Fluorophotometric Detection of Oxygen Free Radicals in the Cornea and Lens after Excimer Laser Photore fractive Keratecto my in Rabbit

This study was performed to detect the oxidative stress in the cornea and lens in vivo by fluorophotometer after excimer laser photorefractive keratectomy(PRK). Twenty New Zealand white rabbits(20 eyes)were divided into two groups, control group(10 eyes)and PRK group(10 eyes). Rabbits of PRK group underwent PRK(8 diopters)and 2', 7'-dichlorofluorescein diacetate(DCFH-DA)was applied on the central cornea 6 hours after PRK in both groups. Fluorophotometric readings of the cornea and lens were measured 15 minutes(F15)and 30 minutes(F30)after DCFH-DA application in both groups. The cornea and lens was observed with slit lamp biomicroscope for 8 weeks. F15 and F30 of the cornea in PRK group(3.83+/-1.22 ng/ml, 5.12+/-1.57 ng/ml)were significantly higher than those in control group(2.61+/-0.59 ng/ml Eq, 3.26+/-0.76 ng/ml Eq)(p=0.01, p=0.005). F15 and F30 of the lens in PRK group(409.7+/-157.2 ng/ml, 594.9+/-242.2 ng/ml Eq)were significantly higher than those in control group(74.1+/-48.3 ng/ml Eq, 310.1+/-249.8 ng/ml Eq)(p=0.0004, p=0.01). No lens opacity developed and F15 and F30 of the cornea did not correlate with corneal haze determined at postoperative 8 weeks. In this study, we demonstrated increased oxygen free radicals in the cornea and lens after PRK by fluorophotometer in vivo and this method can be used as a useful tool to investigate the possible damage induced by oxygen free radicals in the cornea and lens after excimer laser corneal ablation.

Tear Turnover Rate Measurement Using Fluorotron Master

Maintenance of normal rate of tear production and elimination is essential for the proper controlled envionment for the cornea and the conjunctiva. We analyzed tear turnover rates in normal subjects, which mainly depend on tear production. We scanned 65 eyes of 36 normal subjects after instillation of 2% fluorescein solution 1u into the lower conjunctival fornix, using fluorophotometer (Fluorotron Master). After instillation of fluorescein solution, we scanned the eyes every 3 minutes for 30 minutes to measure tear film fluorescence. We calculated the tear turnover rate using tear film fluorescence valuse. Mean tear turnover rates were 12.3+/-6.6 %/min in normal subjects, 12.7+/-6.9 %/min in men, and 11.7+/-6.6 %/min in women. Mean tear turnover rates of men did not differ significantly from those of women (p>0.05). Mean tear turnover rates of younger subjects(25 years old~40 years old) (16.2 +/-7.4 %/min) were found to be significantly higher than ghose of older subjects(41 years old~73 years old) (9.1+/-40 %/min) (p0.05). We think that this study might be useful to study the diagnosis and treatement of tear secretory system disorders.

The Relationship between Diabetic Retinopathy and Corneal Autofluorescence

The metabolic changes in diabetics result in progressive retinopathy and influence corneal metabolism. Changes in corneal autofluorescence were demonstrated originating from mitochondrial flavoproteins and influenced by the metabolic changes in cornea in diabetics. The corneal autofluorescence was determined to evaluate its correlation with diabetic retinopathy using fluorophotometer in 25 healthy controls, 25 diabetic mellitus(DM) pationts without retinopathy, 25 background diabetic retinopathy(BDR)patients, 25 preproliferative diabetic retinopathy (PPDR) patients, and 25 proliferative diabetic retinopathy(PDR) patients. The mean values(mean +/- standard deviation in ng fluorescein/ml) were 13.9 +/- 1.9, 18.7 +/- 3.1, 19.6 +/- 2.3, 20.2 +/- 4.0, 24.3 +/- 4.2, respectively. The means of coreal autofluorescence values in diabetics were significantly higher than that of the healthy controls(p0.05), but the mean value in PDR patients was significantly higher than those of the other 4 groups(p<0.001). These results indicate that measurement of corneal autofluorescence can play a supplementary role in diagnosing diabetic retinopathy.