Kristian Klemp

Photoreceptor atrophy in acute zonal occult outer retinopathy

Purpose:  To assess retinal morphology in acute zonal occult outer retinopathy (AZOOR) without ophthalmoscopically visible fundus changes.

Scotopic electrophysiology of the retina during transient hyperglycemia in type 2 diabetes.

PURPOSE To examine dark-adapted retinal function in subjects with type 2 diabetes during transient hyperglycemia. METHODS Twenty-four subjects with type 2 diabetes and minimal diabetic retinopathy were randomized to an oral glucose tolerance test (OGTT) or a fasting regimen. One study eye was kept in the dark-adapted state at all times. Full-field electroretinography (ffERG) and blood glucose measurements were performed at baseline and after 20, 80, 140, and 200 minutes. RESULTS Mean capillary glucose had increased 162% from the fasting baseline value when the concentration peaked in the OGTT group after 80 minutes (P < 0.0001). Concomitantly, rod b-wave amplitude had increased by 34% (P = 0.0007), whereas the a- and b-wave amplitudes of the standard combined rod-cone response had increased by 17% (P = 0.0013 and P = 0.0064). The dark-adapted 30-Hz flicker response was unaffected by hyperglycemia. The scotopic ffERG amplitudes rose and fell in phase with the glycemia. Implicit times did not change with the rise and fall in glycemia. CONCLUSIONS The change in scotopic signaling amplitude in the outer and middle layers of retina in subjects with diabetes was proportional to the change in capillary glucose. Cone amplitude was not influenced by hyperglycemia in this study.

Danish Rural Eye Study: the association of preschool vision screening with the prevalence of amblyopia

To determine the prevalence of amblyopia in Denmark before and after the initiation of the Danish national preschool vision screening programme.

Danish Rural Eye Study: Epidemiology of Adult Visual Impairment

ABSTRACT Purpose: To examine the frequency and causes of visual impairment (VI) in a select population of Danish adults. Methods: A total of 3843 adults aged 20–94 years from the Danish General Suburban Population Study (GESUS) were included in the population-based, cross-sectional ophthalmological study, Danish Rural Eye Study (DRES). All DRES participants received a comprehensive general health examination preceding their eye examination, including measurement of best-corrected visual acuity (BCVA) for each eye, bilateral 45° retinal fundus photographs and further ophthalmological examination where indicated. Results: Overall, 3826 of 3843 participants (99.6%) had bilateral visual acuity measurements. The overall frequency of VI (BCVA <20/40 in the better-seeing eye) was 0.4% (95% confidence interval, CI, 0.2–0.7%; n = 15) among all DRES participants, 0.6% (95% CI 0.3–1.0%; n = 15) among participants >50 years and 3.7% (95% CI 2.1–6.5%; n = 11) in participants >80 years. The primary causes of VI in the better-seeing eye were age-related macular degeneration (AMD) in 46.7% (7/15) and cataract in 26.7% (4/15). A total of 43.3% (n = 115) of participants >80 years were pseudophakic in one or both eyes. The frequency of diabetes (HbA1c ≥48 mmol/mol or self-reported diagnosis) was 5.9% (n = 227), including 1.3% (n = 51) newly diagnosed in the GESUS. Of participants determined to have VI due to exudative AMD, 50% had received anti-vascular endothelial growth factor (VEGF) treatment. Conclusion: We report a relatively low frequency of VI among Danish adults over 59 years of age compared with that observed 10–15 years ago, which is both consistent with other recent Scandinavian studies and reflective of our relatively healthy and mobile population sample.

Time-Dependent Decline in Multifocal Electroretinogram Requires Faster Recording Procedures in Anesthetized Pigs

Purpose The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures. Methods Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments. Two to 4 weeks after initial recordings, an intraocular injection of tetrodotoxin (TTX) was given and the mfERG was rerecorded as described above. Data were analyzed using mixed models in SAS statistical software. Results Propofol significantly decreases the conventional and global-flash amplitudes over time. The only significant effect of isoflurane is a decrease in the global-flash amplitudes. At 15 minutes after TTX injection several of the mfERG amplitudes are significantly decreased. There is a linear correlation between the conventional P1 and the global-flash DR mfERG-amplitude (R2 = 0.82, slope = 0.72, P < 0.0001). There is no significant difference between the 3-minute and the prolonged mfERG recordings for conventional amplitudes and the global-flash direct response. The global flash–induced component significantly decreases with prolonged mfERG recordings. Conclusions A 3-minute mfERG recording and a single stimulation protocol is sufficient in anesthetized pigs. Recordings should be obtained immediately after the induction of anesthesia. The effect of TTX is significant 15 minutes after injection, but is contaminated by the effect of anesthesia 90 minutes after injection. Therefore, the quality of mfERG recordings can be further improved by determining the necessary time-of-delay from intraocular injection of a drug to full effect. Translational Relevance General anesthesia is a possible source of error in mfERG recordings. Therefore, it is important to investigate the translational relevance of the results to mfERG recordings in children in general anesthesia.

An evaluation of fundus photography and fundus autofluorescence in the diagnosis of cuticular drusen

Purpose To examine non-mydriatic fundus photography (FP) and fundus autofluorescence (FAF) as alternative non-invasive imaging modalities to fluorescein angiography (FA) in the detection of cuticular drusen (CD). Methods Among 2953 adults from the Danish Rural Eye Study (DRES) with gradable FP, three study groups were selected: (1) All those with suspected CD without age-related macular degeneration (AMD) on FP, (2) all those with suspected CD with AMD on FP and (3) a randomly selected group with early AMD. Groups 1, 2 and 3 underwent FA and FAF and group 4 underwent FAF only as part of DRES CD substudy. Main outcome measures included percentage of correct positive and correct negative diagnoses, Cohens κ and prevalence-adjusted and bias-adjusted κ (PABAK) coefficients of test and grader reliability. Results CD was correctly identified on FP 88.9% of the time and correctly identified as not being present 83.3% of the time. CD was correctly identified on FAF 62.0% of the time and correctly identified as not being present 100.0% of the time. Compared with FA, FP has a PABAK of 0.75 (0.60 to 1.5) and FAF a PABAK of 0.44 (0.23 to 0.95). Conclusions FP is a promising, non-invasive substitute for FA in the diagnosis of CD. FAF was less reliable than FP to detect CD.

Localization, distribution, and connectivity of neuropeptide Y in the human and porcine retinas-A comparative study

Neuropeptide Y (NPY) is a peptide neurotransmitter abundantly expressed in the mammalian retina. Since its discovery, NPY has been studied in retinas of several species, but detailed characterization of morphology, cell‐type, and connectivity has never been conducted in larger mammals including humans and pigs. As the pig due to size and cellular composition is a well‐suited animal for retinal research, we chose to compare the endogenous NPY system of the human retina to that of pigs to support future research in this field. In the present study, using immunohistochemistry, confocal microscopy and 3D reconstructions, we found NPY to be expressed in GABAergic and calretinin‐immunoreactive (‐ir) amacrine cells of both species as well as parvalbumin‐ir amacrine cells of humans. Furthermore, we identified at least two different types of medium‐ to wide‐field NPY‐ir amacrine cells. Finally, we detected likely synaptic appositions between the NPY‐ir amacrine cells and melanopsin‐ and nonmelanopsin‐ir ganglion cells, GABAergic and dopaminergic amacrine cells, rod bipolar cells, and horizontal cells, suggesting that NPY‐ir cells play diverse roles in modulation of both image and non‐image forming retinal signaling. These findings extend existing knowledge on NPY and NPY‐expressing cells in the human and porcine retina showing a high degree of comparability. The extensive distribution and connectivity of NPY‐ir cells described in the present study further highlights the potential importance of NPY signaling in retinal function.

Bilateral diffuse uveal melanocytic proliferation: Case report and literature review

Bilateral diffuse uveal melanocytic proliferation (BDUMP) is a rare paraneoplastic intraocular disease that causes progressive visual loss in patients driven by an IgG factor associated with an underlying malignancy. Characteristic ocular findings include exudative retinal detachment, rapid cataract formation and uveal melanocytic tumours. The awareness and documentation of BDUMP has increased during the past decade, and the increasing amount of data collected demonstrates the effect of treatment with plasmapheresis and the value of diagnostic tools in BDUMP such as genetic and immunologic investigations. The literature of BDUMP has not been reviewed since 2003, and there is a growing need for an updated review on diagnosis and management of BDUMP. We review the literature and report a case of BDUMP with a white ciliary body tumour, iris rubeosis, increased iris pigmentation and cataract.

Delayed response of the retina after hyperbaric oxygen exposure.

Purpose:  To examine retinal electrophysiological function and retinal thickness in healthy eyes before and after hyperbaric oxygen (HBO) exposure.

Neuropeptide Y treatment induces retinal vasoconstriction and causes functional and histological retinal damage in a porcine ischaemia model

To investigate the effects of intravitreal neuropeptide Y (NPY) treatment following acute retinal ischaemia in an in vivo porcine model. In addition, we evaluated the vasoconstrictive potential of NPY on porcine retinal arteries ex vivo.