Corneal autofluorescence: an indicator of diabetic retinopathy.

The metabolic disorder in diabetics often results in progressive retinopathy with severe visual impairment. Changes in metabolism can influence corneal autofluorescence. This has led to speculation that diabetic retinopathy might be associated with changes in corneal autofluorescence. Corneal autofluorescence of both eyes was determined by fluorophotometry in 94 insulin-dependent diabetes mellitus patients and in 46 healthy controls to evaluate its correlation with diabetic retinopathy. The modified Airlie House classification was used for grading diabetic retinopathy: (1) no or negligible retinopathy; (2) minimal background retinopathy; (3) background retinopathy; and (4) (pre-) proliferative retinopathy. The corneal autofluorescence values of grade 1 retinopathy patients did not differ significantly from those of the healthy controls (mean +/- standard deviation in ng equivalent fluorescein/ml: 11.6 +/- 3.0 and 11.4 +/- 2.8, respectively; P = 0.8). The means of grade 2, 3, and 4 retinopathy patients (mean +/- standard deviation in ngEq fluorescein/ml: 16.2 +/- 4.4, 16.7 +/- 4.3, 20.9 +/- 5.4, respectively) were significantly higher than the means of grade 1 patients and healthy controls (P less than 0.004). The mean values of patients with grade 4 were significantly higher than those of patients with grades 2 and 3 (P less than 0.01). The sensitivity and specificity of corneal autofluorescence as a screening test for diabetic retinopathy were 80% and 76%, respectively; the positive predictive value for the presence of retinopathy was 90%. The values for screening on (pre-) proliferative diabetic retinopathy were 68%, 72%, and 58%, respectively. These data show corneal autofluorescence to be an adequate indicator of diabetic retinopathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Autofluorescence distribution along the corneal axis in diabetic and healthy humans.

Corneal autofluorescence, as measured with a commercial scanning fluorophotometer (lambda(exc): 415-491 nm; lambda(em): 515-630 nm), is increased in patients with diabetes mellitus. However, such fluorophotometers register an average fluorescence signal over all corneal layers as a consequence of their limited axial resolution of 0.5 mm. In order to determine the location of the fluorophores responsible for the increased corneal autofluorescence measured in diabetics, an attempt was made to measure in vivo the distribution of autofluorescence along the optical axis of the cornea with a modified slitlamp. Fluorescence excitation and emission filters identical to those of the scanning fluorophotometer were fitted to a slitlamp equipped with a slow scan CCD camera. Corneal autofluorescence intensity profiles were obtained with the slitlamp in five patients with severe diabetic retinopathy and compared to those of age-matched healthy controls. Corneal autofluorescence was also measured with the scanning fluorophotometer for comparison. The resolution of the CCD camera for measurement of fluorescence along the corneal axis was 0.1 mm. The corneal autofluorescence intensity of the patients and the healthy controls gradually decreased by about the same amount from the endothelium to the epithelium (57% mm(-1)+/-6 s.d. and 52% mm(-1)+/-5 s.d., respectively). The area under the fluorescence intensity curve was significantly greater for the patients than for the healthy controls (factor 2.4+/-1.0 s.d., P<0.001) and was proportional to the corneal fluorescence measured with the scanning fluorophotometer (r=0.92, P<0.001). The results show that (1) the distribution of autofluorescence along the corneal axis can be measured in vivo in humans, (2) the fluorophores involved are distributed throughout the cornea, and (3) the relative distribution of fluorescence is similar in diabetic patients and healthy controls.     

Investigation of corneal autofluorescence in diabetic patients

PURPOSE: The investigation of corneal autofluorescence in diabetic patients. OBJECTS AND METHODS: Corneal autofluorescence was investigated with a newly-developed fluorophotometer (wave length: excitation, 290-390 nm; emission, 430-630 nm) having, fluorescence characteristics involving those of reduced pyridine nucleotides (PN) and advanced glycation endoproduct (AGE) except pentosidine and pyrraline. Twenty-eight patients with non-insulin-dependent diabetes mellitus and sixty-seven healthy volunteers were studied. RESULTS: The corneal autofluorescence was 1.65 times higher than that of controls (p < 0.0001). In non-insulin-dependent diabetes mellitus, the corneal autofluorescence was not correlated significantly with various diabetic parameters in blood (r < 0.4). In controls, the corneal autofluorescence was correlated significantly with age (r = 0.438). CONCLUSION: The corneal autofluorescence has some relation with PN and AGE accumulation in the cornea.     

Corneal autofluorescence in relation to permeability of the blood-aqueous barrier in diabetic patients with clinically significant macular edema and in an age-matched control group

PURPOSE: Corneal autofluorescence is related to advanced glycation end products formed by glucose that reaches the cornea via the aqueous humour. The aim of the study was to examine the influence on autofluorescence of changes in permeability of the blood aqueous barrier. METHODS: Corneal autofluorescence was measured in 50 diabetic patients with clinically significant macular edema and in 28 age-matched control subjects. Permeability of the blood aqueous barrier was assessed using the diffusion coefficient of fluorescein. RESULTS: Corneal autofluorescence was higher in diabetic subjects than in the control group, mean (SD) at an excitation wavelength of 458 nm was 41.2 ng f-eq/ml (11.7) in diabetic patients and 26.5 ng f-eq/ml (7.3) in the control group, p < 0.001. The mean permeability of the blood aqueous barrier, Kd(F), was 492.0.10(-6) min(-1 )in the diabetic patients and 484.2. 10(-6) min(-1)in the control group. There was no association between permeability of the blood aqueous barrier and corneal autofluorescence, p = 0.99 for the diabetic patients and p = 0.15 for the control group (458 nm). CONCLUSIONS: Corneal autofluorescence was unaffected by permeability of the blood aqueous barrier suggesting that formation of advanced glycation products is limited by other factors than the concentration of glucose in the aqueous humour, or that other factors unrelated to nonenzymatic glycation of stromal proteins are involved.     

Investigation of Corneal Autofluorescence in Diabetic Patients

Purpose: The investigation of corneal autofluorescence in diabetic patients.Objects and Methods: Corneal autofluorescence was investigated with a newly-developed fluorophotometer (wave length: excitation, 290-390 nm; emission, 430-630 nm) having, fluorescence characteristics involving those of reduced pyridine nucleotides (PN) and advanced glycation endoproduct (AGE) except pentosidine and pyrraline. Twenty-eight patients with non-insulin-dependent diabetes mellitus and sixty-seven healthy volunteers were studied.Results: The corneal autofluorescence was 1.65 times higher than that of controls (P <.0001). In non-insulin-dependent diabetes mellitus, the corneal autofluorescenece was not correlated significantly with various diabetic parameters in blood (r < 0.4). In controls, the corneal autofluorescence was correlated significantly with age (r = 0.438).Conclusion: The corneal autofluorescence has some relation with PN and AGE accumulation in the cornea.     

The relation between corneal autofluorescence,endothelial cell count and severity of the diabetic retinopathy

We measured the corneal autofluorescence in groups with different levels of diabetic retinopathy severity (72 eyes of 46 patients) and in age-matched non-diabetic controls (34 eyes of 24 controls). We also estimated the corneal endothelium cell count and pachymetry with a contact specular microscope. For the controls, mean corneal autofluorescence was 8.8 ng equivalents fluorescein/ml (SD 0.3). Results showed increased autofluorescence of the cornea in diabetic patients (mean 17.9 ng equivalents fluorescein/ml, SD 4.2), related to the duration of diabetes (P < 0.05) and to the severity of diabetic retinopathy (P < 0.0001). Corneal endothelial cell count results showed no statistically significant relation to corneal autofluorescence (P < 0.6), indicating that the increased autofluorescence cannot be attributed to a change in corneal cell density.     

Corneal autofluorescence in diabetic and normal eyes

Corneal autofluorescence has been lately studied as a predictor of retinopathy severity in diabetic patients. We measured corneal autofluorescence in 138 eyes of 69 diabetic patients and 64 eyes of 32 healthy controls. Diabetic patients were subdivided by the severity of retinopathy according to the Modified Airlie House Classification (stage 1: no or minimal retinopathy; stage 2: minimal background retinopathy; stage 3: background retinopathy; stage 4: (pre-) proliferative retinopathy. The fluorescence peak value and the area underlying the corneal autofluorescence curve were measured with a scanning fluorophotometer (Fluorotron Master, Coherent Radiation Palo Alto CA) Healthy controls' values of corneal autofluorescence (peak value: mean 11.03±3.77 ng. equivalent fluorescein/ml; area: mean 163.85±61.40 scan-point × ng. equivalent fluorescein/ml) resulted similar (peak value: p=0.83; area: p=0.61) to those of diabetic patients without retinopathy (peak value: mean 11.2±3.4 ng.eq/ml; area: 170.07±57.23 scan-pnt.ng.eq/ml). A statistically significant difference was found between diabetic patients without retinopathy and patients with stage 2, 3, 4 retinopathy. No statistically significant difference was found both for the peak value (p=0.50) and for the area (p=0.61) between stage 3 and stage 4 retinopathy. The sensitivity and specificity of corneal autofluorescence as a screening test for diabetic retinopathy were 82% and 62% for the peak value, 87% and 60% for the area; the positive predictive value for the presence of diabetic retinopathy was 65% for the peak and 63% for the area.     

Evaluation of diabetic retinopathy by fluorophotometry

Background: Fluorophotometric variables (permeability of the blood-retinal barrier (BRB) and blood-aqueous barrier (BAB), corneal autofluorescence, and lenticular light transmittance) are reported to correlate with the severity of diabetic retinopathy. This preliminary multicenter study was performed to measure these variables simultaneously in patients with type 2 diabetes mellitus and to assess which of these variables could be of help in evaluating diabetic retinopathy. Methods: Eighty-two patients with type 2 diabetes and diabetic retinopathy were recruited in seven European university clinics. Each patient was investigated three times, at intervals of about one year. The investigations included fluorophotometric determination of corneal autofluorescence, lenticular light transmittance, and permeability of the BRB and BAB. Retinopathy was classified into four grades, using a simplified evaluation system based on the Modified Airlie House retinopathy classification and applied to color fundus slides of standard fields 1 and 2. Results: Multiregression analyses revealed that only corneal autofluorescence and BRB permeability were correlated with the severity of diabetic retinopathy (P < 0.05). Corneal autofluorescence and BRB permeability as single variables were found to be indicative of severe nonproliferative retinopathy and proliferative retinopathy (sensitivity 100% and 86%, respectively, and specificity 65% and 85%, respectively). Combination of both variables increased specificity to 92%. Conclusions: This preliminary multicenter study shows that fluorophotometric variables can be measured simultaneously and reliably in patients with diabetes and that corneal autofluorescence and BRB permeability (individually or in combination) could be of help in detecting severe non-proliferative retinopathy and proliferative retinopathy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of inhibition of glycation and oxidative stress on the development of cataract and retinal vessel abnormalities in diabetic rats

PURPOSE: To study effects of inhibition of glycation, and oxidative stress on the development of cataract and retinal vessel abnormalities in diabetic rats. METHODS: Diabetes was induced in male Wistar rats with streptozocin (STZ; 60 mg/kg BW, i.p.). Diabetic as well as strain matched control rats were fed 1) a normal diet, 2) addition of aminoguanidine in the drinking water (0.5 g/l for diabetic rats and 1.0 g/l for control rats) or 3) probucol in the pellets (1% w/w). After 6 months, the number of acellular vessels, endothelial cells and pericytes were counted in trypsin digested retinal vessel preparations, and the total retinal tissue amount of glutathione (GSH) and cysteine was measured with HPLC. RESULTS: Cataract formation occurred after 13 weeks in diabetic animals compared with 17 weeks for those treated with aminoguanidine, and 16 weeks for those treated with probucol (p < 0.001 in both cases). Aminoguanidine inhibited the formation of acellular collapsed capillary strands, 9 (3-14) vs. 18 (12-262) (median, range) per quadrant in untreated diabetic rats (p = 0.004), while probucol did not have any effect. Neither aminoguanidine, nor probucol influenced the endothelial/pericyte ratio. Diabetes caused a reduction in the GSH/cysteine ratio (10.7 +/- 0.6 vs. 15.3 +/- 1. 5) (mean +/- SD; p < 0.001). Probucol partly restored this imbalance (p < 0.05) whereas aminoguanidine did not. CONCLUSIONS: The results indicate that cataract formation in diabetes involves both glycation and oxidative stress processes. The reduced formation of acellular collapsed capillary strands by aminoguanidine suggests a potential role for glycation in vascular damage. The positive effect of probucol on cysteine/GSH metabolism imbalance indicates that derangements of one of the retinal defense systems against oxidative stress can be normalized by antioxidants.     

Role of epidermal growth factor receptor (EGFR) in corneal remodelling in diabetes

Purpose: This study examined the role of epidermal growth factor receptor (EGFR) signalling on the organization and remodelling of collagen fibrils (CFs) and proteoglycans (PGs) in the stroma of diabetic rat cornea. Methods: Diabetes was induced in female Wistar rats (n = 5) by streptozotocin (STZ) injection (55 mg/kg). Treatment with a selective inhibitor of EGFR tyrosine kinase, AG1478, was started on the same day as the induction of diabetes and administered every other day for 4 weeks. Corneas were fixed in 4% paraformaldehyde at 4 ° to allow for analysis of CF diameters and in 2.5% glutaraldehyde in sodium acetate buffer containing cuprolinic blue to enable the study of PG distribution. AnalySIS soft imaging software was used to analyse CFs and PGs. Results: Epithelial thickness, and median diameter and area fraction of CF in corneal stroma were decreased in diabetic rat cornea compared with normal cornea (p < 0.001), whereas the median PG area and area fractions were significantly increased (p < 0.001). Treatment with AG1478, although it had no action on normal cornea, prevented these diameter and area fraction changes in CFs and PGs. The cornea of AG1478‐treated diabetic rats showed a slight increase in CF diameter and area fraction and a decreased number density. Conclusions: These data show that the distribution of corneal stroma CFs and PGs was altered after 4 weeks of diabetes and that, furthermore, treatment with an EGFR signalling inhibitor normalized these abnormalities. The data suggest that EGFR plays an important role in the development of diabetes‐induced corneal remodelling.     

川芎嗪联合氨基胍对糖尿病大鼠视网膜保护作用的机制

目的　探讨川芎嗪联合氨基胍对糖尿病视网膜病变防治作用及其机制。方法　用链尿佐菌素 (STZ)制作糖尿病大鼠动物模型 ,分为正常对照组、糖尿病对照组、糖尿病氨基胍治疗组、糖尿病川芎嗪 +氨基胍治疗组 ,于第 12周测定大鼠视网膜组织NO的含量、NOS活性和AR的活性。结果　糖尿病川芎嗪 +氨基胍治疗组、糖尿病氨基胍治疗组大鼠视网膜组织NOS及AR活性显著低于糖尿病对照组 (P <0 0 1) ,NO的含量升高 (P <0 0 1) ;糖尿病氨基胍治疗组仍高于正常对照组 (P <0 0 1) ,NO的含量降低 (P <0 0 1) ;糖尿病川芎嗪 +氨基胍治疗组与正常组无显著差异。结论　川芎嗪联合氨基胍能够抑制糖尿病大鼠视网膜组织NOS、AR活性 ,从而对糖尿病视网膜病变起一定保护作用     

氨基胍对STZ糖尿病大鼠视网膜微血管病变的影响

目的:观察STZ糖尿病大鼠视网膜微血管病理改变及氨基胍对微血管病变的影响.方法:制备STZ糖尿病大鼠动物模型,随机分为正常对照(CON)组、糖尿病3mo(DM3)组,6mo(DM6)组,氨基胍3mo(AG3)组和6mo(AG6)组.每组大鼠各10只,分别饲养3,6mo.取大鼠视网膜进行视网膜微血管形态及超微结构观察.结果:DM组视网膜周细胞数目随病程逐渐减少,细胞核染色质浓缩,边集,分布于核膜下;胞质内线粒体肿胀,变性,空泡化,胞质消失,基底膜增厚.AG治疗组则明显改善.结论:氨基胍对STZ糖尿病大鼠视网膜微血管病变有防治作用.     

Estimation of corneal endothelial pump function in long-term contact lens wearers

PURPOSE: To study the effects of long-term contact lens wear on morphologic and physiologic properties of corneal endothelial cells. METHODS: The endothelial permeability to fluorescein and the rate of corneal deswelling from hypoxia-induced edema were measured in 20 long-term (mean, 17+/-9 years; range, 5-33 years) contact lens wearers and 20 age-matched control subjects. From these data, the relative endothelial pump rate in each subject was estimated, based on the pump-leak hypothesis of corneal hydration control. Corneal autofluorescence and the aqueous humor flow rate were determined by fluorescein fluorophotometry. Images of corneal endothelial cells were recorded by using specular microscopy, and morphologic indices (cell density, coefficient of variation of cell area, percentage of hexagonal cells, and skewness) were determined. RESULTS: No statistically significant differences were found between the contact lens and control groups in endothelial permeability, corneal deswelling, relative endothelial pump rate ([mean +/- SD] 1.07+/-0.33 relative pump units versus 1.01+/-0.25 relative pump units; contact lens versus control; P = 0.57), and endothelial cell density. Contact lens wearers had a significantly higher aqueous humor flow rate (3.57+/-1.03 microl/min versus 2.77+/-0.51 microl/min; P = 0.005), coefficient of variation of cell area (0.35+/-0.09 versus 0.28+/-0.04; P = 0.006), and corneal autofluorescence (3.1+/-0.6 ng/ml versus 2.3+/-0.3 ng/ml fluorescein equivalents; P < 0.001) than did non-contact lens wearers. CONCLUSIONS: Despite the known effects of long-term contact lens wear on corneal endothelial morphometry, no effect on endothelial function was found.     

Corneal autofluorescence in choroidal melanoma or in choroidal naevus

AIMS: To investigate whether corneal autofluorescence is different in patients with choroidal melanoma or choroidal naevus. METHODS: Corneal autofluorescence was determined by fluorophotometry in both eyes of 32 patients with a unilateral choroidal melanoma, 32 patients with a unilateral choroidal naevus, and 32 age matched healthy controls. The corneal autofluorescence ratio between affected and contralateral eyes of patients or between randomly selected eyes of healthy controls was calculated. RESULTS: Mean corneal autofluorescence ratio of patients with a choroidal melanoma was significantly higher than that of healthy controls (mean ratio: 1.09 (SD 0.15) and 1.00 (0.09), respectively, ANOVA p=0.014), and than that of patients with choroidal naevus (mean ratio 0.96 (0.09), p<0.001). Mean ratios of patients with choroidal naevus and healthy controls were not significantly different (p=0.27). CONCLUSIONS: Corneal autofluorescence ratio of patients with a unilateral choroidal melanoma is increased. This is probably due to an increased flow of glucose through the impaired blood-aqueous barrier in the affected eye, resulting in additional glycation of corneal proteins and hence in increased autofluorescence. The corneal autofluorescence is not increased in patients with a choroidal naevus, because the blood-aqueous barrier is not impaired in the affected eye in these patients. Measurement of corneal autofluorescence is simple, fast, and non-invasive, and might be helpful to distinguish between patients with choroidal melanoma and those with choroidal naevus.     

Abnormalities of retinal metabolism in diabetes or experimental galactosemia VIII. Prevention by aminoguanidine

PURPOSE: Aminoguanidine has been found to inhibit the development of some retinal lesions in diabetic rats and diabetic dogs, thereby raising a possibility that the formation of glycation end products (AGEs) may be an essential step in the pathogenesis of the retinopathy. The purpose of this study is to investigate the effect of aminoguanidine administration on other metabolic abnormalities which might be involved in the development of retinopathy in two models of the retinopathy, alloxan diabetes and experimental galactosemia. METHODS: Oxidative stress, nitric oxide (NO) and the activity of protein kinase C (PKC, total activity) were measured in the retina of the rats experimentally diabetic or galactosemic for 2 months. Effect of aminoguanidine administration on the inhibition of hyperglycemia-induced retinal dysmetabolism was investigated. RESULTS: Two months of diabetes or experimental galactosemia in rats resulted in elevation of retinal oxidative stress (increase in thiobarbituric acid reactive substances, TBARS, and decrease in glutathione, GSH), NO, and PKC activity. Aminoguanidine supplementation (2.5 g aminoguanidine/kg rat diet) significantly inhibited each of these abnormalities in retinas of diabetic rats and galactosemic rats, and did so without lowering the blood hexose levels of these animals. CONCLUSIONS: The ability of aminoguanidine to normalize the hyperglycemia-induced increases in retinal oxidative stress, NO and PKC in diabetic rats and galactose-fed rats suggests that these abnormalities may be inter-related in the retina, and that the biochemical mechanism by which aminoguanidine inhibits retinal microvascular disease in diabetes may be complex.     

氨基胍对糖尿病大鼠视网膜c-myc、LaminB表达的影响

目的通过观察氨基胍治疗后糖尿病大鼠视网膜凋亡相关因子c-myc及LaminB表达的变化,初步探讨氨基胍对糖尿病视网膜病变的治疗机制。方法取36只Wistar大鼠,随机分为正常组12只,另24只制备STZ糖尿病大鼠模型,分为糖尿病组12只(DM组)及氨基胍治疗组12只(AG组),分别于饲养后1个月、3个月、6个月各取4只摘除眼球制作石蜡切片,TUNEL方法观察视网膜神经细胞的凋亡,免疫组织化学方法检测c-myc及LaminB表达情况。结果 3个月DM组视网膜神经节细胞层及内核层开始出现TUNEL阳性染色,6个月染色阳性结果进一步增加,3个月和6个月AG组TUNEL染色阳性细胞数分别为(52.50±4.44)mm-2、(102.38±3.11)mm-2,显著低于同病程DM组(P<0.05)。3个月和6个月AG组c-myc表达阳性细胞数分别为(59.00±3.02)mm-2、(115.13±4.26)mm-2,显著低于同病程DM组(P<0.05)。6个月AG组LaminB表达阳性细胞数为(45.25±2.96)mm-2,低于同病程DM组,差异也具有统计学意义(P<0.05)。结论 c-myc、LaminB在糖尿病视网膜病变神经细胞凋亡通路中扮演了重要的角色,氨基胍可能通过抑制c-myc和LaminB的表达从而达到对糖尿病视网膜病变的治疗作用。     

Study of lens autofluorescence by fluorophotometry in pregnancy

Lens autofluorescence originates from an accumulation of fluorescent substances such as the tryptophan-derived residues and protein aggregations, which are associated with the preclinical progress of cataractogenesis, diabetes and lens aging. Our purpose is to determine if pregnancy alters the typical constituents of the lens autofluorescence. Fifteen healthy pregnant women (22 eyes) who were in their third trimester of pregnancy and 23 age-matched healthy controls (37 eyes, non-pregnant females). Lens autofluorescence, lens transmission and corneal autofluorescence were studied with fluorophotometry. The lens autofluorescence values were 358+/-151 ng ml(-1) in the control group and 201+/-110 ng ml(-1) in the pregnants women. The difference was significant (p=0.0074). Lens transmission values were 0.93+/-0.02 ng ml(-1) in the control group and 0.94+/-0.02 ng ml(-1) in the pregnants women: the difference was not significant. Corneal autofluorescence values were 21.9+/-7.5 ng ml(-1) in the control group and 18.2+/-5.8 ng ml(-1) in the pregnant women. The difference was not significant. Our study showed a significant decrease in lens autofluorescence in pregnant women compared to a normal population. The decrease can be partly attributed to the aqueous component of the lens that increases significantly during the final trimester of pregnancy and that this provokes a dilution of the fluorescent substances.     

Corneal autofluorescence in diabetic and penetrating keratoplasty patients as measured by fluorophotometry

At first it was verified that the major part of the fluorophotometer signal obtained when measuring corneal autofluorescence originated from fluorescence and not from scatter of excitation light at the corneal surface. The minimum percentage of the signal which can be attributed to fluorescence was determined using a fluorescence blocking filter placed in the excitation and fluorescence light path, respectively. The minimum percentages in two healthy controls, two diabetic patients and two patients after penetrating keratoplasty ranged from 75% to 93% (mean 84%). Then the corneal autofluorescence was determined in 22 healthy controls, 18 non-insulin-dependent diabetes mellitus (NIDDM). 23 insulin-dependent diabetes mellitus (IDDM) and 21 penetrating keratoplasty patients in order to detect a possible difference in autofluorescence as a result of diabetes or penetrating keratoplasty. The means of the corneal peak autofluorescence values in the NIDDM, IDDM and penetrating keratoplasty patient groups were significantly higher than that in the healthy control group (mean values in ng equivalent fluorescin ml-1: 18.0 +/- 4.2 S.D., 20.6 +/- 5.1 S.D., 17.9 +/- 5.5 S.D. and 13.7 +/- 3.7 S.D., respectively; P less than 0.01). The mean values in the NIDDM and IDDM patients did not differ significantly (P = 0.09). The autofluorescence values were independent of age in all four groups (linear correlation coefficient: r less than 0.47). The corneal peak autofluorescence was linearly correlated with the diabetes duration in the NIDDM and IDDM patients [r = 0.6, P = 0.02; increase: 0.36 ng equiv. fluorescein ml-1 yr diabetes-1]. Our results show that corneal autofluorescence is an easily obtained parameter which can be of assistance in evaluating corneal metabolism.     

Role of leukocytes in ocular inflammation of tyrosinemia II

In the animal model of tyrosinemia II only corneas from tyrosine(tyr)-fed rats produce chemoattractants in organ culture. To study the role of neutrophils (PMNs) in production of these chemoattractants, leukocytes (WBCs) were depleted using i.p. cyclophosphamide (CP). Saline (SAL)-treated rats maintained 18,375 +/- 894 WBC/mm3 (mean +/- SEM) with 4168 +/- 424 PMNs. Rats receiving CP (150 mg/kg day 0, 75 mg/kg day 4) has 1565 +/- 170 WBC (565 +/- 129 PMN) on day 3, and 398 +/- 68 WBC (19 +/- 5 PMN) on day 8. Rats ate a low-protein +/- 5% tyr diet on days 4-8. Only SAL-treated tyr-fed rats developed plaque-like gray epithelial lesions; histopathology showed corneal epithelial necrosis, stromal edema, and epithelial and stromal PMN infiltration. Control and CP-treated tyr-fed rat corneas showed no inflammation. On day 8 corneas were cultured in RPMI 1640 + 5% heat-inactivated fetal bovine serum. After 3 days, supernatants were assayed for chemotactic activity (leading front method); data were expressed as the percentage of peritoneal PMN migration relative to 5% zymosan-activated rat serum. The mean total migration toward 75% supernatant from SAL-treated, tyr-fed rat corneas was 79%, whereas migration toward corneal supernatants from controls and CP-treated tyr-fed rats ranged from 42-48%. Corneal extracts were assayed for proteolytic activity. WBC depletion prevented the increase in cathepsin B- and D-like activities present in tyr-fed corneas, suggesting that PMNs were a major source of these enzymes. The data suggest that WBC depletion reduces both corneal inflammation in vivo and the production of chemotactic activity by tyr-fed corneas in culture.