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PubMed2005

Off-axis refraction and aberrations following conventional laser in situ keratomileusis.

PURPOSE: To investigate off-axis refraction and aberrations following conventional laser in situ keratomileusis (LASIK) for myopia and hypermetropia. SETTING: School of Optometry, Queensland University of Technology, Australia. METHODS: Using an autorefractor, off-axis refractions were analyzed along the horizontal visual field between 35 degrees nasally and 35 degrees temporally in 1 eye each of 15 emmetropic subjects (-0.50 to +0.50 diopters [D]), 6 myopic subjects (-2.25 to -6.50 D), 6 hyperopic subjects (+1.50 to +3.00 D), 6 myopic LASIK patients (presurgical refraction -2.75 to -9.00 D), and 6 hyperopic LASIK patients (presurgical refraction +0.75 to +2.00 D). Wavefront sensing measured off-axis higher-order aberrations in 2 myopic LASIK patients. RESULTS: In myopic LASIK, the mean spherical components of refraction M became highly myopic away from the center of the visual field; in emmetropic and untreated myopic eyes, there were relatively small myopic shifts and hyperopic shifts, respectively. Off-axis 90-degree to 180-degree astigmatisms J180 in myopic LASIK subjects were greater than in untreated subjects. In hyperopic LASIK, there were mainly hyperopic shifts in M, opposite the direction in emmetropic and untreated hyperopic subjects. Off-axis J180 was less than in emmetropic and untreated hyperopic subjects. Some hyperopic LASIK patients had greater off-axis 45-degree to 135-degree astigmatisms J45 than patients in the other groups. In 2 myopic LASIK patients, Zernike root-mean-square 4th-order aberrations were higher than in the near-emmetropia group because of higher levels of positive spherical aberration. CONCLUSIONS: Off-axis aberrations can be dramatically affected by conventional myopic and hyperopic LASIK. In myopic LASIK, the increased off-axis refractive errors may have adverse effects on peripheral visual tasks that are dependent on off-axis refractive errors. The relatively low off-axis refractive errors in hyperopic LASIK patients may improve peripheral visual tasks.

Adult↗
PubMed1993

Initial cross-sectional results from the Orinda Longitudinal Study of Myopia.

BACKGROUND: Although investigations of human refractive error development and normal ocular growth have been conducted for the last 50 years, no previous study of refractive error and the ocular components has measured all the ocular components. METHODS: The Orinda Longitudinal Study of Myopia was initiated to characterize the development of refractive error and normal eye growth in a sample of predominantly Caucasian children ages 6 to 14 years. RESULTS: Cross-sectional results from 530 children ages 5 to 12 years in the 1st, 3rd, and 6th grades are presented. CONCLUSIONS: This sample's refractive error decreased toward emmetropia with age from an average of +0.73 D at age 6 years to an average of +0.50 D by age 12 years. Between the ages of 6 and 12 years, the vitreous chamber elongated (by 0.52 mm) and the crystalline lens power decreased (by 1.35 D); surprisingly, the crystalline lens thinned by 0.14 mm during this same time period.

California↗
PubMed1989

Meridional analysis of with-the-rule astigmatism in Oklahoma Indians.

Refraction and keratometry records were obtained for 142 consecutive with-the-rule astigmats and for 100 consecutive nonastigmats from W. W. Hastings Indian Health Service Hospital in Tahlequah, Oklahoma. Patients were 5 to 40 years of age. Patients with higher degrees of Indian ancestry were more common in the astigmatic group than in the spherical refraction group. An analysis of refractive error and keratometry by principal meridian was performed. The horizontal meridian refractive error in astigmats was most often near emmetropia. Compound myopic astigmatism and mixed astigmatism accounted for over 3/4 of the cases. The astigmats as a group had flatter corneas in the horizontal and steeper corneas in the vertical than the nonastigmats. Horizontal refractive errors and horizontal keratometry readings showed a weak but significant correlation in astigmats but not in nonastigmats.

Adolescent↗
PubMed1994

The effect of cycloplegia on measurement of the ocular components.

PURPOSE: The purpose of this study was to examine the effect of cycloplegic agent on the measurement of refractive error and the ocular components. METHODS: We compared two commonly used topical cycloplegic agents, 1% tropicamide and 1% cyclopentolate, for their effect on the measurement of refractive error (by Canon R-1 autorefraction), accommodative response (by Canon R-1 autorefraction and by the conventional, subjective "pushup" method), crystalline lens power (by video phakometry and by calculation), and axial ocular dimensions (by A-scan ultrasonography) in 20 emmetropic to moderately hyperopic children. RESULTS: Comparison of refractive error at each drug's reported time of maximum cycloplegia (30 minutes for tropicamide and 60 minutes for cyclopentolate) showed that distance autorefraction in the vertical meridian differed by +0.20 +/- 0.30 diopters (D) (P = 0.008). The average difference was +0.07 +/- 0.10 mm for anterior chamber depth (P = 0.004), -0.03 +/- 0.05 mm for crystalline lens thickness (P = 0.025), -0.65 +/- 0.69 D for phakometrically measured crystalline lens power (P < 0.001), +0.03 +/- 1.55 D for calculated crystalline lens power (P = 0.94), and -0.09 +/- 0.19 mm for vitreous chamber depth (P = 0.062, all paired t tests; positive signs denote greater values with cyclopentolate). Residual accommodation was 0.47 and 0.67 D greater with tropicamide when measured by autorefraction and the pushup method (P = 0.013 and 0.08 respectively, paired t test). All significant differences were consistently in the direction of poorer cycloplegia with tropicamide. CONCLUSIONS: Although tropicamide, as expected, showed poorer cycloplegia compared to cyclopentolate, the degree of difference appeared to be small, with minimal effect on the measurement of distance refractive error and the ocular optical components.

Accommodation, Ocular↗
PubMed1994

Results of the prospective evaluation of radial keratotomy (PERK) study 10 years after surgery.

OBJECTIVE: To determine the long-term effects and stability of refraction following a standardized technique of radial keratotomy for myopia in the nine-center Prospective Evaluation of Radial Keratotomy (PERK) Study 10 years after surgery. METHODS: Radial keratotomy using eight centripetal incisions was performed to reduce myopia of -2.00 to -8.75 diopters in 1982 and 1983. A mean of 10 years later, patients underwent a standardized ophthalmic examination similar to previous study examinations. RESULTS: Of 427 patients (793 eyes that underwent radial keratotomy), 374 patients (88%) (693 eyes) returned for the 10-year examination. Of 675 eyes with refractive data, 38% had a refractive error within 0.50 D and 60% within 1.00 D. For 310 first-operated eyes, the mean refractive error was -0.36 D at 6 months and changed in a hyperopic direction to + 0.51 D at 10 years. The average rate of change was +0.21 D/y between 6 months and 2 years and +0.06 D/y between 2 and 10 years. Between 6 months and 10 years, the refractive error of 43% of eyes changed in the hyperopic direction by 1.00 D or more. The hyperopic shift was statistically associated with the diameter of the clear zone. Uncorrected visual acuity was 20/20 or better in 53% of 681 eyes and 20/40 or better in 85%. Loss of spectacle-corrected visual acuity of 2 lines or more on a Snellen chart occurred in 3% of all 793 eyes that underwent surgery. Among 310 patients with bilateral radial keratotomy, 70% reported not wearing spectacles or contact lenses for distance vision at 10 years. CONCLUSION: The PERK technique of radial keratotomy eliminated distance optical correction in 70% of patients, with a reasonable level of safety. A shift of the refractive error in the hyperopic direction continued during the entire 10 years after surgery.

Adult↗
PubMed2000

Quantitative analysis of the effect of near lens addition on accommodation and myopigenesis.

PURPOSE: To develop a quantitative, objective, and scientific basis for understanding the effects of applying near bifocal additions (ADDs) on oculomotor control and myopia development. This is important because myopia is a major public health problem that affects 25% of the U.S. population and 75% or more in Asian countries. It is also associated with an increased risk for vision-threatening conditions, such as retinal breaks and detachments, as well as glaucoma. METHODS: A comprehensive model of refractive error development was constructed based on a dual-interactive feedback model of accommodation and vergence, which represented the short-term dynamics pathway, with the addition of both genetic and environmental (defocus-induced axial growth) components in a long-term pathway. An alternating near- and far-viewing paradigm was simulated, with varying amounts of ADDs, to obtain a parametric relationship between the root mean square of accommodative error (AE) and the induced refractive error (IRE). The parametric relationship provided the crucial linkage between the long-term growth pathway and the conventional short-term dynamics pathway. ADD is the simulated lens placed before the eyes only during near viewing, whereas IRE is the simulated lens fixed before the eyes that represents the optical effect of slowly progressive refractive development caused by near work. RESULTS: A V-shaped functional relationship was found between AE and IRE. The left half of the curve is associated with hyperopic defocus and myopigenesis, whereas the right half is associated with myopic defocus and hyperogenesis. Introduction of an ADD shifts the V-shaped curve horizontally. Thus, an "optimal" ADD can be used to shift the minimum of the accommodative error curve to the zero IRE point, and thereby reduce or eliminate retinal defocus and its potential towards myopigenesis. On the other hand, sensitivity analysis of model parameters shows that increasing the accommodative convergence crosslink gain (AC) shifts the curve to the right and results in a tendency towards myopigenesis, which is consistent with clinical findings in progressive myopia. CONCLUSIONS: The model can be used to specify the precise ADD needed for an individual to retard or eliminate retinal defocus-induced myopic progression. If future experiments show that using the "optimal" ADD results in the greatest benefit (i.e., least myopia progression), there will be considerable worldwide public health benefit.

Accommodation, Ocular↗
PubMed2002

Population-based study of spectacles use in southern India.

This study assessed the use of spectacles and its demographic associations in a sample representative of the population of the Indian state of Andhra Pradesh. A total of 11,786 subjects of all ages were sampled from 94 clusters in one urban and three rural study areas of Andhra Pradesh using stratified, random, cluster, systematic sampling. The eligible subjects underwent detailed interview and eye examination including dilated examination of the posterior segment. The data on the use of spectacles were analysed for subjects > 15 years of age. A total of 7,432 subjects > 15 years of age participated in the study of whom 1,030 (13.8%) had a refractive error of spherical equivalent +/- 3.00 Diopter or worse. The prevalence of current use of spectacles in those with spherical equivalent +/- 3.00 Diopter or worse, who were likely to be visually impaired without refractive correction, was 34.2% (95% confidence interval 30.3-38%) and of previous use of spectacles was 12.3% (95% confidence interval 10.3-14.3%). The odds of using spectacles currently were significantly higher for those with any level of education, those living in the urban area, and for those with aphakia or psuedophakia as compared with natural refractive error. Among those who had used spectacles previously, 43.8% had discontinued because they felt that either the prescription was incorrect or that the spectacles were uncomfortable, suggesting poor quality of refractive services, and another 19.6% had lost the pair and could not afford to buy another pair. These data suggest that the use of spectacles in this population by those with refractive error was not optimal. Two-thirds of those with spherical equivalent +/- 3.00 Diopter or worse were not using spectacles. Of those who had discontinued the use of spectacles, a significant proportion did so for reasons related to poor quality of refractive services. Strategies such as vision screening programmes and eye health promotion need to be implemented, the quality of refractive services monitored and the cost of spectacles regulated, if the substantial burden of visual impairment due to refractive error in this population is to be reduced.

Adolescent↗
PubMed2005

Choice of intraocular lens may not affect refractive stability following cataract surgery.

PURPOSE: To assess whether the choice of an intraocular lens (IOL) with rigid haptics (Sensar) or an IOL with pliable haptics (Acrysof) has an effect on refractive stability following cataract surgery. METHODS: Seventy-three patients were recruited consecutively as they returned for their 6-month visit following cataract surgery. There were 37 patients who had received an Acrysof IOL and 36 who had received a Sensar IOL. Each patient had their refractive error measured at the 1-month postoperative visit. At the 6-month follow-up visit, refraction was repeated. The change in refractive error was then compared between IOL groups and other factors that may affect postoperative refractive stability including preoperative refraction, axial length, keratometry, wound type and wound meridian. RESULTS: An Acrysof IOL showed minimal myopic movement, whereas a Sensar IOL was more likely to move hypermetropically. However, this difference was not statistically significant (t=1.92; P=0.06). The magnitude of the shift in spherical equivalent in either direction for the Acrysof group was 0.37 +/- 0.35 D and for the Sensar group was 0.28 +/- 0.31 D. Again, this difference was not statistically significant (t=1.17; P=0.25). However, preoperative anterior chamber depth was associated with postoperative refractive shift (t=2.66; P=0.009). Furthermore, patients with a scleral wound showed a small against-the-rule shift in cylindrical refractive error. No other factors were associated with postoperative refractive shift amongst the sample. CONCLUSIONS: There were no clinically significant differences in postoperative refractive stability between the Acrysof and Sensar groups. However, preoperative anterior chamber depth was associated with the magnitude of shift in spherical equivalent.

Acrylic Resins↗
PubMed1987

Observations on the effects of form deprivation on the refractive status of the monkey.

The consistency of the refractive error alterations produced by monocular form deprivation in developing monkeys and the influence of the duration and the age at the onset of deprivation on the magnitude of these alterations was investigated. Refractive error and axial length measurements are presented for a group of monkeys which had one eye sutured closed for a period exceeding 18 months beginning at various ages ranging from 26 days to 25 months. In addition, we pooled and reanalyzed refractive error and axial length data for monocularly form-deprived monkeys from previous studies. When the alterations in the deprived eye's refractive status are specified with respect to the fellow nondeprived eye, the results are, with a few noteworthy exceptions, consistent between laboratories and individual animals. In most cases, early monocular form deprivation causes the treated eye to develop a longer axial length and to manifest a more myopic/less hyperopic refractive error than the fellow nontreated eye. The magnitude of this deprivation-induced alteration is generally dependent on the duration and the age at the onset of form deprivation. The earlier the deprivation is initiated and the longer it is maintained, the greater the degree of the relative myopia produced in the deprived eye.

Animals↗
PubMed2005

Three-year follow-up of biomicroscopy signs and refractive status in patients wearing lotrafilcon A lenses.

PURPOSE: To report the wearer experience, biomicroscopy signs, and stability of refractive error after 3 years' use of lotrafilcon A lenses. METHODS: Seventy-four subjects from a multicenter clinical trial with lotrafilcon A lenses were queried on aspects of lens wear. Biomicroscopy signs and refractive error were compared to baseline measurements. RESULTS: A total of 66% of subjects reported continuing to wear lotrafilcon A lenses, usually for more than 21 nights, with high satisfaction. Signs of limbal, palpebral, and bulbar redness improved significantly. Average refractive error remained stable. CONCLUSIONS: Long-term use of lotrafilcon A lenses resulted in high wearer satisfaction, reduction of ocular redness, and stable refractive error.

Contact Lenses, Extended-Wear↗
PubMed2005

Peripheral vision can influence eye growth and refractive development in infant monkeys.

PURPOSE: Given the prominence of central vision in humans, it has been assumed that visual signals from the fovea dominate emmetropization. The purpose of this study was to examine the impact of peripheral vision on emmetropization. METHODS: Bilateral, peripheral form deprivation was produced in 12 infant monkeys by rearing them with diffusers that had either 4- or 8-mm apertures centered on the pupils of each eye, to allow 24 degrees or 37 degrees of unrestricted central vision, respectively. At the end of the lens-rearing period, an argon laser was used to ablate the fovea in one eye of each of seven monkeys. Subsequently, all the animals were allowed unrestricted vision. Refractive error and axial dimensions were measured along the pupillary axis by retinoscopy and A-scan ultrasonography, respectively. Control data were obtained from 21 normal monkeys and 3 infants reared with binocular plano lenses. RESULTS: Nine of the 12 treated monkeys had refractive errors that fell outside the 10th- and 90th-percentile limits for the age-matched control subjects, and the average refractive error for the treated animals was more variable and significantly less hyperopic/more myopic (+0.03 +/- 2.39 D vs. +2.39 +/- 0.92 D). The refractive changes were symmetric in the two eyes of a given animal and axial in nature. After lens removal, all the treated monkeys recovered from the induced refractive errors. No interocular differences in the recovery process were observed in the animals with monocular foveal lesions. CONCLUSIONS: On the one hand, the peripheral retina can contribute to emmetropizing responses and to ametropias produced by an abnormal visual experience. On the other hand, unrestricted central vision is not sufficient to ensure normal refractive development, and the fovea is not essential for emmetropizing responses.

Animals↗
PubMed2006

Genomewide scan in Ashkenazi Jewish families demonstrates evidence of linkage of ocular refraction to a QTL on chromosome 1p36.

UNLABELLED: The development of refractive error is mediated by both environmental and genetic factors. We performed regression-based quantitative trait locus (QTL) linkage analysis on Ashkenazi Jewish families to identify regions in the genome responsible for ocular refraction. We measured refractive error on individuals in 49 multi-generational American families of Ashkenazi Jewish descent. The average family size was 11.1 individuals and was composed of 2.7 generations. Recruitment criteria specified that each family contain at least two myopic members. The mean spherical equivalent refractive error in the sample was -3.46D (SD=3.29) and 87% of individuals were myopic. Microsatellite genotyping with 387 markers was performed on 411 individuals. We performed multipoint regression-based linkage analysis for ocular refraction and a log transformation of the trait using the statistical package Merlin-Regress. Empirical genomewide significance levels were estimated through gene-dropping simulations by generating random genotypes at each of the 387 markers in 200 replicates of our pedigrees. Maximum LOD scores of 9.5 for ocular refraction and 8.7 for log-transformed refraction (LTR) were observed at 49.1 cM on chromosome 1p36 between markers D1S552 and D1S1622. The empirical genomewide significance levels were P=0.065 for ocular refraction and P<0.005 for LTR, providing strong evidence for linkage of refraction to this locus. The inter-marker region containing the peak spans 11 Mb and contains approximately 189 genes. CONCLUSION: We found genomewide significant evidence for linkage of refractive error to a novel QTL on chromosome 1p36 in an Ashkenazi Jewish population.

Alleles↗
PubMed1991

The regulation of eye growth and refractive state: an experimental study of emmetropization.

During growth the vertebrate eye achieves a close match between the power of its optics and its axial length with the result that images are focused on the retina without accommodative effort (emmetropia). The possibility that vision is required for the regulation of eye growth was studied experimentally in chicks made myopic or hyperopic by different visual manipulations. After discontinuing these visual manipulations, the eyes returned quickly to emmetropia mainly by adjusting the growth of their vitreous chambers; growth stopped in eyes recovering from myopia and continued in eyes recovering from hyperopia. Because both hyperopic and myopic eyes were already larger than normal controls, the difference in growth indicates that refractive error, rather than eye size per se, guides the eye toward emmetropia. Evidence is also presented for nonvisual shape-related control of eye growth, but this is slow-acting and cannot explain the emmetropization from induced refractive errors. Both the visually guided and shape-related mechanisms work even in eyes with the optic nerve cut, indicating that the two mechanisms are local to the eye. Although the optic-nerve-sectioned eye can sense the sign of a refractive error and initially adjust growth accordingly, it eventually overshoots emmetropia and reverses the sign of the initial refractive error. Whether this is due to loss of feedback from the central nervous system or retinal ganglion cells is unclear.

Aging↗
PubMed1988

Instant photographic refractometry in children.

A simple photographic method for detection and measurement of refractive errors in children, using a specially designed camera and electronic flash unit and 'instant' (Polaroid) film, was tested on 64 children, aged 3 to 8 years, and compared with the results from retinoscopy. The refractive errors ranged from -6.5 to +6.5 D. A light reflex in the pupil was observed on the photos of all children with hyperopia greater than = 0.5 and myopia greater than = 2.0 D. A curvilinear relationship was observed (in the range -2 to -4 and +0.5 to +3 D) between the width of the light reflex in the pupil, easily measured on the photos and the degree of refractive error, determined by retinoscopy. The degree of ametropia could be estimated with reasonable accuracy (+/- 0.5 D) in the interval from -2 to -4 D and +0.5 to +3 D. The method can demonstrate the type and, to a limited extent, also the degree of refraction anomaly and may be of value in screening for refractive errors in children.

Child↗
PubMed2003

Ocular morbidity in schoolchildren in Kathmandu.

BACKGROUND/AIMS: Any information on eye diseases in schoolchildren in Nepal is rare and sketchy. A programme to provide basic eye screening to schoolchildren with an aim to provide services as well as gather information on ocular morbidity has been started. METHODS: All the children in the schools visited are included in the study. This programme is targeted at poor government schools, which are unable to afford this service. A complete eye examination is given to all the children including slit lamp examination, fundus evaluation and retinoscopy, and subjective refraction. RESULTS: A total of 1100 children from three schools are included in this report. 11% of our schoolchildren have ocular morbidity, 97% (117 out of 121) of which is preventable or treatable. Refractive error is the commonest type of ocular morbidity (8.1%). Myopia is the commonest type of refractive error (4.3%) as opposed to hypermetropia (1.3%). 12.4% of children with refractive error have already developed amblyopia. Strabismus is the second commonest type of ocular disability (1.6%). Alternate divergent squint is the commonest type of strabismus (1.4%). Traumatic eye injuries (0.54%), xerophthalmia (0.36%), and congenital abnormalities (0.36%) are much less common. CONCLUSION: A school eye screening cum intervention programme with periodic evaluation seems to be appropriate for countries like Nepal as most of the eye diseases found are preventable or treatable.

Adolescent↗
PubMed2006

Peripheral and posterior pole retinal lesions in association with high myopia: a cross-sectional community-based study in Hong Kong.

PURPOSE: To evaluate the prevalence and factors associated with posterior pole and peripheral retinal lesions in Chinese subjects with high myopia. METHODS: Three hundred and thirty-seven asymptomatic adults with high myopia of refractive error <or=-6 D were examined in a cross-sectional community-based study. All subjects underwent cycloplegic refraction, ultrasound biometry and dilated fundal examination. Statistical analysis was performed to assess factors associated with the presence of posterior pole and peripheral retinal lesions. RESULTS: The mean age of the 337 subjects was 36.0 years and the mean spherical equivalent refractive error was -10.2 D. Thirty-eight eyes (11.3%, 95% CI=8.1-15.2%) were found to have one or more posterior pole lesions and subjects with posterior pole lesion had significantly older age, longer axial length and higher degree of myopia (all P<0.001) compared with subjects without posterior pole lesion. After controlling for axial length, both the severity of refractive error and older age were significantly associated with the presence of posterior pole lesion (both P<0.001). For peripheral retinal lesions, 189 eyes (56.1%, 95% CI=50.6-61.5%) were found to have one or more peripheral retinal lesions. The presence of peripheral retinal lesion was associated with younger age and higher degree of refractive error (P=0.046 and 0.002, respectively). CONCLUSION: Posterior pole and peripheral retinal degenerative lesions were found in a considerable proportion of subjects with high myopia. As some of these retinal lesions might predispose to visual impairment, highly myopic individuals should be educated on the symptoms of various eye conditions and seek care immediately if symptoms arise.

Adolescent↗
PubMedDate not supplied

Older age as risk factor for deviation from emmetropia in pseudophakia.

PURPOSE: To find risk factors for deviation from emmetropia after cataract surgery in clinical practice. METHODS: We evaluated the refractive outcome in 106 patients who had underone phacoemulsification and in-the-bag IOL placement 115 +/- 10 days after surgery. Postoperative optical correction and refractive error (diopters of spherical equivalent--ED) were related to age and sex, pre-operative axial length and keratometric diopter power, and operative incision technique. RESULTS: Emmetropia was achieved in 15% of cases; 65% of eyes needed a myopic correction, averaging = 0.46 +/- 0.91 ED. The refractive error was 0.74 +/- 0.61 ED (< or = 1 ED in 77% of cases, < or = 2 ED in 97%). Both optical correction and refractive error were correlated to older age at the time of surgery (p=0.002 and p=0.001, respectively). Astigmatism appeared greater in clear-cornea incision than in limbar incision cases (p=0.05). CONCLUSIONS: The higher refractive error in patients aged over 73 years suggests that age may be a risk factor for deviation from emmetropia after cataract surgery.

Adult↗
PubMed1999

The refractive development of untreated eyes of rhesus monkeys varies according to the treatment received by their fellow eyes.

To determine the extent to which the visual experience of one eye may influence the refractive development of its fellow eye, we analyzed the data of untreated (UT) eyes of monkeys that received different types of unilateral pattern deprivation. Subjects were 15 juvenile rhesus monkeys, with five monkeys in each of three treatment groups: aphakic eyes with optical correction (AC), aphakic eyes with no correction (ANC), and eyes that were occluded with an opaque contact lens (OC). Under general anaesthesia, refractive error (D) was determined by cycloplegic retinoscopy and axial length (mm) was determined with A-scan ultrasonography. For measurements of refractive error of the UT eyes, there was a significant main effect of groups according to the treatment of the fellow eyes, F(2, 12) = 6.6. While UT eyes paired with AC fellow eyes (mean = +4.2 D) were significantly more hyperopic than the eyes of age-matched normal monkeys (mean = +2.4 D), t(25), = 2.5, UT eyes paired with OC fellow eyes (mean = -0.5 D) were significantly more myopic than the eyes of normal monkeys, t(25) = -9. UT eyes paired with ANC fellow eyes (mean = +1.9 D) were not significantly different from normal eyes. For measurements of axial length there was also a significant main effect of groups, F(2, 12) = 6.9. While UT eyes paired with AC fellow eyes (mean = 16.9 mm) were significantly shorter than the eyes of age-matched normal monkeys (mean = 17.5 mm), t(25) = 2.3, UT eyes paired with OC fellow eyes (mean = 18.1 mm) were significantly longer than the eyes of normal monkeys, t(25) = 2.3. UT eyes paired with ANC fellow eyes (mean = 17.5 mm) were not significantly different from the eyes of normal monkeys. The measurements of axial length and of refractive error of the UT eyes were also significantly correlated with one another, probably indicating that the differences in refractive error were due to differences in axial length, r = -0.8. The present data reveal that despite normal visual experience, UT eyes can have their refractive development altered, systematically, simply as a function of the type of pattern deprivation received by their fellow eyes. These data add to the growing evidence that there is an interocular mechanism that is active during emmetropization. As a consequence, future models of eye growth will need to consider both: (1) the direct influence of visual input on the growing eye; as well as (2) the indirect influence coming from the fellow eye.

Animals↗