Muscle Weakening Effect After Superior Rectus Z-myotomy in Rabbits

PURPOSE: To experimentally investigate the effect for muscle weakness after superior rectus Z-myotomy and histological changes. METHODS: Superior rectus muscle fibers of rabbits (16 rabbits, 32 eyes) were cut transversely with scissors across 75% of the muscle in two different positions on opposite sides. In group 1 (16 eyes), myotomies were performed at 2 and 7 mm from the muscle insertion (5 mm gap) and in group 2, performed at 2 and 5 mm (3 mm gap). The change of mark, eyeball position, and muscle tension after myotomy and 4 weeks postoperatively was evaluated, the location of the mark was examined, and muscle tissue biopsy was performed. RESULTS: After Z-myotomy, the marks of the two groups moved significantly posteriorly from insertion within groups (p<0.05), with no significant differences between groups (p=0.469). Eyeball positions of the two groups moved significantly inferiorly (p<0.05); the amount of position change of group 1 was greater than group 2 (p<0.05). When the globe was pulled in opposite directions for muscle action, the degree of change decreased with significant difference within groups (p<0.05), but there were no significant differences between groups (p=0.32). CONCLUSIONS: Z-myotomy of the superior rectus muscle affected the recession of eyeball position and weakened the muscle action. Muscle weakening affected by the different gaps between myotomies did not show consistent results.

The Change in ACD and Refraction after Nd:YAG Laser Posterior Capsulotomy

PURPOSE: To evaluate the effect of Nd:YAG laser posterior capsulotomy on refraction, anterior chamber depth (ACD), and intraocular pressure (IOP). METHODS: For forty-eight eyes of 38 patients who received Nd:YAG laser therapy, we measured visual acuity, refraction, ACD, and IOP before the capsulotomy and at 1 day, 7 days, 30 days, 90 days after. RESULTS: There were no significant difference in ACD or IOP after YAG laser capsulotomy (P>.05). But we found significant decrease in astigmatism 1day after laser treatment, especially In the large axial length group (> or =24 mm)(P<.05). This early change in astigmatism was recovered to similar to what it was before laser treatment. CONCLUSIONS: YAG laser treatment after treatment of cataract is a stable method without clinically significant effect on refraction, ACD, or IOP, except for transient astigmatic change.

Change of Eye Position in Patients with Orthophoria and Horizontal Strabismus under General Anesthesia

We studied the relationship between eye position in the awakened state and in the surgical plane of anesthesia in orthophoric and horizontal strabismus patients. We classified 105 orthophoric and horizontal strabismus patients into 5 groups, measured the eye position at the primary position by photographic measurement of the corneal reflex positions and undertook a quantitative study of eye position. Under general anesthesia, the mean divergence was 39.7 +/- 8 PD for the esotropia group, 36.6 +/- 11.7 PD for exophoria, 27.4 +/- 8.1 PD for orthophoria, and 11.1 +/- 10.2 PD for exotropia I ( 30 PD) group was rather convergent at 11.0 +/- 6.5 PD. According to the eye position of the fixating and nonfixating eyes in the esotropia group, both eyes converged with an angle deviation of 14.4 +/- 4.8 PD divergent and 14.1 +/- 4.8 PD divergent, respectively (P=.71). In the exotropia groups (I, II), the fixating eye diverged but the nonfixating eye rather converged. Therefore, the angle deviation was 19.0 +/- 2.1 PD divergent for the fixating eye and 18.2 +/- 6.4 PD divergent for the nonfixating eye (P=.68). In conclusion, under general anesthesia, eye positions in the awakened state and in the surgical plane of anesthesia were convergent or divergent, and showed a tendency to converge into the position of 25-35 PD divergent. Therefore, we could not distinguish fixating eye from nonfixating eye under general anesthesia.

The Comparison of Astigmatism According to the Incision Size in Small Incision Cataract Surgery

PURPOSE: To compare surgically-induced corneal astigmatism after 3.0 mm-sized incision and 3.2~3.4 mm-sized extended incision in cataract surgery. METHODS: This study included 205 eyes of 202 patients having phacoemulsification with temporal clear corneal incision. The eyes were classified into 4 groups according to IOL type and incision size: Group A, silicone IOL was inserted using the injector through 3.0 mm sized incision; Group B, silicone IOL was inserted using the injector through 3.2 mm sized incision; Group C, acrylic IOL was inserted using the forceps through 3.4 mm sized incision; and Group D, acrylic IOL was inserted using the injector through 3.2 mm sized incision. The uncorrected visual acuity, autorefractometry, and keratometry were taken preoperatively and at 1 week and 2 months postoperatively. RESULTS: Preoperatively, there was no significant difference between the 4 groups in preoperative astigmatism. On the seven operative day, there was significant difference between the 4 groups with one-way ANOVA test (P=.044), and between A and C, and between A and D with post-hoc tests (P<.05). There was no significant difference between the 4 groups at 2 months postoperatively (P=.945). On the seven operative day, there were significant differences between the 4 groups in surgically-induced corneal astigmatism with one-way ANOVA test (P=.009), and between A and C, and between A and D with post-hoc tests (P<.05). There was no significant difference between the 4 groups at 2 months postoperatively (P=.985). CONCLUSIONS: The 3.0 mm-sized clear corneal incision without extension induced early stabilization of surgically-induced corneal astigmatism and rapid visual rehabilitation.

Clinical Features and Counterplans of Monocular Amblyopia Failed to Occlusion Therapy

PURPOSE: To investigate the clinical features of monocular amblyopia which failed to respond to occlusion therapy. METHODS: We retrospectively reviewed the records of 57 children who failed to respond to occlusion therapy. Treatment failure was defined in two ways: visual improvement failure indicating less than two lines of visual acuity improvement, and functional failure indicating a final visual acuity in the amblyopic eye worse than 20/40 after more than 3 months of occlusion therapy. We investigated the clinical features of the patients and also classified and analyzed the factors related to prognosis into fixed factors and adjustable factors according to the adjustability during treatment. RESULTS: The visual acuity of the amblyopic and sound eyes was and average of 0.20+/-0.12 (0.02~0.5) and 0.80+/-0.18 (0.5~1.0), respectively. Forty-one patients (71.9%) had strabismus and esotropia was most frequent (65.9%). According to the age distribution, the 5~6-year-old group was most frequent (21 patients, 36.8%). Four adjustable factors, the interval from diagnosis to treatment, good compliance, full term occlusion, and sufficient occlusion, were insufficiently applied to the visual improvement failure group and the functional failure group as 60% and 53.1%, respectively. CONCLUSIONS: Clinical features of monocular amblyopia which failed to respond to occlusion therapy were moderate amblyopia with strabismus and relatively younger children. There was room for improvement to additional treatment of 50~60%.

Relationship between Clinical History Method and Orbscan II for Measuring Corneal Power after LASIK

PURPOSE: To evaluate the relation between clinical history method and Orbscan II for corneal power measurement after laser in situ keratomileusis (LASIK). METHODS: A total of 77 consecutive eyes of 43 patients who were treated with LASIK for myopia were followed up for at least 6 months. Corneal power by clinical history methods (CK) was compared with 3.0 mm zones of simulated keratometry (Sim-K), with 0.5, 1.0, 1.5, 2.0 and 3.0 mm zones of axial power maps (AP) and with 2.0, 3.0, 3.5, 4.0 and 5.0 mm zones of total optical power maps (TOP). RESULTS: Sim-K and all AP-map zones using Orbscan II were significantly higher (P<.001) than the CK value, while all TOP-map zones were significantly lower (P<.001) than the CK value. Among them, 3.0 and 4.0 mm TOP-map zones showed the highest correlation with the corneal power by CK (r2=0.889, P<.001; r2=0.889, P<.001). The correlation was higher with 3.0 mm TOP-map zone (r2=0.800, P<.001) than with 4.0 mm TOP-map zone (r2=0.793, P<.001) in high myopia patients. CONCLUSIONS: Although 3.0 and 4.0 mm TOP-map zones of Orbscan II were correlated highly with the CK value, these correlations were relatively low in high myopia patients and 3.0 mm TOP-map zone was better correlated than 4.0 mm TOP-map zone in these patients.

Corneal Sensation and Tear Film Stability after Cataract Surgery with Temporal Clear Corneal Incision

PURPOSE: To evaluate the change of corneal sensitivity and tear film stability after phacoemulsification with a 3 mm-sized temporal clear corneal incision. METHODS: This study comprised 39 eyes of 30 patients having phacoemulsification with a 3 mm-sized temporal clear corneal incision. All patients were examined for corneal sensitivity, tear break-up time, Schirmer test, fluorescein staining for ocular surface, and ocular irritation symptoms. All values were compared before and at 1, 7, 30, 60, and 90 days after surgery. RESULTS: Central corneal sensitivity was measured 58.6 +/- 3.4 mm, preoperatively. Corneal sensitivities decreased in all areas at postoperative 1 day. Among these, the corneal center and temporal incision sites showed statistically significantly decreased sensitivity of 52.3 +/- 6.5 mm and 39.5 +/- 14.4 mm, respectively (P=.021, P<.001), and the corneal sensitivity of the dry eye group decreased more than that of the normal group(P<.05). All areas of the cornea showed a tendency of improved sensitivity after 7 postoperative days, and the sensitivity of the temporal area returned to the preoperative level at postoperative 2 months. Postoperative Schirmer test and tear break-up time were unchanged compared to preoperative values (P=.14, P=.11). However fluorescein staining scores for the ocular surface increased from 2.95 +/- 1.2 to 4.4 +/- 1.9 (P<.05), and ocular irritation symptoms increased through 1 week (P<.05). CONCLUSIONS: Phacoemulsification with 3 mm-sized clear corneal incision induced local hyposensitivity of the incision site but did not change the tear film stability. However, the patients undergoing cataract surgery temporarily developed ocular surface damage and irritation symptoms. Therefore observation and proper management are required.