The effect of axial length on pseudophakic retinal detachment.

PURPOSE: The purpose of the study was to analyse the surgical management and outcome regarding axial length in the population affected by pseudophakic retinal detachment (PRD) 2015-2020. METHOD: The patients included were from an observational cohort study of patients undergoing cataract surgery in the region of Skåne during 2015-2017. Data were retrieved from the Swedish National Cataract Register and cross-referenced with cases of PRD in the same region from 2015 to 2020. The surgical method used and findings at follow-up were recorded. The patients were stratified according to axial length (AL) to <25 mm, 25 ≤ n < 26.5 mm and ≥26.5 mm. The main outcome was primary success with one surgery apart from silicone oil removal. The secondary outcome was postoperative visual acuity. RESULTS: In the whole study group of 58 624 cases, complete follow-up data were available for 288 eyes. The median follow-up time was 324 days, and primary operation was successful in 82.9% of these cases. The median visual acuity was 0.31 (LogMAR). In the stratification those with AL < 25 mm had a primary success of 75.8%, AL 25 ≤ n < 26.5 mm of 87.9% and ≥26.5 mm of 95.8%. CONCLUSIONS: The primary anatomical success was 82.9% in the whole group of PRD but with stratification they had an increasing number of primary success with longer AL.

Functional and molecular 3D mapping of angiosarcoma tumor using non-invasive laser speckle, hyperspectral, and photoacoustic imaging.

PURPOSE: The gold standard for skin cancer diagnosis is surgical excisional biopsy and histopathological examination. Several non-invasive diagnostic techniques exist, although they have not yet translated into clinical use. This is a proof-of-concept study to assess the possibility of imaging an angiosarcoma in the periocular area. METHODS: We use laser speckle, hyperspectral, and photoacoustic imaging to monitor blood perfusion and oxygen saturation, as well as the molecular composition of the tissue. The information obtained from each imaging modality was combined in order to yield a more comprehensive picture of the function, as well as molecular composition of a rapidly growing cutaneous angiosarcoma in the periocular area. RESULTS: We found an increase in perfusion coupled with a reduction in oxygen saturation in the angiosarcoma. We could also extract the molecular composition of the angiosarcoma at a depth, depicting both the oxygen saturation and highlighting the presence of connective tissue via collagen. CONCLUSIONS: We demonstrate the different physiological parameters that can be obtained with the different techniques and how these can be combined to provide detailed 3D maps of the functional and molecular properties of tumors useful in preoperative assessment.

Forehead flap perfusion monitored by laser speckle contrast imaging: Importance of flap length and thickness.

Purpose: Forehead flaps are commonly used in oculoplastic surgery to cover defects after tumor excision. Blood perfusion is vital for flap survival. The aim of this study was to monitor the perfusion in forehead flaps and investigate the impact of flap length and thickness. Methods: Nineteen forehead flaps in patients undergoing direct brow lift were studied. Perfusion was monitored using laser speckle contrast imaging, immediately after raising flaps consisting of epidermis, dermis, and subcutaneous tissue, and after removing the subcutaneous tissue resulting in a thin flap. Results: Perfusion decreased gradually along the length, the mean value being 44% at 5 mm and 26% at 15 mm from the base, in thick flaps. Perfusion was significantly lower in thin flaps, being 13% when measured 15 mm from the flap base (p < 0.0024). Perfusion was better preserved in thick than in thin flaps. Very low perfusion was observed 16.7 mm (16.0-17.3 mm) from the base in thick flaps, and from 10.2 mm (9.8-10.6 mm) from the base in thin flaps (p < 0.0001). Conclusions: Flap thickness is important in maintaining adequate blood perfusion and thus increasing the probability of flap survival. This may be particularly important in long flaps and in patients with impaired microcirculation.

The effect of traction force on eyelid blood perfusion during closure of defects.

PURPOSE: In oculoplastic surgery the eyelid tissue is frequently stretched in order to repair defects after tumor surgery. However, there is a paucity of research regarding how stretching affects eyelids. The purpose of this study was to gain insight into how traction force affects eyelid stretch as well as tissue perfusion, using a laser-based in vivo monitoring technique. METHOD: Lower-lid pentagonal resections were performed in eight patients and a total of nine eyelids. The medial section of the eyelid was then stretched using a dynamometer up to a force of 2.3 Newtons (N), and eyelid stretching and blood perfusion were continuously measured using laser speckle contrast imaging. RESULTS: Tissue perfusion decreased exponentially when eyelid tissue was stretched, with an initial sharp decline followed by a more gradual reduction. Perfusion approached zero at a force of approximately 2.0 N. The length of the eyelid increased with increasing force up to 1.5 N, after which there was only a very slight increase in length. CONCLUSIONS: Eyelid tissue seems to respond to traction in a non-linear fashion, where the initial force results in the greatest eyelid stretching and reduction in blood perfusion. The results provide information on the effects of a large force for direct closure of large eyelid defects. Considering how quickly perfusion approaches zero, the high success rate of eyelid reconstruction surgery is likely a testament to the extensive vascularization of the periocular region.

Optimizing clinical O2 saturation mapping using hyperspectral imaging and diffuse reflectance spectroscopy in the context of epinephrine injection.

Clinical determination of oxygen saturation (sO2) in patients is commonly performed via non-invasive optical techniques. However, reliance on a few wavelengths and some form of pre-determined calibration introduces limits to how these methods can be used. One example involves the assessment of sO2 after injection of local anesthetic using epinephrine, where some controversy exists around the time it takes for the epinephrine to have an effect. This is likely caused by a change in the tissue environment not accounted for by standard calibrated instruments and conventional analysis techniques. The present study aims to account for this changing environment by acquiring absorption spectra using hyperspectral imaging (HSI) and diffuse reflectance spectroscopy (DRS) before, during, and after the injection of local anesthesia containing epinephrine in human volunteers. We demonstrate the need to account for multiple absorbing species when applying linear spectral unmixing in order to obtain more clinically relevant sO2 values. In particular, we demonstrate how the inclusion of water absorption greatly affects the rate at which sO2 seemingly drops, which in turn sheds light on the current debate regarding the time required for local anesthesia with epinephrine to have an effect. In general, this work provides important insight into how spectral analysis methods need to be adapted to specific clinical scenarios to more accurately assess sO2.

Comparison of perimetric 24-2 and 30-2 test patterns in detecting visual field defects in patients with tumours in the pituitary region.

PURPOSE: Automated perimetry provides a standardized method of measuring the visual field. The Humphrey Field Analyser (HFA) uses the 24-2 test pattern to cover 24 degrees centrally or the 30-2 test pattern to cover a slightly broader region of 30 degrees. The aim of this study was to determine whether the 24-2 test pattern provides comparable information to the 30-2 test pattern in detecting visual field defects in patients with tumours in the pituitary region. METHODS: A retrospective cohort study was carried out on patients with tumours in the pituitary region and radiologically confirmed compression of the visual pathway. Included patients (79 of 133) had been examined using the Humphrey 30-2 visual field test, after which the 30-2 test patterns were reduced into corresponding 24-2 test patterns. The location of visual field defects, visual acuity and the perimetric parameters mean deviation (MD) and visual field index (VFI) were also recorded. RESULTS: No patient was classified differently when evaluated with the 24-2 test pattern, compared to the 30-2 test pattern. Interestingly, although the majority of patients had visual field defects located in the temporal visual field of each eye, a significant minority did not. In addition, it was found that a large proportion of patients had normal visual acuity (≥0.8). CONCLUSIONS: The use of the HFA 24-2 test pattern reliably detected visual field defects in patients with tumours in the pituitary region. The present study indicates that MD and VFI are not reliable parameters for evaluating visual field defects due to compression.

Breast Cancer Diagnosis Using Extended-Wavelength-Diffuse Reflectance Spectroscopy (EW-DRS)-Proof of Concept in Ex Vivo Breast Specimens Using Machine Learning.

This study aims to investigate the feasibility of using diffuse reflectance spectroscopy (DRS) to distinguish malignant breast tissue from adjacent healthy tissue, and to evaluate if an extended-wavelength range (450-1550 nm) has an advantage over the standard wavelength range (450-900 nm). Multivariate statistics and machine learning algorithms, either linear discriminant analysis (LDA) or support vector machine (SVM) are used to distinguish the two tissue types in breast specimens (total or partial mastectomy) from 23 female patients with primary breast cancer. EW-DRS has a sensitivity of 94% and specificity of 91% as compared to a sensitivity of 40% and specificity of 71% using the standard wavelength range. The results suggest that DRS can discriminate between malignant and healthy breast tissue, with improved outcomes using an extended wavelength. It is also possible to construct a simple analytical model to improve the diagnostic performance of the DRS technique.

Visual Acuity Prior to Cataract Surgery and Risk of Retinal Detachment - A Population-Based Study.

Purpose: To analyze preoperative visual acuity before cataract surgery regarding the risk of rhegmatogenous retinal detachment (RRD) after cataract surgery. Methods: The preoperative visual acuity in an observational cohort study of patients undergoing cataract surgery in Skåne, southern Sweden, during 2015-2017 was analyzed with data retrieved from the Swedish National Cataract Register. This was then cross-referenced with patients undergoing surgery for retinal detachment at the Skåne University Hospital in Lund from 2015 to 2020. The main outcome was the risk-benefit ratio of measuring preoperative visual acuity before cataract surgery and the risk of RRD. Results: The mean visual acuity in the whole study group (N=58,624), expressed as LogMAR, was 0.40 ± 0.32 (SD). In the group with RRD (n=298), the mean visual acuity was 0.44 ± 0.36 (p=0.07). In the subgroups of RRD, those aged <60 years 0.49 ± 0.44 (p=0.07), aged <60 years and axial length (AL) >25 mm 0.42 ± 0.38 (p=0.68), and in those aged <60 years, AL >25 mm and male sex 0.44 ± 0.39 (p=0.53). However, there is considerable variations in visual acuity of the various groups and in the high-risk group with RRD aged <60 years with AL>25 mm, 15% had a visual acuity of 0.8 or better in the operated eye. Conclusion: There must be strong indications for performing cataract surgery in those with a high risk of retinal detachment, and the patient must be given adequate information on the risk of retinal detachment.

Oxygen saturation mapping during reconstructive surgery of human forehead flaps with hyperspectral imaging and spectral unmixing.

BACKGROUND: Optical spectroscopy is commonly used clinically to monitor oxygen saturation in tissue. The most commonly employed technique is pulse oximetry, which provides a point measurement of the arterial oxygen saturation and is commonly used for monitoring systemic hemodynamics, e.g. during anesthesia. Hyperspectral imaging (HSI) is an emerging technology that enables spatially resolved mapping of oxygen saturation in tissue (sO2), but needs to be further developed before implemented in clinical practice. The aim of this study is to demonstrate the applicability of HSI for mapping the sO2 in reconstructive surgery and demonstrate how spectral analysis can be used to obtain clinically relevant sO2 values. METHODS: Spatial scanning HSI was performed on cutaneous forehead flaps, raised as part of a direct brow lift, in eight patients. Pixel-by-pixel spectral analysis, accounting for the absorption from multiple chromophores, was performed and compared to previous analysis techniques to assess sO2. RESULTS: Spectral unmixing using a broad spectral range, and accounting for the absorption of melanin, fat, collagen, and water, provided a more clinically relevant estimate of sO2 than conventional techniques, where typically only spectral features associated with absorption of oxygenated (HbO2) and deoxygenated (HbR) hemoglobin are considered. We demonstrate its clinical applicability by generating sO2 maps of partially excised forehead flaps showed a gradual decrease in sO2 along the length of the flap from 95 % at the flap base to 85 % at the flap tip. After being fully excised, sO2 in the entire flap decreased to 50 % within a few minutes. CONCLUSIONS: The results demonstrate the capability of sO2 mapping in reconstructive surgery in patients using HSI. Spectral unmixing, accounting for multiple chromophores, provides sO2 values that are in accordance with physiological expectations in patients with normal functioning microvascularization. Our results suggest that HSI methods that yield reliable spectra are to be preferred, so that the analysis can produce results that are of clinical relevance.

Laser speckle contrast imaging enables perfusion monitoring of the anterior segment during strabismus surgery: a study on the horizontal rectus muscles.

BACKGROUND: A dreaded complication of strabismus surgery is anterior segment ischaemia (ASI), caused by damage to the anterior ciliary arteries. To avoid ASI, a maximum of two rectus muscles are operated on at a time. However, these surgical protocols are based on empirical observations of clinical outcome, rather than objective perfusion measurements. There is no method available for perioperative, real-time perfusion measurements during ocular muscle surgery. The aims of this study were to investigate whether laser speckle contrast imaging (LSCI) could be used for such measurements, and to monitor perfusion during strabismus surgery on one or two horizontal rectus muscles. METHODS: Forty-four eyes in 44 patients with horizontal strabismus underwent corrective surgery involving medial and/or lateral rectus muscle detachment. Perfusion in the adjacent paralimbal and iris tissue was monitored with LSCI. RESULTS: When the first horizontal rectus muscle was detached perfusion in the adjacent paralimbal tissue decreased by 23% (p<0.0001), and by 12% (p<0.0001) when the second muscle was detached. The iris perfusion decreased by 5% (p<0.05) when the first muscle was detached but showed no significant decrease as the second muscle was cut. CONCLUSION: This is the first study showing that perfusion of the anterior segment can be monitored non-invasively with LSCI during strabismus surgery. In this cohort, two horizontal rectus muscles were detached with only a small decrease in the anterior segment circulation. Future studies are required for complete mapping of the effect of surgery on multiple ocular muscles on the anterior segment circulation.

Detailed measurements of the four extraocular rectus muscles' contribution to the perfusion of the anterior segment of the eye.

BACKGROUND/AIMS: Anterior segment ischaemia (ASI) is a rare but serious complication of strabismus surgery, which may be caused by damage to the anterior ciliary arteries that run along the rectus muscles. To avoid ASI, clinical praxis is to operate on a maximum of two rectus muscles at a time. The aim of this study was to perform a detailed study of the contribution of the four ocular rectus muscles to the perfusion of the anterior segment using laser speckle contrast imaging (LSCI). METHODS: The four rectus muscles were successively detached during enucleation in nine patients with suspected uveal melanoma. Perfusion of the anterior segment was monitored with LSCI during the detachment of each of the rectus muscles, and after the ophthalmic artery had been severed. RESULTS: Perfusion of the anterior segment, measured in the paralimbal tissue, decreased gradually as the four rectus muscles were detached, showing a decrease to 98% when the first (lateral rectus) muscle was detached, to 88% when the second (medial rectus), and 69% when the third (inferior rectus) muscles were detached. The decrease was more pronounced and statistically significant when the fourth (superior rectus) muscle was detached (to 28%, p=0.0102). CONCLUSION: LSCI is a valuable perfusion monitoring tool, as it has the capability to visualise the gradual decrease in anterior segment perfusion as the rectus muscles are successively detached. Further studies are needed to determine how many rectus muscles can be safely detached during strabismus surgery without risking ASI.

Mapping the architecture of the temporal artery with photoacoustic imaging for diagnosing giant cell arteritis.

Photoacoustic (PA) imaging is rapidly emerging as a promising clinical diagnostic tool. One of the main applications of PA imaging is to image vascular networks in humans. This relies on the signal obtained from oxygenated and deoxygenated hemoglobin, which limits imaging of the vessel wall itself. Giant cell arteritis (GCA) is a treatable, but potentially sight- and life-threatening disease, in which the artery wall is infiltrated by leukocytes. Early intervention can prevent complications making prompt diagnosis of importance. Temporal artery biopsy is the gold standard for diagnosing GCA. We present an approach to imaging the temporal artery using multispectral PA imaging. Employing minimally supervised spectral analysis, we produce histology-like images where the artery wall is clearly discernible from the lumen and further differentiate between PA spectra from biopsies diagnosed as GCA- and GCA+ in 77 patients.

Mapping of Perfusion During Full-Thickness Blepharotomy Using Laser Speckle Contrast Imaging.

PURPOSE: The aim of this study was to monitor how the blood perfusion in human upper eyelids is affected during full-thickness blepharotomy. METHODS: Seven eyelids in 5 patients with upper eyelid retraction due to Graves' disease underwent full-thickness blepharotomy. Perfusion was measured using laser speckle contrast imaging in the eyelid margin and in the conjunctival pedicle. RESULTS: Immediately following the procedure, a nonsignificant reduction in perfusion was observed in the skin of the pretarsal eyelid margin, being 66% of the initial value ( p = n.s.). However, a statistically significant decrease in perfusion, to 53% of the initial value ( p < 0.01), was seen in the central pedicle of the conjunctiva. There were no surgical complications such as infection, signs of ischemia, or bleeding. CONCLUSIONS: In this study, eyelid perfusion was mapped during full-thickness blepharotomy for the first time using laser speckle contrast imaging. The results showed that perfusion is sufficiently preserved during surgery, probably due to the rich vascular supply in the periocular region, which may explain the low risk of postoperative complications such as ischemia and infection.

Hyperspectral and Laser Speckle Contrast Imaging for Monitoring the Effect of Epinephrine in Local Anesthetics in Oculoplastic Surgery.

PURPOSE: Epinephrine is used in local anesthetics to induce vasoconstriction and thus reduce bleeding and prolong the anesthetic effect. Finding the optimal delay between the administration of the anesthetic and skin incision to ensure vasoconstriction and minimize bleeding is important and has recently become the subject of debate. This is the first study to assess blood perfusion and oxygen saturation (sO 2 ) simultaneously in response to a local anesthetic containing epinephrine in human oculoplastic surgery. METHODS: A local anesthetic consisting of lidocaine and epinephrine (20 mg/ml + 12.5 µg/ml) was injected in the eyelids of 9 subjects undergoing blepharoplasty. The perfusion and sO 2 of the eyelids were monitored using laser speckle contrast imaging and hyperspectral imaging, respectively. RESULTS: Laser speckle contrast imaging monitoring showed a decrease in perfusion over time centrally at the site of injection. Half-maximum effect was reached after 34 seconds, and full effect after 115 seconds, determined by exponential fitting. The drop in perfusion decreased gradually further away from the injection site and hypoperfusion was less prominent 4 mm from the injection site, with a spatially dependent half-maximum effect of 231 seconds. Hyperspectral imaging showed only a slight decrease in sO 2 of 11 % at the injection site. CONCLUSIONS: The optimal time delay for skin incision in oculoplastic surgery is approximately 2 minutes after the injection of lidocaine with epinephrine. Longer delay does not lead to a further decrease in perfusion. As sO 2 was only slightly reduced after injection, the results indicate that the use of epinephrine is safe in the periocular region.

Laser speckle contrast imaging enables perfusion monitoring of the anterior segment during eye muscle surgery.

We demonstrate that laser speckle contrast imaging can be used to monitor blood perfusion noninvasively during the detachment of ocular muscles, which may be a valuable tool for reducing the risk of anterior segment ischemia as a complication of strabismus surgery.

Retinal detachment after cataract surgery: a population-based study.

PURPOSE: To analyse the risk of rhegmatogenous retinal detachment (RRD) after cataract surgery, and to identify possible risk factors. METHOD: Observational cohort study of patients undergoing cataract surgery in Region Skåne, southern Sweden, during 2015-2017 were retrieved from the Swedish National Cataract Register. These were then cross-referenced with cases of retinal detachment surgery performed at the Skåne University Hospital in Lund from 2015 to 2020. The main outcome was RRD after cataract surgery. The influence of sex, age, axial length of the eye, rupture of the posterior capsule, patient comorbidity and other cataract complications were analysed. RESULTS: Among the 58 624 cases of cataract surgery, a total of 298 RRDs (0.51%) were identified up to the end of 2020. The mean time from cataract surgery to RRD was 667 days. The mean age was 65.3 years, compared to 74 years in the control group. A strong correlation was found between RDD and age: <60 years, incidence = 0.50%; 60-75 years, incidence = 0.14%; and >75 years, incidence = 0.04%. The correlation with axial length was also very strong: mean value 23.73 mm in those without RRD, and 25.13 mm in those with RRD (p < 0.001). Sex was also strongly correlated to RDD; 68.8% of cases of RRD being men. Among men younger than 60 years of age, with an axial length ≥25 mm, 9.46% exhibited RRD within the follow-up period (mean 4.7 years). Rupture of the posterior capsule was found in 2.01% of RRD patients compared to 0.74% in the control group. Diabetes, glaucoma or pseudoexfoliation had no impact on the prevalence of RRD. CONCLUSIONS: The three main risk factors for RRD following cataract surgery were found to be sex, age and axial length. The highest incidence of RRD (9.46%) were identified among men younger than 60 years of age and an axial length ≥25 mm.

Photoacoustic imaging of periorbital skin cancer ex vivo: unique spectral signatures of malignant melanoma, basal, and squamous cell carcinoma.

Radical excision of periorbital skin tumors is difficult without sacrificing excessive healthy tissue. Photoacoustic (PA) imaging is an emerging non-invasive biomedical imagi--ng modality that has potential for intraoperative micrographic control of surgical margins. This is the first study to assess the feasibility of PA imaging for the detection of periocular skin cancer. Eleven patients underwent surgical excision of periocular skin cancer, one of which was a malignant melanoma (MM), eight were basal cell carcinomas (BCCs), and two squamous cell carcinomas (SCCs). Six tumors were located in the eyelid, and five in periocular skin. The excised samples, as well as healthy eyelid samples, were scanned with PA imaging postoperatively, using 59 wavelengths in the range 680-970 nm, to generate 3D multispectral images. Spectral unmixing was performed using endmember spectra for oxygenated and deoxygenated Hb, melanin, and collagen, to iden--tify the chromophore composition of tumors and healthy eyelid tissue. After PA scanning, the tumor samples were examined histopathologically using standard hematoxylin and eosin staining. The PA spectra of healthy eyelid tissue were dominated by melanin in the skin, oxygenated and deoxygenated hemoglobin in the orbicularis oculi muscle, and collagen in the tarsal plate. Multiwavelength 3D scanning provided spectral information on the three tumor types. The spectrum from the MM was primarily reconstructed by the endmember melanin, while the SCCs showed contributions primarily from melanin, but also HbR and collagen. BCCs showed contributions from all four endmembers with a predominance of HbO2 and HbR. PA imaging may be used to distinguish different kinds of periocular skin tumors, paving the way for future intraoperative micrographic control.

Laser Speckle Contrast Imaging of the Blood Perfusion in Glabellar Flaps Used to Repair Medial Canthal Defects.

BACKGROUND: The glabellar flap is a common technique for surgical repair after tumor excision in the medial canthal area. However, the outcome may be affected by partial flap necrosis. Little is known about the impact of surgery on blood perfusion and the postoperative course of reperfusion due to the absence of reliable and noninvasive perfusion monitoring techniques. The aim of this study was to use a modern imaging technique to assess blood perfusion in glabellar flaps. METHODS: Glabellar flaps were used to repair medial canthal defects following tumor excision in 7 patients. Blood perfusion was monitored using laser speckle contrast imaging: during surgery, immediately postoperatively (0 weeks), and at follow-up, 1, 3, and 6 weeks after surgery. RESULTS: Perfusion decreased gradually along the length of the flap, and reached a minimum 15 mm from the flap base. Perfusion in the proximal 20 mm of the flap was completely restored after 1 week, while the distal part of the flap was gradually reperfused over 6 weeks. Both the functional and esthetic surgical outcomes were excellent. CONCLUSIONS: The rapid reperfusion of the glabellar flap may be explained by its connection to the vascular network via the flap pedicle. In flaps longer than 20 mm, the distal part can be considered a free skin transplant, and a combination of a glabellar flap and a free skin graft could then be considered.

Blood Perfusion of Human Upper Eyelid Skin Flaps Is Better in Myocutaneous than in Cutaneous Flaps.

BACKGROUND: The aim of this study was to monitor blood perfusion in human upper eyelid skin flaps and examine how the perfusion is affected by the thickness of the flap. METHODS: Twenty upper eyelids were dissected as part of a blepharoplasty procedure in patients. The medial end of the blepharoplasty flap remained attached to mimic a flap design often used in reconstruction in the periocular area, a myocutaneous flap in which the blood supply follows the fibers of the orbicularis muscle and is thus parallel to the long axis of the flap. The muscle was thereafter dissected from the flap to create a cutaneous flap. Blood perfusion in the 2 types of flaps was compared using laser speckle contrast imaging. RESULTS: Blood perfusion decreased gradually from the base to the tip of all the flaps. Perfusion was significantly higher in the myocutaneous flaps than in the cutaneous flaps (p < 0.0004): 69% in the myocutaneous flaps and 43% in the cutaneous flaps, measured 5 mm from the base. Blood perfusion was preserved to a greater extent distally in the myocutaneous flaps (minimum value seen at 25 mm) than in the cutaneous flaps (minimum seen at 11 mm). CONCLUSIONS: Blood perfusion was better preserved in myocutaneous flaps, including both skin and the orbicularis oculi muscle, than in cutaneous flaps. This may be of clinical interest in patients with poor microcirculation in which a long flap is required for reconstructive surgery.