congenital superior oblique palsy (SOP). Method: Children with both SOP and AHP who underwent extraocular muscle surgery for correction of AHP were recruited. The patients received complete ophthalmic and orthopaedic examinations. Residual AHP was classified according to severity of face turn, head tilt and chin elevation. Results: Thirty-two children with mean age at operation of 82.6 months were recruited, with mean follow-up of 37.9 months. Of these children, 65.6% had a postoperative vertical deviation of less than three prism dioptres. In addition, 34.4% patients had resolved (0°), 34.4% had mild (1°–10°), and 31.3% had significant residual torticollis (>10°). Of the patients with significant residual torticollis, 33.3% had ocular causes. The mean age at operation for the patients with residual torticollis (95.9 months) was older than those without torticollis (79.9 months) (p = 0.018). Residual torticollis was found to be related to sternocleidomastoid muscle tightness (p = 0.013). Conclusion: The success rate for eliminating significant AHP after strabismus surgery for patients with congenital SOP was 68.8%. Early surgery was associated with a better outcome. Association was also found between sternocleidomastoid tightness and AHP. A multidisciplinary approach is recommended in the management of torticollis as ophthalmic and orthopaedic comorbidities can coexist.

Topical mydriatic and cycloplegic spray for Chinese children.

PURPOSE To assess the efficacy and tolerance of mydriatic and cycloplegic spray versus drops for Chinese children. METHODS The effects of the spray (cyclopentolate 0.25%, phenylephrine 0.625%, and tropicamide 0.5%) and the drops (cyclopentolate 1%, phenylephrine 0.5%, and tropicamide 0.5%) were evaluated in 29 children (58 eyes) in two separate sessions. There was a 1-week period between the applications of the spray and the drops. Dilated pupil size and refraction after cycloplegia were the primary outcome variables used to assess the efficacy. A subjective discomfort score was used to assess acceptance of the spray and the drops. RESULTS The mean age of the study population was 4.33 +/- 1.39 years (range, 3 to 8 years). The mean pupil size was 6.9 mm for the spray and 6.6 mm for the drops. The spray appeared to be slightly more effective than the drops, with a mean difference of 0.3 mm that was statistically significant (P = .001, two-tailed t test). No statistically significant difference in cycloplegic response was found between the spray and the drops (P = .535, two-tailed t test). Administration of the spray caused less discomfort than did administration of the drops (P < .001, Wilcoxon signed-rank test). CONCLUSIONS The spray system appears to be clinically equivalent to the drops for achieving effective pupil dilation and cycloplegia, even in a population with dark irides such as ours. Tolerability and acceptance improved because the spray was applied to the closed eyelids.

Allelic imbalance at 13q31 is associated with reduced GPC6 in Chinese with sporadic retinoblastoma

Background/aims Loss of heterozygosity (LOH) has been discovered in retinoblastoma (RB) in previous studies. In this study, we aimed to discover potential tumour suppressor genes through investigation of the incidence of allelic loss in chromosome 1, 6, 9, 13, 19, 20, 21, 22 and X in Chinese sporadic retinoblastoma patients and to study the expression of genes flanking LOH region 13q31. Methods Twenty-five microdissected RB samples were analysed to investigate the LOH in 140 microsatellite markers. Expression of genes flanking D13S265 was investigated by real-time quantitative-PCR on available frozen samples. The promoter and entire coding region of GPC6 were examined for sequence changes in an extended batch of 29 RB samples. Results Allele losses were found in 92% (23/25) of the tumours. We identified a new LOH locus at 13q31 (D13S265) with a high occurrence rate (67%, 14/21) apart from the RB1 locus (68%, 17/25). Expression study detected the reduced expression of Glypican 6 (GPC6) transcript significantly associated with the LOH at 13q31 (p=0.024). Furthermore, mutation screening revealed no remarkable sequence alteration in GPC6 that could affect its expression. Conclusion Results suggest that a reduction in GPC6 mRNA in retinoblastoma is associated with the non-random allelic loss at 13q31 that could contribute to RB development.