Charles J. Pavlin

Clinical Use of Ultrasound Biomicroscopy

The authors have developed a method of obtaining images of cross-sections of the intact anterior globe at microscopic resolution. High-frequency ultrasound transducers (50-100 MHz) have been developed and incorporated into a clinical B-scan device capable of producing images in the living human eye to a depth of approximately 4 mm at an axial and lateral resolution approaching 20 microns. Clinical use of this instrument is no more difficult than conventional immersion ultrasonography. The authors results in a series of 14 clinical cases have shown that this method can provide information unavailable from any other imaging technique. Anterior segment tumors difficult to define with conventional ultrasound can be measured and the extent of invasion determined. Differentiation of tissue on the basis of internal acoustic characteristics is aided by the very fine backscatter speckle patterns at these frequencies. Pathology behind anterior segment opacities can be imaged in detail and the ability to image angle structures in cross-section allows a new quantitative method of gonioscopy. The ability to define the relationship of the iris, posterior chamber, zonules, ciliary body, and lens is potentially helpful in understanding mechanisms of glaucoma. Ocular structures can be measured with increased accuracy. Clinical ultrasound biomicroscopy (UBM) has shown significant potential as an aid in diagnoses of ocular disease.

Subsurface Ultrasound Microscopic Imaging of the Intact Eye

The authors have developed a method of obtaining images of cross sections of the intact eye at microscopic resolution. High-frequency ultrasound transducers (100 MHz) have been developed and incorporated into imaging devices. These devices are capable of producing images to a depth of 4 mm at an axial and lateral resolution approaching 20 microns. Resolution exceeds that of current combined A- and B-scan imaging devices by a factor of approximately 10. Microscopic images of ocular structures including Schlemms canal, cornea, iris, ciliary muscles, and retina have been produced in eye bank eyes. These studies show the feasibility of developing an apparatus to be used in the clinical setting for examining anterior structures of the eye not visible by current techniques.

Ultrasound biomicroscopic quantitative analysis of light-dark changes associated with pupillary block

PURPOSEnTo quantitatively analyze the changes in anterior chamber angle and iris configuration induced by varying illumination in patients with narrow angles and pupillary block.nnnMETHODSnTwenty-four eyes of 24 patients with pupillary block (mean age, 52.5 years) had ultrasound biomicroscopic images of the angle and iris structures obtained superiorly, nasally, inferiorly, and temporally. Images were performed in the light and the dark. We measured the angle opening distance, iris thickness, iris chord length, iris-lens touch, and iris curvature.nnnRESULTSnChanges in iris and angle configuration occurred within a few seconds of a change in lighting. The mean dark measurements were statistically significantly less than the mean light measurements for angle opening distance (96 +/- 18 vs 185 +/- 26 microm, P = .0001), iris chord length (2,505 +/- 61 vs 3,001 +/- 69 microm, P = .0001), and iris-lens touch (350 +/- 20 vs 693 +/- 35 microm, P = .0001). The mean dark measurements were statistically significantly greater than the mean light measurements for iris thickness at 500 microm from the scleral spur (367 +/- 10 vs 307 +/- 25 microm, P = .0001), and 1,500 microm from the scleral spur (404 +/- 14 vs 347 +/- 12 microm, P = .0001). Iris curvature in all four quadrants was statistically significantly greater in the dark than the light.nnnCONCLUSIONSnThis study quantitatively confirms that angle narrowing in the dark in eyes with pupillary block is associated with iris shortening, increased iris thickness, and increased iris convexity. Iris-lens touch is relatively small in pupillary block and decreases with dilation. Angle narrowing with dilation is not related to increased iris-lens touch and occurs promptly without requiring time for aqueous pressure buildup behind the iris.

Plateau iris syndrome: changes in angle opening associated with dark, light, and pilocarpine administration

PURPOSEnTo report changes in angle configuration associated with dark, light, and pilocarpine administration in plateau iris syndrome.nnnMETHODnIn 10 eyes of 10 patients with plateau iris syndrome and persistent narrow angles after patent peripheral Nd:YAG laser iridotomy, ultrasound biomicroscopy was used to image variations in angle opening, iris thickness, and trabecular-ciliary process distance. Measurements were taken in the dark, in full room light, and after administration of pilocarpine 2%.nnnRESULTSnAverage angle opening distance increased in the light compared with the dark (113+/-34 microm vs. 22+/-34 microm, P = .0001) and increased further after pilocarpine administration (171+/-52 microm vs. 113+/-34 microm, P = .0034). Average iris thickness decreased in the light compared with the dark (338+/-34 microm vs. 436+/-58 microm, P = .0009) and decreased further after pilocarpine administration (253+/-48 microm vs. 338+/-34 microm, P = .0002). Average trabecular meshwork-ciliary process distance measurements were smaller than normal and did not change significantly in the light compared with the dark (481+/-42 microm vs. 464+/-44 microm, P = .4001) or after pilocarpine administration compared with light (451+/-67 microm vs. 481+/-42 microm, P = .1304).nnnCONCLUSIONSnIn plateau iris syndrome, anteriorly located ciliary processes support the peripheral iris. Changes in angle opening in dark and light are solely related to changes in iris thickness. Pilocarpine produces iris thinning and is an effective method of opening the angle. Ultrasound biomicroscopy can be used to perform a darkroom provocative test, which provides information on whether the angle anatomically closes in the dark.

Ultrasound biomicroscopic imaging of the anterior aspect of peripheral choroidal melanomas.

PURPOSEnTo correlate ultrasound biomicroscopic features of the anterior aspect of peripheral choroidal melanoma with respect to histopathology.nnnMETHODSnWe examined 17 eyes of 17 patients who had clinically diagnosed peripheral choroidal melanomas that approached the ora serrata or extended into the ciliary body and who had been assessed with ultrasound biomicroscopy before enucleation. Comparisons were made between anterior tumor margins imaged by ultrasound biomicroscopy and histopathologic specimens. Anatomic features noted on ultrasound biomicroscopy before enucleation were correlated with enucleation specimens, including supraciliary effusion, rotation of the ciliary body, angle involvement, and internal reflectivity patterns. Anterior tumor margin position was determined with reference to the scleral spur.nnnRESULTSnMean distances from the anterior tumor margin to the scleral spur were 1.47 mm on ultrasound biomicroscopy and 1.65 mm on pathologic examination. This difference was not statistically significant (P = .325). Tumor features evident on ultrasound biomicroscopy were also seen on pathologic examination: supraciliary choroidal effusions in seven of seven, ciliary body rotation in seven of eight, and angle involvement in seven of eight. All tumors were mixed-cell melanomas, and 12 of 17 (70%) demonstrated homogeneous ultrasound biomicroscopic internal reflectivity. Irregular internal reflectivity was seen in five of 17 tumors (29%) and was related to prominent internal vascularity on pathology in three of five.nnnCONCLUSIONSnUltrasound biomicroscopy is an accurate imaging technique for the in vivo assessment of anterior tumor margins of peripheral choroidal melanomas and can provide detailed imaging of the tumors interface with the ciliary body.

Anterior chamber depth in plateau iris syndrome and pupillary block as measured by ultrasound biomicroscopy.

PURPOSEnTo quantitatively analyze the anterior chamber depth (ACD) in patients with pupillary block and plateau iris syndrome.nnnDESIGNnRetrospective, consecutive, observational case series.nnnMETHODSnWe measured the ACD in 318 eyes of 318 patients who had been diagnosed by ultrasound biomicroscopy as having either pupillary block or plateau iris syndrome. Pupillary block patients were all preiridotomy and plateau iris patients were all postiridotomy. Anterior chamber depth was measured axially from the internal corneal surface to the lens surface using the ultrasound instruments internal measuring capability.nnnRESULTSnThe mean ACD in patients with plateau iris syndrome (n = 181) was significantly smaller than the hypothesized normal ACD (2.04 +/- 0.30 mm vs 3.0 mm, P =.0001). The mean ACD in patients with pupillary block (n = 137) was also significantly smaller than the hypothesized normal ACD (2.17 +/- 0.30 mm vs 3.0 mm, P =.0001). The mean ACD in patients with plateau iris syndrome was significantly smaller than the ACD in patients with pupillary block (2.04 +/- 0.30 mm vs 2.17 +/- 0.30 mm, P =.001).nnnCONCLUSIONSnReview of the literature suggests that patients with plateau iris have a normal or deeper axial ACD compared with pupillary block. This study found that the ACD associated with plateau iris syndrome is shallower than normal and also shallower than in pupillary block.

Retinitis pigmentosa, nanophthalmos, and optic disc drusen : A case report

OBJECTIVEnAlthough the associations of retinitis pigmentosa (RP) with nanophthalmos/microphthalmos and RP with optic disc drusen have previously been recognized, the concurrence of all three features, as far as the authors are aware, has not previously been reported.nnnDESIGNnCase report.nnnRESULTSnThe authors report a sporadic case of nanophthalmos, RP, and optic nerve drusen with the additional complication of chronic angle closure glaucoma.nnnCONCLUSIONSnVisual loss may be secondary to the complications of nanophthalmos, RP, or optic nerve drusen. Chronic angle closure may be caused by choroidal effusion with serous retinal detachment, which may, in turn, cause a pseudo-RP picture. It is therefore important to recognize the possible association of true RP with nanophthalmos as a cause for visual deterioration.

Follow-up of 3 patients with Ridleyintraocular lens implantation

Three patients in whom Ridley intraocular lenses (IOLs) were successfully implanted more than 42 years ago are presented. One case had traumatic cataract at age 13. The other 2 had surgery for unilateral cataract of unknown etiology at about age 40 and surgery on the second eye approximately 40 years later. A review of other reports of late-term results with this IOL is included.

High-frequency doppler ultrasound examination of blood flow in the anterior segment of the eye

PURPOSEnTo show that extending Doppler imaging into the high-frequency domain could allow detection and characterization of blood flow in small arterioles and capillaries.nnnMETHODSnA 40-MHz continuous wave Doppler system and a 60-MHz pulsed-wave Doppler system were constructed, tested, and used to examine the ciliary body region in two normal volunteers.nnnRESULTSnCiliary body circulation in the region of the great circle of the iris, which is undetectable by conventional 7.5-MHz duplex Doppler, was consistently and reproducibly detectable by high-frequency (40-MHz and 60-MHz) Doppler systems.nnnCONCLUSIONnHigh-frequency Doppler imaging may provide a unique new tool for the characterization and assessment of anterior segment ocular blood flow.

Use of microbubble ultrasound contrast agent to demonstrate the iris valve effect in human eye bank eyes

PURPOSEnTo demonstrate that the interface between the normal iris and the lens surface functions as a flap valve.nnnMETHODnMicrobubble ultrasound contrast agent was injected into the anterior and posterior chambers of human eye bank eyes and the distribution of contrast imaged with high-frequency ultrasound.nnnRESULTSnContrast agent did not enter the posterior chamber when injected into the anterior chamber, but contrast agent injected into the posterior chamber easily flowed into the anterior chamber.nnnCONCLUSIONSnThe iris-lens interface normally functions as a flap valve, preventing retrograde flow from the anterior to the posterior chamber. A temporary increase in anterior chamber pressure thus results in iris concavity in pigmentary dispersion syndrome.