Friday, December 30, 2005

DOES XALATAN REMAIN STABLE AFTER 4-6 WEEKS AT ROOM TEMPERATURE?


Investigative Ophthalmology and Visual Science. 2006;47:222-225.

According to this study, after 4-6 weeks of Xalatan use:
"Ninety-four percent of the bottles had concentrations within 90% to 110% of the labeled amount. No difference in latanoprost concentrations was found between the bottles used for 4 weeks versus those used for 6 weeks.

"CONCLUSIONS. In an eye clinic setting, latanoprost ophthalmic solution 0.005% remains stable after 4 or 6 weeks of patient use from the same bottle when stored at room temperature."

Although we've known this for some time, this is another study that enables us to confidently advise patients they don't need to store Xalatan in the refrigerator. Now I'd like to know what happens to Xalatan when it is left in a hot car in the middle of summer in Arizona.

Thursday, December 29, 2005

ARE ANTIOXIDANTS BENEFICIAL TO PREVENT AMD?


JAMA -- Abstract: Dietary Intake of Antioxidants and Risk of Age-Related Macular Degeneration, December 28, 2005, van Leeuwen et al. 294 (24): 3101

We have known that antioxidants are useful in slowing disease progression in those who have already been diagnosed with AMD, but it was not known if antioxidants reduced the risk of developing AMD in the first place.

This study concludes:
"a high dietary intake of beta carotene, vitamins C and E, and zinc was associated with a substantially reduced risk of AMD in elderly persons."

So perhaps we can counsel patients concerned about AMD (perhaps those with a family history of AMD) that antioxidants may be worth taking even if they have not developed signs of it.

CORNEA TOO THIN FOR LASIK? LASER THE FLAP UNDERSIDE


According to this study: (ScienceDirect - Journal of Cataract & Refractive Surgery : Simultaneous laser in situ keratomileusis on the stromal bed and undersurface of the flap in eyes with high myopia and thin corneas) if the cornea is too thin to perform LASIK on highly myopic eyes, the underside of the flap can be lasered as well as a portion of the stromal bed. I wonder if a center mark is placed on the cornea before the flap is made so the surgeon can make sure the laser is centered properly. This would be interesting to watch. About 80% of patients obtained 20/30 or better post-operatively. The conclusion of the study was
"Simultaneous LASIK appears to be a useful surgical aid in LASIK treatment in eyes with high myopia with or without astigmatism when an adequate residual stromal bed does not exist."

Mucin balls with silicone hydrogel contact lenses


"Clinical Significance of Mucin Balls"

According to this study mucin balls on silicone hydrogel lenses are somewhat common and resemble "dimple veiling" seen with rigid gas permeable contact lenses.
This article gives tips on how to differentiate your clinical findings.

Tuesday, December 27, 2005

LASIK SAFE IN WELL CONTROLLED DIABETES

Journal of Cataract & Refractive Surgery
Volume 31, Issue 10 , October 2005, Pages 1895-1898


According to this study,
"Laser in situ keratomileusis surgery was safely performed in patients with well-controlled diabetes. Enhancement may often be required for optimal correction."

TONOMETRY CALIBRATION ERRORS

SOURCE: Sandhu SS, Chattopadhyay S, Birch MK, Ray-Chaudhuri N. Frequency of Goldmann applanation tonometer calibration error checks. J Glaucoma 2005;14(3):215-8.

According to this study,
"Calibration error checks should be carried out monthly and tonometers with calibration error greater than +/- 2.5 mmHg returned to the manufacturer for re-calibration."

Does anyone know how to calibrate the Goldmann Tonometer? This is not something I've ever thought about, and yet we have so many glaucoma patients where 1 or 2 mmHg makes a difference in making clinical decisions. This sounds like a question for the manufacturer. If anyone knows anything about this please comment.

ERRONEOUS CORRECTING OF IOP FOR CORNEAL THICKNESS

Gunvant P, O'Leary DJ, Baskaran M, et al. Evaluation of tonometric correction factors. J Glaucoma. 2005;14(5):337-43. This study investigated the efficacy of currently available correction factors in correcting intraocular pressure (IOP) measurements for central corneal thickness variations. It states that
"the Ehlers and Orssengo and Pye models may significantly overestimate the effect of CCT on IOP measurement. Correcting IOP for the effect of CCT using these models could be erroneous and lead to overcorrection of IOP. This could result in erroneously low corrected IOP in eyes with thicker cornea and erroneously high corrected IOP in eyes with thinner cornea."

This is yet another study that demonstrates that we should be determining risk level for glaucoma using CCT and IOP separately, but not together in a "corrected IOP". Using a corrected IOP seems to be common sense, but no study demonstrates it's usefulness. I think I'll continue to treat CCT and IOP as separate risk factors, as demonstrated by the OHTS study.

EPIRETINAL MEMBRANE REMOVAL IN EYES WITH GOOD VISUAL ACUITIES.

According to this study:
"Vitrectomy for epiretinal membranes is safe in eyes with relatively good preoperative visual acuities (20/30 to 20/50) but cataract surgery is necessary in phakic eyes to achieve long-term visual acuity improvement."


Maybe we can refer earlier than we have in the past.

Monday, December 26, 2005

Visual Acuity Mortality Risk Factor


According to this study, decreased visual acuity increases the risk of mortality in elderly. They study states:
"Worse acuity was associated with a higher mortality rate. Also, those who gained two or more lines of visual acuity over 2 years had a lower risk of dying. Women who lost 3 lines of visual acuity over a 2-year period had a higher risk of dying, whereas men did not. Depressive symptoms did not mediate these relationships."

Not to put any pressure on anybody.

Friday, December 23, 2005

IT MAKES IT ALL WORTH IT


I made a patient's wife cry today. Let me explain. This gentleman in his 50's hasn't seen 20/20 in years. He's had Fuch's dystrophy that required PKP in the right eye 3 years ago. His resultant cornea has 6 diopters of astigmatism. I ordered a contact lens for him last week. They came in and with the contact lens in his eye he's seeing 20/20! His wife cried. I almost cried too because ordinarily my post-PKP contact lenses are a disaster.

But I got a little teary eyed because it has been years of Fuch's dystrophy, and 3 years of post-op PK, and now for the 1st time since he was in his 30's, he's seeing 20/20. It makes it all worth it!

TRABECULECTOMY IMPROVES COLOR VISION



According to this study "Intraocular pressure reduction of ≥ 20% post-trabeculectomy was associated with an improvement in colour vision. Colour vision tests may be useful as an adjunctive outcome measure for therapeutic interventions."

Is this because with decreased pressure the optic nerve is more perfused? I spoke to our glaucoma specialist about this study and he said he'd welcome color deficiencies as an indication for trabeculectomy. Yea...he'd like that.

CATARACT SURGERY AND REFRACTIVE EXPECTATIONS

According to this study "Patients who already wear spectacles expect to need them after cataract surgery. Those not already wearing spectacles do not expect to need them. This latter group is at particular risk for refractive disappointment and complaint."

Seems like a no brainer, but I guess we shouldn't be surprised when a patient didn't need glasses before cataract surgery and now needs them.

Thursday, December 22, 2005

DIMPLE VEILING ON NIGHT & DAY CL?


I've got a gentleman who's worn Acuvue's EW for years with not problems except the usual pannus and redness. So I switched him to Night and Day's. He's using "Blink" Lubricant Eye Drops.

He comes into today with no visual complaints, but when I look in his eye, he has a ton of dimple veiling. What's up with that?

I'm going to try switching the drops to something else...but that's not something I've seen before in soft lenses. Maybe it's a fitting problem. Any thoughts?

STATE ASSOCIATION FEES


$1416.00! Ouch! I'm half tempted not to do it this year. Somebody ease my pain by reminding me of the benefits of belonging to the association.

WATER DRINKING TEST AND GLAUCOMA


Has anybody ever done the "water drinking test" to determine the peak of the diurnal IOP curve? According to the theory: "Fluctuations of IOP in glaucomatous patients can be induced by the osmotic variations caused by water ingestion. Such influence can be studied by means of the water-drinking test (WDT)" (J Ocul Pharmacol Ther. 2005 Jun;21(3):250-7.).

Here's how it's done: The patient drinks 4 cups of water in 10 minutes and the IOP is measured every 15 minutes until the pressure returns to baseline levels. On the chart you record the peak IOP, the percentage increase, and how long it takes to return to baseline.

According to one recent study, the higher the peak IOP and percentage change of IOP during the water drinking test, the greater the progression of visual field loss).

The first mentioned study above says that patients on Timolol, Trusopt, and Azopt reach a higher peak IOP and shorter return to normal than patients taking the prostaglandin analogues and Alphagan-P (the former affect aqueous production and the latter affect outflow). This would suggest Lumigan and Alphagan-P is better to decrease diurnal variations.

Is the water drinking test useful to us at all in the clinic? All I can say is, the bathroom better be nearby and unoccupied!


Dr. Kevin

Wednesday, December 21, 2005

Move over, I'm coming on board.

I read from a few blogs in the past but have no experience myself. However, I am anxious to learn. I think this is a great idea. Thanks Kevin for taking the initiative.

CRYSTALENS AND POST-OP DILATING


I was able to ask Dr. Mike today about Crystalens and dilating. He said he (and Eyeonics) stopped requiring the prolonged dilating period because of patient complaints of blurred vision. He did say that outcome was slightly more predictable for those patients that endured the prolonged post-operative dilation, even to the point that he considers going back to that regimen. But I've seen great results in those that didn't follow the dilating regimen. Sounds like a good study should be done! The jury is still out. Any thoughts?

Tuesday, December 20, 2005

AR COAT DECREASES POLYCARBONATE STRENGTH


This is so strange. Here's the conclusion from this recent study:

"applying a MAR coating further reduces the penetration resistance. Therefore, the use of 2-mm center thickness and anti-reflective coated polycarbonate lenses should be discouraged for industrial eye protectors where sharp missile hazards are possible."

Optometry & Vision Science. 82(11):964-969, November 2005.

Monday, December 19, 2005

IOP-LOWERING DEVICE WITHOUT BLEB

The FDA has granted an Investigational Device Exemption (IDE) approval to SOLX, Inc. to begin studies of the DeepLight Gold Micro-Shunt (GMS) implant for glaucoma. The GMS is a 24-karat gold, ultra-thin, flat plate designed for implantation through a single micro-incision. It contains micro-tubular channels that bridge the anterior chamber and suprachoroidal space, maximizing uveoscleral outflow to reduce IOP. The GMS rests permanently in the suprachoroidal space and cannot be felt by the patient. It is biocompatible and physically inert, and it has been shown to eliminate the formation of scar tissue. Multicenter studies of 70 eyes with up to two years follow-up in Spain and Israel demonstrated excellent clinical results. The randomized, multicenter study will evaluate safety and efficacy of the GMS for lowering intraocular pressure (IOP) in patients with primary open-angle glaucoma. who have failed maximum medical therapy and at least one surgical intervention.

Welcome Dr. Ken

Dr. Ken has joined me in this endeavor and I welcome him. We expect many profound, if not humorous insights from the Elvis Loving Dr. Ken.

Sunday, December 18, 2005

Intraocular Pressure After LASIK Surgery


After LASIK, IOP is reduced from 16.5 +/- 2.1 to 12.9 +/- 1.9 mmHg. There is a significant correlation between IOP and corneal curvature as well as corneal thickness.

Pressure measurements after LASIK are inaccurate because of a change in corneal biomechanics, corneal thickness and curvature and they should be corrected as follows: IOP (real) = IOP (measured) + (540 - CCT)/71 + (43 - K-value)/2.7 + 0.75 mmHg.

SOURCE: Kohlhaas M, Sporl E, Bohm AG, et al. Applanation tonometry in 'normal' patients and patients after LASIK. Klin Monatsbl Augenheilkd. 2005;222(10):823-6.

DR KEVIN: Someday soon I'll take the formula above and take the formula for determining how much the corneal thickness is reduced per diopter corrected and maybe come up with an Reduced IOP/Diopter Corrected formula. Seems like it should be a simple calculation.

Is Homelessness a Risk Factor for Eye Disease?

This study revealed an unexpectedly high prevalence of optic nerve atrophy in homeless people. The prevalence for cataract and legal blindness was slightly higher than in representative epidemiological investigations. Homelessness seems to be correlated with an increased ocular morbidity.

SOURCE: Pitz S, Kramann C, Krummenauer F, et al. Is homelessness a risk factor for eye disease? Ophthalmologica. 2005;219(6):345-9.

DR. KEVIN'S COMMENTS:

Why would homelessness and optic atrophy be correlated? Could it possibly be because of nutritional deficiency? Interesting study.

Effect of Artificial Tears on Visual Acuity

Conclusions
Refresh Plus Eye Drops provides a temporary yet significant improvement in the visual acuity of dry eye patients. The effect of artificial tears on visual acuity may be of diagnostic value in detecting ocular surface abnormality in symptomatic and asymptomatic patients.

ScienceDirect - American Journal of Ophthalmology : Effect of Artificial Tears on Visual Acuity

DR KEVIN'S COMMENTS:

How about those late afternoon refractions that seem to fluctuate so much because of dryness? I wonder if using Refresh Plus before refraction might help in these dry eye patients? I'll have to try it this week.

Acuvue Oasys Lenses Supposed to be More Comfortable


VISTAKON-SPONSORED STUDY SUGGESTS SENOFILCON MATERIAL MAY HELP REDUCE COMMON PROBLEMS.


A recent study showed that lenses made with senofilcon A, a new silicone hydrogel material currently marketed in the United States as Acuvue Oasys contact lenses with Hydraclear Plus, were associated with a reduction in discomfort, dryness and other commonly reported problems associated with contact lens wear. Results of the study, which was sponsored by Vistakon, were published in Optometry and Vision Science and presented at the AAO annual meeting. Researchers evaluated clinical data from 1,092 current soft contact lens wearers to calculate the prevalence of six common signs and symptoms associated with contact lens discomfort. Nearly half (48 percent) showed at least one of the six criteria. Uncomfortable hours of wear at the end of the day (31 percent) was the most commonly reported problem, followed by frequent or constant dryness (28 percent) and discomfort (17 percent). Following the evaluation, 257 wearers were fit with senofilcon A lenses and reassessed two weeks later. Among subjects who reported problems before refitting, 88 percent said they noticed improvement in overall comfort, 76 percent in comfortable hours of wear and 75 percent in frequency of dryness.

DR. KEVIN'S COMMENTS:

Of course the study was sponsored by Vistakon so I have to be careful about this. I haven't been fitting these yet but I certainly will begin to based on these data. I fit primarily the Biomedics 55 Premier lens for comfort, the Proclear Compatibles for dryness, and Ciba Night and Day contact lenses for extended wear. I haven't gotten back to the B&L Purevision contact lenses yet, but before they were outlawed several years ago, I recall them being more comfortable than Night and Day. So I'll probably go back to them soon. I am excited about the Purevision Toric lenses coming out in January. This will allow me to fit toric lenses extended wear. I hope they work! Maybe I'll try this Acuvue Oasys lens. Since we're a medical practice, I don't get as many contact lens fits as more commercial settings, so the reps ignore me a little, especially from Vistakon. I'll have to track the rep down.

Half of Glaucoma Patients Soon Stop Their Drops

Approximately half of patients who had filled a glaucoma prescription discontinued therapy within six months. Also, only 37% of patients refilled their initial medication at three years. These are the findings of a new study in October’s American Journal of Ophthalmology.

Am J Ophthalmol 2005 Oct;140(4):598-606.

Review of Optometry


DR. KEVIN'S COMMENTS: I guess we have to be more careful about assuring compliance

Saturday, December 17, 2005

Here I am with my wife and friends in Hawaii


We were ziplining in Kauai in July 2005. Awesome experience! What a great time!