Prisms have been used as tools with which to treat and diagnose many diseases in strabismology. But, because of prismatic distortion and dispersion, the visual acuities are declined. The purpose of this study is to show the relationship between prismatic effect and visual acuity degradation. Visual acuities were measured through a series of prisms of CR-39 to quantify the blur induced by prism. The mean visual acuities of myopias and amblyopias(with or without correction), and emmetropias were reduced as prism diopters were increased. The declines were linear. There was no significant difference among the declines of visual acuities of each group. Whenever to prescribe prisms and to test with prisms, we should remind that prisms could reduce visual acuities.
Emmetropia ; Myopia ; Visual Acuity*

PURPOSE: To estimate the age and spherical equivalent related changes in the wavefront aberrations. METHODS: The age related difference in the wavefront aberrations were measured using a WASCA aberrometer on 63 eyes from 38 persons ranging in age from 18 to 60 years with a mean spherical equivalent of -0.55 diopter. The total RMS (root mean square), the high order RMS, coma and spherical aberration were analyzed and compared according to age(second, third, fourth, fifth and sixth decade). The spherical equivalent related difference in the wavefront aberrations were also measured on 118 eyes from 62 persons with a spherical equivalent ranging from +0.5 D to -10.5 D (average -4.87 D). The total RMS, high order RMS and spherical aberration were analyzed and compared according to the spherical equivalent. RESULTS: With increasing age, the total RMS showed no statistically significant increase (p>0.05), but a high order RMS and spherical aberration showed a significant increase (p<0.05) and there was increase in the incidence of coma but without statistical significance (p>0.05). With the increasing amount of spherical equivalent, the total RMS increased significantly (p<0.05), but the incidence of coma and the spherical aberration did not (p>0.05). CONCLUSIONS: In emmetropia, the total RMS and high order aberration increased significantly with increasing age. With increasing amount of spherical equivalent, the total RMS increased significantly while coma and the spherical aberrations did not.
Coma ; Emmetropia ; Humans ; Incidence

PURPOSE: We evaluated the distribution and change of total, corneal and residual astigmatism with age in patients with emmetropia. METHODS: We examined the visual acuity, refraction, and corneal curvature in 263 persons aged from 3 to 83 years (mean, 38 years), with a spherical equivalent refraction of under +/-0.75 diopter (D). We analysed the distribution and change of the astigmatism. RESULTS: Total astigmatism was changed from with-the-rule (WTR) to against-the-rule (ATR) with aging based on WTR of 0.31 +/- 0.48 D in the 3-10 year-old group, ATR of 0.02 +/-0.52 D in the 31-40 year-old group and ATR of 0.65 +/- 0.66 D in the 71-83 year-old group. Corneal astigmatism showed a similar pattern to that of total astigmatism with WTR of 1.03 +/- 0.47 D, WTR of 0.37 +/- 0.78 D, ATR of 0.05 +/- 0.59 D and ATR of 0.31 +/- 0.64 D in the 3-10, 31-40, 61-70 and 71-83 year-old groups, respectively. Residual astigmatism showed ATR astigmatism in all age groups such as ATR of 0.71 +/- 0.48 D, ATR of 0.60 +/- 0.44 D and ATR of 0.35 +/- 0.71 D in the 3-10, 41-50 and 71-83 year-old groups, respectively. CONCLUSIONS: Total and corneal astigmatism showed the change from WTR to ATR, and residual astigmatism showed the pattern of decreasing ATR with aging in patients with emmetropia. The change of total astigmatism with aging seems to be influenced by that of corneal astigmatism rather than by that of residual astigmatism.
Aging ; Astigmatism* ; Emmetropia* ; Humans ; Visual Acuity

The purpose of the study was to evaluate the postoperative change of keratometric astigmatisms according to preoperative. A total of 254 eyes were underwent phacoemulsification and foldable silicone posterior chamber lens implantation using 3.2mm temporal clear corneal incision. The subjects were divided into five groups: Group 1(aganist the rule >1.25D), Group 2(ATR < OR =1.0D), Group 3(with the rule < OR =1.0D), Group 4(WTR >1.25D) and emmetropia according to preoperative astigmatisms. Mean preoperative astigmatism was -0.19+/-0.97D. At 6 months after operation, mean surgically induced stigmatism(SIA) was 0.41+/-0.60, and remained astigmatism was 0.27+/-0.98D. SIA in group 1, 2 was less than in group 3, 4. The difference was stastically significant at 6 months after operation(p<0.05). The change of astigmatism in group 1 was -1.83+/-0.48D preoperatively, -0.75+/-0.50D at 6 months after operation, in group 2 -0.58+/-0.28D preoperatively, 0.02+/-0.50D at 6 months, in group 3 0.45+/-0.25D preoperatively, 0.50+/-0.43D at 6 months, and in group4 1.90+/-0.25D preoperatively, 3.17+/-0.23D at 6 months. In group 4, the proportion of patients who had astigmatism within 1D was only 20% at months after operation and none 6 months after operation. In conclusion, temporal clear corneal incision induces more astigmatisms in preoperative ATR group than in WTR group. And the Patients who have preoperative astigmatism larger than WTR 1.25D seem to be needed an additional correction of astigmatism or change the location of incision in temporal clear corneal incision cataract surgery.
Astigmatism* ; Cataract* ; Emmetropia ; Humans ; Phacoemulsification ; Silicones

Since corneal thickness is changed by various corneal disease, it is important to determine the normal value of the corneal thickness. Normal corneal thickness was measured by Sohn (1972) in our depatment. Also it was reported by Murata and Kato (1963), von Bahr(1948) that the corneal thickness is thinner in myopia than in emmetropia. Author measured central corneal thickness of 58 myopic eyes which divided into three groups according to the degree of myopia-group 1(-0.25D ~ 3.75D), group 2(-4.0D ~ 5.75D) and group 3(more than -6.0D)-using Haag-Streit pachometer and Mishima and Hedbys modified device to determine the changes of the corneal thickness of the myopic eyes. Results obtained as follows: 1. In group 1, group 2 and group 3, the mean value with standard deviation for the central part of the cornea was 0.497 +/- 0.012mm, 0.452 +/- 0.011mm and 0.430 +/- 0.012mm, respectively. 2. There was no significant difference of the central corneal thickness between group 1 and emmetropia. 3. However central corneal thickness of the group 2 and 3 were significantly thinner than that of group 1, respectively (P<0.001). 4. The central corneal thickness was significantly thinner in group 3 than that of group 2 (P<0.001). 5. The changes of central corneal thickness linealy decreased as the myopic degree increased from -4.0D to -7.0D.
Cornea ; Corneal Diseases ; Emmetropia ; Myopia ; Reference Values

370 eyes which underwent phtorefractive keratectorny With VISX 20/20 excuner laser were evaluated. At 6 months post-op, the low myopic group(under -6D) of 172 eyes with mean pre-op refractive error of -4.48D changed to -0.54D, the moderate myopic group(between -6D and -9D) of 128 eyes changed from -7.47D to -1.19, and the hlgh myopic group(above -9D) of 70 eyes changed from -11.29D to -2.68D, 76%, 61.9%, ahd 17.4% of the respective groups were with +/-1D of emmetropia. Uncorrected vision hetter than 20/40 was achiced in 90.7%, 75.2% and 31 9% of the resperective groups. The best corrected vision below 2 lines from the best pre-op level was seen in 1.2%, 2.3%, and 4.3% of the respective groups. The astigmatic correction rate was 6.6% in the eyes under 1D of astigmatism, 36.1% in the eyes between 1D and 2D, and 54.5% in the eyes more than 2D.
Astigmatism ; Emmetropia ; Lasers, Excimer* ; Myopia ; Refractive Errors

Objective: This study measured the optic-disc area using optical coherence tomography (OCT) and correlated it with the type of refractive error. Methods: A cross-sectional study was conducted involving 73 healthy Filipinos aged 20 to 60 years. All underwent a full ophthalmologic examination including visual acuity, automated refraction, Goldmann applanation tonometry, and dilatedfundus examination. Fast optic-nerve-head imaging was performed with 6 radial linear scans centered on the optic-nerve head. Data were tabulated and the association between optic-disc measurements and refractive error was analyzed using analysis of variance and linear regression. Results: A total of 142 eyes of 73 patients were included, of which 39 (27.5%) were classified as emmetropia or hyperopia, 47 (33%) as low myopia, 37 (26.2%) as moderate myopia, and 19 (13.4%) as high myopia. The mean refractive error was –9.2 ± 2.98D for those with high myopia, –4.7 ± 0.74D for moderate myopia, –1.7 ± 0.78D for low myopia, and 1.1 ± 2.55D for emmetropia and hyperopia. The mean optic-disc area for all groups was 2.70 ± 0.59 mm2 (range, 1.6 to 4.7 mm2 ); the mean optic-disc area was similar for high myopia (2.7 ± 0.57 mm2 ) and low myopia (2.7 ± 0.52 mm2 ). There was no significant difference in the optic-disc area of the different types of refractive errors (p = 0.30). Conclusion This study showed that the optic-disc area is statistically independent of the refractive error.
Emmetropia Hyperopia Myopia Tomography ; Optical Coherence

PURPOSE: To evaluate the changes in macular thickness with regard to age and gender in normal subjects with emmetropia using spectral domain optical coherence tomography. METHODS: The present study consisted of 90 healthy subjects (162 eyes) with no ophthalmic evidence of retinopathy and who had emmetropic eyes. The data from macular measurements using spectral domain optical coherence tomography was analyzed according to the groups divided by age (Group 1: 0 to 19 years of age, Group 2: 20 to 39 years of age, Group 3: 40 to 59 years of age, Group 4: 60 to 80 years of age) and gender. RESULTS: Macular thickness of the central circle was 253.40 +/- 23.03 microm in all subjects. There was no significant change with age (p > 0.05). However, the measurements at the inner (3 mm) and outer circle (6 mm) showed a reduction of macular thickness with age (p < 0.05). The macular thickness at the central and inner circle was significantly lower in the female subjects (p < 0.05). In group 3 and 4, macular thickness at the central circle in males was greater than in females. In group 3, the average inner macular thickness in males was significantly greater than in females (p < 0.05). CONCLUSIONS: In normal subjects with emmetropia, there are statistically significant differences in macular thickness between subjects of different age and gender. The results from the present study can be expected to provide a reference value for evaluating macular disease.
Emmetropia ; Eye ; Female ; Humans ; Male ; Reference Values ; Tomography, Optical Coherence

PURPOSE: To investigate the shape of normal fovea in Korean subjects in their 20's using spectral domain optical coherence tomography (SD-OCT). METHODS: One hundred-twelve emmetropic eyes of 60 subjects and 100 myopic eyes of 58 subjects between 20 and 29 years of age were included in this study. Central foveal thickness (CFT), regional maximal retinal thickness (MRT), pit diameter, pit depth, and slope were obtained using Spectralis OCT and analyzed according to spherical equivalent and gender. RESULTS: In emmetropic and myopic eyes, MRT was significantly thinner temporally (p < 0.001) than in other regions and pit diameter was wider horizontally than vertically (p < 0.001). The CFT was significantly thicker and all regional MRT was thinner in myopic eyes than in emmetropic eyes (p < 0.001). Foveal pits were narrower and shallower in myopic eyes (p < 0.001). In both groups, CFT and all regional MRT in males were significantly thicker than in females (p < 0.05); however, no difference between the genders in horizontal pit diameter, pit depth, and slope were found. CONCLUSIONS: In normal subjects, statistically significant differences were found in foveal shapes between subjects with different spherical equivalent and gender. These differences should be considered when interpreting a foveal shape. Knowledge of the normal foveal morphology is important when conducting further macular studies.
Emmetropia* ; Female ; Humans ; Male ; Myopia* ; Retinaldehyde ; Tomography, Optical Coherence*

We evaluated the effect of retreatment for under- of overcorrection after laser in situ keratomileusis(LASIK). We performed LASIK enhancement after lifting flap(8 eyes) and transepithelial PRK(1 eye) for the 9 eyes of undercorrection and 1 eye of hyperopic correction after primary LASIK procedures were performed from October 1996 through May 1997. The average preoperative refractive error was -12.88D and preretreatment refractive error was -3.53D in spherical equivalent. The average period from primary LASIK to retreatment was 85.7 days and we evaluated the stability, predictability, efficacy, safety, and complications after 6 months. At 6 months postretreatment, the average refractive error was -0.31D and 8 eyes obtained a refraction within +/-1.0D of emmetropia. Uncorrectedvisual acuity(UCVA) was improved from 0.24 to 0.71. There was one eye with grade III corneal haze and decentration after transepithelial PRK on corneal flap. And it had 1 line loss of best corrected visual acuity(BCVA) compared with preretreatment BCVA. The final average refractive error of the 7 eyes which underwent retreatment after 1 month was closer to emmetropia than that of the other 3 eyes which underwent retreatment within 1 month, but there was no statistically significant difference(p>0.05). In conclusion, LASIK tetreatment may be considered for the correction of under- and overcorrection after LASIK.
Emmetropia ; Keratomileusis, Laser In Situ* ; Lifting ; Refractive Errors ; Retreatment*