Hue Discrimination and Contrast Sensitivity Deficits in Diabetic Subjects With and Without Retinopathy

In an attempt to assess the evidence of abnormal central vision before the development of either overt retinopathy or a reduction in visual acuity in patients with diabetes mellitus, hue discrimination and ccntrast sensitivity were tested in diabetic patients with background diabetic retinopathy(N=57) or no-retinopathy(N=28). The results were as follows: 1. There were statistically significant differences in the mean square root of total error score, blue-yellow and red-green partial error score between the normal controIs, the no-retinopathy group and the background diabetic retinopathy groups, respectively(P<0.001). 2. In the no-retinopathy group contrast sensitivity was decreased in high spatial frequency only in comparison with the normal controls. On the other hand, in the background diabetic retinopathy group contrast sensitivity was decreased in all spatial frequency in comparison with the normal controls and the no-retinopathy group(P<0.05). 3. The proportion of diabetic patients with statistically significant color vision and contrast sensitivity deficits in the no-retinopathy and the background diabetic retinopathy groups were 3.6% and 38.6% respectively.

The Aasesament of Contrast Sensitivity by MCT 8000(R) in Normal Eyes and Peeudophakic Eyes

The standard vision test using Snellen acuity is not always an accurate indicat or of functional vision loss. Acuity measures optical blur, but psudophakic eyes frequently do not affect optical blur. Therefore, acuity cannot provide relevant informations on the loss of vision experienced by the patients. Contrast sensitivity, not acuity, has been shown to be effective in determining functional vision loss due to psudophakic eyes. The MCT 8000(R), glare and contrast sensitivity system. was used for measurement of contrast sensitivity in 19 pseudophakic eyes at postoperative 1 month, 18 pseudophakic eyes at post-operative 3 months and 18 normal control eyes. The results were as follows: 1) Contrast sensitivity decreased in pseudophakic eyes compared to normal eyes in four different conditions; day vision, day vision with perpheral glare, night vision and night vision with central glare. 2) In pseudophakic eyes, contrast sensitivity was not different between 1 month and 3 months postoperatively.

Changes of the Corneal Thickness, Intraocular Pressure and Corneal Endothelial Cell After Nd:YAG Laser Treatment of Rabbit's Lens Nucleus

The search for a less traumatic method of cataract removal through a small incision, is on going. One of the advantages of phacoemulsification is that it permits the removal of a cataract through a small incision than otherwise possible. The small incision allows the refractive error to be stabilized sooner and reduces the amount of induced postoperative astigmatism. But it may be traumatic to the endothelium, especially in cases with hard nucleus. There is a method using the Nd:YAG laser to preoperatively soften the nucleus of the cataract intracapsularly and thereby simplyfing the technique of phacoemulsification. The aim of this study is to evaluate the safety of softening lens nucleus by Nd:YAG laser application for cataract operation, and we observed the change of corneal endothleium and IOP and corneal thickness according to varied intensity, and time of laser application. The authors attempted to soften the nucleus using the Q-switched Nd:YAG laser without opening the anterior capsule. The laser was focused into the center of the nucleus and 100, 150 and 200 laser shots were made with the power of 5 mJ, 7 mJ, 10 mJ and 15 mJ. The results were as follows: 1. The corneal thickness was increased to the peak 24 hours after Nd:YAG laser application in cases of 150 and 200 laser shots with 15 mJ (P<0.05). 2. Intraocular pressure was not changed in any group after Nd:YAG laser application. 3. In morphological study with scanning electron microscope, the cases of 200 laser shots with 10 mJ and 150 laser shots with 15 mJ showed moderatly decreased the number of microvilli and partial seperation of the intercellular junctions. The cases of 200 laser shots with 15 mJ showed markedly decreased the number of microvilli and partial seperation of the intercellular junctions.

Clinical Evaluation of Full-thickness Deep Lamellar Keratoplasty

Full-thickness lamellar keratoplasty is a surgical method for corneal allografting, in which a full thickness corneal donor button without endothelium is transplanted deep into the lamellar bed of a recipient's cornea. Lamellar keratoplasty is indicated for tectonic, therapbeutic, or optical reasons. Usually the visual result with lamellar keratoplasty performed for optical purposes is less rewarding than penetrating keratoplasty. However the advantages of the lamellar graft are as follows: (1) the age limit of the donor material can be extended because the endothelium is not transplanted; (2) a lamellar graft is an extraocular procedure, and the complications in intraocular surgery can be avoided; and (3) there is no restriction as to size of the graft. We obtained good results from full-tickness deep lamellar keratoplasty on patients with granular corneal dystrophy, macular corneal dystrophy, keratoconus, and corneal scars(in cases of intact endothelium), in which penetrating keratoplasty used to be performed in the past.

Two Cases of Choroidal Neovascularizatien After Photocoagulation

The use of photocoagulation to treat proliferative diabetic retinopathy has gained widespread acceptance in ophthalmic practice since its introduction in 1959 by Meyer-Schwickerath. The purpose of photocoagulation is thought to reduce the stimulus for the vessel formation so characteristic of proliferative retinopathy. Photocoagulation may cause damage to Bruch's membrane, retinal pigment epithelium, and neurosensory retina and may result in either subretinal neovascularization or choroidal neovascularization. We found choroidal neovasaularization after performing photocogulation(one case is Argon laser the other Xenon-arch) in two diabetic retinopathy patients.