Comparison of VEP Values in Acquired Esotropia with Exotropia

PURPOSE: To investigate about the influence of acquired strabismus, its angle and stereopsis on visual evoked potential (VEP). METHODS: This study included 30 accommodative esotropes and 30 intermittent exotropes aged 5 to 10, who had not undergone strabismus surgery. Partially accommodative esotropes were excluded. Angle of deviation, stereopsis, and refractve error were measured in all subjects. The values of VEP to monocular and binocular pattern stimulation were recorded. Statistical significances were tested by t-test and Kruskall-Wallis test. RESULTS: In intermittent exotropes, the P100 amplitude of deviating eye was smaller than that of normal eye in the test with 8 X 8 and 16 X 16 check size (p<0.05). There was no significant difference in accommodative esotropes. The P100 latency of binocular VEP using 16 X 16 check size was significantly short in intermittent exotropes, comparing to the normal eye. Angle of deviation and stereopsis did not influence on VEP. CONCLUSIONS: Acquired strabismus occurring beyond the end of the visual critical period can influence on VEP, but angle of deviation and stereopsis could not.

The Influence of Type of Computer and VDT Work on the Dryness of Eye

PURPOSE: This study was performed in order to discover the influence of the different types of computer and VDT work on the dryness of eyes. METHODS: Forty people without eye disease were included in this study. The frequency of blinking, BUT and width of palpebral fissure were measured after working on documents with desktop computers and laptop (notebook) computers and playing computer games at PC-room for 30 minutes each. RESULTS: The BUT value was 7.0+/-2.52 seconds after working on document with laptop computers and 5.7+/-1.86 seconds with desktop computers. Whereas the frequency of blinking was almost the same, the width of palpebral fissure was 6.6+/-0.95 mm in the former and 7.7+/-1.07 mm in the latter. After playing computer games at PC-room for 30 minutes, the BUT was as low as 4.6+/-1.61 seconds. The frequency of blinking was as low as 7.7+/-2.52 times/minute, and width of palpebral fissure as high as 9.2+/-1.24 mm. CONCLUSIONS: The highest value of palpebral fissure and the lowest value of BUT were obtained after playing computer games at PC room. These results indicate that the most severe dryness of eyes results from playing computer games at PC room and leads to eye fatigue easily. This was followed in the order of severe dryness by working on documents with desktop computers and laptop (notebook) computers. Therefore, proper rest during computer work, use of artificial tears and improved environment of the VDT working room are required.

Long-standing Adult Horizontal Strabismus with Early Childhood Onset

Management of infantile and early childhood onset strabismus should be completed during early childhood to gain better binocular function and vision. The author experiencep 38 adult patients who had horizontal strabismus without any adequate treatment lasting over 14 years with onset before 6 years of age. They showed large angle of deviation and deep amblyopia. After surgery, stereopsis was never developed in all of the 14 congenital strabismic patients, whereas 30% of the 24 patients with acquired onset showed gross stereopsis. There was abnormal muscular contracture requiring adjustable stutre. All of the patients showed abnormal character psychologically. This study revealed that the longer the duration of misalignment, the greater the chance of deep amblyopia, large angle of deviation, abnormal sensory and motor adaptation, psychological influence, and abnormal muscular contracture. Therefore early initiation of therapy during early childhood should be emphasized.

The Treatment of Esodeviation with Abduction Deficiency Caused by Recurrent Pterygium

The recurrent pterygium can be caused by repeating excisions for simple pterygium. The severe conjunctival cicatrization on the area of the medial rectus muscle limits abduction and results in diplopia and it is one of the causes of acquired retraction syndrome. We experienced two patients who have marked abducticn limitation and diplopia in all directions of gaze by recurrent pterygium. In order to eliminate these troblesome symptoms and signs with only one surgery, we performed conjunctival autograft transplantation in one patient and on the other patient with bilateral recurrent pterygium, the procedure was performed with resection of the lateral rectus using adjustable suture at one time. The limitation of ocular movement and diplopia were completely gone postoperatively.

Consecutive Cyclic Esotropia Following Surgery for Intermittent Exotropia

Cyclic esotropia is a rare condition, first mentioned by Burian in 1958, in which orthophoria is regularly followed by constant deviation on rhythmic pattern. The periodicity would suggest a biologial clock mechanism. Consecutive cyclic esotropia following strabismus surgery is extremely rare. Only three cases of consecutive cyclic esotropia following surgery for intermittent exotropia have been reported We report one case of consecutive cyclic esotropia in an 8-year-old girl who underwent surgery for intermittent exotropia. The periodic esodeviation was treated with bimedial rectus recession. We suggest the overcorrection after surgery for intermittent exotropia would cause the periodicity by biological clock mechanism when the biorhythm of the patient is in an unstable and dangerous state.