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PubMed1977

Comparison of ultrasonic and photographic methods of axial length measurements of the eye.

The axial length of 25 eyes was measured by the photographic method and by ultrasonography. The photographic measurements were consistently larger than the ultrasonic, but analysis gave a correlation coefficient of r = 0-8483. The results suggest that the centre of rotation of the eye lies posterior to the anatomical centre of the globe. Using an empirical method of calculation and allowing for an error of +/-0-3 mm in the ultrasonic measurement, the photographic results were within +/-0-5 mm in 13 eyes and +/-1-0 mm in 7 eyes. The photographic method may be helpful as a guide to the power of intraocular lens implants and for comparing axial lengths in population studies.

Anthropometry↗
PubMed2003

Axial and peripheral eye length measured with optical low coherence reflectometry.

An optical low-coherence reflectometer (OLCR device) is described that allows the precise and noncontact measurement of eye length. The device measures eye length both on-axis and off-axis, thus enabling the determination of eye shape, an ocular parameter thought to be important in the development of refractive error. It is essential for several applications in ophthalmology and vision science. This improved OLCR device operates using a single-beam interferometer with a beam deflection mechanism that allows the precise measurement of eye length along the visual axis and within 15 deg horizontally and vertically from the fovea. The validity of this instrument and its revised software is evaluated by measuring the reproducibility of axial length results in an adult eye and an artificial eye, and by correlating axial eye length measured in a group of ten adult eyes with axial eye length obtained with A-scan ultrasound in the same eyes. The precision obtained with adult subjects is compared with that obtained with children.

Adult↗
PubMed2000

[Measurement of eye length and eye shape by optical low coherence reflectometry].

BACKGROUND: The precise and rapid measurement of eye length and eye shape are essential for investigating eye growth regulation and myopia. For this purpose, we developed an optical low coherence reflectometer and obtained preliminary measurements in volunteers. METHODS: The instrument includes a rotating glass cube to produce longitudinal scans at a velocity of 0.42 m/s and a repetition rate of approximately 13 scans/s. Heterodyne detection of light reflected from the anterior cornea and the posterior retina permits to measure axial eye length and eye shape (off-axis eye length). Each measurement consists of five consecutive scans. Reproducibility and precision were determined in one volunteer by measuring axial eye length five consecutive times, each time repositioning the eye. Eye shapes were determined in right eyes of four volunteers by measuring eye length every 3.3 degrees from 10 degrees nasally to 10 degrees temporally. RESULTS: Axial eye length measured repeatedly in one volunteer did not differ between or within the measurements (one-factor ANOVA). The average standard deviation was 11 microns. Eye shapes a) varied substantially among subjects and b) differed considerably from the corresponding shapes of spherical model eyes with identical axial eye lengths. CONCLUSION: The newly developed reflectometer permits the precise and rapid measurement of eye length and eye shape. Such measurements, especially in children, may provide important information about mechanisms of eye growth regulation and the development of myopia.

Eye↗
PubMed1993

Axial length of eyes with rhegmatogenous retinal detachment.

We conducted a prospective study of 226 eyes with nontraumatic rhegmatogenous retinal detachment; we examined patient characteristics as well as changes in axial length and corneal curvature induced by scleral buckling surgery. Eyes with a round hole in lattice degeneration were characterized by axial length that was longer than that of eyes with retinal tears with and without lattice degeneration. Sex and age also correlated significantly with axial length. Surgically induced changes in axial length depended upon the procedures performed, but the retinal detachment surgery primarily caused a change in the refractive status.

Adult↗
PubMed2002

Progressive axial myopia in a juvenile patient with traumatic glaucoma.

PURPOSE: To report a case of progressive axial myopia associated with traumatic glaucoma in a juvenile patient with no systemic disease. DESIGN: Interventional case report. METHODS: In a 15-year-old male, serial ocular examinations, including manifest refraction, tonometry, and axial eye length measurement, were performed over a 6-year period, beginning with blunt trauma, right eye, followed by a series of surgical procedures for traumatic cataract and glaucoma. RESULTS: A 4-diopter myopic shift (from -1.25 to -5.25) with a 1.5 mm increase in the axial eye length occurred, whereas the intraocular pressure increased from 21 to 46 mm Hg, during a 2-year period. The refraction, axial eye length, and intraocular pressure remained stable during the same period in the fellow, normal eye. CONCLUSION: Progressive axial myopia associated with traumatic glaucoma is possible in a juvenile patient in his late teens.

Adolescent↗
PubMed2004

The allometry and scaling of the size of vertebrate eyes.

We compiled data from the literature and colleagues to examine the relationship between eye axial length and body weight for vertebrates as well as birds, mammals, reptiles, and fishes independently. After fitting the data to logarithmic and semi-logarithmic models, we found that axial length of vertebrate eyes does obey a conventional logarithmic relationship with body weight rather than a semi-logarithmic relationship as suggested by the results of previous studies. The regression slopes and intercepts appear to be characteristic of various animal groups. The axial length of the eye is largest in birds and primates, smaller in other mammals (especially rodents) and reptiles, and widely varying in fishes.

Animals↗
PubMed1998

Analysis of zonular-free zone and lens size in relation to axial length of eye with age.

PURPOSE: To evaluate the anatomical relationships of the zonular-free zone (ZFZ) of the anterior capsule and crystalline lens diameter in relation to the axial length of the eye with age. SETTING: Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea, and Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHOD: Various ocular structures in 122 eyes obtained post-mortem were measured without prior preparation. The correlation between age, anterior-posterior (A-P) length and globe size, and diameters of the cornea, crystalline lens, and ZFZ were analyzed. RESULTS: The average A-P globe length, and corneal, lens, and ZFZ diameters were 24.48, 11.67, 9.65, and 6.93 mm, respectively. There was no significant relationship between A-P length and globe size and corneal diameter in different age groups. The ZFZ size varied negligibly among age groups. There was a statistically significant correlation between lens diameter and age (correlation coefficient = 0.2647; P < .01) and lens diameter and A-P globe length (correlation coefficient = 0.3183; P < .001). CONCLUSIONS: When choosing an intraocular lens, one should consider the patient's age and the A-P globe length. Six eyes (5%) showed unusual anterior insertion of zonular attachment, which reminds us to be prudent with a large paracentral capsulorhexis.

Adult↗
PubMed1998

High precision biometry of pseudophakic eyes using partial coherence interferometry.

PURPOSE: To investigate the applicability of the scanning version of dual-beam partial coherence interferometry (PCI) for measuring the anterior segment and axial length of pseudophakic eyes in a clinical setting and to determine the achievable precision with this biometry technique. SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. METHODS: Partial coherence interferometry was performed in 39 pseudophakic eyes of 39 patients after implantation of a foldable acrylic intraocular lens (IOL). RESULTS: Effective lens position (ELP), IOL thickness and lens-capsule distance (LCD) were determined with a precision of 2 to 3 microns; corneal thickness and axial eye length, with a precision of 0.8 and 5.0 microns, respectively. The mean ELP of the IOL was 4.093 mm +/- 0.290 (SD). In 7 eyes (18%), a positive LCD of 68 +/- 40 microns was detected with PCI. Mean corneal thickness was 526.4 +/- 31.5 microns; mean IOL thickness, 791.5 +/- 40.2 microns; and mean axial length, 23.388 +/- 0.824 mm. CONCLUSION: The scanning version of PCI enables high precision (< or = 5 microns) and high resolution (approximately 12 microns) biometry of pseudophakic eyes that is better than conventional ultrasound by a factor of more than 20. For the first time, positive LCD, a possible risk factor for posterior capsule opacification, could be detected and quantified. Furthermore, this technique offers a high degree of comfort for the patient since it is a noncontact method with no need for local anesthesia or pupil dilation and has a reduced risk of corneal infection.

Acrylates↗
PubMed1991

[Accuracy of ultrasound measurements of the axial length of the eye].

Ultrasonic assessment of the axial length of the eye provides important baseline data for the calculation of the dioptric power of an artificial intraocular lens. The accuracy of ultrasonic biometry performed by an OPHTASCAN B apparatus is discussed based on evaluation of a group of repeated measurements of the axial length and depth of the anterior chamber in 592 bulbi.

Adult↗
PubMed1999

Contact or immersion technique for axial length measurement?

PURPOSE: The purpose of the present study was to determine whether contact and immersion A-scan techniques produce comparable measures of the magnitude of eye axial length. METHOD: A prospective study in which 225 consecutive patients scheduled for cataract surgery in a private day surgery setting had axial lengths measured with an Alcon Ocuscan machine (Alcon Australia, Frenchs Forest, NSW, Australia) using both contact and immersion techniques. Twelve patients had both techniques repeated on a separate occasion. RESULTS: Measurements of eye axial length obtained by the immersion technique averaged 0.1 mm longer than those obtained by the contact technique. A difference in axial length values was confirmed in eyes subjected to repeated measurements. CONCLUSIONS: Both techniques give consistent results, but the difference between axial lengths measured by the two techniques has implications for choice of intra-ocular lens power.

Anthropometry↗
PubMed2005

[Clinical features of 233 cases of keratoconus].

OBJECTIVE: To analyze clinical features of keratoconus. METHODS: The case history of keratoconus patients who underwent penetrating keratoplasty, epikeratophakia or deep lamellar keratoplasty in our hospital during January 1993 to March 2002 was reviewed, and inquiry form was sent to those who without complete data. Patients were followed during January 2000 to March 2002. Two hundred and thirty three cases of keratoconus were enrolled in this study with 216 males and 17 females. Patient's family history, systemic complications, refractive status, progress of disease, eye axial length and anterior chamber depth were recorded. RESULTS: The clinical natural history of these patients followed the model of "myopia-astigmatism-poor spectacle correction-acute corneal hydrops or stromal scar". The presenting age of myopia ranged from 6 to 29 years, with a mean age of 13.8 years, 10.1% (22/219) of the patients were younger than 10 years, 67.1% (147/219) were between 11 and 15 years. The interval time between emerging myopia and poor spectacle correction (best corrected visual acuity less than 20/200) was ranged from 1 to 20 years, of which 85.2% (161/189) were shorter than 6 years. Twenty percent (47/233) of the patients had acute corneal hydrops in one eye at the age of 12 to 31 years, and 4.3% of them (2/47) resulted in corneal perforation. Thirty-four patients had corneal stromal scars 1 to 13 years after keratoconus developed, and 94.1% of them (32/34) were within 8 years. Topography examination demonstrated a tendency of the cone base position progress: first, paracentral-enlargement following dominant astigmatism axis, then, enlargement along smaller astigmatism axis, and finally, the cone base moving centrally. The eye axial length averaged at (25.9 +/- 1.4) mm, the depth of anterior chamber (AC) were (4.3 +/- 0.3) mm, 89.7% (279/311) eyes had an axial length longer than 24 mm. All cases had an asymmetry clinical progress course. Two cases had Down syndrome, 2 with intelligence defect. No family history was noted in this study. CONCLUSIONS: Keratoconus in Han nationality of Shandong Province has a relatively earlier age onset. These eyes tend to have a deeper AC with higher incidence of longer axial length.

Adolescent↗
PubMed1976

Simple method of determining the axial length of the eye.

By photographing the corneal reflex in two positions of gaze and measuring the radius of curvature of the cornea it is possible to calculate the radius of rotation of the eye. The measurements obtained in this way showed a high correlation with refraction in a series of 80 eyes. The axial length obtained by this method was about 3 mm greater than that obtained by ultrasonographic or x-ray methods, and the reasons for the discrepancy are discussed.

Anthropometry↗
PubMed1989

Retrospective study of retinal detachment following neodymium:YAG laser posterior capsulotomy.

A retrospective study of 1,000 cases that had Nd:YAG laser posterior capsulotomy after cataract surgery is presented. We analyzed the correlation of the patient's age, axial length of the eye, method of cataract surgery, and laser parameters (exposures, energy, and burst mode) with the incidence of retinal detachment (1.6% overall). The highest risk for retinal detachment (12.3%) was in patients with an axial eye length of 26.1 mm to 28.0 mm. The average age of patients with retinal detachments was 60.6 years, ten years younger than the collective average age. Laser parameters, such as energy, exposures, and burst mode, and the method of cataract surgery (extracapsular or phacoemulsification) did not correlate with the incidence of retinal detachment. After surgical treatment of the 16 retinal detachments, a good postoperative visual acuity (better than 20/40) was achieved in most cases.

Adolescent↗
PubMedDate not supplied

Ocular and systemic characteristics of Duane syndrome.

The clinical features of 63 patients with Duane syndrome are described in this report. All data in the study were gathered retrospectively except for measurements of vertical palpebral fissure and axial eye length, which were investigated prospectively. The following new aspects of the syndrome are emphasized: 1) In most cases with heterotropia, the angle of deviation was not large (< or = 25 prism diopters). 2) Visual acuity of 0.66 (20/30) or better was recorded in 94% of the affected eyes. 3) Smaller palpebral fissure (by 1 mm or more) of the affected eye was measured in primary position among 9 of 40 (22%) unilateral cases. 4) The axial length of the affected eye (mean, 22.8 +/- 0.6 mm) was not significantly different from the uninvolved eye. 5) Two cases of heterochromia iridis (3.2%) were found among the Duane syndrome patients. 6) A 4.8% prevalence of high-tone hearing loss was detected, in addition to 4.8% of sensorineural deafness.

Adolescent↗
PubMed1988

Calculating axial length in the aphakic and the pseudophakic eye.

The axial length of 149 eyes (84 pseudophakic and 65 aphakic) was calculated by refractive means and compared with the axial length determined by ultrasound. The mean error (+/- SD) between the measured and the calculated axial length (measured minus calculated) was 0.02 mm (+/- 0.51) and 0.13 mm (+/- 0.54) for the aphakic and the pseudophakic eyes, respectively. The mean error was not significantly different from zero (P greater than .05). Calculation of the axial length may represent a valuable alternative to biometry for the aphakic and the pseudophakic eye.

Aged↗
PubMed1987

Ultrasonographic measurement of the posterior coats of the eye and their relation to axial length.

In 159 eyes with a spherical correction varying from +14.0 to -27.0 diopters, the axial length and thickness of posterior ocular coats were measured ultrasonographically. As proven in experimental studies, retina, choroid, and sclera were resolved in a considerable percentage of cases by combining A- and B-mode techniques of modern ultrasonographic equipment. The presumed close inverse correlation between the axial length of the eye and ocular coat dimensions was confirmed by statistical analysis. These values were used to calculate the approximative volume of the posterior half of the ocular coats. There was evidence for a constant tissue volume regardless of the difference in surface and axial length parameters between hyperopic and myopic eyes. Results are discussed and compared with theories of axial growth under physiological and pathological conditions.

Animals↗
PubMed1992

Changes in the ocular dimensions after trabeculectomy.

Ocular wall dimensions (axial eye length, anterior chamber depth, lens thickness, vitreous length, thickness and volume of the ocular wall) were determined by echobiometry on 10 eyes of 10 patients with glaucoma one day before and four days after trabeculectomy. The results showed significant differences: decreased axial eye length, and increased thickness and volume of the ocular wall were found after trabeculectomy. The observed changes in the ocular dimensions might be due to ocular hypotony and postoperative inflammation. Echographic follow-up of the changes in the ocular wall is a useful monitor to study alteration in eye dimensions after glaucoma surgery.

Aged↗