Journal of Pediatric Ophthalmology and Strabismus

CME Activity 

CME Activity

Abstract

Review the stated learning objectives on the first page of the CME article and determine if these objectives match your individual learning needs.

Read the article carefully. Do not neglect the tables and other illustrative materials, as they have been selected to enhance your knowledge and understanding.

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Send the completed form to: JOURNAL OF PEDIATRIC OPHTHALMOLOGY & STRABISMUS CME Quiz, PO Box 36, Thorofare, NJ 08086.

Be sure to mail the CME Registration Form on or before the deadline listed. After that date, the quiz will close. CME Registration Forms received after the date listed will not be processed.

Your answers will be graded and you will receive a certificate via mail within 4 to 6 weeks advising you whether you have passed or failed. A score of at least 80% is required to pass. Unanswered questions will be considered incorrect.

This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint sponsorship of Vindico Medical Education and the Journal of Pediatric Ophthalmology & Strabismus. Vindico Medical Education is accredited by the ACCME to provide continuing medical education for physicians.

Vindico Medical Education designates this journal-based educational activity for a maximum of 1 AMA PRA Category 1 Credit™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

This activity is approved for credit from the original date of release, March 1, 2012, through the expiration date of March 15, 2013.

In accordance with the Accreditation Council for Continuing Medical Education’s Standards for Commercial Support, all CME providers are required to disclose to the activity audience the relevant financial relationships of the planners, teachers, and authors involved in the development of CME content. An individual has a relevant financial relationship if he or she has a financial relationship in any amount occurring in the last 12 months with a commercial interest whose products or services are discussed in the CME activity content over which the individual has control. Relationship information appears prior to the content.

The audience is advised that this continuing medical education activity may contain references to unlabeled uses of FDA-approved products or to products not approved by the FDA for use in the United States. The faculty members have been made aware of their obligation to disclose such usage.

This CME activity is primarily targeted to pediatric ophthalmologists and ophthalmic surgeons. There are no specific background requirements for participants taking this activity.

To understand how vision will change over time in albinism to answer questions from parents.

To recognize that best-corrected visual acuity often improves over the early school years in students with albinism.

Albinism is a genetic disorder in which melanin…

How to Obtain Credit by Reading This Article

  1. Review the stated learning objectives on the first page of the CME article and determine if these objectives match your individual learning needs.

  2. Read the article carefully. Do not neglect the tables and other illustrative materials, as they have been selected to enhance your knowledge and understanding.

  3. The following quiz questions have been designed to provide a useful link between the CME article in the issue and your everyday practice. Read each question, choose the correct answer, and record your answer on the CME REGISTRATION FORM at the end of the quiz.

  4. Type or print your full name and address and your date of birth in the space provided on the CME REGISTRATION FORM.

  5. Complete the Evaluation portion of the CME Registration Form. Forms and quizzes cannot be processed if the Evaluation portion is incomplete. The Evaluation portion of the CME Registration Form will be separated from the quiz upon receipt at JOURNAL OF PEDIATRIC OPHTHALMOLOGY & STRABISMUS. Your evaluation of this activity will in no way affect the scoring of your quiz. NO PAYMENT REQUIRED. You may be contacted at a future date with a follow-up survey to this activity.

  6. Send the completed form to: JOURNAL OF PEDIATRIC OPHTHALMOLOGY & STRABISMUS CME Quiz, PO Box 36, Thorofare, NJ 08086.

  7. Be sure to mail the CME Registration Form on or before the deadline listed. After that date, the quiz will close. CME Registration Forms received after the date listed will not be processed.

Method for Obtaining Credit Certificate

Your answers will be graded and you will receive a certificate via mail within 4 to 6 weeks advising you whether you have passed or failed. A score of at least 80% is required to pass. Unanswered questions will be considered incorrect.

CME Accreditation

This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint sponsorship of Vindico Medical Education and the Journal of Pediatric Ophthalmology & Strabismus. Vindico Medical Education is accredited by the ACCME to provide continuing medical education for physicians.

Vindico Medical Education designates this journal-based educational activity for a maximum of 1 AMA PRA Category 1 Credit™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

This activity is approved for credit from the original date of release, March 1, 2012, through the expiration date of March 15, 2013.

Full Disclosure Policy

In accordance with the Accreditation Council for Continuing Medical Education’s Standards for Commercial Support, all CME providers are required to disclose to the activity audience the relevant financial relationships of the planners, teachers, and authors involved in the development of CME content. An individual has a relevant financial relationship if he or she has a financial relationship in any amount occurring in the last 12 months with a commercial interest whose products or services are discussed in the CME activity content over which the individual has control. Relationship information appears prior to the content.

Unlabeled and Investigational Usage

The audience is advised that this continuing medical education activity may contain references to unlabeled uses of FDA-approved products or to products not approved by the FDA for use in the United States. The faculty members have been made aware of their obligation to disclose such usage.

Target Audience

This CME activity is primarily targeted to pediatric ophthalmologists and ophthalmic surgeons. There are no specific background requirements for participants taking this activity.

Change in Visual Acuity in Albinism in the Early School Years

Educational Objectives

  1. To understand how vision will change over time in albinism to answer questions from parents.

  2. To recognize that best-corrected visual acuity often improves over the early school years in students with albinism.

Introduction

Albinism is a genetic disorder in which melanin pigment is reduced or absent in the eyes and often in the hair and skin. It occurs in the United States with a frequency of approximately 1 in 20,000.1 It is classified as oculocutaneous albinism (OCA) or ocular albinism, depending on the clinical phenotype, amount of melanin pigment present, and the gene mutation. OCA is more common than ocular albinism and encompasses several different types based on the responsible gene. There are also unusual forms of OCA associated with systemic conditions, such as Hermansky–Pudlak syndrome and Chediak–Higashi syndrome.

The degree of hypopigmentation varies considerably in albinism, from little or no pigment to nearly normal pigment in some individuals. Visual acuity is variably reduced in albinism and is generally related to the type of albinism and severity of hypopigmentation.2 OCA1 is due to a mutation in the tyrosinase gene on chromosome 11q. Those without ability to produce any melanin (OCA1A) typically have visual acuity ranging from 20/100 to 20/400, whereas those who can make some pigment due to residual enzyme function (OCA1B) often have better vision.3 Individuals with OCA2 have abnormal synthesis or function of a transmembrane protein essential for melanogenesis and typically have better vision than individuals with tyrosinase-related albinism. OCA2 is produced by mutations in the P gene on chromosome 15q. Vision in ocular albinism, inherited as an X-linked recessive disorder, is often better than that seen in OCA.4

Isolated cases of improved vision in individuals with albinism have been reported, but the frequency and amount of improvement are unknown.5,6 We sought to determine whether binocular best-corrected visual acuity (B-BCVA) improved during the early school years and whether this was related to type of albinism, ocular pigment, or appearance of the macula.

Patients and Methods

After obtaining approval from the Institutional Review Board at the University of Minnesota, we performed a retrospective chart review of individuals with albinism seen between 1984 and 2010. Prior consent to use examination data had been obtained from the patients’ parents or guardians.

A diagnosis of albinism was primarily based on determination of clinical phenotype by a pediatric ophthalmologist (CGS) and geneticist (RAK). A diagnosis of OCA1 was made when individuals with typical features of albinism had white hair and skin and blue irides at birth. When no pigment developed, individuals were diagnosed as having OCA1A. When melanin pigment developed in the skin, hair, and/or eyes, a diagnosis of OCA1B was made. Individuals born with melanin pigment in the hair were classified as having OCA2. A diagnosis of Hermansky–Pudlak syndrome was made in those with OCA and an abnormality of platelet function due to absence of dense bodies. Those with OCA and increased susceptibility to infections associated with giant granules in melanocytes were diagnosed as having Chediak–Higashi syndrome. A diagnosis of OA1 was given for males with the ocular features of albinism but with normal skin and hair pigment, often accompanied by finding pigmentary mosaicism in the biological mother (obligate carrier). In some cases without a definitive clinical examination, additional testing included a visual evoked potential to document excessive retinostriate decussation, an electroretinogram to eliminate other diagnoses, and testing for mutations on genes known to cause albinism.

We included all patients with binocular B-BCVA measured at two ages: 5.5 to 9 years (Visit A) and 9.5 to 14 years (Visit B), provided the time between the two visits was at least 2.5 years for each patient. These age windows were selected to capture the largest number of patients in this retrospective study, whereas the minimum time between visits was arbitrarily selected to provide a time period that might allow for detection of a change in visual acuity. We excluded patients who had undergone extraocular muscle surgery for nystagmus between Visits A and B, patients with a normal visual evoked potential, and patients with an abnormal electroretinogram.

We recorded type of albinism, glasses prescription, manifest refraction, refraction with refinement (after administration of a proprietary mixture of 1.3% cyclopentolate, 1.6% phenylephrine, and 0.16% tropicamide), iris grade, macular grade, presence or absence of melanin in the macula, and presence or absence of a rudimentary annular reflex in the macula. Glasses were prescribed according to guidelines described by Anderson et al.7 For analysis of improvement in visual acuity, we used the refraction that gave the best B-BCVA. Preferred head posture was allowed for binocular acuity testing with projected linear letters (Snellen acuity) by an experienced, unmasked examiner in a well-illuminated environment. The smallest line on which at least half of the letters were correctly identified was recorded as the B-BCVA.

All ocular characteristics were evaluated by the same individual (CGS) who was not masked to diagnosis, but the standard procedure employed in examining patients with albinism included voluntarily masking to examination findings at the previous visits. Iris grade was determined with slit-lamp biomicroscopy according to a previously described scale of iris pigmentation.8 Grade 1 represented marked pigment in the posterior iris epithelium and punctate area of iris transillumination, grades 2 and 3 represented moderate and minimal pigment, respectively, and grade 4 represented no pigment and full iris transillumination. Macular melanin pigment was graded as present or absent by inspection with direct ophthalmoscopy. Macular transparency, also determined by inspection with direct ophthalmoscopy, was graded according to the previously published scheme: grade 1 = easily visualized choroidal vessels, grade 2 = vessels less easily seen due to some masking, and grade 3 = complete masking of the choroidal vessels in the macula.8 Presence or absence of a rudimentary annular reflex in the macula was detected by binocular indirect ophthalmoscopy.

Change in recognition acuity at the two ages was compared to type of albinism and the noted ocular characteristics. Secondary analysis was performed to compare B-BCVA at each visit to the studied variables. Two subgroups were also compared: OCA1B (22 patients) and OCA2 (22 patients). All other subgroups based on type of albinism contained too few patients to allow for comparison. Analyses performed included paired and unpaired t tests for comparing B-BCVA at Visits A and B and linear regressions for all correlations. P values less than .05 were considered significant. Visual acuity was converted to logarithm of the minimum angle of resolution acuity and differences were compared in terms of octaves.

Results

We identified 65 patients (35 male, 30 female) with a diagnosis of albinism who had visual acuity measured at two ages: 5.5 to 9 years (Visit A) and 9.5 to 14 years (Visit B). Twelve patients had OCA1A, 22 patients had OCA1B, 22 patients had OCA2, 7 patients had ocular albinism, 1 patient had Hermansky–Pudlak syndrome, and 1 patient had Chediak–Higashi syndrome. To facilitate diagnosis, 13 patients had an abnormal visual evoked potential, which showed excessive retinostriate decussation, 3 patients had a normal electroretinogram, and 3 patients were found to have a mutation on a gene known to cause albinism. Mean ages at Visits A and B were 6.9 and 11.8 years, respectively, with an age difference between these two visits ranging from 2.5 to 7.67 years. At Visit A, 53 of the subjects wore glasses. By Visit B, this number had increased to 56 subjects.

B-BCVA for the study group showed significant improvement from a mean of 20/84 at Visit A to a mean of 20/61 at Visit B (P < .001). When grouped by type of albinism, only the OCA1B and OCA2 subgroups were large enough to analyze separately. Improvement in B-BCVA was also found in these two subgroups of albinism over the time period studied: from 20/68 to 20/51 for OCA1B (P < .001) and from 20/79 to 20/63 for OCA2 (P = .039).

B-BCVA for 52 of the 65 subjects (80%) improved from Visit A to Visit B. Improvement was evaluated in terms of octaves. An octave is commonly thought of as a halving or doubling of the Snellen denominator (eg, 20/60 to 20/30 is an octave). Because B-BCVA was converted into logarithm of the minimum angle of resolution for statistical evaluation of data, more specifically, an octave is a change of 0.3 log units; when converted back to a Snellen fraction, it represents a change from 20/63 to 20/32. Visual acuity in 21 subjects improved less than 0.5 octave, 21 subjects improved 0.5 or greater but less than 1.0 octave, and 10 subjects improved 1.0 octave or greater (Figure). No child had worse B-BCVA at Visit B compared to Visit A. Of the 10 patients improving 1.0 octave or greater, 3 patients had OCA1B, 3 patients had OCA2, 3 patients had OCA1A, and 1 patient had ocular albinism. No improvement in vision was found in 13 patients. Of the 13 patients who did not improve, 5 patients had a diagnosis of OCA1B, 5 patients had OCA2, 2 patients had ocular albinism, and 1 patient had OCA1A.

Correlations between glasses wear, iris grade, macular grade, the presence of melanin pigment in the macula, and annular reflex with improvement in B-BCVA for the entire study group were weak (Table 1). These variables were also correlated with measured B-BCVA at each visit and showed a moderate correlation for iris grade and macular melanin at both Visits A and B (Table 2). Similar correlations were made for the two subgroups (Table 3). Moderate correlations of B-BCVA with all variables except glasses wear were found at Visit A but only macular grade and macular melanin moderately correlated for the group with OCA1B at Visit B. For the group with OCA2, only iris and macular grades were moderately correlated with B-BCVA at Visit B.

Discussion

Visual acuity in individuals with albinism typically ranges from 20/100 to 20/200 but can vary from 20/20 to 20/400.9–11 The reduced vision that individuals with albinism typically exhibit is one of the most disabling features of the disorder.11 In the pediatric population, reduced vision plays an important role in a child’s learning and educational planning. Vision in the general population develops rapidly during the first 6 months of life and then progresses at a slower rate to a nearly adult level by the age of 3 years when measured with acuity cards.12 In previously published reports, it has been suggested that the rate of visual development may be delayed in children with albinism.13–15 Hypotheses to explain delayed visual maturation include an arrest in development at a certain point in maturation or a delay from birth with progression at a slower rate than that observed in the general population. A study comparing grating acuity in the first 3 years of life in a large group of children with albinism to normative data concluded that albinism is associated with abnormal visual maturation, in addition to reduced visual potential.16 In contrast, a case study of a patient with OCA1 found that acuity was similar to that of normal infants up to the age of 14 months and then decreased.17 The results of our study suggest that visual maturation may continue through the early school years.

We examined visual acuity in children at 5.5 to 9 years and 9.5 to 14 years to determine whether improvement occurred during the early school years. We chose these two age ranges because they represent both ends of the spectrum of elementary education. We arbitrarily set 2.5 years as the minimum difference in age between Visits A and B. We also examined the various characteristics associated with albinism and their relationship to change in visual acuity. In our total study population of 65 patients, we found significant improvement in vision (from a mean of 20/84 to a mean of 20/59) between these two defined ages. That improvement remained significant for OCA1B and OCA2 when subgroup analyses were performed. Possible reasons for improvement in B-BCVA include continued maturation of the visual system, changes in characteristics of nystagmus over time, use of a head posture to damp nystagmus, improved compliance with wearing glasses, and/or changes in ocular pigment. It is unlikely that the observed change in B-BCVA was due to increased cooperation with vision testing because most children ages 5.5 to 9 years are sufficiently mature to follow instructions and complete the testing without loss of attention.

Subgroup analysis in this study showed better B-BCVA in OCA1B than OCA2. The former group included only those patients with OCA1 who had clinical evidence of melanin production, and therefore represents a subgroup of tyrosinase-negative albinism. Witkop et al. has suggested that visual potential is related, in part, to the amount of ocular pigment present.18 A previous study involving both children and adults concluded that the presence of melanin pigment in the macula is an important indicator of visual potential.11 In our study, we found a moderately positive correlation between presence of both iris grade and macular melanin pigment and measured visual acuity at each of the two study visits. The data suggest that ocular melanin pigment, particularly in the macula, is related to a relatively better level of measured visual acuity for OCA1B, but such could not be shown to be related to improvement in B-BCVA. This is most likely due to the small changes in B-BCVA over the studied interval.

Previous studies have indicated improvement in vision as a child matures to adulthood, but have not examined correlation of B-BCVA with specific characteristics of albinism. Blohmé and Tornqvist conducted a 19-year follow-up study that included a cohort of 9 patients with albinism.4 Five of the 9 patients had sufficient improvement in vision over the course of the study to qualify for exclusion from the researchers’ low vision category (visual acuity: 20/67 to 20/400). Summers and King studied another cohort of 9 individuals with minimal pigment albinism (OCA1B with development of small amounts of hair and iris pigment over the first two decades of life) and noted improvement in monocular vision by 2.0 octaves over 8 years in one patient.5 The current study showed improvement in binocular B-BCVA in a larger number of patients in the early school years.

A limitation of this retrospective study was the number of subjects who had vision measured within the two defined age ranges. When further divided into type of albinism, only the OCA1B and OCA2 groups contained enough subjects to permit subgroup analysis. Another limitation is the variable time interval between Visits A and B, which ranged from 2.50 to 7.67 years. The smaller interval would likely have mitigated against detection of a change in visual acuity, and thus the measured improvement likely underestimates the true improvement that occurs in the early school years.

In this study of 65 children with albinism, visual acuity improved in 80% over the early school years, although improvement for an individual child was often modest. A strong correlation between change in visual acuity and type of albinism or any of the studied ocular parameters was not found. Moderate correlations between measured B-BCVA and iris grade and macular melanin were found at Visits A and B, suggesting that ocular melanin pigment is related to relatively better visual acuity, regardless of the age of the child. Counseling parents and children with albinism should include the possibility of improved vision during the early school years and the likelihood of relatively better vision when melanin pigment is detected in the eyes.

References

  1. King, RA, Hearing, VJ, Creel, DJ & Oetting, WS. Albinism. In: Scrivner CR, Beaudet AL, Sly WS, Valle D, eds. Metabolic and Molecular Basis of Inherited Disease, 8th ed., vol. IV. New York: McGraw-Hill; 2001:5587–5627.
  2. Kinnear, PE, Jay, B & Witkop, CJ Jr. . Albinism. Surv Ophthalmol. 1985;30:75–101. doi:10.1016/0039-6257(85)90077-3 [CrossRef]
  3. Fonda, G, Thomas, H & Gore, GV 3rd. . Educational and vocational placement, and low-vision corrections in albinism: a report based on 253 patients. Sight Sav Rev. 1971;41:29–36.
  4. Blohmé, J & Tornqvist, K. Visually impaired Swedish children: the 1980 cohort study—a 19-year ophthalmological follow-up. Acta Ophthalmol Scand. 2000;78:553–559. doi:10.1034/j.1600-0420.2000.078005553.x [CrossRef]
  5. Summers, CG & King, RA. Ophthalmic features of minimal pigment oculocutaneous albinism. Ophthalmology. 1994;101:906–914.
  6. Oetting, WS. Albinism. Curr Opin Pediatr. 1999;11:565–571. doi:10.1097/00008480-199912000-00016 [CrossRef]
  7. Anderson, J, Lavoie, J, Merrill, K, King, RA & Summers, CG. Efficacy of spectacles in persons with albinism. J AAPOS. 2004;8:515–520. doi:10.1016/j.jaapos.2004.08.008 [CrossRef]
  8. Summers, CG, Knobloch, WH, Witkop, CJ Jr. & King, RA. Hermansky-Pudlak syndrome: ophthalmic findings. Ophthalmology. 1988;95:545–554.
  9. Cheong, PY, King, RA & Bateman, JB. Oculocutaneous albinism: variable expressivity of nystagmus in a sibship. J Pediatr Ophthalmol Strabismus. 1992;29:185–188.
  10. Summers, CG, Creel, D, Townsend, D & King, RA. Variable expression of vision in sibs with albinism. Am J Med Genet. 1991;40:327–331. doi:10.1002/ajmg.1320400316 [CrossRef]
  11. Summers, CG. Vision in albinism. Trans Am Ophthalmol Soc. 1996;94:1095–1155.
  12. Salomão, SR & Ventura, DF. Large sample population age norms for visual acuities obtained with Vistech-Teller acuity cards. Invest Ophthalmol Vis Sci. 1995;36:657–670.
  13. Tresidder, J, Fielder, AR & Nicholson, J. Delayed visual maturation: ophthalmic and neurodevelopmental aspects. Dev Med Child Neurol. 1990;32:872–881. doi:10.1111/j.1469-8749.1990.tb08099.x [CrossRef]
  14. Fielder, AR, Russell-Eggitt, IR, Dodd, KL & Mellor, DH. Delayed visual maturation. Trans Ophthalmol Soc U K. 1985;104:653–661.
  15. Birch, E, Hale, L, Stager, D, Fuller, D & Birch, D. Operant acuity of toddlers and developmentally delayed children with low vision. J Pediatr Ophthalmol Strabismus. 1987;24:64–69.
  16. Whang, SJ, King, RA & Summers, CG. Grating acuity in albinism in the first three years of life. J AAPOS. 2002;6:393–396. doi:10.1067/mpa.2002.129047 [CrossRef]
  17. Jacobson, SG, Mohindra, I, Held, R, Dryja, TP & Albert, DM. Visual acuity development in tyrosinase negative oculocutaneous albinism. Doc Ophthalmol. 1984;56:337–344. doi:10.1007/BF00155678 [CrossRef]
  18. Witkop, CJ Jr. , Hill, CW & Desnick, S et al. Ophthalmologic, biochemical, platelet, and ultrastructural defects in the various types of oculocutaneous albinism. J Invest Dermatol. 1973;60:443–456. doi:10.1111/1523-1747.ep12702920 [CrossRef]

Correlation of Improvement in B-BCVA With Ocular Characteristics of Albinism

Characteristic All Patients (N = 65)
OCA1B (n = 22)
OCA2 (n = 22)
P R P R P R
Glasses wear < .001 0.084 .000 0.229 < .001 0.148
Iris grade < .001 0.075 .000 0.250 < .001 0.032
Macular grade < .001 0.120 .000 0.056 < .001 0.229
Macular melanin < .001 0.067 .000 0.265 .003 0.208
Annular reflex < .001 0.036 .001 0.245 .112 0.015

Correlation of Measured B-BCVA at Visits A and B With Ocular Characteristics of Albinism for All Patients (N = 65)a

Characteristic Visit A
Visit B
P R P R
Glasses wear < .001 0.066 < .001 0.312
Iris grade < .001 0.485 < .001 0.467
Macular grade < .001 0.044 < .001 0.116
Macular melanin .097 0.436 .950 0.482
Annular reflex .003 0.259 .131 0.259

Correlation of Measured B-BCVA at Visits A and B With Ocular Characteristics for Patientsa

Characteristic Visit A
Visit B
P R P R
OCA1B (n = 22)
  Glasses wear .001 0.041 < .001 0.299
  Iris grade < .001 0.479 < .001 0.253
  Macular grade < .001 0.385 < .001 0.388
  Macular melanin .295 0.654 .051 0.452
  Annular reflex .944 0.396 .172 0.226
OCA1B (n = 22)
  Glasses wear .754 0.125 .002 0.123
  Iris grade .002 0.144 < .001 0.316
  Macular grade < .001 0.162 < .001 0.332
  Macular melanin .263 0.068 .725 0.295
  Annular reflex .042 0.074 .038 0.095

CME Quiz: Change in Visual Acuity in Albinism in the Early School Years

Case Scenario

Parents bring a 6-year-old girl with nystagmus to the office to determine whether glasses would help her vision and to find out what her visual prognosis is. The examination shows reduced vision, iris transillumination, and foveal hypoplasia.

CME Questions

  1. What is the most likely diagnosis?

    1. Achromatopsia.

    2. Albinism.

    3. Aniridia.

    4. Batten’s disease.

  2. What is the natural progression of visual acuity in this condition?

    1. Blindness by age 10 years.

    2. Slow deterioration over several decades.

    3. Likely some improvement over early school years.

    4. Resolution of nystagmus and improvement of best-corrected visual acuity to 20/20.

  3. Which of the following shows a strong correlation with change in best-corrected visual acuity?

    1. Amount of iris transillumination.

    2. Amplitude of nystagmus.

    3. Visible choroidal vessels in macula.

    4. Melanin pigment in the macular retinal pigment epithelium.

  4. All of the following are true of this disorder EXCEPT:

    1. Children will not wear glasses because they have no improvement in visual acuity with correction.

    2. Children are often photosensitive.

    3. The phenotype is variable.

    4. An autosomal recessive inheritance pattern is more common than X-linked inheritance.

10.3928/01913913-20120308-02

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