A comparative study of the effects of argon and diode laser photocoagulation on retinal oxygenation

Background: The purpose of this study was to compare the effects of diode and argon laser photocoagulation (DLP and ALP) on the preretinal oxygen tension (P_O2): (1) directly over photocoagulated retina and (2) in between laser lesions. Methods: DLP or ALP was applied to avascular rabbit retina to produce grade II lesions. On the day of the oxygen measurement, a droplet of perfluorotributylamine was placed into the preretinal vitreous space over the lasered area of retina and the steady-state P_O2 was measured in normoxic animals using¹⁹F magnetic resonance spectroscopy. To determine the P_O2 directly over laser lesions, small (5l) droplets were placed over large ( 4 mm X 5 mm), confluent areas of treatment (burn area 95% of the treated retinal surface area). To determine the P_O2 in between laser lesions, a larger (10 –l) droplet was placed over a field of scatter photocoagulation (burn area 30% of the treated retinal surface area). The theoretical basis for this approach is discussed. Results: Untreated eyes had a preretinal P_O2 of 22±9 mm Hg (mean ± SD,n=15 eyes). The preretinal P_O2 was significantly higher over confluent, 12-day-old ALP or DLP lesions (51+13 mm Hg,n=8 eyes;P<0.01) compared to untreated eyes. However, at that time, DLP lesions had significantly higher P_O2 values (60±13 mm Hg,n=4 eyes) than did ALP lesions (42±6 mm Hg,n=4 eyes;P=0.04). The preretinal space in between laser lesions generally showed no significant increase in P_O2 (P>0.05) over controls on post-treatment days 1, 5, 14 and 47. The only exception was in the DLP group of eyes, in which a significant increase in P_O2 over untreated or ALP-treated eyes occurred on post-treatment day 5 (41±7 mm Hg,n=5 eyes;P=0.01). Over photocoagulation lesions in this study, DLP produced a greater increase in preretinal P_O2 compared to control values than did ALP. Conclusions: These results support the use of DLP as an alternative to ALP for the treatment of retinal vascular diseases in which hypoxia is suspected to play a role.     

Vitreous laser absorption following fluorescein angiography in diabetic patients

Background: Sodium fluorescein staining of the vitreous following fluorescein angiography may interact with laser photocoagulation. Methods: We evaluated the laser absorption by fluorescein in the vitreous when photocoagulation is performed following fluorescein angiography in 15 eyes of nine diabetic patients. Axial fluorescein concentration in the vitreous was measured by a scanning vitreal fluorophotometer. The amount of light absorbed by the fluorescein within the vitreous was calculated according to the Lambert-Beer law. Results: The mean fluorescein concentration ranged from 2.93 ng cm^–3 to 105.16 ng cm^–3 at 1 h after injection of fluorescein and from 8.03 to 188.56 ng cm^–3 after 4 h. Maximum laser absorption at 488 nm ranged from 6.79% (after 1 h) to 14.53% (after 4 h); at 514.5 nm it ranged from 0.96% to 2.14%; at 532 nm it ranged from 0.03% to 0.07%. At >550 nm, laser absorption was found to be negligible. Conclusions: In order to optimize the effect of photocoagulation, especially during long photocoagulation sessions, argon blue laser (488 nm) should be avoided following fluorescein angiography. Argon green laser (514.5 nm) should be used within 1 h after fluorescein injection. Frequency-doubled Nd:YAG laser (532 nm), krypton laser (647 nm) or semiconductor diode laser (810 nm) may be used at any time.Presented at the Association for REsearch in Vision and Ophthalmology Annual Meeting, Sarasota, Florida, 1–6 May 1994     

Immunolocalization of basic fibroblast growth factor during wound repair in rat retina after laser photocoagulation

Background: Basic fibroblast growth factor (bFGF) stimulates the mitogenesis of various cells and plays a key role in wound repair. We studied the immunohistochemical localization of bFGF during wound repair in the rat retina after laser photocoagulation. Methods: Krypton laser photocoagulation was performed on the eyes of pigmented rats. The eyes were enucleated on days 1, 3, 7, 14 and 28 after the photocoagulation, and the immunohistochemical localization of bFGF was assessed. Two different monoclonal antibodies and one polyclonal antibody against bFGF as first antibodies were used. Results: Marked immunoreactivity for bFGF was found in the ganglion cell layer, and weak immunoreactivity for bFGF was found in the retinal pigment epithelial (RPE) cells of the normal adult rat retina. On day 3 after laser photocoagulation, the nuclei and cytoplasm of proliferating RPE cells at the center of the photocoagulated lesion showed intense bFGF immunoreactivity. The nuclei of RPE cells around the lesion showed intense bFGF immunoreactivity. Macrophages that migrated into the lesion showed positive staining for bFGF. These immunoreactivity decreased with time. Controls (0.05 M Tris-HCl buffer, normal serum, or these same antibodies preabsorbed with bFGF) did not show positive staining. Conclusion: The finding of an elevated expression of bFGF immunoreactivity in the photocoagulated lesion suggests that bFGF may play a role in wound repair in the rat retina after laser photocoagulation.     

Expression of vascular endothelial growth factor in experimental choroidal neovascularization

Background: Although the choroidal neovascularization (CNV) is a common pathologic feature of a number of different eye diseases, its pathological mechanisms have not been fully elucidated. We investigated the expression of vascular endothelial growth factor (VEGF) in CNV using an experimental primate model. Method: CNV was induced by intense laser photocoagulation in four monkey eyes. Single eyes were enucleated at 1, 3, 7 or 14 days after photocoagulation and examined immunohistochemically for VEGF, macrophage antigen, von Willebrand factor and glial fibrillary acidic protein (GFAP). Expression of VEGF mRNA was examined byin situ hybridization. Results: One day after photocoagulation, the normal structure of the outer portion of the retina and the inner portion of the choroid was destroyed. Three days after photocoagulation, choroidal vascular endothelial cells migrated into the subretinal space through the defect in Bruch's membrane. Increased expression of VEGF was detected in the accumulating macrophages, migrating retinal pigment epithelial (RPE) cells and Muller cells. Maximal expression of VEGF was observed between 3 and 7 days after wounding, and many newly formed vessels extended into the subretinal space 7–14 days after photocoagulation. Conclusion: VEGF derived from RPE cells, macrophages and Müller cells may play a role in the formation of CNV.     

Surgical risk factors for severe postoperative proliferative vitreoretinopathy (PVR) in retinal detachment with grade B PVR

Background: Previous studies have shown that grade B proliferative vitreoretinopathy (PVR) is a considerable risk factor for the development of severe postoperative PVR. We conducted a prospective study to elucidate which surgical procedures used in retinal detachment management may stimulate the PVR process in such eyes. Materials and methods: The study included 156 eyes of 152 consecutive patients with rhegmatogenous retinal detachment complicated by grade B PVR referred before any failed surgery and operated on between 1983 and 1993. The parameters evaluated by multivariate statistical analysis included the cumulative circumferential extent of the retinal tears, the extent of the scleral buckle, gas injection, vitrectomy, the method used for retinopexy, and the time of surgical management during the period of the study. Results: The incidence of severe postoperative PVR was 25.8% in eyes managed with cryotreatment versus 2.2% in eyes managed with argon laser photocoagulation (P=0.001). The rate of severe postoperative PVR was not influenced by the other surgical variables. Conclusion: We conclude that cryotherapy may be a risk factor for the development of severe postoperative PVR in retinal detachments associated with grade B PVR.     

Anterior chamber inflammation after transconjunctival cryosurgery

Background: Inflammation caused by transconjunctival cryotherapy for prophylactic retinal detachment surgery was measured in various conditions. Methods: Thirty-four eyes of 28 patients with peripheral retinal lesions predisposing to retinal detachment were studied by laser flare cell meter before and after treatment. Results: The mean flare value for 34 eyes was 4.06 ± 1.45 photon counts/ms before surgery and 5.72 ± 2.52 pc/ms after surgery (p < 0.05). Flare value was elevated at 1, 2, and 3 weeks after treatment, peaking at 2 weeks (p < 0.05), and normal again at 4 weeks. There were no significant differences in flare increase between eyes with and without retinal breaks, eyes with and without limited retinal detachment, eyes with myopia more and less than – 8.0 D, and eyes with a treatment area limited to one quadrant and extending over more than one quadrant. Conclusion: Transconjunctival cryosurgery caused mild inflammation in the anterior chamber of the eye for 3 weeks. The inflammation was not affected by the presence of retinal break or limited retinal detachment, the degree of myopia, or the extent of the treatment area.     

Efficacy of argon laser trabeculoplasty: 3-year preliminary results of a prospective placebo-controlled study

Background: It was the purpose of this study to evaluate the efficacy of argon laser trabeculoplasty (ALT) in controlling intraocular pressure (IOP) and avoiding surgical intervention. We also investigated whether topically applied diclofenac sodium eye drops had an influence on the success rate of ALT compared with placebo eye drops. Methods: The indication for ALT was progressive glaucoma uncontrolled by maximal tolerated medical therapy. Thirty-nine of 41 patients were available for follow-up after 1122±239 days. Results: Twenty-one of 39 eyes failed during the first 3 years of follow-up for one or more reasons: 11 eyes required additional laser treatment and/or filtration surgery because of progressive visual field loss or unacceptably high IOP, 9 eyes failed to have a final IOP 21 mmHg, and 7 eyes failed because of an increase in the number of the medications. This yields a success rate for ALT of 46% for 3-year follow-up. There was no significant difference between diclofenac sodium- and placebotreated eyes concerning the success rate after 3 years (P>0.05). Conclusion: We conclude that the use of ALT for the treatment of glaucoma is best reserved for cases in which medical avenues of treatment have been exhausted.     

Hyperopia correction by noncontact holmium: YAG laser thermal keratoplasty: five-pulse treatments with 1-year follow-up

Background: Previous noncontact holmium (Ho): YAG laser thermal keratoplasty (LTK) studies on correction of low to moderate hyperopia have used treatment algorithms based on ten-pulse, variable-pulse-energy treatment parameters. The purpose of this study was to evaluate the safety, effectiveness, and stability of new five-pulse, constant-pulse-energy treatment parameters for noncontact Ho:YAG LTK. Methods: Thirty-nine hyperopic patient eyes [up to +4.75 diopters (D) refractive error] were treated using simultaneous noncontact delivery of Ho:YAG laser energy (Sunrise) with two symmetrical octagonal rings of eight spots per ring and radial spot patterns on centerline diameters of 5 and 6 mm (group A), 6 and 7 mm (group B), or 6.5 and 7.5 mm (group C). Each ring of spots received five pulses of laser light at 5 Hz pulse repetition frequency and a fixed pulse energy of 240 mJ. Thirty of the 39 patient eyes (77%) had 1-year followup exams. Results: At 1 year, the mean Suellen uncorrected distance visual acuity lines gained was 3.7 ± 0.5/6.8 ± 2.7/5.3 ± 3.3 for groups A, B, and C. The mean changes in subjective manifest refraction (spherical equivalent) were -2.08 ± 1.13 D, -1.83 ± 0.88 D,-1.22 ± 0.88 D for groups A, B, and C respectively. None of the eyes lost two or more lines of spectacle-corrected distance visual acuity. There were no clinically significant complications in any patient. Conclusion: This clinical study indicates that five-pulse noncontact LTK treatments of low hyperopia are safe and effective. The stability has to be confirmed with longer follow-up.Presented in part as a paper at the annual meeting of the Deutsche Ophthalmologische Gesellschaft, Mannheim, Germany, 21–24 September 1996     

Color Doppler imaging of the ocular vessels

Background: Color Doppler imaging allows for simultaneous two-dimensional anatomical imaging and Doppler evaluation of blood flow velocity. Methods: We examined 40 normal eyes (17 males and 23 females, aged 16 to 57 years) with this technique. The color Doppler unit used in this study had a 5.0-MHz PLF-503 ST phased-array scanning head. Each vessel examination was repeated 10 times during a single session. Results: The following peak flow velocities were found: central retinal artery, 12.5±2.4 cm/s; central retinal vein, 4.4±0.49 cm/s; posterior ciliary arteries, 14.4±2.6 cm/s; vorticose veins, 5.5±1.0 cm/s; ophthamic artery, 36.9±7.0 cm/s. Ophthalmic artery systolic and end-diastolic velocities declined as a function of age; however, these changes were not significant (systolic: r=–0.24; diastolic, r=–0.22). Conclusion: This noninvasive technique allows quantitative assessment of blood flow velocity in these vessels.     

Endothelin-like immunoreactivity in aqueous humor of patients with primary open-angle glaucoma and cataract

Background: Experimental evidence suggests a role of endothelin-1 (ET) in the regulation of intraocular pressure (IOP). Method: Therefore, inpatients undergoing cataract surgery, ET-like immunoreactivity (STIR) was measured by radioimmunoassay in pooled samples of aqueous humor of eyes with primary open-angle glaucoma (POAG) and normotensive eyes with cataract only. Results: ETIR was significantly (P < 0.05) higher in patients with cataract and POAG (20.5 ± 1.8 pg/ml,n = 12; preoperative IOP 21.4 ± I.1 mmHg,n = 33) than in patients with cataract only (15.8 ± 1.6 pg/m1,n = 15; preoperative IOP 16.0 ± 0.6 mmHg,n = 77). Conclusion: This finding may indicate a role of ET in POAG or ocular antihypertensive treatment, and its relevance should be further investigated.     

Steps to optimize transscleral photocoagulation

Background: In transscleral photocoagulation, the desired effect is coagulation of parts of the ciliary body or of the peripheral retina. However, the application is often limited by the unwanted effect of coagulation of the sclera. to reduce this effect, the ratio of incident radiation flux to radiation flux transported through the sclera (and able to coagulate the target tissue) should be minimized by the incident beam characteristics.Methods: Monte Carlo simulations for the radiation transport problem of multiple scattering in the sclera were used to calculate the ratio of transported to incident radiation for different parameter settings of beam diameters, optical thicknesses of the sclera and beam angles. To verify the theoretical calculations, an simple optical device utilizing a bulb instead of a laser source was constructed and applied to enucleated porcine eyes.Results: The theoretical calculations showed that the ratio of incident to transported radiation flux can typically be decreased by a factor of three by increasing the beam radius from 0.35 mm (as used in state-of-the-art laser devices) to 2 mm. This was confirmed by the experiments. Coagulations of the ciliary body or of the peripheral retina were possible with power densities an order of magnitude below the values normally applied with laser sources.Conclusion: To improve transscleral photocoagulation, beam diameters should be increased.     

Immunosuppressive effect of bovine seminal ribonuclease on a model of corneal transplantation in rabbit

Background: Bovine seminal ribonuclease (BS RNase) was determined to have a specific suppressive effect on the proliferation of T lymphocytes in vitro. Its immunosuppressive effect was proven in skin grafting in mice as well. Methods: The immunosuppressive effect of BS RNase was evaluated in tissue cultures and on a model of corneal transplantation in rabbits. The penetration of BS RNase into the anterior chamber was detected by immunoblotting of anterior chamber fluid obtained from animals treated either topically or subconjunctivally. Results: In vitro blastic transformation of mouse T lymphocytes was significantly inhibited by BS RNase (concentrations 15–250 g/ml). No such effect was observed on B lymphocytes. In the rabbit model of corneal graft rejection, BS RNase injected subconjunctivally prolonged mean graft survival time significantly (33.4 days) compared with placebo (salt solution; MST 17.7 days). No BS RNase was detected by immunoblotting in anterior chamber fluid after either topical or subconjunctival application. Conclusion: BS RNase showed significant immunosuppressive effect both in the blastic transformation test and in the rabbit high-risk model of corneal transplantation. Negative results of anterior chamber fluid immunoblotting indicate poor absorption of the drug.     

The effect of argon laser trabeculoplasty on the blood-aqueous barrier and intraocular pressure in human glaucomatous eyes treated with diclofenac 0.1%

Background: We studied the effect of argon laser trabeculoplasty (ALT) on the bloodaqueous barrier (BAB) in 41 eyes of 41 patients with primary open-angle glaucoma, pseudoexfoliation glaucoma, or pigment dispersion glaucoma using the Fluorotron Master II. Methods: Fluorophotometry was performed the day before ALT and on the 3rd day after surgery at 30 and 60 min after intravenous injection of 7 mg/kg body weight sodium fluorescein 10%. Intraocular pressure (IOP) was measured using Goldmann applanation tonometry on the day before surgery and at 3rd days and 1 year (mean) after ALT. Patients were treated with argon laser by one surgeon (180°, 0.1 s, 50 m 0.6–1.0 W 56 laser burns). Eyes were randomly assigned to either diclofenac-sodium 0.1 % eye drops or vehicle. Eye drops were applied six times 1 h before ALT into the operated eyes and five times daily for 3 days postoperatively. Results: On the 3rd day after ALT there was significant disruption of the BAB in the placebo-treated eyes compared to the diclofenac 0.1%-treated eyes. In the placebo-treated eyes as well as in diclofenac-sodium 0.1 %-treated eyes there was a significant decrease of IOP postoperatively for up to 1 year. There was no significant difference concerning the IOP reduction after 1 year. Diclofenac-sodium 0.1 % eye drops significantly stabilized the BAB on the 3rd day after ALT, compared to placebo, in this model. Conclusion: Diclofenac-sodium 0.1 % significantly stabilized the disruption of the blood-aqueous barrier on the 3rd day after ALT. Concerning the IOP-lowering effect of ALT, the postoperative application of steroids should be avoided.     

Indirect scatter laser photocoagulation to subfoveal choroidal neovascularization in age-related macular degeneration

Background: Occult choroidal neovascularization (CNV), poorly defined on fluorescein angiography, is present in the majority of patients with exudative complications of age-related macular degeneration. For patients who present with this type of subfoveal CNV but who have useful visual acuity, no form of treatment is of proven benefit. Accordingly, a pilot randomized trial of indirect laser treatment was performed. The rationale of this treatment was to inhibit the CNV through laser-induced effects on the retinal pigment epithelium. Methods: Patients with occult subfoveal CNV without retinal pigment epithelial detachment and with visual acuity of 20/200 or better were randomized to treatment or control groups. A grid of laser burns was applied to the macula beyond the area of serous retinal detachment and of angiographically defined occult CNV Results: After an average follow-up of 38 months, there was no difference in mean final visual acuity (0.12 treated, 0.14 control) or clinical outcome between treated and untreated groups. Fluorescein angiography showed gradual enlargement in the occult CNV in 58% of eyes in both groups. A decrease in visual acuity to worse than 20/200 (54% of treated, 50% of control eyes) was associated with ingrowth of well-delineated CNV (6 treated, 7 control eyes) or progression to a fibroglial or atrophic scar (11 treated, 8 control eyes). Conclusions: No benefit was demonstrated for scatter photocoagulation of the macula in patients with age-related macular degeneration and occult subfoveal CNV with initially good visual acuity. There were, however, no complications related to treatment.     

Anterior segment findings in AIDS patients with cytomegalovirus retinitis

Background: Anterior segment findings in AIDS patients presenting with cytomegalovirus (CMV) retinitis have not been specifically addressed in the American literature. Methods: Our study evaluated 21 AIDS patients with CMV retinitis. Results: Nineteen (90%) of these patients exhibited corneal endothelial deposits concurrent with CMV retinitis. The endothelial deposits were microscopic, opaque, linear flecks arranged in a reticular-like fashion. Of 42 eyes evaluated, 32 (76%) demonstrated active CMV retinitis. Corneal endothelial deposits were noted in 26 (81%) of the 32 eyes with retinitis. These corneal endothelial deposits were absent in the eyes which did not have CMV retinitis. Conclusion: Meticulous examination of the retina of an HIV-positive or AIDS patient who presents with reticularly arranged, linear, flecked corneal endothelial deposits should be performed to ensure that the diagnosis of CMV retinitis can be ruled out.     

Relaxing incisions with compression sutures for control of astigmatism after penetrating keratoplasty

Background: Ten percent of patients with persisting postoperative astigmatism following penetrating keratoplasty (PK) require surgical re-intervention, despite an otherwise successful transplant. Relaxing incisions (RIs) in combination with compression sutures seem to be the preferable procedure. However, poor predictability and lack of long-term experience complicate the issue. Here we report the 2-year follow-up results of 25 patients with high PK astigmatism treated by means of RIs and compression sutures Methods: Commonly, free-handed RIs were placed at the graft-host interface and 10–0 nylon compression sutures were placed perpendicular to the incisions. PK sutures had been removed no less than 4 months prior to refractive surgery Results: Nineteen eyes regained a functional vision of >- 0.4. The net decrease in astigmatism was 6.1 ± 4.3 D (47 ± 21 %). The mean vector-corrected change in astigmatism was 13.1 ± 5.7 D. Cylinder axis variation was reasonably low, with a correlation of attempted versus achieved axis of r=0.85. Within the first 3 months after operation the induced astigmatism regressed by, on average, 5.5 ± 4.3 D, making intraoperative overcorrection necessary. As an inevitable side effect, refractive procedures resulted in a myopic shift (4.7 ± 6.9 D) in spherical equivalence Conclusion: RIs and compression sutures are very useful in reducing postkeratoplasty astigmatism if correction of extremely high cylinder (> 10 D) is not intended. However, predictability still remains unsatisfactory and more than one operation may be required.     

Immunohistochemical evaluation of the integrity of the blood-aqueous barrier in normal and rubeotic human eyes

Background: The integrity of the blood-aqueous barrier (BAB) was analyzed using an immunohistochemical technique for the demonstration of albumin. Methods: Paraffin sections of 36 normal eyes obtained from eye banks or at autopsy (mean age 62.8 ± 15.2 years) and 46 eyes with marked iris neovascularization (mean age 54.6 ± 25.3 years) were formalin-fixed and examined using rabbit anti-human albumin. Results: In normal eyes, albumin staining was found in the iris stroma inside and outside the iris vessels but was not detected across the anterior iris border; albumin was present in the anterior chamber in one eye, but not internal to the nonpigmented ciliary epithelium. In rubeotic eyes, albumin staining extended along the anteri or iris in all 46 cases; albumin was demonstrated in the anterior chamber in 31 eyes and along to the nonpigmented ciliary epithelium in 13 eyes. Differences between normal and rubeotic eyes were significant for intensity of albumin staining in the iris stroma and for presence of albumin along the anterior iris, within the anterior chamber, and along the ciliary epithelium (P < 0.001, ² test). Conclusion: Our findings indicate that the BAB may be less resistant to leakage in the iris stroma than at the ciliary epithelium. BAB breakdown in rubeotic eyes occurred mainly in the iris; the ciliary epithelium was much less involved. Immunohistochemical staining for albumin appears to be useful for evaluating the integrity of the BAB in human pathologic specimens.     

Aqueous flare in eyes with senile disciform macular degeneration: correlation with clinical stage and area of neovascular membrane

Background: The aim of the present study was to investigate the aqueous flare in eyes with senile disciform macular degeneration (SDMD), divided into different clinical stages, and the correlation between the aqueous flare and the area of the neovascular membrane. Methods: Eighty-six eyes of 44 patients with SDMD were examined using a laser flare meter. The area of the neovascular membrane was measured by means of a digitizer in images obtained using indocyanine green videoangiography. Results: The mean value of the aqueous flare was 5.91±2.51 (photon count/ms) in 7 predisposing stage eyes, 5.68 ± 1.64 in 15 initial stage eyes, 9.09 ± 7.65 in 24 advanced form eyes, 5.40 ± 1.42 in 11 disciform scar eyes, and 5.36 ± 1.72 in 29 fellow eyes. The aqueous flare value was significantly (P<0.01) higher in eyes with the advanced form of SDMD than in the fellow eyes. There were no significant differences in aqueous flare values between eyes with predisposing stage, initial stage, and disciform scar and fellow eyes. The aqueous flare value increased significantly with increasing area of neovascular membrane (R\s=0.68, P<0.01). Conclusion: The present results suggest that the aqueous flare increases with increasing neovascular membrane area in eyes with SDMD, and decreases with scarization of the neovascular membrane.     

Oxidative reactions in the tear fluid of patients suffering from dry eyes

Purpose: To evaluate whether products of oxidative and inflammatory reactions are detectable in the tear fluid of patients suffering from dry eyes. Methods: The tear fluid of 217 patients (397 eyes) was sampled. Criteria for grouping of the patients were (1) basic secretion test (sicca l: BST = 0–5 mm, n = 78 eyes; sicca 2: BST = 6–10 mm, n = 109 eyes) and (2) subjective symptoms (normal BST, burning, foreign body sensations, tearing, dryness of the eyes: n = 78 eyes). One group of healthy patients (normal BST, n = 132 eyes) served as controls. Lipid peroxide levels and myeloperoxidase activity, as parameters for oxidative tissue damage and inflammatory activity, were determined in the tear fluid. Those patients whose consent could be obtained were subjected to the rose bengal test (sicca 1: 56 eyes; sicca 2: 97 eyes; subjective symptoms: 44 eyes; controls: 49 eyes). The correlation between BST and rose bengal test results was calculated. Results: Lipid peroxides were significantly (P < 0.05) higher in the groups sicca 1 and subjective symptoms than in healthy controls, as was the inflammatory activity in groups sicca 1, sicca 2 and subjective symptoms. Additionally, the inflammatory activity in the group sicca 1 was significantly (P < 0.05) higher than in the groups sicca 2 and subjective symptoms. No evidence of a significant correlation between BST and rose bengal test results was observed. Conclusions: Both oxidative tissue damage and polymorphonuclear leukocytes indicating an oxidative potential occur in the tear film of patients suffering from dry eyes. These reactions lead to severe damage of the involved tissue. Free radicals and inflammation may be involved in the pathogenesis or in the self-propagation of the disease.     

Macular capillary particle velocities: a blue field and scanning laser comparison

Background: Two different techniques are available for measurement of macular capillary particle velocities. The psychophysical blue field simulation technique gives data on macular leukocyte flow velocities, while the scanning laser technique provides information on capillary blood velocities of hypofluorescent segments in the macular network. Published velocity data differ considerably between the two methods. The current study was undertaken to compare the two measuring techniques in a group of healthy volunteers. Methods: Thirty-two healthy subjects (12 man, 20 women, mean age 27 years) participated in this study. All subjects underwent entoptic leukocyte visualization by means of blue field simulation followed by fluorescein angiography using scanning laser ophthalmoscopy. Results: The capillary blood velocities measured using the scanning laser technique were significantly higher (P < 0.01) than the flow velocities estimated with the blue field simulation technique (2.68 ± 0.3 mm/s vs 0.89 ±0.2 mm/s). No significant correlation between the flow velocities was found (r = –0.22). Conclusion: The differences may be related to different measuring locations and/or measurements of different phenomena. The blue field technique estimates average leukocyte flow in the macular network, whereas the scanning laser technique quantifies the velocity of erythrocyte aggregates in the capillary lumen of the para- and perifoveal network. A combination of both techniques may be helpful in interpreting physiological responsiveness and altered velocity pattern in diseased eyes.Presented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Florida, 2–7 May, 1993