The diameter of the ciliary sulcus: a morphometric study

Endoscopy-guided in vivo evaluation of ciliary sulcus location in children with ectopia lentis

OBJECTIVE

To assess a new method to measure the distance of the needle passage from the ciliary sulcus to the corneal limbus anterior border (CTC) in eyes with ectopia lentis directly in vivo via endoscopy and to further evaluate the correlations among the CTC, age, automated horizontal white-to-white distance (WTW), and ocular axial length (AL).

METHODS

The WTW and AL were measured using an optical biometer. An intraocular endoscope was used during transscleral suture fixation of posterior chamber intraocular lenses to identify the true location of the ciliary sulcus. Linear regression analysis was used to assess the correlation between the CTC and other ocular biological parameters, including age, WTW, and AL.

RESULTS

Thirty eyes of 30 children with ectopia lentis were evaluated. A statistically significant correlation was found between age and the CTC. The CTC could be predicted by the equation CTC = 0.1313 × Age + 0.9666. No statistically significant correlations were found between CTC and WTW, CTC and AL, WTW and AL, or WTW and age.

CONCLUSION

Endoscopy is useful for precisely suturing intraocular lens haptics in the real ciliary sulcus. Age can be used as an equivalent parameter for prediction of the true ciliary sulcus location.

Phakic intraocular lens: Getting the right size

Phakic intraocular lenses (IOL) are a boon for patients who want spectacle independence but are unable to get refractive correction through laser platforms due to high refractive error or certain corneal contraindications. Phakic IOL's (PIOL) have their own set of complications and challenges, the most important being getting the sizing right. This paper attempts to solve the problem of accurate sizing of PIOL's. Parameters needed for calculating the ideal size of PIOL's have been studied in a step by step manner using all possible tools depending upon the availability and preference of the surgeon. The pros and cons of using a particular tool for measurements have been highlighted along with illustrative case examples to help surgeons who are starting PIOL implantation surgery.

Multivariate Analysis to Predict the Horizontal Anterior Chamber Diameter from Other Anterior Chamber Parameters Using Scheimpflug Imaging: Is There a Better Method Than Adding a Fixed Constant?

PURPOSE

To evaluate the predictive association between the horizontal anterior chamber diameter (HACD) and other measurements using Scheimpflug imaging, and to assess whether a method superior to using fixed constants can be proposed.

METHODS

This hospital-based study was performed in the Cornea and Refractive Surgery Services, New Medical Center (NMC) specialty hospital, Abu Dhabi. Initially, 100 candidates were included serially in the model building group (group1). All candidates underwent detailed evaluation and Scheimpflug imaging (CSO, Sirus, Italy). Subsequently, another 100 candidates were included serially in the validation group (group 2). Candidates in both groups underwent the same tests.

RESULTS

In group 1, the mean HACD was 12.25 ± 0.48 mm. This measurement correlated significantly with the horizontal visible iris diameter (HVID), anterior chamber depth, angle (ACA), and volume (ACV) (r = 0.2-0.7). The overall regression equation was HACD = 5.62 + 0.01 × ACV + 0.45 × HVID - 0.013 × ACA (adjusted R² = 0.66, p < 0.001). Situation-based equations derived from the outcomes of group 1 were tested in group 2. Equation A included all factors found significant during model-building, Equation B included only non-volumetric significant factors, and situation C only included the HVID. Equations D through F used direct substitution by HVID plus a constant to predict HACD (the constant was 0.0, 0.5, and 1.0 for Equations D, E, and F, respectively). The predicted HACD (pHACD) was within ±0.5 mm of the actual HACD (aHACD) in 93%, 88%, 87%, 83%, 69%, and 16% case for Equations A, B, C, D, E, and F, respectively. The mean prediction error was -0.14 ± 0.27 mm (p = 0.08), -0.15 ± 0.28 mm (p = 0.03), -0.18 ± 0.30 mm (p = 0.001), -0.18 ± 0.32 mm (p < 0.001), 0.33 ± 0.35 mm (p < 0.001), and 0.83 ± 0.35 mm (p < 0.001) for Equations A, B, C, D, E, and F, respectively.

CONCLUSION

Regression equations using Scheimpflug-derived anterior chamber parameters may predict HACD to varying degrees, depending on the input parameters. Adding 0.5 or 1.0 mm to the corneal diameter (CD) to estimate the HACD is not recommended.

Evaluation of ciliary sulcus diameter using ultrasound biomicroscopy in emmetropic eyes and myopic eyes

PURPOSE

To measure the ciliary sulcus-to-sulcus (STS) diameter in 4 axes in emmetropic and myopic eyes using ultrasound biomicroscopy (UBM) and compare the measurements with automated horizontal white-to-white (WTW) diameter measurements.

SETTING

University Eye Hospital Freiburg, Freiburg im Breisgau, Germany.

DESIGN

Evaluation of diagnostic technology.

METHODS

The STS diameter was measured at 0, 45, 90, and 135 degrees using 35 MHz UBM. The 0-degree WTW diameters were obtained using scanning-slit topography (Orbscan) and partial coherence interferometry (PCI) biometry (IOLMaster). The 0-degree STS and 90-degree STS were compared using the paired t test; the Pearson correlation was used to assess whether the 0-degree STS diameter could be predicted from the 0-degree WTW diameter.

RESULTS

The mean SE refraction was -0.48 diopter (D) ± 0.35 (SD) in emmetropic eyes and -9.55 ± 3.70 D in myopic eyes. In 35 of 37 eyes, 90-degree STS was greater than 0-degree STS. The mean 90-degree STS was 12.51 ± 0.43 mm. The mean 0-degree STS was 12.19 ± 0.47 mm (P<.01). The mean 0-degree WTW diameters were 11.73 ± 0.37 mm (scanning-slit topography) and 12.20 ± 0.42 mm (PCI biometry). The correlations were good between 0-degree STS and 0-degree WTW with PCI biometry (r(2) = 0.82) and scanning-slit topography (r(2) = 0.86) in emmetropic eyes but weak between 0-degree STS and 0-degree WTW in myopic eyes (r(2) = 0.36 and r(2) = 0.40, respectively).

CONCLUSIONS

Sulcus diameter measurements were most precise using UBM. The ciliary sulcus is vertically oval. The WTW diameter is not suitable for calculating a PC pIOL diameter, particularly in myopic eyes.

Direct measurement of the ciliary sulcus diameter by 35-megahertz ultrasound biomicroscopy

PURPOSE

To measure the ciliary sulcus diameters in 4 different axes and to determine the correlation with white-to-white distance.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Fourteen normal volunteers with no evidence of ocular disease.

METHODS

Twenty-eight eyes were scanned using a 35-megahertz (MHz) ultrasound biomicroscopy (UBM) in sequential meridional scan planes at 45 degrees increments. Horizontal white-to-white distance was measured using Orbscan IIz (Bausch & Lomb-Orbtek, Inc., Salt Lake City, UT).

MAIN OUTCOME MEASURES

Ciliary sulcus diameter, anterior chamber diameter, white-to-white distance, and coefficient of variation.

RESULTS

The coefficient of variation for 35-MHz UBM was 0.90%. The mean diameters+/-standard deviations of ciliary sulci were 11.55+/-0.38 mm at 45 degrees, 11.99+/-0.36 mm at 90 degrees, 11.54+/-0.36 mm at 135 degrees, and 11.32+/-0.40 mm at 180 degrees. In all eyes, vertical diameters were greater than horizontal diameters. The mean difference between vertical and horizontal diameters was 0.67+/-0.26 mm (range, 0.36-1.13 mm), and this was statistically significant (P<0.001). Horizontal sulcus diameters and horizontal white-to-white distances were not correlated (r = 0.006; P = 0.976).

CONCLUSIONS

The posterior chamber appears to have a vertically oval shape. The white-to-white technique is inaccurate at predicting the horizontal diameter of the ciliary sulcus. The 35-MHz UBM may provide a good means of measuring the ciliary sulcus diameter for the implantation of a posterior chamber phakic intraocular lens.

Very High Frequency Ultrasound Biometry of the Anterior and Posterior Chamber Diameter

PURPOSE

To measure the largest diameter of the anterior chamber (AC) and posterior chamber (PC) dimension and its orientation and determine the relationship with the principal keratometric meridians.

METHODS

Twenty-eight eyes of 14 subjects were scanned with high frequency (50 MHz) ultrasound in sequential meridional scan planes at 30 degrees increments. Observer identified angle and ciliary sulcus recess boundaries in each patient scan set were fit with an elliptical model to obtain the ellipse semi-major axis corresponding to the largest diameter and its meridional orientation. Anterior and posterior chamber diameters from raw data and model fit were compared using linear statistics. Circular statistics were used to compare the orientation of the largest diameter for raw ultrasound measurements, model estimations of largest diameter, and autorefractor determined keratometric axes.

RESULTS

The mean model diameters were anterior chamber OD 12.07 mm (0.32 SD); anterior chamber OS 12.06 mm (0.36 SD); posterior chamber OD 12.35 mm (0.42 SD); posterior chamber OS 12.33 mm (0.43 SD). The general trend for orientation of the meridian of largest diameter was in the horizontal meridian. In over 35% of eyes the difference between AC or PC meridian and the flat keratometric axis was greater than 20 degrees.

CONCLUSIONS

Accurate and reproducible anterior segment biometry depends on visualization of structures and minimization of eye and head movement error. The range and standard deviation of the diameter and orientation measures suggests anatomic variation is sufficient to require biometry for proper sizing and placement of intraocular devices that use angle or sulcus fixation.

Iridociliary apposition in plateau iris syndrome persists after cataract extraction

PURPOSE

To evaluate the ultrasound biomicroscopic appearance of the anterior segment before and after cataract extraction in eyes with plateau iris syndrome and to determine the effect of postoperative zonular relaxation on ciliary body position.

DESIGN

Interventional case series.

METHODS

Eyes with plateau iris syndrome scanned before and after cataract extraction between January 1994 and September 2001 were enrolled. The iridociliary relationship and the anterior chamber depth at a distance of 3 mm from the scleral spur were assessed.

RESULTS

We examined six eyes of six patients. Mean patient age was 74.2 +/- 6.4 years (standard deviation [SD]) (range, 65-81 years). Mean refractive error was + 1.0 +/- 3.9 diopters [D] (range, -5.75-+5.50), and mean axial length was 21.85 +/- 0.77 mm (range, 20.90-22.95 mm). All eyes had undergone laser iridotomy and argon laser peripheral iridoplasty before cataract extraction. Ultrasound biomicroscopy examination revealed a narrow angle and absence of a ciliary body sulcus in all eyes with focal areas of iridotrabecular apposition in three eyes. Following cataract extraction, the anterior chamber depth increased (P =.0006, paired t test), while the iridociliary contact remained unchanged.

CONCLUSIONS

Iridociliary apposition persists after cataract extraction in plateau iris syndrome. Whether the cause is congenital or acquired, or both, remains to be determined.

Exchange of a posterior chamber phakic intraocular lens in a highly myopic eye

A 38-year-old woman had posterior chamber phakic intraocular lens (IOL) implantation as a secondary refractive procedure to correct residual refraction (20/50 with -16.50 -1.50 x 80) in May 1998, 3 years after intrastromal corneal ring segment surgery for high myopia (-30.00 diopters). Ultrasound biomicroscopy revealed an oversized lens, leading to malpositioning. Moreover, the patient remained undercorrected (20/40 with -5.25 -0.75 x 120). Ten months later, the phakic IOL was uneventfully exchanged for a shorter one with the correct dioptric power. It was well placed in the posterior chamber. The patient's visual acuity was 20/30 with -2.25 -0.75 x 145, very close to the refraction in the fellow aphakic eye (20/30 with -2.50 -0.75 x 75). Patient satisfaction with the final visual outcome was high. Accurate ciliary sulcus measurement is critical for proper phakic IOL sizing.