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Biomedical subjects

M C Mehta

Publications and source records attributed to M C Mehta.

At least 37 records · Page 2Linked to original sources
PubMed1993

Correlating visual acuity and electrooculogram recordings in Best's disease.

The visual function in 54 eyes of 27 patients with Best's disease was analyzed by retrospectively examining the Snellen visual acuities and the electrooculogram (EOG). Visual acuities, generally well maintained in most patients, were 20/40 (0.5) or better in 41 of 54 (75.9%) eyes, and showed no correlation with age. Those in the cicatricial stage had worse visual acuities than those in the previtelliform stage. The EOG was abnormal in 47 eyes (87.0%) with a subnormal light peak/dark trough (Lp/Dt) ratio less than 1.85. Seven eyes (13.0%) with an Lp/Dt ratio 1.85 or higher had significantly smaller Dt values compared with those with a low Lp/Dt ratio. The Lp/Dt ratio did not correlate with patient age or disease stage. No correlation existed between visual acuities and Lp/Dt ratios. The Lp/Dt ratio did not reflect the severity of the macular lesions. The results indicate that not only a low Lp/Dt ratio but also a low dark trough value in cases with a normal Lp/Dt ratio are helpful in diagnosing Best's disease.

Adolescent↗
PubMed1993

Measuring vision with temporally modulated stripes in infants and children with ROP.

PURPOSE: To determine differences in preferential looking (PL) acuities using stationary and temporally modulated stripe patterns in patients with various stages of retinopathy of prematurity (ROP). METHODS: We measured the PL acuities of 134 patients (ages 4 mo to 13 yr) with various stages of ROP. Patients were divided into six subgroups according to PL vision measured with stationary stripes: (1) equal to or better than 20/200 (n = 24); (2) worse than 20/200 to 20/400 (n = 10); (3) worse than 20/400 to 20/800 (n = 15); (4) worse than 20/800 to 20/1600 (n = 13); (5) worse than 20/1600 to 20/6400 (n = 26); and (6) worse than 20/6400 (n = 46; no stationary vision). RESULTS: In the group with PL acuity equal to or better than 20/200, no difference in vision was apparent between the two methods. In patients with acuities worse than 20/200 to 20/400, the temporally modulated PL acuities were 0.23 octave better than the PL acuities measured with the stationary stripes. The difference increased to 0.86 and 1.12 octaves in the groups with visual acuities worse than 20/400 to 20/800 and worse than 20/800 to 20/1600, respectively. The difference in the group with PL acuities worse than 20/1600 to 20/6400 was 1.69 octaves. The 46 patients with no stationary vision detected only the temporally modulated stripes. CONCLUSIONS: The results suggest that the PL acuity difference between the temporally modulated and stationary stripes increases with visual impairment. Measuring PL acuity with temporally modulated stripes is an important addition to the evaluation of severely visually impaired subjects.

Adolescent↗
PubMed1992

Pattern reversal visual-evoked response as a prognostic indicator in macular gliosis.

We recorded the preoperative pattern reversal visual-evoked responses in 16 subjects (16 eyes) with macular gliosis who underwent membrane-peeling operations. A postoperative visual improvement of one octave or more was observed in 11 of 16 eyes (68.8%). Preoperatively, ten eyes had peak amplitudes greater than or equal to 2 microV, all 11 eyes had either lowpass or bandpass curve shapes, and ten eyes had recordable responses to 20- or 10-minutes of an arc check sizes. Each of the three preoperative criteria was significantly associated with a postoperative visual improvement of one octave or more (P = .01, .02, and .02, respectively). These results demonstrate that the preoperative pattern reversal visual-evoked response can objectively assess the function of the underlying macula in patients with macular gliosis and, consequently, is helpful in determining which patient would most likely benefit from a membrane-peeling operation.

Adult↗
PubMed1992

Electrophysiological findings in paraneoplastic retinopathy.

Paraneoplastic retinopathy is a cancer-related non-metastatic retinopathy mainly associated with lung cancer. We examined two patients with presumed paraneoplastic retinopathy, both ophthalmologically and electrophysiologically. Both patients presented with initial visual complaints of moderate reduction of visual acuity. No specific fundus anomaly was found in the fundus except for a mild attenuation of the retinal arteries. The electroretinogram and pattern reversal visual evoked responses were either markedly reduced in amplitude or non-recordable. The electrooculogram recorded in one patient demonstrated a markedly reduced light peak/dark trough ratio. These results indicate the presence of a severe and diffuse bilateral retinal dysfunction, despite the relatively good visual acuities and mild fundus changes. Electrophysiological evaluations play an important role in the diagnosis of paraneoplastic retinopathy.

Aged↗
PubMed1991

Development of vision in retinopathy of prematurity.

Serial measures (range, two to eight) of preferential-looking grating acuities of 52 infants with retinopathy of prematurity were made. Group 1 patients (n = 11), who had little or no macular displacement, had normal preferential-looking acuity except for two who had mild acuity deficits. None of the group 2 patients (n = 12), who had dragged maculas, ever had normal acuity. On the average, their acuities, which ranged from 1 to 6 octaves less than normal, gradually increased at a rate not significantly different from normal. Group 3 patients (n = 29), who had undergone open-sky vitrectomy, had significantly lower acuity despite reattachment of the retina.

Aging↗
PubMed1991

Gyrate atrophy of the choroid and retina in a 5-year-old girl.

A 5-year-old Asian-Indian female presented with bilateral cobblestone-like peripheral lesions, a single area of chorioretinal atrophy, infero-nasal to the disc, in her right eye and a non-recordable single flash ERG. Serum ornithine level was assayed at 841 mumol/l, ten times normal levels, and a diagnosis of gyrate atrophy, due to ornithine aminotransferase deficiency was made. The patient was refractory to any form of therapy and her clinical lesions spread rapidly in both eyes, showing both centrifugal and centripetal spread in her right eye. A rapid deterioration in her psychophysical tests was also seen over the 28 months follow-up. The presence of cobblestone-like peripheral lesions in a child should alert the clinician to the possibility of gyrate atrophy, and the rapid spread of the chorioretinal lesions coupled with non-recordable single flash ERGs, in a young patient may suggest a much poorer prognosis.

Child, Preschool↗
PubMed1991

Topographical analysis of peripheral vs central retina with pattern reversal visual evoked response and the scanning laser ophthalmoscope.

The contribution of the central and the surrounding peripheral retina to the pattern reversal visual evoked response (PVER) was analyzed simultaneously using double frequency stimulation and the Fast Fourier transform (FFT) method. The Scanning Laser Ophthalmoscope (SLO) was used to project the pattern stimulus, a square subtending 10 degrees on a side, on a specific location in the fundus and to monitor accurately the stimulus' position during PVER testing. When the stimulus area on the central retina was less than or equal to 50 min of arc on a side, or 0.69% of the total area was stimulated (a square of 10 degrees on a side), the contribution from the central retina was negligible, and the PVER was dominated by surrounding peripheral retinal activity. When the stimulus area of the central retina was greater than or equal to 100 min of arc on a side, or 2.78% of the whole area was stimulated, activity from the central retina became more evident. When the stimulus area projected on the central retina became 150 min on a side (6.25% of the area or greater), activity from the central retina showed an increase and exceeded that of the peripheral retina. When the central area became larger, its activity dominated the PVER, and the contribution from the peripheral retina became negligible at this stage. The PVER was highly dependent upon the activity of the central retina, and activity levels from the central and surrounding peripheral retina were correlated.

Adult↗
PubMed1991

Electrophysiological findings in peripheral uveitis.

Nine patients with peripheral uveitis were studied clinically and electrophysiologically. Electroretinographic findings varied widely from supernormal to nonrecordable responses, depending on the disease duration and severity. These results suggest that the pathology in peripheral uveitis is not necessarily limited to the inferior pars plana but can be diffuse and widespread. In the final stage of the disease, the fundus showed extensive pigmentation and narrow retinal arteries associated with a nonrecordable electroretinogram, similar to retinitis pigmentosa. Burned-out peripheral uveitis should be considered in the differential diagnosis of secondary pigmentary degeneration.

Action Potentials↗
PubMed1990

Effect of topical dexamethasone on the ocular allergic reaction in passively sensitized guinea pigs.

We examined the effect of extended topical pretreatment with dexamethasone (Dex) on the ocular allergic response in passively sensitized guinea pigs. The passive IgG1 antibody dependent guinea pig model used in these studies demonstrates both early- and late-phase ocular anaphylactic reactions. Fourteen hours prior to challenge with the hapten di-DNP-lysine, three groups of guinea pigs were sensitized subconjunctivally with antiserum rich in IgG1 anti-DNP antibodies in both eyes (group 1, n = 11) or in one eye (group 2, n = 9; group 3, n = 10). The contralateral eyes of animals in groups 2 and 3 received normal guinea pig serum. At 1-hour intervals, beginning 6 h prior to challenge, guinea pigs in group 1 received 0.1% Dex in 0.5% hydroxymethylcellulose (MC) topically in one eye and 0.5% MC in their other eye. Animals in group 2 were treated on the same schedule with 0.5% MC only in both eyes. Animals in group 3 were not pretreated. Conjunctival edema, conjunctival erythema, periorbital swelling, and lid erythema were scored independently in the upper and lower lids of both eyes of all animals for 10 h. Comparisons between the scores of Dex-pretreated eyes in group 1 and MC-pretreated eyes in group 2 or untreated eyes in group 3 revealed no significant differences in any clinical sign at 0.5 h (early-phase reaction). However, these comparisons demonstrated significant reductions in all four clinical signs in animals of groups 1 from 1 to 8 h and marked reduction or complete absence of signs from 6 to 10 h (late-phase reaction).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1983

Regional lymph node involvement in tuberculoid leprosy.

A study of regional lymph nodes in 44 cases of proved tuberculoid leprosy (BT & TT) is presented. Out of 26 cases of tuberculoid polar (TT) leprosy, 76.92% showed presence of paracortical lymphocytes, 61.52% showed presence of granuloma and 11.54% showed presence of acid fast bacilli in lymph nodes. In the borderline tuberculoid (BT) group, 61.1% showed granuloma, 72.22% showed presence of paracortical infiltration by lymphocytes and 11.11% showed presence of A.F.B. in lymph nodes. Lesions of tuberculoid leprosy have been conclusively demonstrated in the low resistant tuberculoid (BT) leprosy and polar tuberculoid leprosy (TT). The presence of paracortical lymphocytes in large numbers in the lymph nodes could indicate high cell mediated immunity (CMI) and possibly a tuberculoid end of the spectrum. The skin lesions and lymph nodes had comparative histopathology.

Adolescent↗
PubMed1982

Study of renal changes in leprosy.

Renal lesions observed in 50 cases of chronic leprosy are reported. They include membranous and membranoproliferative glomerular lesions and amyloidosis forming one type possibly resulting from immune complexes. They also include lesions like chronic interstitial nephritis resulting from opportunistic secondary infections and/or drug toxicity. The evaluation of these lesions is discussed and appropriate remedial measures are suggested in the management of leprosy.

Amyloidosis↗