Prevalence and Risk Factors for Undercorrected Refractive Errors among South Korean: KNHANES 2008-2012

PURPOSE: To assess the prevalence and risk factors of undercorrected refractive error in South Korea. METHODS: We analyzed 36,162 participants for estimating prevalence using the Korean National Health and Nutrition Examination Survey (KNHANES, 2008-2012). Undercorrected refractive error was defined as an improvement of at least 2 lines in best corrected visual acuity compared with the presenting visual acuity in the right eye. Proportion of undercorrected refractive error by occupation was presented, and associated sociodemographic factors were evaluated by multivariable logistic regression. RESULTS: The prevalence of undercorrected refractive error among all participants and among adults was 8.5% (n/N, 6,954/36,162) and 18.8% (n/N, 3,980/19,884), respectively. The proportion of undercorrected refractive error was higher among those with did not wear spectacles or contact lenses (23.1%) than among spectacle or contact lens wearers (8.1%). The proportion of participants who gained more than four or more lines of best corrected visual acuity was 7.2% (n = 2,606) for the all age group. In terms of occupation, farming, fishing, and forestry occupations (22.8%, 570/2,499) and laborer (20.2%, 497/2,457) were more likely to have undercorrected refractive error. Age groups of 10s, 70s, or 80s (30s as a reference group), female sex, lower income, lower education level, and living without a spouse were associated with undercorrected refractive error. CONCLUSIONS: People of older age, female sex, and lower socioeconomic status were more likely to have undercorrected refractive error. This suggests that a public-health approach is needed for preventing visual impairment via proper vision correction.

The Efficacy of Unilateral Rectus Resection in the Reoperation of Strabismus

PURPOSE: To study the efficacy of unilateral rectus resection in the surgical treatment of undercorrected or recurrent strabismus. METHODS: A retrospective chart review of patients who had undergone a unilateral rectus resection with at least 6 months (mean 35.6 months) of postoperative follow-up was performed. RESULTS: A resection of a single rectus muscle was undergone by 92 patients: 70 underwent a unilateral resection of the medial rectus and 22 underwent a unilateral resection of the lateral rectus. The mean preoperative deviations of patients were 23.6+/-5.9 prism diopters (PD). The amount of unilateral medial rectus resection ranged from 3 to 7 mm and unilateral lateral rectus resection ranged from 5 to 10 mm. The satisfactory surgical result was considered to be any deviation within 8 PD. The success rates were 81.4% in the unilateral medial rectus resection group and 72.7% in the unilateral lateral rectus resection group. The satisfactory surgical result of the group of preoperative deviation less than or equal to 20 PD was 93.2%, the group of greater than 20 PD and less than or equal to 25 PD was 65.6% and the group of greater than 25 PD was 68.8%. This difference in results between three groups was statistically significant (p=0.006). CONCLUSIONS: The unilateral rectus resection is an effective procedure for the treatment of undercorrected or recurrent strabismus with small to moderate preoperative deviations.

Clinical Result of Radial Keratotomy for the Undercorrected Myopia after Keratomileusis-in-situ

The authors report clinical results of 6 myopic patients(6 eyes) who showed undercorrection following keratomileusis-in-situ and then underwent radial keratotomy to correct the residual myopia. The mean age of patients was 39.2 years, and the mean interval between keratomileusis and radial keratotomy was 19.8 months. The mean refractive error was changed from -7.0D preoperatively to -3.23D after radial keratotomy. 'The average difference of refractive error between treated eye and untreated fellow eye was changed from 5.12D to 1. 63D after radial keratotomy. The mean visual acuity was changed from 0.15 preoperatively to 0.33 after radial keratotomy. In conclusion, radial keratotomy is an useful procedure for correcting undercorrected myopia after keratomileusis in situ.

Reoperations for Undercorrected Esotropia

For undercorrected esotropia after bilateral medial rectus(MR) recession, we performed unilateral or bilateral MR rerecession, unilateral rerecession or marginal myotomy of the recessed medial rectus muscle combined with lateral rectus(LR) resection, or unilateral LR resection. The correction of deviation was 15 delta in unilateral 2.0mm MR rerecession. Bilateral 2.0mm MR rerecession corrected 20 to 25 delta of esodeviation, but undercorrection was noted in one case. With unilateral 2.0mm rerecession or marginal myotomy of the recessed medial rectus muscle combined with 5.5mm or 8.0mm LR resection, the correction of deviation was 26 to 29 delta, and there was no under- or overcorrection. The corrective effect of this procedure was therefore greater and more stable than that of bilateral 2.0mm MR rerecession. Unilateral 8.0mm LR resection performed 3 months after bilateral MR recession showed correction of 15 delta, whereas the same procedure performed 3 weeks after bilateral MR rerecession showed correction of 24 delta. Unilateral LR resection procedure seems to be more efficacious for residual esotropia if performed as soos as possible within 3 months after sufficient bilateral MR recession or rerecession.