Comparison of physician and artificial intelligence-based symptom checker diagnostic accuracy

Symptom checkers are increasingly used to assess new symptoms and navigate the health care system. The aim of this study was to compare the accuracy of an artificial intelligence (AI)-based symptom checker (Ada) and physicians regarding the presence/absence of an inflammatory rheumatic disease (IRD). In this survey study, German-speaking physicians with prior rheumatology working experience were asked to determine IRD presence/absence and suggest diagnoses for 20 different real-world patient vignettes, which included only basic health and symptom-related medical history. IRD detection rate and suggested diagnoses of participants and Ada were compared to the gold standard, the final rheumatologists’ diagnosis, reported on the discharge summary report. A total of 132 vignettes were completed by 33 physicians (mean rheumatology working experience 8.8 (SD 7.1) years). Ada’s diagnostic accuracy (IRD) was significantly higher compared to physicians (70 vs 54%, p = 0.002) according to top diagnosis. Ada listed the correct diagnosis more often compared to physicians (54 vs 32%, p < 0.001) as top diagnosis as well as among the top 3 diagnoses (59 vs 42%, p < 0.001). Work experience was not related to suggesting the correct diagnosis or IRD status. Confined to basic health and symptom-related medical history, the diagnostic accuracy of physicians was lower compared to an AI-based symptom checker. These results highlight the potential of using symptom checkers early during the patient journey and importance of access to complete and sufficient patient information to establish a correct diagnosis.

[Indication and Results of the Anderson Procedure]

The major goal of extraocular muscle surgery for nystagmus is to reduce the abnormal head turn (AHT) which is caused by an eccentric null zone of the nystagmus. Shifting the null zone to the primary gaze position will eliminate the AHT. The Kestenbaum procedure consists of bilateral recession of the yoke muscles opposite to the AHT, combined with bilateral resection or plication of their antagonists. The Anderson procedure is confined to bilateral recession of the yoke muscles and is therefore less invasive. We report on our experience with the Anderson procedure. Patients and Methods: From September 2013 to June 2015, we performed the Anderson procedure in 11 consecutive orthotropic patients with infantile idiopathic or sensory defect nystagmus. Patients responsive to convergence inducing prisms who could benefit from artificial divergence surgery were excluded. Results: Medians and ranges (minimum-maximum) were: Age 7 years (4-30); binocular BCVA 0.5 (0.05-1.0); AHT 30° (20-40); equal recessions on the horizontal yoke muscles opposite to the AHT of 12 mm (10-17), in one case using bovine pericardium grafts. Three (3-6) months post surgery, the AHT was reduced to 7° (0-20). First step success rates, defined by residual AHT ≤ 10° and ≤ 15°, were 73 % (95 % CI 39-93 %) and 82 % (95 % CI 48-97 %). No over-correction or other adverse effects were observed. Two patients later received augmenting surgery. One patient with pre-existing exophoria later required strabismus surgery for exotropia. Conclusion: The AHT can be significantly reduced or completely corrected by the Anderson procedure. Recessions of at least 10 mm on both yoke muscles were performed. The success rates equaled success rates of augmented Kestenbaum surgery. Compared to the latter, the Anderson procedure is less invasive. It is followed by a shorter healing process. It is a vessel sparing method - an advantage for potential future surgery.

[Bilateral medial rectus recession with posterior fixation suture for large infantile esotropia]

BACKGROUND

Surgery for infantile large angle esotropia is not uniform. Bilateral medial rectus recession (BMR), combined recess-resect procedure, also combined with simultaneous contralateral medial rectus recession or secondary other procedures are common. Alternatively, bilateral medial rectus recession with posterior fixation suture (BMRF) has been used. We analysed the effect of BMRF for this specific indication.

PATIENTS AND METHODS

We undertook a retrospective evaluation of squint angles in simultaneous (S) and alternating (A) prism cover test before and 3 months after BMRF with and without additional oblique muscle surgery as primary surgery for esotropia ≥ 20° performed at our department between 1997 and 2009, as well as the rate of second procedures.

RESULTS

Sixty-one children (0.5 % of all patients who received eye muscle surgery during the same time interval) were included. Medians (10 % and 90 % quantiles) were: age at surgery 48.4 months (23.6; 76.0), refraction (spherical equivalent)2.25 dpt (0.25; 5.50), posterior fixation 5.5 mm + 13.0 mm (12.5; 13.0) from limbus, recession 5.0 mm (4.0; 5.0), inferior oblique recession in 29 children (27 bilateral), preoperative squint angles at 5 m S/A 29° (20; 40), at 0.3 m S/A 35° (24; 45), postoperative at 5 m S 0° (-6; 10), A 2° (-6; 11), at 0.3 m S 1° (-5; 12), A 3.5° (-5; 13), S ≤ 5° in 70.2 % at 5 m and 60.3 % at 0.3 m, consecutive exotropia 6-10° and > 10° in 7.0 and 3.5 % at 5 m and 8.6 and 1.7 % at 0.3 m, residual esotropia 6-10° and > 10° in 10.5 and 8.8 % at 5 m and 13.8 and 15.5 % at 0.3 m. Seven children (11.5 %) were re-operated for esotropia, four for exotropia (6.6 %).

CONCLUSION

Bilateral medial rectus recession with retroequatorial myopexy (Cüppers procedure) is an effective one-step procedure for large infantile esotropia. In roughly two-thirds of the cases, the squint angle was corrected within ± 5° with one surgery, which is similar to reported success rates of BMR.

How to deal with diplopia

Diplopia is a frequent neuro-ophthalmologic symptom with diverse etiologies. This article describes elementary diagnostic tests and frequent causes of diplopia. Monocular diplopia persists when the other eye is closed and usually disappears when the patient looks through a pinhole. It is usually caused by errors in the optical media of the eye and has to be differentiated from spectacle-induced side effect and non-organic disorders. A sign of non-organic etiology is absence of change in image position when the head is tilted. Binocular diplopia disappears regardless of which eye is closed. Binocular diplopia occurs when the images of both eyes cannot be fused. The most frequent direct cause of diplopia is acquired strabismus. Knowledge of several specific types of strabismus enables efficient patient management. Congenital and decompensating strabismus like accommodative esotropia, pathophoria, strabismus surso- and deorsoadductorius, retraction syndrome, Brown's syndrome and esotropia in high myopia only need ophthalmologic treatment. Orbital injury, orbital tumor, ocular myositis, Graves orbitopathy and vascular disease usually require multidisciplinary management. Neurogenic paresis, superior oblique myokymia, ocular neuromyotonia, myasthenia, chronic progressive external ophthalmoplegia (CPEO), internuclear ophthalmoplegia (INO) and skew deviation require specific neurologic examination. Treatment of diplopia includes treatment of the fundamental disorder, monocular occlusion, prisms and strabismus surgery.

[Surgery for strabismus sursoadductorius (congenital superior oblique palsy) in childhood]

PURPOSE

The aim of this study was to evaluate the effect of inferior oblique muscle recession (IOR) in children with pure unilateral strabismus sursoadductorius (so-called congenital superior oblique palsy, CSOP) operated before age 11 years.

PATIENTS AND METHODS

A retrospective study of IOR in children with unilateral CSOP and surgery before age 11 years was undertaken. In most cases, recession and anteroposition of the anterior part of the inferior oblique tendon next to the lateral edge of the inferior rectus muscle was performed without fixation of the posterior part of the tendon. Main outcome measures were change in abnormal head tilt, change in vertical deviation, both in straight and contralateral side gaze, and evaluation of squint angles.

RESULTS

Between 1997 and 2007, 36 consecutive children (aged 2 -10 years; 27 boys, 9 girls) received IOR for unilateral CSOP. The dose of IOR ranged between 6 and 12 mm. Vertical deviation in straight and contralateral gaze was reduced from median 5° (range 0 - 11°) and 12° (3 - 20°) to 0° (-2 - 8°) and 1° (-5 - 13°), respectively. Abnormal head tilt towards the contralateral shoulder was reduced from median 10° (0 - 20°) to 0° (-2,5 - 10°). Three children (8 %) received further extraocular muscle surgery within 2 years, one because of persistent hyperdeviation, and two because of consecutive hypodeviation of the operated eye.

CONCLUSIONS

The results indicate that IOR with fixation of only the anterior part of the inferior oblique to the sclera is an effective treatment for strabismus sursoadductorius/CSOP in children. Undercorrection into a residual, well compensated stage is a satisfying result. Both overcorrection and elevation deficiency were rare.

[Comparison of visual acuity measured using Landolt-C and ETDRS charts in healthy subjects and patients with various eye diseases]

PURPOSE

Results of visual acuity determination can differ depending on the stimuli being used, even if their critical details appear under the same visual angle. In this study, visual acuity measured with the Landolt C was compared to acuity measured with ETDRS charts in subjects with and without visual disorders.

PATIENTS AND METHODS

One hundred patients (age 8 to 90 years) with strabismus amblyopia (39), refractive amblyopia (5), cataract (24) and maculopathy (32) as well as 13 healthy volunteers (age 18 to 33 years) were examined. Retro-illuminated ETDRS 1, 2 and R charts (Lighthouse) and a retro-illuminated Landolt C chart with the same arrangement of optotypes (Precision Vision) were used. Three out of 5 optotypes in each line had to be correctly identified. In the patient group, the eyes with the lower visual acuity were tested, while the right eyes of the healthy subjects were monitored. Wrong answers were monitored and the results were noted in interpolated logMAR.

RESULTS

Differences between Landolt C (LC) and ETDRS acuity were only small and statistically not significant. LogMAR values (SEM in parentheses) for LC /ETDRS 1 were: entire group: 0.60 (0.04)/ 0.55 (0.04), strabismus amblyopia: 0.85 (0.08)/ 0.80 (0.08), refractive amblyopia: 0.27 (0.04)/ 0.23 (0.05), cataract: 0.57 (0.07)/ 0.51 (0.07), retinal disease: 0.67 (0.06)/ 0.61 (0.06), healthy eyes: -0.17 (0.03)/ -0.17 (0.02). The mean difference between LC and ETDRS 1 was 0.49 lines in the entire group and 0.51 lines in strabismus amblyopia in favour of ETDRS 1 values. ETDRS 2 and R charts yielded similar results.

CONCLUSIONS

In healthy subjects and in patients with various eye disorders including strabismus amblyopia, there was only a slight difference between visual acuity measured by ETDRS charts compared to the Landolt C. Comparing data of different settings it must be considered that in the lower visual acuity range (< 0.32), the mean ETDRS acuity of adults overestimates the Landolt C acuity by 0.5 and 1.0 line.

[Diagnosis and treatment of trochlear nerve palsy]

The diagnosis of unilateral trochlear nerve palsy is based on acute onset vertical deviation which increases in contralateral side gaze, down gaze and ipsilateral head-tilt together with excyclodeviation which also increases in both down gaze and ipsilateral head-tilt. Both vertical deviation and excyclodeviation decrease in contralateral head-tilt. To detect excyclotropia one must ask the patient whether there is a tilted double image in down gaze. Bilateral trochlear nerve palsy causes a change of vertical deviation between right and left gaze and between head-tilt to the right and to the left shoulder. In severely asymmetric bilateral palsy, this change of vertical deviation may be absent. Bilateral symmetric trochlear nerve palsy regularly causes only slight vertical deviation in side gaze and slight head-tilt phenomenon. Major symptoms of symmetric palsy are significant excyclodeviation increasing in down gaze and V-incomitance. Objective assessment of vertical and eventually horizontal deviation is performed by the alternate prism and cover test. Cyclodeviation can be measured by Maddox rods. Differentiated assessment of subjectively localised horizontal, vertical and cyclotorsional deviations in definite gaze directions is preferably being performed at the Harms tangent scale. Treatment of trochlear nerve palsy is nearly exclusively surgical. Prisms are rarely helpful due to incomitance of vertical deviation and since they are not suitable to correct for cyclodeviation. Surgery should be scheduled not earlier than 12 months after onset of the palsy. The preferred surgical strategies include weakening procedures on the inferior oblique, tucking or advancement of the superior oblique tendon, combination of both and, if fitting with the motility pattern rarely as a primary procedure, but usually as a possible second procedure contralateral inferior rectus recession. Surgery will not alter the neurogenic palsy but it modulates the squint angle pattern resulting from the movements of both eyes. Normal binocular vision in all directions of gaze for slight palsy and in large part of the daily used gaze area for severe palsy can be achieved by one or sometimes two operations.

[Influence of prism overcorrection on residual postoperative strabismus]

BACKGROUND

Prism overcorrection is a complementary procedure to reduce the residual postoperative esotropia caused by anomalous retinal correspondence (ARC) after surgery for esotropia. We have investigated the results of this treatment.

PATIENTS AND METHODS

For Group 1, the files of 63 patients treated with postoperative prism overcorrection in the Department of Ophthalmology, University of Giessen, were evaluated regarding the pre-and postoperative squint angles (SPCT, simultaneous and APCT, alternate prism and cover test) and the angle of ARC, determined by the red filter test and by the increase of esotropia after neutralisation of the squint angle (APCT). Postoperatively, squint angles had been measured immediately (APCT) after removal of the eye patch and 10 minutes to 2 hours later (SPCT and APCT). Subsequently, prism overcorrection was performed with a Fresnel prism foil (40 PD basis temporally) in front of the fellow eye for a maximum of 3 months. After 3 months, SPCT and APCT were performed. For Group 2, the files of 28 patients with a preoperative angle of ARC of 5 degrees or more, treated in the Department of Ophthalmology, University of Heidelberg, were evaluated. These patients had not been treated with prism overcorrection. The squint angles had been measured (SPCT and APCT) on the preoperative day, on the first postoperative day, a few hours after removing the eye patch, and after three months.

RESULTS

For Group 1, at surgery, the patients were 4 to 12 years old (median: 6.2 years). The preoperative squint angle ranged from + 5 degrees to + 27 degrees (median: + 12 degrees) in the SPCT and from + 7 degrees to + 27 degrees (median: + 14 degrees) in the APCT. The angle of ARC was between + 4 degrees and + 15 degrees (median: + 7 degrees). Both combined recess and resect surgery (with or without additional oblique muscle surgery) or bilateral retroequatorial medial rectus myopexy, in part depending on the squint angle pattern with medial rectus recession, were performed. Immediately after removing the patch, the squint angle (APCT) was between - 10 degrees and + 5 degrees (median: + 1 degrees). Ten minutes to 2 hours later, the manifest squint angle ranged from 0 to + 12 degrees (median: + 7 degrees). The angle had decreased significantly to - 6 to + 12 degrees (median: + 5 degrees) after 3 months. For Group 2, the patients' ages were between 5 and 12 years (median: 6.5 years). The squint angles ranged from + 11.5 degrees to + 35 degrees (median: + 20 degrees) in the SPCT and APCT. The angle of ARC was between + 5 degrees and + 17 degrees (median: + 8 degrees). Combined recess and resect surgery or bilateral recession of the medial rectus (with or without oblique muscle surgery both) were performed. The SPCT several hours after removal of the patch showed angles of - 4 degrees to + 14 degrees (median: + 4.25 degrees). Three months later the manifest squint angles ranged from - 5 degrees to + 14 degrees (median: + 3 degrees).

DISCUSSION

After prism overcorrection (Group 1), there was a significant reduction of the residual esotropia. Without this additional treatment (Group 2), there was no significant change in the postoperative squint angle. However, neither the positive outcome in Group 1 nor the difference to Group 2 do unequivocally prove that there is a beneficial effect of prism overcorrection, since preoperative conditions were different and the sample size in Group 2 was small, especially after matching for equal preoperative conditions. A spontaneous reduction of the postoperative esotropia cannot be excluded. Further studies are necessary in order to investigate the specific effect of prism overcorrection.

Systematische Fehler bei der fotografischen Beurteilung der Hornhautspiegelbilder

BACKGROUND

The growing popularity of digital imaging leads to an increasing number of photos transferred by parents via E-mail to an ophthalmologist, showing a child with a displacement of corneal reflections. This must not necessarily lead to the diagnosis of manifest strabismus.

MATERIALS AND METHODS

The displacement of the first Purkinje image is demonstrated by moving the flash of a digital camera sideways from the objective. Photographs were taken at a distance of 0.6 m while the healthy test subject was looking into the camera. Flashlight was displaced gradually up to 20 cm to the left side of the objective. The resulting displacement of the corneal reflections was measured after transferring the photos to a computer.

RESULTS

Displacement of the source of light by 10 cm resulted in a displacement of the first Purkinje image of about 1 mm, i. e., about 0.1 mm per degree.

CONCLUSIONS

Displacement of corneal reflection was 0.1 mm per degree. Asymmetry of corneal reflections is twice as much, since the corneal reflections are displaced in the same direction on both eyes. Lateral displacement of the flash from the objective of the camera by 2.5 cm results in an asymmetry of 0.5 mm, thus suggesting a squint angle of 6 degrees. Vice versa, a real strabismus can be masked. This bias can be avoided by using the camera with the flash above the objective in relation to the patient's interpupillar axis. Nevertheless, it is impossible to diagnose or to exclude a microstrabismus by this method itself, because an angle kappa, if it is different on both eyes, can also mimic or mask a manifest strabismus.

[Landolt C and snellen e acuity: differences in strabismus amblyopia?]

BACKGROUND

Assessment of visual acuity depends on the optotypes used for measurement. The ability to recognize different optotypes differs even if their critical details appear under the same visual angle. Since optotypes are evaluated on individuals with good visual acuity and without eye disorders, differences in the lower visual acuity range cannot be excluded. In this study, visual acuity measured with the Snellen E was compared to the Landolt C acuity.

PATIENTS AND METHODS

100 patients (age 8 - 90 years, median 60.5 years) with various eye disorders, among them 39 with amblyopia due to strabismus, and 13 healthy volunteers were tested. Charts with the Snellen E and the Landolt C (Precision Vision) which mimic the ETDRS charts were used to assess visual acuity. Three out of 5 optotypes per line had to be correctly identified, while wrong answers were monitored. In the group of patients, the eyes with the lower visual acuity, and the right eyes of the healthy subjects, were evaluated.

RESULTS

Differences between Landolt C acuity (LR) and Snellen E acuity (SE) were small. The mean decimal values for LR and SE were 0.25 and 0.29 in the entire group and 0.14 and 0.16 for the eyes with strabismus amblyopia. The mean difference between LR and SE was 0.55 lines in the entire group and 0.55 lines for the eyes with strabismus amblyopia, with higher values of SE in both groups. The results of the other groups were similar with only small differences between LR and SE.

CONCLUSION

Using the charts described, there was only a slight overestimation of visual acuity by the Snellen E compared to the Landolt C, even in strabismus amblyopia. Small differences in the lower visual acuity range have to be considered.

Okuläre Neuromyotonie - Ein Fallbericht

BACKGROUND

Ocular neuromyotonia is a rare ocular motility disorder characterized by involuntary contractions of one or several ocular motor muscles. In this report a typical case is presented.

PATIENT AND METHODS

A 61-year-old female patient was referred with persistent diplopia despite previous surgical treatment for right 6 (th) nerve palsy. The palsy was caused by a meningeoma of the petrous bone, which had been incompletely resected. Subsequently, the patient had received radiation therapy. Strabismological and neuroophthalmological examinations were performed. The results coincide with data collected in our department from three other patients with ocular neuromyotonia (2 cranial nerve VI, 1 cranial nerve IV), over the past three years.

RESULTS

The patient showed orthophoria at distance (5 m) and an exophoria of 6 degrees at near vision. The abduction and adduction of the right eye were restricted to 40 degrees and 35 degrees , respectively. After several seconds of eccentric gaze to the right, the right eye remained in an abducted position of approximately 25 degrees . The gaze to the left led to a retraction instead of an adduction of the right eye. The spasm of the lateral rectus muscle resolved after some seconds, returning to the aforementioned right eye motility. Under oral treatment with carbamazepine, initially 200 mg, later increasing to 400 mg per day, the symptoms improved significantly, did not resolve entirely, however.

CONCLUSIONS

These typical findings permit the diagnosis of ocular neuromyotonia. The characteristic symptoms of ocular neuromyotonia and the typical history of a previous intracranial tumor, treated neurosurgically with adjuvant radiotherapy, lead to the hypothesis that ephaptic transmission in the cranial nerve is the underlying pathophysiological mechanism in the development of ocular neuromyotonia. Hereby, efferent impulses from non-twitch motoneurons could activate neighbouring axons, and spread both peripherally and centrally. Beside other mechanisms discussed, an involvement of proprioceptive elements and their reafference is also a possible cause for the prolonged muscle contraction.

Operationsergebnisse bei kongenitalem Brown-Syndrom

BACKGROUND

There are various surgical procedures for the treatment of congenital ("true") Brown's syndrome. We have evaluated the effects of a superior oblique tendon recession.

PATIENTS AND METHODS

In a retrospective study, we evaluated the files of 22 patients who received surgery for congenital Brown's syndrome in our department. A recession of the superior oblique tendon was performed, when there was a hypotropia in primary position with an abnormal head posture and a significant elevation deficit in adduction, and when these findings did not improve spontaneously. The squint angles (alternate prism and cover test), the monocular motility and the abnormal head posture at distance fixation were assessed. The measurements were performed 1 day before and 3 months after surgery. Thirteen patients were examined 2 - 10 years after surgery.

RESULTS

At the time of surgery, the patients were 4 - 17 years old (median 7 years), 13 were male, in 15 patients, the right eye was concerned. Eight patients had an additional esotropia, one patient was exotropic. The vertical deviation in straight gaze was 0 - 12 deg (median 7 deg). The elevation of the eye was restricted to - 10 deg (below horizontal) to 15 deg (median 0 deg) in adduction and to 10 - 35 deg (median 25 deg) in abduction. Sixteen patients had an abnormal head posture. The superior oblique tendon was recessed by 10 mm, in some patients with an additional loop (6x0 polyester). Nine patients received simultaneous surgery for their eso/exotropia. At the end of the operation, the elevation of the eye in adduction (forced duction test) was free. Three months postoperatively, the vertical deviation was 0 - 6 deg (median 1 deg). Twelve patients did not show any abnormal head posture. Inspite of free passive motility, the monocular elevation in adduction was only slightly improved to - 5 to 15 deg (median 5 deg). At the late control, the hypotropia (0 - 4 deg, median 0 deg) and the elevation in adduction (5 - 35 deg, median 15 deg) were significantly improved.

CONCLUSION

The recession of the superior oblique tendon is an effective and safe surgical procedure for congenital Brown's syndrome. The efficiency of the procedure is individually variable. Presumably, this variability was caused by the heterogenous etiology of Brown's syndrome rather than by surgical technique. The hypotropia and the abnormal head posture were reduced immediately after surgery, while the delayed improvement of active elevation in adduction often remained incomplete. Postoperative forced upgaze training may be beneficial.

[Head-tilt test in unilateral and symmetric bilateral acquired trochlear nerve palsy]

BACKGROUND

The head-tilt phenomenon (difference between the vertical deviations with an ipsilateral and contralateral head-tilt by 45 deg. each) occurring in patients with a superior oblique palsy has traditionally been explained by the lacking contraction of the superior oblique muscle within the synkinetic movement of ocular counterrolling. However, using a computer model, Robinson showed that the superior oblique palsy itself causes only a relatively small head-tilt phenomenon. Adaptive mechanisms amplifying the otolith reflex were suggested to explain the increase of the head-tilt phenomenon in the course of time. In order to reduce the abnormal head posture required for binocular vision, the otolith reflex would be amplified, accepting the greater vertical deviation when the head is tilted to the paretic side .

QUESTION

If the head-tilt phenomenon were solely caused by the lacking contraction of the superior oblique muscle, it should be greater in bilateral than in unilateral superior oblique palsies. If an adaptive mechanism were acting to reduce the abnormal head posture, the head-tilt phenomenon should not be greater, and could even be smaller in bilateral than in unilateral superior oblique palsy, because in bilateral (symmetric) trochlear nerve palsies the vertical deviation at straight gaze is already small or absent without adaptation.

PATIENTS AND METHODS

We have carried out a retrospective comparison of 10 patients with bilateral symmetric superior oblique palsies and 10 patients with unilateral superior oblique palsy. In all cases, the palsy was acquired and had been present for at least 1 year.

RESULTS

The patients with bilateral superior oblique palsy had a head-tilt phenomenon ranging from 0 to 7 degrees (median, 2 deg.). The patients with unilateral superior oblique palsy had a head-tilt phenomenon between 2 and 13 degrees (median, 8 deg.). The difference was significant (p = 0.0117).

CONCLUSIONS

The head-tilt phenomenon is smaller in long-standing bilateral symmetric superior oblique palsies than in long-standing unilateral superior oblique palsy. This finding supports the hypothesis that in unilateral superior oblique palsy, an adaptive mechanism augments the head-tilt phenomenon by an amplification of the otolith reflex. However, we presume that the amplification of the otolith reflex is only a side effect of the adaptive change of the vertical fusional vergence tonus and thus the price of the improved vertical fusion, rather than a compensatory mechanism.

Die Darstellung der Sehschärfe in ophthalmologischen Publikationen

BACKGROUND

Visual acuity is one of the most important functions of the visual system. Visual acuity is the basis of many decisions in clinical practice. The assessment of visual acuity is clearly defined (norm EN ISO 8596). In this study, the presentation of results of visual acuity assessments in the ophthalmological literature was analysed.

MATERIALS AND METHODS

All the issues of the journals "Klinische Monatsblatter fur Augenheilkunde" and "Der Ophthalmologe" of the years 2002 and 2003 were reviewed especially concerning the procedure of visual acuity assessment, the scaling in the lower visual acuity range, axis scaling and the calculation of mean values of visual acuity.

RESULTS

In total, 550 publications were reviewed. Of these papers, 207 contained at least one visual acuity value and 42 papers presented detailed data concerning either the change of visual acuity over a certain time interval, or mean values, or using charts. A linear scale was used in 9 of 28 papers with presentation of visual acuity measurements in a chart. Of 32 publications with visual acuity measurements less than 0.2, only 2 used a logarithmic scale in the lower visual acuity range, while in 14 papers, scaling was rather rough or not numeric (e. g., counting fingers). Sixteen papers used the units "finger counting" or "hand movements" to describe low visual acuities. The way of calculating mean values remained obscure in 36 papers.

CONCLUSIONS

Regarding a correct assessment of visual acuity and the effect of therapy, the fundamental guidelines of visual acuity assessment and its correct presentation should be considered.

[Strategies of visual acuity assessment]

Visual acuity can be assessed by different strategies. The constant-stimulus-, the stair-case-, the Best-PEST-strategies, and the EN ISO 8596 are discussed. In cases of presumed psychogenic visual impairment and malingering it can be useful to modify these strategies striving for a determination of the (minimum) visual acuity based on statistical analysis rather than "clinical experience". The EN ISO 8596 defines visual acuity by a 60 % criterion, thus implying guesswork, if recognition of the optotypes is uncertain. Therefore, the forced-choice-procedure is mandatory. Objective psychophysical (preferential looking, induction or suppression of rhythmic eye movements) and electrophysiological methods (VEP) of visual acuity assessment can be useful in infants, in the mentally handicapped, and in patients with presumed psychogenical influence or malingering.

Probleme bei der augen�rztlichen Bescheinigung von Blindheit

BACKGROUND

We compared the medical test results of 117 persons examined by the superintendent for blindness assessment in 2002 with their certificates of blindness (5.5% of the applications, 42% of the testimonial examinations performed in Hessen in 2002).

METHODS

If the ratings as "blind" or "severely visually handicapped" (corresponding to a visual acuity of not more than 0.02 or 0.05, resp.) differed between the medical test and the certificate, visual acuity, visual field, further findings, and the methods of assessment were analyzed on the basis of the medical records.

RESULTS

The medical test confirmed 75 certificates. Fourteen persons with a certificate of blindness were graded as severely visually handicapped by the medical test. In 8 and 12 cases, respectively, the criteria of neither blindness nor severe visual handicap were fulfilled. Eight persons with a certificate of severe visual handicap were graded as blind by the medical test.

DISCUSSION

In 29% of the cases, the visual handicap did not reach the certified grade. Striking differences occurred between the certificate and the functions shown in the medical test. In the certificates, the declared visual handicap was regularly judged to correspond to the objective findings, but apparently in these cases symptom validity had not been critically assessed. An improvement of diagnostic validity could be achieved using relatively uncomplicated subjective and objective tests.

Dissoziierte Naheinstellungstrias mit akkommodativem Konvergenzexzess

We report on an 8-year-old boy whose near reflex could be elicited exclusively when the left eye was fixing (LF) but not when the right eye was fixing (RF). With RE +1.25/-1.25/169 degrees and LE +1.0/-0.75/24 degrees, the visual acuity was 1.0 OU at 5 m and RE 0.5, LE 1.0 at 0.3 m improving to 1.0 OU by a near addition of 3.0 D. Stereopsis was 100 degrees (Titmus test). The prism and cover test revealed an esophoria of 4 degrees at 5 m. At 3 m there was an esophoria of 6 degrees (RF) and an esotropia of 28 degrees (LF), compensating to an esophoria of 3 degrees (RF/LF) with a near addition of 3.0 D. Accommodation and the pupillary near reaction (OU) were hardly elicitable during RF. During LF, retinoscopy revealed an accommodation of 8 D (OU) and the pupils constricted normally. Correction by bifocal glasses yielded orthotropia with random dot stereopsis at near.

Kestenbaum and artificial divergence surgery for abnormal head turn secondary to nystagmus. Specific and nonspecific effects of artificial divergence

Recommendations concerning the kind and dosage of eye muscle surgery for nystagmus vary in the literature. The present paper is an evaluation of the effects of Kestenbaum and artificial divergence surgery on abnormal head posture in a retrospective study. Exclusively patients with surgery for nystagmus-related horizontal head-turn (HT), with binocular vision and without previous eye muscle surgery were considered. Of the 78 patients, aged 3 to 68 years, 52 had a HT to the left side; 47 patients were male. In the Kestenbaum group (n = 31), the preoperative HT of 30 degrees (20-40) (median, 0.1-0.9 quantile) was reduced to 10 degrees (0-30) by surgery of 14 mm (10-20) on each eye. Four patients received further surgery. In the artificial divergence group (n = 27), the HT of 30 degrees (25-40) was reduced to 5 degrees (0-20) by recess-resect surgery of 10 mm (7-12) on the adducted eye. Seven patients needed further surgery. In the combined Kestenbaum plus artificial divergence group (n = 20), the HT of 30 degrees (25-40) was reduced to 7 degrees (-5-15) by surgery of 29 mm (21-37) on both eyes together. No further surgery was necessary. Kestenbaum surgery had a similar effect/dose ratio as recess-resect surgery for strabismus. If a test with base-out prisms suggests that artificial divergence is promising, this concept is preferable. It can be integrated into Kestenbaum surgery.

[Dissociated horizontal deviations (DHD): nomenclature and etiology. An orientating attempt in terminological confusion]

PURPOSE

To classify dissociated horizontal deviations (DHD) based on the etiology of the vergence that causes the dissociation of the squint angle.

METHODS

Dissociated strabismus can reliably be diagnosed by a change of the squint angle caused by an alternation in the fixation from one eye to the other, when all the other conditions (head posture, direction of gaze, fixation distance, accommodation) remain unchanged. The decisive diagnostic tool is the reversed fixation test: During monocular fixation with one eye, the squint angle of the other eye is neutralized using a synoptometer or a prism. Then, the fixation is changed to the other eye, which keeps its position behind the prism. If the change in fixation causes a change in the position of the previously fixating eye, the deviation is dissociated. If the position of the previously fixating eye does not change, the deviation is not dissociated.

RESULTS

Dissociated strabismus can be detected and differentiated from both comitant and incomitant non dissociated strabismus by the reversed fixation test. The dark red glass test is less sensitive and less specific for dissociated strabismus than the reversed fixation test, if a difference in accommodative convergence is excluded, possible causes of DHD are nystagmus-attenuating convergence, substitution of version eye movement by convergence, and a horizontal side effect of the vertical eye muscles in asymmetric DVD.

CONCLUSION

Dissociated strabismus is an effect of vergence which is brought about by the change in the fixation or dominance from one eye to the other eye or in the interocular ratio of afferent input (luminance). Dissociated strabismus can be classified based on its direction or due to its etiology.

[The closed Landolt ring--a handy test for evaluating suspected simulation]

PURPOSE

We present a visual acuity test for proof of malingering and psychogenic impairment of visual acuity.

METHOD

The book contains 36 plates. On 32 plates, a Landolt-C is shown with a gap of 10 minutes of arc, thus corresponding to a visual acuity of 0.1, when applied at a distance of 1 metre. Each of the 4 alternatives of the Landolt-C occurs eight times in random order. Starting at position 21, four plates are interspersed showing a closed circle of the same size. The test is used at a distance corresponding to an acuity level of maximum 50% of the presumed factual acuity. Following a four alternative forced choice paradigm, the tested person is requested to call the direction of the Landolt-C within about 2 seconds, when the plates of the book are turned over. The responses and their latency are recorded using a digital electronic system which allows later audiovisual analysis. The response on the first closed circle and its latency is compared to the previous responses. Two subjects were tested who tried to pretend a reduction of their visual acuity.

RESULTS

Malingering was proved by the verbal response of the first subject and by the long latency of the response of the second subject (4.0 s vs. 1.2 s-2.7 s for the previous responses). The entire test, explanation included, took less than 5 minutes.

CONCLUSION

This handy test can be a useful tool in cases suspect of malingering or psychogenic impairment of visual acuity.

Surgery for nystagmus related head turn: Kestenbaum procedure and artificial divergence

PURPOSE

An abnormal head posture adopted to reduce a nystagmus can be treated by Kestenbaum surgery or by creating an exodeviation which is compensated by convergence (artificial divergence). We evaluated the effects of Kestenbaum surgery and artificial divergence surgery in a retrospective study.

METHODS

Seventy-eight patients who received surgery for horizontal head turn (HT) due to nystagmus were included in the study. Exclusion criteria were previous extraocular muscle surgery, strabismus, lack of binocular vision, and cerebral disease. The millimetres of surgery and the findings before and 3 months after operation [HT, binocular visual acuity (VA), binocular vision (BV)] were evaluated. The patients were divided into three groups: the Kestenbaum group, the artificial divergence group, and the artificial divergence plus Kestenbaum group.

RESULTS

Of the 78 patients, aged 3-68 years, 52 had HT to the left side and 47 were male. In the Kestenbaum group (n=31), the median (10% and 90% quantile) HT was 30 degrees (range 20-40 degrees). A total of 28 mm (range 20-40 mm) surgery reduced the HT to 10 degrees (0-30 degrees). The efficacy of surgery was 1.4 degrees HT reduction per millimetre surgery on one eye (range 0.4-2.5 degrees). Four patients received further surgery. In the artificial divergence group (n=27), 10 mm (range 7-12 mm) surgery reduced the HT of 30 degrees (range 25-40 degrees) to 5 degrees (range 0-20 degrees). Seven patients received further surgery. In the artificial divergence plus Kestenbaum group (n=20), the HT was 30 degrees (range 25-40 degrees). A total of 29 mm (range 21-37 mm) surgery reduced the HT to 7 degrees (range -5 degrees to 15 degrees). No further surgery was performed. Postoperatively, the maximum VA and BV was available without large HT, but an increase in the absolute VA and BV could not be proved.

CONCLUSION

Artificial divergence is preferable or should be combined with Kestenbaum surgery, if possible. Kestenbaum surgery alone has an effect/dose ratio similar to recess-resect surgery for strabismus. Thus, to correct x degrees HT, 2/3x mm surgery on each eye is adequate.

[Unilateral aplasia of a lateral rectus muscle]

BACKGROUND

The congenital absence of an extraocular muscle is rare. The case of an unilateral lateral rectus muscle and a review of the literature are presented.

PATIENT AND METHODS

A healthy 7-year old boy with inconspicuous family history was seen in our clinic. The boy had been noted to have a right esotropia from infancy. Clinical orthoptical examinations and magnetic resonance imaging (MRI) were performed. The esotropia was corrected by transposition of the superior and inferior rectus muscle.

RESULTS

With correction of the myopic astigmatism the visual acuity of either eye was 0.8. The right eye could not abduct to pass the midline, the left eye passed the midline by 35 degrees. From the primary position the right eye was able to elevate by 20 degrees and the left eye to elevate 15 degrees. The alternate prism and cover test showed in either eye fixation an esotropia of 24 degrees without significant change in elevation or depression. Besides, there was a hypertropia (+VD) of 14 degrees which increased to 21 degrees in left gaze and decreased to 0 degree in right gaze. Indirect ophthalmoscopy showed a bilateral excyclo position of approximately 5-10 degrees. Retraction of either eye was not seen in any gaze direction. The axial length of the right/left eye was 25.2 mm/24.6 mm. Aplasia of the right lateral rectus muscle and hypoplasia of the left lateral rectus muscle could be demonstrated by magnetic resonance imaging. Intraoperatively the right lateral rectus muscle was absent. The vertical eye muscle inserted regularly. Hummelsheim's procedure was performed. Eight months postoperatively, the boy was orthotropic in primary position. The inferior oblique overaction was still present together with a "V" pattern of 8 degrees. The Bagolini test was positive.

CONCLUSION

The congenital absence of one or more extraocular muscles is a rare condition, which has to be considered as a differential diagnosis to neurogenic nerve palsy.

[Results of combined divergence operation in intermittent exotropia in 120 children]

BACKGROUND

Intermittent exotropia is the most frequent indication for surgical correction of exodeviations in childhood. Overcorrection with prolongated or persistent consecutive esotropia can impair binocular vision particularly in early childhood. We wanted to investigate this potential risk and the dose/effect relation of recess-resect surgery on children.

PATIENTS AND METHODS

120 children up to ten years of age underwent recess-resect surgery for intermittent exotropia in our clinic from 1991 to 1999 (< 2% of the surgical cases). The cycloplegic refraction was spectacle corrected with a reduction of 0.5 dpt. Preoperatively, a diagnostic occlusion was performed for three days. The amount of surgery was calculated using our dosage schedules based on effects one week postoperatively. The squint angles as measured by the alternate prism and cover test at 5 m and 0.3 m pre- and 3 months postoperatively and the binocular functions as measured by the Bagolini striated glasses, Titmus, Randot, TNO, or Lang tests were evaluated.

RESULTS

(Medians) Squint angles in primary position were: preoperative: distance (5 m)--15 degrees, near (0.3 m)--16 degrees; postoperative (n = 104); distance--4 degrees, near--3 degrees. Effectivity of surgery: distance: 1.3 degrees/mm, near 1.4 degrees/mm. Consecutive esotropia requiring surgical correction occurred in 1 child. Second surgery for intermittent exotropia in the years 1991 to 1999 was necessary in 5 children. Binocular functions (n = 95): Preoperative = postoperative: 61%, postoperative > preoperative 21%, postoperative < preoperative 18%. The diagnostic occlusion was helpful to differentiate "pseudo-divergence excess type" from "divergence excess type" exotropia. The average deviation did not increase under the diagnostic occlusion. The effectivity of surgery (degree/mm) in the children group was lower than in a compared group of older patients (> 10 years) with intermittent exotropia.

CONCLUSION

Using our own dosage schedules and surgical technique, residual exodeviations are common after recess-resect surgery in childhood. The risk of consecutive esotropia or persistent impairment of binocular vision is low.

[Congenital nystagmus: indication, results and dosage of Kestenbaum surgery in 34 patients]

BACKGROUND

Abnormal, nystagmus related head postures can be treated by Kestenbaum's procedure, if the concept of artificial divergence (Cüppers procedure) is not expected to work. In this retrospective study, we evaluated the effects of Kestenbaum surgery in order to establish dosage recommendations.

PATIENTS AND METHODS

Solely patients who received Kestenbaum surgery (maximum 3 mm dosage difference between both eyes, i.e., without additional artificial divergence) for a horizontal head turn (HT) due to nystagmus were included in this study. Exclusion criteria were previous eye muscle surgery, strabismus, lacking binocular vision, and cerebral disease. The millimetres of surgery and the pre- and 3-6 months-postoperative findings (HT and visual acuity at 5 m distance, stereopsis) were evaluated.

RESULTS

Of the 34 patients, 21 had a HT to the left side and 20 were male. The age at surgery (median, 10%- and 90%-quantile) was 7 years (4-32), the total amount of surgery 32 mm (20-40), and the preoperative HT 30 degrees (20-40). Postoperatively (n = 31), the HT amounted to 7 degrees (0-20). The reduction of HT was 67% (25-100), the efficacy of surgery 0.8 degree (0.3-1.0) per millimetre total amount of surgery on both eyes together. Four patients needed further surgery due to residual HT. Postoperatively, the maximum visual acuity was available without HT or with significantly less HT than preoperatively. Stereopsis showed a trend of improvement.

CONCLUSIONS

The Kestenbaum procedure has a dose/effect ratio similar to that of recess/resect surgery for strabismus. Due to a long term efficacy of 1.5 degrees/mm, a dosage (in millimetres) on each eye of two thirds of the HT (in degrees) can be recommended. Physiological and methodical factors (false measurements) have to be discussed as an explanation for apparently low efficacy of surgery.

[Pathophysiology, diagnosis and therapy of three congenital dacryocystoceles]

BACKGROUND

Congenital dacryocystocele has been rarely described in German literature. Congenital obstruction and distention of the lacrimal sac makes it necessary to differentiate for various causes.

PATIENTS AND METHODS

Three infants had congenital dacryocystocele. The diagnosis was made by sonography and was established by probing the lacrimal duct and nasal endoscopy that showed a white prominent tumor below the lowest conch.

RESULTS

Directly after endonasal and canalicular opening of the dacryocystocele clear liquid with white detritus drained, and the swelling decreased. No further procedure was needed.

CONCLUSION

The diagnosis of dacryocystocele can be made by inspection, probing the lacrimal duct, ultrasound and nasal endoscopy. If probing of the lacrimal duct could not easily open the Hasner's membrane, endonasal opening can be performed. The cooperation with an ear-nose-throat specialist could lead to the diagnosis of dacryocystocele and sufficient treatment without the need for any further radiological examinations.

Reduction of postoperative nausea and vomiting by dimenhydrinate suppositories after strabismus surgery in children

Although dimenhydrinate has been used for treatment and prevention of postoperative nausea and vomiting (PONV) since the fifties, there have been few controlled studies about its efficacy. We performed a double-blinded study of 301 children aged 4 to 10 yr who underwent strabismus surgery. Preanesthetic medication with midazolam (0.5 mg/kg) as well as application of either dimenhydrinate suppositories or a placebo preparation was performed 30 min before the induction of anesthesia. Anesthesia was induced with thiopentone (5-10 mg/kg) and vecuronium (0.1 mg/kg) and maintained with halothane (1%-2%) in N(2)O/O(2) (65%/35%). The incidence of PONV, requirements for rescue dimenhydrinate, and time to recovery were recorded. The overall incidence of PONV was 60.1% in the placebo group and 30.7% in the dimenhydrinate group. In the dimenhydrinate group, children had to be observed in the recovery room significantly longer than those in the placebo group. Children having received dimenhydrinate were discharged from the recovery room with lower arousal scores. We conclude that the rectal administration of dimenhydrinate is effective for the prevention of PONV, although the sedative effect may require longer postoperative monitoring.

IMPLICATIONS

We performed a double-blinded, randomized study to investigate the effects of prophylactic rectal dimenhydrinate application on postoperative nausea and vomiting in children undergoing strabismus surgery. In comparison with placebo, dimenhydrinate reduced the incidence of postoperative vomiting from 60.1% to 30.7%.

[Healing process and complications after eye muscle surgery]

BACKGROUND

Varying reports on the incidence of operative and postoperative complications following eye muscle surgery have been published. The purpose of this study was to quantify complications after various types of eye muscle surgery as well as minor pathological changes of the anterior and posterior segment.

PATIENTS AND METHODS

This prospective study included all patients who underwent eye muscle surgery at the Department of Strabismology and Neuroophthalmology, Giessen, from January to May 1998. Five hundred eyes of 377 patients aged 2-82 years were included. The spectrum of procedures comprised: recessions, resections, tucks, R&R procedures, transpositions, bimedial retroequatorial myopexies, and revisions of rectus and oblique muscles. All patients were examined 1 day preoperatively and 1 day, 1 week, and 3 months postoperatively. Any complications and even minor pathological changes of the anterior and posterior segment were documented. Some changes were assessed by means of a score (0-3).

RESULTS

One day postoperatively, 30% of eyes had inflammatory pseudoptosis, most of them mild. Conjunctival swelling and injection were frequently mild and moderate, after 1 week mostly mild. Conjunctival irritation was more pronounced following resection than tucking. Punctate epithelial keratopathy was noted in 1.6% of cases (first postoperative day), dellen in 4.3% (first postoperative week). Three months postoperatively, 14.3% of eyes had biomicroscopically visible conjunctival folds and 91.3% had minimal conjunctival scars. None of the patients had a scleral perforation or other serious complication.

CONCLUSIONS

Eye muscle surgery rarely entails complications. Revisions due to organic pathological changes are extremely rare. Possible development of dellen requires check-up 4-7 days postoperatively. Tucking of rectus muscles causes less conjunctival irritation than resection.

[Vertical vergence in convergence]

PURPOSE

To report on a 7-year-old boy with a small left-over-right deviation (-VD) which increased when the head was tilted to the left shoulder and during convergence.

METHODS

The squint angles were measured by the unilateral and alternate prism cover test at distance and near fixation when the head was in ortho-position and when it was tilted.

RESULTS

At distance fixation (D) there was a latent deviation of-VD 3 degrees. With near fixation (N) at 0.3 m the vertical phoria increased to-VD 18 degrees. The angle of deviation was not influenced by (N) convex lenses in front of the fixating eye despite an adequate dis-accommodation. The-VD was fairly comittant in right and left gaze. At 45 degrees head tilt to the right shoulder the-VD decreased to (D) 2 degrees and (N) 12 degrees. At 45 degrees head tilt to the left shoulder the-VD increased to (D) 18 degrees and (N) 26 degrees. A dissociated vertical deviation was excluded by the dark red glass test and by the reversed fixation test.

CONCLUSION

The disturbance can be explained by a, presumably congenital, supranuclear misinnervation and has to be differentiated from other types of vertical deviation.

[Determining visual acuity with LH symbols and Landolt rings]

PURPOSE

Lea (LH) symbols seem to be favourable for visual acuity assessment in childhood. The symbols of the LH test are well standardized and applicable to preschool children. We compared the visual acuity determined by LH single symbols (LH) and the acuity measured with the Landolt-C (LC).

PATIENTS AND METHODS

138 cooperative subjects aged 7 to 91 years were examined. Their visual acuity was either normal or reduced due to various etiologies. Their refractive error was corrected. The monocular LH and LC were determined by a 3/4 criterion (study 1). In 19 healthy subjects aged 21 to 58 years, acuity was reduced stepwise by 5 different calibrated occlusives (study 2). A Lighthouse single symbol book (LH symbols) was used at a distance of 3 m. LC was determined at a distance of 5 m. The luminance of the test field was 180-200 cd/m2. The right eye of each patient and the amblyopic eye of the squinting patients was taken for statistical evaluation. The strabismic patients' interocular differences of LC and LH were compared.

RESULTS

Within study 1, LC ranged from 0.02 to 2.0 and LH from 0.03 to 2.5. LH overestimated LC by 1.4 lines on an average (t-test p < 0.0001). The regression equation lgLH = 0.95 lgLC + 0.11 describes a high correlation (r = 0.95) between LH and LC. The relations between LH and LC of 43 strabismic amblyopic patients and the remaining subjects did not significantly differ. Due to the criterion of an interocular LH-difference > 1 line, 85.7% resp. 90% of the strabismic amblyopic patients with an interocular LC difference > 1 resp > 2 lines were detected. In study 2, LC ranged from 0.1 to 1.6, LH from 0.12 to 2.0. The mean difference LH-LC was 1.3 lines. The regression equation was lgLH = 0.91 lgLC + 0.08 (r = 0.95).

CONCLUSION

LH symbols allow a reliable measurement of recognition acuity. Due to the design of the symbols, they are excellently suitable for application to preschool children. Age related normal values should be established. The systematic difference between the LC acuity and the LH acuity measured with the Lighthouse LH single symbol book by 1.4 lines has to be considered.

[Causes of blindness in Hessia in 1996]

BACKGROUND

Despite of medical progress, the incidence and prevalence of blindness are continuously increasing. In Hessia, the number of persons receiving blindness compensation payment increased from 8,346 in 1985 to 11,166 in 1996 by 2.6% per year. In 1996, the rate (prevalence) amounted to 1.85/1000 of the Hessian population.

METHODS

In this study, the incidence of blindness (visual acuity < or = 0.02 or equivalent visual handicap) and substantial visual handicap (visual acuity < or = 0.05 or equivalent visual handicap) according to the Hessian law was investigated by means of the records of new candidates for blindness compensation payment whose applications were granted in 1996. The causes of blindness (main diagnosis), visual acuity, age, gender, and nationality were evaluated.

RESULTS

The Hessian administration for public welfare had filed 2,609 alterations of applications concerning sundry social assistance. Out of these, 2,395 files (91.8%) were available, 1411 applications met the requirements for blindness compensation payment, 45.4% were graded substantially visually handicapped for the first time, 43.4% were graded blind for the first time, and 11.0% were graded blind after previous substantial visual handicap. In 0.2%, a further classification was not necessary. Applied to the Hessian population of 6.027 million people, the incidence of blindness was 0.14/1000. 67.9% were female, 30.9% were male, in 1.2% the gender was not evaluable. The age median of the candidates was 78 years (male: 74 years, female: 80 years), 84.3% of the candidates were > or = 60 years old. The most frequent causes of blindness (substantial visual handicap) were: age related macular degeneration 35.3% (49.5%), diabetic retinopathy 15.0% (17.0%), glaucoma 12.6% (7.8%), tapetoretinal degenerations 6.9% (1.7%), optic nerve atrophy 6.1% (4.3%), and myopia 5.0% (6.5%).

CONCLUSION

Age related affections are the most frequent causes of blindness. Due to the increasing life expectancy and rather constant birth rates, a further increase of blindness rates has to be expected.

[Clinical application of a new method for the objective estimation of minimum visual acuity]

PURPOSE

Recently, a new method for the objective estimation of the minimum visual acuity (OEM) by means of suppression of the optokinetic nystagmus has been presented (Klin Monatsbl Augenheilkd 1998;212:196-202). This study reports on the clinical use of this method.

METHODS

In 120 individuals referred to our clinic either to procure an ophthalmological expert opinion or for differential diagnosis of an unclear visual impairment, an OEM was performed. The result of the OEM was compared to the clinical findings (history, biomicroscopy of anterior and posterior segments, objective refractometry, pupillary responses, binocular alignment, motility, binocular vision, colour vision, applanation tonometry, electrophysiology, fluorescein angiography, neurologic, radiologic, psychiatric findings, reproducibility of visual acuity and visual field statements under different conditions, comparison of subjective and objective visual field data, statistical prove of false visual acuity and visual field statements) which were critically interpreted concerning the credibility of the subject's statements.

RESULTS

As a result of the clinical examinations, the stated visual acuity of 62 individuals was credible. In one of these individuals, the OEM pointed to a slightly (1dB) better visual acuity. The statements of 7 individuals could not be categorized clinically. The OEM pointed to a better acuity in 3 cases. The stated vision of the remaining 51 individuals was not credible. In 38 of these cases, the OEM pointed to a better acuity, or false statements could be proven by the OEM.

CONCLUSION

A significant rate (75%) of the individuals whose statements were not credible was detected by the computer-aided, nystagmographic method of OEM. The method allows an estimation of the actual minimum visual acuity and yields evidence of false statements concerning the detection acuity.

Sensitivity of the MTI photoscreener for amblyogenic factors in infancy and early childhood

BACKGROUND

Screening for amblyogenic factors in infancy by pediatricians is unsatisfactory, as they hardly ever detect ametropia or microstrabismus. As photoscreening seems to be a helpful method to detect even small squint angles and refractive errors, we tested the MTI photoscreener for its sensitivity with respect to amblyogenic factors.

PATIENTS AND METHODS

One hundred and twelve children aged 6-48 months were first examined with the MTI photoscreener. Then each child underwent complete medical examination by an ophthalmologist and an orthoptist. The examination included the Hirschberg test (corneal reflex evaluation), the Brückner test (fundus red reflex), and, where possible, the Lang stereotest, the cover test and visual acuity assessment, as well as a motility test, biomicroscopy, ophthalmoscopy in mydriasis and refractometry in cycloplegia. Exclusion criteria were any organic pathological results, manifest strabismus, ametropia > or = 2 D and astigmatism > or = 1 D. An orthoptist, a pediatrician and two ophthalmologists independently evaluated the Polaroid pictures according to the criteria given in the handbook of the MTI photoscreener.

RESULTS

For 10 children the evaluation with the MTI photoscreener was not possible despite the fact that photographs were retaken several times. Thirteen photographs showing obvious pathologic findings despite their poor quality were included. Eighty-three of the remaining 102 children failed the eye examination according to the above-mentioned criteria. The mean sensitivity of the MTI photoscreener was determined to be 82.8%. The ability to correctly identify the absence of any amblyogenic factors (specificity) was 61.8%.

CONCLUSIONS

Sensitivity was high when compared to the usually low detection rate during pediatric examinations. Due to the low specificity, effectiveness was poor. Therefore an ophthalmological examination should be included in the preventive screening during infancy and early childhood.

[Objective assessment of minimum visual acuity by suppression of optokinetic nystagmus]

PURPOSE

To develop and to validate an objective method which allows an estimation of the visual acuity (VA) of adults.

METHODS

A horizontal optokinetic nystagmus (OKN) was elicited by a vertical rectangular grating presented on a PC-screen and was recorded by an infrared reflection method. Superimposition of three stationary black detection stimuli was used to suppress the OKN. The size of these stimuli was increased every two seconds, in ten steps. Suppression of the OKN was taken as an indication that the stimuli were detected. The relation between the smallest effective stimulus and logVA was evaluated in 65 healthy volunteers (130 eyes) with artificially reduced VA and 425 cooperative patients (842 eyes) whose VA was reduced due to different etiologies. The tolerance intervals of logVA related to the discrete detection stimuli were calculated.

RESULTS

The method allows an estimation of the least expectable VA in steps of 0.8, 0.32, 0.25, 0.12, 0.1, 0.06, 0.03 und 0.025 due to the smallest value of three trials. The least VA of strabismic amblyopic eyes can only be estimated in steps of 0.16, 0.06, and 0.02. A VA > 0.02 can be proven with high reliability.

CONCLUSION

The method allows a clinically useful, objective estimation of the least VA without observer bias in non-amblyopic eyes.

[Visual field examination in limited patient cooperation]

Objective methods to estimate the visual field are necessary, if a conventional subjective perimetry is impossible due to limited cooperation. Objective methods are indicated in infants, handicapped patients, patients with psychogenic visual field loss, and malingerers. An objective estimation of the visual field can be performed by means of pupillary light reflexes, voluntary and involuntary eye movements, and visual evoked potentials. Systematically false responses contain useful information regarding the proof of misrepresentations. The reproducibility of visual field defects can be checked by testing at different distances from the screen. This article reports on handy methods requiring no large-scale equipment.

[Examinations with the Cardiff Acuity Test]

Recently, a new preferential looking (PL) test has been presented for measuring visual acuity in infants and young children (Cardiff Acuity Test, CAT). The PL target is a schematic vanishing picture composed of isoluminant lines with different spatial orientations. Fifty-three healthy children (4-34 months, group 1), 28 (4-35 months) children at risk for amblyopia due to strabismus (group 2), 19 healthy subjects, and 157 patients (group 3) were tested with the CAT. In group 2 the CAT was compared with the fixation preference test. In group 3 the CAT was compared with a recognition test (Landolt C test). In group 1 the interocular difference of the CAT data was a maximum of 1 dB (70% 0 dB, 30% 1 dB, 1/3 so-called octave). Thus, an interocular difference of > 1 dB was considered to be suggestive of monocular or asymmetrical visual impairment. The maximum value 6/6 was frequently achieved (RE 44%, LE 36%, > 18 months RE 57%, LE 46%). In group 2 only 20% of the monolateral strabismic children showed an interocular difference > 1 dB in the CAT. In group 3 we found significant correlations between the CAT and Landolt acuity. A ratio of about 1.7/1 between CAT and Landolt acuity remained constant in cataract eyes as compared to healthy eyes. In amblyopic eyes due to strabismus this ratio was 3.7/1. Thus, amblyopia was underestimated with the CAT. Without limiting the examination distance, interocular differences > 1 dB in the CAT occurred in 52% of the strabismic amblyopic patients (potential sensitivity). At a distance of 1 m this rate decreased to 22% (real sensitivity). In conclusion, the CAT definitely lacks sensitivity for strabismic amblyopia. The data suggest that the real sensitivity could be improved by using higher spatial frequencies. The use of familiar shapes instead of gratings such as PL targets affects cooperation favorably in 12- to 36-month-old children.

[Bilateral congenital mydriasis with accommodation failure]

In the literature congenital mydriasis is described as a very rare condition and explained as a result of isolated aplasia of the iris sphincter muscle. Aplasia of the ciliary muscle was assumed to cause congenital accommodation insufficiency. A case of congenital mydriasis with lack of accommodation is presented. The first ophthalmological check-up was 2 weeks after surgery for a persistent ductus arteriosus Botalli. The girl was 15 weeks old. Her parents had watched her dilated pupils since birth. The diameter of both pupils was 6.5 mm. They did not react to light, lid closure, or conjunctival administration of pilocarpine solutions up to 1%. A refractive error of OD +3.0 D and OS +2.5 D was measured by retinoscopy. The hypermetropia was also uninfluenced by topical locarpine 1%. Two drops of pheylephrine 2.5% caused additional pupillary dilatation of 0.5 mm. Besides the lack of accommodation and pupillary constriction, all ocular findings were regular. No chromosomal abnormalities were found. No further cases of pupillary disorders are known in the family. These findings can only result from the lack of cholinergic sensitivity or aplasia of the pupillary sphincter and ciliary muscle. The infant was supplied with bifocals and sunglasses. The near correction was spontaneous. At the age of 15 months there was a grating acuity of 20/80, which is in the normal range, as measured by preferential looking.