Oculomics: A Crusade Against the Four Horsemen of Chronic Disease

Chronic, non-communicable diseases present a major barrier to living a long and healthy life. In many cases, early diagnosis can facilitate prevention, monitoring, and treatment efforts, improving patient outcomes. There is therefore a critical need to make screening techniques as accessible, unintimidating, and cost-effective as possible. The association between ocular biomarkers and systemic health and disease (oculomics) presents an attractive opportunity for detection of systemic diseases, as ophthalmic techniques are often relatively low-cost, fast, and non-invasive. In this review, we highlight the key associations between structural biomarkers in the eye and the four globally leading causes of morbidity and mortality: cardiovascular disease, cancer, neurodegenerative disease, and metabolic disease. We observe that neurodegenerative disease is a particularly promising target for oculomics, with biomarkers detected in multiple ocular structures. Cardiovascular disease biomarkers are present in the choroid, retinal vasculature, and retinal nerve fiber layer, and metabolic disease biomarkers are present in the eyelid, tear fluid, lens, and retinal vasculature. In contrast, only the tear fluid emerged as a promising ocular target for the detection of cancer. The retina is a rich source of oculomics data, the analysis of which has been enhanced by artificial intelligence-based tools. Although not all biomarkers are disease-specific, limiting their current diagnostic utility, future oculomics research will likely benefit from combining data from various structures to improve specificity, as well as active design, development, and optimization of instruments that target specific disease signatures, thus facilitating differential diagnoses.

Extracting spacing-derived estimates of rod density in healthy retinae

Quantification of the rod photoreceptor mosaic using adaptive optics scanning light ophthalmoscopy (AOSLO) remains challenging. Here we demonstrate a method for deriving estimates of rod density and rod:cone ratio based on measures of rod spacing, cone numerosity, and cone inner segment area. Twenty-two AOSLO images with complete rod visualization were used to validate this spacing-derived method for estimating density. The method was then used to estimate rod metrics in an additional 105 images without complete rod visualization. The spacing-derived rod mosaic metrics were comparable to published data from histology. This method could be leveraged to develop large normative databases of rod mosaic metrics, though limitations persist with intergrader variability in assessing cone area and numerosity.

Foveal Cone Structure in Patients With Blue Cone Monochromacy

Purpose

Blue cone monochromacy (BCM) is a rare inherited cone disorder in which both long- (L-) and middle- (M-) wavelength sensitive cone classes are either impaired or nonfunctional. Assessing genotype-phenotype relationships in BCM can improve our understanding of retinal development in the absence of functional L- and M-cones. Here we examined foveal cone structure in patients with genetically-confirmed BCM, using adaptive optics scanning light ophthalmoscopy (AOSLO).

Methods

Twenty-three male patients (aged 6-75 years) with genetically-confirmed BCM were recruited for high-resolution imaging. Eight patients had a deletion of the locus control region (LCR), and 15 had a missense mutation-Cys203Arg-affecting the first two genes in the opsin gene array. Foveal cone structure was assessed using confocal and non-confocal split-detection AOSLO across a 300 × 300 µm area, centered on the location of peak cell density.

Results

Only one of eight patients with LCR deletions and 10 of 15 patients with Cys203Arg mutations had analyzable images. Mean total cone density for Cys203Arg patients was 16,664 ± 11,513 cones/mm2 (n = 10), which is, on average, around 40% of normal. Waveguiding cone density was 2073 ± 963 cones/mm2 (n = 9), which was consistent with published histological estimates of S-cone density in the normal eye. The one patient with an LCR deletion had a total cone density of 10,246 cones/mm2 and waveguiding density of 1535 cones/mm2.

Conclusions

Our results show that BCM patients with LCR deletions and Cys203Arg mutations have a population of non-waveguiding photoreceptors, although the spectral identity and level of function remain unknown.

Comparing Retinal Structure in Patients with Achromatopsia and Blue Cone Monochromacy Using OCT

Purpose

To compare foveal hypoplasia and the appearance of the ellipsoid zone (EZ) at the fovea in patients with genetically confirmed achromatopsia (ACHM) and blue cone monochromacy (BCM).

Design

Retrospective, multi-center observational study.

Subjects

Molecularly confirmed patients with ACHM (n = 89) and BCM (n = 33).

Methods

We analyzed high-resolution spectral domain optical coherence tomography (SD-OCT) images of the macula from aforementioned patients with BCM. Three observers independently graded SD-OCT images for foveal hypoplasia (i.e. retention of one or more inner retinal layers at the fovea) and four observers judged the integrity of the EZ at the fovea, based on an established grading scheme. These measures were compared with previously published data from the ACHM patients.

Main Outcome Measures

Presence of foveal hypoplasia and EZ grade.

Results

Foveal hypoplasia was significantly more prevalent in ACHM than in BCM (p<0.001). In addition, we observed a significant difference in the distribution of EZ grades between ACHM and BCM, with grade II EZ being by far the most common phenotype in BCM (61% of patients). In contrast, ACHM patients had a relatively equal prevalence of EZ grades I, II, and IV. Interestingly, grade IV EZ was 2.6 times more prevalent in ACHM compared to BCM, while grade V EZ (macular atrophy) was present in 3% of both the ACHM and BCM cohorts.

Conclusions

The higher incidence of foveal hypoplasia in ACHM than BCM supports a role for cone activity in foveal development. Although there are differences in EZ grades between these conditions, the degree of overlap suggests EZ grade is not sufficient for definitive diagnosis, in contrast to previous reports. Analysis of additional OCT features in similar cohorts may reveal differences with greater diagnostic value. Finally, the extent to which foveal hypoplasia or EZ grade is prognostic for therapeutic potential in either group remains to be seen, but motivates further study.

Optical Coherence Tomography Artifacts Are Associated With Adaptive Optics Scanning Light Ophthalmoscopy Success in Achromatopsia

Purpose

To determine whether artifacts in optical coherence tomography (OCT) images are associated with the success or failure of adaptive optics scanning light ophthalmoscopy (AOSLO) imaging in subjects with achromatopsia (ACHM).

Methods

Previously acquired OCT and non-confocal, split-detector AOSLO images from one eye of 66 subjects with genetically confirmed achromatopsia (15 CNGA3 and 51 CNGB3) were reviewed along with best-corrected visual acuity (BCVA) and axial length. OCT artifacts in interpolated vertical volumes from CIRRUS macular cubes were divided into four categories: (1) none or minimal, (2) clear and low frequency, (3) low amplitude and high frequency, and (4) high amplitude and high frequency. Each vertical volume was assessed once by two observers. AOSLO success was defined as sufficient image quality in split-detector images at the fovea to assess cone quantity.

Results

There was excellent agreement between the two observers for assessing OCT artifact severity category (weighted kappa = 0.88). Overall, AOSLO success was 47%. For subjects with OCT artifact severity category 1, AOSLO success was 65%; for category 2, 47%; for category 3, 11%; and for category 4, 0%. There was a significant association between OCT artifact severity category and AOSLO success (P = 0.0002). Neither BCVA nor axial length was associated with AOSLO success (P = 0.07 and P = 0.75, respectively).

Conclusions

Artifacts in OCT volumes are associated with AOSLO success in ACHM. Subjects with less severe OCT artifacts are more likely to be good candidates for AOSLO imaging, whereas AOSLO was successful in only 7% of subjects with category 3 or 4 OCT artifacts. These results may be useful in guiding patient selection for AOSLO imaging.

Translational Relevance

Using OCT to prescreen patients could be a valuable tool for clinical trials that utilize AOSLO to reduce costs and decrease patient testing burden.

Interocular Symmetry of Foveal Cone Topography in Congenital Achromatopsia

Purpose: To determine the interocular symmetry of foveal cone topography in achromatopsia (ACHM) using non-confocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO). Methods: Split-detector AOSLO images of the foveal cone mosaic were acquired from both eyes of 26 subjects (mean age 24.3 years; range 8-44 years, 14 females) with genetically confirmed CNGA3- or CNGB3-associated ACHM. Cones were identified within a manually delineated rod-free zone. Peak cone density (PCD) was determined using an 80 × 80 μm sampling window within the rod-free zone. The mean and standard deviation (SD) of inter-cell distance (ICD) were calculated to derive the coefficient of variation (CV). Cone density difference maps were generated to compare cone topography between eyes. Results: PCD (mean ± SD) was 17,530 ± 9,614 cones/mm2 and 17,638 ± 9,753 cones/mm2 for right and left eyes, respectively (p = .677, Wilcoxon test). The mean (± SD) for ICD was 9.05 ± 2.55 µm and 9.24 ± 2.55 µm for right and left eyes, respectively (p = .410, paired t-test). The mean (± SD) for CV of ICD was 0.16 ± 0.03 µm and 0.16 ± 0.04 µm for right and left eyes, respectively (p = .562, paired t-test). Cone density maps demonstrated that cone topography of the ACHM fovea is non-uniform with local variations in cone density between eyes. Conclusions: These results demonstrate the interocular symmetry of the foveal cone mosaic (both density and packing) in ACHM. As cone topography can differ between eyes of a subject, PCD does not completely describe the foveal cone mosaic in ACHM. Nonetheless, these findings are of value in longitudinal monitoring of patients during treatment trials and further suggest that both eyes of a given subject may have similar therapeutic potential and non-study eye can be used as a control.

Intraobserver Repeatability and Interobserver Reproducibility of Foveal Cone Density Measurements in CNGA3- and CNGB3-Associated Achromatopsia

Purpose

To examine repeatability and reproducibility of foveal cone density measurements in patients with CNGA3 - and CNGB3-associated achromatopsia (ACHM) using split-detection adaptive optics scanning light ophthalmoscopy (AOSLO).

Methods

Thirty foveae from molecularly confirmed subjects with ACHM, half of whom harbored disease-causing variants in CNGA3 and half in CNGB3, underwent nonconfocal split-detection AOSLO imaging. Cone photoreceptors within the manually delineated rod-free zone were manually identified twice by two independent observers. The coordinates of the marked cones were used for quantifying foveal cone density. Cone density and difference maps were generated to compare cone topography between trials.

Results

We observed excellent intraobserver repeatability in foveal cone density estimates, with intraclass correlation coefficients (ICCs) ranging from 0.963 to 0.991 for CNGA3 and CNGB3 subjects. Interobserver reproducibility was also excellent for both CNGA3 (ICC = 0.952; 95% confidence interval [CI], 0.903-1.0) and CNGB3 (ICC = 0.968; 95% CI, 0.935-1.0). However, Bland-Altman analysis revealed bias between observers.

Conclusions

Foveal cone density can be measured using the described method with good repeatability and reproducibility both for CNGA3- and CNGB3-associated ACHM. Any degree of bias observed among the observers is of uncertain clinical significance but should be evaluated on a study-specific basis.

Translational Relevance

This approach could be used to explore disease natural history, as well as to facilitate stratification of patients and monitor efficacy of interventions for ongoing and upcoming ACHM gene therapy trials.

Characterization of Retinal Structure in ATF6-Associated Achromatopsia

Purpose

Mutations in six genes have been associated with achromatopsia (ACHM): CNGA3, CNGB3, PDE6H, PDE6C, GNAT2, and ATF6. ATF6 is the most recent gene to be identified, though thorough phenotyping of this genetic subtype is lacking. Here, we sought to test the hypothesis that ATF6-associated ACHM is a structurally distinct form of congenital ACHM.

Methods

Seven genetically confirmed subjects from five nonconsanguineous families were recruited. Foveal hypoplasia and the integrity of the ellipsoid zone (EZ) band (a.k.a., IS/OS) were graded from optical coherence tomography (OCT) images. Images of the photoreceptor mosaic were acquired using confocal and nonconfocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO). Parafoveal cone and rod density values were calculated and compared to published normative data as well as data from two subjects harboring CNGA3 or CNGB3 mutations who were recruited for comparative purposes. Additionally, nonconfocal dark-field AOSLO images of the retinal pigment epithelium were obtained, with quantitative analysis performed in one subject with ATF6-ACHM.

Results

Foveal hypoplasia was observed in all subjects with ATF6 mutations. Absence of the EZ band within the foveal region (grade 3) or appearance of a hyporeflective zone (grade 4) was seen in all subjects with ATF6 using OCT. There was no evidence of remnant foveal cone structure using confocal AOSLO, although sporadic cone-like structures were seen in nonconfocal split-detection AOSLO. There was a lack of cone structure in the parafovea, in direct contrast to previous reports.

Conclusions

Our data demonstrate a near absence of cone structure in subjects harboring ATF6 mutations. This implicates ATF6 as having a major role in cone development and suggests that at least a subset of subjects with ATF6-ACHM have markedly fewer cellular targets for cone-directed gene therapies than do subjects with CNGA3- or CNGB3-ACHM.

Assessing the Interocular Symmetry of Foveal Outer Nuclear Layer Thickness in Achromatopsia

Purpose

We examine the interocular symmetry of foveal outer nuclear layer (ONL) thickness measurements in subjects with achromatopsia (ACHM).

Methods

Images from 76 subjects with CNGA3- or CNGB3-associated ACHM and 42 control subjects were included in the study. Line or volume scans through the fovea of each eye were acquired using optical coherence tomography (OCT). Image quality was assessed for each image included in the analysis using a previously-described maximum tissue contrast index (mTCI) metric. Three foveal ONL thickness measurements were made by a single observer and interocular symmetry was assessed using the average of the three measurements for each eye.

Results

Mean (± standard deviation) foveal ONL thickness for subjects with ACHM was 79.7 ± 18.3 μm (right eye) and 79.2 ± 18.7 μm (left eye) compared to 112.9 ± 15.2 (right eye) and 112.1 ± 13.9 μm (left eye) for controls. Foveal ONL thickness did not differ between eyes for ACHM (P = 0.636) or control subjects (P = 0.434). No significant relationship between mTCI and observer repeatability was observed for either control (P = 0.140) or ACHM (P = 0.351) images.

Conclusions

While foveal ONL thickness is reduced in ACHM compared to controls, the high interocular symmetry indicates that contralateral ONL measurements could be used as a negative control in early-phase monocular treatment trials.

Translational Relevance

Foveal ONL thickness can be measured using OCT images over a wide range of image quality. The interocular symmetry of foveal ONL thickness in ACHM and control populations supports the use of the non-study eye as a control for clinical trial purposes.

RAC-CNN: multimodal deep learning based automatic detection and classification of rod and cone photoreceptors in adaptive optics scanning light ophthalmoscope images

Quantification of the human rod and cone photoreceptor mosaic in adaptive optics scanning light ophthalmoscope (AOSLO) images is useful for the study of various retinal pathologies. Subjective and time-consuming manual grading has remained the gold standard for evaluating these images, with no well validated automatic methods for detecting individual rods having been developed. We present a novel deep learning based automatic method, called the rod and cone CNN (RAC-CNN), for detecting and classifying rods and cones in multimodal AOSLO images. We test our method on images from healthy subjects as well as subjects with achromatopsia over a range of retinal eccentricities. We show that our method is on par with human grading for detecting rods and cones.

Residual Cone Structure in Patients With X-Linked Cone Opsin Mutations

Purpose

To assess residual cone structure in subjects with mutations in exon 2, 3, and 4 of the OPN1LW or OPN1MW opsin.

Methods

Thirteen males had their OPN1LW/OPN1MW opsin genes characterized. The cone mosaic was imaged using both confocal and nonconfocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO), and retinal thickness was evaluated using optical coherence tomography (OCT). Six subjects completed serial imaging over a maximum period of 18 months and cone density was measured across imaging sessions.

Results

Ten subjects had an OPN1LW/OPN1MW "interchange" opsin mutation designated as LIAVA or LVAVA, which both introduce exon 3 splicing defects leading to a lack of functional photopigment in cones expressing LIAVA and greatly reduced functional photopigment in cones expressing LVAVA. Despite disrupted cone reflectivity and reduced numerosity, residual inner segments could be visualized. Similar patterns were observed in individuals with an exon 2 insertion, or an exon 4 splice defect, both of which are also expected to produce cones that are devoid of functional opsin protein. OCT revealed variably reduced retinal thickness. A significant inverse relationship was found between the proportion of waveguiding cones and axial length.

Conclusions

Split-detection imaging revealed that the altered appearance of the cone mosaic in confocal images for subjects with exon 2, 3, and 4 mutations was generally due to disrupted waveguiding, rather than structural loss, making them possible candidates for gene therapy to restore cone function. The relative fraction of waveguiding cones was highly variable across subjects, which appears to influence emmetropization in these subjects.

Deep learning based detection of cone photoreceptors with multimodal adaptive optics scanning light ophthalmoscope images of achromatopsia

Fast and reliable quantification of cone photoreceptors is a bottleneck in the clinical utilization of adaptive optics scanning light ophthalmoscope (AOSLO) systems for the study, diagnosis, and prognosis of retinal diseases. To-date, manual grading has been the sole reliable source of AOSLO quantification, as no automatic method has been reliably utilized for cone detection in real-world low-quality images of diseased retina. We present a novel deep learning based approach that combines information from both the confocal and non-confocal split detector AOSLO modalities to detect cones in subjects with achromatopsia. Our dual-mode deep learning based approach outperforms the state-of-the-art automated techniques and is on a par with human grading.

Adaptive optics imaging of inherited retinal diseases

Adaptive optics (AO) ophthalmoscopy allows for non-invasive retinal phenotyping on a microscopic scale, thereby helping to improve our understanding of retinal diseases. An increasing number of natural history studies and ongoing/planned interventional clinical trials exploit AO ophthalmoscopy both for participant selection, stratification and monitoring treatment safety and efficacy. In this review, we briefly discuss the evolution of AO ophthalmoscopy, recent developments and its application to a broad range of inherited retinal diseases, including Stargardt disease, retinitis pigmentosa and achromatopsia. Finally, we describe the impact of this in vivo microscopic imaging on our understanding of disease pathogenesis, clinical trial design and outcome metrics, while recognising the limitation of the small cohorts reported to date.

REPEATABILITY AND LONGITUDINAL ASSESSMENT OF FOVEAL CONE STRUCTURE IN CNGB3-ASSOCIATED ACHROMATOPSIA

PURPOSE

Congenital achromatopsia is an autosomal recessive disease causing substantial reduction or complete absence of cone function. Although believed to be a relatively stationary disorder, questions remain regarding the stability of cone structure over time. In this study, the authors sought to assess the repeatability of and examine longitudinal changes in measurements of central cone structure in patients with achromatopsia.

METHODS

Forty-one subjects with CNGB3-associated achromatopsia were imaged over a period of between 6 and 26 months using optical coherence tomography and adaptive optics scanning light ophthalmoscopy. Outer nuclear layer (ONL) thickness, ellipsoid zone (EZ) disruption, and peak foveal cone density were assessed.

RESULTS

ONL thickness increased slightly compared with baseline (0.184 μm/month, P = 0.02). The EZ grade remained unchanged for 34/41 subjects. Peak foveal cone density did not significantly change over time (mean change 1% per 6 months, P = 0.126).

CONCLUSION

Foveal cone structure showed little or no change in this group of subjects with CNGB3-associated achromatopsia. Over the time scales investigated (6-26 months), achromatopsia seems to be a structurally stable condition, although longer-term follow-up is needed. These data will be useful in assessing foveal cone structure after therapeutic intervention.

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

Purpose

Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction.

Methods

We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family.

Results

There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array.

Conclusions

Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus.

Residual Foveal Cone Structure in CNGB3-Associated Achromatopsia

PURPOSE

Congenital achromatopsia (ACHM) is an autosomal recessive disorder in which cone function is absent or severely reduced. Gene therapy in animal models of ACHM have shown restoration of cone function, though translation of these results to humans relies, in part, on the presence of viable cone photoreceptors at the time of treatment. Here, we characterized residual cone structure in subjects with CNGB3-associated ACHM.

METHODS

High-resolution imaging (optical coherence tomography [OCT] and adaptive optics scanning light ophthalmoscopy [AOSLO]) was performed in 51 subjects with CNGB3-associated ACHM. Peak cone density and inter-cone spacing at the fovea was measured using split-detection AOSLO. Foveal outer nuclear layer thickness was measured in OCT images, and the integrity of the photoreceptor layer was assessed using a previously published OCT grading scheme.

RESULTS

Analyzable images of the foveal cones were obtained in 26 of 51 subjects, with nystagmus representing the major obstacle to obtaining high-quality images. Peak foveal cone density ranged from 7,273 to 53,554 cones/mm2, significantly lower than normal (range, 84,733-234,391 cones/mm2), with the remnant cones being either contiguously or sparsely arranged. Peak cone density was correlated with OCT integrity grade; however, there was overlap of the density ranges between OCT grades.

CONCLUSIONS

The degree of residual foveal cone structure varies greatly among subjects with CNGB3-associated ACHM. Such measurements may be useful in estimating the therapeutic potential of a given retina, providing affected individuals and physicians with valuable information to more accurately assess the risk-benefit ratio as they consider enrolling in experimental gene therapy trials. (www.clinicaltrials.gov, NCT01846052.).

Understanding disability glare: light scatter and retinal illuminance as predictors of sensitivity to contrast

The presence of a bright light in the visual field has two main effects on the retinal image: reduced contrast and increased retinal illuminance because of scattered light; the latter can, under some conditions, lead to an improvement in retinal sensitivity. The combined effect remains poorly understood, particularly at low light levels. A psychophysical flicker-cancellation test was used to measure the amount and angular distribution of scattered light in the eye for 40 observers. Contrast thresholds were measured using a functional contrast sensitivity test. Pupil-plane glare-source illuminances (i.e., 0, 1.35, and 19.21  lm/m2), eccentricities (5°, 10°, and 15°), and background luminances (1, 2.6, and 26  cd/m2) were investigated. Visual performance was better than predicted, based on a loss of retinal image contrast caused by scattered light, particularly in the mesopic range. Prediction accuracy improved significantly when the expected increase in retinal sensitivity in the presence of scattered light was also incorporated in the model.

Comparison of objective outcomes following laparoscopic Nissen fundoplication versus laparoscopic gastric bypass in the morbidly obese with heartburn

BACKGROUND

Heartburn and gastroesophageal reflux disease (GERD) affects approximately 25-50% of morbidly obese patients. Although objective physiologic testing has been reported extensively in patients following Nissen fundoplication, there are no previous reports of such testing in morbidly obese patients. A life-saving surgical alternative for the morbidly obese patient is gastric bypass surgery, which usually improves heartburn symptoms in addition to many serious health conditions such as diabetes, hypertension, and sleep apnea. We hypothesized that, in morbidly obese patients, gastric bypass surgery would be as effective as Nissen fundoplication in reducing both heartburn symptoms and esophageal acid exposure, as reflected by the DeMeester score.

METHODS

Between 1995 and 2000, all patients undergoing laparoscopic Nissen fundoplication (LN) and laparoscopic gastric bypass (LGB) in our practice underwent preoperative and postoperative esophageal physiologic testing. Patients were included in this study that were morbidly obese and had significant heartburn symptoms or objective evidence of acid reflux, and had repeat esophageal physiologic testing after either LN or LGB. Data were obtained through retrospective review of prospectively collected data.

RESULTS

Twelve patients met the inclusion criteria: six patients who had LN and six who had LGB. The mean body mass index (BMI) was 55 kg/m2 in the LGB group and 39.8 in the LN group. After surgery, the mean DeMeester score decreased from 64.3 to 2.8 in the LN group ( p = 0.01) and from 34.7 to 5.7 in the LGB group ( p = 0.1). Both groups' mean postoperative DeMeester scores were normal after surgery, and there was no significant difference between the two groups ( p = 0.3). Both groups experienced a significant improvement in heartburn symptoms postoperatively. The mean preoperative symptom score improved from 3.5 to 0.5 in the LN group ( p = 0.01) and from 2.2 to 0.2 in the LGB group ( p = 0.003). There was no difference in the mean postoperative symptom scores between the groups ( p = 0.35). After surgery, mean LES resting pressures increased from 12.9 to 35.5 ( p = 0.003) in the LN group and from 23.6 to 29.7 ( p = 0.45) in the LGB group. There were no complications in either group.

CONCLUSION

Results of this study show that laparoscopic gastric bypass and laparoscopic Nissen fundoplication are both effective in treating heartburn symptoms and objective acid reflux in morbidly obese patients. The health benefits of weight loss after laparoscopic gastric bypass should make this operation the procedure of choice in the morbidly obese patient with heartburn.

Surgical staplers for vascular control of hepatic veins and portal structures in major hepatic resection

Phenomenal progress has occurred in the art of liver resection. Only a decade ago massive blood transfusion, liver failure, bile leak, or sepsis were alI frequent attendants of major resection, and intraoperative death from torrential bleeding from hepatic veins or vena cava was not uncommon. Now, major liver resection may be accomplished routinely without blood transfusion, and operative mortality of 0% to 2% is standard in expert hands. Uncontrolled hemorrhage remains the primary cause of intraoperative death. Mortality in the early postoperative period is usually related to delayed hemorrhage, inadequate hepatic reserve, or injury to vital blood supply or biliary drainage in the liver remnant.

Veno-veno bypass of the inferior vena cava in trauma, tumor, and transplantation

Interrupting the venous return from below the diaphragm is usually associated with sudden hypotension, hypovolemic cardiac failure, and increased bleeding secondary to acute venous hypertension and hepatic congestion. Shaw, Starzl, and Griffith developed a veno-veno bypass technique to shunt the somatic and splanchnic venous return around the retrohepatic vena cava to the superior vena cava. This permitted continuation of venous return and simultaneous blood warming, allowing surgeons to perform complex procedures in a dry operative field. These bypass techniques have evolved since their introduction in the 1980s and are now being applied for the removal of otherwise nonresectable tumors of the liver, adrenal gland, and kidney. Further, traumatic injuries to the hepatic veins and the retrohepatic cava associated with a high mortality rate can be repaired safely using vascular isolation techniques and bypass.

Laparoscopic pancreatic resection: single-institution experience of 19 patients

BACKGROUND

The number of laparoscopic pancreatic resections reported in the surgical literature has been remarkably low. Few substantive data are available concerning current indications and outcomes after laparoscopic pancreatectomy. The purpose of this article is to review the recent indications, complications, and outcomes after laparoscopic pancreatic resection.

STUDY DESIGN

A retrospective analysis of the Mount Sinai hospital records was performed for all patients who underwent laparoscopic distal pancreatectomy or enucleation between the time of the first resection in November 1993 until the time of this study in March 2000.

RESULTS

In the 19 patients (6 men) the mean age was 53 years (range 22 to 83 years). In 16 patients (84%) the entire procedure was done by laparoscopy; one operation was converted to a hand-assisted technique; and two cases were converted to open. Median operating time was 4.4 hours (range 1.6 to 6.6 hours), and median intraoperative blood loss was 200 mL. Postoperative complications included three pancreatic leaks (16%), one case of superficial phlebitis, and one prolonged ileus for 7 days (total morbidity of 26%). There were no deaths. The median length of postoperative hospital stay was 6 days (range 1 to 26 days).

CONCLUSIONS

This represents the largest single-institution experience with laparoscopic pancreatic resection. The considerable morbidity rate is comparable to recently published open series, and is likely inherent in pancreatic surgery, rather than the technical approach. Laparoscopic pancreatic surgery resulted in shorter hospital stays and appears to be safe for benign diseases.

Effect of an esophageal bougie on the incidence of dysphagia following nissen fundoplication: a prospective, blinded, randomized clinical trial

HYPOTHESIS

Based on retrospective, uncontrolled studies, it has been claimed that Nissen fundoplication should be performed over an esophageal bougie to minimize postoperative dysphagia. We hypothesized that a surgeon experienced in laparoscopic fundoplication will have similar rates of postoperative dysphagia whether or not an esophageal bougie is used.

DESIGN

A patient and observer blinded, randomized, prospective clinical trial to assess the effect of intraoperative bougie use.

SETTING

A tertiary care teaching hospital that is a regional referral source for complex laparoscopic foregut surgical procedures.

PATIENTS

Three hundred thirty-six consecutive patients referred for laparoscopic fundoplication between March 1, 1996, and July 31, 1998, were evaluated for eligibility based on inclusion criteria and, if applicable, were offered randomization for fundoplication with or without a 56F bougie. One hundred seventy-one patients were enrolled in this study.

INTERVENTIONS

All patients underwent laparoscopic Nissen fundoplication, 81 with a bougie (hereafter referred to as the bougie group) and 90 without a bougie (hereafter referred to as the no bougie group).

MAIN OUTCOME MEASURES

Dysphagia severity and frequency were assessed by a blinded observer using a standardized scoring system. Incidence of complications related to the use or absence of a bougie, operative times, and postsurgical recovery was also assessed.

RESULTS

The mean operating time was 148 minutes (range, 65-295 minutes). The overall operative morbidity was 9% (7. 4% in the bougie group and 11% in the no bougie group, P=.41). One esophageal injury (1.2%) occurred in the bougie group. The 30-day mortality was 0. Long-term dysphagia assessment was completed in 90% of patients, with a mean follow-up of 11 months. Overall, long-term postoperative dysphagia was present in 13 patients (17%) in the bougie group and 24 patients(31%) in the no bougie group (P=.047). Severe dysphagia occurred in 5% of patients in the bougie group and 14% in the no bougie group.

CONCLUSION

This study confirms the dogma that use of a large-caliber stent during the creation of a fundoplication decreases the long-term incidence of dysphagia; albeit at the risk of injury from the introduction of a bougie.

Radiofrequency ablation followed by resection of malignant liver tumors

BACKGROUND

Radiofrequency ablation (RFA) has recently been used to treat liver tumors, but few clinical reports have described the pathological characteristics of radiofrequency ablation in human specimens. This study delineates the gross pathologic and histochemical changes induced by RFA in benign and malignant human liver tissue and confirms the tumor necrosis described in early clinical reports.

METHODS

Ten patients with metastatic tumors of the liver received a single treatment of ultrasound-guided percutaneous RFA to 12 tumors. Hepatic resection was carried out within 6 weeks of RFA. Specimens were stained with standard hematoxylin and eosin stain followed by oxidative stain to determine if there was evidence of viable tumor within the zone of ablation.

RESULTS

Nine of the 12 ablations were resected. Microscopic examination within the zone of ablation showed successful ablation in 8 of the 9 resected ablations.

CONCLUSIONS

Percutaneous RFA creates well-circumscribed areas of tumor necrosis with apparent cell death using an oxidative stain. Further investigation is encouraged to determine the clinical effectiveness of radiofrequency ablation in the complete destruction of liver tumors for palliative or curative intent.

Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion size

OBJECTIVE

To determine, in vivo, the effect of radiofrequency ablation (RFA) treatment time and tissue blood flow on the size and shape of the resulting necrotic lesion in porcine liver.

SUMMARY BACKGROUND DATA

Radiofrequency ablation is an electrosurgical technique that uses a high frequency alternating current to heat tissues to the point of desiccation (thermal coagulation). Radiofrequency ablation is well established as the treatment of choice for many symptomatic cardiac arrhythmias because of its ability to create localized necrotic lesions in the cardiac conducting system. Until recently, a major limitation of RFA was the small lesion size created by this technique. Development of bipolar and multiple-electrode RFA probes has enabled the creation of larger lesions and therefore has expanded the potential clinical applications of RFA, which includes the treatment of liver tumors. A basic understanding of factors that influence RFA lesion size in vivo is critical to the success of this treatment modality. The optimal RFA technique, which maximizes liver lesion size, has yet to be determined. Theoretically, lesion size varies directly with time of application of the RF current, and inversely with blood flow, but these relationships have not been previously studied in the liver.

METHODS

Six animals underwent hepatic RFA (460 kHz), for 5, 7.5, 10, 12.5, 15, and 20 minutes. Identical, predetermined anatomic areas of the liver were ablated in each animal. Two additional animals underwent 12 RFA treatments -- 6 with vascular inflow occlusion (Pringle maneuver) and 6 with uninterrupted hepatic blood flow. Animals were euthanized and the livers were removed for gross pathologic examination. All lesions were measured in three dimensions and photographed. Tissues were examined by routine histology and by histochemistry to determine viability.

RESULTS

Increasing duration of RFA application from 5 through 20 minutes did not create lesions of larger diameter, but this time increase did predict deeper lesion production (beta = 0.34, p = 0.04). A range of lesion shapes were created from four separate ovals (corresponding to each electrode), to larger ovals intersecting to form a cross, to spheroid lesions. The number of blood vessels in close proximity to the probe tip (within a 1-cm radius from the center of the lesion) strongly predicted minimum lesion diameter (beta = -0.61, p = 0.0001) and lesion volume (beta = -0.56, p = 0.0004). This negative effect of blood flow on lesion size was confirmed experimentally. Radiofrequency ablation lesions created during a Pringle maneuver were significantly larger in all three dimensions than lesions created without a Pringle maneuver: minimum diameter was 3.0 cm (with Pringle) versus 1.2 cm (p = 0.002), maximum diameter was 4.5 cm (with Pringle) versus 3.1 cm (p = 0.002), depth was 4.8 cm (with Pringle) versus 3.1 cm (p < 0.001), and lesion volume was 35.0 cm3 (with Pringle) versus 6.5 cm3 (p < 0.001).

CONCLUSIONS

Blood flow is a strong predictor of all RFA lesion dimensions in porcine liver in vivo, whereas a change of treatment time from 5 to 20 minutes is predictive only of lesion depth, but not diameter or volume.

Don't cry over spilled stones? Complications of gallstones spilled during laparoscopic cholecystectomy: case report and literature review

The gallbladder is perforated and stones are spilled more frequently during laparoscopic cholecystectomy than during open cholecystectomy. Recent reports have implicated spilled gallstones as a source of infrequent but serious complications of laparoscopic of laparoscopic cholecystectomy. They can cause serious morbidity, and in most cases the patient will require open surgery for management of these complications. The authors report the case of a patient who was ill for 14 months after laparoscopic cholecystectomy when spilled stones formed a nidus for intra-abdominal abscess and colocutaneous fistula. Every effort must be made to prevent gallbladder perforation. When it does occur, all stones should be retrieved. Attempts at repairing gallbladder perforations are often unsatisfactory. A simple solution to this potential problem is to retrieve all stones immediately, place them in an intraperitoneal specimen bag, and "park" the bag on the liver. As soon as the gallbladder is dissected off the liver it should be placed in the specimen bag with the stones and removed through the umbilical port opening.

Liver tumor ablation techniques

Despite advances in surgical technique, patients with primary and secondary liver tumors remain a difficult management problem, as most tumors are unresectable at presentation. Alternative therapies, involving the in situ destruction of liver tumors, have recently come under scrutiny as palliative options. Percutaneous ethanol injection and cryosurgery have been advocated, but both have associated technical difficulties and adverse effects. Novel liver tumor ablation techniques have recently been developed that work via the induction of localized hyperthermia. There is mounting evidence to support a hypothesis that cancer cells are more selectively sensitive to heat than are normal cells, due to the poor blood supply of neoplastic tissue and the decreased vasodilatation capacity of the neovascular bed. These ablative modalities induce a variable degree of tumor necrosis in unresectable tumors, and therefore may provide useful palliation. Clinical trials are needed to determine the true nature and degree of any palliative benefit. In addition, the determinants of treatment efficacy and the predictability of the necrotic zone must be better understood before these techniques can be contemplated as alternatives to liver resection for cure.

Radiofrequency ablation in surgery

Recently, hyperthermia has been employed clinically as one of a variety of multimodal therapies for cancer. Hyperthermia has been applied locally, regionally, and systemically to various tumors. Local or regional hyperthermia has the advantage that a localized tumor can be heated to temperatures higher than 420 C, the maximum for total-body hyperthermia. There is mounting evidence to support a hypothesis that cancer cells are more selectively sensitive to heat than are normal cells, due to the poor blood supply of neoplastic tissue and the decreased vasodilatation capacity of the neovascular bed.

An alternative approach to acute cholecystitis. Percutaneous cholecystostomy and interval laparoscopic cholecystectomy

BACKGROUND

The mainstay of therapy for acute cholecystitis is cholecystectomy, which has a mortality of 5-30% in high-risk patients such as the elderly or critically ill. An alternative treatment option in patients suffering from acute cholecystitis with contraindications to emergency surgery is percutaneous cholecystostomy (PC) followed by interval laparoscopic cholecystectomy. Percutaneous cholecystostomy yields 10-12% mortality in high-risk patients and is therefore a safe temporizing measure, allowing delayed, elective cholecystectomy when the patient is in better condition for surgery.

METHODS

Hospital charts and radiology films were reviewed for all 50 patients who underwent PC for acute cholecystitis between January 1990 and September 1993. Most patients were high risk for emergency cholecystectomy by virtue of their critical illness or underlying medical condition. Twenty-five patients went on to have interval cholecystectomies. We recorded whether they underwent laparoscopic or open cholecystectomy, as elective or emergency procedures, and we recorded direct complications, mortality, and postoperative length of hospital stay.

RESULTS

Relief of symptoms occurred within 48 h of PC in 90% of patients, and two patients had complications of PC. Laparoscopic cholecystectomy was attempted in 13 patients and competed in nine. Four patients (31%) required conversion from laparoscopic to open cholecystectomies due to extensive adhesions (3) or bleeding (1). Three patients had direct complications of laparoscopic cholecystectomy. There was no mortality or major bile duct injury.

CONCLUSION

Percutaneous cholecystostomy followed by interval laparoscopic cholecystectomy is a safe, minimally invasive approach which can be employed safely in the critically ill patient when contraindications to emergency surgery exist.

Radiologically guided percutaneous cholecystostomy for acute cholecystitis: long-term outcome in 50 patients

To assess the long-term outcome in patients with acute cholecystitis treated initially by percutaneous cholecystostomy, the authors reviewed the medical and radiology records of all such patients treated at their hospital from January 1990 to September 1993. Of the 50 patients, 29 had calculous and 21 had acalculous cholecystitis. In the group with calculous cholecystitis, 1 of the patients required no further treatment, 3 subsequently underwent percutaneous stone removal, 14 underwent elective cholecystectomy, 6 underwent emergency cholecystectomy and 5 died of the underlying condition shortly after cholecystostomy. In the group with acalculous cholecystitis, 12 of the patients needed no further treatment after a mean follow-up period of 12 months; 8 of these underwent follow-up ultrasound examination, which revealed gallbladder calculi in only 1 patient. Four patients underwent elective cholecystectomy, 1 underwent emergency cholecystectomy, and 4 died of the underlying condition shortly after cholecystostomy. Over the long term, 23 (79%) of the 29 patients with calculous cholecystitis underwent surgery or removal of calculi. In the other group surgery was required in only 5 (24%) of the 21 patients. The authors conclude that percutaneous cholecystostomy is a useful temporizing measure, which allows patients with calculous cholecystitis to undergo elective cholecystectomy. In most cases of acalculous cholecystitis the procedure is curative, obviating the need for cholecystectomy.

Multiple clones with (3;21) translocation in a case of Ph-positive chronic myelogenous leukemia during relapse after allogeneic bone marrow transplantation

Secondary chromosome changes are frequently observed during the blastic phase of chronic myelogenous leukemia (CML) owing to clonal evolution. Both numerical and structural abnormalities are reported in most of these cases. Recently a new translocation, t(3;21)(q26;q22), was reported in Philadelphia (Ph)-positive CML during the chronic as well as accelerated phase. We report a patient with Ph-positive CML who developed three abnormal clones, all of which had t(3;21) at the time of relapse after allogeneic bone marrow transplantation during the accelerated phase.