Gerard Nah

Ophthalmic complications of dengue.

A case series suggests that the spectrum of complications in dengue infection is widening.

Differences in Prevalence of Refractive Errors in Young Asian Males in Singapore between 1996-1997 and 2009-2010

Abstract Purpose: To determine the differences in prevalence rates of refractive errors in young Singaporean males over a 13-year period between 1996–1997 and 2009–2010 Methods: Non-cycloplegic autorefraction data were obtained in a survey of 15,085 young male subjects (mean age 19.5 ± 1.4 years, range 16–25 years) in 1996–1997 using a Nikon NRK-8000 autorefractor. A second survey of 28,908 male subjects (mean age 19.8 ± 1.2 years, range 17–29 years) was conducted in 2009–2010 using a Huvitz MRK-3100 autorefractor. Results: The overall prevalence of myopia (spherical equivalent, SEq, worse than −0.5 diopters, D) was similar in 2009–2010 (81.6%) and 1996–1997 (79.2%; odds ratio 1.38, 95% confidence interval 1.31–1.46; p < 0.001). The prevalence of high myopia (SEq worse than −6.0D) increased from 13.1% in 1996–1997 to 14.7% in 2009–2010 (p < 0.001). The prevalence of refractive astigmatism increased significantly from 41.4% in 1996–1997 to 50.9% in 2009–2010 (p < 0.001). Conclusions: Our results show that the prevalence of myopia and high myopia remained high and the prevalence of astigmatism increased in young male adults in Singapore over a 13-year period after controlling for age, education and ethnicity.

Choroidal thickness and high myopia: a case-control study of young Chinese men in Singapore.

To determine the distribution of choroidal thickness (CT) and ocular factors associated with CT in high myopic eyes in comparison with emmetropic eyes of young healthy adults.

Peripapillary choroidal thickness in young Asians with high myopia.

PURPOSE To describe the topography and predictors of peripapillary choroidal thickness (PPCT) in highly myopic eyes of young, healthy, Asian subjects. METHODS A total of 870 young male subjects aged 21.63 ± 1.15 years were recruited from the Singapore military. Choroidal imaging was performed using enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT). Peripapillary choroidal thickness was manually measured at eight locations around the optic disc. RESULTS We analyzed 448 subjects with high myopia (defined as spherical equivalent [SE] worse than -6.0 diopters [D]) and 116 with emmetropia (SE > -0.5 and < 0.5 D). The mean SE was -8.52 ± 1.20 D for the high-myopic group, and 0.11 ± 0.24 D for the emmetropic group. The mean peripapillary choroid was significantly thinner (142.62 ± 43.84 μm) in high myopes compared with emmetropes (181.90 ± 46.43 μm, P < 0.001). Likewise, PPCT showed further decrease with increase in degree of myopic refractive error. Distribution of PPCT showed a markedly different pattern in high-myopic eyes (thickest superiorly) and emmetropic eyes (thickest temporally). However, peripapillary choroid in both the groups was thinnest at the inferior location. Among the ocular factors studied, axial length, IOP, presence of posterior staphyloma, and chorioretinal atrophy were the factors significantly associated with PPCT. CONCLUSIONS Highly myopic eyes have significantly thinner peripapillary choroid and showed different distribution of thickness, compared with emmetropes. Axial length, IOP, and presence of posterior staphyloma and chorioretinal atrophy significantly influence PPCT and should be taken into consideration during clinical interpretation of PPCT measurement.

Correlation of structural and electrophysiological changes in the retina of young high myopes

Despite a high prevalence of myopia among young East Asian adults, there is a lack of data on the myopic retina structure‐function relationship in this group. We examined the association between optical coherence tomography (OCT) and electroretinogram (ERG) measurements in highly myopic young Asian adults to provide this information and also determined if OCT can be used as an alternative screening tool to assess retinal function in young myopic adults.

Maculopathy associated with dengue fever in a military pilot

Dengue fever is the most prevalent vector-borne flavivirus infection in humans. Its ocular manifestations have only recently been reported with increasing frequency. We present a case of an air force rotary wing pilot who presented with dengue-related maculopathy and decrement in visual function. The pilot ultimately recovered full visual function and was returned to full unrestricted flying duties with the proviso of regular ophthalmic monitoring. Dengue-related maculopathy may present with retinal edema, blot hemorrhages, and vasculitis. Less common features include exudative retinal detachment, cotton wool spots, and anterior uveitis. It is generally self-resolving with good prognosis. Treatment is controversial, but a course of corticosteroids has been tried in view of a postulated underlying immune-mediated pathology. It is recommended that aviators who have recovered from dengue fever undergo a clinical ophthalmological examination before return to flying duties.

Photorefractive keratectomy in young Asian aviators with low-moderate myopia.

INTRODUCTION The high prevalence of myopia among Asians led the Republic of Singapore Air Force (RSAF) to introduce photorefractive keratectomy (PRK) as a means of enlarging its pilot recruitment pool at the end of 2005. This study aims to address the efficacy and safety of PRK performed on young Asian patients with low-moderate myopia, as well as audit the RSAFs corneal refractive surgery (CRS) program. METHODS This is a retrospective case series of 149 eyes of 76 consecutive patients that underwent PRK as part of the RSAF CRS program over the 5-yr period from 1 January 2006 to 31 December 2010. RESULTS The median patient age was 21 yr (range, 18-26 yr) and the mean preoperative spherical equivalent (SE) refraction was -3.39 - 1.19 D. Of the patients, 96.1% were men and all were of Asian origin. At the 12-mo follow-up, 98.5% of eyes had an uncorrected distance visual acuity (UDVA) of < or = 0.00 LogMAR, 100.0% of eyes had an SE refraction of within + 0.50 D of intended correction, and 2.300% of eyes had a loss of corrected distance visual acuity (CDVA) of 0.20 LogMAR. The cumulative incidence of retreatments was 6.7% and cumulative incidence of grade II or worse corneal haze requiring retreatment was 6.0%. Refractive stability was achieved at 3 mo postsurgery. CONCLUSION The results of this study suggest that PRK performed within the context of a stringent and structured CRS program on young Asian eyes with low-moderate myopia is both efficacious and safe, with refractive stability achieved by 3 mo.

Peripheral retinal changes in highly myopic young Asian eyes

To determine the type and prevalence of peripheral retinal changes and its relationship with axial length (AL) in a population of young Asian adult males.

Positional and rotational stability of the toric phakic intraocular lens under high +Gz environments.

BACKGROUND Phakic intraocular lens (PIOL) implantation is a surgical option for correction of refractive errors. PIOLs can be use to correct myopia, hyperopia, and astigmatism. It is a surgical option available to patients in addition to methods such as laser cornea refractive surgery, e.g., laser assisted in-situ keratomileusis (LASIK) and photo-refractive keratectomy (PRK). Visian implantable collamer lens (ICL) are posterior chamber lenses which are surgically positioned in a phakic eye in the sulcus between the iris diaphragm and the natural crystalline lens. CASE REPORT This case report describes the stability of Visian toric ICL in a candidate with bilateral implants under high +Gz force exposure in a human centrifuge trainer. The subject was sequentially exposed to three incremental +Gz profiles of +5 Gz, +7 Gz, and +9 Gz. Pre- and post-+Gz exposure, ophthalmic examination revealed no ICL displacement, implant touch or induced cataract, or change in refractive error. DISCUSSION The rotational stability of the toric implants was also demonstrated by identical subjective refractions in both eyes taken pre- and post-+Gz, exposure. A search of the literature did not reveal any published articles on intraocular stability of ICL in the +Gz environment. This case report suggests that ICL may be considered an alternative to laser refractive surgery for patients subjected to a high +G, environment such as military aviators.

Is Myopia Affected By Near Work, Outdoor Activities And/Or Level Of Education?

Introduction Near work has always been associated with the influence of myopia (Ip JM, et al., 2008, Saw SM, et al., 2001 & 2002, Goss DA, et al., 2000). It has been shown to affect the progression of myopia. In this study, we aimed to determine if there is a relationship between outdoor activities and myopia, as the prevalence of myopia seems to be lower in children who are more active outdoor. (Rose KA, et al., 2008, Dirani M, et al., 2009, Jones LA, et al., 2007). In addition, we also aimed to establish if the level of education affects myopia prevalence.