Variable expression of albinism within a single kindred

The effects of topical carbonic anhydrase inhibitor in treatment of nystagmus

OBJECTIVE

To evaluate the effects of topical carbonic anhydrase inhibitor (CAI), brinzolamide (Azopt), for treatment of nystagmus patients.

MATERIALS AND METHODS

Patients who used Brinzolamide for treatment of nystagmus were retrospectively analyzed. 23 patients were included in this study. The patients' diagnosis were idiopathic infantile nystagmus 18 (78.2%) and oculocutaneous albinism in 5 (21.8%). Azopt eye drop was used in both eyes, 3 times a day. Detailed eye examination in all of the patients before treatment and repeated at the end of the first week after treatment. SPSS 16.0 computer program was used for evaluation of DATAs.

RESULTS

The mean follow-up was 32 ± 28 months. 23 patients 15 (65.2%) were male and 8 (34.7%) were female and the mean age was 12.6 ± 5.5. Before the management of topical brinzolamide, abnormal head position (AHP) were observed in 18 patients. After that we found reduction of nystagmus in 5 (22.7%) of the patients, increase in vision in 9 (40.9%) and reduced AHP in 18.3%. There is no identified change in 4 (18.1%).

CONCLUSION

The medical treatment of nystagmus with topical brinzolamide was found effective in our series but, wider series and longer follow-up studies are needed.

Concordance of visual and structural features between siblings with albinism

PURPOSE

To evaluate similarities and differences in visual function and ocular structure between siblings with albinism.

METHODS

The medical records of all siblings diagnosed with albinism were retrospectively reviewed. Comparisons were made using examination at oldest age for younger sibling and examination closest to that age for older siblings.

RESULTS

A total of 111 patients from 54 families were studied. Mean age was 12.9 years (range, 2 months to 44.2 years). Mean difference in ages between sibling pair examinations was 11.5 months (range, 0-87 months). Of 45 families, best-corrected visual acuity was equal in 9 (20%), within 1/2 octave in 9 (20%), >1/2 but <1 octave in 21 (47%), and ≥1 octave difference in 6 (13%). Of 27 families, stereoacuity was present in all siblings in 9 (33%), absent in 9 (33%), and present in only 1 sibling in 9 (33%). Of 54 families, grading of iris translucency was equal in 35 (65%) and different by 1 grade in 19 (35%). Of 54 families, foveal grading was equal in 39 (72%), different by 1 grade in 14 (26%), and different by ≥2 grades in 1 (2%). Macular melanin was present in all siblings in 16 of the 54 families (30%), absent in all siblings in 36 (67%), and present in only 1 sibling in 2 (4%) families.

CONCLUSIONS

The strong concordance of structural features is contrasted with discordance in visual function. Families of siblings with albinism should be counseled with due caution because visual function is often disparate despite similar structural findings.

Comparison of clinical findings in pediatric patients with albinism and different amplitudes of nystagmus

INTRODUCTION

Visual acuity in albinism can vary and is difficult to predict. We undertook this study to investigate whether patients with albinism with absent or minimal nystagmus have better visual acuity and ocular alignment than patients with albinism and obvious nystagmus.

METHODS

Our retrospective chart review of 38 pediatric patients with albinism yielded 16 patients with absent or minimal nystagmus and 22 patients with obvious nystagmus.

RESULTS

Patients with albinism and absent or minimal nystagmus had best-corrected visual acuities ranging from 20/20 to 20/50, with a mean visual acuity of 20/33. Those patients with albinism and obvious nystagmus had best-corrected visual acuities ranging from 20/30 to 20/200, with a mean visual acuity of 20/80. Visual acuity was significantly better in the group with absent or minimal nystagmus (P < 0.001). Of the 16 patients with absent or minimal nystagmus, 6 were orthophoric and 10 had a strabismic deviation of 12 prism diopters (PD) or less. None of these patients required strabismus surgery. Of the 22 patients with nystagmus, 16 were orthophoric, 1 had a horizontal deviation of less than 12 PD, and 5 had larger angle horizontal deviations ranging from 20 to 50 PD.

CONCLUSION

Our findings suggest that pediatric albinism patients with absent or minimal nystagmus can be expected to demonstrate better visual acuity and are less likely to show a strabismic deviation of greater than 12 PD compared with those with obvious nystagmus (P = 0.0003).

Stereopsis in patients with albinism: clinical correlates

PURPOSE

A hallmark of albinism is excessive decussation of retinostriate projections at the optic chiasm. This misprojection might lead to abnormalities in the retinal correspondence and may account for the usual absence of stereovision. We report on 2 groups of patients with albinism who have either fine or gross stereopsis and compare the clinical findings of these groups to other patients with albinism with similar visual acuities but no stereopsis.

METHODS

A retrospective chart review of patients with albinism was used to segregate those with a letter visual acuity of 20/100 or better in one eye, assessment of stereopsis, and strabismus < or = 10 PD. Forty-five patients were identified. Albinism type, best-corrected visual acuity, motility, Titmus vectograph stereoacuity, iris and macula transparency grades, and the presence or absence of both melanin and an annular reflex in the macula were tabulated. A comparison of the clinical characteristics of the groups with and without stereopsis was made.

RESULTS

Those albino subjects who demonstrated stereopsis had better visual acuity, less iris transillumination, more frequent presence of melanin in the macula, less nystagmus, and less marked foveal hypoplasia than the albino subjects without stereopsis. No nystagmus was clinically detected in 5 patients with fine stereopsis. All these differences were statistically significant. Macular transparency grade was not significantly different between the groups.

CONCLUSIONS

Patients with albinism who demonstrate stereopsis tend to have better visual acuity, more iris pigment, and more melanin pigment in the macula than their counterparts without stereopsis.

Correlation of visual acuity and ocular pigmentation with the 16-bp duplication in the HPS-1 gene of Hermansky-Pudlak syndrome, a form of albinism

OBJECTIVE

Patients with the Hermansky-Pudlak syndrome (HPS), a form of albinism, were studied. The first purpose of this investigation was to determine if visual acuity was related to the presence or absence of the 16-bp duplication in the HPS-1 gene. The second was to study the correlation between the degree of ocular pigmentation and visual acuity within the two genetic groups described above.

DESIGN

Cross-sectional study of a series of consecutive patients.

PARTICIPANTS

Forty-nine patients with HPS with or without the 16-bp duplication in HPS-1.

METHODS

Best corrected visual acuity (VA) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, photographic gradings of iris transillumination and of visibility of choroidal vessels in the macula (macular transparency).

MAIN OUTCOME MEASURES

Association between VA and the presence or absence of the 16-bp duplication in HPS-1 and correlation between VA and the degree of iris transillumination (iris score) and macular transparency (fundus score), as determined by masked reading of photographs, with respect to the presence or absence of the 16-bp duplication in HPS-1 were the main outcome measures.

RESULTS

The VA of the better eye did not differ between the two genetic groups (P = 0.322, two-sided t test). Spearman's rank correlation between VA and iris scores in 39 eyes of 20 patients with the duplication was not statistically significant (P = 0.698) but was statistically significant in 36 eyes of 19 patients without the duplication (P < 0.001). Among all patients, the correlation was statistically significant (r = -0.36 in RE and r = -0.51 in LE). Spearman's rank correlation between VA and fundus scores in 36 eyes of 19 patients with and 34 eyes in 18 patients with and without the duplication was statistically significant (P = 0.035 and P = 0.008, respectively). Among all patients, it was also statistically significant (r = -0.39 in RE and r = -0.45 in LE).

CONCLUSIONS

The mean VA of the better eye did not differ in patients with the 16-bp duplication compared with those without the duplication. There were statistically significant associations between VA and the iris score and the fundus score except for the VA and iris scores in patients with the 16-bp duplication. However, because of the variability of VA, these associations were not large enough for useful prediction of VA based on the degree of ocular pigmentation.

Diagnosis of oculocutaneous albinism with molecular analysis

PURPOSE

To use molecular analysis to diagnose oculocutaneous albinism in a patient with an atypical clinical presentation.

METHODS

A 34-year-old woman with a history of strabismus and absent cutaneous pigment underwent comprehensive ophthalmic examination, visual-evoked potentials to detect altered optic decussation, and molecular analysis.

RESULTS

Examination showed fine nystagmus, iris transillumination, foveal hypoplasia, and corrected visual acuity of 20/25 in each eye. Misrouting of the retinostriate fibers was demonstrated with visual-evoked potentials. Mutations in the tyrosinase gene established the diagnosis of oculocutaneous albinism 1 even though the patient had atypical clinical features.

CONCLUSIONS

Molecular analysis can establish the diagnosis of oculocutaneous albinism 1 in the patient with atypical ocular features.

A practical approach to albino diagnosis. VEP misrouting across the age span

In addition to the genetic heterogeneity in albinism, widespread clinical heterogeneity frequently impedes albino detection and differential diagnosis. Further, several auxiliary ocular and/or cutaneous manifestations of this inherited error of pigmentary metabolism are neither pre-requisite nor specific to the albino condition. However, one feature that is specific to albinism regardless of genotype or phenotype is a unique pattern of abnormal visual pathway organization. With an appropriate test paradigm, the albino visual pathway can be revealed by the non-invasive recording of the visual evoked potential (VEP) distribution across the occiput which shows contralateral hemispheric asymmetry following full field monocular stimulation. As described in this report, the VEP albino misrouting detection test has been refined to yield extraordinarily high sensitivity and selectivity across the age span from the neonate to the elderly. As the VEP profile undergoes maturational changes, these changes have been taken into account in the development of an albino age-range VEP test recipe which includes the pattern onset paradigm for older albinos and a luminance flash paradigm for the albino infant. The age appropriate optic pathway misrouting test provides reliable albino detection and definitive differential diagnosis. Further, as the albino VEP signature of contralateral asymmetry is also age specific, the VEP misrouting test can be extended to the objective assessment of visual pathway maturation.