Post-eruptive flooding of Santorini caldera and implications for tsunami generation.

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

Stereoacuity and foveal fusion in adults with long-standing surgical monovision.

PURPOSE: Although binocular vision deficits occur in children who have a constant esotropia onset following significant maturation of stereopsis, it is uncertain whether adults are susceptible to changes to binocular vision. We examined binocular vision in adults with longstanding surgical monovision (> or =6 month's duration) to determine whether the binocular visual system remains susceptible to change. METHODS: Participants included 32 adults with longstanding monovision through laser-assisted in situ keratectomy or photorefractive keratectomy and 20 age-matched control subjects. After full binocular correction, binocular function was measured by using the Randot Stereoacuity Test, the Randot Preschool Stereoacuity Test, and the Worth 4-dot test at near and distance. Monovision patients were grouped as having low anisometropia (<1.5 spherical D) or moderate anisometropia (> or =1.5 spherical D). RESULTS: Non-parametric analysis of variance revealed a significant difference between group median stereoacuity (H = 16.062; P <.001). Pairwise multiple comparisons indicated both groups with monovision had significantly worse stereoacuity compared with control subjects (P <.05). Median stereoacuity values were 100 seconds of arc for patients with low anisometropia, 150 seconds of arc for patients with moderate anisometropia, and 40 seconds of arc for control subjects. A larger proportion of patients with moderate anisometropia failed the Worth-4 dot test at distance than control subjects (z = 2.619; P =.009). CONCLUSIONS: Reduced stereoacuity and an absence of foveal fusion in adults with longstanding surgical monovision suggest continued susceptibility of the binocular visual system to anomalous binocular experience.

Timely surgery in intermittent and constant exotropia for superior sensory outcome.

PURPOSE: To determine whether time of strabismus surgery for patients with acquired intermittent exotropia and constant exotropia influences postoperative sensory outcome. METHODS: In a retrospective, cross-sectional study, 76 patients with acquired intermittent or constant exotropia and motor realignment were evaluated for postoperative sensory status. Age at surgery, duration of exotropia, and presence of intermittent or constant exotropia were correlated with postoperative sensory status. The 23 male and 53 female patients had an average age of 9.3 years at the time of surgery and a mean follow-up of 5.9 years. RESULTS: Patients had a significantly greater chance of having postoperative stereoacuity better than 60 seconds of arc (bifixation) if they were surgically aligned before 7 years of age (P <.01) or before 5 years of strabismus duration (P <.05), or with intermittent as compared with constant exotropia (P <.001). Patients with postoperative bifixation had earlier surgical intervention (P <.025) and shorter duration of exotropia (P <.025) than those with postoperative monofixation. CONCLUSIONS: Patients with intermittent or constant exotropia may achieve superior sensory outcome with motor realignment before age 7, before 5 years of strabismus duration, or while the deviation is intermittent.

Screening for amblyopia in preverbal children with photoscreening photographs: II. Sensitivity and specificity of the MTI photoscreener.

OBJECTIVE: To determine the sensitivity and specificity of vision screening using the Medical Technology and Innovations (MTI), Inc., PhotoScreener. DESIGN: Cross-sectional study. PARTICIPANTS AND TESTING: Three hundred ninety-two children less than 4 years of age received a complete ophthalmologic examination and were photographed using the MTI PhotoScreener. One hundred three children had normal examinations, and the remaining 284 children had conditions of interest for pediatric screening: ptosis, media opacity, refractive error, or strabismus. Five children were excluded. MAIN OUTCOME MEASURES: The grading of the photographs by the manufacturer's representative was compared with the results of the ophthalmologic examinations. Sensitivity and specificity of vision screening were determined. RESULTS: The analysis of all informative photographs resulted in a sensitivity of 65% and a specificity of 87%. The sensitivity of detection for children with some forms of strabismus was high, up to 95% for esotropia of 10Delta or more. Sensitivities for the detection of ptosis, media opacity, and refractive error were poor in patients where strabismus was not also present. CONCLUSIONS: The MTI PhotoScreener may play a role in preverbal vision screening; identification of two of three children with amblyopiogenic factors before age 4 would be an exciting advance in public health. However, improvement in the ability to identify children with media opacity and refractive error is necessary. Improvements may be possible with modifications of the examination failure and photograph grading criteria.

Screening for amblyopia in preverbal children with photoscreening photographs. III. improved grading criteria for hyperopia.

OBJECTIVE: To examine the ability of the Medical Technology and Innovations (MTI), Inc., Photoscreener (Cedar Falls, IA) to detect hyperopia and to improve the photograph grading criteria to screen for amblyopiogenic levels of hyperopia. DESIGN: Cross-sectional study and reanalysis. PARTICIPANTS AND TESTING: In previous work, 392 participants received a complete ophthalmologic examination and were photographed using the MTI Photoscreener. For this study, all 209 participants with normal examination findings (65 children) or hyperopia without anisometropia (144 children) were selected. The data were reanalyzed using modified photograph grading and ophthalmologic examination failure criteria. Potential reasons for why many children with hyperopia passed photoscreening were explored. MAIN OUTCOME MEASURES: We determined whether a study participant would pass or fail screening with a given photograph grading and ophthalmologic examination failure criteria. RESULTS: Most children with hyperopia of +2.00 to +3.50 diopters (D) passed screening with the MTI instrument, in most cases because their photographs lacked bright crescents. When bright crescents in at least two of the four possible meridians were the grading guideline for screening failure and the pediatric ophthalmologists' consensus hyperopia failure criteria (> +3.50 D) were adopted, the sensitivity for hyperopia detection was 100% and the specificity was 88%. Identical results were obtained using the American Academy of Ophthalmology Preferred Practice Pattern hyperopia failure criteria (>/= +4.50 D). CONCLUSIONS: The MTI photograph grading guidelines can be simplified, and the ophthalmologic examination failure criteria for hyperopia can be improved. The presence of a bright crescent in the lower or the left pupillary margin indicate hyperopia in an amblyopiogenic range (> +3.50 D).

A 5-base insertion in the gammaC-crystallin gene is associated with autosomal dominant variable zonular pulverulent cataract.

A seven-generation family with 30 members affected by highly variable autosomal dominant zonular pulverulent cataracts has been previously described. We have localized the cataracts to a 19-cM interval on chromosome 2q33-q35 including the gamma-crystallin gene cluster. Maximum lod scores are 4.56 (theta=0.02) with D2S157, 3.66 (theta=0.12) with D2S72, and 3.57 (theta=0.052) with CRYG. Sequencing and allele-specific oligonucleotide analysis of the pseudo gammaE-crystallin promoter region from individuals in the pedigree suggest that activation of the gammaE-crystallin pseudo gene is unlikely to cause the cataracts in the family. In addition, base changes in the TATA box but not the Sp1-binding site have been found in unaffected controls and can be excluded as a sole cause of cataracts. In order to investigate the underlying genetic mechanism of cataracts in this family further, exons of the highly expressed gammaC- and gammaD-crystallin genes have been sequenced. The gammaD-crystallin gene shows no abnormalities, but a 5-bp duplication within exon 2 of the gammaC-crystallin gene has been found in one allele of each affected family member and is absent from both unaffected family members and unaffected controls. This mutation disrupts the reading frame of the gammaC-crystallin coding sequence and is predicted to result in the synthesis of an unstable gammaC-crystallin with 38 amino acids of the first "Greek key" motif followed by 52 random amino acids. This finding suggests that the appropriate association of mutant betagamma-crystallins into oligomers is not necessary to cause cataracts and may give us new insights into the genetic mechanism of cataract formation.

A comparison of the rate of refractive growth in pediatric aphakic and pseudophakic eyes.

OBJECTIVE: To compare the rate of refractive growth in pseudophakic children's eyes to that of aphakic eyes. DESIGN: Multicenter, retrospective observational case series. PARTICIPANTS: 83 patients with pseudophakic eyes (100 eyes) and 74 patients with aphakic eyes (106 eyes), with an age of surgery between 3 months and 10 years and a minimum follow-up time of 3 years or more, depending on the age at surgery. METHODS: A logarithmic model was used to analyze the rate of refractive growth for each eye. MAIN OUTCOME MEASURES: Age at surgery, intraocular lens power, intraocular lens A-constant, initial postoperative refraction, final refraction, and final age. RESULTS: Overall, pseudophakic eyes showed a lesser rate of refractive growth than aphakic eyes (-4.6 diopter vs. -5.7 diopter, P = 0.03). This trend was also present but less significant when the eyes were grouped into those less than 6 months of age at surgery (-3.3 diopter vs. -4.6 diopter, P = 0.09) and older patients (-5.0 diopter vs. -6.1 diopter, P = 0.07). However, the mean quantity of myopic shift was greater in pseudophakic eyes than in aphakic eyes (-5.26 diopter vs. -4.54 diopter), despite shorter follow-up times in the pseudophakic eyes. This is due to the optical effects of a constant intraocular lens power in a growing eye. CONCLUSIONS: Pediatric pseudophakic eyes have a slightly lesser rate of refractive growth than aphakic eyes. The new rate values should be used for predicting future refractions in these eyes.

Long-term results of silicone expander for moderate and severe Brown syndrome (Brown syndrome "plus").

BACKGROUND: The treatment of Brown syndrome has been undergoing an evolution toward more effective procedures with fewer operative interventions. Dr Kenneth Wright has introduced a procedure of superior oblique muscle tenotomy with a silicone expander to reduce the incidence of overcorrection. METHODS: There was a retrospective study of 20 eyes of 19 consecutive patients with moderate or severe Brown syndrome (Brown syndrome "plus"). Follow-up ranged from 12 to 72 months. The expander, which varies 6 to 10 mm in length, was placed in all patients in the tenotomized superior oblique muscle tendon 5 mm nasal to the nasal border of the superior rectus muscle using 7-0 or 8-0 Prolene suture without violating the inner layer of the intermuscular septum. The intermuscular septum was closed over the silicone expander. RESULTS: One hundred percent of patients had resolution of the down shoot in adduction and some or full ability to elevate the eye in adduction. Twenty percent of patients required reoperation (12.5% using 5-8 mm expanders) for overcorrection. Restriction of downgaze was not seen postoperatively. Patients often show an undercorrection 1 to 6 months postoperatively and improve or occasionally overcorrect at 1 to 2 years postoperatively. One patient with a 10-mm expander extruded the implant. DISCUSSION: Placement of a 5- to 8-mm silicone expander in the tenotomized superior oblique muscle tendon is an effective means of correcting Brown syndrome with a low rate of reoperation. Initial undercorrection should not discourage the surgeon because improvement may continue for up to 3 years. The goal of treatment should be to convert a moderate or severe Brown syndrome (Brown syndrome plus) to a mild Brown syndrome ("true" Brown syndrome). CONCLUSION: This technique reduces the need for either simultaneous or subsequent inferior oblique muscle weakening and represents an advance in the treatment of Brown syndrome.

Screening for amblyopia in preverbal children with photoscreening photographs. National Children's Eye Care Foundation Vision Screening Study Group.

OBJECTIVE: This study aimed to determine the ability of healthcare professionals and lay volunteers to grade photoscreening photographs. DESIGN: The study design was a cross-sectional study. PARTICIPANTS AND INTERVENTION: One hundred children 3 years of age or younger received a complete ophthalmologic examination and were photographed using the Medical Technology Innovations (MTI) photoscreener. Twenty-six children had normal examination results, and the remaining 74 children had conditions that are of interest for pediatric screening, including strabismus, refractive error, media opacities, and ptosis. Eighteen volunteers, including pediatric ophthalmologists, pediatricians, ophthalmic technicians, health department nurses, Prevention of Blindness Society personnel, and Lions Club volunteers, graded each of the 100 photoscreening photographs. MAIN OUTCOME MEASURES: Sensitivity and specificity of vision screening and of photograph grading were measured. RESULTS: Results from various graders yielded sensitivities ranging from 37% to 88% and specificities ranging from 40% to 88%. No single grader achieved sensitivity and specificity both greater than 70%. The grading of the manufacturer's representative had a sensitivity of 43% and a specificity of 85%. Sensitivity decreased to 31% for strabismus and 18% for refractive error when the correct type of strabismus or refractive error was required to be considered true-positives. Results were not positively correlated with the ophthalmologic knowledge of the participant. CONCLUSIONS: The wide variability in sensitivities and specificities among graders indicates inconsistent photograph interpretation skills or deficient screening guidelines or both. For off-axis photoscreening as implemented by the MTI system to become a useful vision-screening method, additional photograph interpretation skill transfer may be beneficial, although not necessarily sufficient.

Theoretic refractive changes after lens implantation in childhood.

OBJECTIVE: Children with aphakia tend to have decreasing hyperopia as they grow older. No large study of the long-term refractive changes in children with pseudophakia has been published, although myopic shifts of greater than 10 diopters (D) have been reported. The authors used the refractions of children with aphakia and long follow-up to calculate the theoretic long-term refractive effects of pseudophakia. DESIGN: The study design was a chart review of eyes that underwent cataract surgery before age 10 with documented refractions for more than 7 years. PARTICIPANTS: Ninety-three eyes were studied. INTERVENTION: The initial aphakic refractions of the study eyes were used to calculate the intraocular lens (IOL) powers that would have been required to give emmetropia at cataract removal. The aphakic refractions at last follow-up were used to calculate the final pseudophakic refractions, and these were compared with the predictions of a logarithmic model of myopic shift. RESULTS: The mean follow-up time was 11 years. The median calculated pseudophakic refraction at last follow-up was -6.6 D with a range of -36.3 to +2.9 D. Children who underwent surgery in the first 2 years of life had a substantially greater myopic shift than older children (P < 0.001) and a larger variance in this myopic shift (P < 0.001). The logarithmic model accurately predicted the final refraction within 3 D in 24% of eyes undergoing surgery before 2 years of age and in 77% of eyes undergoing surgery after this age. CONCLUSIONS: Pseudophakia in children is predicted to result in a large quantity of myopic shift, particularly in very young children. An IOL power chosen to leave a child initially hyperopic should lessen both the quantity of myopic shift and the extreme myopia that can result with growth. The surgeon who implants IOLs in young children must be prepared for a wide variation in long-term myopic shift.

Myopic shift after cataract removal in childhood.

BACKGROUND: Children who have had cataract removal tend to have decreasing hyperopia (myopic shift) as they grow older. We wondered if the rate of myopic shift could be determined by age at surgery, cataract type, glaucoma, or other factors. METHODS: We studied 156 aphakic eyes of children who had cataract surgery before age 10 and documented refractions for more than 3 years. Refraction was corrected with contact lenses and spectacles; glaucoma was managed with medicine and surgery. Stepwise multiple regression was used to analyze differences in the rate of myopic shift between subgroups. RESULTS: The average refraction tended to follow a logarithmic decline with age (P < 0.01, R2 = 0.97). The average rate of myopic shift (the slope of spectacle plane refraction vs log of age, where age is in years and log is base 10) was -5.5, with a standard deviation of 3.8. Age at surgery had a small but statistically significant effect on the rate (P < 0.01, R2 = 0.04). No other studied factor reached statistical significance. However, among the 86 eyes with cataract removal after age 6 months, age at surgery was not as significant (P = 0.21), and unilateral cataract eyes tended to have a greater rate than bilateral cataract eyes (-7.7 vs -5.7; P = 0.05, R2 = 0.05). CONCLUSIONS: Aphakic refraction tends to follow a logarithmic decline with age. The rate of myopic shift is determined partly by age at surgery and whether the cataract was unilateral or bilateral, although the effects are small. A wide variation in the rate of myopic shift exists. The following factors made little difference in the rate: cataract type, glaucoma, sex, side, and best corrected visual acuity.

Acquired posterior lentiglobus.

PURPOSE/METHODS: An infant examined by three ophthalmologists was found to have unilateral posterior lentiglobus, which subsequently developed bilaterally by 15 weeks of age. RESULTS/CONCLUSIONS: The onset of posterior lentiglobus may be congenital or acquired. Infants with unilateral cataracts whose family history indicates early-onset lens opacities require careful and frequent examinations of the fellow eye.

Transection of the superior rectus muscle during intended superior oblique tenotomy: a report of three cases.

Reported complications of superior oblique surgery include postoperative vertical or torsional deviation, Brown's syndrome, head tilt, blepharoptosis, and conversion of an A-pattern to a V-pattern. McNeer reported three cases of postoperative vertical deviation, one of which was attributed to severing of the superior rectus tendon. We report three additional cases of inadvertent unrecognized transection of the superior rectus during intended superior oblique tenotomy to emphasize the importance of direct visualization of these tendons during surgery.

Prevalence of primary monofixation syndrome in parents of children with congenital esotropia.

The prevalence of primary monofixation syndrome (MFS) in the general population is approximately 1%. This study was performed to determine the prevalence of primary monofixation in biological parents of children with congenital esotropia. Ninety children with congenital esotropia were seen between November 1991 and June 1992 by one ophthalmologist (M.M.P.). One hundred and twenty-nine biological parents of these children were screened for sensorimotor abnormalities. Twelve parents were found to have secondary MFS and were removed from the analysis. This left 78 apparently non-strabismic families consisting of a total of 117 parents. Seven parents were identified as having primary MFS. The prevalence of primary MFS in this population is 9% of families and 6% of parents. Congenital esotropia is believed to be inherited in a multifactorial fashion. We believe that this increase in the prevalence of primary MFS compared to the general population lends support to the hypothesis that primary MFS may be a mild (subthreshold) effect of the "gene(s)" that cause congenital esotropia.

Autosomal dominant congenital cataract. Interocular phenotypic variability.

PURPOSE: While intrafamilial morphologic heterogeneity of autosomal dominant congenital cataracts has been well established, interocular variation in individual patients of described pedigrees is small. The authors describe a seven-generation family with 48 of 138 individuals known to be affected with autosomal dominant congenital cataracts of the pulverulent type. Affected patients exhibit a seemingly random expression of either unilateral or bilateral lens opacities. METHODS: Ophthalmic and medical histories were obtained, complete ophthalmologic examinations were performed, blood samples were drawn, and transformed lymphoblastoid lines were established on 53 patients. Eighty-five members of the family were unable to be examined. RESULTS: Twenty-eight of the 53 individuals examined had congenital cataracts. Of these patients, 19 eyes (8 right eyes and 11 left eyes) were unilateral and 9 were bilateral. The clinically unaffected eye in patients with unilateral cataracts showed no evidence of lenticular opacity under detailed slit-lamp examination. Severity of the cataracts included a subtle unilateral zonular cataract with 20/20 visual acuity, bilateral inner fetal nuclear pulverulent opacities with 20/16 visual acuity in both eyes, and dense unilateral and bilateral nuclear cataracts requiring early surgical removal. Incorporating the historic data on patients who were not examined, we found 48 affected members (28 unilateral, 17 bilateral, 3 obligate carriers who were not examined). CONCLUSIONS: Hereditary cataracts typically are symmetric in affected individuals. The authors describe a large pedigree with the apparently random expression of an autosomal dominant gene as either unilateral or bilateral cataract. To their knowledge, this is the first such family described in the literature. Currently, work is under way to determine if the causative gene is linked to previously defined cataract loci on chromosomes 1, 2, or 16.

Binocularity in accommodative esotropia.

One hundred twenty-seven medical records of patients with accommodative esotropia met our inclusion criteria and were analyzed. All included patients were within 10 prism diopters of orthophoria and had stereopsis and other binocular sensory test results recorded at their latest visit. Bifixation, defined as stereopsis of 50 arc seconds or better, was present in 31 patients (24%) with an average follow up of 89 months. Monofixation (peripheral fusion) was present in the remaining 96 patients (76%) with an average follow up of 84 months. Patients with bifixation were less likely to have presented with constant esotropia (19% vs 39% [P = .04]) and were more likely to be aligned within 8 delta of orthophoria in their first glasses (84% vs 21% [P < .0001]). No patient with bifixation had constant esotropia longer than 4 months. In addition, patients with bifixation were less likely to have worn bifocals (39% vs 59% [P = .09]), or undergone esotropia surgery (23% vs 62% [P < .0001]). These data suggest that maintenance of bifixation is possible in accommodative esotropia if the eyes are straightened before or shortly after the esodeviation becomes constant. With this early therapy, amblyopia and deterioration of ocular alignment are also less likely.

Long-term visual results and complications in children with aphakia. A function of cataract type.

PURPOSE: Previous studies of outcome in children with aphakia have approached the data by grouping patients according to features such as age at surgery, type of procedure, or some other common attribute. The purpose of this study is to identify factors predictive for visual outcome and complications in pediatric patients with cataracts. METHOD: One hundred seventy-four eyes in 118 patients underwent lensectomy and anterior vitrectomy for congenital or juvenile cataracts. All received early optical correction, occlusion therapy when necessary, and follow-up for at least 6 months. Visual outcome and complications were analyzed statistically to determine predictive factors. Features analyzed included cataract type, laterality, age at onset, follow-up, and corneal size. RESULTS: Statistical analysis showed that the most important predictor of long-term visual outcome and complications is cataract type. Visual outcome differed significantly by cataract type, with best results in the lamellar and posterior lentiglobus groups. Unilateral cases had a mean acuity lower than bilateral cases. Other factors, such as age at surgery and corneal size, were less predictive but closely linked to cataract type. Complications, such as aphakic glaucoma, also were more closely linked to the type of cataract than to other variables. CONCLUSION: The results indicate that an important determinant of long-term outcome and complications in aphakic children is cataract type. Other features were found to be closely correlated to cataract type and were not independently significant.