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. 2010 Oct;121(2):85-91.
doi: 10.1007/s10633-010-9232-3. Epub 2010 May 4.

Cone ERG Responses in Patients With Smith-Lemli-Opitz Syndrome (SLOS)

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Free PMC article

Cone ERG Responses in Patients With Smith-Lemli-Opitz Syndrome (SLOS)

Deirdre Garry et al. Doc Ophthalmol. .
Free PMC article

Abstract

Purpose: To evaluate cone and cone-driven retinal function in patients with Smith-Lemli-Opitz syndrome (SLOS), a condition characterized by low cholesterol. Rod and rod-driven function in patients with SLOS are known to be abnormal.

Methods: Electroretinographic (ERG) responses to full-field stimuli presented on a steady, rod suppressing background were recorded in 13 patients who had received long-term cholesterol supplementation. Cone photoresponse sensitivity (S(CONE)) and saturated amplitude (R(CONE)) parameters were estimated using a model of the activation of phototransduction, and post-receptor b-wave and 30 Hz flicker responses were analyzed. The responses of the patients were compared to those of control subjects (N = 13).

Results: Although average values of both S(CONE) and R(CONE) were lower than in controls, the differences were not statistically significant. Post-receptor b-wave amplitude and implicit time and flicker responses were normal.

Conclusions: The normal cone function contrasts with the significant abnormalities in rod function that were found previously in these same patients. Possibly, cholesterol supplementation has a greater protective effect on cones than on rods as has been demonstrated in the rat model of SLOS.

Figures

Fig. 1
Fig. 1
A boy with Smith-Lemli-Opitz Syndrome. There is mild facial dysmorphia with turned up nose, anteverted nares, and small chin.
Fig. 2
Fig. 2
Sample records. (A) Cone mediated ERG records from 9-year-old patient 2. (B) Fit of Eq. 1 (dashed lines) to the a-wave. The calculated values of SCONE and RCONE are shown.
Fig. 3
Fig. 3
Photoresponse parameters in 13 patients with SLOS and 13 control subjects. (A) SCONE is the sensitivity parameter. (B) RCONE is the amplitude of the saturated cone response. The horizontal lines indicate the mean for each group.
Fig. 4
Fig. 4
Sensitivity parameters, SCONE and SROD, and saturated amplitude parameters, RCONE and RROD, as a percent of the mean (100%) in control subjects.
Fig. 5
Fig. 5
Cone-driven b-wave amplitude (A) and implicit time (B) as a function of stimulus intensity. Mean and standard error of the mean for patients with SLOS and controls are shown. ANOVA showed no significant differences in either amplitude (F= 0.164; df 1,6; ns) or implicit time (F=1.58; df 1,6; ns).

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