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At least 1,621 records · Page 90Linked to original sources
PubMed1993

[Streak retinoscopy. Optical principles and practical recommendations].

The optical principles of streak retinoscopy are demonstrated by diagrams and by optical models. The phenomena observed in the proband's pupil are being explained in two ways: In the first explanation, the image on the proband's retina and its movements are considered, or rather their projection into space; this explanation corresponding to the term "retinoscopy" is commonly used in English textbooks. In the second explanation, the limitations of the light bundle by the proband's and the observer's pupils are considered; hence the term skiascopy (sigma kappa iota alpha = shadow), commonly used in the German literature. The practical hints include retinoscopy through the phoropter, suggestions for the examination of children both with and without cycloplegia, the measurement of accommodation, the detection of opacities and irregularities in the optical media, and the analysis of visual field defects caused by optical anomalies, such as refraction scotomas.

Accommodation, Ocular↗
PubMed1992

[The cycloplegic effect of atropine in comparison with the cyclopentolate-tropicamide-phenylephrine combination].

Atropine is thought to produce the most effective cycloplegia in early childhood. Cyclopentolate and Tropicamide are the best known short acting cycloplegic agents. Phenylephrine is an adrenergic agent and has also a cycloplegic effect. In this study we compared a combination of Cyclopentolate, Tropicamide and Phenylephrine with Atropine and observed no difference between them.

Accommodation, Ocular↗
PubMed1990

[Initial experiences with refractive corneal surgery].

The present paper reports on the advice customarily given to patients and on methods of establishing the indication for radial keratotomy at the author's clinic. Examples are given to illustrate the problems involved. The unsatisfactory results in 2 cases following epikeratophakia are discussed.

Adult↗
PubMed1987

[Evaluation of Scheimpflug photographs in transitory hypermetropia].

Scheimpflug photography of lenses with transient hypermetropia in cases of diabetes mellitus revealed an enlargement of the axial diameter of the cortex and especially of the nucleus of the lens. This transient hypermetropia is thought to stem from a decrease in the refractive index of the lens cortex and nucleus.

Diabetes Mellitus, Type 2↗
PubMed1985

[Equivalency of different methods of measuring lens power].

Mathematical error analysis shows that the prognosis of IOL powers on the basis of theoretical optical formulas for calculating lens power is no more accurate than the regression (SRK) formula. The minimum error in a recommended lens power is at present between +/- 0.6 and +/- 1.0 D. As a result of this range of error there is a range of equivalence of the two formulas, and the vast majority of cataract patients (85%) are within this range. However, in hyperopic eyes the SRK formula is clearly superior to the theoretical optical formulas for a clinically useful prognosis.

Aphakia, Postcataract↗
PubMed2001

A randomized comparison of prism adaptation and augmented surgery in the surgical management of esotropia associated with hypermetropia: one-year surgical outcomes.

OBJECTIVE: To compare motor and sensory 1-year surgical outcomes in patients with hypermetropic esotropia, managed with either augmented surgery based on the average of the near deviation with and without correction or preoperative prism adaptation. METHODS: Forty-three patients with hypermetropic esotropia without distance-near disparity entered a randomized prospective evaluation of augmented surgery (group A, 27 patients) versus prism adaptation (group P, 16 patients). The formula for augmenting the amount of the rectus muscle recession was based on the average of the near deviation with and without correction in group A and the prism-adapted angle of deviation in group P. During prism adaptation, 9 of 16 patients in group P responded to prism. Motor and sensory outcomes of the Worth 4-dot test at 6 and 0.33 m and the Titmus stereotest were evaluated 1, 3, 6, and 12 months after surgery. RESULTS: Postoperative deviations of 8 PD or less at distance were achieved in 24 of 27 patients (89%) of group A and in 7 of the remaining 8 patients (88%) of prism responders and in all 7 prism nonresponders (100%) in group P. No significant difference existed between groups A and P, as well as between the prism responders and prism nonresponders in group P in terms of near and distance deviation 1 year after surgery. The sensory outcomes improved over time in group A and prism responders. CONCLUSION: There were no significant differences in the surgical outcomes between each group. However, the small sample size may limit the power to detect any statistically significant differences.

Adaptation, Ocular↗
PubMed2002

Sensitivity of photoscreening to detect high-magnitude amblyogenic factors.

PURPOSE: To determine the sensitivity of a unique pupil-size based set of referral criteria of the MTI PhotoScreener(Medical Technology and Innovations, Inc, Cedar Falls, Iowa) to detect high magnitude refractive error. METHODS: The photoscreening photographs of 949 preschool children previously analyzed were reevaluated with the new referral criteria. The original photographs had been obtained from pediatricians' offices and public health and Women, Infants, and Children's (WIC) clinics. The results of this analysis were compared with the gold standard clinical examination and cycloplegic refraction. Sensitivities were calculated for amblyogenic factors based on the magnitude of the refractive error. RESULTS: For 26 patients with anisometropia, the sensitivity to detect anisometropia increased from 46% for +1.25 or greater spherical interocular difference to 100% for +2.50 spherical intraocular difference. For 36 patients with hypermetropia in at least 1 meridian ranging from +3.75 to +7.50 D, sensitivity increased from 53% to detect +3.75 D or greater to 70% for +5.00 D or greater. The sensitivity to detect hypermetropia of +5.75 D or greater was 100%. These criteria detected 82% of patients with astigmatism greater than or equal to +3.00 D, and 100% of patients with astigmatism greater than +3.50 D. CONCLUSION: It is crucial that screening programs avoid over-referrals caused by high false-positive screening rates. The sensitivity of our new criteria increases with higher magnitude refractive error; patients with moderate and severe amblyogenic factors are almost never missed. While the sensitivity to detect lower magnitude refractive error is poor, the amblyogenic impact of such errors remains to be determined.

Amblyopia↗
PubMed2003

Variability of retinal steepness at the posterior pole in children 7-15 years of age.

PURPOSE: Considerable evidence suggests that both axial and peripheral refraction play important roles in eye growth control. The large variability in peripheral refraction seen in adults and children indicates that the peripheral retina is exposed to a wide range of refractive errors. The current lack of appropriate measurement techniques has hampered the determination of whether variability in peripheral refraction between individuals can be correlated with variability in retinal steepness. An Optical Low Coherence Reflectometer (OLCR) was developed to determine retinal steepness. METHODS: Retinal steepness was assessed in right eyes of 63 children 7-15 years of age by measuring eye length (EL) and spherical equivalent refraction (SER) axially and at 15 degrees temporally, nasally, inferiorly and superiorly with OLCR and Binocular Auto-Refractometry, respectively, during cycloplegia. At each peripheral location, relative peripheral EL and SER (i.e., the difference between peripheral and axial readings) were compared between myopic, emmetropic and hyperopic eyes, and the correlation between relative peripheral EL and SER was analyzed. RESULTS: Although the standard deviations were large, significant differences in relative peripheral EL and SER between refractive groups as well as a significant correlation between relative peripheral EL and SER were observed at several of the assessed locations. CONCLUSIONS. The results strongly suggest that peripheral refraction is correlated with retinal steepness and that previously observed variability in peripheral refraction chiefly reflects variability in retinal steepness. If peripheral refraction represents a determining parameter in the control of eye growth, the precise measurement of retinal steepness could be used not only to improve estimates of myopic progression, but also to identify children who are at high risk of developing myopia. It may lead to specialized clinical/optical treatments, e.g. the correction of not only axial but also peripheral refractive errors, which are more effective than current treatments in individuals who are at risk of myopia development or progression.

Adolescent↗
PubMed2003

Neural pathways subserving negative lens-induced emmetropization in chicks--insights from selective lesions of the optic nerve and ciliary nerve.

PURPOSE: Active emmetropization describes the process by which young eyes regulate their growth to eliminate refractive errors. The purpose of this study was to re-investigate the role of the brain in compensation to imposed hyperopic defocus (negative lenses), specifically, to assess whether a retina-brain link and/or an intact ciliary nerve are required for this emmetropizing response. Data from previous related studies are equivocal. METHODS: Unilateral lesion surgery involving either or both optic nerve section (ONS) and ciliary nerve section (CNS), was performed on 2-3 day old White-Leghorn chicks to interrupt communication between the eye (retina in the case of ONS) and brain. After a recovery period of 4 days, lesioned eyes were fitted with either -5 or -15 D lenses or diffusers (6-9 per group). An additional lesion group underwent unilateral CNS and was fitted with -5 D lenses bilaterally. Finally 3 groups that underwent the same unilateral optical treatments but no surgery were included as controls for analyzing lesion-induced changes. Complete sets of measurements, involving retinoscopy for refractive errors, and high frequency A-scan ultrasonography for axial ocular dimensions, were made at the beginning (baseline), and end of a 4 day treatment period. Additional ultrasonography data were collected after 1 and 2 days of treatment. Optical treatment effects were expressed as changes in interocular differences from baseline values. RESULTS: All three lesions produced hyperopic shifts in refraction (evident in baseline values), although this effect was minimal for the ONS+CNS group. Choroidal thickening as well as increased anterior chamber depth and lens thinning were observed in all cases but vitreous chamber depth was reduced in only the ONS group. In response to the -5 D lens, the control (nonlesioned) group showed nearly complete compensation, while full compensation was not achieved to the -15 D lens over this short treatment period. The diffuser group showed the largest change, which was also in the direction of myopia. Both the ONS and CNS groups showed near normal compensation, as indexed by the changes in refractive errors relative to their respective baseline values. In contrast, the ONS+CNS lens groups overcompensated, by 130% and 54% for the -5 D and the -15 D lens groups respectively. Form deprivation responses were slightly exaggerated in both ONS and ONS+CNS groups, the latter group again showing the largest response. Enhanced vitreous chamber growth was evident under all conditions and correlated well with the refractive changes across the groups. DISCUSSION: The data imply that an intact retina-brain link is not required for compensation to hyperopic defocus and thus emmetropization. However, the data also imply interactions between higher centers and the eye. The emmetropization set-point appears to be recalibrated after ONS surgery. The data also indicate a role of the ciliary nerve as an important conduit for signals that exercise a restraining influence on eye growth.

Accommodation, Ocular↗
PubMed2004

Refractive evaluation in children with growth defect.

PURPOSE: Growth hormone (GH) is considered essential for postnatal somatic growth, exerting its effects on growth by hepatic production of IGF-I. IGF and other growth factors interact with the developing ocular tissues by influencing the synthesis of the extracellular matrix of the sclera and by inducing angiogenesis. The association between optic nerve hypoplasia, reduced retinal vascularization and GH deficiency (GHD) is well known. The purpose of this study is to evaluate the possible influence of congenital GHD on the refraction and on the emmetropization process. METHODS: Eighty children with congenital GHD had a thorough ophthalmologic examination, including cycloplegic refraction and axial length measurement. As a control group we enrolled 483 healthy children. RESULTS: In accordance with other epidemiological studies, the control group showed a slightly myopic mean defect; on the contrary, in GHD group we found a hyperopic defect, related to a shorter axial length, with statistically significant differences. CONCLUSIONS: Our findings emphasise the possible role of growth hormone in ocular development, and its interaction with the physiological process of emmetropization.

Adolescent↗
PubMed2003

Emmetropisation in normal and strabismic children and the associated changes of anisometropia.

The purpose of this study was to measure whether emmetropisation failed in children who had strabismus irrespective of their refraction in infancy, and to record simultaneous changes in anisometropia. We also report how often hypermetropia increased before these children presented with esotropia. A total of 2920 infants had a cycloplegic retinoscopy at age 5-7 months and again at 42 months or when defective vision was identified. Changes of refraction in 210 children with strabismus are compared with the remaining 2710 who did not. When the spherical equivalent of the fixing eyes was > +2.75 D in infancy, hypermetropia decreased less in both eyes of those who had microtropia (p <.001) and heterotropia (p <.001) than in normal children. When it was < +2.75 D, the spherical and/or cylindrical refraction more often remained outside the 'normal' range in both eyes of those who had microtropia and heterotropia (p <.05). Emmetropisation was deficient in both eyes of at least 80% of these strabismic children irrespective of their refraction in infancy. Furthermore, in the strabismic children, the mean change of refraction was less (p <.05) in their fellow eyes than in their fixing eyes, the difference between the two eyes being on average three times greater than that in those who had normal vision. Thus, anisometropia increased in 53% of those who had strabismus but remained within normal limits (< ca. 0.75 D spherical equivalent) in 94 % of those who did not. 'Abnormal' anisometropia in infancy did not, per se, permanently affect vision because 72% of all those who had it did not have strabismus. Finally, the spherical hypermetropia of fixing eyes increased in only 35% of the children with esotropia - similar to the incidence in those who had a microtropia (p =.36). This does not obviously support the concept that increasing hypermetropia causes accommodation to increase before convergence.

Accommodation, Ocular↗
PubMed2006

Objective blur thresholds in free space for different refractive groups.

The aim of the current study was to measure the objective depth-of-focus (DOF) of myopes (MYO) in free space and compare them with emmetropic (EMM) and hyperopic (HYP) cohorts. The objective DOF was measured in 35 visually normal, young adults including 16 MYO, 13 EMM, and 6 HYP using the Power Refractor (PR II). The DOF was larger in the MYO and HYP than in the EMM. The larger objective DOF found in the MYO subgroup is in agreement with previous studies assessing the DOF subjectively. This finding is consistent with current thinking that increased amounts of retinal-defocus integrated over extended time may be myopiogenic. In agreement with earlier clinical and computer simulation studies, hyperopes demonstrate a relative resistance to increased retinal defocus.

Accommodation, Ocular↗
PubMed2005

Ophthalmic aspects of GAPO syndrome: case report and review.

This paper reports on a 36-year-old woman with GAPO syndrome, a rare autosomal recessive condition characterized by growth retardation (G), alopecia (A), pseudoanodontia (P), and optic atrophy (O). Her parents are consanguineous and one of her sisters is also affected. Since the first description by Anderson and Pindborg in 1947, 27 individuals have been reported with this diagnosis. They were from at least 19 different families (four of them from Brazil, including the present one), suggesting a founder effect. The phenotype of this condition, initially considered as the result of an ectodermal dysplasia, could be attributed to the accumulation of extracellular connective tissue matrix and its progressive character must be pointed out. The clinical findings, especially ophthalmological features that include bilateral glaucoma, are reviewed and discussed.

Adult↗
PubMed2005

Hereditary high hypermetropia in the Faroe Islands.

PURPOSE: To characterize the phenotype of two families with high hypermetropia from the Faroe Islands. METHODS: Ophthalmologic evaluation including ultrasound oculometry and anthropometric measurements. RESULTS: Of the 40 examined family members, 15 individuals (8 males, 7 females; ages: 6-77 years; mean: 36.5 years) had small deep-set eyes with high hypermetropia (median: + 16.5 D; range: + 7.75 to + 22), short axial eye length (< 21 mm), and a thickened eye wall. The median corrected visual acuity was 0.4 (0.2-0.9). Ocular complications included angle-closure glaucoma in six eyes, uveal effusion in three eyes, cataract in two eyes, and esotropia with amblyopia in three eyes. An emergency case of uveal effusion and retinal detachment after Yag iridotomy eventually responded to systemic corticosteroids and scleral resection surgery with a slow visual recovery. No associated ocular or systemic malformations were found in the series. In addition to the two examined families, six smaller Faroese families with high hypermetropia are briefly reported. CONCLUSIONS: The study highlights the signs and symptoms of a rare hereditary phenotype characterized by a short axial length mainly confined to the posterior segment of the eye, a shallow anterior chamber, and a thickened eye wall. The morphological characteristics predispose for sight-threatening complications such as angle-closure glaucoma, chorioretinal pathology including uveal effusion, and amblyopia. Regular ophthalmic follow-up is therefore of obvious importance in families known to have small eyes/high hypermetropia. An endemic high prevalence in the Faroe Islands suggests the presence of a founder effect, and further genetic research would probably indicate pseudodominant rather than dominant transmission

Adolescent↗
PubMed1996

Impaired sensitivity to visual contrast in children treated early and continuously for phenylketonuria.

Contrast sensitivity was assessed in 47 children aged 5.4-9.8 years: 12 with phenylketonuria (PKU), six unaffected siblings and 29 children from the general population. Children with PKU, despite early and continuous treatment and despite phenylalanine (Phe) levels within accepted limits, were impaired across the range of spatial frequencies [1.5-18.0 cycles per degree of visual angle (c.p.d.)]. They were most impaired at the next to the highest spatial frequency, where "group' accounted for 70% of the variance in sensitivity to contrast, controlling for acuity, sex, age and test site. Never, at any spatial frequency, was the contrast sensitivity of any PKU subject better than that of his or her sibling. All subjects were tested under conditions of 20/20 vision, with correction if needed. The mean IQ of PKU subjects was 99; IQ was not significantly related to contrast sensitivity performance. We interpret these findings as support for Diamond's hypothesis that moderately elevated plasma Phe levels (3-5 x normal), combined with reduced plasma tyrosine (Tyr), moderately reduce the levels of Tyr reaching the eye and brain, which adversely affects those dopamine neurons that fire and turn over dopamine most rapidly (the dopamine neurons in the retina and those projecting to prefrontal cortex). This would lead to the deficit in contrast sensitivity found here and to the selective deficit in prefrontal cortex cognitive functions previously reported in PKU children under moderately good dietary control.

Analysis of Variance↗
PubMed1999

Epithelial scrape for photorefractive keratectomy overcorrection associated with induced regression.

PURPOSE: To study the effect of combined corneal epithelial scrape and contact lens wear treatment on regression in eyes with symptomatic overcorrection after photorefractive keratectomy (PRK) or PRK retreatment. METHODS: Fifteen eyes had corneal epithelial scrape with a scalpel followed by soft contact lens wear for approximately 1 month. Eight of the eyes were treated 3-4 months after the laser procedure, and seven eyes were treated >4 months after laser treatment. Fifteen eyes that had the same level of PRK correction and monitored during the same interval after PRK were used as matched control eyes. RESULTS: Epithelial scrape was performed for mean spherical equivalent (SE) of +1.1+/-0.4 diopters (D) (range, +0.50 to +1.75 D) at mean 6.1+/-3.2 months after PRK or PRK retreatment. The SE in these eyes was +0.5+/-0.6 D (range, -0.25 to +1.25 D) 3 months after epithelial scrape and +0.4+/-0.5 D (range, -0.75 to +1.25 D) 6 months after scrape. The change in scraped eyes at 3 and 6 months compared to before scrape was statistically significant (p = 0.001 and p = 0.001, respectively). The change in mean SE at 6 months after scrape (-0.7+/-0.5 D) was significantly different than the change noted in matched control eyes that were not scraped (-0.1+/-0.2 D) over the same interval after the PRK or PRK retreatment procedure. The change in SE at 6 months after epithelial scrape was greater for the eyes scraped 4 months or less (mean, 3.6+/-0.5 months) after PRK (-0.9+/-0.3 D) than eyes scraped >4 months (9.0+/-2.6 months) after PRK (-0.4+/-0.5 D). This difference approached statistical significance (p = 0.06). CONCLUSIONS: Epithelial scrape and soft contact lens treatment for symptomatic overcorrection after PRK may induce regression and is more likely to be effective when performed <4 months after the primary PRK or PRK retreatment procedure.

Adult↗
PubMed2002

Two cases of a penetrating keratoplasty with tissue from a donor who had undergone LASIK surgery.

PURPOSE: To report two cases of penetrating keratoplasty using tissue from a donor who had undergone laser-assisted in situ keratomileusis (LASIK) surgery before its transplantation. PARTICIPANTS: Two patients who had penetrating keratoplasties and received donor corneas from eyes that had previous LASIK. INTERVENTION: The two patients underwent corneal transplantation by two different surgeons who were unaware that the donor eyes had previous LASIK treatment. RESULTS: Penetrating keratoplasty was completed without complication in both cases, although a separation of the corneal lamellae was noted during surgery in one of the cases. The two patients are doing well at 5.5 months postsurgery. CONCLUSION: With the increasing popularity of laser refractive surgery, eye banks should increase their awareness and refine screening techniques to rule out refractive surgery in the donor corneas. The long-term follow-up of those patients will reveal if surgical success was compromised by prior refractive surgery.

Aged↗