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LETTER TO EDITOR
Year : 2004  |  Volume : 52  |  Issue : 1  |  Page : 86-87

Transpupillary thermo therapy for the treatment of choroidal neovascula-risation secondary to age related macular degeneration in Indian eyes.



Correspondence Address:
L Verma


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Source of Support: None, Conflict of Interest: None


PMID: 15132395

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How to cite this article:
Verma L, Sinha A, Nainiwal S, Tewari HK. Transpupillary thermo therapy for the treatment of choroidal neovascula-risation secondary to age related macular degeneration in Indian eyes. Indian J Ophthalmol 2004;52:86-7

How to cite this URL:
Verma L, Sinha A, Nainiwal S, Tewari HK. Transpupillary thermo therapy for the treatment of choroidal neovascula-risation secondary to age related macular degeneration in Indian eyes. Indian J Ophthalmol [serial online] 2004 [cited 2019 Aug 26];52:86-7. Available from: http://www.ijo.in/text.asp?2004/52/1/86/14616

Dear Editor,

We read with interest the article on "Transpupillary thermo therapy for the treatment of choroidal neovascularisation secondary to age-related macular degeneration in Indian eyes" by Nagpal et al. We congratulate the authors for the same

We have been doing transpupillary thermo therapy (TTT) for neovascular age-related macular degeneration (AMD) since September 2000. We agree with the authors that overall, the results of TTT are encouraging. In a study on 50 eyes of patients of subfoveal choraidal neovascularisation (CNV), we found that the letter acuity stabilised or improved (a shift of one line on ETDRS chart) in 72% of eyes (P<0.05) at 12 weeks' follow-up and reading speed improved from a mean of 27.04 words/minute to 37.33 words/minute at 12 weeks. Further, TTT works better in occult CNV.

We further agree that the power settings for the Indian pigmented eyes are significantly lower than recommended in the literature for Caucasian eyes. At our centre we have been using power settings of 200 -300 mW, 350 - 450 mW and 400 - 550 mW for 1.2, 2.0 and 3.0 mm spot size using a quadraspheric lens.

The power to be delivered needs to be individualised. We would like to supplement certain points which are of importance while deciding on the power for a particular patient. Besides fundus pigmentation, these include media clarity, squeezing by the patient, pressure exerted by the contact lens (this tends to enhance the effect of TTT by decreasing choroidal blood flow and decreasing the dissipation of heat thus increasing the local temperature and the effect of TTT), wear and tear of the fiber-optic cable, coating, tilting and focus of the contact lens, age of the patient, haemorrhage, exudation and elevation of the lesion.

Giving a test spot outside the arcades may not always indicate the power setting to be used. We feel this is because one cannot always extrapolate the reaction seen on a normal retina to an abnormal area of retina. At times no reaction may be seen even with power setting of 1200 mW on normal retina.

The authors have used two spots of 3mm size when the lesion was not fully covered with the spot size; here we suggest that when the spot does not cover the entire membrane and one is using Goldman's lens for laser delivery, use of two adjacent spots leads to undertreatment of the triangles which are above and below the overall spot. This could lead to recurrence or persistence of the lesion. We would recommend one to use quadraspheric lens which magnifies the spot by 2.06 times thus necessitating only one spot. The other strategy should be to use overlapping spots in such a way that the entire lesion is covered and the centre that is overtreated should not lie on the centre of the foveal avascular zone.

In the study, the authors have used Snellen's visual acuity chart to document visual acuity. In our view, ETDRS charts would be preferable for documentation of visual function. The letters which have near equal difficulty score are used in making the ETDRS chart, and all the lines hence have almost equal difficulty scores. Moreover, as one moves down the chart, the visual angle doubles at every third line. This is not so in case of Snellen's acuity charts.

Another point worth noting is that juxtafoveal lesion so far has been treated according to the MPS recommendation. Juxtafoveal lesions which are close to the fovea and are treated with thermal laser photocoagulation fare no better than the natural history.[2] In the era of TTT and PDT, such lesions should be treated with these newer modalities to prevent immediate reduction of visual acuity. We have treated 22 eyes of 22 patients with fluorescein angiographic evidence of juxtafoveal CNV (14 secondary to AMD and 8 eyes with idiopathic CNV). In a mean follow up of 24.6 weeks in the AMD group, the visual acuity improved or stabilised in 78.57% eyes (n = 14) at 3 months, 57.24% eyes (n = 7) at 6 months, 50% eyes (n = 4) at 9 months and 50% eyes (n = 2) at 1 year follow up. In a mean follow-up of 32.5 weeks in the idiopathic group, visual acuity improved or stabilised in 87.5% (n =8) eyes at 3 months, 71.42% (n =7) eyes at 6 months and none of eyes at 9 months and 1 year. Hence juxtafoveal CNVs are better dealt with non thermal lasers rather than thermal (Transpupillary Thermo Therapy as an alternative treatment of Juxtafoveal Choroidal Neovascular membranes in pigmented Eyes. 3rd EURETINA Congress, May 15 - 17, Hamburg, Germany).

Once again we congratulate the authors for sharing their experiences of the use of TTT in subfoveal choroidal neovascular membranes.



 
  References Top

1.
Nagpal M, Nagpal K, Sharma S, Puri J, Nagpal PN: Transpupillary Thermo Therapy for the treatment of choroidal neovascularization secondary to age related macular degeneration in Indian eyes. Indian J Ophthalmol 2003; 51: 243 - 50.  Back to cited text no. 1
    
2.
Lee MJ, Lance S: Treatment of juxtafoveal and extrafoveal Choroidal Neovascularization in the era of photodynamic therapy with Verteporfin. Am J Ophthalmol 2002:134, 99-101.  Back to cited text no. 2
    




 

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