Anterior Segment Depth Research Articles

Prevalence and prediction of intraoperative floppy iris syndrome in patients with pseudoexfoliation syndrome

ObjectiveTo investigate the incidence of intraoperative floppy iris syndrome (IFIS) in patients with pseudoexfoliation syndrome (PXF) and analyze preoperative ocular predicting factors. DesignA retrospective case-control study MethodsThe study included 224 eyes with PXF and 287 control eyes without PXF. One eye per patient, who underwent cataract surgery at the Wolfson Medical Center between January 2020 to December 2021, was included. Medical records of the patients were reviewed. Data collected included demographic characteristics, medical history, preoperative comprehensive ophthalmic examination, biometry, surgical procedure details, and IFIS occurrence. The association of IFIS with preoperative ocular parameters was analyzed through both univariant and multivariant analyses. ResultsPatients with PXF were older and had a higher prevalence of glaucoma (77.6 ± 6.4 years vs 74.2±7.6 years; p < 0.001, and 20.1 % vs 9.8 %, p < 0.001, respectively). Prevalence of α-blockers treatment was similar in both groups. IFIS rate among the PXF group was 12.5% (n = 28) compared to 7.3% (n = 21) in the control group (p < 0.05). When omitting patients exposed to α-blockers, the PXF group exhibited a significantly higher IFIS rate (9.9% vs 4.8%; p < 0.05). Pupil dilation diameter was significantly lower among PXF patients (5.8 ± 1.1 mm vs 6.9 ± 0.99 mm; p < 0.001). Biometric evaluation revealed significant differences in anterior segment depth (ACD) and lens thickness (LT). Multivariate analysis indicated that PXF and decreased mydriatic pupil size remained significant predictors of IFIS. ConclusionThis study establishes an association between PXF and an increased risk of IFIS during cataract surgery, independent of α-blockers treatment.

The Effect of Anterior Segment Depth on the Accuracy of 7 Different Intraocular Lens Calculation Formulas.

Objectives:To evaluate the effect of anterior segment depth (ASD; sum of anterior chamber depth and lens thickness) on the accuracy of 7 intraocular lens formulas calculated in patients with axial length (AL) between 22.5 and 24.5 mm.Materials and Methods:In this retrospective study, patients who underwent cataract surgery were divided into three groups based on their ASD measurements (Group I: ASD <7.30 mm, Group II: ASD between 7.30-7.90 mm, Group III: ASD >7.90 mm). The mean predictive error (MPE), mean absolute error (MAE), and median absolute error (MedAE) values of each group were compared. The effect of ASD on the predictive error (PE) of each lens formula was additionally tested in subgroups based on mean keratometry (K) values (Subgroup I: K <42.0 D, Subgroup II: K between 42.0-44.5 D, Subgroup III: K >44.5 D).Results:The study included 184 eyes of 184 patients. In Group I, all formulas except Olsen OLCR and Barrett II had clinically myopic MPEs. In Group II, the MPEs of all lens formulas except Barrett II were statistically non-different from zero (p>0.05). In Group III, the MPEs of all lens formulas were found to be statistically hyperopic. In Group III, all formulas except Olsen OLCR were significantly shifted to more hyperopic results when compared with Groups I and II (p<0.05). ASD was positively correlated with the PEs of the SRK/T, Holladay I, Hoffer Q, Barrett II, Hill-RBF, and Haigis formulas. In cases with mean K greater than 42.0 D, ASD was similarly correlated with PE for all formulas except Olsen OLCR.Conclusion:In eyes with AL between 22.5 and 24.5 mm, the predictions of lens formulas were significantly hyperopic in cases with greater ASD.

Anterior Ocular Biometrics as Measured by Ultrasound Biomicroscopy.

Background: High frequency ultrasonography (ultrasound biomicroscopy; UBM) is an ophthalmic diagnostic tool that can be used to measure the depth of the anterior segment (ASD), the anterior chamber angle (ACA), as well as thicknesses of the iris and the ciliary body (CB). Methods: The anterior segment dimensions and thicknesses were measured by Sonomed 35-MHz. Results: Measurements for 95 eyes from 52 adults were analyzed. The mean and median ASD and ACA were 2.91, 2.92 ± 0.41 mm and 34.1, 34.3 ± 12.1 degrees, respectively. The angle superiorly was wider than inferiorly (p = 0.04). At the root of the iris, the mid of the iris, and the juxtapupillary edge of the iris, the iris thicknesses (median, mean) were 0.40, 0.41 ± 0.1, 0.50, 0.51 ± 0.1, and 0.70, 0.71 ± 0.1 mm, respectively. The thicknesses of CB and CB together with the ciliary processes (median, mean), were 0.70, 0.71 ± 0.15 mm and 1.36, 1.41 ± 0.15 mm, respectively. The upper quadrant of both the iris and the CB was significantly thicker than the lower quadrant (p = 0.04). Conclusions: Our biometric measurements for the anterior segment can be used as normative data for anterior segment depth and angle and iris and ciliary body thickness in normal eyes.

Correlation of vitreous chamber depth with ocular biometry in high axial myopia.

Purpose:The proportion of axial length (AL) occupied by vitreous chamber depth (VCD), or VCD:AL, consistently correlates to ocular biometry in the general population. Relation of VCD:AL to ocular biometry in high myopia is not known. The purpose of this study is to evaluate the relation of VCD and VCD:AL to ocular biometry of highly myopic eyes.Methods:This was a cross-sectional retrospective study of records of 214 myopic eyes (<−1 D SE, aged 20–40 years) attending the refractive surgery services. High axial myopia was defined as AL >26.5 mm. Eyes with posterior staphyloma and myopic maculopathy were excluded. Records were assessed for measurements of AL, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), white to white diameter (WTW), and vitreous chamber depth (VCD). Groups were formed based on increasing AL, while the sum of CCT, ACD, and LT was recorded as anterior segment depth (AS). The main outcome measure was the correlation of VCD and VCD:AL to ocular biometry. A comparison was also performed based on of degree of axial myopia.Results:Mean age of the patients was 27.0 ± 5.2 years. VCD showed a very strong correlation with AL (R = 0.98, P < 0.001) but did not correlate to any anterior parameter. VCD:AL showed moderate negative relation with AS (R = −0.43, P < 0.001) and ACD (R = −0.3, P < 0.001), while it had a weakly negative relation with LT (R = −0.18, P = 0.006). VCD:AL showed strong negative relation (R > ~0.7) with AS in all individual groups of AL. Among anterior parameters, WTW showed the most consistent relation with ocular biometry.Conclusion:VCD:AL is a better correlate of ocular biometry in high myopia as compared to VCD. However, the correlation is weaker than that noted by previous studies done on the general population. Longitudinal studies of VCD:AL in the younger age group is recommended.

Alterações oculares precoces após aplicação de compressas frias

To examine changes in the eyes after cold compress application at the early stage. A total of 62 eyes from 62 healthy adult participants were included in this cross-sectional and comparative study. The subfoveal choroidal thickness and retinal nerve fiber thickness were measured by spectral-domain ocular coherence tomography. The central corneal thickness, anterior segment volume and depth, iridocorneal angle, and pupil diameter were measured by means of the Scheimpflug anterior segment imaging method. The measurements were repeated after 10 min of cold compress application, which was applied using special packs. The procedures were then repeated with non-cold packages to exclude the effect of pressure. The average age of the participants was 30.74 ± 5.82 years. There was no significant change in the central corneal thickness after cold compress application, and there was a significant decrease in the anterior segment volume (p<0.001), anterior segment depth (p<0.001), and pupil diameter. Moreover, the iridocorneal angle increased (p=0.002). The subfoveal choroidal thickness decreased after the application of cold compress (p<0.001). The overall disk thickness (p=0.034) and superior nasal scale (p=0.007) significantly decreased after the cold compress was administered during the evaluation of optic nerve fiber thickness. In contrast to that with the cold application, the subfoveal choroidal thickness and optic nerve fiber thickness did not change after the non-cold compress application (p>0.05). Cold compress application may thus cause some physiological changes in the eyes, which necessitates the examination of its usage and effects.

Comparison of A-Scan ultrasonography and the Lenstar optical biometer in Guinea pig eyes

ObjectiveTo compare the biometric parameters provided by A-scan ultrasonography and the Lenstar optical biometer in guinea pig eyes, including anterior segment depth (ASD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL), and differences of them between treated form deprivation (FD) eyes and untreated fellow eyes after 4 weeks of FD. MethodsThree-week-old guinea pigs (N = 41) were subjected to biometric measurements before monocular FD (baseline) and after a 4-week FD. Statistical analyses including within-subject standard deviation (SDwithin), coefficient of variation (CV), and intraclass correlation coefficient (ICC), used to evaluate repeatability for both the A-scan ultrasonography and the Lenstar individually, and correlation and Bland-Altman analyses were used to assess agreement between the two methods. The absolute values of ASD, LT, VCD and AL as measured by the two devices were compared, and the differences of them between treated (T) and untreated fellow (F) eyes (ΔASD, ΔLT, ΔVCD and ΔAL) (Δ = T-F) were compared between the two devices after 4 weeks of FD. ResultsMeasurements by the Lenstar (ICC: 0.923–0.994) were more repeatable than A-scan ultrasonography (ICC: 0.825–0.870). There was a high correlation for AL (r = 0.851, P < 0.001), a moderate correlation for VCD (r = 0.571, P < 0.001) and LT (r = 0.423, P < 0.001), and a low correlation for ASD (r = 0.230, P < 0.01) between the two devices. The values for ASD, VCD and AL measured by A-scan ultrasonography were larger than those measured by the Lenstar (all, P < 0.001), while LT provided by A-scan ultrasonography was much smaller than that of the Lenstar (P < 0.001). Bland-Altman plots showed poor agreement of absolute values of the four parameters between the two devices. Moreover, there was a high correlation between both methods for ΔAL (r = 0.704, P < 0.001), a moderate correlation for ΔVCD (r = 0.534, P < 0.001) and ΔASD (r = 0.574, P < 0.001), and no correlation for ΔLT (r = 0.303, P = 0.054). The ΔASD, ΔLT, and ΔAL measurements obtained by A-scan ultrasonography were greater than those obtained by the Lenstar (all, P < 0.001), while ΔVCD was mildly smaller using A-scan ultrasonography (P < 0.05). Bland-Altman plots illustrated there is good agreement of ΔAL, ΔVCD, ΔASD, and ΔLT between the two devices. ConclusionsThe Lenstar exhibited better repeatability and provided smaller measurements for AL, VCD and ASD than A-scan ultrasonography. Furthermore, a high correlation and a good agreement for the ΔAL was observed between the two devices after a period of FD. In summary, the two devices cannot replace each other directly to obtain absolute values of ASD, LT, VCD and AL, but the Lenstar still can serve as an option in measuring ΔAL between eyes in guinea pig myopia model.

WITHDRAWN: Intelligent microscopy to improve cataract surgery

Abstract Phacoemulsification is the most performed surgery in the world. Over the past few years, evidence emerged about the use of artificial intelligence (AI) in cataract surgery video analysis for phase classification and instrument identification. Herein, we propose the use of AI to analyze intraoperative images captured by a surgical microscope to improve the fluidic of the phacoemulsification device. The principle is to develop an AI algorithm for recognizing anterior chamber movements by real-time automated analysis of microscope captured images. When AI recognizes an aspect of the anterior chamber which begins to be emptied, it sends a signal to the fluidic system to adjust the anterior segment depth. We believe that this technique could improve surgery security.

Effects of Monocular Atropinization on Refractive Error and Eye Growth in Infant New World Monkeys.

To explore the effect of topical atropine on axial eye growth and emmetropization in infant marmosets. Atropine was applied to one eye from the age of 7 to 56 days in two dose regimens, High (0.1-1% twice daily, increasing with age) or moderate (Mod) (0.1% once daily). Both eyes of the marmosets were refracted, and axial dimensions were measured ultrasonically, at 14, 28, 42, 49, 56, 70, 105, 168, and 279 days of age. The time course of each measured variable was analyzed using multilevel mixed-effects modeling realized in R. The logistic growth curves fitted to anterior segment depth (ASD) did not differ significantly between the dose regimens, but xmid, the age at which growth was half-maximal, and scal, the time constant of the exponential term in the logistic growth curve equation, differed significantly between the ASD of atropinized and untreated eyes (P = 0.03 and P < 0.0001, respectively), with the ASD of atropinized eyes shorter than that of untreated eyes. The splines fitted to lens thickness did not vary significantly with dose, but differed significantly (P < 0.0001) between the atropinized and untreated eyes, with the atropinized lenses thicker. Vitreous chamber depth (VCD) was not significantly different, but the variance of VCD was significantly greater (P < 0.001) in the atropinized compared with the untreated eyes. Refractive error (RE) became relatively myopic in atropinized eyes. The variance of RE in atropinized eyes was significantly greater (P < 0.0001) than in untreated eyes. Atropine caused the infant marmoset lens to move forward and thicken, a relative myopia, and increases in the between-animals variance in VCD, which could be considered a failure of emmetropization.

Matching the LenStar optical biometer to A-Scan ultrasonography for use in small animal eyes with application to tree shrews

We describe an analysis strategy to obtain ultrasonography-matched axial dimensions of small animal eyes using the LenStar biometer. The LenStar optical low-coherence reflectometer is an attractive device for animal research due to its high precision, non-invasiveness, and the ability to measure the axial dimensions of cornea, anterior chamber, lens, vitreous chamber, and axial length. However, this optical biometer was designed for clinical applications in human eyes and its internal analysis provides inaccurate values when used on small eyes due to species-dependent differences in refractive indices and relative axial dimensions. The LenStar uses a near infrared light source to measure optical path lengths (OPLs) that are converted by the LenStar's EyeSuite software into geometrical lengths (GLs) based on the refractive indices and axial dimensions of the human eye. We present a strategy that extracts the OPLs, determines refractive indices specific for the small animal eye of interest and then calculates corrected GLs. The refractive indices are obtained by matching the LenStar values to ultrasonography values in the same eyes. As compared to ultrasounography, we found that the internal calculations of the LenStar underestimate the axial dimensions of all ocular compartments of the tree shrew eye: anterior segment depth by 6.17±4.50%, lens thickness by 1.37±3.06%, vitreous chamber depth by 29.23±2.35%, and axial length by 10.62±1.75%. Using tree shrew-specific refractive indices, the axial dimensions closely matched those measured by ultrasonography for each compartment. Our analysis strategy can be easily translated to other species by obtaining a similar paired data set using ultrasonography and LenStar, and applying our step by step procedures.

Clinical and biometric determinants of actual lens position after cataract surgery

To evaluate the preoperative clinical and biometric determinants associated with the actual lens position after cataract surgery. Department of Ophthalmology, University Hospital of Montpellier, France. Prospective longitudinal cohort study. The data collected included clinical factors (age, sex, history of vitrectomy) and biometry factors (axial length [AL], anterior chamber depth [ACD], lens thickness, white-to-white [WTW] distance) that might affect actual lens position. Each patient had optical low-coherence reflectometry biometry (Lenstar) preoperatively and 1month postoperatively. The actual lens position was measured as the postoperative position of the center of the intraocular lens (IOL). Patients were stratified into 3 groups by type of IOL: Acrysof SN60WF or SN6AT (Group 1), Tecnis ZCB00 or ZCT (Group 2), and Asphina 409MV (Group 3). The study comprised 168 eyes (mean age 73.3years±9.8 [SD]). The mean actual lens position was 4.88±0.29mm, 5.01±0.29mm, and 5.05±0.32mm in Group 1 (n=67 eyes), Group 2 (n=52 eyes), and Group 3 (n=49 eyes), respectively. In the overall population, AL, ACD, anterior segment depth, and WTW distance were correlated with actual lens position (r=0.48, P<.0001; r=0.64, P<.001; r=0.58, P<.0001; r=0.39, P<.001, respectively). The AL, ACD, anterior segment depth, and WTW distance correlated with actual lens position after cataract surgery. The integration of these data in IOL formulas could help improve refractive outcomes after the surgery.

Baseline assessment of ophthalmic parameters in the greater one-horned rhinoceros (Rhinoceros unicornis).

Five healthy captive greater one-horned rhinoceroses (Rhinoceros unicornis) were evaluated with standing sedation (detomidine hydrochloride 20-30 mg and butorphanol tartrate 50-60 mg per animal) to determine baseline values for tear production, intraocular pressure (IOP), conjunctival flora, and ocular anatomy using brightness mode transpalpebral ultrasonography with a 4- to 7-MHz broadband curvilinear transducer. The mean Schirmer tear test I value was 18.2 ± 3.49 mm/min. The mean IOP measured using applantation tonometry was 31.2 ± 6.62 mm Hg. Ocular biometry measurements were the following: axial length 2.61 ± 0.11 cm; corneal thickness 0.13 ± 0.01 cm; anterior segment depth 0.28 ± 0.06 cm; lens depth 0.70 ± 0.11 cm; and posterior segment depth 1.46 ± 0.13 cm. These values indicate that the globe is smaller than that of the domestic horse. All eight conjunctival swabs cultured bacterial and fungal microorganisms, with the most common being Staphylococcus spp. (57%). All bacterial isolates were considered to be commensal organisms due to the presence of mixed bacterial populations and lack of clinical signs of ocular disease. The data collected in this study should provide veterinarians with baseline information to assist in the diagnosis of ophthalmic conditions in the greater one-horned rhinoceros.

Three-dimensional anterior segment imaging in patients with type 1 Boston Keratoprosthesis with switchable full depth range swept source optical coherence tomography

A high-speed (100 kHz A-scans/s) complex conjugate resolved 1 μm swept source optical coherence tomography (SS-OCT) system using coherence revival of the light source is suitable for dense three-dimensional (3-D) imaging of the anterior segment. The short acquisition time helps to minimize the influence of motion artifacts. The extended depth range of the SS-OCT system allows topographic analysis of clinically relevant images of the entire depth of the anterior segment of the eye. Patients with the type 1 Boston Keratoprosthesis (KPro) require evaluation of the full anterior segment depth. Current commercially available OCT systems are not suitable for this application due to limited acquisition speed, resolution, and axial imaging range. Moreover, most commonly used research grade and some clinical OCT systems implement a commercially available SS (Axsun) that offers only 3.7 mm imaging range (in air) in its standard configuration. We describe implementation of a common swept laser with built-in k-clock to allow phase stable imaging in both low range and high range, 3.7 and 11.5 mm in air, respectively, without the need to build an external MZI k-clock. As a result, 3-D morphology of the KPro position with respect to the surrounding tissue could be investigated in vivo both at high resolution and with large depth range to achieve noninvasive and precise evaluation of success of the surgical procedure.

MRI study of the changes in crystalline lens shape with accommodation and aging in humans

Magnetic Resonance Imaging was used to study changes in the crystalline lens and ciliary body with accommodation and aging. Monocular images were obtained in 15 young (19-29 years) and 15 older (60-70 years) emmetropes when viewing at far (6 m) and at individual near points (14.5 to 20.9 cm) in the younger group. With accommodation, lens thickness increased (mean ± 95% CI: 0.33 ± 0.06 mm) by a similar magnitude to the decrease in anterior chamber depth (0.31 ± 0.07 mm) and equatorial diameter (0.32 ± 0.04 mm) with a decrease in the radius of curvature of the posterior lens surface (0.58 ± 0.30 mm). Anterior lens surface shape could not be determined due to the overlapping region with the iris. Ciliary ring diameter decreased (0.44 ± 0.17 mm) with no decrease in circumlental space or forward ciliary body movement. With aging, lens thickness increased (mean ± 95% CI: 0.97 ± 0.24 mm) similar in magnitude to the sum of the decrease in anterior chamber depth (0.45 ± 0.21 mm) and increase in anterior segment depth (0.52 ± 0.23 mm). Equatorial lens diameter increased (0.28 ± 0.23 mm) with no change in the posterior lens surface radius of curvature. Ciliary ring diameter decreased (0.57 ± 0.41 mm) with reduced circumlental space (0.43 ± 0.15 mm) and no forward ciliary body movement. Accommodative changes support the Helmholtz theory of accommodation including an increase in posterior lens surface curvature. Certain aspects of aging changes mimic accommodation.

Ultrasonographic Anatomy of the Asian Elephant (Elephas maximus) Eye

Bilateral transpalpebral ultrasonography was performed on 53 captive Asian elephants (Elephas maximus) in order to describe the normal ultrasonographic appearance and measurements of the Asian elephant eye. Transpalpebral ultrasonography was performed using a portable ultrasound unit and a 4-7-MHz broadband curvilinear transducer on animals housed at seven institutions in the United Kingdom and in Sri Lanka. Both males and females were included in the study and ages ranged from 14 mo to 65 yr. Ultrasonic examinations were conducted on unsedated animals, without the use of topical or local anesthesia. The ultrasonographic appearance of the globe and intraocular structures of the Asian elephant eye is similar to that in other species. Biometry measurements recorded for adult (n=41) and juvenile (n=10) Asian elephants were: axial length, 3.44 +/- 0.21 cm and 3.18 +/- 0.19 cm (mean +/- SD); equatorial diameter, 3.88 +/- 0.32 cm and 3.60 +/- 0.24 cm; corneal thickness, 0.17 +/- 0.02 cm and 0.16 +/- 0.02 cm; anterior segment depth, 0.45 +/- 0.08 cm and 0.36 +/- 0.07 cm; lens diameter, 1.90 +/- 0.14 cm and 1.75 +/- 0.19 cm; lens depth, 1.01 +/- 0.12 cm and 0.94 +/- 0.10 cm, and posterior segment depth, 1.82 +/- 0.17 cm and 1.72 +/- 0.15 cm, respectively. Multiple linear regression analysis indicated a significant relationship between the explanatory variables (age, sex, and height) and the dependent variables (axial length, equatorial diameter, corneal thickness, anterior segment depth, lens diameter, and lens depth). The main finding of this statistical test was that the globe increases in size as the animal ages. Transpalpebral ultrasonography was found to be an effective and practical imaging modality in the evaluation of the Asian elephant eye, without the need for chemical restraint.

High-Frequency Ultrasound Biomicroscopy of the Anterior Segment Morphometry before and Immediately after Pars Plana Vitrectomy

To characterize short-term changes induced by pars plana vitrectomy on anterior segment depth and lens thickness by means of high-frequency ultrasound biomicroscopy. We undertook a prospective case series study on consecutive patients referred for pars plana vitrectomy as the sole procedure in our institution between 2005 and 2007. Twenty-eight eyes of 28 patients undergoing pars plana vitrectomy were studied by ultrasound biomicroscopy. Neither silicone oil nor scleral buckle was used for any of the procedures. Anterior chamber depth and lens thickness were compared before and immediately after surgery, and their results were compared to the postoperative intraocular pressure measurements. There was a significant decrease in anterior chamber depth in the study eyes of patients who had undergone gas tamponade (p<0.0001) but not in those who had not undergone gas tamponade. No differences were found between the preoperative and the postoperative lens thickness measurements in any of the patients, nor was there any correlation between anterior chamber depth and increased intraocular pressure. Uncomplicated pars plana vitrectomy with gas tamponade can induce short-term changes in anterior chamber depth as measured by morphometry. Surgeons may need to reconsider using gas tamponade at the end of surgery in surgical candidates with shallow anterior chambers.

Comparison of corneal thickness, anterior segment depth and pupil diameter between patients with neovascular age‐related macular degeneration and controls

Abstract Purpose The goal of this study was firstly to compare corneal thickness at four different locations, anterior depth and pupil diameter between patients with neovascular age‐related macular degeneration and healthy individuals and secondly, to find out any possible anterior segment related risk factor for AMD development. Methods In this prospective study 69 patients (119 eyes) with neovascular age‐related macular degeneration with no history of any ocular disease or surgery were included. The 31 controls (56 eyes) were also enrolled. Informed consent was obtained from all recruited individuals. Each subject underwent complete ophthalmic examination. Galilei Dual Scheimpflug Analyzer (version 3.0, Ziemer Ophthalmic Systems AG, Switzerland), a non‐invasive diagnostic system designed for analysis of anterior chamber of the eye, was used for anterior segment evaluation. Results Comparison of corneal thickness at central, paracentral, peripheral zone and at the thinnest point revealed no statistically important difference between patients with age‐related macular degeneration and controls (P&lt;0,5). There was a statistically significant difference in the mean anterior chamber depth between both groups (P=0,002). We did not observe statistically important difference in pupil diameter between both group (P&gt;0,5). Conclusion The results of our study confirmed that the corneal thickness and pupil diameter are not associated with age‐related macular degeneration. Further investigations are necessary to confirm our results and to find out a possible role of anterior chamber depth as an additional risk factor for AMD development.

Age-related changes in optical and biometric characteristics of emmetropic eyes

We measured optical and biometric parameters of emmetropic eyes as a function of age. There were approximately 20 subjects each in age groups 18-29, 30-39, 40-49, 50-59, and 60-69 years with similar male and female numbers. One eye was tested for each subject, having spherical equivalent in the range -0.88 D to +0.75 D and <or=0.50 D astigmatism. Despite considerable data scatter, we found significant age changes: anterior chamber depth decreased 0.011 mm/year, lens central thickness increased 0.024 mm/year, anterior segment depth increased 0.013 mm/year, eye length increased 0.011 mm/year, anterior lens radius of curvature decreased 0.044 mm/year, and lens equivalent refractive index decreased 0.0003/year. Males had higher anterior corneal radii of curvature (0.16 mm), lower lens equivalent refractive index (0.006), longer vitreous lengths (0.51 mm), and longer axial lengths (0.62 mm) than females. Superficially, the results suggest that eyes get bigger as they age. However, results can be related to refraction patterns in which refraction is stable in 20s to 40s and then moves in the hypermetropic direction. It is likely that several young subjects will become hypermetropic as they age, and it is possible that some of the older subjects were myopic when younger.

High Myopia Associated With Retinopathy of Prematurity Is Primarily Lenticular

To determine which of the eye's refractive components are responsible for the high myopia in retinopathy of prematurity (ROP), as compared with highly myopic eyes in full-term patients. The study included 53 highly myopic eyes in 34 patients with a history of ROP, and 66 highly myopic eyes in 37 full-term patients. Measurements included refraction, keratometry, and A-scan values for axial length, lens thickness, lens position, anterior chamber depth, anterior segment depth, and lens power calculations. Comparisons were also made with published age-matched, full-term normal controls. Refractions ranged from a spherical-equivalent of -5.0 to -20.75, and from -5.0 to -22.0 diopters in ROP and full-term eyes, respectively. For ROP eyes, increasing myopia was most associated with lens thickness and lens power ( P < 0.001), with lesser contributions from corneal steepness, axial length, and a more forward position of the lens's center. For the eyes with myopia in full-term patients, increasing myopia was highly associated with axial length ( P < 0.001), with smaller contributions from increased lens thickness and lens power. ROP eyes had a lens-thickness/anterior-chamber-depth ratio almost 50% higher than FT and normative eyes. Anterior segment depth was remarkably similar in all eyes studied. High myopia associated with ROP appears pathophysiologically distinct from high myopia in full-term patients. The increased lens thickness seen in ROP eyes was accompanied by shallower anterior chamber depth and maintenance of the anterior segment depth, similar to the normal neonatal eye, suggesting a mechanism of altered anterior segment development in ROP leading to high myopia.

Normal development of refractive state and ocular component dimensions in the marmoset ( Callithrix jacchus)

Refractive state and ocular dimensions were studied longitudinally in nine normal marmosets. Animals were anaesthetised and examined (with some exceptions) at 4, 6, 7, 8, 10, 15, 24 and 39 weeks of age. Cycloplegic retinoscopy showed that hyperopia early in life rapidly diminished. Refraction corrected for the artefact of retinoscopy stabilised by 8 weeks of age, but at a slightly myopic value, rather than at emmetropia. The ocular components continued to change throughout the period studied. Corneal radius, measured by photokeratometry, increased slightly during development. Anterior segment depth and vitreous chamber depth (VCD), measured by A-scan ultrasonography, increased throughout development while lens thickness initially increased and then decreased. Data from the eyes of these normal animals were compared with that from the contralateral eyes of animals which received short periods of monocular deprivation early in life (Troilo, D., & Judge S.J. (1993). Ocular development and visual deprivation myopia in the common marmoset ( Callithrix jacchus jacchus). Vision Research, 33, 1311–24)); eyes which viewed through no lens or a plano lens (Graham, B. & Judge, S.J. (1999). The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset ( Callithrix jacchus). Vision Research, 39, 189–206), and eyes of normal animals in another colony. There were no significant differences between the first two groups and the normal animals in our colony while age-matched animals from the other colony were slightly but significantly less myopic than our animals.

Dynamic relationships of the mandibular anterior segment

The hyperbolic cosine function is shown to be an accurate representation of the form of the mandibular anterior teeth from the canine/first premolar contact on one side around the perimeter to the opposite side ( r = 0.951). On the basis of this mathematical function, the changes in canine width, anterior segment depth, arch perimeter, and their related incisor angular alterations are forecastable. This knowledge will allow the clinician to predict the effects on various aspects of the anterior segment arch form as one or more of these variables are altered without resorting to trial and error or performing a wax-up. For example, the clinician can predict the change in the anterior segment arch depth and incisor angulation that would occur with alterations in canine width. (Am J Orthod Dentofac Orthop 1997;111:518-24.)