A spectraldomain OCT study of formerly premature children

A spectral-domain OCT study of formerly premature children. Prat Itharat MD May 30, 2008 Vanderbilt Eye Institute Preceptor: Dr. Recchia

Background: Optical coherence tomography (OCT) Ø OCT analogous to ultrasound imaging Ø Non-invasive Ø Uses light waves Ø Many applications in ophthalmology

Background: OCT Zeiss Stratus OCT Domain ØTime Zeiss Cirrus HD-OCT Ø Zeiss Stratus OCT Spectral Domain (Meditec, Dublin, CA) Acquires 6 linear B-scans Acquires 200 linear Ø Acquires 6 B-scans linear BØ Acquires 200 linear Bscans Fewer data points sampled More data points sampled Ø Fewer data points Ø More data points sampled ØSlower Faster scanning time Ø Slower time Ø Better resolution: up to 5 Ø Resolution: up to 10 microns Better resolution: up to 5 microns Ø Less concern for eccentric Ø More concern for fixation technical More concernand for eccentric fixation Less concern for eccentric fixation and technical skills

Background: SD vs TD OCT Spectral Domain Time Domain Courtesy of Zeiss Whitepaper

Background: Prematurity

Background: Prematurity Ø Escedy et al (2007) noted increase central retinal thickness in formerly premature children Ø Stratus OCT Ø Mainly due to presence to ROP

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Recchia et al (2007) showed OCT abnormalities in ROP patients - first to suggest that changes may be vestiges of prematurity

Limitations Ø Technologically Ø Methodologically

Hypothesis: OCT abnormalities are more common in formerly premature children than in full term children.

OCT and prematurity Study questions: 1. Is there a difference in macular thickness between premature and full-term children? 2. Is there a difference in foveal contour between these groups? 3. Are the OCT findings correlated to the presence of ROP or another variable?

Methods Ø IRB approval for prospective study Ø Records of formerly premature infants born prior to 1/1/2001 (treated in the Vanderbilt NICU) Ø Control group matched for age and refractive error

Methods Ø Group I: premature with ROP (<32 weeks gestational age) Ø Group II: premature without ROP (<32 weeks gestational age) Ø Group III: full term (>36 weeks gestational age)

Methods Ø Gestational age, birth weight, ROP status obtained from records Ø Cycloplegic refraction Ø Best corrected visual acuity

Methods Ø Quantitative primary outcome measures (OCT) -central subfield thickness -inner (ring) macular thickness -outer (ring) macular thickness -total macular volume

Methods Ø Qualitative primary outcome measures (OCT) -presence of foveal depression -preservation of retinal layers

Methods Ø OCT data were reviewed by a trained physician (FMR) masked to the birth history of the patient Ø Quality of all scans was assessed any scans with a signal strength less than 8/10 were discarded Ø For each eye, a 6 x 6 mm macular cube and 5 -line macular raster line scan were interpreted individually

Results: Eyes 76 • 38 patients completed study -9 • One eye nystagmus, one eye phthisical, two eyes uncooperative, five monocular status -6 • Six eyes from three patients – could not determine ROP/non-ROP status -2 • From one pt with a poor OCT scan 59 • Eyes of 32 patients

Results:

Results: Central subfield thickness

Results: Inner ring retinal thickness

Results: Outer ring retinal thickness

Results: Total macular volume

Results: Foveal contour

Results: Central subfield thickness : inner ring thickness

Results: Gestational age effect?

Discussion: Ø Significant effect of gestational age Ø Non-significant effect of ROP Ø In contrast to prior studies which suggest that ROP is the major determinant of OCT abnormalities

Discussion: Foveal development Ø Ø Ø Foveal depression occurs by a reduction of inner (ganglion cell and inner nuclear) layers of the retina Evident by 24 -25 weeks of gestation Continues until four months postnatally Diagram from Provis et al.

Discussion: Foveal development Ø Mintz-Hittner et al described smaller foveal avascular zone (FAZ) in formerly premature children Ø Provis et al showed that the formation of the FAZ (vascular border) precedes foveal depression Ø These two processes may be interrelated

Discussion: Foveal development Ø Prematurity may change retinal oxygenation Ø Disruption of FAZ and foveal formation -Blunted/absent foveal depression -Thickened central macula -Preservation of retinal layers Ø Interestingly, most of our patients had excellent visual acuity

Limitations Ø Selection bias (less severe ROP, less severe neurological disease) Ø Non-matched gestational age Ø Most ROP staging obtained indirectly through NICU discharge summaries Ø Inter-rater variability of ROP

Conclusions Ø OCT findings such as increased central macular thickness and foveal depression blunting may represent hallmarks of prematurity Ø These findings can be associated with normal visual acuity

Clinical relevance Ø Greater use of OCT in evaluation of patients with decreased visual acuity Ø OCT abnormalities may not represent ocular disease Ø Research studies in which numerical cutoffs are made for inclusion or evaluation of therapeutic response

Acknowledgements Ø Dr. Franco Recchia Ø Tony Adkins Ø Dr. Jeffrey Kammer Ø Rocky Munn Ø Dr. Lori. Ann Kehler Ø Dr. Robert Estes Ø Dr. Cynthia Recchia Ø Dr. Ryan Tarantola Ø Dr. Chun Li Ø Christine Franklin Ø Dr. Jeffrey Sonsino Ø Ø Sandy Owings Family and children volunteers

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