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How To Measure Slab-Off and Reverse Slab-Off Spectacle Lenses
72
Abstracts
How To Measure Slab-Off and Reverse Slab-Off Spectacle Lenses Alexander Christoff CO, COT, David L. Guyton MD; Wilmer Eye Institute at Johns Hopkins Hospital, Baltimore, MD Vertical diplopia while reading can occur when glasses are made for an anisometropic individual. The difference in the powers of the lenses induces a prismatic difference that can cause double vision in off-center areas of the lenses when patients try to read through anisometropic corrections. This induced prismatic effect can be compensated at one level of downgaze by the use of slab-off or reverse slab-off prism, where typically the slab-off correction is ground into the stronger minus, or weaker plus, lens. Slab-off lenses can also be used for patients who demonstrate vertical strabismus at near fixation only, or where the magnitude of the vertical deviation is worse at near versus at distance. Unfortunately, determining the amount of slab-off prism already incorporated into spectacle lenses is nonintuitive and inconvenient, usually requiring the use of a lens clock, not widely accessible to many ophthalmology practices. A simple technique, described in the past but poorly known, is illustrated for quickly measuring slab-off and reverse slab-off prism prescription lenses in the clinic with a common manual lensmeter. Assessment of Magnocellular and Parvocellular Pathways in Early- versus Late-Onset Amblyopes Using Motion and Color VEP Alison R. Davis, Madgella N. Neveu, Chris R. Hogg, Michael J. Morgan, Graham E. Holder, John J. Sloper; Moorfields Eye Hospital, London, UK Aim: Studies in nonhuman primates indicate that monocular visual deprivation starting at different ages has different effects on the parvocellular and magnocellular pathways. We examined whether subjects with strabismic amblyopia of onset before (early) or after 18 months (late) of age have different electrophysiological responses to motion onset and color appearance stimuli. Method: Motion onset VEPs were recorded in 15 early and 12 late onset strabismic amblyopes and 19 normal subjects using an achromatic 0.8-cpd vertical square wave grating. There was no difference in mean Log MAR acuities between the early- and late-onset amblyopes. Color VEPs were recorded in 14 early- and 13 late-onset strabismic amblyopes and 17 normal subjects using a 3.2-cpd equiluminant red/green pattern onset sine-wave grating. Between-eye comparisons were made using paired t-tests and between-group comparisons were made using unpaired t-tests. Results: Motion onset VEP latencies were shortened in amblyopic (171.0 ⫾ 12.4 ms; P ⫽ 0.041) and fellow eyes (167.6 ⫾ 10.7 ms; P ⫽ 0.001) of all amblyopes compared to normal (178.1 ⫾ 9.5 ms). The latencies from amblyopic eyes were significantly longer than those from fellow eyes (P ⫽ 0.024). There was little difference between earlyand late-onset amblyopes. Color VEP latencies in the amblyopic eyes of late onset amblyopes (149.9 ⫾ 25.3 ms) were significantly longer than normal (125.2 ⫾ 11.3 ms; P ⫽ 0.001) and fellow eyes (131.7 ⫾ 13.8; P ⫽ 0.024). In early-onset amblyopes there was no significant difference between amblyopic (131.0 ⫾ 22.1 ms) and fellow eyes (132.3 ⫾ 15.6) nor either eye and normal. The difference in latency between early- and late-onset amblyopic eyes was significant (P ⫽ 0.048). Conclusions: These results suggest different changes in magnocellular and parvocellular function in both amblyopic and fellow eyes between early- and late-onset strabismic amblyopes.
Journal of AAPOS Volume 10 Number 1 February 2006 How Often Are Our Patients’ Spectacle Lenses Dispensed as Prescribed? Arlene V. Drack MD, Rebecca Sands MD, Colleen Smith COT, Ted Curtis MD, Cameile Moore CO, Cathy O’Donnell COA; University of Colorado, Aurora, CO Introduction: Our purpose was to determine the frequency of inaccurate glasses prescriptions being dispensed to our patients. Methods: Chart review from 11 outpatient clinic sessions for three pediatric ophthalmologists. Spectacle prescriptions written were compared to actual prescription measured at next visit. Differences of ⱖ0.50 D sphere or cylinder, and ⬎5 degrees in cylinder axis, were considered inaccurate. Differences of ⬎1 D sphere/cylinder, or ⱖ10 degrees in cylinder axis, were considered potentially amblyogenic. Results: Seventy-nine charts were identified in which patients had been prescribed glasses and had the lenses measured on return visit. Twenty-five percent were inaccurate according to our criteria. Three of 79 (3.8%) were potentially amblyogenic. In one case ⫹13.50 was prescribed and ⫺14.50 ⫹ 0.75 ⫻ 73 was dispensed. In the second case the left and right lenses had been reversed. In the third case a cylinder axis was off by 10 degrees. In addition, one child had been dispensed adult-sized frames, and another had inaccurate optical centers, inducing prism. Discussion: Since spectacles are often prescribed as medical treatment for amblyopia and/or strabismus in the pediatric population, incorrect spectacle lenses may contribute to permanent vision loss. Young children are often unable to express that their spectacles are incorrect. Conclusion: The rate of serious error in dispensing children’s spectacle lenses is fairly low, but can be disastrous if it occurs. We recommend that nonverbal children’s spectacles be measured shortly after dispensing, and at every clinic visit, to ensure that what we think they are wearing is actually the case. Conjunctival Amelanotic Melanoma in a Teenager Patrick J. Droste MD; DeVos Children’s Hospital/Spectrum Health, Grand Rapids, MI Introduction: Conjunctival neoplasms in children are rare. Methods: A 13-year-old white female presented with a benignappearing neoplasm of the medial conjuctiva of the left eye. A 3-week course of topical steroid resulted in no clinical improvement. The child was scheduled for conjunctival excision and biopsy. Results: Conjunctival biopsy revealed the presence of malignant melanoma with minimal pigmentation. Further treatment included wide excision with cryotherapy and sentinel node biopsy. Two-year follow-up has revealed no occurrence. Discussion: Benign-appearing lesions may not be benign. Conclusions: Conjunctival lesions that do not respond to anti-inflammatory treatment should be considered for wide excision biopsy. Malignant conjunctival lesions should be treated with cryotherapy and sentinel node biopsy to rule out metastatic disease.
Abstracts
How To Measure Slab-Off and Reverse Slab-Off Spectacle Lenses Alexander Christoff CO, COT, David L. Guyton MD; Wilmer Eye Institute at Johns Hopkins Hospital, Baltimore, MD Vertical diplopia while reading can occur when glasses are made for an anisometropic individual. The difference in the powers of the lenses induces a prismatic difference that can cause double vision in off-center areas of the lenses when patients try to read through anisometropic corrections. This induced prismatic effect can be compensated at one level of downgaze by the use of slab-off or reverse slab-off prism, where typically the slab-off correction is ground into the stronger minus, or weaker plus, lens. Slab-off lenses can also be used for patients who demonstrate vertical strabismus at near fixation only, or where the magnitude of the vertical deviation is worse at near versus at distance. Unfortunately, determining the amount of slab-off prism already incorporated into spectacle lenses is nonintuitive and inconvenient, usually requiring the use of a lens clock, not widely accessible to many ophthalmology practices. A simple technique, described in the past but poorly known, is illustrated for quickly measuring slab-off and reverse slab-off prism prescription lenses in the clinic with a common manual lensmeter. Assessment of Magnocellular and Parvocellular Pathways in Early- versus Late-Onset Amblyopes Using Motion and Color VEP Alison R. Davis, Madgella N. Neveu, Chris R. Hogg, Michael J. Morgan, Graham E. Holder, John J. Sloper; Moorfields Eye Hospital, London, UK Aim: Studies in nonhuman primates indicate that monocular visual deprivation starting at different ages has different effects on the parvocellular and magnocellular pathways. We examined whether subjects with strabismic amblyopia of onset before (early) or after 18 months (late) of age have different electrophysiological responses to motion onset and color appearance stimuli. Method: Motion onset VEPs were recorded in 15 early and 12 late onset strabismic amblyopes and 19 normal subjects using an achromatic 0.8-cpd vertical square wave grating. There was no difference in mean Log MAR acuities between the early- and late-onset amblyopes. Color VEPs were recorded in 14 early- and 13 late-onset strabismic amblyopes and 17 normal subjects using a 3.2-cpd equiluminant red/green pattern onset sine-wave grating. Between-eye comparisons were made using paired t-tests and between-group comparisons were made using unpaired t-tests. Results: Motion onset VEP latencies were shortened in amblyopic (171.0 ⫾ 12.4 ms; P ⫽ 0.041) and fellow eyes (167.6 ⫾ 10.7 ms; P ⫽ 0.001) of all amblyopes compared to normal (178.1 ⫾ 9.5 ms). The latencies from amblyopic eyes were significantly longer than those from fellow eyes (P ⫽ 0.024). There was little difference between earlyand late-onset amblyopes. Color VEP latencies in the amblyopic eyes of late onset amblyopes (149.9 ⫾ 25.3 ms) were significantly longer than normal (125.2 ⫾ 11.3 ms; P ⫽ 0.001) and fellow eyes (131.7 ⫾ 13.8; P ⫽ 0.024). In early-onset amblyopes there was no significant difference between amblyopic (131.0 ⫾ 22.1 ms) and fellow eyes (132.3 ⫾ 15.6) nor either eye and normal. The difference in latency between early- and late-onset amblyopic eyes was significant (P ⫽ 0.048). Conclusions: These results suggest different changes in magnocellular and parvocellular function in both amblyopic and fellow eyes between early- and late-onset strabismic amblyopes.
Journal of AAPOS Volume 10 Number 1 February 2006 How Often Are Our Patients’ Spectacle Lenses Dispensed as Prescribed? Arlene V. Drack MD, Rebecca Sands MD, Colleen Smith COT, Ted Curtis MD, Cameile Moore CO, Cathy O’Donnell COA; University of Colorado, Aurora, CO Introduction: Our purpose was to determine the frequency of inaccurate glasses prescriptions being dispensed to our patients. Methods: Chart review from 11 outpatient clinic sessions for three pediatric ophthalmologists. Spectacle prescriptions written were compared to actual prescription measured at next visit. Differences of ⱖ0.50 D sphere or cylinder, and ⬎5 degrees in cylinder axis, were considered inaccurate. Differences of ⬎1 D sphere/cylinder, or ⱖ10 degrees in cylinder axis, were considered potentially amblyogenic. Results: Seventy-nine charts were identified in which patients had been prescribed glasses and had the lenses measured on return visit. Twenty-five percent were inaccurate according to our criteria. Three of 79 (3.8%) were potentially amblyogenic. In one case ⫹13.50 was prescribed and ⫺14.50 ⫹ 0.75 ⫻ 73 was dispensed. In the second case the left and right lenses had been reversed. In the third case a cylinder axis was off by 10 degrees. In addition, one child had been dispensed adult-sized frames, and another had inaccurate optical centers, inducing prism. Discussion: Since spectacles are often prescribed as medical treatment for amblyopia and/or strabismus in the pediatric population, incorrect spectacle lenses may contribute to permanent vision loss. Young children are often unable to express that their spectacles are incorrect. Conclusion: The rate of serious error in dispensing children’s spectacle lenses is fairly low, but can be disastrous if it occurs. We recommend that nonverbal children’s spectacles be measured shortly after dispensing, and at every clinic visit, to ensure that what we think they are wearing is actually the case. Conjunctival Amelanotic Melanoma in a Teenager Patrick J. Droste MD; DeVos Children’s Hospital/Spectrum Health, Grand Rapids, MI Introduction: Conjunctival neoplasms in children are rare. Methods: A 13-year-old white female presented with a benignappearing neoplasm of the medial conjuctiva of the left eye. A 3-week course of topical steroid resulted in no clinical improvement. The child was scheduled for conjunctival excision and biopsy. Results: Conjunctival biopsy revealed the presence of malignant melanoma with minimal pigmentation. Further treatment included wide excision with cryotherapy and sentinel node biopsy. Two-year follow-up has revealed no occurrence. Discussion: Benign-appearing lesions may not be benign. Conclusions: Conjunctival lesions that do not respond to anti-inflammatory treatment should be considered for wide excision biopsy. Malignant conjunctival lesions should be treated with cryotherapy and sentinel node biopsy to rule out metastatic disease.