Ingrid Florén

Indoleamine-accumulating neurons in the retina of rabbit, cat and goldfish

SummarySpecial neurons accumulating indoleamines have been detected in the retina of rabbit, cat and goldfish. They have their perikarya in the inner-most cell row of the inner nuclear layer, among the amacrine cells, and send their processes to various parts of the inner plexiform layer. The distribution of the processes is different in the different animals investigated. The neurons do not correspond to the previously known dopaminergic retinal neurons, which have a different distribution of their terminals and which can be demonstrated with a specially developed technique, simultaneously with the indoleamine-accumulating neurons.

Quantitation of the uptake of indoleamines and dopamine in the rabbit retina

Abstract The characteristies of 5-hydroxytryptamine (5-HT) uptake into retinal neurons in rabbit were studied by in vitro incubations. 5-HT is actively concentrated against a considerable gradient. Kinetic analysis indicated two components of 5-HT accumulation, one representing a high affinity transport system with an apparent K m of 9·2 × 10 −7 m and the other a low affinity transport system with an apparent K m of 1·7 × 10 −5 m . For dopamine (DA) an apparent K m of 5·6 × 10 −7 m was found. By comparing the inhibitory effect of different drugs and amines on the uptake of 5-HT and DA it was possible to discriminate the 5-HT uptake from the DA uptake. Autoradiography and fluorescence microscopy confirmed the uptake of [ 3 H]5-HT and 5-HT. No active uptake could be shown for melatonin. The results are consistent with 5-HT being a transmitter in special retinal neurons.

Chemical removal of indoleamine accumulating terminals in rabbit and goldfish retina

Abstract The recently discovered indoleamine-accumulating retinal neurons are not reproducibly destroyed by a single injection of either of the toxic amines, 5,6-dihydroxytryptamine or 5,7-dihydroxytryptamine. However, two injections on two successive days will do so in the goldfish retina, whereas in the rabbit monoamine oxidase inhibition is also necessary. The terminals are destroyed after one week, but most or all of the perikarya remain, presumably because the concentration of the indole in them does not reach the level attained in the terminals.

Arguments against 5-hydroxytryptamine as neurotransmitter in the rabbit retina

The indoleamine accumulating retinal neurons are visualized only by uptake of exogenously applied indoleamines but lack fluorescence in the normal retina. These neurons have now been studied in the rabbit after pretreatment with L-tryptophan and a monoamine oxidase inhibitor with an improved histofluorescence method based on perfusion with formaldehyde-glyoxylic acid pH 4.5 containing high amounts of magnesium. The method does not, however, reveal any indoleamine fluorescence in the retina. Also, p-chloroamphetamine has no toxic effect on the neurons. Selective inhibitors of the uptake of 5-hydroxytryptamine have a lower inhibitory effect in the retina than in the hypothalamus. A substance other than 5-hydroxytryptamine is therefore suggested to be the transmitter of the indoleamine accumulating neurons.

Strategy to reduce the number of patients perceiving impaired visual function after cataract surgery.

Purpose: To reduce the number of patients who perceive more difficulties performing daily life activities 6 months after cataract extraction than before surgery. Setting: Surgeons at 4 surgical units participating in the yearly outcome studies organized by the Swedish National Cataract Register. Methods: This study comprised surgical outcomes data and completed Catquest results before and after surgery collected from consecutive patients during a 1‐month period yearly since 1995. The reasons for a no‐benefit outcome from 1995 to 1997 were identified. During the 1‐month study period in 1999, a strategy was launched to reduce postoperative anisometropia and disturbances from cataract in the fellow eye through better surgical planning. Results: The percentage of patients with a no‐benefit outcome who had anisometropia or cataract in the fellow eye as a probable reason for the outcome decreased from 27.3% and 13.0%, respectively, in the 1995 to 1997 study to 10.5% and 10.5%, respectively, in the 1999 study. Other reasons for a no‐benefit outcome such as ocular co‐morbidity or few preoperative problems increased in frequency, presumably as a result of a change in case mix. Conclusions: A strategy to reduce the number of patients perceiving more difficulties in performing daily life activities after cataract extraction than before surgery was tested. The number of patients with reasons for a poor outcome that the study focused on was reduced. Patients who gave reasons for a poor outcome other than anisometropia or cataract in the fellow eye increased in frequency, probably as a result of a change in case mix.

Postoperative aphakia in modern cataract surgery - Part 2 : Detailed analysis of the cause of aphakia and the visual outcome

Purpose: To study the incidence of aphakia after cataract surgery, the surgical complications that can lead to it, and the visual outcome. Setting: Six community‐run eye clinics participating in the Swedish National Cataract Register. Methods: Data on cataract extractions were collected prospectively from 1997 through 2001. The data also covered the type of surgery and type of intraocular lens, including a “no lens implanted” option. All data were stored in a database. These data were supplemented with data on the intended type of surgery, type of complications, possible second surgery, and visual outcome. Results: The overall incidence of postoperative aphakia was 0.65%. In 87.1% of cases, the aphakia was not planned, corresponding to an incidence of 0.48%. Unplanned aphakia was significantly related to poor preoperative vision, old age, and the presence of ocular comorbidity. The most frequent reasons for unplanned aphakia were intraoperative capsule problems and vitreous loss. In two thirds of cases, a second operation was performed. In 41% of all cases, the final visual acuity was 0.5 or better and in 27.7%, worse than 0.1. Conclusions: During the study period, 1 of every 200 routine cataract surgeries ended in unplanned aphakia. The incidence of surgical complications leading to unplanned aphakia and a final visual acuity worse than 0.1 (20/200) was 7.8 per 10000 operations in cases with no ocular comorbidity and 27.6 per 10000 operations in cases with ocular comorbidity.

Postoperative aphakia in modern cataract surgery. Part 1: Analysis of incidence and risks based on 5-year data from the Swedish National Cataract Register

Purpose: To study the incidence of aphakia after cataract extraction and evaluate the relative risk for this outcome in subgroups of patients based on preoperative conditions. Setting: Sixty‐two community‐run or private clinics participating in the Swedish National Cataract Register. Methods: Data on cataract extractions were collected prospectively from 1997 through 2001. The set of data also covered type of surgery and type of intraocular lens (IOL), including a “no lens implanted” option. All data were stored in a database. Database calculations were made of frequencies and risk ratios of postoperative aphakia in the subgroups of patients based on preoperative conditions. Results: For the entire study period, postoperative aphakia was reported in 1410 of 287951 surgeries for which complete IOL data were available, corresponding to an overall frequency of 0.49%. The occurrence of ocular comorbidity and poor preoperative visual acuity (≤0.1) in the eye to be operated on was significantly related to postoperative aphakia for each year of the study (P<.001). Glaucoma and poor visual acuity (≤0.1) in the surgical eye meant a 12.8 higher risk for aphakia after surgery than a better visual acuity (>0.1) and no ocular comorbidity. Conclusions: This national 5‐year survey showed that in routine cataract surgery performed during the study, 1 of every 200 operations ended in postoperative aphakia. Poor visual acuity (≤0.1) in the eye to be operated on combined with ocular comorbidity was the highest risk factor for postoperative aphakia.