Ann M. Holleschau

The Infant Aphakia Treatment Study: Design and Clinical Measures at Enrollment

OBJECTIVE To compare the use of contact lenses and intraocular lenses (IOLs) for the optical correction of unilateral aphakia during infancy. METHODS In a randomized, multicenter (12 sites) clinical trial, 114 infants with unilateral congenital cataracts were assigned to undergo cataract surgery with or without IOL implantation. Children randomized to IOL treatment had their residual refractive error corrected with spectacles. Children randomized to no IOL treatment had their aphakia treated with a contact lens. MAIN OUTCOME MEASURES Grating acuity at 12 months of age and HOTV visual acuity at 4 1/2 years of age. APPLICATION TO CLINICAL PRACTICE This study should determine whether either treatment for an infant with a visually significant unilateral congenital cataract results in a better visual outcome. RESULTS Enrollment began December 23, 2004, and was completed January 16, 2009. The median age at the time of cataract surgery was 1.8 months. Fifty patients were 4 to 6 weeks of age at the time of enrollment; 32, 7 weeks to 3 months of age; and the remaining 32, more than 3 to less than 7 months of age. Fifty-seven children were randomized to each treatment group. Eyes with cataracts had shorter axial lengths and steeper corneas on average than the fellow eyes. CONCLUSIONS The optimal optical treatment of aphakia in infants is unknown. However, the Infant Aphakia Treatment Study was designed to provide empirical evidence of whether optical treatment with an IOL or a contact lens after unilateral cataract surgery during infancy is associated with a better visual outcome.

Further refinement of the MYP2 locus for autosomal dominant high myopia by linkage disequilibrium analysis.

Introduction: High myopia (>-6.00 diopters) is a complex common disorder that predisposes individuals to retinal detachment, glaucoma, macular degeneration, and premature cataracts. A recent linkage analysis of seven families with autosomal dominant high myopia has identified one locus (MYP2) for high myopia on chromosome 18p11.31 (Young et al.: Am J Hum Genet 1998;63:109–119). Haplotype analysis revealed an initial interval of 7.6 centimorgans (cM). Methods: Transmission disequilibrium tests (TDT) with both the Statistical Analysis for Genetic Epidemiology (SAGE) 3.1 TDTEX and GENEHUNTER 2 (GH2) programs were performed using chromosome 18p marker alleles for this interval. Results: Using SAGE analysis, the following p values were obtained for markers in marker order in this region: D18S1146 (p = 0.227), D18S481 (p = 0.001), D18S63 (p = 0.062), D18S1138 (p = 0.0004), D18S52 (p = 1.79 × 10 -6 ), and D18S62 (p = 0.141). GH2 TDT analysis revealed the following p values for the best allele for the markers: D18S1146 (p = 0.083), D18S481 (p = 0.108), D18S63 (p = 0.034), D18S1138 (p = 0.011), D18S52 (p = 0.007), and D18S62 (p = 0.479). Conclusion: These data suggest that the gene for 18p11.31-linked high myopia is most proximal to marker D18S52, with a likely interval of 0.8 cM between markers D18S63 and D18S52. Due to the contraction of the interval size by TDT, these results provide a basis for focused positional cloning and candidate gene analysis at the MYP2 locus.

Species Survey of Glutathione Peroxidase and Glutathione Reductase: Search for an Animal Model of the Human Lens

Lenses from representative species of eight mammalian orders were assayed for glutathione peroxidase and glutathione reductase activities. Wide variation of glutathione peroxidase activity was noted, the lowest activity being that of the prosimian galago while the highest activities were from three Old World monkey species of the genera Macaca and Papio. The hominoids, including the human, all exhibited lower activities of this enzyme. Glutathione reductase activity was lowest in the dog, the rabbit, and all species of cats. The higher Old World monkeys and hominoids, including the human, exhibited enzyme activities many times greater than any other species except the woodchuck. Since glutathione reductase is the rate-controlling enzyme of the glutathione redox cycle, it may be concluded that the most suitable model for the human lenticular glutathione redox cycle will only be found among the higher primates.

The effects of age on glutathione synthesis enzymes in lenses of old world simians and prosimians

The activities of gamma-glutamylcysteine synthetase and glutathione synthetase, the two enzymes required for glutathione synthesis, were determined as a function of age in lenses of three species of Old World higher primates: orangutan, pigtail monkey and olive baboon. These were compared to enzyme activities in lenses of two prosimians: mouse lemur and galago. gamma-Glutamylcysteine synthetase activity decreased as a function of age in all three Old World simians. The rate of decrease was greatest in the juvenile lenses. In contrast, the enzyme activity increased continuously with age in the galago lens. In the mouse lemur the enzyme activity increased per lens, but was constant when expressed as specific activity or as units per gram of lens. The loss of enzyme activity with age was limited to Old World higher primates apparently representing genetic change. Glutathione synthetase activity decreased logarithmically with age in the lenses of all five species.

Maintenance of hepatic glutathione homeostasis and prevention of acetaminophen-induced cataract in mice by L-cysteine prodrugs

Administration of acetaminophen (ACP, 3.0 mmol/kg, i.p.) to beta-naphthoflavone-induced C57 BL/6 mice led to the formation of bilateral cataracts within 8 hr with a 71% incidence. The hepatic glutathione (GSH) levels were reduced 99% and lenticular GSH levels reduced 42% in cataractous mice. Cataract formation was completely prevented by the co-administration of the L-cysteine prodrugs 2(R, S)-methylthiazolidine-4(R)-carboxylic acid (MTCA) and 2(R, S)-n-propylthiazolidine-4(R)-carboxylic acid (PTCA) in two divided i.p. doses totaling 4.5 mmol/kg. 2-Oxo-L-thiazolidine-4-carboxylic acid (OTCA) was nearly equipotent, yielding only one cataract in 16 mice, but D-ribose-L-cysteine (RibCys, 5/16) and N-acetyl-L-cysteine (NAC, 9/14) were much less effective. Hepatic and lenticular GSH were maintained at near normal levels by MTCA, PTCA and OTCA. These results suggest that maintenance of adequate cellular GSH levels in the presence of ACP protects against cataract induction.

Stereopsis Results at 4.5 Years of Age in the Infant Aphakia Treatment Study

PURPOSE To determine whether stereopsis of infants treated for monocular cataracts varies with the type of optical correction used. DESIGN Randomized prospective clinical trial. METHODS The Infant Aphakia Treatment Study randomized 114 patients with unilateral cataracts at age 1-7 months to either primary intraocular lens (IOL) or contact lens correction. At 4.5 years of age a masked examiner assessed stereopsis on these patients using 3 different tests: (1) Frisby; (2) Randot Preschool; and (3) Titmus Fly. RESULTS Twenty-eight patients (25%) had a positive response to at least 1 of the stereopsis tests. There was no statistically significant difference in stereopsis between the 2 treatment groups: Frisby (contact lens, 6 [11%]; IOL, 7 [13%]; P = .99), Randot (contact lens, 3 [6%]; IOL, 1 [2%]; P = .62), or Titmus (contact lens, 8 [15%]; IOL, 13 [23%]; P = .34). The median age at surgery for patients with stereopsis was younger than for those without stereopsis (1.2 vs 2.4 months; P = .002). The median visual acuity for patients with stereopsis was better than for those without stereopsis (20/40 vs 20/252; P = .0003). CONCLUSION The type of optical correction did not influence stereopsis outcomes. However, 2 other factors did: age at surgery and visual acuity in the treated eye at age 4.5 years. Early surgery for unilateral congenital cataract and the presence of visual acuity better than or equal to 20/40 appear to be more important than the type of initial optical correction used for the development of stereopsis.

Evidence for genetic heterogeneity in families with congenital motor nystagmus (CN).

Congenital motor nystagmus (CN) is a relatively common genetic disorder (approximately 1 in 1500) characterized by bilateral involuntary ocular oscillations, with onset occurring within the first six months of life. To date, three loci associated with CN have been mapped to chromosomes 6p12, Xp11.4-p11.3, and Xq26-q27. We analyzed five pedigrees segregating for CN. Mapping studies using markers in these three regions showed that only one pedigree exhibited suggestive linkage with a lod score of 2.08, straight theta=0.0, at chromosome Xp11. This pedigree had both affected male and female members, with two unaffected obligate female carriers. The remaining four pedigrees did not exhibit evidence of linkage for any of the three chromosome locations. Three of the pedigrees, Pedigrees 2, 4, and 5, exhibited several instances of male-to-male transmission, excluding X-linkage, and exhibited a lod score of -3.82, straight theta=0.0, for marker D6S459 located at 6p12, thus excluding the chromosome 6 locus. This provides evidence for at least a fourth locus associated with CN.

Reading acuity in albinism: Evaluation with MNREAD charts

INTRODUCTION The MNREAD reading acuity (RA) charts use continuous-text reading to measure (1) RA, ie, the smallest size of print that the patient can resolve; (2) maximum reading speed (MRS); and (3) critical print size (CPS), ie, the smallest print that the patient can read with maximum speed. This project used the MNREAD charts to evaluate reading performance in children and adults with albinism to determine the smallest print size recommended to facilitate effortless reading. METHODS A total of 63 subjects with albinism were administered the MNREAD test to determine the critical print size for effortless reading. The subjects read continuous, high-contrast text print until they could no longer discern the words. The MRS and CPS were determined with the MNREAD protocol. Presence or absence of nystagmus and strabismus was recorded. Distance visual acuity was measured with ETDRS charts. RESULTS The sample included 25 male and 38 female subjects with a median age of 16 years. Median MRS was 150 words per minute. The mean CPS was 0.84 logMAR, notably larger than the mean RA of 0.53 logMAR. CONCLUSIONS The MNREAD acuity charts can be used to determine functional reading ability and critical print size for effortless reading in individuals with albinism. The amount of enlargement in print size can be used in educational and vocational recommendations to facilitate reading.

Glutathione peroxidase, glutathione reductase and glutathione-S-transferase activities in the rhesus monkey lens as a function of age

The activities of glutathione peroxidase, glutathione reductase and glutathione-S-transferase were determined in lenses from rhesus monkeys (Macaca mulatta) as a function of age. The ages ranged from 137 day old embryos to a 34 year old. Glutathione peroxidase activity (units/g lens) occurred at a very low level in lenses of fetuses and neonates, but increased dramatically with age, peaking in the adult of about 12 to 20 years of age and declining thereafter. Glutathione reductase activity (units/g lens) decreased throughout juvenile life, leveling off when adulthood was reached (at least 6 years of age). Glutathione-S-transferase activity showed considerable age-related variation. Calculations show that glutathione reductase is rate-limiting in the glutathione redox pathway.

An HPLC radiotracer method for assessing the ability of L-Cysteine prodrugs to maintain glutathione levels in the cultured rat lens

PURPOSE To apply a high performance liquid chromatographic radiotracer method to test a variety of L-cysteine prodrugs and one dipeptide prodrug for their ability to synthesize glutathione in cultured rat lenses. METHODS Rat lenses were incubated for 48 h in a medium containing [14C(U)]-glycine and prodrugs. Following homogenization and derivatization, lens extracts were analyzed to determine the extent of biosynthetic incorporation of this labeled amino acid into [14C]-glutathione using high performance liquid chromatography with radioisotope and ultraviolet absorption detection. All of the thiazolidine prodrugs contained masked sulfhydryl groups to stabilize them against air oxidation. L-buthionine-(S,R)-sulfoximine-an inhibitor of the first step in glutathione biosynthesis-was present in media containing the dipeptide prodrug. RESULTS In all cases, a large [14C]-labeled peak eluted just prior to [14C]-glutathione. This peak had some characteristics of the mixed disulfide of glutathione and L-cysteine, viz., L-cysteine/glutathione disulfide, but requires further investigation in order to be positively identified. Of the eleven L-cysteine prodrugs investigated, the most effective was 2(R,S)-methylthiazolidine-4(R)-carboxylic acid, which increased the rate of [14C]-glutathione biosynthesis 35% over that of the controls. A number of other L-cysteine prodrugs were somewhat effective, increasing glutathione synthesis 5-30% over the controls, while several L-cysteine prodrugs were totally ineffective. The only dipeptide prodrug investigated, viz., gamma-L-glutamyl-L-cysteine ethyl ester, increased the biosynthesis of [14C]-glutathione 18% over control. Biosynthetic rates based on ultraviolet absorption of the derivatized glutathione demonstrated a similar pattern, the compounds most effective in synthesizing [14C]-glutathione generally yielding the highest ultraviolet glutathione concentrations and the ineffective compounds showing the lowest concentrations. CONCLUSIONS 2(R,S)-methylthiazolidine-4(R)-carboxylic acid, 2(R,S)-n-propylthiazolidine-4(R)-carboxylic acid and N-acetyl-L-cysteine were the only compounds that were statistically significant in yielding higher levels of both ultraviolet and radioactive glutathione as compared to their respective controls. Thus, these prodrugs have very promising anti-cataract potential.