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 nerve hypoplasia and small eyes in presumed amblyopia.

PURPOSE: To assess the anatomy of eyes presumed to be amblyopic and their fellow eyes. PARTICIPANTS: Two hundred seventy-five patients diagnosed with amblyopia and 88 healthy or glaucomatous subjects. METHODS: All subjects underwent complete examinations, including cycloplegic refraction, slit lamp examination, ophthalmoscopy, and retinal imaging. Axial lengths were determined on 263 amblyopic and 88 healthy and glaucomatous subjects by ultrasonic biometry. MAIN OUTCOME MEASURES: Optic disc areas were determined by magnification correction of disc images performed with formulas. Dysversion of the optic disc was determined by simultaneous viewing of disc photographs, digitized images of both eyes, or both. RESULTS: The mean disc area of eyes presumed to be amblyopic was 1.72 mm(2) +/- 0. 73 SD and 1.95 mm(2) +/- 0.69 SD for nonamblyopic eyes (P =.0017). The mean disc area for 176 optic discs of glaucomatous and healthy eyes was 2.61 mm(2) +/- 0.95 SD. The mean axial length for eyes in the general population is 23.65 mm +/- 1.35 SD. The healthy and glaucomatous group in this study had a mean axial length of 23.89 mm +/- 1.29 SD. The eyes with poorer vision that were assumed to be amblyopic averaged 22.42 mm +/- 2.01 SD in length, whereas their nonamblyopic fellow eyes averaged 22.83 mm +/- 1.89 SD (P =.022). The differences between eyes in the healthy population and eyes that are presumably amblyopic, as well as the healthy and fellow eyes, are highly significant (P <.0001)(7.0 x 10(-16)). CONCLUSION: Vision impairment in presumed amblyopia is associated with optic nerve hypoplasia with relative microphthalmos, which is more notable in those eyes with poorer vision.

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

PURPOSE: Our purpose was to evaluate anatomic variations of eyes presumed to be amblyopic. METHOD: Computer 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. RESULTS: Ninety-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. CONCLUSION: Optic 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.

Evaluation of posterior subcapsular cataracts. With spatial contrast acuity.

A new microcomputer-controlled instrument that tests contrast acuity is described. It displays a range of Sloan optotype sets at five different levels between 3 and 95% contrast. The spatial contrast acuities of two groups were compared with this instrument. The first group consisted of 68 eyes of patients with posterior subcapsular cataracts whose conventional, high-contrast visual acuity was 20/60 or better. The second group was comprised of 146 eyes with normal vision. The posterior subcapsular cataract group had greater variation in visual performance and a more pronounced decrease in spatial acuity at lower contrasts than did the normal group. This study indicates that high-contrast acuity measurements, in patients with posterior subcapsular cataracts, do not predict acuity at other contrast levels.