Philip Lempert

Dysversion of the optic disc and axial length measurements in a presumed amblyopic population

PURPOSEnOur purpose was to evaluate anatomic variations of eyes presumed to be amblyopic.nnnMETHODnComputer imaging and photography of the optic discs of 205 amblyopic subjects were performed and the axial lengths of 183 of the subjects were measured. The paired optic nerve images were evaluated for symmetry of disc contours and orientation of central blood vessels to detect optic nerve head dysversion. Dysversion of the optic nerve head, which is also referred to as segmental hypoplasia, is a congenital disorder characterized by the central retinal vessels emerging temporal to the vertical midline of the disc and being directed nasally or the nerve head tilting in a vertical direction resulting in a downward or oblique tilting of the discs with the blood vessels emerging at the superior or inferior disc rim.nnnRESULTSnNinety-three subjects had optic nerve dysversion. There was a greater degree of anisometropia (P< or =.004) in subjects with dysversion (anisometropia factor of 2.51+/-2.15) than in the subjects with symmetric discs (anisometropia factor of 1.76+/-1.63). Axial lengths of the amblyopic eyes were significantly smaller (P<.0001) than those of the nonamblyopic eyes. There was no statistical difference (P< or =.879) in length between amblyopic eyes with dysversion and those with symmetric discs.nnnCONCLUSIONnOptic disc dysversion was identified in 45.4% of patients who were previously assumed to be amblyopic. There are anatomic malformations in the eyes of a significant proportion of the presumed amblyopic population. This suggests that, in these individuals, congenital peripheral factors rather than impaired cortical development may be responsible for decreased unilateral acuity.

Retinal Area and Optic Disc Rim Area in Amblyopic, Fellow, and Normal Hyperopic Eyes: A Hypothesis for Decreased Acuity in Amblyopia

PURPOSEnDefects in visual functions in amblyopic eyes may have a neuroretinal explanation. The retinal area to optic disc rim area ratios of hyperopic normal, amblyopic, and fellow eyes were evaluated.nnnDESIGNnCase-controlled study.nnnPARTICIPANTSnA total of 293 patients with amblyopia and bilateral hyperopia and 77 non-amblyopic bilaterally hyperopic patients without strabismus.nnnMETHODSnDisc areas were measured using magnification correction formulas developed by Bengtsson and Krakau. Axial lengths were determined by ultrasound biometry or laser interferometry with a Zeiss AOL Master (Carl Zeiss Co., Oberkochen, Germany). The visual area of the retina was calculated using axial length measurements.nnnMAIN OUTCOME MEASURESnOptic disc rim areas, corrected for magnification, retinal areas, and a derived ratio, retinal area/disc rim area (RetA/DRimA).nnnRESULTSnThe RetA/DRimA for the amblyopic eyes was significantly greater than that of the fellow and normal eyes, indicating that amblyopic eyes have larger retinal receptor areas than fellow or normal eyes. The RetA/DRimA of the fellow eyes was smaller than for the amblyopic but larger than that of the normal eyes. These differences were due to smaller optic disc rim areas in the amblyopic and fellow eyes.nnnCONCLUSIONSnAmblyopic and their fellow eyes, when compared with normal eyes, have reduced innervations of comparable retinal areas. These differences can be attributed to a paucity of nerve fibers, as indicated by the smaller neuroretinal rim areas.nnnFINANCIAL DISCLOSURE(S)nThe authors have no proprietary or commercial interest in any materials discussed in this article.

Grading nuclear cataract: reproducibility and validity of a new method

AIMS To assess the reproducibility and validity of a new instrument for grading nuclear cataract—the laser slit lamp, by comparison with an established method of lens grading—the Lens Opacities Classification System III (LOCS III). METHODS 62 volunteers (113 eyes) were examined on two occasions. At each visit, a video image of the anterior segment was captured with the laser slit lamp and stored digitally. A measure of lens opacity for each laser slit lamp image was calculated using image analysis software. Each lens was also photographed on both visits for LOCS III grading of nuclear colour and nuclear opalescence. RESULTS There was a linear increasing relation between the laser slit lamp measure of nuclear lens opacity and the LOCS III nuclear opalescence scores. The overall reproducibility of the laser slit lamp measurement was comparable with LOCS III (intraclass correlation coefficient of 95% (95% CI 92.9–96.5) for the laser slit lamp method; 97% (95% CI 95.6–97.9) for the LOCS III method). However, among healthy subjects, the reproducibility was lower (intraclass correlation for the laser slit lamp of 38.6% (95% CI 12.9–59.2) and 76.1% (95% CI 62.3–85.4) for LOCS III. CONCLUSION The laser slit lamp appears to give a valid measurement of nuclear cataract. The reproducibility of the instrument was high and similar to that of LOCS III. Modifications to the design would have to be made to improve its reproducibility among healthy subjects. It is simpler than other objective instruments, and could be useful in large scale studies of cataract.

Optic Disc Area and Retinal Area in Amblyopia

Purpose: To compare retinal area to optic disc rim area ratios of hyperopic normal, strabismic eyes with equal acuity, amblyopic, and fellow eyes. Methods: Neuroretinal rim areas of 293 amblyopic and fellow eyes, and 77 non-amblyopic hyperopic right eyes, and 84 non-amblyopic strabismic right eyes were measured by magnification corrected retinal photography and planimetry. Retinal area estimates were based on axial lengths. Inclusion criteria: All subjects had bilateral hyperopia. Patients with glaucoma or known optic nerve atrophy were excluded. The normal and strabismic groups had equal visual acuity in each eye better than 20/40. The amblyopic group had acuity worse than 20/40 in one eye uncorrectable with lenses and without gross anatomic defects. Results: The amblyopic group included 137 with strabismus and 89 with anisometropia exceeding 1.5 diopters. There were highly significant differences between the ratio of retinal area to optic disc rim area of the amblyopic and of normal eyes (unpaired t-test, p = 8.6 × 10-6), the amblyopic and strabismic right eyes (unpairedt−test, p = 4.22 × 10-8) as well between the fellow and amblyopic eyes (pairedt−test, p = 2.13 × 10-5). The difference between the normal and strabismic eyes without amblyopia was not significant (p = 0.82). There was a 20 percent increase in the retinal receptor areas of hyperopic amblyopic eyes as compared to hyperopic eyes without amblyopia despite reduced retinal areas in the amblyopic eyes. Dysplastic and/or asymmetric optic discs were present in 163 of 293 (56 percent) amblyopic patients, 47 of 84 (56 percent) strabismic, and 10 of 77 (13 percent) normal patients. Conclusions: The increase in the receptor area may be an explanation for diminished acuity and impaired visual function in amblyopic eyes.

Amblyopia prevalence and cigarette smoking by women

The relationship between cigarette smoking by young women and amblyopia in children was investigated in 13 population groups. Two searches were conducted on Medline using the following keywords for the first search: amblyopia, prevalence or incidence, and the names of specific countries. The keywords for the second search were smoking, cigarettes, women and the names of the same specific countries. Relevant articles were reviewed. A positive relationship between the rate of smoking among women and the prevalence of amblyopia in school‐aged children and military recruits was found. The Pearson correlation coefficient was 0.73. The occurrence of decreased visual acuity attributed to amblyopia in disparate population groups is directly related to rates of cigarette smoking by young women.

The Pediatric Eye Disease Investigator Group Report May Be Too Optimistic About Efficacy of Treatment

To the Editor.— The Quinn et al commentary1 comparing the efficacy of various patching protocols for the treatment of amblyopia confirms a previous compilation of multiple reports2 that found no relationship between duration or type of therapy used and visual outcome. Performance improvement on vision tests normally occurs in children with increasing age, literacy, and experience.3 Improved acuity also was demonstrated in clinical trials in which acuity of the patched eyes improved at the same rate as the unpatched eyes.4 The conclusions concerning the efficacy of treatment in the commentary, reached without the benefit of a control group or correcting for placebo effects, might therefore be too optimistic. For example, a previous Pediatric Eye Disease Investigator Group (PEDIG) study reported that baseline visual acuity in the amblyopic eyes at age of enrollment showed a steady improvement with increasing age before treatment. The percentage of children with 20/100 at 3 years old was 40%, and this percentage decreased to 19% at age 6 years. Only 7% of children had acuities of 20/50 at age 3 years in the poorer eye, and this percentage increased to 27% at age 6 years before treatment was instituted.5 Patient selection in the PEDIG studies presents another cause for concern. From 47 clinical sites, 209 children were recruited.6 These sites were all active pediatric practices that each certainly contained 5 children with amblyopia. The winnowing that occurred “allows bias to enter in and constitutes a subtle manipulation of trial results.”7 Success in amblyopia treatment is usually defined in terms of relative improvement rather than achievement of a specified functional status. For the majority of patients, successful treatment (by this criterion) will still not result in normal vision or even vision levels adequate for driving or reading. Therefore, positive comments about outcome may raise expectations that will not be fulfilled. Amblyopia is a diagnosis of exclusion made only after organic causes for decreased acuity have been eliminated. Diagnostic modalities have improved8,9 since the original definitions of amblyopia were developed 2 centuries ago,10 but there still is an almost total reliance on subjective ophthalmoscopic observations and patient responses. Readily available methods such as biometry, retinal photography, and magnification-corrected optic-disk imaging that permit documentation of optic-nerve hypoplasia12 and/or dysplasia12 are rarely used, even by research groups. The practice of medicine requires constant reevaluation of traditional concepts and methods as new modalities for diagnosis and prevention become available. The acceptance of occlusion as the unquestioned mainstay of treatment for unilateral poor vision in children risks imposing unnecessary treatment and distracts researchers from investigating measures to prevent impaired vision in childhood.

Myopia in diethylstilboestrol exposed amblyopic subjects

Editor,—Diethylstilboestrol (DES) is a synthetic, non-steroidal pseudo-oestrogen. It was prescribed for many pregnant women between 1948 and 1971 with the intention of preventing spontaneous abortions and premature delivery.1 nnEmbryonic neural tissue is particularly sensitive to gonadal hormones which play a vital part in axonal growth.2 “Estrogen and androgen appear to induce inherent neural programs in which androgen increases neurite arborization and the receptive field of individual cells, increasing the likelihood for intercellular communication, while estrogen actually induces this communication, in the form of spines, …

New instrument for objective density measurement of the crystalline lens nucleus: correlation of visual acuity with nuclear density

Objective evaluation of nuclear cataracts would facilitate clinical activities and research studies. This presentation describes a new device using a helium-neon laser beam configured as a sheet of light. Computerized equipment was used for imaging and objective analysis of the lens nucleus. Visual acuity and density measurements of the crystalline lens nucleus were compared in 262 eyes. These included normals and patients with nuclear sclerosis or nuclear cataracts without other visually significant pathology. The coefficient of correlation between acuity and mean nuclear density was 0.78. Thirty-two eyes were examined twice and had no change in visual acuity between the two visits. These paired density measurements had a correlation coefficient of 0.96. Fifteen patients who did have decreased acuity between the two examinations had a correlation between the two measurements of 0.33. The intensity of nuclear sclerosis or cataract, as well as density changes, can be objectively measured and correlated to visual acuity degradation with this instrument.