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PubMed1992

The Purkinje vascular entoptic test: a halogen light gives better results.

The Purkinje vascular entoptic test is a test of macular function which employs a light directed through the sclera illuminating the fundus. This light casts shadows of retinal blood vessels on to posterior pole photoreceptors. When the light source is moved, a patient with a good macular function should be able to see a negative image of his or her retinal blood vessels. We evaluated the Purkinje test in eyes with clear ocular media. A bright 3.5 watt halogen rechargeable transilluminator was used instead of a pen torch as previously described. Sixty-eight patients (129 eyes) attending a diabetic eye clinic, were tested. The test correctly identified 91% of eyes with good macular function and 77% of eyes with poor macular function (visual acuity 6/24 or poorer). If a vascular pattern was seen, it was probable (0.89) that good macular function was present. If no vascular pattern was seen, it was probable (0.80) that the eye had poor macular function (chi 2 = 60.14, P = < 0.001). Our results were superior to those previously reported. We attribute the increased accuracy of our test to the brighter light source used.

Adult↗
PubMed2002

Macular capillary blood flow velocity by blue-field entoptoscopy in diabetic and healthy women during pregnancy and the postpartum period.

PURPOSE: To study macular capillary blood flow velocity in diabetic and healthy women during pregnancy and the postpartum period. METHODS: A prospective study of 46 pregnant women with insulin-dependent diabetes and 11 healthy pregnant women was performed. Macular capillary blood flow velocity was measured by blue-field entoptic simulation. Diabetic retinopathy was graded from colour fundus photographs. RESULTS: In diabetic women, the macular capillary blood flow velocity was 0.94+/-0.27 mm/s (mean +/- SD) during the first trimester, 1.00+/-0.28 mm/s during the third trimester and 1.03+/-0.24 mm/s 3 months postpartum, compared with values of 0.71+/-0.20, 0.77+/-+/-0.20 and 0.82+/-0.19 mm/s, respectively, in healthy women (P=0.0026 between groups). Diabetic women with no or very mild retinopathy had lower macular capillary blood flow velocities than those with more severe retinopathy (P=0.0164), but higher velocities than healthy women (P=0.0167). An increase temporally from the first trimester to the postpartum period was observed in diabetic women (P=0.0294) but not in healthy (P=0.2449) women. CONCLUSIONS: According to our study macular capillary blood flow velocity is higher in diabetic than in healthy women during pregnancy and the postpartum period. Further, capillary blood flow velocity seems to depend on the grade of retinopathy in pregnant diabetic women. These data support the concept that capillary hyperperfusion may play a role in the development of diabetic retinopathy during pregnancy.

Adult↗
PubMed1997

Shape of stars and optical quality of the human eye.

Star images are entoptic phenomena that most people can perceive when looking at bright point sources in darkness. Diffraction and/or ocular aberrations seem to be a plausible cause for the star patterns, but to our knowledge no objective recordings of retinal optical images showing these characteristic patterns have been reported before. We have projected a small Gaussian spot of light onto the retina and registered the aerial image formed externally through a fully dilated pupil [one-and-a-half-pass method [J. Opt. Soc. Am. A 12, 2385 (1995)]]. We have verified that, for fully dilated pupils (> 9 mm), the blur caused by the finite size of the Gaussian spot is small. Consequently, these aerial images are a reasonably good approximation of the (inverted) optical point-spread function of the eye. These objectively recorded images displayed the distinctive radiating patterns of star images, which were compared with subjective patterns sketched out by the same observers. A strikingly close match was found between the objective and the subjective patterns of the same eyes. In addition, we computed the diffraction patterns produced by a simple schematic model of the suture lines of the anterior lens surface, also obtaining star-shaped images. These results support the commonly accepted hypothesis of a purely optical origin of subjective star images.

Humans↗
PubMed1994

Origin of the foveal granular pattern in entoptic viewing.

PURPOSE: To investigate the controversial origin of the foveal granular pattern at the center of the entoptic Purkinje vessel shadows. Both phenomena may be vividly elicited by oscillating a focused spot of light across the scleral surface of the eye in a circumferential direction. METHODS: The site and pattern of oscillation of the light spot were varied and were correlated with the appearance of the foveal granular pattern. Movement of the granular pattern relative to a foveal afterimage was also observed. RESULTS: Oscillation of the light in a meridional direction abolishes the granular pattern. Oscillating illumination through the central pupil can elicit Purkinje vessel shadows but not the characteristic foveal granular pattern. With transscleral illumination, the granular pattern oscillates with an "against" motion with respect to the motion of the Purkinje vessel shadows and with a "with" motion with respect to apparent motion of an afterimage serving as a fixed anatomic reference, and it is displaced from the center of the foveal avascular zone in the visual direction away from the source of illumination. CONCLUSIONS: These observations strongly suggest that the foveal granular pattern is a random moire pattern produced by spatial aliasing as the striated light pattern cast by the parafoveal nerve fiber elements sweeps over the photoreceptors in the form of a faint, high-spatial-frequency, irregular grating. An anatomic section of the fovea reveals the necessary geometry for production of such striated patterns, and the Nyquist frequency for the foveal photoreceptor mosaic supports the spatial aliasing effect. Also, a grating moving over a stationary random dot background demonstrates the origin of the "against" motion that is characteristic of the foveal granular pattern.

Fovea Centralis↗
PubMed1996

Macular blood flow during pregnancy in patients with early diabetic retinopathy measured by blue-field entoptic simulation.

PURPOSE: To study macular capillary blood flow velocity during pregnancy and postpartum in diabetic women with minimal diabetic retinopathy. METHODS: Macular capillary blood velocity was measured using the blue-field entoptic simulation technique in 17 type I diabetic pregnant women with minimal background retinopathy and 10 healthy pregnant women at the 12th and 32nd-36th weeks of pregnancy and 3 months after delivery. Red-free fundus photography was also performed at all visits. RESULTS: Capillary blood velocities at the 12th week of pregnancy were 1.09 +/- 0.37 mm/s in the diabetic women and 0.81 +/- 0.21 mm/s in the controls(P = 0.017), at the 32nd week 0.93 +/- 0.19 mm/s and 0.94 +/- 0.24 mm/s (P = 0.880), and 3 months postpartum 0.98 +/- 0.25 mm/s and 0.75 +/- 0.17 mm/s (P = 0.016), respectively. Analysis of variance indicated that there was a significant difference in leukocyte velocities during the course of pregnancy, with the flow being constantly elevated in diabetic women, but increasing by term in nondiabetic women (P = 0.039). Capillary flow velocity showed a statistically non-significant tendency to be higher in patients with HbA1c levels > 6.4%. Capillary flow velocity levels were not connected with changes in the number of microaneurysms. Capillary leukocyte density in the pregnant diabetic women did not differ from that of nondiabetic pregnant women. CONCLUSIONS: These data suggest that during pregnancy there is a difference in retinal capillary blood flow between diabetic women with minimal background retinopathy and normal women. The lack of increase in blood flow in macular capillaries during diabetic pregnancy may reflect redistribution of retinal capillary flow during diabetic pregnancy or be due to altered rheological properties of blood components in diabetic pregnancy.

Adult↗
PubMed2006

Subjective visual sensation during vitrectomy under retrobulbar anesthesia.

PURPOSE: To report a precise illustrated image of patient's view during vitrectomy. DESIGN: Interventional case report. METHODS: A 56-year-old male with cystoid macular edema (CME) associated with epiretinal membrane underwent vitrectomy. The patient seemed to find gratification in being operated on because he was able to see what was going on. He was a professional artist in computer graphics, and he drew three different pictures depending on the surgical procedures. RESULTS: These pictures depicted the moving of pasty, whirling fluid during core vitrectomy, numerous black or gray spots like snowflakes by intravitrealy injected crystals of triamcinolone acetonide, and a sharp tapered instrument coming into the center and membrane-like material being peeled off. CONCLUSIONS: Patients may see a precise shape in a constant size, scale, and detailed movement as well, focused on the retina without described optics. Further investigation will be required to determine this mechanism.

Anesthesia, Local↗
PubMed2006

Visual experiences during different stages of LASIK: Zyoptix XP microkeratome vs Intralase femtosecond laser.

PURPOSE: To describe the loss of light perception and other visual experiences encountered during different stages of laser in situ keratomileusis (LASIK) and to compare patients' experiences between LASIK performed with the Zyoptix XP microkeratome and Intralase laser. DESIGN: Prospective, randomized, self-matched clinical study. METHODS: Forty-one patients (82 eyes) had bilateral LASIK with the corneal flap fashioned by Zyoptix XP microkeratome in one eye and Intralase laser in the other. They were interviewed postoperatively with a standardized questionnaire about their intraoperative visual experiences, including light perception and ability to see the red fixation light. RESULTS: During both vacuum suction and corneal flap fashioning, a higher proportion of eyes in the Zyoptix XP microkeratome group lost light perception compared with the Intralase group (85.4% vs 39.0% and 90.2% vs 61.0%; P < .001 and P = .004, respectively). Patients also saw flashes, various colors, movement, the surgeon's hands or fingers, and the surgeon during surgery, and there was no difference in these visual experiences between the Zyoptix XP microkeratome and Intralase groups. Overall, eight (19.5%) of 41 patients were frightened by their intraoperative visual experiences during LASIK. CONCLUSIONS: Patients retain light perception during most stages of LASIK except during suction and fashioning of the corneal flap, when some are temporarily unable to see. Many also experience various visual sensations intraoperatively, and 19.5% of patients are frightened by their visual experiences.

Adult↗
PubMed2001

Decreased macular leukocyte velocity in human immunodeficiency virus-infected individuals.

PURPOSE: To determine whether human immunodeficiency virus (HIV)-infected individuals have decreased macular capillary blood flow in vivo. DESIGN: Case control study. METHODS: Macular leukocyte velocity and perceived leukocyte density were determined in 41 HIV-infected individuals without cytomegalovirus retinitis and 31 HIV-negative control subjects using the blue field simulation technique (BFS-2000, Oculix, Inc., Jenkintown, PA). Velocity and density measurements for HIV-infected individuals were compared to current and lowest previous CD4+ T-lymphocyte counts, HIV RNA blood levels, and blood leukocyte counts. RESULTS: Mean macular leukocyte velocity was lower in HIV-infected individuals than in controls (P = 0.0006). No correlations were identified between velocity measurements and the following factors in HIV-infected individuals: current or lowest previous CD4+ T-lymphocyte count; or HIV RNA blood level. Mean perceived leukocyte density in HIV-infected individuals was lower than in controls (P = 0.003), but was not correlated with blood leukocyte count in HIV-infected individuals. No relationships were identified between macular leukocyte velocity and duration of medication use or duration of elevated CD4+ T-lymphocyte count in patients receiving potent antiretroviral therapy. CONCLUSIONS: Reduced macular leukocyte velocity may have important implications for understanding the retinal microvasculopathy of HIV disease, the pathogenesis of opportunistic retinal infections, and visual dysfunction in HIV-infected individuals who do not have opportunistic retinal infections. We found no evidence that macular leukocyte velocity increased with immune reconstitution.

Adult↗
PubMed1985

Migraine art.

An analysis is made of 207 drawings and paintings entered for a migraine art competition. All types of visual disturbances were depicted. One hundred and fifty-four of the paintings showed spectral appearances with fortification or teichopsia in 99. Sixty-two showed either a partial or complete hemianopic loss. Metamorphopsia was seen in 32 and pain was depicted in some form or another in 80. Situational or trigger factors were shown in 23.

Art↗
PubMed2006

What can patients see during glaucoma filtration surgery under peribulbar anesthesia?

PURPOSE: To describe the visual sensations experienced by patients during glaucoma filtration surgery under peribulbar anesthesia and to determine possible risk factors that may affect the visual sensations experienced. SETTING: King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia. METHODS: In this prospective questionnaire study, 75 consecutive adult patients listed for glaucoma filtration surgery (trabeculectomy or Ahmed tube implantation) under peribulbar anesthesia were interviewed postoperatively about the visual sensations experienced in their operated eye during the surgery. RESULTS: The mean age of the 75 patients was 59.7 years (range, 27 to 83, SD +/-12.1). Sixty-five patients (86.7%) perceived light perception during the surgery and the overall light intensity fluctuated in 45 patients (60.0%). The mean age of the patients who retained light perception intraoperatively was significantly lower compared with those who lost light perception (58.3 y vs. 68.8 y; P=0.009). Forty-six patients (61.3%) were able to perceive colors, 32 patients (42.7%) perceived movement, 31 patients (41.3%) saw surgical instruments, and 33 patients (44.0%) reported seeing the surgeon's hands or fingers. The severity of glaucoma did not affect the proportion of patients who perceived the various visual sensations. One patient (1.3%) was frightened by his intraoperative visual experience. Of the remaining patients, 53 (70.7%) said the visual sensations did not affect them, whereas 21 (28.0%) found them unpleasant. CONCLUSIONS: The majority of patients undergoing glaucoma filtration surgery retained light perception intraoperatively and many also experienced various visual sensations. Only 1.3% of patients were frightened by their visual experience.

Adult↗
PubMed1975

Posterior vitreous detachment after cataract extraction in non-myopic eyes and the resulting retinal lesions.

A series of 54 non-myopic aphakic eyes with no signs of posterior vitreous detachment and 63 non-myopic aphakic eyes with various stages of posterior vitreous detachment was followed-up for a period of 6 months to 6 years. Over half of the eyes with no vitreous detachment when first examined developed various stages of posterior vitreous detachment during the follow-up period; in 10 eyes this was accompanied by entopsies with or without photopsies and three eyes developed five new retinal tears. In over half of the eyes with partial vitreous detachment when first examined, the vitreous detachment continued to progress causing retinal detachment in one eye. Late vitreous detachment in non-myopic aphakia or the completion of a partially-detached vitreous could account for the higher incidence of retinal tears in this group of eyes.

Aged↗