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Biomedical subjects

Y S Rabinowitz

Publications and source records attributed to Y S Rabinowitz.

33 records · Page 2Linked to original sources
PubMed1993

Corneal topography.

The heightened interest in refractive corneal surgery has resulted in the increased utility of videokeratography in clinical practice. During this past year, studies have provided new information about the accuracy, reproducibility, limitations, and comparative strengths and weaknesses of different topographic devices. Videokeratography studies have yielded new information about the effects of surgical procedures such as excimer laser photorefractive keratectomy, radial keratotomy, penetrating keratoplasty, trabeculectomy, and strabismus surgery on the shape of the cornea. The use of these devices in fitting patients with keratoconus and patients who have had radial keratotomy with contact lenses is illustrated and subtle topographic abnormalities induced by rigid and soft contact lenses are reported. The early detection of keratoconus with videokeratography has provided new insights into the genetics of this disorder. Computer-assisted topographic devices are rapidly gaining acceptance as screening tools for the detection of early keratoconus in candidates for myopic refractive surgery.

Contact Lenses↗
PubMed1992

Molecular genetic analysis in autosomal dominant keratoconus.

Members in three generations of a family whose propositus had keratoconus were examined by biomicroscopy, with a corneoscope and a computer-assisted videophoto-keratoscope. Keratoconus was detected in eight of 15 family members with vertical transmission consistent with autosomal dominant inheritance. Affected individuals displayed variable topographic features. Abortive "nipple-type" cones were identified in some individuals in successive generations using the computer-assisted videophotokeratoscope and more advanced nipple-type cones detected on biomicroscopy of other family members. We selected a COL6A1 cDNA (the gene encoding the alpha 1 chain of type VI collagen) as a "candidate gene" to determine cosegregation with the disease locus. Linkage analysis excluded a gene locus for keratoconus on the most telomeric region of chromosome 21 in this family.

Adult↗
PubMed1992

Keratoconus and bilateral lattice-granular corneal dystrophies.

The occurrence of lattice and granular corneal dystrophies in the same eye has been reported in individuals who trace their families to the province of Avellino in Italy. We present the first histopathologic report of keratoconus and bilateral lattice-granular corneal dystrophies occurring in the same patient. This individual's family also originated in Avellino, Italy.

Aged↗
PubMed1991

Contact lens selection for keratoconus using a computer-assisted videophotokeratoscope.

We used the Corneal Modeling System, a digital videophotokeratoscope, as an aid in selecting the initial base curve and lens diameter for contact lenses in keratoconus patients. With this instrument we studied corneal topography in 24 keratoconus patients (33 eyes) who were being fit for the first time or who had not worn contact lenses for at least one month prior to our examination. For the purposes of fitting contact lenses, the corneas were classified according to the topographic patterns observed, and appropriate fitting strategies were adopted for each subgroup. Diagnostic lenses and their fluorescein patterns were analyzed for the desired cornea-lens relationship. Topographic analysis of the cornea provided a rational basis for selecting appropriate trial contact lenses for our patients.

Adolescent↗
PubMed1990

Computer-assisted corneal topography in family members of patients with keratoconus.

In about 6% of patients with keratoconus, there is a history of familial disease. High keratometric astigmatism and mildly irregular mires observed by placidois disc have been suggested to represent variable forms of expression of a gene in family members of patients with keratoconus. We used a computer-assisted digital videophotokeratoscope to map the corneas of 28 family members of 5 patients with keratoconus. Abnormalities observed in family members included central steepening, greater steepening of the cornea inferior to the apex, and substantial asymmetry in the central dioptric power between the two eyes of the same individual. These findings were similar to, but less severe than, those found in patients with keratoconus and may represent the variable expression of a gene contributing to the development of keratoconus. Pedigree analysis in these families suggests an autosomal dominant mode of inheritance.

Adolescent↗
PubMed1988

Cosegregation of X-linked retinitis pigmentosa and hemophilia A.

We examined a family pedigree in which retinitis pigmentosa and hemophilia A were inherited in an X-linked manner. Six female carriers were identified by electroretinography. Results of ophthalmoscopic examination were normal in two women, while four displayed marked variability in phenotypic expression. Six of seven males identified with retinitis pigmentosa had hemophilia A. One asymptomatic boy had a markedly abnormal electroretinogram despite normal ophthalmoscopic examination. Pedigree analysis showed a high recombination rate, which would be expected as these two genes are known to be at opposite arms of the X chromosome.

Adolescent↗
PubMedDate not supplied

Keratoconus.

Keratoconus is a bilateral noninflammatory corneal ectasia with an incidence of approximately 1 per 2,000 in the general population. It has well-described clinical signs, but early forms of the disease may go undetected unless the anterior corneal topography is studied. Early disease is now best detected with videokeratography. Classic histopathologic features include stromal thinning, iron deposition in the epithelial basement membrane, and breaks in Bowman's layer. Keratoconus is most commonly an isolated disorder, although several reports describe an association with Down syndrome, Leber's congenital amaurosis, and mitral valve prolapse. The differential diagnosis of keratoconus includes keratoglobus, pellucid marginal degeneration and Terrien's marginal degeneration. Contact lenses are the most common treatment modality. When contact lenses fail, corneal transplant is the best and most successful surgical option. Despite intensive clinical and laboratory investigation, the etiology of keratoconus remains unclear. Clinical studies provide strong indications of a major role for genes in its etiology. Videokeratography is playing an increasing role in defining the genetics of keratoconus, since early forms of the disease can be more accurately detected and potentially quantified in a reproducible manner. Laboratory studies suggest a role for degradative enzymes and proteinase inhibitors and a possible role for the interleukin-1 system in its pathogenesis, but these roles need to be more clearly defined. Genes suggested by these studies, as well as collagen genes and their regulatory products, could potentially be used as candidate genes to study patients with familial keratoconus. Such studies may provide the clues needed to enable us to better understand the underlying mechanisms that cause the corneal thinning in this disorder.

Cornea↗
PubMedDate not supplied

Videokeratography of keratoconus in monozygotic twins.

PURPOSE: To determine the corneal topographic appearance in a pair of monozygotic twins and family members of the twins because one of the twins had keratoconus and the other appeared normal by clinical examination. METHODS: Clinical examination and videokeratography (Topographic Modeling System, Tomey) of the patient, his monozygotic twin brother, an older brother, and his parents were performed. The I-S values (difference in the average dioptric powers of symmetrical points between the inferior and superior cornea) were calculated. RESULTS: The patient, a 28-year-old man, had clinical keratoconus confirmed with videokeratography. Clinical examination of family members including a twin brother, an older brother and both parents revealed no corneal abnormalities. Videokeratography of the clinically normal twin brother showed inferior steepening with progression over time. The I-S value of the clinically normal brother was 1.36 (right eye) (greater than 2.00 SD of normal controls), which progressed to 1.69 (right eye), 1.32 (left eye) 5 months later and to 1.87 (right eye), 1.43 diopters (D) (left eye) 14 months later. Minimal asymmetric inferior steepening was noted in an older brother who had an I-S value of 0.81 (right eye), 1.27 (left eye). The mother appeared topographically normal. CONCLUSIONS: This study lends support to the existence of subclinical keratoconus detectable by videokeratography only.

Adult↗
PubMedDate not supplied

Computer-assisted corneal topography in keratoconus.

Using a computer-assisted video-keratoscope, we determined the topographic findings of 14 eyes of 10 patients with keratoconus. None of these patients had worn contact lenses for at least one year prior to examination and were thus free of contact lens-induced topographical alterations. Two patterns commonly seen included inferior steepening more prominent temporally, and central steepening with a superimposed asymmetric bowtie pattern. When compared with normal eyes three quantitative parameters were significantly different (p less than 0.001): central corneal power, difference in corneal power between fellow eyes in the same patients, and steepening of the inferior cornea compared with the superior cornea. Study of the topography in keratoconus using this technique may prove useful for documenting the pattern of involvement of the anterior corneal surface and providing new insights into the pathogenesis of this condition.

Adolescent↗
PubMedDate not supplied

Keratoconus detected by videokeratography in candidates for photorefractive keratectomy.

BACKGROUND: Patients with corneal shape abnormalities should be identified prior to photorefractive keratectomy (PRK). We used videokeratography screening to detect subclinical corneal abnormalities, including keratoconus, which might have been missed by conventional clinical evaluation. METHODS: One hundred forty-six apparently normal myopic eyes (-1.00 to -7.00 diopters [D] with less than 1.50 D of cylinder) of 91 consecutive patients who were candidates for PRK were screened by videokeratography. RESULTS: In 6 of 91 patients (7 of 146 eyes), unsuspected corneal shape abnormalities were detected by videokeratography. Two patients had definite keratoconus and three were classified as keratoconus suspects by inferior corneal steepening (Rabinowitz I-S index ranging from 1.62 to 6.20 D). One patient had early pellucid marginal degeneration. CONCLUSIONS: Keratoconus suspects and contact lens-induced changes resembling keratoconus are present in the "normal" myopic population that presents for refractive surgery. Videokeratographic screening is the only effective means of identifying these and other corneal shape abnormalities.

Adult↗