-
Effects of Histamine on the Intensity-Response Function of the Electroretinographic b- and d-Waves in Dark Adapted Frog Eyes
Elka Popova,
Petia Kupenova
Issue:
Volume 1, Issue 1, November 2016
Pages:
1-7
Received:
19 August 2016
Accepted:
30 August 2016
Published:
13 September 2016
DOI:
10.11648/j.ijovs.20160101.11
Downloads:
Views:
Abstract: It is known that histamine is neurotransmitter of the retinopetal axons that originate from the tuberomamillary nucleus of the posterior hypothalamus, but its role in visual information processing in the retina is not well understood. The aim of this study was to give insight into the significance that histamine has for the distal retina function revealed by electroretinogram (ERG). The effect of 5 M histamine on the intensity – response function of the b-wave (ON response) and d-wave (OFF response) of ERG was investigated in dark adapted perfused frog eyecup preparations. Perfusion with histamine caused a significant enhancement of the amplitude of both the ON and OFF responses over the entire intensity range studied in comparison with corresponding values obtained in the control experiments. The enhancing effect of histamine was more pronounced upon the OFF than ON response in the lower intensity range, where the responses were mediated by rods. The reverse was true for the higher intensity range, where the responses were cone-dominated. The b-wave V – log I function had a steeper slope and narrower dynamic range during histamine treatment. Histamine did not alter significantly the relative sensitivity of the ON response, while it significantly increased the relative sensitivity of the OFF response. The present results clearly demonstrate that histamine has a significant effect on the intensity-response function of frog ERG b- and d-waves. This effect shows some ON/OFF asymmetries in dependence of the photoreceptor input.
Abstract: It is known that histamine is neurotransmitter of the retinopetal axons that originate from the tuberomamillary nucleus of the posterior hypothalamus, but its role in visual information processing in the retina is not well understood. The aim of this study was to give insight into the significance that histamine has for the distal retina function r...
Show More
-
A New Test System and a New Cause for Acquired Foveal Color-Vision Deficiency
Issue:
Volume 1, Issue 1, November 2016
Pages:
8-19
Received:
22 August 2016
Accepted:
8 November 2016
Published:
2 December 2016
DOI:
10.11648/j.ijovs.20160101.12
Downloads:
Views:
Abstract: The purpose of this paper is to show a new cause of a macular scotoma and an anomalous acquired color-vision deficiency in the clinical fovea caused by retina detachments and subsequent surgeries. This deficiency was measured with a visual test system composed of multiple lasers, a white light beam and dozens of targets that were projected on a computer monitor and printed on paper. Lasers were used, because they produce small monochromatic target dots, 0.07 degrees of visual angle (6 mm) in diameter. The outputs of the system were the subject’s perceived color matches. In experiments with small dots of laser light, colors were judged correctly by the right eye (OD): however, the left eye (OS) could not distinguish colors. For example, a green laser dot appeared green to his OD and white to his OS. Perceived color in the abnormal OS depended on the target’s hue, saturation, luminance, wavelength, size and position on the fovea. This subject has an acquired color-vision deficiency in the clinical fovea of his OS. These visual anomalies are consistent with damage to retinal ganglion cells. Strangely, his OS does not see negative-color afterimages.
Abstract: The purpose of this paper is to show a new cause of a macular scotoma and an anomalous acquired color-vision deficiency in the clinical fovea caused by retina detachments and subsequent surgeries. This deficiency was measured with a visual test system composed of multiple lasers, a white light beam and dozens of targets that were projected on a com...
Show More
-
Collagen Cross Linking in Keratoconus: A Review
Bhavesh Makkar,
Deepak Mishra
Issue:
Volume 1, Issue 1, November 2016
Pages:
20-24
Received:
31 October 2016
Accepted:
29 November 2016
Published:
3 January 2017
DOI:
10.11648/j.ijovs.20160101.13
Downloads:
Views:
Abstract: Corneal collagen cross-linking (CXL) is a therapeutic procedure that helps in increasing the corneal stiffness in the keratoconus eyes. It increases the collagen cross linking within the extracellular matrix (ECM). Ultraviolet-A (370 nm) irradiation of the cornea after saturation with the photosensitizer riboflavin is used. A minimum deepithelialized corneal thickness of 400 μm is recommended to avoid potential irradiation damage to the corneal endothelium but in advanced cases this is not achieved which limits the application of CXL in that category. Modifications have been done in the conventional CXL procedure to be applicable in thin corneas. The current review discusses different techniques employed to achieve this end and their results. The modifications in CXL halt the progression of keratectasia without postoperative complications. However, the evidence of safety and efficacy in the use of modified CXL protocols is still limited to few studies with few patients involved. Controlled studies with long-term follow-up are required to confirm the safety and efficacy of the modified protocols.
Abstract: Corneal collagen cross-linking (CXL) is a therapeutic procedure that helps in increasing the corneal stiffness in the keratoconus eyes. It increases the collagen cross linking within the extracellular matrix (ECM). Ultraviolet-A (370 nm) irradiation of the cornea after saturation with the photosensitizer riboflavin is used. A minimum deepithelializ...
Show More
-
Visual Outcomes and Safety of Two Different Techniques of Scleral Fixated-Intraocular Lens in the Setting of Postoperative and Post-Traumatic Aphakia
Rajendra K. Bisen,
Sushil Tripathi,
Sourabh Soni,
Uma Thakur
Issue:
Volume 1, Issue 1, November 2016
Pages:
25-28
Received:
29 November 2016
Accepted:
16 December 2016
Published:
13 January 2017
DOI:
10.11648/j.ijovs.20160101.14
Downloads:
Views:
Abstract: Aim: Several techniques of scleral fixated-intraocular lens have been developed. We evaluate visual outcomes and safety of two different techniques of scleral fixated-intraocular lens in the setting of postoperative and post-traumatic aphakia. Methods: This retrospective study included 22 eyes of 22 patients, who had secondary IOL implantation surgery. The data including demographic data, ocular history, indication for surgery, preoperative and postoperative best corrected visual acuity (BCVA), intraocular pressure, detailed anterior and posterior segment evaluation using slit lamp bi-microscopy and indirect ophthalmoscopy were collected. The mean follow-up was 12 months ± 5.2 (SD) (range 12-16 months). Results: Overall, the final BCVA improved in 19 (86%) eyes, did not changed in 2 (9%), and worsened in 1 (4.5%) eye. No significant differences in BCVA were found in two techniques (p<0.2). Conclusion: Both techniques of scleral fixated PCIOL are feasible methods of managing post-traumatic and postoperative aphakia. However, functional outcomes are diverse, especially in post-traumatic cases. Longer follow-up in large population is required. Careful selection of cases and surgical method should be made before operation.
Abstract: Aim: Several techniques of scleral fixated-intraocular lens have been developed. We evaluate visual outcomes and safety of two different techniques of scleral fixated-intraocular lens in the setting of postoperative and post-traumatic aphakia. Methods: This retrospective study included 22 eyes of 22 patients, who had secondary IOL implantation surg...
Show More
-
The Management of the Retention of Giant Subfoveal Perfluorocarbon Liquid
Burak Turgut,
Tamer Demir
Issue:
Volume 1, Issue 1, November 2016
Pages:
29-31
Received:
2 December 2016
Accepted:
20 December 2016
Published:
13 January 2017
DOI:
10.11648/j.ijovs.20160101.15
Downloads:
Views:
Abstract: The aim of this report is to present the outcome of the surgical removal of a giant subfoveal retained perfluorocarbon liquid (PFCL). The case is a 65 years old man undergone pars plana vitrectomy and silicone oil implantation for macula-off superior retinal detachment about three months ago. He admitted our clinic with a complaint of gradual visual loss in the left eye. His visual acuity in the left eye was at the level of finger counting from one meter. Indirect ophthalmoscopy and optical coherence tomography revealed a giant PFCL bubble located in the fovea. The retained PFCL was removed via therapeutic extrafoveal retinotomy inferotemporal to fovea on PFCL bubble and passive aspiration with a back flush flute cannula during air-fluid exchange following silicon oil removal via 23 gauge pars plana scleroretinotomy. His visual acuity in the left eye improved to 1/10. A retinal atrophy developed at the region of which retinotomy was created. The retained subfoveal PFCL. should be removed surgically.
Abstract: The aim of this report is to present the outcome of the surgical removal of a giant subfoveal retained perfluorocarbon liquid (PFCL). The case is a 65 years old man undergone pars plana vitrectomy and silicone oil implantation for macula-off superior retinal detachment about three months ago. He admitted our clinic with a complaint of gradual visua...
Show More
