Intraocular pressure associations with refractive error and axial length in children

AIM: To assess whether intraocular pressure (IOP) is associated with refractive error or axial length in children. METHODS: Of subjects from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), 636 Chinese children aged 9-11 years from two elementary schools underwent non-contact tonometry, cycloplegic autorefraction, and A-scan biometry during 2001. For analyses, refractive error was categorised into four groups; hypermetropia (spherical equivalent refraction (SE) > or = +1.0D), emmetropia (-0.5D相似文献   

Intraocular pressure, anterior chamber depth and axial length following intravenous mannitol.

The intraocular pressure (IOP), anterior chamber depth (ACD), and axial length (AL) were measured in 38 eyes of 19 subjects before and after intravenous mannitol injection (12.5 g). Intraocular pressures dropped over the initial 30 min then rose back to baseline by 2 hr. Time 0 min:14.2 mmHg, 15 min:12.7 mmHg, 30 min:11.4 mmHg, 60 min:12.0 mmHg, 90 min, 13.2 mmHg, 120 min:14.1 mmHg. Sitting and supine ACD and AL did not change following mannitol injection. This study supports an ocular hypotensive effect of mannitol without reducing vitreous volume using a relatively low dose of mannitol (12.5 g). This finding has important implications for its use in ocular surgery at this dosage.     

Intraocular lenses in children: changes in axial length, corneal curvature, and refraction

AIM: To assess changes in axial length, corneal curvature, and refraction in paediatric pseudophakia. METHODS: 35 eyes of 24 patients with congenital or developmental lens opacities underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation. Serial measurements were made of axial length, corneal curvature, objective refraction, and visual acuity. RESULTS: For patients with congenital cataracts (onset < 1 year age) the mean age at surgery was 24 weeks. Over the mean follow up period of 2.7 years, the mean increase in axial length of 3.41 mm was not significantly different from the value of an expected mean growth of 3.44 mm (paired t test, p = 0.97) after correction for gestational age. In the developmental cataract group (onset > 1 year of age) the mean age at surgery was 6.4 years with a mean follow up of 2.86 years. This group showed a mean growth in axial length of 0.36 mm that was not significantly different from an expected value of 0.47 mm (paired t test, p = 0.63). The mean preoperative keratometry was 47.78 D in the congenital group and 44.35 D in the developmental group. At final follow up the mean keratometry in the congenital group was 46.15 D and in the developmental group it was 43.63 D. In eyes followed for at least 2 years, there was an observed myopic shift by 24 months postoperatively of 3.26 D in the congenital cases (n = 10) and 0.96 D in the developmental cases (n = 18). CONCLUSION: The pattern of axial elongation and corneal flattening was similar in the congenital and developmental groups to that observed in normal eyes. No significant retardation or acceleration of axial growth was found in the eyes implanted with IOLs compared with normal eyes. A myopic shift was seen particularly in eyes operated on at 4-8 weeks of age and it is recommended that these eyes are made 6 D hypermetropic initially with the residual refractive error being corrected with spectacles.     

Intraocular lens power calculation in eyes with short axial length

Aim:

To evaluate and compare the predictive capacity of four intraocular lens (IOL) power calculation formulas (SRK/T, Hoffer Q, Holladay 1, and Haigis) in eyes shorter than 22.0 mm.

Setting and Design:

Observational study.

Materials and Methods:

Participants in our study were 69 consecutive patients with a preoperative axial length (AL) of less than 22.0 mm in one or both eyes. All patients underwent phacoemulsification with IOL implantation and postoperative target of refraction was analyzed. Specifically, the differences in the mean absolute estimation error (AE) for the four formulas were analyzed. Furthermore, the percentage of eyes with AE within ±0.5 and ±1.0 D for each formula was estimated, as well as the correlation coefficient (r) between the AL and estimation error (E) for each formula. The Mann-Whitney U test was used to compare differences in the AEs of the formulas. A statistically significant difference was defined as P < 0.05.

Results:

The Haigis formula had statistically significant smaller mean AE in comparison to Holladay 1, Hoffer Q, and SRK/T. The Haigis formula predicted more eyes with E within ±0.5 and ±1.0 D of predicted spherical equivalent compared to other formulas. Correlation between AL and AE revealed a negative r value and P < 0.05 for all formulas.

Conclusions:

Haigis formula provides more accurate results concerning the postoperative target of refraction in eyes with AL less than 22.0 mm. Hoffer Q could be also used as an alternative.     

Intraocular pressure in anisometropic children.

BACKGROUND: There is evidence that intraocular pressure (IOP) is higher in myopes than in hyperopes or emmetropes, and it has been suggested that myopia may be the result of a high IOP. We studied IOP in the two eyes of anisometropes, thus controlling for nuisance variables affecting IOP measurement. METHODS: Sixty-seven Chinese children, aged between 8 and 14 years, with anisometropia not <2 D were studied. A Topcon CT-60 noncontact tonometer was used for IOP measurement. Cycloplegia was achieved using two drops of tropicamide 1%, and retinoscopy was performed after residual accommodation had decreased to <2 D. A-scan ultrasonography was carried out using a Storz Alpha II Biometric Ruler. RESULTS: There were no statistically significant differences in IOP between the less myopic and more myopic eyes. CONCLUSIONS: Refractive error and axial length differences in anisometropic children are not related to differences in IOP and seem more likely to be due to genetically determined discrepancies in scleral structure, as previously proposed.     

青少年近视配戴角膜塑形镜后非接触眼压的变化

目的 观察和分析配戴角膜塑形镜后非接触眼压(NCT)的变化.方法 回顾性病例对照研究.对配戴角膜塑形镜的303例青少年近视患者,按照屈光度分为低、中、高度近视组.分别在戴镜前、戴镜后1d、1周、1个月及3个月时测量NCT、角膜曲率以及进行主、客观验光.对相关数据进行连续测量的单因素方差分析,两两比较采用LSD检验.结果 配戴角膜塑形镜1周后NCT趋于稳定,并且较戴镜前降低(F=51.75,P＜0.01),但在戴镜后1d,中高度近视眼压分别较戴镜前升高1.04 mmHg(t=-4.81,P＜0.01)及0.58 mmHg(t=-2.65,P＜0.05),低度近视眼压则呈下降趋势(t=0.57,P＞0.05).戴镜后3个月,屈光度改变量与眼压改变量呈正相关(r=-0.131,P＜0.05),不同程度近视每单位屈光度所致眼压改变不同(F=3.57,P＜0.05).其中,低度近视每单位屈光度改变导致眼压下降0.50 mmHg,高于中度近视(t=-2.57,P＜0.01),而低度与高度近视(t=-1.86,P＞0.05)、中度与高度近视(t=0.68,P＞0.05)之间则无明显差异.结论 配戴角膜塑形镜后NCT下降,眼压值的下降应该与角膜形态因素以及眼调节功能等因素有关.     

Intraocular pressure response to corticosteroids in children.

A total of 44 children who suffered from vernal conjunctivitis were treated with topical dexamethasone 0.1% 4 times daily for 6 weeks and tested for their intraocular pressure. There was a statistically significant difference (P less than 0.01) between the responders in our group of children and a group of normal adults reported on by Armaly in 1965.     

Relationship of axial length and retinal vascular caliber in children

PURPOSE: Previous studies in older adults suggest that longer axial length is associated with narrower arteriolar caliber. In this study, we re-examined this relationship in a cohort of children, while controlling for the effects of ocular magnification. DESIGN: Cross-sectional study of 767 children aged 7 to 9 years. METHODS: Retinal vascular calibers were measured from retinal photographs using a computer-based program. Ocular magnification was corrected using the Bengtsson formula. Standardized examination of refraction and ultrasound ocular biometry was performed for all children. RESULTS: In models that adjusted for age, gender, ethnicity, body mass index, blood pressure, and birth weight, longer axial length was associated strongly with narrower retinal arteriolar caliber (3.18-microm decrease per standard deviation increase in axial length; P < .001) and venular caliber (4.62-microm decrease standard deviation increase in axial length; P < .001) before correction for ocular magnification. However, after correction, these associations no longer were significant (0.44 microm; P = .31, change for arteriolar caliber; and 0.70 microm; P = .25, for venular caliber). CONCLUSIONS: Our study in children found no association between axial length and retinal vascular caliber after correcting for ocular magnification, suggesting that the previously reported association was likely related to differences in ocular magnification.     

Intraocular lens power calculation using the IOLMaster and various formulas in eyes with long axial length

PURPOSE: To evaluate the predictability of intraocular lens (IOL) power calculations using the IOLMaster (Carl Zeiss) and different IOL power calculation formulas in eyes with a long axial length (AL). SETTING: Department of Ophthalmology, Far Eastern Memorial Hospital, Taipei, Taiwan. METHODS: This study included 68 eyes with an AL longer than 25.0 mm that had phacoemulsification with IOL implantation. Preoperative AL and keratometric index measurements were obtained with the IOLMaster (Group 1) or, respectively, with applanation ultrasound and automatic keratometry (Group 2). The power of the implanted IOL was used to calculate the predicted postoperative spherical equivalence (SE) by various formulas: SRK/T, SRK II, and Holladay 1 (Groups 1 and 2) and Haigis (Group 1). The predictive accuracy of the formula was analyzed by comparing the mean difference between the actual and predicted postoperative SE; that is, the mean absolute error (MAE). RESULTS: The mean AL was significantly longer in Group 1 than in Group 2 (P = .03). The MAEs calculated by the SRK/T, SRK II, and Holladay 1 formulas were comparable between the 2 groups (P>.05). The lowest MAE was obtained using the IOLMaster data in the Haigis formula (P<.05). CONCLUSIONS: Although AL measured by the IOLMaster was longer than that measured by ultrasound, use of optical or ultrasound biometry data in the SRK/T, SRK II, and Holladay 1 formulas resulted in similar accuracy of IOL power prediction in eyes with higher myopia. The IOL power calculated using the Haigis formula predicted the best refractive outcome in long eyes.     

The relation of axial length and intraocular pressure fluctuations in human eyes

PURPOSE: To determine in human eyes whether diurnal fluctuations in axial length are related to fluctuations in intraocular pressure (IOP) by studying these fluctuations in both eyes of individual subjects and by assessing the regularity of both rhythms on two separate study days. METHODS: Ten subjects, ages 18 to 24 years, underwent serial axial length and IOP measurements using highly precise, noncontact partial coherence interferometry and Goldmann applanation tonometry, respectively. Both eyes were measured at six 3-hour intervals during each of two study days, and significant fluctuations were modeled by sine curves. RESULTS: Of the 40 data sets, 29 had significant axial length high-low differences and 32 had significant IOP high-low differences (ANOVA, P < 0.05 for each). The magnitude of the significant high-low differences were 38 +/- 22 microm for axial length and 6.0 +/- 1.9 mm Hg for IOP (mean +/- SD). Neither axial length nor IOP fluctuations necessarily occurred bilaterally on the same day, and neither rhythm was regularly observed on two separate days in individual eyes. In eyes in which both parameters fluctuated on the same day, there were no correlations in the amplitude, period or phase of the two rhythms. CONCLUSIONS: Both axial length and IOP fluctuate during the day much of the time in most subjects. However, diurnal IOP fluctuations do not appear to cause diurnal axial length fluctuations.     

Variability of the eyeballs axial length in children with pseudophakia

PURPOSE: The aim of the study is to evaluate the dynamics of axial elongation of pseudophakic eyes and changes in refraction pseudophakic eyes in children after monocular or binocular cataract surgery. MATERIAL AND METHODS: the observations of 79 children (158 eyes) aged from 4 to 18 years (mean 9.7 +/- 0.55) after cataract surgery were conducted. The examined group consisted of 105 pseudophakic eyes, the comparative group consisted of 53 eyes without surgery in the same observed group of children. Moreover, the patients were evaluated in the following group: moncular - binocular cataract, primary or secondary IOL implantation, the age in groups were between 4-7 and between 8-18 years. Analysis statistically: STATGRAPHICS and SIMSTAT programs, p (alpha) = 0.05. RESULTS: In the examined group (105 eyes) the mean follow-up time was 4.2 years (+/- 0.3), the average age of patients was 9.7 years (+/- 0.7). Improvement of visual acuity was achieved mean 0.5 in 52.4% post operative eyes observed, myopic shift was -0.7D (+/- 0.52). The anatomic eyeball length increased up to 0.5mm (+/- 0.27). The average age of patients of the control group was 9.7 years (+/- 0.83), follow-up 4.3 years (+/- 0.44), visual acuity 0.8 (+/- 0.03). Mean elongation of the axial length was 0.56 mm(+/- 0.26), mean refraction of the eyeball was +0.38 D (+/- 0.54). The difference of the changes of refraction between examined and control group was statistically significant. The comparison of final refraction in optical pathway (p = 0.32) and the growth of anatomic eyeball length (p = 0.14), proved no significant differences in the group with monocular and binocular IOL. The comparative analysis of final refraction in optical pathway (p1 = 0.36), and the growth of anatomic eyeball length (p2 = 0.26) in the group with primary or secondary IOL and in the younger or older children (p1 = 0.52; p = 0.98) in the both groups, did not significantly differ. CONCLUSIONS: The dynamics of axial elongation of pseudophakic and phakic eyes in children is similar. The myopic shift of pseufophakic eyes is bigger than in phakic eyes. It should be undertaken in calculation of the refractive power of intraocular lenses.