Sek-Jin Chew

Intraoperative mitomycin C to prevent recurrence of pterygium after excision: A 30-month follow-up study

OBJECTIVE The purpose of the study was to examine the efficacy of intraoperative mitomycin C (MMC) in preventing recurrence of pterygium after excision and the postoperative complications encountered. DESIGN The study design was a prospective, randomized, clinical trial. PARTICIPANTS A total of 180 primary and recurrent pterygia were recruited for the study. They were randomized into five groups: A, control with no MMC; B, 0.02% MMC for 5 minutes; C, 0.04% MMC for 5 minutes; D, 0.02% MMC for 3 minutes; and E, 0.04% MMC for 3 minutes. INTERVENTION All patients received pterygium excision with or without the above four modes of intraoperative MMC application. MAIN OUTCOME MEASURES Recurrence of pterygium and postoperative complications such as superficial scleral melting were measured. RESULTS At a mean follow-up of 30 (groups A-C) and 20 months (groups D and E), the respective recurrence rates in groups A through E were 75%, 8.3%, 8.6%, 42.9%, and 22.9%. There were two cases of postoperative superficial scleral melting in group C. Otherwise, no major postoperative complications were encountered. CONCLUSIONS The midterm results of a single intraoperative application of MMC at the concentration of 0.02% for 5 minutes are encouraging. Its application as an adjunctive therapy for the surgical treatment of pterygium appeared to be safe and effective. However, because of the possibility of serious late complications, the authors suggest that this procedure be reserved for patients who have high probability of recurrence after excision of pterygium.

Temporal variations in myopia progression in Singaporean children within an academic year.

Purpose Excessive nearwork is believed to be associated with myopia development and progression. To investigate this further, we studied refractive error changes and their correlation with nearwork in a cohort of grade school children in Singapore. Methods Cycloplegic autorefraction was performed 5 times over 10 months on 168 children aged 7, 9, and 12 years who were further divided into myopic and nonmyopic subgroups based in their initial refractive errors. Information about nearwork was obtained through diaries filled out over 24 h at the commencement of the study. Results Myopia progression was high (overall mean: −0.87 D per year) and largely linear throughout the year, but significantly higher rates were seen after the final school examinations in 7-year-old myopes and nonmyopes. Overall, myopic groups exhibited higher progression rates than nonmyopic groups, although 33.6% of subjects from the latter groups had become myopic by the end of the study. Nearwork scores derived from the diaries were generally not well correlated with overall myopia progression. Conclusions The tendency for myopia progression rates to increase after the final school examinations in 7-year-olds is interpreted as a delayed effect of the intense nearwork associated with preparing for them. The timing of nearwork-diary data collection at the beginning of the study could be responsible for the poor correlation between these data and overall myopia progression rates.

Prevention of Blinking Alters Iris Configuration in Pigment Dispersion Syndrome and in Normal Eyes

PURPOSE To examine the effect of blinking on iris configuration and aqueous humor distribution between the posterior and anterior chambers in eyes with pigment dispersion syndrome compared with healthy eyes. METHODS High-resolution, anterior segment ultrasound biomicroscopy was performed on ten eyes of ten patients with untreated pigment dispersion syndrome and on ten control subjects. Patients were scanned continuously for 15 minutes or until the maximal change in iris configuration occurred. During this time, the eyelids were held open mechanically, and blinking was prevented. Eyes then were rescanned immediately after blinking. RESULTS Initial iris configuration was concave in all eyes with pigment dispersion syndrome, whereas in control eyes it was concave in four eyes, planar in four eyes, and convex in two eyes. Iridozonular contact occurred in eyes with pigment dispersion syndrome only. Iridolenticular contact was greater in eyes with pigment dispersion syndrome than in control eyes. Analysis of covariance controlling for age, sex, and refractive error showed pigment dispersion syndrome to be a significant predictor of increased iris concavity. During continuous scanning, the mean change in iris position, from most concave to most convex, and mean time to the maximal change in iris configuration were greater for eyes with pigment dispersion syndrome than in control eyes and were related to the degree of initial iris concavity only (analysis of covariance). In six eyes with pigment dispersion syndrome, the eye cup was removed, normal blinking was permitted, and the eye was rescanned. The iris resumed a concave configuration in all eyes. CONCLUSION Increased iris concavity in pigment dispersion syndrome appears to be related to increased iridolenticular contact. This creates an anatomic configuration that predisposes to reverse pupillary block. The accumulation of aqueous humor in the posterior chamber, when blinking is prevented, alters iris position in pigment dispersion syndrome and in healthy eyes and increases iridozonular and iridociliary-process distances while minimizing iridolenticular contact. Normal blinking appears to create transient vector forces which promote aqueous humor flow from the posterior to anterior chamber.

Ocular-hypertensive Response to Topical Steroids in Children

OBJECTIVE The purpose of the study is to investigate the rate and degree of ocular-hypertensive response to topical steroids in Chinese children. DESIGN The study design was an institutional, randomized, clinical trial. PARTICIPANTS A total of 19 consecutive patients were studied. INTERVENTION Topical steroids were administered to Chinese children younger than 10 years of age who underwent bilateral strabismus surgery. One eye was randomized to receive topical 0.1% dexamethasone (DMS), whereas the fellow eye received 0.1% fluorometholone (FML) six times per day for up to 4 weeks. Intraocular pressure (IOP) was measured on the day before operation and at postoperative days 1, 3, 6, 10, 13, and 27, then every 2 weeks thereafter until the IOP fell to preoperative levels. Topical steroids would be stopped if IOP was 30.00 mmHg or greater. MAIN OUTCOME MEASURES Peak IOP and maximal change of IOP from baseline were measured and categorized into low, intermediate, and high levels. Time to peak IOP also was studied. RESULTS A total of 16 patients were included. The peak IOP for DMS-treated eyes was 30.66 +/- 8.35 mmHg (range, 13.00-48.00 mmHg), whereas that in FML-treated eyes was significantly lower at 20.66 +/- 6.03 mmHg (range, 11.30-36.30 mmHg) (P = 0.001). The maximal change in IOP ranged from -2.60 to +31.00 mmHg in DMS-treated eyes (mean, 15.48 +/- 8.71 mmHg), almost double that of FML-treated eyes (range, +1.00 to +17.00 mmHg; mean, 5.83 +/- 4.96 mmHg) (P = 0.001). When the ocular-hypertensive responses of both DMS and FML groups were categorized into three levels of severity, significant differences were found between the two treatment groups (P = 0.001). In the DMS group, nine patients (56.25%) were high responders and six patients (37.5%) were intermediate responders. In the FML group, only one patient (6.25%) was a high responder. CONCLUSIONS The ocular-hypertensive response to topical DMS in children occurs more frequently, more severely, and more rapidly than that reported in adults. A total of 56% of the studied children, all younger than 10 years of age, were high responders to topical DMS. Of these, 89% attained their peak IOP within 8 days. Its use in children should best be avoided if possible. It would be desirable to monitor the IOP when it is being used. Conversely, FML produced a much less ocular-hypertensive effect and therefore poses an acceptable risk of clinically significant pressure elevation.

Astigmatism in Chinese preschool children: prevalence, change, and effect on refractive development

Aim: To study the prevalence, type, and progression of astigmatism in Chinese preschool children, and its effect on refractive development. Methods: A cross sectional study of preschool children was carried out in two randomly selected kindergartens. A cohort study was performed on a subset of children, five years after initial examination. Refractive error (measured by cycloplegic autorefraction) and axial ocular dimensions (measured by ultrasonography) were the main study outcomes. Results: 522 children participated in the study; the mean age was 55.7 months (SD 10.9; range 27 to 77). Mean cylinder reading was −0.65 D (SD 0.58; range 0.00 to −4.75), and with the rule astigmatism was predominant (53%). In the 108 children studied longitudinally, the mean cylinder reading reduced from −0.62 D to −0.50 D (p = 0.019). The presence of astigmatism in initial examination predisposed the eyes towards greater myopisation (p<0.001). In addition, children with increased astigmatism had greater myopic progression (p<0.001) and axial length growth (p = 0.002). Conclusions: This study reports a high prevalence of astigmatism in Chinese preschool children. The presence of astigmatism, and particularly with increasing astigmatism, appears to predispose the children to progressive myopia. Further studies are warranted.

Automated static perimetry : the influence of myopia and its method of correction

OBJECTIVE To determine how the magnitude of myopia and its method of correction influence visual field testing. DESIGN Prospective observational case series, including comparison of spectacles and contact lenses. PARTICIPANTS One hundred forty-six ophthalmologically normal males 19 to 24 years of age with myopia (spherical equivalent from -0.50 to -14.0 diopters). METHODS Participants performed automated static threshold perimetry. Refractive errors were corrected using trial lenses and soft contact lenses. Subjects were tested with both methods of correction, the order of which was randomized. MAIN OUTCOME MEASURES Threshold sensitivity and global indexes. RESULTS Only one subject (0.7%) had a significant reproducible visual field defect on both methods of correction. Six subjects (4.1%) had a focal visual field defect on one method of correction but not the other. For myopia greater than -4.0 diopters, the mean defect decreased significantly as axial length and degree of myopia increased (P: < 0.01). Similar results were obtained with either method of correction. CONCLUSIONS Threshold sensitivity is reduced in moderate and high myopia, regardless of the method of correction. The surprisingly low prevalence of visual field defects in this myopic population disputes the widely held view that myopia is associated commonly with visual field abnormalities. If field defects are found in myopes on automated perimetry, it is advisable to repeat the test with another method of optical correction to check that such defects are genuine and not related to the method of refractive correction.

School Myopia in Hong Kong

The short article is about school myopia in Hong Kong and the high prevalence rates of myopia in primary school children.