Macular Degeneration: Mainster MA

Mainster MA, Turner PL. · No affiliation provided · Am J Ophthalmol. · Pubmed #19100352 No free full text.

This publication has no abstract.

Mainster MA. · Department of Ophthalmology, University of Kansas Medical Center, Kansas City, KS 66160-7379, USA. · Arch Ophthalmol. · Pubmed #15824232 No free full text.

This publication has no abstract.

Mainster MA, Reichel E. · Department of Ophthalmology, University of Kansas Medical Center, 3907 Rainbow Boulevard, Kansas City, KS 66160-7379, USA. · Semin Ophthalmol. · Pubmed #15491004 No free full text.

Abstract: Transpupillary thermotherapy (TTT) is a subthreshold, low irradiance, long exposure duration, large spot size, infrared diode laser protocol. Retinal temperature increases in TTT for choroidal neovascularization (CNV) are substantially lower than those in conventional short-pulse photocoagulation, but they are maintained for 60 seconds to achieve therapeutic results. Treatment power is adjusted for retinal lesion size, chorioretinal pigmentation, macular elevation and media clarity. TTT uses 810-nm diode laser infrared radiation, which has no significant retinal phototoxicity. A parfocal laser delivery system is required to assure uniformity of irradiance across large diameter treatment spots. Relative contraindications for TTT include dense subretinal hemorrhage, prior focal photocoagulation and serous RPE detachment. Adverse events are rare, and include decreased vision and retinal arteriole occlusion. Randomized, prospective multi-center trials are underway to compare the results of TTT for occult CNV in age-related macular degeneration to the natural history of the disorder. Imaging, electrophysiologic or thermometric techniques may ultimately provide intra-operative or post-operative monitoring to assure the adequacy of TTT for CNV, despite the absence of ophthalmoscopically visible lesions.

Mainster MA, Reichel E. · Department of Ophthalmology, University of Kansas Medical Center, Kansas City 66160-7379, USA. · Ophthalmic Surg Lasers. · Pubmed #11011704 No free full text.

Abstract: OBJECTIVE: To provide a biophysical foundation for using transpupillary thermotherapy (TTT) to manage choroidal neovascularization in age-related macular degeneration (ARMD). METHODS: Retinal temperature rise in laser therapy is proportional to retinal irradiance (laser power/area) for a particular spot size, exposure duration, and wavelength. TTT is a low irradiance, large spot size, prolonged exposure (long-pulse), infrared laser photocoagulation protocol. Results from an experimentally confirmed, finite element model of retinal light absorption and heat conduction are used to analyze laser parameter selection and its consequences. Results from apoptosis, heat shock protein and hyperthermia research are used to examine how chorioretinal damage from clinical procedures might be reduced. RESULTS: Chorioretinal thermal equilibration occurs during long-pulse TTT photocoagulation. Retinal temperature increases are similar in the RPE where laser radiation absorption is significant and in the adjacent neural retina where there is negligible radiation absorption. For parameters used to treat occult choroidal neovascularization in lightly-pigmented fundi (800-mW, 810-nm, 3-mm retinal spot diameter, 60-sec exposure duration), the maximum chorioretinal temperature elevation is calculated to be roughly 10 degrees C, significantly lower than the 20 degrees C temperature elevations measured in threshold, conventional short-pulse retinal photocoagulation. CONCLUSIONS: To achieve a preselected temperature rise, TTT laser power must be increased or decreased in proportion to the diameter rather than the area of the laser spot. Clinical power settings should be adjusted for fundus pigmentation and media clarity because both of these factors affect absorbed retinal irradiance and thus retinal temperature rise. Noninvasive thermal dosimetry currently is unavailable for clinical retinal photocoagulation, but potential thermometric techniques include MRI, liposomal-encapsulated dyes, multispectral imaging or reflectometry, and subretinal or episcleral thermometry. TTT may be useful not only as independent therapy, but also as an adjunct to PDT, antiangiogenic drugs and ionizing radiation therapy in the management of neovascular ARMD. Low temperature, long-pulse photocoagulation is a potential strategy for decreasing neural retinal damage in subsequent TTT or short-pulse photocoagulation and perhaps even for treating glaucoma or retinal degenerations.

Mainster MA. · PhD, MD, FRCOphth, Department of Ophthalmology, MS3009, University of Kansas Medical School, 3901 Rainbow Boulevard, Kansas City, KS 66160-7379, USA. · Br J Ophthalmol. · Pubmed #16714268 links to  free full text

Abstract: AIM: To analyse how intraocular lens (IOL) chromophores affect retinal photoprotection and the sensitivity of scotopic vision, melanopsin photoreception, and melatonin suppression. METHODS: Transmittance spectra of IOLs, high pass spectral filters, human crystalline lenses, and sunglasses are used with spectral data for acute ultraviolet (UV)-blue photic retinopathy ("blue light hazard" phototoxicity), aphakic scotopic luminous efficiency, melanopsin sensitivity, and melatonin suppression to compute the effect of spectral filters on retinal photoprotection, scotopic sensitivity, and circadian photoentrainment. RESULTS: Retinal photoprotection increases and photoreception decreases as high pass filters progressively attenuate additional short wavelength light. Violet blocking IOLs reduce retinal exposure to UV (200-400 nm) radiation and violet (400-440 nm) light. Blue blocking IOLs attenuate blue (440-500 nm) and shorter wavelength optical radiation. Blue blocking IOLs theoretically provide better photoprotection but worse photoreception than conventional UV only blocking IOLs. Violet blocking IOLs offer similar UV-blue photoprotection but better scotopic and melanopsin photoreception than blue blocking IOLs. Sunglasses provide roughly 50% more UV-blue photoprotection than either violet or blue blocking IOLs. CONCLUSIONS: Action spectra for most retinal photosensitisers increase or peak in the violet part of the spectrum. Melanopsin, melatonin suppression, and rhodopsin sensitivities are all maximal in the blue part of the spectrum. Scotopic sensitivity and circadian photoentrainment decline with ageing. UV blocking IOLs provide older adults with the best possible rhodopsin and melanopsin sensitivity. Blue and violet blocking IOLs provide less photoprotection than middle aged crystalline lenses, which do not prevent age related macular degeneration (AMD). Thus, pseudophakes should wear sunglasses in bright environments if the unproved phototoxicity-AMD hypothesis is valid.

Luttrull JK, Musch DC, Mainster MA. · Private Practice, 3160 Telegraph Road, Suite 230, Ventura, CA, 93003, USA. · Br J Ophthalmol. · Pubmed #15615751 links to  free full text

Abstract: AIM: To report the visual and clinical outcomes of a pilot study of subthreshold diode micropulse (SDM) laser photocoagulation for clinically significant diabetic macular oedema (CSMO). METHODS: The results of infrared (810 nm) SDM laser photocoagulation for CSMO were retrospectively reviewed in 95 eyes of 69 consecutive patients with mild to moderate non-proliferative diabetic retinopathy. The same laser parameters were used for each patient. Only the number of laser applications varied between patients, depending on their macular findings. Primary outcome measures were Snellen visual acuity, fluorescein angiographic leakage, and CSMO status. RESULTS: Visual acuity was stable or improved in 85% of treated eyes, with a mean follow up of 12.2 months (range 3-29 months). CSMO decreased in 96% and resolved in 79% of treated eyes. No adverse laser events occurred. No laser lesions were detectable ophthalmoscopically or angiographically after treatment, consistent with calculations based on ANSI Z136.1 laser safety standards suggestive of only histologically detectable tissue effects at the laser exposure levels. No laser scarring was observed during the follow up period. CONCLUSION: Subthreshold diode micropulse laser photocoagulation minimises chorioretinal damage in the management of CSMO and demonstrates a beneficial effect on visual acuity and CSMO resolution. Prospective studies are needed to fully evaluate this technique.

Mainster MA, Friberg TR. · Department of Ophthalmology, University of Kansas Medical Center, 3907 Rainbow Boulevard, Kansas City, KS 66160-7379, USA. · Semin Ophthalmol. · Pubmed #15491003 No free full text.

This publication has no abstract.

Ibarra MS, Hsu J, Mirza N, Wu IH, Ying GS, Mainster MA, Tolentino MJ. · Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. · Invest Ophthalmol Vis Sci. · Pubmed #15452076 links to  free full text

Abstract: PURPOSE: To study the risk of adverse events in transpupillary thermotherapy (TTT) for age-related macular degeneration by measuring how laser-induced retinal temperature increase is affected experimentally by subretinal blood, choroidal blood flow, and chorioretinal pigmentation. METHODS: An ultrafine thermocouple technique was developed to measure retinal temperature increase during TTT in albino and pigmented rabbit eyes. TTT was performed with 60-second, 0.78-mm spot size, 810-nm infrared diode laser exposures with power settings ranging from 50 to 950 mW. Intraretinal and subretinal temperature increases were measured in pigmented and albino rabbits, with or without subretinal blood and choroidal blood flow. RESULTS: Threshold power settings for visible lesions in albino and pigmented rabbits were 950 and 90 mW, respectively, corresponding to retinal temperature increases of 11.8 degrees C and 5.28 degrees C, respectively. Power settings required to produce threshold lesions in albino rabbits caused retinal temperature increases in pigmented rabbits that were five times higher than in the albino rabbits. Temperature increases in albino rabbits were 1.5 times higher with subretinal blood than without it. Choroidal blood flow generally did not affect measured retinal temperature increases. CONCLUSIONS: The results confirm prior theoretical recommendations that clinicians should consider decreasing TTT power settings in darkly pigmented eyes and proceed with caution in those with subretinal hemorrhage or pigment clumping.

Falsini B, Focosi F, Molle F, Manganelli C, Iarossi G, Fadda A, Dorin G, Mainster MA. · Institute of Ophthalmology, Catholic University of S Cuore, Rome, Italy. · Invest Ophthalmol Vis Sci. · Pubmed #12714653 links to  free full text

Abstract: PURPOSE: To use focal electroretinography to evaluate changes in retinal function during transpupillary thermotherapy (TTT) for neovascular age-related macular degeneration (ARMD). METHODS: Sixteen eyes of 16 patients with ARMD with occult choroidal neovascularization (CNV) were studied. A 630-nm photocoagulator aiming beam was modified for use as a 41-Hz square-wave focal electroretinogram (fERG) stimulus. The stimulus was presented on a light-adapting background by a Goldmann-type lens (visual angle, 18 degrees; mean luminance, 50 cd/m(2)). fERGs were continuously monitored before, during, and after TTT for occult CNV. The amplitude and phase of the fERG's fundamental harmonic were measured. RESULTS: No suprathreshold or adverse clinical events occurred during the course of the study. fERG amplitude decreased transiently during TTT (23% +/- 9% [SE]; P < 0.05). The decrease in amplitude was greatest 16 to 20 seconds and 32 to 40 seconds after the onset of TTT. It was followed by a recovery to baseline amplitude during TTT (48 to 60 seconds after TTT was begun). Within 60 seconds after TTT was completed, fERG amplitude was within the range of baseline. TTT did not alter the fERG phase. Mean fERG amplitudes and phases recorded 1 week and 1 month after TTT were comparable to mean pretreatment levels. CONCLUSIONS: fERG amplitude decreases transiently during TTT, despite the absence of ophthalmoscopically apparent lesions. Intraoperative amplitude depression may result from an adaptation effect to laser light energy and/or hyperthermia, resulting in desensitization of cone photoreceptors and bipolar cells. Treatment sites are electrophysiologically functional 1 month after TTT. Detailed parametric study of a larger patient group is needed to determine whether fERG testing is potentially useful for monitoring and perhaps for controlling and optimizing TTT for choroidal neovascularization.