Comparison of internal anterior chamber diameter measured with ultrabiomicroscopy with white-to-white distance measured using digital photography in aphakic eyes

PURPOSE

Measuring the anterior chamber diameter (AC) is important both for diagnostics and before ocular surgery. In clinical practice, horizontal AC diameter is usually estimated on the basis of measurements of corneal diameter (so-called white-to-white [WTW] distance). The usual method for selecting an appropriate size for an AC lens is to add 1 mm to WTW measurement. The purpose of this study was to compare AC diameter measured using ultrasound biomicroscopy (UBM) with WTW distance measured using digital photography in aphakic eyes.

METHODS

The data were gathered prospectively from a nonrandomized consecutive series of aphakic patients. The examined group consisted of 23 eyes of 23 adult patients, mean age 71.17 years. WTW diameter was measured in the 3 o'clock and 9 o'clock meridian on a digital photograph. Internal horizontal AC diameter measurements were performed in the 3 o'clock and 9 o'clock meridian with the Sonomed Ultrabiomicroscopy device with a 50-MHz probe.

RESULTS

Mean horizontal WTW diameter measured using digital photographs was 11.65+/-0.38 mm and mean horizontal internal AC diameter measured using UBM was 13.53+/-0.83 mm. A significant difference in mean WTW diameter measured using digital photography and UBM was found (Mann-Whitney U test, p<0.05). There was a significant correlation between these values (Spearman=0.70, p<0.001).

CONCLUSIONS

In order to obtain good and precise measurements of internal AC diameter, a method of direct visualization of the intraocular structures should be used. Despite the limits of a small case series, our results support the use of UBM technique for preoperative evaluation of the internal AC diameter and AC intraocular lens sizing in aphakic eyes.

Anterior chamber width measurement by high-speed optical coherence tomography

OBJECTIVE

To measure anterior chamber (AC) width and other dimensions relevant to the sizing of phakic intraocular lenses (IOLs) with a high-speed optical coherence tomography (OCT) system.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Both eyes of 20 normal volunteers.

METHODS

A novel high-speed (4000 axial scans/second) OCT prototype was developed for anterior segment scanning. The system uses long wavelength (1310 nm) for deeper angle penetration, rectangular scanning for undistorted imaging, and short image acquisition time (0.125 seconds) to reduce motion error. Three horizontal cross-sectional OCT images (15.5 mm wide and 6 mm deep) of the anterior segment were obtained from each eye with real-time image display to guide centration on the corneal apex. Image processing software was developed to correct for image warping resulting from index transitions. Anterior chamber dimensions were measured using computer calipers by 3 expert raters (ophthalmologists). Analysis of variance was used to determine interrater, interimage, right versus left eye, and intersubject standard deviation (SD) of OCT measurements.

MAIN OUTCOME MEASURES

Anterior chamber width (recess to recess), AC depth, and crystalline lens vault as measured by OCT; external white-to-white (WTW) corneal diameter (CD) as measured by Holladay-Godwin gauge.

RESULTS

The mean AC width was 12.53+/-0.47 mm (intereye SD), and the mean corneal diameter was 11.78+/-0.57 mm. Optical coherence tomography measurement of AC width has good repeatability from image to image (SD, 0.134 mm), but there was significant difference between raters (SD, 0.215 mm). Estimation of AC width from WTW CD by linear regression was relatively inaccurate (residual SD, 0.41 mm). The mean AC depth was 2.99+/-0.323 mm (intereye SD), with repeatability of less than 0.001 mm (interimage SD), and the mean crystalline lens vault was 0.39+/-0.27 mm with 0.023 mm repeatability.

CONCLUSIONS

Reproducible OCT AC biometry was demonstrated using a high-speed OCT prototype. Further improvement in reproducibility may be achieved by automating the measurements with a computer. Direct OCT AC width measurement may improve sizing of angle-supported AC IOLs over conventional estimation by WTW CD. The measurement of AC depth and lens vault also may be useful for other types of phakic AC IOLs.

Correction of pseudophakic anisometropia with the Staar Collamer implantable contact lens

PURPOSE

To assess the role of the Staar Surgical implantable contact lens (ICL) for the correction of pseudophakic anisometropia.

SETTING

Oxford Eye Hospital, Oxford, and Rosen Eye Center, Alexandra Hospital, Manchester, United Kingdom.

METHODS

Six patients with pseudophakic anisometropia ranging from 2.0 to 7.9 diopters (D) (mean 4.4 D) had ICL implantation as an alternative to intraocular lens (IOL) exchange or conventional piggyback IOLs.

RESULTS

All patients had a reduction in anisometropia to asymptomatic levels. The mean reduction was 3.15 D. No patient experienced adverse effects.

CONCLUSIONS

The implantable contact lens offers an alternative approach to the management of pseudophakic anisometropia that avoids some of the risks associated with IOL exchange, corneal refractive surgery, and conventional piggyback IOLs.

Safety of posterior chamber phakic intraocular lenses for the correction of high myopia: anterior segment changes after posterior chamber phakic intraocular lens implantation

OBJECTIVE

To assess the safety of posterior chamber phakic intraocular lens (PCPIOL) implantation in patients with high myopia.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Twenty eyes of 10 patients were included.

INTERVENTION

Staar Collamer Implantable Contact Lens PCPIOLs were implanted for the correction of high myopia.

MAIN OUTCOME MEASURES

Intra- and postoperative complications were recorded. Specular microscopy, lens fluorophotometry, laser flare-meter, and ultrasound biomicroscopy were performed before surgery and at different stages of the follow-up period to evaluate endothelial cell density, crystalline lens transmittance, aqueous flare, and anatomic relations of the implanted lenses with the other structures of the anterior segment.

RESULTS

There were no intraoperative complications. One patient experienced pupillary entrapment by the lens in the immediate postoperative period, which was resolved without incident. Pigmentary dispersion or cataracts did not appear during the postoperative period. All the lenses remained correctly centered, and no patient reported night halos or glare. Anterior chamber depth showed a statistically significant reduction, between 9% and 12%. Central endothelial density was significantly decreased after surgery. The percentages of cell loss after 3, 6, 12, 18, and 24 months were 4.41%, 4.83%, 5.17%, 5.46%, and 6.57%, respectively. Aqueous flare increased by 49.19% in the first postoperative month in relation to preoperative values. Afterward, it decreased and then remained above preoperative values for the entire follow-up period (33.76% at month 3, 27.81% at month 6, 27.65% at month 12, 23.39% at month 18, and 27.27% at month 24). Crystalline lens transmittance decreased by 0.72% at month 3, by 1.44% at month 6, by 1.95% at month 12, by 2.25% at month 18, and by 2.24% at month 24. Finally, by ultrasound biomicroscopy it was observed that the PCPIOL and the crystalline lens were in contact on the peripheral level in 12 patients (60%) and in the center in another three patients (15%) during at least one checkup. In all the patients, contact between the PCPIOL and the posterior iris surface could be observed.

CONCLUSIONS

Posterior chamber phakic IOL implantation for the surgical correction of high myopia is a safe procedure with regard to immediate visual and refractive results. The short-term clinical benefit and lack of immediate surgical complications are impressive. However, the increase in flare, the endothelial cell loss, the decrease in crystalline lens transmittance, and the iris-PCPIOL and crystalline lens-PCPIOL contact are findings that suggest caution regarding the long-term safety of this lens implant.

Surgical correction of severe myopia with an angle-supported phakic intraocular lens

PURPOSE

To evaluate the effectiveness, predictability, and safety of a fourth-generation angle-supported anterior chamber phakic intraocular lens (IOL) in patients with severe myopia.

SETTING

Refractive Surgery and Cornea Unit, Alicante Institute of Ophthalmology, Miguel Hernández University School of Medicine, Alicante, Spain.

METHODS

In this prospective study, 23 eyes (16 patients) with a mean preoperative myopia of -19.56 diopters (D) +/- 1.76 (SD) (range -16.75 to -23.25 D) were implanted with the ZSAL-4 phakic IOL. Basic examinations were performed before and after surgery in all patients. Eighteen eyes were also studied by clinical specular microscopy, and the endothelium was analyzed for cell density, coefficient of variation in cell size, and hexagonality. The location of the IOL in the anterior chamber was evaluated in 10 eyes by A-scan biometry. To evaluate haptic geometry, a theoretical mechanical model was used. The follow-up was 24 months in all patients.

RESULTS

Uncorrected visual acuity was 20/40 or better in 13 eyes (56.0%) 12 months after surgery and in 14 eyes (60.8%) at 24 months. Best spectacle-corrected visual acuity improved 0.19 at 12 and 24 months (0.1 = 1 line) from preoperative values. The efficacy index was 1.12 at 24 months and the safety index, 1.45. The mean postoperative spherical equivalent was -0.65 +/- 0.65 D at 24 months. The postoperative spherical equivalent was within +/-1.00 D of emmetropia in 19 eyes (82.6%) at 12 and 24 months. The mean endothelial cell loss was 3.50% at 12 months and 4.18% at 24 months. The coefficient of variation in cell size decreased from 0.34 before surgery to 0.28 at 24 months after surgery. The IOL was located 0.79 +/- 0.24 mm in front of the crystalline lens. Postoperative complications included night halos in 6 eyes (26.1%) at 12 and 24 months and pupil ovalization in 4 eyes (17.4%). Intraocular lens rotation was observed in 10 eyes (43.5%) at 24 months. Two eyes (8. 7%) developed a slight inflammatory response during the first 6 months. Our mechanical model predicted that the compression forces against the angle structures were greater at the first footplate than at the second.

CONCLUSIONS

Implantation of the ZSAL-4 IOL in the anterior chamber of phakic eyes was effective and predictable in correcting severe myopia. However, the ZSAL-4 did not prevent pupil ovalization, IOL rotation, or low-grade postoperative uveitis. Improvements in haptic design following our mechanical model could decrease these haptic-related complications.

Advances in refractive surgery: 1975 to the present

PURPOSE

To review the major advances in the field of refractive surgery occurring over the past 25 years.

METHODS

Literature review.

RESULTS

The major developments in refractive surgery over the past 25 years are reviewed.

CONCLUSIONS

The past 25 years have witnessed great changes in refractive surgery. As a result of advancements in technology, instrumentation, and technique, we have seen improvements in the treatment of all types of ametropias. In this article, we review some of the successes and failures of the past quarter-century.

Scleral Fixation for a Phakic Anterior Chamber Disc Intraocular Lens

BACKGROUND

Angle-supported phakic anterior chamber intraocular lenses (IOLs) require a high degree of anterior vaulting, but this can cause an inadequate distance between the IOL and the cornea, especially during rubbing or squeezing of the eye.

METHODS

A vaultless implant was designed by anchoring 3 supple hepatics through the anterior chamber into the sclera. Thus, a suspended rather than a wedged implant was achieved.

RESULTS

The lens was implanted in 3 eyes of 2 patients in 1990. Good tolerance of the IOL was maintained over 7 years of follow-up.

CONCLUSION

A suspended anterior chamber phakic IOL maintains an adequate position with lack of bowing and shows promising results.

Staar Collamer posterior chamber phakic intraocular lens to correct myopia and hyperopia

PURPOSE

To evaluate the efficacy, safety, stability, and predictability of implanting a collagen polymer (Staar Collamer), posterior chamber phakic intraocular lens (IOL) to correct myopia and hyperopia.

SETTING

Centre for Advanced Refractive Eye Surgery at the BMI Alexandra Hospital, Cheadle, Manchester, United Kingdom.

METHODS

A Staar Collamer posterior chamber phakic IOL was implanted in 25 eyes of 14 patients with a mean age of 37.9 years (range 20 to 50 years). Seven patients were men and seven, women. Sixteen were myopic and 9, hyperopic. Before treatment, each patient had a thorough evaluation including refractive, general, ocular, and social and personal histories. The examination included visual acuity, refraction, tonometry, topography, biometry, biomicroscopy, pupil size in dim illumination, and posterior segment evaluation by a vitreoretinal specialist. Patients were informed about the surgical process and expected outcome, their own expectations were discussed, and their consent to surgery was obtained. Surgical implantation was performed through a less than 3.0 mm clear corneal sutureless incision using brief general anesthesia on a day-case surgical basis.

RESULTS

At 3 months postoperatively, all eyes had a significant increase in uncorrected visual acuity, allowing all but two patients (three eyes) to manage most activities without spectacles. Adjustment by incisional corneal surgery was planned for undercorrected myopic eyes (n = 3). Pupil block glaucoma and pigment deposits occurred in one patient each.

CONCLUSION

In this short-term study, the posterior chamber phakic IOL was predictable, safe, and efficacious in the correction of myopic and hyperopic refractive errors, with good refractive stability. Long-term follow-up is required to validate that the absence of significant complications in most patients is a lasting phenomenon.

Ultrasound Biomicroscopy of Baikoff Anterior Chamber Phakic Intraocular Lenses

BACKGROUND

The purpose of the study was to analyze qualitatively and quantitatively anatomic relationships of anterior chamber Baikoff phakic intraocular lenses (IOL) to the cornea, angle, iris, and lens in myopic eyes.

METHODS

Thirteen phakic myopic eyes (-9.00 to -15.00 diopters) corrected by minus power, angle-supported, anterior chamber intraocular lenses of the ZB5M style (Chiron-Domilens), with a mean follow-up of 25 months (range 18 to 36 months), were examined clinically and by ultrasound biomicroscopy.

RESULTS

The mean distance (+/- SD) between the central cornea and the IOL was 2.05 +/- 0.18 mm (range 1.8 to 2.47 mm); mean distance between the corneal periphery and the IOL was 1.56 +/- 0.17 mm (range 1.33 to 1.95 mm); and the mean distance between the IOL and the lens was 0.58 +/- 0.12 mm (range 0.48 to 0.81 mm). IOL footplates seemed to be correctly positioned in the angle in all eyes. We observed no goniosynechiae. In six eyes, we found localized posterior indentation of the iris caused by the haptics. Four of these six eyes exhibited oval pupils associated with an oversized IOL.

CONCLUSIONS

High frequency ultrasound biomicroscopy can define anatomic relationships of anterior chamber phakic IOLs, and help analyze the mechanisms of corneal and iris complications.

Correction of High Myopia With the Worst Myopia Claw Intraocular Lens

BACKGROUND

Phakic anterior chamber lenses is one of the modalities used to correct high myopia. We report the initial results of our prospective study on the Worst myopia claw intraocular lens (IOL) that is fixated to the anterior iris.

METHODS

We studied 35 eyes in 18 patients with a preoperative myopia ranging from -6.00 to -28.00 diopters (D). The follow up ranged from 6 months (n = 15) to 12 months (n = 20).

RESULTS

In 26 (74.3%) eyes, the postoperative spherical equivalent refractive error was within 1.00 D of emmetropia. The mean refraction was stable between 1 to 2 months and 12 months. The mean spectacle-corrected visual acuity improved from 20/50 to 20/40. The straylight measurements did not show a significant increase postoperatively (p = .64). The mean endothelial cell loss was 5.6% (range, +6.3% to -22.6%) at 6 months, and 8.9% (range, +0.77% to -23.5%) at 12 months. We did not encounter major complications.

CONCLUSION

Implanting a Worst myopia claw IOL in high myopic eyes resulted in a stable, reasonably accurate refractive outcome. This group of patients will be followed longer because of concern over ocular complications with this technique.