The Naka-Rushton equation, R=R(max) I(n)/(I(n)+K(n)), has been used to describe the luminance-response function of the scotopic electroretinogram. R(max) is the asymptotic value of the b-wave amplitude as a function of stimulus luminance, K is the intensity that produces a b-wave amplitude that is one-half R(max) and n is a dimensionless contant that controls the slope of the function and represents the degree of homogeneity of retinal sensitivity. These three parameters are often used in experimental laboratories, since it can show selective changes in each parameter. The present study describes and compares the parameters of Naka-Rushton equation obtained by using ganzfeld stimuli(R(max)=363+/-32 uv, n=0.86+/-0.06, log K=-2.39+/-0.19 log cd.sec/m2) and direct flash stimuli(R(max)=354+/-28 uv, n=0.80+/-0.06, log K=-2.26+/-0.15 log cd.sec/m2) in 20 eyes of the normal pigmented rabbits respectively. The n values were significantly increased by the ganzfeld light stimuli than by the direct flash stimuli(p<0.05).
Rabbits ; Retinaldehyde

The relationship between the amount of posterior displacement of the retinal surface at the temporal disc margin and the reference height(HRef)in analyzing optic disc using Heidelberg Retina Tomograph(HRT;Heidelberg Engineering, Heidelberg, Germany)was evaluated. The displacement was measured as mean height of contour(MHC)in the temporal 40degrees C segment(20degrees C superior and 20degrees C inferior to the horizontal midline)of optic disc. HRef is a value representing the location of the standard reference plane. The accordances of HRef and stereometric parameters between right and left disc were also evaluated. MHC in the temporal 40 degrees C and nasal 40 degrees C segment, HRef, and stereometric parameters of optic disc were measured with the HRT in 244 eyes of 122 subjects. HRef was 0.376+/-0.099 mm in the right disc and 0.385+/-0.090 mm in the left disc. There was good correlation between HRef and MHC in the temporal 40degrees C segment(r=0.97, p<0.01), but poor in the nasal 40 degrees C segment(r=0.29, p<0.01). The accordances of HRef and stereometric parameters increased as the difference of MHC in the temporal 40degrees C segment between right and left disc decreased. HRef was affected by the amount of posterior displacement of the retinal surface at the temporal disc margin, which occurs in instances such as a tilted disc. We should find the method to adjust stereometric parameters to the amount of disc tilt.
Retina* ; Retinaldehyde*

PURPOSE: The authors used the instrument, OCT3, to evaluate the reproducibility and map the macular thickness rapidly in normal subjects METHODS: Macular thickness was measured in 120 eyes of 62 normal subjects, aged 18 to 79 years, with the macular OCT3 map. There was no history of ocular disease in any of the subjects, and routine ophthalmoscopic examination results were normal. RESULTS: The coefficient value for macular thickness was lower than 2%, indicating that OCT3 provides reliable measurements. Macular thickness of normal subjects was 193.4 +/- 14.6 micro meter in the central ring, 273.0 +/- 14.8 micro meter in the inner ring and 238.2 +/- 15.6 micro meter in the outer ring. The nasal and superior quadrants of the inner ring and the nasal quadrant of the outer ring had higher thickness measurements than another. A decrease of retinal thickness was observed in the old group. However, gender did not have a significant effect on the values. CONCLUSIONS: Macular thickness analysis with OCT3 provided a detailed map of the macular thickness. This indicates that the method may provide a sensitive detection of pathologic thickening or thinning of the retina and suggests that the macular thickness decreases with age.
Retina ; Retinaldehyde

Polypoidal choroidal vasculopathy (PCV) is a retinal disorder characterized by aneurismal polypoidal lesions in choroidal vasculature. PCV appears to preferentially affect pigmented individuals and is considerably high among Asians. Most reports on patterns of PCV around Asia are based on a homogenous race (e.g. Chinese, Japanese) and very few descriptions from a multiracial population like those seen in Malaysia. The present study aimed to describe the demographic features, clinical and investigative characteristics of PCV in a multiracial group at Universiti Kebangsaaan Malaysia Medical Centre (UKMMC). Ninety one eyes of 86 PCV patients, comprising of Chinese (65.1%), Malays (31.4%), Indians (2.3%) and Eurasian (1.2%) were retrospectively reviewed. All underwent complete ophthalmic examination and investigations. Mean patient age was 70.4 years with a male preponderance (59.3%), and mostly unilateral presentation (94.1%). The logMAR mean presenting visual acuity was 0.78 ± 0.64. Polypoidal vascular lesions were located generally within the macula area (86.8%), manifesting mainly as submacular hemorrhage (59.3%). Interestingly a number of eyes (43.9%) had associated drusen. Optical coherence tomography largely demonstrated exudative changes (75.9%) and almost all patients (97.7%) had loss of external limiting membrane (ELM) and IS/OS interface. On indocyanine green angiography, majority of eyes had multiple polyps (82.4%) with ‘cluster’ (58.2%) being the commonest configuration. In conclusion, although the patterns of PCV in UKMMC were mainly similar to other Asian patients, a number of our patients had associated drusen. This indicates that PCV in our population could be a variant of neovascular age related macular degeneration and not solely idiopathic in nature.
Retinaldehyde ; Choroid

No abstract available.
Nerve Fibers* ; Retinaldehyde*

ERG was checked by an instrument set up by authors in eyes with vitreous opacity with and without retinal disorders. It is composed of a preamplifier(frequency response of 0.3Hz~240Hz, gain of 80 decibel), Tektronix 5103N oscilloscope(with 5A18N dual trace amplifier and 5B12N dual time base). Retina was stimulated by Grass P22 photostimulator at settings of 1, 4, 8, and 16 light in tensities. Following findings were obtained; 1. Voltage of a-wave was much increased with little change of b-wave, when intensities of photostimulation was increased. 2. Definite ERG waves were recorded with high intensities of light stimulation, when low intensities failed to produce them. 3. Even in high intensities of light stimulation, oscillatory potentials were not recorded. 4. In case of diffuse retinal damage and vitreous opacities, peak time of a and b wave were markedly delayed as well as decrease of voltages.
Electroretinography* ; Poaceae ; Retina ; Retinaldehyde

No abstract available.
Retinal Detachment* ; Retinaldehyde*

No abstract available.
Retinal Detachment* ; Retinaldehyde*

Authors analysed the clinical characteristics and the surgical results of rhegmatogenous retinal detachment in 70 patients(71 eyes) who were operated GNUH from Feb. 1990 to Feb. 1992. The clinical characteristics of rhegmatogenous retinal detachment were as follows. The result was myopia(39.4%) as the most common associated ocular finding, one break(57.7%) as the number of break, two quadrants(33.8%) as the extent of retinal detachmenthole(53.5%) as the type of break and superior temporal portion(56.3%) and anterior portion including equator(83.1%) as the location of break. The success rate of first operation was 87.3% and the overall success rate of rhegmatogenous retinal detachment maintained anatomical attachment above 6 months and exeluded 3 cases of refused reoperation was 92.3%. The type of break extent of detachment and duration of detachment were not influenced to surgical success rate statistically(P>0.05). The most common cause of first operative failure was proliferative vitreoretinopathy(57%).
Reoperation ; Retinal Detachment* ; Retinaldehyde*

Tissue temperatures were measured by a thermistor-thermometer, at suprachoroid, inner retinal surface and intravitreous portion (1mm deep), during diathermy applications on the scleral surfaces of rabbit eyes. Castroviejo's Electro-surgical Ophthalmic unit Model S-5 was used and power intensity(current) was fixed to 2, and diathermy was applied on the sclera 3mm, 2mm, and 1mm from and above the measuring points. Measurements were performed in the following groups: Group 1: Spark gap power 2. duration of application 2 sec. Group 2: Spark gap power 2. duration of application 3 sec. Group 3: Spark gap power 3. duration of application 2 sec. Group 4: Spark gap power 3. duration of application 3 sec. Maximum rise of temperature was 20.0 degrees C at suprachoroid, 16.8 degrees C at inner retinal surface and 6.6 degrees C at vitreous in Group 4. Temperature rise in vitreous was much lower than that in suprachoroid and inner retinal surface (table II, which revealed percentage of average rise per tissue temperature before diathermy). Highest measuring temperature at inner retinal surface in this experiment was under 60 degrees C, at which vitreous collagen fibrils may coagulate.
Collagen ; Diathermy* ; Retinaldehyde ; Sclera