Structural Alterations of Retinal Detachment After Intravitreal Triamcinolone Injection in Rabbit Eyes

PURPOSE: To investigate the effect of localized retinal detachment on both the detached and attached regions, and to determine the effect of triamcinolone on Muller cell gliosis. METHODS: Pars plana vitrectomy was performed in both eyes of 12 pigmented rabbits. A dome shaped retinal detachment was made by injecting sodium hyaluronate into the subretinal space. Triamcinolone (5 mg) was applied intravitreally to one eye (12 eyes). The detached retinal area and the neighboring attached region were studied by light and electron microscopy 3, 7, and 28 days after surgery. Tissues were prepared in 5 um sections for hematoxylin-eosin staining and immunohistochemistry with antibody to glial fibrillary acidic protein (GFAP). RESULTS: In addition to the well-known degeneration of photoreceptor cells in the detached retina, an incomplete but severe loss of ganglion cell axons occurs in both the detached and the attached regions. The total retinal thickness gradually decreased in the detached areas, while the thickness of the inner retinal layers remained virtually unchanged over several weeks. Gliotic alterations were apparent in both the detached and non-detached retinal areas, and intravitreal triamcinolone did not alter these gliotic alterations of Muller cells. CONCLUSIONS: It is noteworthy that progressive retinal destruction also occurs in the attached retina after local detachment. This may account for visual impairment in strikingly large areas of the visual field, even after retinal reattachment.

The Change of Ocular Position According to the Amount of Recession after Superior Rectus Muscle Resection on White Rabbit

PURPOSE: To compare the effect of combined recession and resection on ocular position. METHODS: We designed a study with three groups of white rabbits. A recession was performed by differing the amount, 9 mm, 12 mm and 15 mm, according to the group, after 12 mm resection on superior rectus muscle. Before and 1 week after the operation, distance from lower margin to upper corneal limbus was measured using photographs. RESULTS: In 12 mm recession group, the distance before and after the operation was 9.44 mm and 9.19 mm respectively, showing no statistically significant change (P=0.2344). In 15 mm recession group, the ocular position showed significant depression, from 9.13 to 7.87 mm (P=0.0017), whereas in 9 mm recession group ocular position showed significant elevation from 9.11 to 10.85 mm (P=0.0078). CONCLUSIONS: The result of this study showed that when combined resection and recession on the same extraocular muscle were made in the same amount, eye alignment at primary ocular position was kept. Furthermore this procedure enables adjustable surgery to be considerable in incomitant strabismus.

The Change of Deviation Angle according to Gaze Position in Exotropes with Inferior Oblique Overaction

PURPOSE: To determine the correlation between the grade of inferior oblique overaction and the change of deviation angle according to gaze position. METHODS: We classified 90 patients into 4 groups according to the grade of inferior oblique overaction. Deviation angle was respectively measured in upward, primary and downward position at far and the difference between them was analyzed. And we assessed the frequency of V and Y pattern and the concordance of deviating eye between at primary position and at upgaze. RESULTS: Mean bilateral sum of the IOOA was +3.58 and average of deviation angle was 33.64 PD in upward position, 27.82 PD in primary position and 24.72 PD in downward position. Difference of deviation angle between upward and primary position was 5.82 PD (P0.05). The frequency of V pattern exotropia was 17.6% in group A, 17.1% in group B, 50% in group C and 85.7% in group D while the frequency of Y pattern among V pattern was 100%, 66.7%, 75% and 25% respectively. The chief deviating eye or IOOA predominant eye at primary position diverged during upgaze only in 67% of patients. CONCLUSIONS: The larger the inferior oblique overaction, the more V pattern exotropia was observed and deviation angle was increased at higher IOOA groups. Overall exotropia patients with IOOA shows rather Y shape than V shape. And chief deviating eye was not always deviating eye at upgaze.

The Clinical Evaluation about the Impact of Cataract Operation on the Progression of Diabetic Retinopathy

PURPOSE: To study the effect of cataract surgery and associated risk factors on the progression of diabetic retinopathy. METHODS: We performed monocular cataract surgery in 45 diabetic patients having no or the same degree of retinopathy in both eyes. After 1 year follow up, we classified patients into 2 groups and analyzed them. Group A: newly developed retinopathy only at operated eye and more progressed at operated eye than the other eye among those who didn't have retinopathy prior to surgery. And if with preoperative retinopathy, either progressed only at the operated eye or more aggravated compared to contralateral progression. Group B: neither newly developed nor more aggravated compared to the other eye. RESULTS: 15 of 45 patients (33.3%) were included in Group A and 30 patients (66.7%) in Group B. Operated eye significantly showed more severe retinopathy than non-operated contralateral eye (P0.05). CONCLUSIONS: Diabetic retinopathy was progressed after cataract operation and preoperative macular edema and diabetic nephropathy affected retinopathy progression.

Change of Corneal Astigmatism with Aging in Koreans with Normal Visual Acuity

PURPOSE: To evaluate the distribution and change of corneal astigmatism with aging in persons with normal visual acuity. METHODS: We classified 504 subjects (504 eyes) showing good naked vision at least 1.0 from 3 to 83 years into 15 groups with 5 year interval and analyzed corneal astigmatism using refraction and keratometry. RESULTS: With-the-rule astigmatism (WTR) was shown in 98.5% between 3 and 25 years and progressively decreased with aging. In 61 to 65 years' group WTR was 34.1% and against-the-rule astigmatism (ATR) was 36.4%. After then ATR was more predominant. Mean corneal astigmatism was about 1 diopter under 20 years and progressively decreased to 0.5 D at 60 years with aging. CONCLUSIONS: 84.7% of persons with normal visual acuity have corneal astigmatism. WTR was predominant in the youth but progressively decreased with aging to equal balance with ATR in the mid sixties. After then corneal astigmatism would be inclined to against-the-rule. The amount of corneal astigmatism was decreased from about an 1 diopter in twenties to 0.5 diopter in sixties.

The Changes of Tear Break-up Time and Schirmer's Test after Photore fractive Keratectomy

Myopic regression and corneal opacity are well known complications after photorefractive keratectomy(PRK)and some clinical reports suggest the postoperative dry eye syndrome make worse corneal opacity. To investigate the changes in tear secretion and tear film stability after excimer laser PRK for myopia we measured tear break-up time(BUT)and the Schirmer's test on 249 eyes of 126 persons ranging from -2 ~ -11 D(mean -5.40 D)at preoperative 1 month, 6 month and 1 year after PRK. The result shows that the Schirmer's test and BUT values are reduced together at 1 month after PRK, but BUT values return to almost normal levels at postoperative 6 months, whereas Schirmer's test values never come back to initial ones regredless of the presence of preoperative dry eye syndrome and refractive error. So we reach an idea that the decrease of tear secretion due to vague corneal sensation rather than the tear film instability from irregular corneal surface effects on the postoperative dry eye syndrome largely. From this results, we propose that artificial tears should be used at least for an year for the eyes after PRK.

A Case of Contralateral Pseudo Inferior Oblique Overaction after Unilateral Inferior Oblique Anterior Transposition

There are a large number of reports documenting the effectiveness of the inferior oblique anterior transposition (IOAT)procedure for ipsilateral inferior oblique overaction (IOOA)occurring secondarily to the suprior oblique muscle palsy.However after this procedure, the limitation of elevation in abduction of operated eye may cause apparent IOOA of the contralateral eye, and differentiation of the causes should be required for proper treatment.The primary inferior oblique overaction, inferior oblique overaction in masked bilateral superior oblique palsy and pseudo inferior oblique overaction of the contralateral eye may be the possible causes.We performed IOAT procedure on a 35 year old man showing left hypertropia with IOOA becasuse of left superior oblique palsy.Five months after the operation, we observed the contralateral inferior oblique overaction and diagnosed as the pseudo inferior oblique overaction followed by the limitation of elevation of the operated eye.This patient was successfully treated by recessing the transpositioned inferior oblique muscle posteriorly.We report this case with literature review.