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Objective: To describe ocular biometry relationships in older white adults., Methods: Ocular dimensions were measured with partial coherence laser interferometry in 1968 persons (aged 58-100 years, 59% female) seen at the fourth examination of the Beaver Dam Eye Study. Generalized estimating equations-modeled associations of age, sex, height, and education with ocular dimensions: axial length, corneal curvature radius, and anterior chamber depth., Results: The mean axial length was 23.69 mm; mean corneal curvature radius was 7.70 mm; and mean anterior chamber depth was 3.11 mm. Participants younger than 65 years had larger eyes (longer axial length, greater corneal curvature radius, and deeper anterior chamber depth) than persons aged 75 years or older. Mean axial length was 23.86 mm, 23.66 mm, and 23.55 mm in people aged 64 years and younger, 65 to 74 years, and 75 years or older, respectively. Generally, larger eyes were observed in men (vs women) and in taller (>178 vs 16 vs <12 years) persons. Adjustment for height accounted for all sex differences. Age differences in axial length were attenuated (P = .06) after adjustment for both height and education., Conclusion: In this older white population, age and sex variations in ocular dimensions are partially explained by differences in stature and education.

Objectives: To test whether dynamic contour tonometry yields ocular pulse amplitude (OPA) measurements that are independent of corneal thickness and curvature, and to assess variables of observer agreement., Methods: In a multivariate cluster analysis on 223 eyes, the relationship between central corneal thickness, corneal curvature, axial length, anterior chamber depth, intraocular pressure, sex, age, and OPA measurements was assessed. Intraobserver and interobserver variabilities were calculated from repeated measurements obtained from 8 volunteers by 4 observers., Results: The OPA readings were not affected by central corneal thickness (P = .08), corneal curvature (P = .47), anterior chamber depth (P = .80), age (P = .60), or sex (P = .73). There was a positive correlation between OPA and intraocular pressure (0.12 mm Hg/1 mm Hg of intraocular pressure; P<.001) and a negative correlation between OPA and axial length (0.27 mm Hg/1 mm of length; P<.001). Intraobserver and interobserver variabilities were 0.08 and 0.02 mm Hg, respectively, and the intraclass correlation coefficient was 0.89., Conclusions: The OPA readings obtained with dynamic contour tonometry in healthy subjects are not influenced by the structure of the anterior segment of the eye but are affected by intraocular pressure and axial length. We found a high amount of agreement within and between observers.

Objective: To evaluate the effect of central corneal thickness (CCT), corneal curvature, and axial length on applanation tonometry in an in vivo study., Methods: In a masked, prospective clinical trial, we examined 125 eyes of 125 patients scheduled for cataract surgery. Corneal curvature was measured by means of keratometry and axial length by A-scan ultrasonography. By cannulating the anterior chamber before surgery, intraocular pressure (IOP) was set to 20, 35, and 50 mm Hg in a closed system by means of a water column. After measuring thickness, the IOP was measured with an applanation tonometer. Pearson product moment correlations and multiple linear regression analyses were performed, and significance levels were evaluated by the paired, 2-tailed t test., Results: The difference between measured and real IOP was significantly dependent (P < .001) on CCT. The associations between IOP and corneal curvature or IOP and axial length were not statistically significant (P = .31). The association between IOP reading and CCT is shown in the "Dresdner correction table," which illustrates an approximately 1-mm Hg correction for every 25-microm deviation from a CCT of 550 microm. The correction values were positive as thickness decreased and negative as thickness increased., Conclusions: Central corneal thickness significantly affects IOP readings obtained by applanation tonometry according to the Goldmann principle. A correction of IOP readings by considering CCT according to the Dresdner correction table might be helpful for determining an accurate IOP value.

Objective: To determine the feasibility, reliability, and validity of using partial coherence interferometry, a noncontact method that detects interference patterns from various layers of the eye, to measure axial length in young children., Methods: The right eye of 64 subjects (mean age, 8.4 y; age range, 3.4-12.9 y; best-corrected visual acuity >or=20/30) was measured. Subjects fixated monocularly on the collimated light pattern from a laser diode (the alignment beam) and the operator used a video monitor to align the corneal reflection in the optical path. Axial length was measured during an 0.8-second scan using interference patterns from a collimated short coherence superluminescence diode aligned coaxially with the laser diode. Five series of 16 readings each were obtained. The average axial length for each of the 5 series of readings was calculated. Main Outcome Measure Axial length., Results: Within-subject precision of axial length measurements was high, with an overall SE of measurement of 8 micro m for individual subjects across the 5 sessions (95% confidence interval, +/-16 micro m). Subgroup analysis showed that sex, age, spherical equivalent, and refractive error exerted statistically significant effects on precision, but all of the differences among subgroups were 3 micro m or less and likely to be insignificant clinically. Axial length measured by partial coherence interferometry varied systematically, with factors known to influence eye length (ie, age and refractive error), further validating the measurement method., Conclusion: The partial coherence interferometry technique provides reproducible, extraordinarily precise eye length measurements in young children and should enable novel approaches to study eye growth and refractive development.

Objective: To determine the effect of the axial length of the eye on laser spot size and irradiance., Design: Experimental study using a calibrated Gullstrand-type model eye., Methods: The model eye, which was fitted with a scale of half circles in the center of the artificial fundus, was first examined using 2 different fundus imaging systems, then with a setup of a slitlamp, 2 indirect condensing laser lenses, and a laser unit with a spot size of up to 7 mm. The axial length of the model eye was set to different values ranging from 20 to 31 mm, and the magnifications of the fundus imaging systems and the laser lenses were calculated and compared for a treatment spot with a diameter of 4 mm. The laser irradiance for treating the spot at different axial lengths was also recorded., Results: Whereas the magnification of a fundus imaging system is inversely related to the axial length, the laser spot size is directly related to axial length when using indirect condensing laser lenses. Therefore, the changes of magnification produced by axial ametropia are mostly compensated, so that the intended size of the treatment spot is obtained even in eyes with a high axial ametropia. The laser irradiance, on the other hand, has a significant variation for the observed range of the axial length., Conclusion: Axial length has a significant effect on laser spot size and laser irradiance., Clinical Relevance: The effect of axial length on laser spot size and laser irradiance may be ignored when administering photodynamic therapy with verteporfin but has to be considered for transpupillary thermal treatment of choroidal neovascular lesions.

Objective: To determine the effect of age on the retardation of axial elongation in neonatal monkey eyes following the extraction of the crystalline lens., Methods: A monocular lensectomy was performed on 4 rhesus monkeys when they were 4 days, 2 weeks, 7.5 months, and 1 year of age. Longitudinal measurements of axial lengths and keratometry readings were made., Results: The aphakic eye was 1.7 mm shorter than the unmanipulated fellow eye in the monkey undergoing surgery at 4 days of age and 1.1 mm shorter in the monkey undergoing surgery at 2 weeks of age. However, the aphakic eyes were only 0.2 mm and 0.1 mm shorter than their unmanipulated fellow eyes, respectively, in the monkeys undergoing surgery at 7.5 months and 1 year of age., Conclusions: The retardation of axial elongation following a lensectomy in infantile monkey eyes is age dependent. Little effect is observed in monkeys aged 7.5 months or older.

Objective: To study the effects of exposed ocular surface area and blink rate on tear dynamics by the measurement of tear evaporation under a range of conditions., Methods: Tear evaporation was measured in three gaze positions in 15 normal volunteers, and the ocular surface area was determined as a function of the width of the palpebral fissure. In 17 normal volunteers, the effect of blink rate on tear evaporation was assessed., Results: The ocular surface area was 1.2 +/- 0.27, 2.2 +/- 0.39, and 3.0 +/- 0.33 cm2 with patients looking down, ahead, and up, respectively. The corresponding tear evaporation rates per eye were 7.0 +/- 3.5, 17.6 +/- 6.6, and 23.7 +/- 6.3 x 10(-7) g/s, respectively. The tear evaporation per square meter also increased proportionally with the ocular surface area. When the blink rate was changed from 10 to 60 per minute, the tear evaporation did not change in those individuals with evaporation rates more than 7.8 x 10(-7) g/s per square centimeter, whereas it did increase with the blink rate in those whose evaporation rates were lower., Conclusions: Ocular surface area and blink rate affect tear dynamics. Moderate palpebral fissure width and blink rate are necessary for the prevention of desiccation of the ocular surface.

Objective: We investigated the effect of scleral reinforcement on ocular elongation in the rapidly growing eyes of juvenile cats., Methods: Bands made from donor sclera or expanded polytetrafluoroethylene were used to reinforce one eye of each animal; contralateral eyes underwent sham surgery., Results: During 5 months of follow-up, normal intraocular pressures implied normal functioning of angle structures. A-scan on the central axis showed no difference in globe lengths. Direct physical measurements of the posterior aspect of the globe at enucleation revealed significant decreases in off-center lengthening where reinforcement was present compared with unreinforced areas in the same eyes and in the contralateral unbanded eyes. Venous beading in fundus photographs of three eyes suggested impairment of venous outflow., Conclusions: Scleral reinforcement appears to control expansion of the growing cat eye to a limited extent, but the effects on vision and retinal perfusion require further investigation.

Eleven normal women, between the ages of 19 and 28, were examined at the same time of day, every day of a complete menstrual cycle. Measurements of intraocular pressure, anterior chamber depth, corneal thickness, and tear production were obtained. Tonographic values were obtained on eight days during the cycle. The results for ten of the women who were shown to have ovulated during the study, were then correlated with daily blood levels of luteinizing hormone, follicle-stimulating hormone, estrone, estradiol, progesterone, and testosterone, as measured by techniques of radioimmunoassay. No statistically valid correlations could be made when the various studies were analyzed and correlated.

Elongation of the eye is one of the drawbacks of implanting intraocular lenses in children. To evaluate possible effects of cataract and aphakia on eye elongation, we measured the axial length in children with unilateral aphakia (15 children with congenital cataract and 27 with traumatic cataract) and in children with bilateral congenital cataract (operated on in 14 cases and not operated on in eight cases). In all cases of unilateral aphakia, the aphakic eye was consistently longer than the normal fellow eye. Excessive eye elongation was related to corresponding reduction in visual acuity. The presumed rate of elongation was quantitatively expressed using the time elapsed since surgery and the age of the child. In bilateral congenital cataract, the axial length measured in aphakic eyes that were operated on was similar to that in eyes that were not operated on. We suggest that unilateral cataract or aphakia is associated with excessive eye elongation of affected eyes. Eye elongation seems to be related to amblyopia and poor vision rather than to aphakia.

A review of the literature was made to evaluate the prediction accuracy of intraocular lens calculations. A uniform standard formula (percentage +/- 1.0 diopter/percentage +/- 2.0 D/range of error) for reporting accuracy was used to evaluate the accuracy of reports in the literature, as well as the accuracy of an ultrasound unit (Kretz 7100 MA), the HOffer formula, use of a standard 3.5-mm anterior chamber depth, and addition of a retinal thickness factor to the measured ultrasound axial length. The appropriateness of technicians performing this procedure also was evaluated. Results of previous studies show that the use of another ultrasound unit (Sonometrics DBR) and Binkhorst's formula is the least clinically accurate method.

Thirty-three eyes of 18 normal infants and children and 36 eyes of infants in whom congenital glaucoma had been diagnosed were measured by echometry. The anterior chamber depth, vitreous length, and axial length were notably greater in glaucomatous eyes, while the lens thickness was smaller in glaucomatous eyes. The axial length of normal eyes was found to increase with age. The confidence interval of the normal growth curve allows the prediction of the maximum normal axial length for any given age. In congenital glaucoma cases in which the visual fields and daily pressure curve cannot be evaluated, clinical echometry is proposed as a valuable diagnostic and follow-up procedure.

Transscleral cyclophotocoagulation was performed with a neodymium-YAG laser in the free-running mode (20-ms pulses) on eight human autopsy eyes. Variables studied were laser beam position and angle, defocusing, and pulse energy. Based on gross and histologic evaluation of the treated eyes, a tangential beam placed 1.0 to 1.5 mm behind the limbus, with maximum defocusing and an energy setting of approximately 8 J, appears to provide the optimum probability of damaging the ciliary processes.

Forty-eight patients with Graves' eye disease, half of whom had extraocular muscle restriction, and 45 normal adult subjects underwent exophthalmometry while in the upright and the supine positions to determine whether the difference in measurement due to position would serve to differentiate the groups. A previous report claimed that the upright reading would be greater than the supine reading for normal subjects and patients with Graves' eye disease without clinical extraocular muscle involvement, whereas those with extraocular muscle restriction would show little change in their exophthalmometer readings. Our study showed an increase in exophthalmometer readings in going from the upright to the supine position for normal subjects and both groups of patients with Graves' eye disease. Furthermore, this test did not serve to differentiate these three groups.

Radial retinal folding, associated with equatorial scleral buckling, contributes to the difficulty in repairing a retinal detachment due to a fishmouth break. To minimize this effect, a wedge-shaped implant was designed to approximate more closely the same relative reduction in the circumference of the circles of the globe along the meridian of the break. The surgical details of use of the implant are described. In a consecutive series of 56 eyes in which the fishmouth phenomenon was expected, 49 (88%) were successfully managed at first encounter using a wedge buckling device. Revised scleral bucklings and open-sky vitrectomies, in early failures and delayed recurrences, salvaged additional eyes for final success in 52 (93%) of the eyes.