In this retrospective, comparative analysis of 37 patients who developed corneal ectasia post-LASIK out of 148 patients included in the study, the researchers devised a scale with a grading system of the following corneal parameters: central keratometry; oblique cylinder; pachymetry; inferior and superior corneal diopteric power value; posterior surface elevation; and the ratio of posterior to anterior best sphere fit. Each parameter was given a grade of one to three each, and an ectasia grading system was established, with the cumulative risk score assessed.
Patients who had a grade of seven or less showed no evidence of corneal ectasia, whereas 16 (59 percent) of 27 patients who had a grade of eight to 12 had corneal ectasia. Twenty-one (100 percent) of 21 patients with a grade of more than 12 had corneal ectasia after LASIK (p<0.0001).
The researchers say that while this proposed grading system is helpful in the identification of patients who are at risk of developing corneal ectasia after LASIK, it doesn't replace a comprehensive eye examination.
(Ophthalmology 2006;113:1618-1622)
Tabbara KF, Kotb AA.
IOP Monitoring in Advanced Glaucoma
Patients in advanced stages of glaucoma or those with progression that is disproportionate to known intraocular pressure measurements can benefit from 24-hour IOP monitoring, say researchers in New York City. They say the 24-hour monitoring of IOP, outside of normal office hours, adds clinically useful information and may reveal a greater role for pressure-related risk for glaucoma progression than previously suspected and may alter treatment strategies.
The researchers reviewed the records of all patients with glaucoma who were admitted for 24-hour IOP monitoring during a span of three years. Applanation IOP was recorded in the sitting position from 7 a.m. until midnight and in the supine position at 6 a.m. Of the 32 patients (22 women, 10 men) who were enrolled (mean ±SD age, 67.3 ±12.1 years), mean ±SD 24-hour IOP was 13 ±2.2 mmHg. The mean ±SD peak 24-hour IOP (16.8 ±3.2 mmHg) was significantly higher than peak office IOP (14.7 ±3.2 mmHg) (p<0.001). Peak IOP was recorded outside of office hours in at least one eye in 22 patients (69 percent). Mean IOP fluctuation during 24-hour monitoring (6.9 ±2.9 mmHg) was significantly greater than that during office hours (3.8 ±2.3 mmHg, p<0.001). Peak 24-hour IOP was higher than the peak IOP noted during previous office visits in 40 eyes (62 percent).
The results of 24-hour IOP monitoring led to immediate treatment change in 23 eyes (36 percent), the researchers report. They advise that until accurate self-tonometry devices become widely available or a method for accurately predicting the 24-hour peak is found, clinicians should consider obtaining 24-IOP measurements for selected patients.
(Arch Ophthalmol. 2006;124:793-797)
Barkana Y, Anis S, Liebmann J, Tello C, Ritch R.
Omega-3s May Help Prevent AMD
Omega-3 fatty acids play some role in the primary prevention of age-related macular degeneration, according to researchers at the University of Ottawa Eye Institute and CHEO Research Institute in Ottawa. The researchers' systemic review of current world literature on the topic was requested and funded by the National Institutes of Health. The researchers say present literature neither clearly supports nor refutes this prevention.
Omega-3 fatty acids are considered potentially important antioxidants and are being considered as an arm of the Age-Related Eye Disease Study II clinical trial, according to the researchers. They report that there is some clinical evidence for protection against AMD from omega-3 fatty acids; however, the results were not consistent.
The researchers suggest further study is needed with regards to prospective cohort designs or randomized cohort trials targeting high-risk patients with the objective of preventing advanced dry AMD or neovascular AMD.
(Ophthalmology 2006;113:1165-1173)
Hodge WG, Schachter HM, Barnes D, Pan Y, Lowcock EC, Zhang L, Sampson M, Morrison A, Tran K, Miguelez M, Lewin G.
Blue-Light Filtering IOLs Offer Protective Effects
A blue-light filtering intraocular lens (Hoya) may be more protective against lipofuscin photoreactive damage and inhibit more light-induced VEGF production than a conventional ultraviolet-absorbing IOL (VA60BB, Hoya). That's according to researchers from the Department of Ophthalmology at the University of Tokyo School of Medicine in Japan and the Department of Chemistry, College of Science, at Yonsei University in Seoul, Korea.
They say the lipofuscin fluorophore A2E triggers apoptosis in retinal pigment epithelial cells after blue-light exposure, indicating that it mediates blue-light-induced RPE cell damage, and also causes light-induced phenotypic changes in those cells. This alteration in the RPE phenotype contributes to the production of proangiogenic factors from RPE cells that may affect the pathogenesis of exudative AMD.
Without an IOL, the white-light exposure decreased cell viability to 28 percent of the non-irradiated control. Although the UV-absorbing IOL tended to reduce light-induced cell death, the decrease was not significant. However, the presence of the blue-light filtering IOL significantly attenuated light-induced cell damage, increasing cell viability to 42 percent. The secreted VEGF protein level increased 3.2-fold after the A2E-laden RPE cells were exposed to white light. In the presence of the UV-absorbing IOL, the VEGF protein level decreased, but not significantly. The presence of the blue-light filtering IOL significantly attenuated the upregulated VEGF expression compared to upregulation without an IOL.
(J Cataract Refract Surg 2006;32: 1540-1544)
Yanagi Y, Inoue Y, Iriyama A, Jang W.
Complement Factor H Raises Risk for Atrophic AMD
Complement factor H is the first major AMD risk gene found so far, says a group of researchers from Vanderbilt University in Tennessee and Duke University in North Carolina. The researchers of the retrospective, case-control study say CFH increases the risk of developing geographic atrophy (grade four) as well as neovascular (grade five) and milder (grade three) disease.
The independent data set contained 647 AMD cases (grades three, four or five) and 163 controls (grades one or two). To determine if CFH had any effect on determining risk for development of GA, the rs1061170 single-nucleotide polymorphism was tested for association, separating grades and analyzing them independently against the controls. Odds ratios were calculated using standard logistic regression models. The outcome variable was AMD affection status, and genotypes were coded according to a log-additive model.
There were 407 grade five, 107 grade four, 133 grade three, 35 grade two and 128 grade one individuals. There was significant association with AMD when comparing grades three, four and five versus the controls. The highest odds ratio was obtained when analyzing the grade-four cases versus the grade-1 controls (OR=3.217, p<0.0001).
The results indicate that CFH increases the risk of developing GA (grade four) as well as neovascular (grade five) and milder (grade three) disease. Although neovascular disease is responsible for the majority of severe vision loss with AMD, GA is also a significant cause of vision loss, and is without effective treatment. Therefore, an attempt to clarify its pathogenesis is of the utmost importance.
The researchers suggest that their findings indicate it may be possible to develop better preventative therapies or treatments for GA given the common effect of CFH and the inflammatory pathways likely involved.
(Ophthalmology 2006;113:1504-1507)
Postel EA, Agarwal A, Caldwell J, Gallins P, Toth C, Schmidt S, Scott WK, Hauser MA, Haines JL, Pericak-Vance MA.
