FLUORESCENCE LIFETIME IMAGING OPHTHALMOSCOPY IN PATIENTS WITH MACULAR TELANGIECTASIA TYPE 2 WITH AND WITHOUT DIABETES.

PURPOSE: Macular telangiectasia type 2 (MacTel) is a vision-altering retinal disease with a high prevalence of diabetes. Differences between patients with MacTel with and without diabetes were investigated using fluorescence lifetime imaging ophthalmoscopy (FLIO). METHODS: Eighty-six patients with MacTel (59 ± 12 years) were included. 40 patients (46%) did not have diabetes, 16 patients (19%) were prediabetic, and 30 patients (35%) were diabetic. Of these, seven had diabetic retinopathy. 18 diabetic patients without MacTel and 42 age-matched healthy controls were included. FLIO lifetimes (FLTs) were obtained in short (SSC, 498-560 nm) and long (LSC, 560-720 nm) spectral channels from different areas of interest using a Heidelberg Engineering FLIO. RESULTS: Fundus autofluorescece lifetimes did not show significant differences when comparing diabetic with nondiabetic MacTel eyes (MacTel zone, SSC, diabetic: 243 ± 65 ps; nondiabetic: 232 ± 51 ps; P = 1.0; LSC, diabetic: 327 ± 66 ps; nondiabetic: 309 ± 54 ps; P = 0.582). Longitudinal changes were similarly unrelated to diabetes status. A nonsignificant trend of increased FLT progression with higher body mass index was found. Fundus autofluorescece lifetimes in diabetic patients without MacTel were significantly shorter within the MacTel zone and longer in the periphery compared with diabetic patients with MacTel. CONCLUSION: Although MacTel has a high prevalence of diabetes, FLTs from the MacTel zone are unrelated to diabetes. Fluorescence lifetime imaging ophthalmoscopy retains diagnostic abilities in patients with MacTel even in the presence of prediabetes, diabetes, and advanced diabetic retinopathy. The lack of diabetic FLT changes in the periphery of diabetic patients with MacTel is an interesting finding that needs further investigation.

LONGITUDINAL FLUORESCENCE LIFETIME IMAGING OPHTHALMOSCOPY ANALYSIS IN PATIENTS WITH MACULAR TELANGIECTASIA TYPE 2 (MacTel).

PURPOSE: Fluorescence lifetime imaging ophthalmoscopy (FLIO) shows characteristic patterns in macular telangiectasia Type 2 (MacTel). This study investigates FLIO changes over time to better understand disease progression. METHODS: Thirty-three patients with MacTel (age 60 ± 15 years) were followed at the Moran Eye Center with a prototype Heidelberg Engineering FLIO. The mean follow-up time was 19 ± 8 months (range 6-34 months). Fundus autofluorescence was excited at 473 nm, and FLIO lifetimes were recorded in in short (498-560 nm) and long (560-720 nm) spectral wavelengths channels. RESULTS: Autofluorescence lifetimes imaging ophthalmoscopy lifetimes from the MacTel area prolonged significantly over time (subfield T1, baseline: short spectral channel 210 ± 54 ps, long spectral channel 269 ± 58 ps; follow-up: short spectral channel 225 ± 59 ps, P < 0.001, long spectral channel 282 ± 64 ps, P < 0.01). The average 12-months prolongation of FLIO lifetimes was 9 ps (short spectral channel) and 8 ps (long spectral channel). Autofluorescence lifetimes changes correlated positively with ellipsoid zone loss and negatively with changes in retinal thickness. CONCLUSION: Autofluorescence lifetimes in MacTel slowly prolong over time, and temporal patterns progress to full rings. Detailed knowledge about FLIO changes will aid in understanding disease development and progression.

Comparing Fluorescence Lifetime Imaging Ophthalmoscopy in Atrophic Areas of Retinal Diseases.

Purpose: Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a non-invasive imaging modality to investigate the human retina. This study compares FLIO lifetimes in different degenerative retinal diseases. Methods: Included were eyes with retinal pigment epithelium (RPE) and/or photoreceptor atrophy due to Stargardt disease (n = 66), pattern dystrophy (n = 18), macular telangiectasia type 2 (n = 49), retinitis pigmentosa (n = 28), choroideremia (n = 26), and geographic atrophy (n = 32) in age-related macular degeneration, as well as 37 eyes of 37 age-matched healthy controls. Subjects received Heidelberg Engineering FLIO, autofluorescence intensity, and optical coherence tomography imaging. Amplitude-weighted mean FLIO lifetimes (τm) were calculated and analyzed. Results: Retinal FLIO lifetimes show significant differences depending on the disease. Atrophic areas in geographic atrophy and choroideremia showed longest mean FLIO lifetimes. τm values within areas of RPE and outer nuclear layer atrophy were significantly longer than within areas with preserved outer nuclear layer (P < 0.001) or non-atrophic areas (P < 0.001). Conclusions: FLIO is able to contribute additional information regarding differences in chronic degenerative retinal diseases. Although it cannot replace conventional autofluorescence imaging, FLIO adds to the knowledge in these diseases and may help with the correct differentiation between them. This may lead to a more in-depth understanding of the pathomechanisms related to atrophy and types of progression. Translational Relevance: Differences between atrophic retinal diseases highlighted by FLIO may indicate separate pathomechanisms leading to atrophy and disease progression.

Fluorescence lifetime imaging ophthalmoscopy: autofluorescence imaging and beyond.

Fluorescence lifetime imaging ophthalmoscopy, FLIO, has gained large interest in the scientific community in the recent years. It is a noninvasive imaging modality that has been shown to provide additional information to conventional imaging modalities. The FLIO device is based on a Heidelberg Engineering Spectralis system. Autofluorescence lifetimes are excited at 473 nm and recorded in two spectral wavelength channels, a short spectral channel (SSC, 498-560 nm) and a long spectral channel (LSC, 560-720 nm). Typically, mean autofluorescence lifetimes in a 30° retinal field are investigated. FLIO shows a clear benefit for imaging different retinal diseases. For example, in age-related macular degeneration (AMD), ring patterns of prolonged FLIO lifetimes 1.5-3.0 mm from the fovea can be appreciated. Macular telangiectasia type 2 (MacTel) shows a different pattern, with prolonged FLIO lifetimes within the typical MacTel zone. In Stargardt disease, retinal flecks can be appreciated even before they are visible with other imaging modalities. Early hydroxychloroquine toxicity appears to be detectable with FLIO. This technique has more potential that has yet to be discovered. This review article focuses on current knowledge as well as pitfalls of this technology. It highlights clinical benefits of FLIO imaging in different ophthalmic and systemic diseases, and provides an outlook with perspectives from the authors.

Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) in Patients with Choroideremia.

Purpose: To provide a detailed characterization of choroideremia (CHM) using fluorescence lifetime imaging ophthalmoscopy (FLIO) and to provide a deeper understanding of disease-related changes and progression. Methods: Twenty-eight eyes of 14 patients with genetically confirmed CHM (mean age, 28 ± 14 years) and 14 age-matched healthy subjects were investigated in this study. FLIO images of a 30° retinal field were collected at the Moran Eye Center using a Heidelberg Engineering FLIO device. FLIO lifetimes were recorded in short spectral channels (SSC; 498-560 nm) and long spectral channels (LSC; 560-720 nm), and mean autofluorescence lifetimes (τm) were calculated. Optical coherence tomography (OCT) scans were recorded for each patient. Three patients were re-imaged after a year. Results: Patients with CHM exhibit specific FLIO lifetime patterns. Prolonged FLIO lifetimes (around 600-700 ps) were found in the peripheral macula corresponding to atrophy in OCT imaging. In the central macula, τm was unrelated to autofluorescence intensity. Some areas of persistent retinal pigment epithelial islands had prolonged FLIO lifetimes, whereas other areas of hypofluorescence had short FLIO lifetimes. At 1-year follow-up, FLIO lifetimes were significantly prolonged within atrophic areas (P < 0.05). Conclusions: FLIO shows distinct patterns in patients with CHM, indicating lesions of atrophy and areas of preserved function in the presence or absence of findings in fundus autofluorescence intensity images. FLIO may provide differentiated knowledge about pathophysiology and atrophy progression in CHM compared to conventional imaging modalities. Translational Relevance: FLIO shows distinctive lifetime patterns that potentially identify areas of function, atrophy, and disease progression in patients with CHM.

Autofluorescence Lifetimes Measured with Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) Are Affected by Age, but Not by Pigmentation or Gender.

Purpose: Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a novel modality to investigate the human retina. This study aims to characterize the effects of age, pigmentation, and gender in FLIO. Methods: A total of 97 eyes from 97 healthy subjects (mean age 37 ± 18 years, range 9-85 years) were investigated in this study. This study included 47 (49%) females and 50 males. The pigmentation analysis was a substudy including 64 subjects aged 18 to 40 years (mean age 29 ± 6 years). These were categorized in groups A (darkly pigmented, 8), B (medium pigmented, 20), and C (lightly pigmented, 36). Subjects received Heidelberg Engineering FLIO and optical coherence tomography imaging. Retinal autofluorescence lifetimes were detected in two spectral channels (short spectral channel [SSC]: 498-560 nm; long spectral channel [LSC]: 560-720 nm), and amplitude-weighted mean fluorescence lifetimes (τm) were calculated. Additionally, autofluorescence lifetimes of melanin were measured in a cuvette. Results: Age significantly affected FLIO lifetimes, and age-related FLIO changes in the SSC start at approximately age 35 years, whereas the LSC shows a consistent prolongation with age from childhood. There were no gender- or pigmentation-specific significant differences of autofluorescence lifetimes. Conclusions: This study confirms age-effects in FLIO but shows that the two channels are affected differently. The LSC appears to show the lifelong accumulation of lipofuscin. Furthermore, it is important to know that neither gender nor pigmentation significantly affect FLIO lifetimes. Translational Relevance: This study helps to understand the FLIO technology better, which will aid in conducting future clinical studies.

FLUORESCENCE LIFETIME IMAGING OPHTHALMOSCOPY (FLIO) PATTERNS IN CLINICALLY UNAFFECTED CHILDREN OF MACULAR TELANGIECTASIA TYPE 2 (MACTEL) PATIENTS.

PURPOSE: Macular telangiectasia Type 2 (MacTel) is an inherited retinal disease following an autosomal dominant pattern with late onset and reduced penetrance. Fluorescence lifetime imaging ophthalmoscopy (FLIO) enhances diagnosis by showing distinct changes in MacTel. This study investigates FLIO-associated changes in clinically unaffected family members. METHODS: Eighty-one patients with MacTel (61 ± 12 years), 33 clinically healthy children under age 40 years of these MacTel patients (MacTel-C; 31 ± 6 years), 27 other family members (children over age 40 years, siblings, and parents) and 30 controls were investigated with the Heidelberg FLIO. All subjects underwent multimodal conventional imaging, including optical coherence tomography, blue-light reflectance, fluorescein angiography, and macular pigment imaging. RESULTS: All 81 patients with MacTel showed typical FLIO patterns. Of the 33 investigated MacTel-C with completely normal eye examinations and conventional imaging, 12 (36%) show FLIO patterns consistent with early MacTel. CONCLUSION: Prolonged FLIO lifetimes in the parafoveal area within the short spectral channel, especially temporally, are MacTel-specific. Fluorescence lifetime imaging ophthalmoscopy detects these lifetime patterns in over one-third of clinically unaffected MacTel-C. Although further studies will be necessary to determine the specificity of FLIO, it may help diagnose MacTel before conventional imaging modalities show changes or patients experience visual disturbances. Early detection may facilitate future gene discovery studies and interventional trials.

Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) in Eyes With Pigment Epithelial Detachments Due to Age-Related Macular Degeneration.

Purpose: To investigate fluorescence lifetime imaging ophthalmoscopy (FLIO) in neovascular AMD and pigment epithelial detachments (PEDs). Methods: A total of 46 eyes with PEDs (>350 µm) as well as age-matched healthy controls were included in this study. We found 28 eyes showed neovascular AMD (nvAMD), and 17 had nonneovascular (dry) AMD (dAMD). The Heidelberg Engineering FLIO excited fluorescence at 473 nm. Fluorescence decays were detected in two spectral channels (498-560 nm; 560-720 nm) to determine fluorescence lifetimes of endogenous fluorophores in their specific spectral emission ranges. Mean fluorescence lifetimes (τm) were investigated. Multimodal imaging was reviewed by two ophthalmologists who circumscribed and classified PEDs as either serous (n = 4), hemorrhagic (n = 4), fibrovascular (n = 16), drusenoid (n = 17), or mixed (n = 5). Blood samples from a healthy subject and a patient with PED were investigated in a quartz cuvette. Results: Eyes with nvAMD show similar FLIO patterns to dAMD: ring-shaped prolongations of τm 3 to 6 mm from the fovea. Different PED-forms show characteristic τm, while serous and hemorrhagic PEDs exhibit shortened τm, drusenoid PEDs show prolonged τm, and τm in fibrovascular PEDs is variable. Areas corresponding to sub-/intraretinal fluid display shortened τm. Ex vivo studies of blood also show short τm. Conclusions: The previously described dAMD-related FLIO pattern is also present in nvAMD. Short τm in serous, fibrovascular, and hemorrhagic PEDs as well as sub/intraretinal fluid may disrupt this pattern. FLIO appears to differentiate between PEDs, hemorrhage, and fluid. Additionally, ex vivo studies of human blood help to better interpret FLIO images.

Imaging of Hydroxychloroquine Toxicity with Fluorescence Lifetime Imaging Ophthalmoscopy.

PURPOSE: To investigate the impact of retinal toxicity from hydroxychloroquine (HCQ) on fundus autofluorescence lifetimes using fluorescence lifetime imaging ophthalmoscopy (FLIO). DESIGN: Cross-sectional study. PARTICIPANTS: Twenty-four eyes of 12 patients with definite HCQ toxicity, 31 eyes of 16 clinically normal patients at high risk of developing HCQ toxicity (taking HCQ longer than 5 years), and 16 eyes of 8 clinically normal patients at low risk of developing HCQ toxicity (taking HCQ fewer than 5 years), as well as 22 age-matched healthy subjects. METHODS: Fluorescence lifetime images of a 30° retinal field centered at the fovea were collected at the Moran Eye Center, Salt Lake City, Utah. A prototype Heidelberg Engineering Spectralis-based FLIO was used to detect autofluorescence lifetimes in short (SSC; 498-560 nm) and long (LSC; 560-720 nm) spectral channels. Mean fluorescence lifetimes were calculated. OCT scans and macular pigment measures were also recorded. Additionally, the autofluorescence lifetimes of HCQ were measured in a cuvette. MAIN OUTCOME MEASURES: Mean autofluorescence lifetimes (τm). RESULTS: All patients with HCQ toxicity showed significantly prolonged FLIO lifetimes in regions of damage, typically in a bulls-eye distribution corresponding to toxic lesions in the retina (SSC: lesion, 400 ps; unremarkable retina, 294 ps; P < 0.001; LSC: lesion, 404 ps; unremarkable retina, 316 ps; P < 0.001). Some clinically normal patients at high risk (9 of 16) and at low risk (2 of 8) of developing HCQ toxicity also showed prolonged FLIO lifetimes in the parafoveal region, whereas age-matched healthy subjects did not. HCQ at a concentration of 46 mM exhibited long autofluorescence lifetimes of around 1100 ps in either spectral channel. CONCLUSIONS: Fluorescence lifetime imaging ophthalmoscopy seems to detect retinal toxicity from HCQ at very early stages and could be a novel method to detect retinal toxicity before irreversible damage is manifest.